Localized metasomatism of Grenvillian marble
leading to its melting, Autoroute 5
near Old Chelsea, Quebec
Fahimeh Sinaei-Esfahani
Department of Earth and Planetary Sciences
McGill University, Montreal
2013
A thesis submitted to the Faculty of Graduate Studies and Research
in partial fulfillment of the requirements
for the degree of Master of Science
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ABSTRACT
The recent (2009) opening of an extension of Autoroute 5 north of Old
Chelsea, Quebec, has produced striking road cuts over a length of 2 km, with a wide
variety of rock types and a very complex and bewildering juxtaposition of igneous,
metamorphic, and metasomatic assemblages of minerals.
The focus here is on the
mineralogy of the “regional” white marble; it is compared to calcite-dominant rocks,
orange, pink, yellow, and blue in color. The orange to pink calcite is dominant in
phenocryst-bearing dikes with a selvage of euhedral crystals of diopside. pargasite,
phlogopite, titanite and betafite are the dominant phenocrysts. The orange calcite in those
dikes [δ13C ≈ –1‰, δ18O ≈ 16‰] is isotopically intermediate between the regionally
developed white marble [δ13C ≈ 3‰, δ18O ≈ 24‰] and a typical mantle-derived
carbonatite [δ13C ≈ –5‰, δ18O ≈ 6‰]. The evidence points to the local metasomatism of
regional marble by an alkaline fluid of mixed crust + mantle derivation, then melted,
possibly at the end of the Ottawan orogenic phase, at approximately 1020 m.y., or the
Rigolet orogenic phase, at approximately 980 m.y. The orange pigment in the calcite is
possibly bastnäsite-(Ce) or hydroxylbastnäsite-(Ce), and the pink calcite may well be due
to exsolution-induced blebs of ferroan dolomite. Above the dikes are diffuse zones of
fracture-controlled reddening of the gray gneiss, in which the original mineralogy is
replaced by a K-feldspar-dominant “syenitic” material. There are signs of rheomorphism
of fenites developed at the expense of the gray gneiss. The road cut displays the products
of melting of marble in the crust, leading to a crustal silicocarbonatite. The phenomenon
is widespread but localized in the Central Metasedimentary Belt of the Grenville
Province.
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SOMMAIRE
La construction récente (2009) d’un nouveau tronçon de l’Autoroute 5 au nord de
Old Chelsea, Québec, a produit des coupes imposantes sur une longueur de plus de 2 km,
révélant ainsi une grande variété de types de roches et une juxtaposition surprenante
d’assemblages de minéraux ignés, métamorphiques, et métasomatiques. Cette thèse porte
surtout sur la minéralogie du marbre blanc “regional”, ainsi que d’échantillons de roches
carbonatées orange, rose, jaune, et bleu. Les roches à calcite orange ou rose se présentent
en filons avec phénocristaux, et ceux-ci ont un liseré de cristaux idiomorphes de diopside
le long de leur contact. La pargasite, la phlogopite, la titanite et la bétafite sont les
phénocristaux prédominants. La calcite orange dans ces filons [δ13C ≈ –1‰, δ18O ≈
16‰] est isotopiquement intermédiaire entre la calcite du marbre blanc “régional” [δ13C
≈ 3‰, δ18O ≈ 24‰] et la calcite typique d’une carbonatite mantellique [δ13C ≈ –5‰, δ18O
≈ 6‰]. D’après les données nouvelles, le marbre régional a aurait subi les effets d’une
métasomatose locale par une phase fluide alcaline de dérivation mixte (croûte +
manteau), et a aurait ensuite fondu, possiblement à la fin de la phase orogénique Ottawa,
à environ 1020 millions d’années, ou la phase orogénique Rigolet, à environ 980 millions
d’années. Le pigment orange dans la calcite est possiblement la bastnäsite-(Ce) ou
l’hydroxylbastnäsite-(Ce), et la couleur de la calcite rose pourrait bien être due aux microinclusions de dolomite ferrifère, attribuées à l’exsolution. Au contact supérieur des filons
de carbonate se trouvent des zones diffuses de transformation rougeâtre du gneiss gris,
distribuées le long de fractures. Ces zones transformées contiennent un matériau
“syénitique” à dominance de feldspath potassique, dû au rhéomorphisme des fénites
créées aux dépens du gneiss gris. Les affleurements démontrent les produits de la fusion
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du marbre dans la croûte, et donc la formation de silicocarbonatite crustale. Le
phénomène est répandu mais localisé dans la Ceinture Métasédimentaire Centrale de la
Province du Grenville.
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Acknowledgements
Foremost, I express my sincere gratitude to my supervisor, Robert F. Martin, for
his patience, motivation, enthusiasm, knowledge, advice, and support in preparing my
thesis. Since Bob accepted to be my supervisor, he always provided valuable insight. I
also thank Dr. Hojatollah Vali, who introduced me to my main advisor, and who
supported and assisted me during my thesis. In addition, I appreciate the advice and
support of Prof. Jeanne Paquette, especially during her course on Crystal Chemistry. I
thank Dr. William Minarik for his support in matters to do with ICP–MS and XRF
analyses. My sincere thanks also go to Jeffrey de Fourestier, who guided me in my thesis
area. Special thanks to Shi Lang, Line Mongeon, George Panagiotidis, and Kristyn
Rodzinyak for assistance with analyses. I appreciate the help of Anne Kosowski, Kristy
Thornton and Angela Di Ninno. I cannot forget my best friend, Pejman Nekoovaght, who
was always there for moral support and very practical assistance. I express my love and
gratitude to Vicki Loschiavo for all her kindness and support. Last but not least, I thank
my family, my parents, and my husband, Peyman Rajabian, for support throughout my
study.
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TABLE OF CONTENT
Abstract
Sommaire
Acknowledgements
List of figures
List of tables
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Chapter 1. Introduction
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Chapter 2. Previous work on the new road cut
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Chapter 3. The geological context of the Old Chelsea – Wakefield area
Observations in the Wakefield area
Observations in the Gatineau Park area
Observations in the Mont-Tremblant area
Observations in the Otter Lake area
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Chapter 4. Methodology
Cathodoluminescence imaging
ICP–MS analyses of bulk carbonate-dominant rocks (solution mode)
Electron-microprobe analyses
X-ray fluorescence
Scanning electron microscopy
Stable isotope analysis using mass spectrometry
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Chapter 5. The mineralogy and composition of calcite-dominant samples
and associated rocks
The carbonates
The regional marble
Composition of the regional marble
Orange calcite dike rock
Composition of the orange calcite
A possible cause of the orange coloration
Cathodoluminescence microscopy
Pink calcite dike rock
Composition of the pink calcite
Cathodoluminescence microscopy
Blue marble
Composition of blue marble
Cathodoluminescence microscopy
The composition of included minerals
Olivine
Pyroxene
Amphibole
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Phlogopite
The associated rocks
Chapter 6. Stable isotope composition of calcite and pyrrhotite in rock encountered
along the Chelsea road cut
The δ18O and δ 13C values of calcite
The 87Sr/86Sr value of calcite
The δ 34S value of pyrrhotite in pink calcite
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Chapter 7. Discussion
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Chapter 8. Conclusions and suggestions for future work
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References
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Appendix I. List of samples, their coordinates, and the type of analysis carried out
Appendix II.A. Pink marble: electron-microprobe data
Appendix II.B. Orange marble: electron-microprobe data
Appendix II.C. Blue marble: electron-microprobe data
Appendix II.D. White marble (regional): electron-microprobe data
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LIST OF FIGURES
Chapter 1
Fig. 1. 1. The extent of the Grenville province in eastern Canada
Fig. 1. 2. Google map showing the thesis area
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Chapter 2
Fig. 2. 1. Geological map of the area near the Chelsea road cut
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Chapter 3
Fig. 3.1. Geological map of the Chelsea – Wakefield area
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Chapter 5
Fig. 5.1. Regional marble with stratiform accumulation of dark minerals
Fig. 5.2. Representative view of regional marble along an Autoroute 5 road cut
Fig. 5.3. Regional marble with serpentine, sphalerite, forsterite
Fig. 5.4. Regional marble with pseudomorphic serpentine mineral
Fig. 5.5. Regional marble with scattered roundish grains of forsterite
Fig. 5.6. Chondrite-normalized REE plot of regional marble
Fig. 5.7. Orange calcite dike intruded in dark country rock
Fig. 5.8. Orange calcite dike intruded in the country rocks
Fig. 5.9. Orange calcite dike, with fragment of wallrock enclosed by calcite matrix
Fig. 5.10. Mechanical twins are ubiquitous in orange calcite
Fig. 5.11. Unusual intergrowth of diopside and pargasite in orange calcite
Fig. 5.12. Diopside included in orange calcite
Fig. 5.13. Diopside crystal in orange calcite
Fig. 5.14. Diopside with phlogopite inclusions surrounded by allanite
Fig. 5.15. Chondrite-normalized REE plot of orange and pink carbonate dike rocks
Fig. 5.16. Globules of orange calcite trapped in fluorapatite
Fig. 5.17. Plane-polarized light image of an orange globule of calcite trapped
in fluorapatite, Yates mine, Otter Lake, Quebec
Fig. 5.18. Oxycalciobetafite in orange calcite, southeastern ramp
Fig. 5.19. Cathodoluminescence image of orange calcite
Fig. 5.20. Pink calcite grading to orange-yellow calcite
Fig. 5.21. Pink calcite-dominant dike rock with coarse stout diopside
Fig. 5.22. Oriented dolomite rhombohedra formed by exsolution in pink calcite
Fig. 5.23. Inclusions in pink calcite
Fig. 5.24. Euhedral prisms of apatite, clouds of dolomite specks
Fig. 5.25. Phlogopite, serpentine and magnetite inclusions in pink calcite
Fig. 5.26. An anhedral grain of olivine is locally transformed to serpentine
Fig. 5.27. Apatite with complex zoning in pink calcite
Fig. 5.28. Anhedral apatite with inclusions of monazite and euhedral anhydrite
Fig. 5.29. Silicate containing Ca, Y, La and Ce, possibly caysichite-(Y)
Fig. 5.30. Cathodoluminescence image of pink calcite
Fig. 5.31. Massive blue marble
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Fig. 5.32. A representative image of blue marble in thin section
Fig. 5.33. Inclusion of euhedral diopside in blue marble
Fig. 5.34. Chondrite-normalized REE plot of blue marble
Fig. 5.35. The cathodoluminescence image of blue calcite
Fig. 5.36. Image of the regional marble containing olivine
Fig. 5.37. Slender prisms of diopside in pink calcite define a macrospherulitic texture
Fig. 5.38. Orange carbonate matrix next to gray gneiss
Fig. 5.39. Pink to gray carbonate dike crowded with pargasite crystals
Fig. 5.40. Two generations of amphibole are visible in pink-orange calcite
Fig. 5.41. Two generations of amphibole in pink-orange calcite
Fig. 5.42. Pink-orange calcite, showing pargasite and ferro-actinolite
Fig. 5.43. Coarse phenocrysts of phlogopite in orange-pink carbonate dike
Fig. 5.44. Titanite and rutile needles in phlogopite
Fig. 5.45. Optical study of a single flake of phlogopite
Fig. 5.46. Phlogopite is locally transformed to chlorite
Fig. 5.47. Concentration of titanite and REE carbonate between calcite and phlogopite
Fig. 5.48. Back-scattered electron image of phlogopite with titanite grains
Fig. 5.49. SEM image of phlogopite shows a primary grain of titanite inside phlogopite
and a secondary one along the cleavage
Fig. 5.50. SEM image of phlogopite with titanite inclusions of two types
Fig. 5.51. Association of carbonate body, gneiss and feldspathic rocks (fenite)
Fig. 5.52. Quartzofeldspathic rock with apatite, calcite, pyrite and albite included
in microcline
Fig. 5.53. Pink microcline-dominant fenite
Fig. 5.54. Sodic-plagioclase-dominant domain in fenite
Chapter 6
Fig. 6.1. Plot of isotopic values for samples of calcite from the Chelsea road cut,
Mont-Tremblant, Otter Lake, and the Adirondacks
Fig. 6.2. The carbon and oxygen isotopic composition of calcite in Trenton limestone
from the contact-metamorphic aureole of the mantle-derived Mont Royal pluton
Fig. 6.3. Variation in 87Sr/86Sr of seawater with time
Fig. 6.4. Pink to gray carbonate dike rock containing a large domain of pyrrhotite
Fig. 6.5. Range of δ 34S values in sulfides from mantle, oceanic and continental
igneous settings
Chapter 7
Fig. 7.1. Generalized diagram to show the principal chemical changes during
fenitization
Fig. 7.2. Pressure vs. temperature diagram illustrating decarbonation reactions
and melting curves
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LIST OF TABLES
Chapter 5
Table 5.1. Whole-rock composition of regional marble
Table 5.2. Trace-element concentrations in regional marble
Table 5.3. Average composition of orange calcite, Chelsea road cut, Quebec
Table 5.4. Whole-rock composition of orange and pink dike rocks
Table 5.5. Trace-element concentrations in orange and pink dike rocks
Table 5.6. Average composition of pink calcite
Table 5.7. Average composition of dolomite in pink calcite
Table 5.8. Average composition of blue calcite in samples of blue marble
Table 5.9. Whole-rock composition of blue marble
Table 5.10. Trace-element concentrations in blue marble
Table 5.11. Average composition of olivine grains in pink calcite
Table 5.12. Average composition of representative pyroxene
Table 5.13. Average composition of pargasitic amphibole
Table 5.14. Average composition of ferro-actinolite
Table 5.15. Average composition of phlogopite
Chapter 6
Table 6.1. Stable isotope composition of calcite grains
Table 6.2. Initial 87Sr/86Sr value of calcite of various colors
Table 6.3. Value of δ 34S of pyrrhotite in pink carbonate dike rock
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CHAPTER 1. INTRODUCTION
Rocks of the Grenville Province have been involved in what is arguably the
largest collisional orogen of the world. Repeated collision took place between the North
American craton and continental masses to the southeast, now concealed under the
Appalachian orogen. In Canada, the Grenville Province (Fig. 1.1) extends from the coast
of Labrador toward Lake Ontario; in the U.S., one can follow it diagonally across North
America and into Mexico (Oaxaca Province). The Grenville Province is characterized by
large variety of igneous and sedimentary rocks deformed and metamorphosed at various
times in the interval 1.4-1.0 Ga, generally at a high grade, up to the granulite facies. Such
a regionally developed granulite-grade terrane can be understood by considering a
modern collisional belt like the Himalayas. Rocks of Grenville age exposed at the surface
today in western Quebec and eastern Ontario are consistent with a depth of formation of
20 to 30 km or more. They result from isostatic uplift such that deep crust has now
reached the surface. Among the Grenville rocks of southwestern Quebec, white marble is
a prominent rock-type in what is known as the Central Metasedimentary Belt (Easton,
2000), associated with quartzofeldspathic gneiss, amphibolite and quartzite, undeformed
or weakly deformed granite and syenite, and ultramafic dikes.
At specific locations in southwestern Quebec, southeastern Ontario and
contiguous area of New York State, the regionally distributed white marble gives way to
assemblages of coarse-grained calcite-dominant rocks containing orange, pink, yellow,
blue, or gray calcite. These rocks contrast with the white to gray regionally developed
12
marble, which contains a minor amount of dolomite and graphite. Tiny crystals of
phlogopite, diopside, forsterite and actinolite of metamorphic origin are not uncommon.
The Autoroute 5 road cut north of Old Chelsea, Quebec, located 17 km northwest
of Ottawa, is such an area of juxtaposition of multicolored calcite, gray gneiss and white
marble. In this thesis, the focus is on the calcite-bearing assemblages. The following
questions have guided this research project. 1) What is the mineralogy of the regional
white marble and the multicolored calcite-bearing rocks? 2) What are the geochemical
and isotopic attributes of the calcite? 3) What petrogenetic information can be extracted
from these data?
In order to reach these goals, the new road cut, created in 2009 for an extension of
Autoroute 5 (which is parallel to the old Highway 105) heading north from Gatineau
(Hull) toward Maniwaki (Fig. 1.2) was visited on four occasions to collect samples of the
various rock types under the guidance of Mr. Jeffrey de Fourestier. In Chapter 2, two
reports written on the mineralogical oddities found along the road cut are summarized,
one of them written by Mr. de Fourestier. In addition, samples were collected from MontTremblant (formerly, Saint-Jovite), Quebec, 140 km to the northeast. Samples from Otter
Lake, Quebec, 76 km to the northwest, were contributed by Dr. Ralph Kretz in order to
compare marble samples in these regions with the marble samples along the road cut
investigated near Old Chelsea. Along what will be referred to for convenience as the
Chelsea road cut, about 55 samples were collected. At Mont-Tremblant, 15 samples were
collected; from Otter Lake, six samples were included in the study. For comparison, five
samples were included from the Adirondacks, and were provided by Dr. Marian
Lupulescu, New York State Museum in Albany. Chapter 3 provides, the geological
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context of the region covering western Quebec, eastern Ontario, and northern New York
State.
Various methods of analysis were applied. Optical microscopy was used for
preliminary identification of the rock-forming minerals. The electron microprobe is an
excellent tool with which to characterize these minerals and to identify unknown phases.
The bulk composition of key samples was established by X-ray fluorescence
spectroscopy, and inductively coupled mass spectrometry – mass spectrometry (ICP-MS,
solution mode) is a powerful tool of trace-element analysis. A cathodoluminescence
microscope was used for carbonate petrography and to qualitatively evaluate the
importance of Mn and selected rare earths. The isotopic composition of oxygen, carbon
and strontium of the calcite, and the sulfur isotopic composition of five samples of
pyrrhotite, were acquired by mass spectrometry. These data do provide insight into the
origin of carbonate rocks. Details of the analytical methods used are presented in
Chapter 4.
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Fig. 1.1. The extent of the Grenville Province in eastern Canada.
In the southwestern part of the belt, three major tectonic boundaries are shown: LDZ:
Labelle Deformation Zone, CCZ: Carthage–Colton Shear Zone, CMBBZ: Central
Metasedimentary Belt Boundary Zone. Pertinent to this study is Mo: Morin. The red star
marks the approximate location of the Chelsea road cut. The map is taken from McLelland
et al. (2010).
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Wakefield
Highway 105
Fig. 1.2. Google map showing the thesis area. The Autoroute de la
Gatineau (Autoroute 5) parallels Highway 105. The two red stars delimit
the interval of Autoroute 5 along which the road cuts of interest are located.
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CHAPTER 2. PREVIOUS WORK ON THE NEW ROAD CUT
The part of Autoroute 5 from Gatineau to Maniwaki that is of interest here is a
2.5-km-long segment in Addington Township, east of Gatineau Park, parallel to Highway
105 and to the Gatineau River. The section, under construction from 2007 to 2009,
actually goes from Exit 21 on Highway 5 (Tulip Valley Exit) in the Cascades district of
Chelsea, Quebec, north 2.5 km to a temporary exit in Farmer's Point district (Fourestier
2008). The new road cuts created by blasting provided a great opportunity for mineral
collecting, and two reports were soon prepared as accounts of what was found.
To Belley et al. (2010), the highlight was the discovery of subvertical veins of
“yellowish to gray and white” calcite up to 20 cm wide containing schorl crystals with
ilmenite. The calcite is said to fluoresce pinkish red when exposed to short-wave
ultraviolet radiation. Another set of calcite veins was found to contain euhedral crystals of
molybdenite, along with minor amphibole, titanite, pyrrhotite and mica. Narrow veins of
greenish calcite (the color attributed to disseminated inclusions of chlorite) contain
molybdenite, apatite, and dark green clinopyroxene crystals upto 3 cm across, lining the
contact with the host paragneissic rock. The association is attributed to “hydrothermal
fluids present in fissures in the host rock”. In the full report on the mindat.org site, P.M.
Belley expressed the opinion that the 2.5-km section is underlain by the Wakefield
batholith, composed of syenite and monzonite, and that the fluids have emanated from
that batholith. This opinion is reasonable, in light of the 1:1,000,000 geological map
covering the region (Fig. 2.1), where this batholith is shown to cover the entire strip along
the Gatineau River, as far north as Wakefield (Baer et al. 1977). The reality is somewhat
more complicated, as will be explained in the next chapter.
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Jeffrey de Fourestier, a serious collector from Aylmer, Quebec, and author of a
mineralogical glossary, also regularly visited the site during the construction project. In
an unpublished report (2008), he described a great variety of rock types, e.g., marble,
syenite, granitic rocks, granitic pegmatite (including graphic granite), gneiss, mica schist,
pyroxenite, along with dikes of aplite and carbonate. He mentioned over 50 minerals in
his report, mostly identified visually. He introduced the writer to the area, and acted as
“tour guide” on more than one occasion. A recent addition to his list of minerals is
metamict oxycalciobetafite, found in a dike of orange calcite and identified with the help
of Andrea Čobić, specialist in metamict accessory phases from Zagreb, Croatia (pers.
commun. to J. de Fourestier, 2012).
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Fig. 2.1. Geological map of the area near the Chelsea road cut. This is a portion of the
geological compilation map of Bilodeau & Sharma (2009) showing the extent of the
Wakefield batholith (purplish unit Hy-h). The dominant pale brown unit in the northern half
of the map represents gneissic rocks. The blue units in the southern half of the map represent
the Ordovician sedimentary cover, A star shows the approximate location of the thesis area.
The red dot north of the star marks the location of Wakefield.
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CHAPTER 3. THE GEOLOGICAL CONTEXT OF THE
OLD CHELSEA – WAKEFIELD AREA
OBSERVATIONS IN THE WAKEFIELD AREA
Saint-Pierre-de-Wakefield is located approximately 20 km northwest of Old
Chelsea. Over this distance, the dominant rock-type is unit Hy-h, syenite, with major
exposures concealed by Quaternary deposits [Fig. 2.1, adapted from Bilodeau & Sharma
(2009)]. Along the section parallel to the Gatineau River referred to earlier, Béland
(1955) mapped northeast-striking elongate strips of intercalated units M4 (paragneiss),
M13 (marble), and M3a (orthogneiss, migmatite), listed in order of areal importance (Fig.
3.1); all are cut by syenite and “innumerable pegmatites”. Thus the area is considerably
more complex than shown in Figure 2.1. About the syenite, Béland (1955) mentioned the
presence of “perthitic microcline with a little plagioclase, a nearly opaque amphibole of
the hastingsite group, hornblende, biotite, and a little interstitial quartz”. Thus it is clear
that the syenite is rather potassic, although Béland did not present chemical data. Titanite
is a common accessory phase.
The marble, of regional importance in the Central Metasedimentary Belt, typically
is gray to white and layered, but locally pink or brownish. Near the contact with
pegmatite dikes and syenite, the marble is said to be “impregnated” with greenish
diopside and yellow or green serpentine in granules or veins. Where incorporated in
syenite, the marble is reported to reveal brucite-rich layers. At the edge of bodies of
marble, Béland (1955) noted the presence of green “metamorphic pyroxenite”, in which
deposits of mica and apatite occur in the Wakefield area. The pyroxenite consists of
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“diopside or augite with tremolite, hornblende, and phlogopite, which minerals for a
network of large crystals with, in the interstices, calcite, apatite and rarely feldspars”.
Béland concluded that such rocks must have formed by the hydrothermal alteration of
marble. Rocks of amphibolitic character containing hornblende ± plagioclase also seem to
have formed by metasomatism of limestones located near granitic gneiss, in his opinion.
Béland was thus the first to attempt to explain the origin of the pyroxene- and amphibolebearing calcite-bearing rocks that are the main focus of this thesis.
The Stephen Cross quarry, located 6 km south of Wakefield and 5 km northeast of
the thesis area, was exploited for brucite in the early 1960s. It is surrounded by syenite
and monzonite of the Wakefield complex. The brucite nodules in this megaxenolith of
marble, up to 2 mm in diameter and with an “onion-peel” texture, formed at the expense
of periclase (Hogarth et al. 1972). Cartwright & Weaver (1993) studied the interactions
between syenite and marble exposed in this quarry. They did this by analyzing the carbon
and oxygen isotopes of marble and the oxygen isotopes of the enclosing syenite. The
mineral assemblages are consistent with metamorphism in the interval 715–815°C; the
latest recrystallization took place in the presence of an aqueous fluid, X(CO2) ≤ 0.03 for
the case of infiltration at 710°C and X(CO2) ≤ 0.15 for the case of infiltration at 815°C.
The calcite in the brucite marble ranges in δ18O from 8.9 to 24.3‰ (VSMOW standard),
and in δ13C from –3.2 to –0.1‰ (VPDB standard). There is no correlation between δ18O
and δ13C in the calcite, nor are these parameters correlated with distance from the marble–
syenite contact. The diopside in one sample of brucite marble (δ18O = 18.4‰ in calcite)
has δ18O = 15.2‰. The forsterite in another sample of brucite marble (δ18O = 12.2‰ in
calcite) has δ18O = 9.2‰, whereas in two other samples (δ18O = 22.5, 24.3‰ in calcite),
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the forsterite has δ18O values of 19.5 and 20.8‰. The Wakefield syenite has whole-rock
δ18O values in the range 8.8–10.2‰, whereas calcite present in veinlets in the syenite
ranges from 9.7 to 11.4‰ (δ13C in the range 0.0 to –0.5‰).
OBSERVATIONS IN THE GATINEAU PARK AREA
The geology of Gatineau Park has been a career-long focus of interest of Prof.
Donald Hogarth. He has systematically mapped the geology of the area to the south and
southeast of the thesis area, and has published his findings as a 1:18 000 map (Hogarth
1970). The predominant rock mapped north and south of Meech Lake is syenite of the
Wakefield complex (unit 7a), commonly with a poorly developed foliation. Unlike
exposures in Béland’s map-area, further north, Hogarth documented a pluton of potassic
aplite 1.5 km across (unit 10), intrusive in the syenite and associated with a dike swarm of
intrusive carbonate, mainly dolomitic (unit 11), and fenite near McCloskey’s Field. To
the southeast, near Old Chelsea, the dominant rocks are north-trending lenses of
paragneiss (unit 3), minor quartzite (unit 4), marble (unit 5), and pyroxene-, amphiboleand phlogopite-bearing calc-silicate rock (unit 6), the latter generally in contact with
marble, and equivalent to rocks interpreted as metasomatized marble by Béland. Hogarth
(2000) agreed with Béland that the rock is a product of regional metamorphism, formed at
the expense of a siliceous dolomite protolith. Hogarth & van Breemen (1996) reported a
U–Pb age of 1026 ± 2 Ma on monazite from carbonatite and related fenite at Lac à la
Perdrix 12 km west of the thesis area. Marcantonio (1986) determined a Sm–Nd wholerock age of 1028 ± 24 Ma for dolomite carbonatite at Meech Lake, 7 km southwest of the
22
thesis area. These dates correspond to the Rigolet stage of evolution of the Grenville
collisional orogen, at which time gravitational collapse and delamination were already
underway, and new asthenosphere was rising diapirically (McLelland et al. 2010, Fig. 5).
Unfortunately, no one seems to have dated the Wakefield complex.
By analogy with potassic syenite emplaced elsewhere in the Central
Metasedimentary Belt, Cartwright & Weaver (1993) inferred that the age of emplacement
of the Wakefield syenite corresponds with the Ottawan pulse of deformation, roughly at
1070 Ma. In their view, the formation of the syenite was contemporaneous with regional
deformation. This opinion is considered incorrect, because syenitic magmas are
associated with distension in the crust, not compressional forces and thrusting (Emslie
1978). The Wakefield syenite complex, as a typical felsic member of an AMCG suite,
likely was emplaced after the second episode of delamination has begun in the area, i.e.,
after 1090 Ma according to Corrigan & Hanmer (1997) or at approximately 1050 Ma in
the reconstruction of McLelland et al. (2010, Fig. 5), at the extensional stage of the
Ottawan orogenic phase (Rivers 2008). One should not rule out the possibility, however,
that its emplacement was coeval with the first episode of delamination, which led to the
emplacement of anorthosite in the Morin massif located approximately 130 km east–
northeast of the thesis area over the interval 1160–1150 Ma, at the end of the Shawinigan
orogeny (McLelland et al. 2010).
23
OBSERVATIONS IN THE MONT-TREMBLANT AREA
Dr. William Peck, working in the Mont-Tremblant (formerly Saint-Jovite) area,
140 km northeast of Old Chelsea, Quebec, described calc-silicate rocks formed at the
contact of the Morin anorthosite, syenite, and monzodiorite with marble. He estimated the
peak temperature to be 751 ± 50°C based on calcite–graphite thermometry, and the peak
pressure estimated to be around 7-8 kbar on the basis of garnet–plagioclase barometry
(Peck et al., 2005). He considered that the Morin terrane was metamorphosed during the
Ottawan orogenic phase of the Grenville orogeny at 1070 Ma, at a similar time as
happened in the Adirondack Highlands in the southern part of Grenville Province (e.g.,
McLelland et al. 1996).
OBSERVATIONS IN THE OTTER LAKE AREA
The area of Otter Lake, located 76 km northwest of Old Chelsea, has been
systematically mapped by Prof. Ralph Kretz. Kretz & Garrett (1980) recognized two
groups of carbonate rocks, which they labeled major (i.e., regionally developed) and
minor (locally metasomatized) marbles. Major marbles are associated with plagioclasedominant gneiss and amphibolite with calcite, graphite, dolomite, calcic amphibole, calcic
pyroxene, forsterite and humite-group minerals. In minor marble, they described pink
calcite, phlogopite, calcic amphibole, calcic pyroxene, K-feldspar, scapolite and titanite.
Major marble in contact with granite and syenite becomes locally modified to minor
marble free of dolomite and graphite, and it becomes enriched in Sr and Mn. The
minimum peak temperature of metamorphism was estimated on the basis of exsolution of
dolomite from calcite to be 660°C. The pressure of metamorphism was calculated to be
24
roughly 7 kbar on the basis of the equilibrium of anorthite with grossular + sillimanite +
quartz (Kretz & Garrett 1980). The samples of major marble partially preserved the
oxygen and carbon isotopic values of the precursor limestone, δ18O (VSMOW standard)
in the range of 28–17‰ and δ13C (VPDB standard) in the range +6 to –2‰, whereas
typical values in the minor marble are δ18O = 14.5‰ and δ13C = 0.23‰. Kretz (2001)
concluded that isotopic shift of the minor marble is due to devolatilization and
metasomatism of major marble. He documented that a syenite body next to graphitebearing marble converts it to pink graphite-free marble (Kretz 2001). An outstanding
characteristic of syenite and granite at Otter Lake area is the great variability in mineral
proportions and striking contrasts between patches in the “blotchy” rocks (Kretz 2009).
Some of the felsic rocks have achieved their present compositions by metasomatic
transformations, which are judged to have occurred at high-temperature subsolidus
conditions.
25
Wakefield
Fig. 3.1. Geological map of the Chelsea–Wakefield area. The geological map of the
Gatineau Park (south part) (Hogarth, 1970) was overlain on the geological map of
Wakefield (Béland, 1954). In this map, the important units are as follows: light
brown (12D) is syenite of the Wakefield complex, dark coral (M3a): orthogneiss, pale
cream (M4): paragneiss, blue (M13): marble. Note that the dark brown unit (7) in the
southern map is also syenite of the Wakefield complex, and the blood red unit (10) is
potassic aplite and related pegmatite. The red star marks the approximate location of
the Chelsea road cut. Scale of the map: 1:50,000.
26
CHAPTER 4. METHODOLOGY
This thesis is based mostly on specimens taken along the Chelsea road cut. There
were four visits to the road cut. From these samples, mostly of marble and the calcitedominant dikes, but also syenitic dikes, graphic granite, and the host rocks, 48 polished
thin sections were prepared. They were studied with a petrographic microscope and by
the techniques listed below.
CATHODOLUMINESCENCE IMAGING
Luminescence in calcite is due to the presence of specific trace elements and the
ensuing distortion of the structure owing to defects affecting the crystal field (Machel,
1985). Cathodoluminescence (CL) analysis of calcite in grain mounts was performed
using a Reliotron R III cold-cathode unit mounted on a Leitz petrographic microscope
stage. Beam voltages ranged from 4.2 to 4.7 kV at 0.5 mA current and 60–70 Mtorr
operating pressure. A QImagingR Retiga EXi camera oriented vertically down the
microscope objective provided digital color images at a spatial resolution of 6.45 μm. The
photos were acquired with the QC capture software, with 15–65 s exposure times. There
was no color adjustment of the images.
27
ICP-MS ANALYSES OF BULK CARBONATE-DOMINANT ROCKS
(SOLUTION MODE)
Inductively coupled plasma – mass spectrometry (ICP–MS) is a powerful
technique for the quantification of elemental concentrations. Sixteen samples were
selected for a mild leach, in the hope of evaluating the relative levels of the REE, Ba, and
Sr in the calcite rather than in calcite + assorted silicates and oxide minerals present in the
whole rock. Among these were five samples of colored calcite-dominant rocks from the
Chelsea road cut (orange, blue, pink, yellow), one sky blue marble from the Adirondacks
in New York, six samples of minor marble from Otter Lake, and four samples from
Mont-Tremblant. All samples were hand-picked and cleaned to minimize the presence of
non-calcite minerals. Then they were crushed and ground to make a homogeneous
powder, and finally they were digested in nitric acid for ICP–MS analysis. The digestion
of calcite was done as follows: 7.5 mL of 1 M acetic acid [57 mL of glacial (99%) acetic
acid diluted to 1000 mL] was reacted with 100 mg of sample. The supernatant solution
was pipetted into teflon vials. Water was added to the sample tube (~ 500 µL), and
evaporated to dryness. Then 0.5 mL of 2% nitric acid was added, and the solution was
evaporated to dryness, then dissolved in 10 mL of 1% nitric acid. The preparation of
samples was done by Isabelle Richer under the supervision of Dr . William Minarik at the
Department of Earth and Planetary Sciences, McGill University. As the reader will see in
Chapter 5, this dissolution procedure gave very high concentrations of Ba and Sr, which
are not recorded in electron-microprobe analyses of the calcite. One can conclude that the
procedure, even with a dilute acid, led to the efficient dissolution of barite, strontianite
and celestine micro-inclusions that are widely disseminated in the calcite.
28
ELECTRON-MICROPROBE ANALYSES
The compositions of the major minerals were acquired with a JXA JEOL 8900L
electron microprobe, with analytical spots chosen using back-scattered electron images,
by Shi Lang. For the carbonates, conditions were 15 kV and 20 nA, with a beam size 5
μm in diameter. Count times for major elements (Mn, Mg, Ca, Fe, Ni, Sr) were 20 s.
Standardization was performed on dolomite for Mg, siderite for Mn and Fe, calcite for
Ca, NiO for Ni, and strontianite for Sr (Kα lines in each case). For the analysis of olivine,
pyroxene, amphibole and phlogopite, the conditions were 15 kV and 20 nA, with a beam
size 5 μm in diameter. Counts were collected on K, Na, Fe, Si, Mg, Ca, Ti, Mn, Al, Cr,
Ba, S and Cl peaks for 20 s, and in the case of F, for 50 s. Standardization was performed
on albite for Na, on fluorite for F, on vanadinite for Cl, on orthoclase for K, on hematite
for Fe, on olivine or diopside for Si and Mg, on diopside for Ca, on rutile for Ti, on
spessartine for Mn, on orthoclase for Al, on chromite for Cr, and on barite for S and Ba.
X-RAY FLUORESCENCE
A Philips PW2440 4 kW X-ray fluorescence spectrometer at McGill was used to
acquire concentrations of the major (Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P) and trace
elements (Ba, Ce, Co, Cr, Cu, Ni, V, Zn) of calcite-dominant rocks from the Chelsea road
cut (five samples), Mont-Tremblant (four samples), Otter Lake (six samples) and from the
Adirondack area in New York (one sample). Analyses were done on fused beads prepared
from ignited samples by Dr. Bill Minarik; detection limits were based on three times the
background values.
29
SCANNING ELECTRON MICROSCOPY
A JEOL JSM-840a scanning electron microsope (SEM) with EDAX energydispersion spectrometry was used to characterize the composition of micro-inclusions in
flakes of phlogopite. The tungsten-filament microscope was used for imaging and
chemical micro-analysis. It is equipped with a secondary-electron detector, a solid-state
back-scattered electron detector and an energy-dispersion system. Mrs. Line Mongeon
was the analyst.
STABLE ISOTOPE ANALYSIS USING MASS SPECTROMETRY
Data on δ13C (PDB) and δ18O (PDB) in calcite were acquired at the University of
Barcelona with a MAT-252 mass spectrometer. The extraction of CO2 was done in a
Carbonate Kiel Device III, by Thermo Finnigan, which reproduces in an automated way
the McCrea (1950) method. Carbonate is attacked with 100% phosphoric acid at 70°C.
The reaction time is three minutes (calcite). The Carbonate Device is coupled to MAT252 isotope ratio mass spectrometer produced by a Thermo Finnigan, in which the CO2
produced is analyzed. In order to evaluate the quality of the results, the NBS-19
international standard was used, with δ13C (PDB) = +1.95‰ and δ18O (PDB) = –2.20‰
values, certified by the IAEA. The standard deviation for the method used was 0.02‰ for
δ13C and 0.03‰ for δ18O. The standard NBS-19, which is calcite from a marble
(carbonate of marine origin), and also NBS-18, which is calcite from a carbonatite, were
used. The analyses were carried out by Mr. Joaquin Perona, of the University of
Barcelona. The results were transformed as follows: δ18O VSMOW = 1.03091* δ18O VPDB +
30.91 (Coplen, 1988).
30
Sulfur isotope analyses of pyrrhotite were carried out using a Thermo Finnigan
MAT 253 by Kristyn Rodzinyak in the isotope laboratory of the Department of Earth and
Planetary Sciences at McGill University, under the supervision of Prof. Boswell Wing.
The extraction involves a reaction with a chromium reduction solution (CRS), as
documented by Fossing & Jørgensen (1989).
31
CHAPTER 5. THE MINERALOGY AND COMPOSITION
OF CALCITE-DOMINANT SAMPLES
AND ASSOCIATED ROCKS
In this chapter, representative samples of marble, intrusive calcite-dominant rocks,
and the enclosing silicate rocks are described. The first section focuses on what is known
about the regional marble of the Grenville Province in terms of mineralogy and
composition. Then the calcite-dominant samples of various colors along the Chelsea road
cut are described.
The regional marble has a generally white to gray color throughout the Central
Metasedimentary Belt. Along the Chelsea road cut, the typical white-gray marble gives
way to a variety of calcite-rich rocks with colors such as pink, orange, green, blue and
yellow. Along the road cut, the so-called "regional" marble is less common than these
colored carbonate rocks. These are not unique to the Chelsea road cut; they are locally
developed in other parts of the Central Metasedimentary Belt. White and blue marble are
massive in outcrop, and thus similar to the regional marble of Grenville Province,
whereas orange and pink marble are emplaced in dike structures with unusually coarse
euhedral crystals of silicates, apatite and other minerals. For convenience, these orange to
pink calcite-dominant rocks will be referred to as carbonate dike rocks.
The dominant silicates present are forsterite, diopside, pargasite, and phlogopite,
which are present in both regional marble and the carbonate dikes. For purposes of
comparison between the Chelsea road cut carbonate rocks with analogues from nearby
localities in the Central Metasedimentary Belt, some samples of regional marble and
orange carbonate dikes also were analyzed from the Mont-Tremblant area, to the east of
32
Old Chelsea, a few samples of Grenville marble in New York State to the south, and
some from Otter Lake, to the northwest of Old Chelsea. By the end of this chapter, the
reader will have an idea about how the variegated samples of dike rocks differ from the
regional marble.
THE CARBONATES
This section contains a description of the regional marble, the orange and pink
carbonate dikes and the blue marble.
THE REGIONAL MARBLE
Most of the regional marble is fine to medium grained, white to gray in color, with
banding containing calcite, graphite, locally dolomite and siliceous clots (Fig. 5.1).
Graphite in this rock is usually interpreted to represent the remains of organic matter in
the original Mesoproterozoic limestone (Fig. 5.2). The regional marble contains
millimetric nodules of pseudomorphic brucite after periclase and of a serpentine-group
mineral pseudomorphic after forsterite. Also present are grains of almost completely
opaque sphalerite molded around the brucite nodules (Fig. 5.3). Minerals commonly
found in the regional marble include forsterite, diopside, actinolite and valleriite in small
roundish grains, all assigned a prograde metamorphic origin, whereas talc, chlorite,
serpentine and brucite are retrograde phases that signal the late influx of H2O. The
inference made by metamorphic petrologists working in the area (e.g., Cartwright &
Weaver, 1993) is that periclase is a product of decarbonation of primary dolomite. The
33
gas phase was initially CO2-dominant; later, the periclase became unstable as the fluid
phase became H2O-dominant (Fig. 5.4) the relevant metamorphic reactions are:
CaMg(CO3)2 = CaCO3 + MgO + CO2
Dolomite
Calcite
Periclase
MgO + H2O = Mg(OH)2
Periclase
Brucite
The first reaction effectively removed all dolomite from the rocks at a temperature above
900°C in a CO2-dominant ambient fluid phase, according to Cartwright & Weaver
(1993). The second reaction removed all the periclase, as no relic was found in any
sample. That reaction occurred at a temperature slightly above 700°C. The two reactions,
numbered 4 and 3, respectively, were plotted in a P–T diagram by Cartwright & Weaver
(1993).
34
Fig. 5.1. Regional marble with stratiform accumulation of dark minerals,
such as forsterite, diopside and graphite, Chelsea road cut, Quebec.
Fig. 5.2. Representative view of regional marble along an Autoroute 5 road
cut.
35
valleriite
Cal
Srp
Fo
Sp
Py
Fo
Srp
Srp
Cal
Fo
Fig. 5.3. Regional marble with serpentine, sphalerite, forsterite, pyrite and
valleriite in sample FAH132. The sphalerite is molded around the grains of
forsterite + serpentine. The texture, taken at face value, seems to show that the
sulfide was molten at peak conditions of P and T. Valleriite [ideal formula is
4(Fe,Cu)S•3(Mg,Al)(OH)2] surrounds serpentine grains. Back-scattered
electron image acquired with an electron microprobe.
Fo
Cal
Cal
Srp
Cal
Fig. 5.4. Regional marble with pseudomorphic serpentine mineral; sample
FAH143. Note: the presence of a thin film of a serpentine-group mineral
around forsterite grains included in calcite. Photomicrograph, cross-polarized
light, width of field of view 5 mm.
36
Fo
Fo
Srp
Py
Cal
Fig. 5.5. Regional marble with scattered roundish grains of forsterite and
pseudomorphic serpentine, sample FAH143. Photomicrograph, crosspolarized light, width of field of view 5 mm.
Composition of the regional marble
The calcite in the regional white marble along the road cut near Chelsea is
characterized by a high purity. It contains low concentrations of Mn (0.01 wt. % MnO),
Fe (0.02% FeO), Sr (0.06% SrO) and Mg (0.23% MgO); these average data were
acquired
by
electron-microprobe
analysis
of
two
samples.
In
comparison,
unmetamorphosed Paleozoic limestone in the general area contains 0.02 wt.% MnO,
0.12% FeO, 0.04% SrO and 1.27% MgO (Shaw et al., 1963). There are no significant
differences between calcite in the limestone and calcite in the Old Chelsea marble. The
lower amount of Mg in the Grenville calcite is consistent with the formation of periclase
and Mg silicates at the expense of dolomite as metamorphism progressed.
37
Four whole-rock samples of regional marble from the Mont-Tremblant area and
six samples of regional marble from Otter Lake, Quebec, were also analyzed (Table 5.1).
Sample SJ4 from Mont-Tremblant contains 0.04 wt.% MnO, 2.02% FeO and 2.04%
MgO. The higher Fe and Mg contents of regional marble at this locality likely reflects the
variability in non-carbonate constituents. The Otter Lake marble is compositionally
similar to the Chelsea road cut regional marble, but also with higher Mg (up to 4.12 wt.%
MgO) reflecting the presence of dolomite. In terms of trace elements, these two samples
do not show any significant differences (Tables 5.1, 5.2).
38
TABLE 5.1. WHOLE-ROCK COMPOSITION OF REGIONAL MARBLE:
REPRESENTATIVE SAMPLES FROM MONT-TREMBLANT AND OTTER LAKE
Sample
SJ4
C50
SiO2 wt.%
TiO2
Al2O3
FeO
MnO
MgO
CaO
Na2O
K2O
P2O5
18.24
0.26
3.25
2.02
0.04
2.04
40.57
0.67
0.46
0.07
5.52
0.05
0.78
0.42
0.03
4.12
48.23
0.06
0.18
0.04
Detection
Limits
ppm
60
25
120
25
25
95
15
35
25
35
BaO ppm
Ce
Co
Cr2O3
Cu
Ni
Sc
V
Zn
LOI wt.%
Total
SJ4
C50
92
61
13
27
32
7
<d.l.
33
<d.l.
29.82
97.47
95
30
9
7
19
<d.l.
<d.l.
13
<d.l.
39.40
98.84
Detection
Limits
ppm
12
15
10
10
2
3
7
7
2
Note: The data were acquired by the XRF technique. SJ: Mont-Tremblant regional marble,
C50: Otter Lake regional calcite–dolomite marble. <d.l.: below detection limit;
TABLE 5.2. TRACE-ELEMENT CONCENTRATIONS IN
REGIONAL MARBLE: REPRESENTATIVE SAMPLES FROM
MONT-TREMBLANT AND OTTER LAKE, QUEBEC
Sr ppm
Y
Ba
La
Ce
Pr
Nd
Sm
Eu
SJ4
C50
1308
10.06
1182
3.71
6.55
0.74
2.88
0.67
0.13
487
4.85
11516
2.69
3.76
0.60
2.58
0.54
0.12
SJ4
Gd ppm
Tb
Dy
Ho
Er
Tm
Yb
Lu
Th
U
0.98
0.17
1.19
0.28
0.90
0.13
1.00
0.16
0.06
0.02
C50
0.71
0.10
0.66
0.14
0.42
0.06
0.42
0.06
0.03
0.01
Note: The results are expressed as ppm (μg/g).
Analyses done on weak acid leaches, using ICP-MS (solution mode);
Detection limits (3x background s.d.), 0.005 ppm for the REE, Th, U.
39
A chondrite-normalized REE plot of the two samples of regional marble is presented in
Figure 5.6. It is obvious that the carbonate fraction of the regional marble is poor in both
light and heavy REE. Both samples have a negative anomaly in Eu. Hereafter, only the
representative sample of regional marble collected at Mont-Tremblant (SJ4) will be used
as a standard sample with which to compare the composition of marble samples
investigated in this study. Any sample of regional marble along the Chelsea road cut was
judged not to be totally devoid of a metasomatic overprint, which explains the reliance on
samples taken further afield.
Fig. 5.6. Chondrite-normalized REE plot of regional marble samples
taken from Mont-Tremblant and Otter Lake. Note: REE
concentrations in chondrite are those of Boynton (1984). SJ4:
regional marble from Mont-Tremblant, Quebec; C50: regional
marble from Otter Lake, Quebec.
40
ORANGE CALCITE DIKE ROCK
Orange is a prominent color of calcite along the road cut. It locally grades into
pink and yellow variants. It forms dikes that cut the host rock, mostly gneiss, syenite and
pyroxenites. These dikes are mainly composed of orange calcite that encloses coarse
crystals of phlogopite, apatite, diopside, pargasite, titanite and a pyrochlore-group mineral
"floating" in the calcite. The textural evidence indicates that these minerals are
phenocrysts. Calcite grains range from a few millimeters to 2 cm, and are slightly
deformed. The sizes of the enclosed minerals are: phlogopite 3 cm, apatite 4-5 cm,
diopside 3-4 cm, and titanite 2 cm. At the contact between the dikes of orange calcite and
the wallrocks, there typically is a selvedge containing an accumulation of diopside and
accessory amphibole. These crystals have nucleated at the contact and grown into
carbonate rock, invariably with euhedral faces (Fig. 5.7). The orange calcite rocks are
closely associated with pyroxenite (Fig. 5.8) Pieces of the wallrock surrounded by orange
calcite give the impression in the field that the carbonate was molten at the time of
emplacement (Fig. 5.9)
The orange calcite dike rock is mostly quartz-free, but at one location, it was
found to contain xenocrysts of corroded quartz next to albite and microcline grains. In
thin section, the calcite commonly shows twin bands caused by mild deformation (Fig.
5.10). Calcite is dominant (i.e., >50 vol.%) in the dikes. It is granular and anhedral; the
grains are larger in size than what is typical in the regional marble. The dikes contain
abundant grains of clinopyroxene, amphibole and phlogopite, locally altered to chlorite.
Amphibole and pyroxene form a very unusual intergrowth. The amphibole defines
41
domains of highly irregular shape inside the diopside (Fig. 5.11). The amphibole is
slightly zoned at its margin, and grew around domains of diopside. The orange marble is
brucite-free. This calcite is quite turbid and not as transparent as that found in regional
marble. In back-scattered electron images, inclusions of allanite and apatite were
identified. Allanite has two modes of occurrence in the orange dikes. Euhedral needles of
allanite radiate from the rim of the mafic clots toward the interior, and some nucleated
hydrothermally later, at grain boundaries, in open space between grains (Fig. 5.12).
There, it is surrounded calcite and apatite grains (Figs. 5.13, 5.14).
It is possible to propose a working hypothesis at this point to explain the textural
relationships exhibited in Figures 5.11 and 5.12. Figure 5.11 seems to show that the
domain occupied by diopside and pargasite was at one stage a domain of immiscible
mafic melt from which allanite, then diopside nucleated early; The needles of allanite
nucleated at the rim of the molten mafic domains and grew inward into the mafic melt,
which later produced diopside (Fig. 5.12) The pargasite then nucleated on the diopside
and seems to have been close to the residual mafic melt in composition. The rim of the
pargasite domains is slightly more Mg-rich than the bulk of the amphibole. The
hypothesis will need to be tested in future studies with more detailed characterization of
the minerals involved. As an example of such a test, one could evaluate the Mg and Fe
content of the first-formed solid and the phase now representing the former liquid, here
amphibole. The relationship of Roeder & Emslie (1970) should hold if the assemblage
represents a liquid + solid pair: KD = (XSFeO / XLFeO * XLMgO / XSMgO) ≈ 0.30.
The preliminary data reported in the caption to Figure 5.11 are consistent with the
hypothesis.
42
Di
Fig. 5.7. Orange calcite dike intruded in dark country rock. Euhedral crystals
of diopside have nucleated at the contact and grown into the carbonate rock.
Fig. 5.8. Orange calcite dike intruded in the country rocks; veinlets of gray
calcite (black arrow) cut the orange calcite. Note the selvedge of diopside
crystals along the upper contact or the orange dike. Southern extremity of
road cut, eastern ramp. A $2 coin is shown for scale.
43
Fig. 5.9. Orange calcite dike, with fragment of wallrock enclosed by calcite
matrix. Crystals of diopside and pargasite grow at its contact into the
carbonate.
.
Fig. 5.10. Mechanical twins are ubiquitous in orange calcite. Deformation of
the twin lamellae is visible locally, but in general it is not prominent. Width
of field of view 5 mm..
44
Prg
Ttn
Di
Chl
Phl
Fig. 5.11. Unusual intergrowth of diopside and pargasite in orange calcite.
Sample FS1. Prg Mg#: 0.75, Di Mg#: 0.94. Back-scattered electron image,
acquired with an electron microprobe.
Chl
Ttn
Di
Aln
Chl
Cal
Fig. 5.12. Diopside included in orange calcite. Allanite rods are oriented
more or less perpendicular to the edge of the domain of diopside. Coarse
intergranular allanite (irregular shape) shows patchy zoning; chlorite
forms a dark network around the allanite. Titanite grains are disseminated in
the diopside crystals. Sample FS1. Back-scattered electron image, acquired
with an electron microprobe.
45
Phl
Cal
Zrn
Di
Aln
Di
Cc
Ttn
Phl
Di
Fig. 5.13. Diopside crystal in orange calcite with titanite, allanite,
phlogopite and zircon inclusions. Zircon is associated with allanite, titanite
with phlogopite, partly converted to chlorite, Chelsea road cut. Sample FS1.
Back-scattered electron image, acquired with an electron microprobe.
Cal
Cal
Ap
Aln
Phl
Di
Ap
Ap
Fig. 5.14. Diopside with phlogopite inclusions surrounded by allanite. Apatite
also nucleated in intergranular sites. Allanite shows zoning from edge to
interior, Chelsea road cut. Sample FS1. Back-scattered electron image,
acquired with an electron microprobe.
46
Composition of the orange calcite
The results of major-element analyses of various samples of orange calcite are
presented in Table 5.3. The samples have quite similar compositions in terms of major
elements. Sample FS1 was used as the standard orange calcite rock; it comes from largest
mass of orange calcite along the Chelsea road cut, at the north end, west side. The calcite
in sample FS1 contains, on average, 0.09 wt.% MnO, 0.2% FeO, 0.78% MgO and 0.27%
SrO. These values are all slightly higher than those in calcite of the regional marble. The
results of an X-ray fluorescence (XRF) analysis (Table 5.4) of the orange calcite dike
rock (FS1) indicate a high Ce content (336 ppm) in comparison with the regional marble
(61 ppm). The REE pattern for orange calcite samples (Fig. 5.15) shows that the
enrichment involves not only Ce, but both light and heavy REE, with a negative Eu
anomaly. Interestingly, orange calcite dike SJ6 from Mont-Tremblant shows a very
similar trend of enrichment of the REE. Further studies of the trace-element signature of
orange and pink calcite are planned.
A possible cause of the orange coloration
There are various factors that can cause coloration in minerals, such as trace-level
incorporation of specific elements, radiation damage, and lattice defects in the structure.
As made clear above, the orange calcite is riddled with micro-inclusions (and probably
nano-inclusions as well). In order to address the question of the origin of the orange color,
a piece of more transparent calcite is needed than what is found along the Chelsea road
cut. A "globule" of transparent dark orange calcite from the Yates mine at Otter Lake,
47
Quebec, trapped in fluorapatite and interpreted to be a melt inclusion (Fig. 5.16) was sent
to Professor George R. Rossman at California Institute of Technology, expert in
spectroscopic properties and the color of minerals. He provided the image reproduced
here, of a polished section showing that the calcite is in fact colorless in plane light. An
orange pigment is concentrated along cleavage planes (Fig. 5.17). Based on ICP–MS
chemical results and enrichment of orange marble in the light REE, it seems quite
possible
that the orange phase that nucleated along the cleavage is bastnäsite-(Ce)
[(Ce,La)CO3F] or hydroxylbastnäsite-(Ce)
[(Ce,La)CO3OH], possibly of exsolution
origin, because the globule was completely enclosed in the fluorapatite crystal. Efforts to
identify the pigment were not successful.
As a working hypothesis to explain the above observation, it is possible that the
calcite crystallized in the fluorapatite crystal at a high temperature from a trapped globule
of carbonate melt. The LREE, possibly tolerated in the structure of calcite at a high
temperature, could be expected to be expelled from the structure upon cooling. It will be
necessary to test the hypothesis by doing energy-dispersion analysis in transmission
electron microscopy to identify the pigment.
Betafite is another accessory mineral found in orange dikes along the road cut. Its
size ranges from less than a millimeter to 0.5 cm across. The crystals are roundish, but
many are octahedra. All are metamict. Some betafite grains from the road cut were
analyzed with an electron microprobe by Andrea Čobić at the Institute of Mineralogy and
Petrology of Zagreb, Serbia. She found that the composition of the betafite-group mineral
is intermediate between oxycalciobetafite and oxyuranobetafite. In a back-scattered
48
electron image (Fig. 5.18), the betafite shows a dark rim and a light-colored center owing
to different contents of U in the grain.
Cathodoluminescence microscopy
In this study, a visual qualitative investigation of cathodoluminescence of calcite
in polished thin sections and grain mounts was made. By visual investigation, the calcite
can be classified as bright, dull or non-luminescent (Machel, 1985). Orange calcite has an
intense and bright orange luminescence, but the orange color is not uniform, and it is
more intense along the cleavages. The ions Mn2+, Sm3+ and Eu3+ are all known to cause
an orange CL of calcite; the bands are very close to each other in wavelength, and are
visually indistinguishable. The Mn2+ ion produces a luminescence at a wavelength of
approximately 600 nm, and
10-20 ppm Mn2+ is sufficient to produce the orange
luminescence (Machel et al., 1991). Image acquisition times varied depending upon the
CL intensity, but were generally in the range 5–56 s. Manganese is so plentiful here that it
likely exerts the main control on the intense orange luminescence; the level of Sm and Eu
are much lower in the orange calcite: 17.9 ppm Sm, 4.1 ppm Eu.
49
TABLE 5.3. AVERAGE COMPOSITION OF
ORANGE CALCITE, CHELSEA ROAD CUT,
QUEBEC
sample
n
MgO wt.%
MnO
CaO
FeO
NiO
CO2
SO3
CoO
SrO
Total
Mg apfu
Mn
Ca
Fe
Ni
C
S
Co
Sr
Total
FS1
FS5
C2
6
0.78
0.09
55.64
0.20
0.04
42.97
0.01
0.00
0.27
100.00
6
0.22
0.11
54.55
0.12
0.05
44.86
0.02
0.00
0.08
100.00
5
0.48
0.14
55.00
0.16
0.02
43.94
0.01
0.00
0.23
100.00
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
0.01
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
0.01
0.00
0.99
0.00
0.00
1.00
0.00
0.00
0.00
2.00
Note: these are results of electron-microprobe
analyses, counting time: 20 s. n: number of
analyses made. The grains are unzoned. The
amount of CO2 is calculated on the basis of
stoichiometry.
50
TABLE 5.4. WHOLE-ROCK COMPOSITION OF ORANGE AND PINK DIKE ROCKS
FROM CHELSEA AND ORANGE DIKE ROCK FROM MONT-TREMBLANT, QUEBEC
Sample
SiO2 wt.%
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
FS1
0.43
0.02
0.21
0.38
0.09
0.87
52.60
0.00
0.00
0.04
FS2
SJ6
2.78
0.04
0.37
0.75
0.09
2.60
49.41
0.03
0.01
0.03
0.19
0.01
0.13
0.13
0.02
0.06
53.44
0.00
0.01
0.77
BaO ppm
Ce
Co
Cr2O3
Cu
Ni
Sc
V
Zn
LOI
Total
FS1
FS2
SJ6
13.9
336
5
0.5
12
<d.l.
<d.l.
<d.l.
<d.l.
43.16
97.83
74.0
594
6
7.8
7
<d.l.
<d.l.
10.9
<d.l.
41.09
97.26
26.3
302
5
0.7
10
<d.l.
<d.l.
11.2
<d.l.
42.66
97.43
Compositions were acquired by the XRF technique. < d.l.: below detection limit. FS1: orange dike
rock, Chelsea; FS2: pink dike rock, Chelsea; SJ6: orange dike rock, Mont-Tremblant.
TABLE 5.5. TRACE-ELEMENT CONCENTRATIONS IN ORANGE AND PINK
DIKE ROCKS FROM CHELSEA AND ORANGE DIKE ROCK FROM
MONT-TREMBLANT, QUEBEC
FS1
Sr ppm
Y
Ba
La
Ce
Pr
Nd
Sm
Eu
3075
137.7
23291
34.4
97.5
15.1
73.8
17.9
4.1
FS2
SJ6
2003
90.7
41294
64.2
143.3
19.0
81.5
16.6
3.5
3659
57.8
40272
78.2
162.4
18.8
68.6
12.1
1.8
Gd ppm
Tb
Dy
Ho
Er
Tm
Yb
Lu
Th
U
FS1
FS2
SJ6
21.6
3.2
19.8
4.3
12.9
1.9
13.2
2.1
0.2
0.0
16.0
2.3
13.5
2.8
8.4
1.2
8.3
1.3
1.1
0.0
11.1
1.6
10.5
2.1
6.2
0.9
5.9
0.8
2.0
0.8
Note: The results of analyses done on weak acid leaches, using ICP-MS (solution mode),
are expressed in ppm (ug/g). Detection limits (3x background s.d.) are 0.005 ppm for the
REE, Th, and U. FS1: orange dike rock, Chelsea; FS2: pink dike rock, Chelsea; SJ6:
orange dike rock, Mont-Tremblant.
51
Fig. 5.15. Chondrite-normalized REE plot (Boynton 1984) of
samples of carbonate dike rocks. FS1: orange dike rock, FS2:
pink dike rock, Chelsea road cut; SJ5: orange dike rock, MontTremblant.
52
Fig. 5.16. Globules of orange calcite trapped
in fluorapatite, and here tentatively interpreted
to be an inclusion of melt, Yates mine, Otter
Lake, Quebec. Width of the fluorapatite
crystal: 5 cm.
Fig. 5.17. Plane-polarized light image of an orange globule of calcite
trapped in fluorapatite, Yates mine, Otter Lake, Quebec, provided by Prof.
George Rossman. Exsolution of an orange pigment from calcite at a low
temperature seems consistent with a high-temperature origin of calcite. Field
of view: 2 mm.
53
Cal
Bet
Gn
Fig. 5.18. Oxycalciobetafite in orange calcite, southeastern ramp, Chelsea
road cut. The crystal has a light center and a dark rim depleted in U. Galena
decorates the rim of the crystal. (SEM-BSE photo, A. Čobić, pers. commun.,
2012).
Fig. 5.19. Cathodoluminescence image of orange calcite shows an intense
orange color, which is likely due to the presence of Mn2+ and possibly also
Sm3+ and Eu3+. Beam voltages ranged from 4.2-4.7 kV at 0.5 mA current,
60-70 mTorr operating pressure and 27.2 s exposure time, Chelsea road cut,
Quebec. Note that the orange color is not uniform; it is more intense along
the cleavages. Width of the field of view: 3.1 mm
54
PINK CALCITE DIKE ROCK
The pink calcite dike rock is characterized by the dominance of coarse grains of
pink calcite, locally grading to yellow calcite. Some samples are crossed by narrow veins
of gray calcite (Fig. 5.20). A sample of pink carbonate dike has been found to host
slender crystals of diopside in a spherulitic array (Fig. 5.21), consistent with rapid growth
in a melt supersaturated in diopside. Note that there is a thin film of calcite between all
juxtaposed elongate crystals. The pink carbonate dike also contains coarse euhedral
pargasite, phlogopite, and pyrrhotite, the latter in the form a vein. In thin section, the pink
calcite is coarse grained, and the gray calcite along the veinlets is finer grained. There is
evidence of mild deformation in calcite in the form of slightly bent twins. The calcite also
typically contains dark rhombohedra of dolomite between 6 and 28 μm across (Fig. 5.22).
These rhombohedra recall those described by Dr. Ralph Kretz at Otter Lake as resulting
from exsolution of a high-temperature calcite solid-solution (Kretz, 1988). The dolomite
rhombohedra are distributed unevenly; their edges parallel the cleavages of the host.
Anhedral apatite decorated with tiny grains of secondary xenotime and monazite
is common in the pink calcite. One sample contains a large accumulation of pyrrhotite (8
× 10 cm). Elsewhere, the pink marble contains globules of pyrrhotite + chalcopyrite. It is
possible that these clots and masses of sulfide represent an immiscible sulfide melt in the
carbonate melt. In addition, there are elongate grains of celestine, barite and apatite
(Figs. 5.23, 5.24). Allanite is another common inclusion. It is found in two modes of
occurrence, as in the orange calcite. An early generation of allanite is found as irregular
grains with calcite and inclusions of fine-grained magnetite. A late allanite decorates the
55
contact around forsterite grains and along cracks, commonly associated with serpentine.
In pink calcite, forsterite grains are altered to a serpentine-group mineral along cracks.
Magnetite is an expected product of serpentinization of forsterite (Figs. 5.25, 5.26). The
pink calcite also contains isolated and complexly zoned euhedral grains of apatite (Fig.
5.27) that seem to have been resorbed slightly. The apatite contains monazite, anhydrite
and dolomite inclusions (Fig. 5.28). The grains of diopside are roundish and full of
inclusions of epidote, amphibole, chlorite and calcite. Chlorite grains are decorated with a
REE silicate, possibly caysichite (Ca yttrium silicate) (Fig. 5.29). The presence of REE
along cracks inside olivine is suspicious because olivine cannot host rare-earth elements
in its structure.
56
Cal
Phl
Fig. 5.20. Pink calcite grading to orange-yellow calcite. Calcite hosting an
accumulation of phlogopite, indicated by Phl, is generally gray. Width of
field of view: 105cm, Chelsea road cut, Quebec.
Di
57
Di
Cal
Fig. 5.21. Top: pink calcite-dominant dike rock with coarse stout crystals of
diopside. Below: the crystals of diopside define a spherulitic array, with
prisms advancing into the calcite matrix. Sample: FAH105. Width of
specimen: 17 cm
58
Dol
Fig. 5.22. Oriented dolomite rhombohedra (Dol, dark) interpreted to have
formed by exsolution in pink calcite, Chelsea road cut, Quebec. Sample FS2.
BSE image, acquired with an electron microprobe.
Dol
Xnt
Cal
Ap
Cls
Fig. 5.23. Inclusions in pink calcite include tiny grains of xenotime as a
decoration around and within subhedral inclusions of apatite. Dolomite is
disseminated within pink calcite, Chelsea road cut, Quebec. Sample FS2,
BSE image acquired with an electron microprobe, Cls: celestine.
59
Cal
Ap
Cls
Dol
Fig. 5.24. Euhedral prisms of apatite, clouds of dolomite specks, and a
grain of celestine included in pink calcite, Chelsea road cut, Quebec.
Sample FS2, BSE image acquired with an electron microprobe.
Cal
Phl
Mgt
Srp
Phl
Aln
Srp
Fig. 5.25. Phlogopite, serpentine and magnetite inclusions in pink calcite
Chelsea road cut, Quebec. This magnetite is primary and so strikingly
anhedral that it may well have been resorbed. Sample FS3, BSE image with
an electron microprobe.
60
Aln
Cal
Cal
Srp
Aln
Cal
Cal
Fo
Mgt
Spl
Fig. 5.26. An anhedral grain of olivine (Fo) is locally transformed to
serpentine along cracks. The serpentine is decorated with allanite. Magnetite,
zinc-rich spinel and calcite are included in olivine; at the upper right; coarse
anhedral allanite contain calcite inclusions. Its shape suggests that it has
been resorbed. Sample FS3, BSE image, acquired with an electron
microprobe.
Cal
Ap
Fig. 5.27. Apatite with complex zoning in pink calcite, Chelsea road
cut, Quebec. There are clear signs of resorption of the apatite.
Sample FS3. BSE image, acquired with an electron microprobe.
61
Anh
Ap
Cal
Mnz
Fig. 5.28. Anhedral apatite, presumably owing to dissolution, with
inclusions of monazite and euhedral anhydrite, and clouds of dolomite,
Chelsea road cut. Note the presence of disseminated dolomite of exsolution
origin in calcite. Sample FS3, BSE image, acquired with an electron
microprobe.
Cal
Chl
Phl
Fig. 5.29. Silicate containing Ca, Y, La and Ce, possibly caysichite-(Y), as a
secondary mineral in chlorite in pink calcite, Chelsea road cut, Quebec.
Sample FS3, BSE image, acquired with an electron microprobe.
62
Cal
Composition of the pink calcite
Selected samples of pink calcite have been analyzed. Results of the electronmicroprobe analyses, presented in Table 5.6, show that the pink calcite is enriched in Mn,
Mg, Fe and Sr, as is the orange calcite, compared to calcite in the regional marble. The
dolomite rhombohedra (Table 5.7) contain less Sr and more Fe than the enclosing calcite,
as was found by Dr. R. Kretz at Otter Lake. The pair calcite–dolomite provided him with
a estimate of the minimum temperature of dolomite formation, in the range 470-490°C
(Kretz, 1988). The bulk chemical composition of the pink calcite (FS2) indicates an even
higher Ce content (594 ppm) than the average regional marble (Table 5.4).
In terms of trace-element data, the pink calcite is rather similar to the orange
calcite (Table 5.5). The REE pattern of pink calcite (Fig. 5.15) shows an enrichment in
both light and heavy REE, with a negative Eu anomaly, in comparison to calcite in the
regional marble. Among the carbonate dikes of the Chelsea road cut and Mont-Tremblant,
SJ6 shows the strongest enrichment in REE elements and has the highest levels of U and
Th.
Cathodoluminescence microscopy
Pink marble has an orange luminescence, but it is less intense than that in orange
calcite; also, it is not uniform and is brighter along the cleavages (Fig. 5.30). The orange
CL color is consistent with the presence of Mn2+ (dominant), Sm3+ and Eu3+, all of which
can produce an orange cathodoluminescence in calcite (Machel et al., 1991).
63
TABLE 5.6. AVERAGE COMPOSITION OF PINK CALCITE, CHELSEA ROAD CUT
n
MgO wt.%
MnO
CaO
FeO
NiO
CO2
CoO
SrO
Total
C679
C674
C675
C679
C674
C675
5
5
5
5
5
5
0.40
0.10
53.84
0.25
0.00
44.98
0.00
0.42
100.00
0.41
0.13
53.41
0.29
0.00
45.29
0.00
0.46
100.00
0.42
0.15
55.13
0.34
0.00
43.47
0.00
0.46
100.00
0.38
0.07
54.27
0.21
0.00
44.67
0.00
0.37
100.00
0.41
0.13
53.41
0.29
0.00
45.29
0.00
0.46
100.00
Mg apfu
Mn
Ca
Fe
Ni
C
Co
Sr
Total
0.40
0.12
54.27
0.28
0.00
44.47
0.00
0.43
100.00
Note: Electron-microprobe technique, beam size: 10 μm, Counting time: 20 s, n: number of
analyses. The grains are unzoned.
TABLE 5.7. AVERAGE COMPOSITION OF DOLOMITE
IN PINK CALCITE
n
MgO wt.%
MnO
CaO
FeO
NiO
CO2
CoO
SrO
Total
FS2
5
20.87
0.23
28.90
1.26
0.01
48.70
0.00
0.03
100.00
FS3
5
21.00
0.15
30.45
0.70
0.00
47.63
0.00
0.07
100.00
Mg apfu
Mn
Ca
Fe
Ni
C
Co
Sr
Total
FS2
5
0.48
0.00
0.47
0.02
0.00
1.00
0.00
0.00
2.00
FS3
5
0.48
0.00
0.50
0.01
0.00
1.00
0.00
0.00
2.00
Note: Electron-microprobe technique, beam size: 10 μm, Counting time: 20 s
n: number of analyses.
64
Fig. 5.30. Cathodoluminescence image of pink calcite. The orange color, due
to Mn2+ (mostly), Sm3+ and Eu3+., is not uniformly distributed, and not as
intense as in the orange calcite. Beam voltages ranged from 4.2 to 4.7 kV at
0.5 mA current and 60-70 mTorr operating pressure and 60 s exposure time.
Width of the field of view: 3.1 mm.
.
BLUE MARBLE
The blue marble (Fig. 5.31) is coarse grained, massive and associated with
pyroxenite dikes. Unlike the orange and pink carbonate rocks, the calcite making up this
rock is relatively free of included minerals. There is no spatial relationship between blue
marble and orange or pink carbonate dike rocks. The blue crystals of calcite have variable
hues. An intense blue marble from a locality in the Adirondacks is included for
comparison. Grains of diopside are small of (~100-200 μm) and roundish (Fig. 5.32).
Brucite, olivine, amphibole, phlogopite and inclusions that contain the REE were nor
observed. In thin section, large twinned grains of calcite are slightly deformed and have a
typically granoblastic texture. Inclusions of diopside, plagioclase and quartz are common
(Fig. 5.33).
65
gray gneiss
blue marble
(A)
(B)
Fig. 5.31. (A): Massive blue marble along the Chelsea road cut.
(B): Representative sample of blue marble. Note the absence of included
phases and the coarse grain-size. Width of sample: 10 cm.
66
Di
Di
Cal
Di
Fig. 5.32. A representative image of blue marble in thin section. It shows
roundish inclusions of diopside, most likely of metamorphic origin. Note the
absence of dolomite rhombs. Back-scattered electron image of sample FS4,
Chelsea road cut, acquired with an electron microprobe.
Di
Di
Cal
Di
120
Fig. 5.33. Inclusion of euhedral diopside in blue marble, Chelsea road cut,
Quebec. Note the granoblastic texture. Sample FS4, cross-polarized light,
width of field of view 3 mm.
67
Composition of blue marble
Sample FS4 was chosen as the reference blue marble owing to its abundance at
the road cut. The calcite is virtually pure: ~0.01 wt.% MnO, ~0.01% MgO, ~0.02% SrO,
without detectable Fe (Table 5.8). These concentrations are considered to be roughly the
same as those in calcite in the regional marble. An XRF analysis of the blue marble FS4
(whole rock) gave low concentrations of Mn, Mg, Fe and Ce. Sample NY2, in
comparison, is richer in included silicate (Table 5.9). An ICP-MS analysis of the whole
rock confirms that the blue marble FS4 is relatively depleted in both light and heavy REE
(Table 5.10). A plot of the trace-element profile of the two samples of blue marble is
illustrated in Figure 5.34. Sample NY2 is richer in these elements than FS4, presumably a
reflection of the non-carbonate fraction in that rock. The Eu anomaly in NY2 is similar to
that in other carbonate samples in the Chelsea road cut. Both samples are LREE-enriched,
but the total REE content is a mere fraction of what is found in the orange and pink
carbonate dike rocks.
Cathodoluminescence microscopy
Sample FS4 has a low concentration of Mn and REE activators. As a result, the
average cathodoluminescence is perceptible but not strong. It has dull brown
luminescence, which is a bit lighter along the cleavages (Fig. 5.35).
68
TABLE 5.8. AVERAGE COMPOSITION OF BLUE
CALCITE IN SAMPLES OF BLUE MARBLE
ALONG THE CHELSEA ROAD CUT
Sample
n
MgO wt.%
MnO
CaO
FeO
NiO
CO2
SO3
CoO
SrO
Total
Mg apfu
Mn
Ca
Fe
Ni
C
Co
Sr
Total
FS4
5
0.01
0.01
56.87
0.00
0.08
42.99
<d.l.
0.01
0.02
100.00
FS4b
5
0.00
0.01
54.95
0.00
0.07
44.95
<d.l.
0.01
0.01
100.00
C6-7
6
0.10
0.01
56.15
0.01
0.00
43.68
<d.l.
0.01
0.02
100.00
C6-4
6
1.62
0.01
54.26
0.00
0.01
44.05
<d.l.
0.00
0.04
100.00
0.00
0.00
1.02
0.00
0.00
0.99
0.00
0.00
2.01
0.00
0.00
0.97
0.00
0.00
1.01
0.00
0.00
1.99
0.00
0.00
1.00
0.00
0.00
1.00
0.00
0.00
2.00
0.04
0.00
0.96
0.00
0.00
1.00
0.00
0.00
2.00
Note: Electron-microprobe technique, beam size: 100 μm,
counting time: 20s, n: number of analyses; the grains are
unzoned. <d.l.: below detection limit,
69
TABLE 5.9. WHOLE-ROCK COMPOSITION OF BLUE MARBLE FROM THE CHELSEA
ROAD CUT AND ADIRONDACKS, NEW YORK
SiO2 wt.%
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
FS4
NY2
d.l.
1.77
0.02
0.26
0.06
0.01
0.41
53.86
0.02
0.08
0.01
8.48
0.13
2.10
1.20
0.01
1.07
47.37
0.22
0.84
0.02
60
25
120
25
25
95
15
35
25
35
BaO ppm
Ce
Co
Cr2O3
Cu
Ni
Sc
V
Zn
LOI
Total
FS4
NY2
d.l.
62
38
2
1
7
<d.l.
< d.l.
9
< d.l.
41.93
98.44
510
37
6
12
30
< d.l.
< d.l.
25
< d.l.
35.63
97.13
12
15
10
10
2
3
7
7
2
100
d.l.: detection limit, XRF technique, FS4: blue marble, Chelsea; NY2 blue marble, Adirondacks,
New York.
TABLE 5.10. TRACE-ELEMENT CONCENTRATIONS IN
BLUE MARBLE FROM THE CHELSEA ROAD CUT AND
ADIRONDACKS, NEW YORK
Sr ppm
Y
Ba
La
Ce
Pr
Nd
Sm
Eu
FS4
NY2
287
2.39
32724
7.98
11.56
1.16
3.59
0.49
0.11
2928
5.85
12778
6.37
13.01
1.53
5.78
1.12
0.21
Gd ppm
Tb
Dy
Ho
Er
Tm
Yb
Lu
Th
U
FS4
NY2
0.35
0.05
0.33
0.07
0.18
0.02
0.14
0.02
0.05
0.01
1.02
0.15
0.92
0.19
0.54
0.08
0.50
0.07
0.28
0.09
Note: The results are expressed as ppm (μg/g). Analyses done on
weak acid leaches, using ICP-MS. Detection limits (3x background
s.d.) 0.005 ppm for the REE, Th and U.
FS4: blue marble, Chelsea road cut. NY2: blue marble, Adirondacks,
New York.
70
Fig. 5.34. Chondrite-normalized REE plot of blue marble FS4 of the
Chelsearoad cut and NY2, Adirondacks, New York. For comparison,
regional marble, C50 and SJ4 are plotted. The chondrite values are thoes
of Boynton (1984).
Fig. 5.35. Cathodoluminescence image of blue calcite is dark brown and
weak. Beam voltages ranged from 4.2 to 4.7 kV at 0.5 mA current and 6070 mTorr operating pressure and 52 s exposure time; sample FS4. Width of
the field of view: 3.1 mm.
71
THE COMPOSITION OF INCLUDED MINERALS
This part of the thesis will focus on the mineral inclusions in the samples of
colored carbonate. Diopside, pargasite and phlogopite are the dominant silicates enclosed
in the calcite-dominate rocks. Small grains of forsterite are found in regional marble and
pink calcite; it is partly replaced by serpentine. Coarse crystals of apatite and titanite are
found in orange calcite at Mont-Tremblant. Pyrrhotite and pyrite are present in pink and
orange calcite. In one sample, a large accumulation of pyrrhotite (8 × 10 cm) was found.
The dominant secondary minerals encountered are a serpentine-group mineral, probably
lizardite, and chlorite.
OLIVINE
Olivine is observed as anhedral high-relief inclusions in pink calcite and regional
marble. The crystals are replaced along cracks and at the rim by a serpentine-group
mineral. The olivine (Table 5.11) has an Mg number [Mg/(Mg + Fe)] of 0.91. In this
rock, the forsterite grains are round or nearly so because they presumably rolled as the
marble was undergoing dynamic recrystallization. They are surrounded with valleriite
4(Fe,Cu)S•3(Mg,Al)(OH)2 (Fig. 5.36). Calcite is present along cracks, and fine-grained
magnetite does occur in the olivine grains. A very small inclusion next to the magnetite is
likely a Zn-rich spinel (Fig. 5.26) Olivine is abundant in regional marble and in pink
calcite, but it is absent in orange calcite. Its magnesian composition is consistent with an
origin by reaction of dolomite with silica or a silicate.
72
Fo
Srp
Srp
Brc
Cal
valleriite
Srp
Srp
Srp
Srp
.
Fig. 5.36. Image of the regional marble containing olivine altered to
serpentine. The grains of serpentinized olivine are partly surrounded by
valleriite. Sample FAH134. Back-scattered electron image acquired with an
electron microprobe.
TABLE 5.11. AVERAGE COMPOSITION OF OLIVINE GRAINS IN PINK
CALCITE, CHELSEA ROAD CUT
n
SiO2 wt.%
TiO2
Al2O3
FeO
MnO
MgO
CaO
Total
Mg#
FS2
FS3
FS2
FS3
5
5
5
5
40.88
0.01
0.00
9.13
0.32
50.07
0.03
100.44
0.91
40.67
0.00
0.01
9.16
0.27
50.07
0.15
100.30
0.91
Si apfu
Ti
Al
Fe
Mn
Mg
Ca
Total
0.99
0.00
0.00
0.19
0.00
1.82
0.00
3.00
0.99
0.00
0.00
0.19
0.00
1.82
0.00
3.00
Note: Samples FS2 and FS3 are pink calcite-dominant dike rocks
sampled along the Chelsea road cut. These are results of electronmicroprobe analyses; n: number of analyses, total Fe expressed as
FeO.
73
PYROXENE
Coarse, blocky, euhedral crystals of very dark green diopside are found in pink
and orange carbonate dikes. Locally, the diopside crystals attain 4 cm in length. The
spherulitic array of slender crystals is indicative of rapid growth, possibly as a result of a
quench in the igneous environment (Fig. 5.37). Orange carbonate dikes next to the host
rock typically show a selvage of euhedral diopside crystals facing inward toward the
carbonate (Fig. 5.38). In such diopside grains, there are inclusions of phlogopite with
titanite, chlorite, allanite, apatite and calcite. The euhedral crystals of diopside in a pink or
orange calcite matrix are large, with sharp edges. They are interpreted as phenocrysts in
the carbonate matrix. Results of electron-microprobe analyses of diopside are reported in
Table 5.12. In contrast, the blue marble shows small roundish grains of diopside, which
are considered to be metamorphic in origin. The round shape of the grains of
metamorphic diopside presumably reflects the fact that the grains actually rolled as the
rock was undergoing prograde metamorphism and plastic deformation.
Diopside phenocrysts in an orange to pink carbonate dike, sample FAH100, have
an Mg# of 0.88, whereas the diopside inclusions in blue marble, of metamorphic origin,
have an Mg# value of 0.96. The diopside phenocrysts in orange, pink and gray carbonate
have a higher Al content (4-7% Al2O3) than diopside inclusions in blue marble.
Metamorphic diopside is known to generally contain less than 0.4% Al2O3 (Nakano et al.,
1994).
74
Di
Cal
Di
Fig. 5.37. Slender prisms of diopside in pink calcite define a
macrospherulitic texture. Between the crystals in the radial array are thin
films of calcite. Color differences among diopside crystals are an artifact of
lighting. Sample: FAH103. See also Figure 5.21. Width of the sample: 17
cm.
Di
Cal
Fig. 5.38. Orange carbonate matrix next to gray gneiss. Note the
nucleation and growth of diopside prisms from the gneiss wall inward
into the calcite. Southeastern ramp of the road cut going north.
75
TABLE 5.12. AVERAGE COMPOSITION OF REPRESENTATIVE
PYROXENE IN THE CARBONATE-DOMINANT ROCKS
OF THE CHELSEA ROAD CUT
n
SiO2 wt.%
TiO2
Al2O3
FeO
MnO
MgO
CaO
Na2O
K2O
F
Cl
Total
Si apfu
Al
Ti
Mg
Fe
Mn
Ca
Na
K
F
Cl
Total
Mg#
FS4
FS5
3
6
FAH105
2
FAH106
5
FAH111
54.69
0.05
0.66
1.34
0.08
17.55
25.35
0.46
0.02
0.02
0.00
100.24
53.28
0.04
0.76
5.92
0.18
14.96
24.30
0.53
0.03
0.01
0.00
100.05
51.02
0.53
3.87
4.16
0.08
15.28
25.34
0.17
0.01
0.00
0.01
100.57
48.64
0.85
6.83
5.03
0.10
13.67
24.36
0.40
0.02
0.03
0.01
99.95
49.85
0.59
4.81
6.02
0.14
13.60
24.05
0.54
0.03
0.03
0.01
99.69
1.98
0.03
0.00
0.95
0.04
0.00
0.98
0.03
0.00
0.00
0.00
4.02
0.96
1.97
0.03
0.00
0.83
0.18
0.01
0.96
0.04
0.00
0.00
0.00
4.03
0.81
1.87
0.17
0.01
0.84
0.13
0.00
1.00
0.01
0.00
0.00
0.00
4.03
0.87
1.80
0.30
0.02
0.76
0.16
0.00
0.97
0.03
0.00
0.00
0.00
4.04
0.83
1.86
0.21
0.02
0.76
0.19
0.00
0.96
0.04
0.00
0.00
0.00
4.04
0.80
5
Note: All samples are from the Chelsea road cut. Pyroxene inclusions:
FS4 from blue marble, and FS5 from orange carbonate dike rock.
Pyroxene phenocryst: FAH105 from pink carbonate rock, FAH106 from
orange carbonate rock, FAH111 from pink-orange dike rock. These are
results of electron-microprobe analyses; n: number of analyses. Diopside
inclusions in FS4 and FS5 have lower Al than diopside phenocrysts.
Total Fe is expressed as FeO. Mg#: Mg / (Mg + Fe + Mn).
76
AMPHIBOLE
Orange and pink calcite-dominant dike rocks contain coarse euhedral, dark
prismatic amphibole crystals 2-3 cm across enclosed in calcite; they are considered to
have grown in a carbonate medium. In the field, they accumulate preferentially in the
center of orange-pink dikes, possibly by flow differentiation (Fig. 5.39). The amphibole
seems to be "decorated" by another amphibole that nucleated along the cleavages and on
the periphery of the grain (Fig. 5.40). The color and birefringence of the two amphiboles
are different in thin section. In back-scattered electron images, the second amphibole is
shown to have nucleated around the grain and along cleavages in a comb pattern, with
prisms commonly oriented toward the calcite host (Figs. 5.41, 5.42). The average
compositions of the two amphiboles are shown in Table 5.13. The amphibole phenocryst
in FAH 100, from a pink-orange dike, is close to the pargasite end-member, with values
of relatively high Al, Na, K and F contents, whereas pargasite inclusions in another pinkorange dike show lower values of Al, Na, K and F content (Table 5.13). The amphibole
that nucleated along the cracks and cleavages and around the pargasite grain is ferroactinolite free of F (Table 5.14). It nucleated on the pargasite–calcite boundary and grew
into the calcite as an epitactic overgrowth, also along cleavage planes. There are also
some nano-inclusions along pargasite cleavages that need to be analyzed; the only phase
that is visible and analyzed is ferro-actinolite. In addition, a strange intergrowth of
pargasite and diopside that is possibly due to the early crystallization of diopside in
droplets of an immiscible mafic melt was described earlier.
77
(A)
(B)
Fig. 5.39. (A): Pink to gray carbonate dike crowded with pargasite crystals,
Chelsea road cut. (B): A close-up picture of carbonate rock full of
pargasite. Crystals are coarse, up to 3 cm across, and enclosed by pink to
gray calcite. Phlogopite with titanite inclusions also is present in this rock.
Width of yellow label: 10 cm.
78
Fac
Prg
Phl
Cal
Ttn
Phl
Fig. 5.40. Two generations of amphibole are visible in pink-orange calcite;
ferro-actinolite (Fac) nucleated around pargasite and along cracks and
cleavages. Phlogopite grains adjacent to pargasite are "decorated" with
titanite inclusions. Chelsea road cut, Quebec. Sample FAH100. Backscattered electron image acquired with an electron microprobe.
Fac
Cal
Prg
Cal
Prg
Phl
Fig. 5.41. Two generations of amphibole in pink-orange calcite. Ferroactinolite (Fac) nucleated on pargasite and exhibits a comb-texture growth
toward the carbonate matrix. Chelsea road cut. Sample FAH101. Backscattered elecron image acquired with an electron microprobe.
79
Phl
Fac
Cal
Prg
Phl
Fig. 5.42. Pink-orange calcite, showing pargasite and ferro-actinolite (Fac)
that nucleated at the pargasite–calcite boundary, and grew into the carbonate
medium. The implication of this texture is epitactic growth of Fac on Prg into
a melt phase. Chelsea road cut. Sample FAH100. Back-scattered electron
image acquired with an electron microprobe.
TABLE 5.13. AVERAGE COMPOSITION OF PARGASITIC AMPHIBOLE
FROM CARBONATE DIKE, CHELSEA ROAD CUT
n
SiO2 wt.%
TiO2
Al2O3
FeO
MnO
MgO
CaO
Na2O
K2O
F
Cl
Total
FS5
3
53.06
0.14
3.41
8.00
0.15
18.87
12.49
0.93
0.37
0.43
0.03
97.69
FAH100
11
42.72
0.7
13.26
6.22
0.11
17.31
12.75
2.36
1.73
1.37
0.06
97.85
FAH101
4
43.97
0.91
12.21
3.66
0.08
19.34
12.83
2.32
1.55
0.86
0.02
97.39
Si apfu
Ti
Al
Fe
Mn
Mg
Ca
Na
K
F
Cl
Total
Mg#
FS5
FAH100
FAH101
7.54
0.01
0.57
0.95
0.02
4.00
1.90
0.26
0.07
0.19
0.01
15.52
0.80
6.21
0.08
2.28
0.76
0.01
3.75
1.99
0.67
0.32
0.48
0.01
15.56
0.83
6.32
0.10
2.07
0.44
0.01
4.15
1.98
0.65
0.29
0.38
0.01
16.40
0.90
Note: electron-microprobe technique; Samples are from orange-pink dike, Chelsea road cut.
n: number of analyses. Based on 24 [O + OH + F + Cl] formula. FS5 has pargasite inclusions with
low level of Al and F, whereas FAH 100 and FAH101 are pargasite phenocrysts with higher Al
and F. Total Fe is expressed as FeO. Mg#: Mg/ (Mg + Fe + Mn).
80
TABLE 5.14. AVERAGE
COMPOSITION OF FERROACTINOLITE FROM ORANGE
CARBONATE DIKE ,
CHELSEA ROAD CUT
n
SiO2 wt.%
TiO2
Al2O3
FeO
MnO
MgO
CaO
Na2O
K2O
F
Cl
Total
Mg #
11
7.96
0
0.02
3.07
0.06
1.92
1.99
0.01
0.01
0
0
11
Si apfu
Ti
Al
Fe
Mn
Mg
Ca
Na
K
F
Cl
15.04 Total
0.38
7.96
0
0.02
3.07
0.06
1.92
1.99
0.01
0.01
0
0
15.04
Note: electron-microprobe technique, n: number
of analyses, based on 24 [O + OH + F + Cl].
(Ca1.99 a0.01K0.01)Fe3.07Mg1.92Si7.96Al0.02O22(OH)2
Total Fe is expressed as FeO. Mg#: Mg/ (Mg +
Fe + Mn).
81
PHLOGOPITE
Euhedral phlogopite crystals, interpreted to be phenocrysts (Fig. 5.43) were
collected from pink-orange carbonate dikes. The crystals grow in the pink and orange
calcite-dominant dikes in random orientation, and form clusters. Phlogopite has an amber
dark brown to black color and ranges in size from a millimeter to 3 cm across. There is a
thin dark zone at the periphery of the crystals, and some areas of darkening inside the
crystals. The hypothesis of compositional zoning can be ruled out, as no compositional
differences were found in the lighter and darker areas. Needles of rutile and titanite
locally are very plentiful in the crystals (Fig. 5.44), and are crystallographically oriented
with respect to the host mica. The dark rim and darkened areas in the crystal are likely the
result of a concentration of these needles, which appeared late (i.e., fluid-induced). A
study of a thin flake of phlogopite shows an asterism, or alignment along a six-rayed star,
if a light source is viewed through the crystal normal to the plane of the sheets (Fig. 5.45).
Generally, the phlogopite is fresh, but minor degradation to chlorite can be observed. In
general, where there is an accumulation of phlogopite phenocrysts, pargasite is absent in
the dike.
The composition of phlogopite is shown in Table 5.15. Sample FS2 and FAH109
contain large phenocrysts of phlogopite with high levels of Ba (1.12 wt.%) and F
(3.56%), and with some Ti present (0.45%). The phlogopite exhibits minor solid-solution
toward kinoshitalite. The needles of titanite and rutile form a sagenitic texture, which is
characterized by slender, needle-like inclusions intersecting at an angle of 60° in a host
mineral; needles of titanite are more abundant than rutile (cf. Gary et al., 1972) (Fig.
5.45). Phlogopite shows minor evidence of deformation in thin section and hand
82
specimen (Fig. 5.46). Titanite is also found along the edge of phlogopite, in cases where
phlogopite is replaced by chlorite; titanite typically is enclosed in chlorite. Non-acicular
titanite is considered primary inside grains and secondary between sheets of phlogopite,
where it is decorated with tiny grains of a REE carbonate (Fig. 5.47). There are diopside
and pyrrhotite inclusions in phlogopite as well as trapped elongate inclusions of calcite
along sheets (Fig. 5.48). At Mont-Tremblant, in addition to the secondary titanite, one
also finds centimetric dark purplish brown crystals of titanite in orange dike rocks.
Figure 5.49 shows an interesting juxtaposition of the two generations of titanite.
By reconstructing the shape of droplet-shape inclusion of titanite and calcite attached to
needle-like titanite that grew along the cleavage, faces of this composite droplet-like
inclusion are parallel to the outer faces of the host phlogopite, in what seems to be a
negative crystal (Fig. 5.49). It is noteworthy that both phlogopite and chlorite may be
either free of titanite inclusions or titanite-bearing, indicating that conversion to chlorite
alone cannot account for the formation of the titanite inclusions. Titanite intergrowths
remained in the same orientation regardless of that conversion; the survival of titanite
inclusions shows that titanite is more resistant to alteration than phlogopite under the
prevailing conditions (Fig. 5.50).
83
Fig. 5.43. Coarse phenocrysts of phlogopite in orange-pink carbonate dike.
They seem to have a random orientation; sample FAH 109.
Fig. 5.44. Titanite and rutile needles in phlogopite. The needles cross each
other in projection through several layers; The inclined fine subhorizontal
black lines are the basal cleavage. Sample: FAH109. Plane-polarized light;
width of field of view is 3 mm.
84
Fig. 5.45. Optical study of single flake of phlogopite shows an asterism, or
six-rayed star in plane light; it is caused by oriented needles of titanite and
rutile. Width of field of view: 3 mm.
Ep
Ep
Phl
Cal
Kfs
Ttn
Phl
Chl
Ep
Fig. 5.46. Phlogopite is locally transformed to chlorite (darker area), with
titanite, calcite, epidote and K-feldspar inclusions in calcite. Sample:
FAH106. Back-scattered electron image acquired with an electron
microprobe.
85
Py
Po
Phl
Ttn
REE carbonate
Ttn
Phl
Fig. 5.47. Concentration of titanite and REE carbonate between calcite and
phlogopite and along other inclusions such as pyrrhotite and pyrite in
phlogopite. Sample: FAH109B. Back-scattered electron image acquired with
an electron microprobe.
Ttn
Phl
Po
Cal
Di
Fig. 5.48. Back-scattered electron image of phlogopite with titanite grains
and needle inclusions, calcite, pyrite and pyroxene. Note the presence of a film
of calcite between two phlogopite grains, Sample: FAH109C, pink calcite.
86
Ttn
Ttn
Phl
Cal
Fig. 5.49. SEM image of phlogopite shows a primary grain of titanite inside
phlogopite and a secondary one along the cleavage. They intersect at some
point. The subhedral shape of the composite calcite–titanite grain suggests a
negative crystal outline. Sample: FAH109. The phlogopite crystal is in a pink
carbonate dike rock.
Cal
Ttn
Ttn
Phl
Ttn
Fig. 5.50. SEM image of phlogopite with titanite inclusions of two types.
The top inclusion shows planar interfaces with a globule of calcite; the
hardness of titanite caused the late separation of sheets to be deflected
around the inclusion of primary titanite. Near the bottom of the image are
films of titanite that grew along the cleavages. Sample: FAH109.
87
TABLE 5.15. AVERAGE COMPOSITION OF PHLOGOPITE,
CHELSEA ROAD CUT
n
SiO2 wt.%
TiO2
Al2O3
FeO
MnO
MgO
CaO
BaO
Na2O
K2O
F
Cl
Total
Si apfu
Al
Ti
Fe
Mg
Mn
Ca
Ba
Na
K
F
Cl
Total
Mg#
FAH105 FAH106B
3
1
39.58
37.22
0.72
0.82
15.74
19.49
4.72
6.22
0.06
0.05
24.43
21.53
0.06
0.05
0.72
0.79
0.44
0.40
9.52
9.37
1.57
1.09
0.08
0.07
96.96
96.97
1.53
0.72
0.02
0.15
1.41
0.00
0.00
0.01
0.03
0.47
0.19
0.00
4.53
0.90
1.45
0.89
0.02
0.20
1.25
0.00
0.00
0.01
0.03
0.48
0.13
0.00
4.48
0.86
FAH109
17
40.94
0.45
13.29
2.47
0.02
25.59
0.02
1.12
0.51
9.64
3.56
0.02
96.13
FAH111
2
37.53
1.47
15.80
13.23
0.14
17.23
0.06
0.42
0.10
9.73
0.96
0.18
96.42
1.60
0.61
0.01
0.08
1.49
0.00
0.00
0.02
0.04
0.48
0.41
0.00
4.75
0.95
1.52
0.75
0.04
0.45
1.04
0.00
0.00
0.01
0.01
0.50
0.12
0.01
4.45
0.70
Note: The compositions were acquired withan electron
microprobe. All samples are from the Chelsea road cut.
FAH109 has largest crystals of phlogopite. n: number of
analyses. The calculation is based on 22[O + OH + F + Cl];
total Fe is expressed as FeO. Mg#: Mg/ (Mg + Fe + Mn).
88
THE ASSOCIATED ROCKS
The Grenville Province, and specifically in the study area near Chelsea, is
characterized by a complex geology with contrasting lithologic domains. There are gray
gneissic rocks that are locally migmatized, and calcite-dominant rocks, juxtaposed with
syenite and pyroxenite. The gneissic rocks vary in composition from leucogabbro to gray
gneiss of “intermediate” composition, which were deformed during the orogenic cycles,
metamorphosed and partially melted (Easton, 2000). Clinopyroxene, plagioclase,
amphibole, phlogopite and pyrite are present in the gneissic rocks. A typical Grenville
gneiss contains plagioclase, K-feldspar, quartz, sillimanite, biotite, garnet, hornblende,
calcium pyroxene and, rarely, orthopyroxene. Furthermore, there is veined gneiss that
contains biotite, quartz, plagioclase and locally grades into migmatite (Kretz, 1959). Kfeldspar is generally subordinate to plagioclase (Kretz, 1959).
Locally important are
dikes related to the Wakefield syenite–granite batholith, described by Béland (1954) and
Cartwright & Weaver (1993), which comprise K-feldspar, sodic plagioclase, quartz,
calcic pyroxene, hornblende, and titanite in variable proportions. Dikes of "normal"
syenite show a pale pink to greenish color. Such dikes of "normal" syenite are less
abundant along the Chelsea road cut than unusual zoned syenitic to monzonitic dikes that
have a white plagioclase-dominant rim and a reddish central zone (Fig. 5.51) . Also, the
gray gneiss is locally transformed to a pink rock in which the dominant mineral is
microcline. Such zones of microcline-rich assemblage are developed adjacent to the
calcite dikes. The pink potassic feldspathic rock is a metasomatized equivalent of the
gneiss rock and could be defined as a fenite because of the gradational nature of the
changes and involvement of alkali-rich fluids. Bodies of fenitized material cross-cut
89
gneiss, pyroxenite and carbonate dikes. They extend in different directions and form dike
and sills in the surrounding gneissic rocks. In fenite, there is abundant K-feldspar with
some euhedral apatite and pyrite inclusion and exsolution of sodic plagioclase in Kfeldspar (Fig. 5.54). Fenite dominantly consists of microcline and small amounts of
oligoclase exsolved in K-feldspar (Figs. 5.53, 5.54). The oligoclase shows a schiller
(iridescence) diagnostic of a peristerite association (exsolution-induced albite–oligoclase
pairs). A zone of pegmatite with potassic graphic granite is found near the zoned syenite
dikes and provide a clear indication that the metasomatized gray gneiss has begun to melt
locally. Such intrusive rocks indicate the importance of the local rheomorphism of fenites.
90
Fenite
Gneiss
carbonate
Fig. 5.51. Association of carbonate body, gneiss and feldspathic rocks
(fenite) The fenite is interpreted to represent metasomatized gneiss that
melted locally. A $2 coin is used as a scale. Northward access ramp on the
east side of Autoroute 5.
.
Cal
Ap
Ksp
Ap
Ab
Py
Fig. 5.52. Quartzofeldspathic rock with apatite, calcite, pyrite and albite
included in microcline. The microcline seems devoid of exsolved albite.
Sample: FAH140. Back-scattered electron image acquired with an electron
microprobe.
91
Pl
Pl
Ttn
Phl
Cal
Phl
Mgt
Ttn
Kfs
Ap
Kfs
Fig. 5.53. Pink microcline-dominant fenite on left and a white plagioclasedominant layer on the right of the image. This assemblage is developed next
to an orange dike; it does not have a normal igneous texture. Sample: FAH
140. Back-scattered electron image acquired with an electron microprobe.
Di
Kfs
Mgt
Di
Pl
Amp
Di
Ttn
Pl
Di
Fig. 5.54. Sodic-plagioclase-dominant domain in fenite. Note the plagioclase
"rods" in microcline, and the amphibole with oriented needles of magnetite,
an indication of a late increase in the fugacity of oxygen, possibly during
uplift. Sample FAH150. Back-scattered electron image acquired with an
electron microprobe.
92
CHAPTER 6. STABLE ISOTOPE COMPOSITION OF CALCITE
AND PYRRHOTITE IN ROCKS ENCOUNTERED
ALONG THE CHELSEA ROAD CUT
The stable isotope characteristics of rocks and minerals offer excellent insight into
their history. In this study, stable isotope data were acquired on calcite grains of various
colors (oxygen, carbon, and strontium) and on one sample of pyrrhotite from a pink
calcite dike (sulfur). Details of the analytical methods were presented in Chapter 4.
Unfortunately, silicate minerals in the carbonate dikes could not be analyzed in the
context of this investigation. They will need to be analyzed in future to evaluate the
degree to which they are in isotopic equilibrium with the carbonate host. The inferred
high temperature of equilibration of the assemblages along the Chelsea road cut is
expected to be reflected in inter-mineral isotope fractionations that tend to zero.
THE δ18O AND δ13C VALUES OF CALCITE
Calcite grains from various samples along the Chelsea road cut were hand-picked
for analysis. For purposes of comparison, samples of colored calcite from MontTremblant and the Adirondacks were included. A compilation of results is presented as
Table 6.1. In all, data on 39 samples of calcite are reported. The color-coded data are
plotted in Figure 6.1, and define a large spread of values ranging from a δ18O (SMOW)
close to 26‰ down to 11‰, and from a δ13C (PDB) of 3‰ down to -2‰. The trend
affects data points from a large geographic area, and indicates an overall systematic
decrease in both values in the direction of a mantle signature. A very similar trend was
documented in southern Madagascar by Pili et al. (1997) and Morteani et al. (2013), and
attributed to isotopic exchange of regionally developed metacarbonates in evaporitic
93
sequences with a fluid phase rising from the mantle along major shear zones in that
granulitic terrane.
Cartwright & Valley (1991) have surveyed the carbon and oxygen isotopic attributes
of regional marble in various parts of the Grenville Province. For the Adirondacks, they
found that a typical marble has a δ18O (SMOW) in the range 21–24‰. This range also is
typical of marble in the unexchanged areas of the Madagascar basement, sampled far
from the shear zones (Pili et al., 1997).
The orange-pink calcite along the Chelsea road cut, Mont-Tremblant and in the
Adirondacks of New York has significantly lighter δ18O values than 21–24‰; they range
largely between 14 and 18‰. In terms of δ13C, they range between 0 and -2‰. The
samples of minor marble described by Kretz (2001) are even lower in δ18O, down to
11‰. Kretz described this category of marble as having undergone a metasomatic
overprint. In contrast, values typical of the blue marble resemble those of the
unexchanged regional marble.
The array of data shown in Figure 6.1 resembles that recorded in the contactmetamorphic aureole developed in the Trenton limestone around the Mont Royal alkali
gabbro - essexite pluton, a Monteregian complex of Cretaceous age (Fig. 6.2, taken from
Deines & Gold 1969). The orthomagmatic fluid produced during the crystallization of the
mantle-derived Mont Royal gabbro and associated peridotitic cumulates and syenitic
differentiates interacted with the host limestone very efficiently, and “reset” the isotopic
signature of calcite in the limestone and in the intrusive rocks so that the samples now
contain a mixed crust + mantle signature. The isotopic exchange proceeded during the
brief cooling interval of this small pluton by a mechanism of solution and redeposition of
94
the calcite. The oxygen and carbon atoms are exchanged by dissolving calcite in the
ambient fluid and reprecipitating calcite in situ, probably in a multitude of steps. The
same process is proposed to explain the array of points in Figure 6.1, except that there are
clear indications that melting occurred following the solution-and-redeposition steps. The
array in Figure 6.1 seems to indicate that in areas of metasomatism of marble leading to
the formation of orange and pink calcite in the Grenville Province, a hot fluid phase
containing a mantle component clearly was involved. Melting also has taken place in
southern Madagascar in a similar context (Morteani et al. 2013). One should add that
unlike the Mont Royal pluton, the subjacent Wakefield syenitic pluton is inferred to be
crust-derived (though likely with a mantle contaminant), leading to the possibility that the
influx of fluid causing the metasomatic modification of the marble prior to its melting
may signal a younger influx of alkaline fluid (i.e., post Wakefield syenite).
Moecher et al. (1997) described dikes of “carbonatite” in the Central
Metasedimentary Belt zone of the Grenville Province near Minden, Ontario, close to the
Central Metasedimentary Belt Boundary Zone, dated at 1085-1035 Ma. They found δ18O
(SMOW) values of calcite in the range of 9.9–13.3‰ and δ13C in the range -4.8 to -1.9‰.
They interpreted these dikes as somehow related to the interaction of granitic pegmatites
with marble. It seems more likely that these dikes share the same origin as that
documented in this investigation.
95
TABLE 6.1. STABLE ISOTOPE COMPOSITION OF CALCITE
GRAINS FROM THE CHELSEA ROAD CUT,
MONT-TREMBLANT AND NEW YORK STATE
Sample Name
FAH 102
FAH 103
FAH 105
FAH 106
FAH 108-A
FAH 108-B
FAH 109-A
FAH 109-B
FAH 110
FAH 111-A
FAH 111-B
FAH 112
C-7
C-7-1
C-7-2
C-7-3
C-7-4
C-7-5
C-7-6
C-7-7
C-7-8
C-7-9
C-7-10
FAH 100
FAH 101
FS 1
FS 2
FS 3
FS 4
FS 5
SJ 1
SJ 2
NY 1
NY 2
NY 3
NY 4
NY 5
NY 6
NY 7
13
δ C (PDB)
-1.13
-1.03
-0.82
-0.90
-0.70
-0.62
-1.23
-1.30
-1.35
-0.99
-1.01
4.09
2.17
2.98
2.00
2.04
1.99
2.08
2.97
3.00
2.97
1.75
2.82
-1.38
-1.37
-1.18
-0.77
-0.83
5.03
-0.65
-2.15
-2.95
5.67
1.26
-2.42
2.11
-0.18
-6.73
-7.42
δ18O (SMOW)
15.61
14.23
16.99
15.06
16.82
16.92
17.62
17.72
13.69
16.95
16.90
20.81
21.01
25.91
20.28
25.04
18.79
18.36
18.52
26.10
23.77
18.20
20.96
17.10
15.87
16.63
17.47
16.83
25.34
16.24
16.04
12.30
27.49
18.24
15.22
25.64
19.83
14.64
15.26
color
O
O
O
O
O
O
O
O
O
O
O
B
W
B
W
W
O
O
O
W
W
W
W
O
O
O
O
O
B
O
O
O
B
B
O
B
O
O
O
Note: SJ: Mont-Tremblant, Quebec; NY: Adirondacks, New
York; FAH, C, FS: Chelsea road cut; O: orange, yellow and pink
carbonate dike rocks, W: white regional marble, B: blue marble,
Standard deviation is 0.02‰ for δ13C and 0.03‰ for δ18O. The
data are reported in ‰.
96
Fig. 6.1. Plot of isotopic values for samples of calcite from the Chelsea road cut, MontTremblant, Otter Lake, and the Adirondacks. Legend: black diamond: blue and white
marble, Chelsea road cut; orange diamond: orange-pink carbonate-dominant dike rocks,
Chelsea road cut; red diamond: regional marble next to Morin anorthosite (Peck et al.,
2005); blue circle: orange carbonate-dominant dike rocks, Mont-Tremblant; green
triangle: minor marble, Otter Lake (Kretz, 2001); black asterisk: major marble of Otter
Lake (Kretz, 2001); blue diamond: blue marble, Adirondacks, New York; olive green
cross: Oka carbonatite, Quebec (Cretaceous), indicative of mantle values (Deines, 1970).
Black arrow is maximum devolatilization (Pili et al., 1997). The data are reported in ‰.
Fig. 6.2. The carbon and oxygen isotopic composition of calcite in Trenton
limestone from the contact-metamorphic aureole of the mantle-derived Mont
Royal pluton and in the pluton itself, Montreal, Quebec (Deines & Gold,
1969). The data are reported in ‰.
97
THE 87Sr/86Sr VALUE OF CALCITE
The Sr composition of seawater seems to be constant all over the world, but it has
increased progressively with time (Fig. 6.3). Today, the
87
Sr/86Sr value is 0.70906 ±
0.00003 (Veizer et al., 1983). In the Mesoproterozoic ocean, values are not very well
known, because most of rocks deposited in oceans of that age were affected by
metamorphism as a result of subsequent orogenic cycles. Veizer & Compston (1976)
listed a possible interval of carbonate sedimentation in the Grenville Province of 11001400 million years. An inferred age of the limestone precursor of the Grenville regional
marble is here taken to be 1350 m.y., keeping in mind that it must have preceded the time
of inception of subduction and collision in the New York - Ontario - Quebec area, at
roughly 1280 m.y. (McLelland et al. 2010).
As a result of a general survey, Krogh & Hurley (1968) found Grenville-age
marble to have an initial Sr isotopic ratio in the range 0.7048-0.7050. This agrees with the
results acquired (Table 6.2) on samples of orange and pink marble from the Chelsea road
cut (0.7044-0.7051). One sample of blue calcite from the Adirondacks has a value of
0.7054. Taken at face value, these findings and the inferred isotopic composition of
seawater at 1350 m.y. (Fig. 6.3) are consistent with the presence of a mixture of crustderived Sr (dominant) and mantle-derived Sr in the calcite under study. This inference
rests on the assumption that the calcite precipitated in the Mesoproterozoic ocean had the
same value as the ocean water (i.e., there was negligible isotopic fractionation). It is
considered likely that the
87
Sr/86Sr values of the rocks in Table 6.2 were “reset”
downward slightly during the metasomatic overprint that made these rocks orange or red.
98
These adjustments occurred closer to 1 Ga years ago, as indicated by the red diamond in
Figure 6.3.
TABLE 6.2. INITIAL 87Sr/86Sr VALUE OF
CALCITE OF VARIOUS COLORS
Sample
Name
FS-1
FAH-112
FS-2
FAH-102
NY-2
87
Sr/86Sr
0.7047
0.7051
0.7047
0.7044
0.7054
color
ORANGE
BROWN
PINK
ORANGE
BLUE
The standard error associated with these
measurements is ±0.002.
Fig. 6.3. Variation in 87Sr/86Sr of seawater with time (Veizer & Compston, 1976). Note: red diamond is the
observed initial 87Sr/86Sr value of calcite in marble and carbonate dike rocks. Sedimentation is inferred to
have occurred 1350 m.y. ago. However, the metasomatic overprint that made the marble orange or pink at
roughly 1050 Ma probably did reset the Sr isotopic system, and decreased the values of that ratio slightly.
99
THE δ34S VALUE OF PYRRHOTITE IN PINK CALCITE
Some samples of pink-orange carbonate dike rock contain centimetric patches of
pyrrhotite with accessory chalcopyrite. One sample that contains a large area of pyrrhotite
(Fig. 6.4) was selected for microsampling at four spots. The four samples were analyzed
by the method of Bruchert & Pratt (1996).The values of δ34S range between 1.42 and
1.77‰ with respect to the Cañon Diablo troilite (Table 6.3). Such an interval of values is
not diagnostic of a specific environment of formation (Fig. 6.5). Values close to 0‰ are
typical of meteorites and mantle-derived igneous rocks, but non-biogenic sedimentary
sulfides derived from such rocks also can have a value close to 0‰ (Seal 2006).
100
Cal
Phl
Po
Fig. 6.4. Pink to gray carbonate dike rock containing a large domain of pyrrhotite. The
rock also contains phenocrysts of phlogopite and pargasite. Sample FAH115. Width of
field of view: 20 cm.
TABLE 6.3. VALUE OF δ34S
OF PYRRHOTITE IN PINK
CARBONATE DIKE ROCK,
CHELSEA ROAD CUT
1
2
3
4
δ34S
error
1.51
1.42
1.77
1.77
0.10
0.05
0.05
0.06
All values are from one coarse
sample (Fig. 6.4), and are
expressed in ‰.
101
Fig. 6.5. Range of δ34S values in sulfides from mantle, oceanic
and continental igneous settings. The isotopic values are given in
per mil (VCDT) (Seal, 2006).
102
CHAPTER 7. DISCUSSION
Work along Autoroute 5 near Old Chelsea has revealed a very interesting and very
complicated association of Mesoproterozoic marble, carbonate-dominant dike rocks, gray
gneiss, along with dikes of syenite, granite and an ultramafic rock. Some of the syenite is
likely directly related to the subjacent Wakefield syenite, of Neoproterozoic age.
Although the exposures are recent (2009), the rock types encountered were already
known from mapping in the general area. Béland (1954) proposed that the unusual
association of pyroxenite with pink marble in the Wakefield map-area somehow
originated by replacement of the marble. This type of replacement reaction to create a
silicate rock from a carbonate is considered to be unrealistic. Cartwright & Weaver
(1993) quantified the observations of this association and proposed that the assemblages
observed in the Stephen Cross quarry in Wakefield are exoskarns caused by the
infiltration of aqueous fluids emanating from the subjacent Wakefield syenite batholith
close to the thermal peak of contact metamorphism (715–815°C). The low values of δ18O
of calcite recorded, as low as 8.6‰, suggested to them that the fluids were in isotopic
equilibrium with the syenites (δ18O in the range 8.8–10.2‰). They inferred that the
intrusion of the Wakefield syenite was
penecontemporaneous
with regional
metamorphism in the area. This interpretation runs counter to the hypothesis generally
accepted now, that the Wakefield syenite batholith is a manifestation of anorogenic
magmatism that accompanied extension in the crust after a cycle of compressional forces
and collision (Emslie 1978, McLelland et al. 2010). Thus the prograde metamorphic
minerals like forsterite and diopside recorded in the area were developed in an earlier
phase of metamorphism, possibly the Shawinigan orogeny (1190–1140 Ma: Rivers 2008,
103
Fig. 1). They likely have nothing to do with the development of an exoskarn around the
Wakefield syenite.
In light of the recent clarification of the tectonic evolution of the area, the
carbonate-dominant dike rocks exposed along the Chelsea road cut probably resulted
from a localized episode of alkali metasomatism and reheating that caused the regional
marble to be metasomatized and to melt. It is possible that the metasomatism
accompanied the cooling of the Wakefield syenite, but it also is possible that it occurred
later, after the Ottawan orogenic phase, possibly as late as 1020 m.y. (Rivers 2008), or
even after the Rigolet orogenic cycle, possibly as late as 980 m.y. Thus one
recommendation for future work is to acquire radiometric dates on the assemblages in
these crustal carbonatites and associated fenites.
The array of data points in a plot of δ18O versus δ13C presented in Chapter 6 point
to a hypothesis different from that of Cartwright & Weaver (1993). The values recorded
in the calcite of the regional marble are progressively shifted to lower values by a
combination of two processes. The most important is a shift caused by interaction of the
regional marble with an aqueous and carbonic fluid of mixed crust and mantle derivation.
Although detailed studies have not been made of the Wakefield syenite, this rock
probably contains cryptic signs of a mantle contaminant (cf. Martin 2012), as is typical of
felsic members of the AMCG association (Emslie 1978, Peck et al. 2010). Another
process, of secondary importance, is the devolatilization incurred by the marble as it
underwent granulite-grade metamorphism. The curved arrow shown in Figure 6.1 shows
the extent of the downward shift in δ18O and δ13C expected in a representative sample of
104
regional marble undergoing devolatilization during prograde metamorphism. The
importance of a mantle-derived mixed aqueous and carbonic fluid entering the deep crust
along major shear zones in a post-collisional setting in southern Madagascar and of
devolatilization in the carbonate assemblages was emphasized by Pili et al (1997)
In this thesis, the dikes of orange and pink calcite have been shown to be true
igneous rocks, because they contain phenocrysts. Furthermore, they contain textural signs
that a sulfide melt was present. Signs of alkali metasomatism accompany the
emplacement of carbonate dikes. The main metasomatic reactions affecting the gray
gneiss involve 1) the replacement of sodic plagioclase by microcline, and 2) overall
desilication of the assemblages, ending up with the generation of in situ subsolidus
generation of potassic syenite compositions. The ultimate generation of potassic felsic
rocks at the expense of the gray gneiss follows the general pattern in well-studied
examples of fenitization (Woolley 1969, Fig. 12, here reproduced as Fig. 7.1). That there
was rheomorphism of the assemblage, i.e., melting of the metasomatized rock, would
explain the occurrence of dikes of unusual potassic syenite that cut, and are cut by, the
orange calcite dikes.
The textural relationships inside mafic clots in the orange carbonate dike rocks are
interpreted in terms of an immiscibility relationship between carbonate melt and globules
of an alkali-bearing mafic melt Immiscibility relationships involving such magmas are
well documented in the literature (Veksler & Lentz 2006). Thus there is evidence of the
existence of four magmas in the area of the road cut: 1) carbonate, 2) mafic silicate, 3)
felsic silicate (rheomorphic fenite), and 4) sulfide. Magmas 2 and 3 are not considered to
105
be related and do not belong to a fractionation sequence. Clearly, more work will be
required to test the proposal of multiple and coeval anatectic melts. It is possible that the
potassic aplite and related granitic pegmatites mapped by Hogarth (1970, 2000) in the
area near Meech Lake, a few km south of the road cut, are in fact a result of the
rheomorphism of fenites developed at the expense of the gray gneiss.
Fig. 7.1. Generalized diagram to show the principal chemical
changes during fenitization, leading in this case to ultrapotassic
assemblages. These changes are expressed in terms of the system
Qz - Ne - Ks (Woolley 1969, Fig. 12). There is no evidence along
the road cut that metasomatism caused the bulk compositions to
migrate into the silica-undersaturated portion of the diagram.
As far as the array of points illustrated in Figure 6.1 is concerned, the main
mechanism illustrated during the metasomatic transformations involves solution and
redeposition of calcite, just as was illustrated by Deines & Gold (1969) in the aureole
around Mont Royal, Quebec (Fig. 6.2). The proposal made here is that the metasomatic
event or events that affected the regional marble along the Chelsea road cut involved
106
solution of calcite and redeposition of calcite containing a complement of elements in
solid solution that it did not have before, possibly La and Ce, which eventually were
expelled from the structure by exsolution. The metasomatic overprint also involved the
addition of Ba, Sr, Ti, and F to the system. Once the crustal carbonate melt had formed,
one can predict that it reacted aggressively toward the gray gneiss country rocks, by now
themselves metasomatized, and dissolved some of that material. This is how the
carbonate melt acquired the constituents to form the phenocrysts of diopside, pargasite,
phlogopite, titanite, and betafite sensu lato. In a nutshell, this scenario accounts for the
unexplained observations of Moyd (1990) and Joyce (2006), whose label, “vein-dikes”,
expresses ambivalence as to the origin of the features being described, either as
hydrothermal veins or as igneous dikes. The descriptions offered in this thesis solve the
dilemma in naming these rocks are veins or dikes. They are dikes, with prominent
phenocrysts.
Note that the array of points in Figure 6.1 does not itself prove that melting
occurred, because the array of points in Figure 6.2 is the same, and melting certainly did
not occur there. Thus Figure 6.2 demonstrates that a subsolidus solution-and-redeposition
process could explain the carbonate data. But such a process cannot work for an unaltered
oxide or silicate mineral. Cartwright & Weaver (1993, Table 3b) reported a value of
15.2‰ for diopside in a brucite-bearing marble. In a parallel study at the Parker
phlogopite mine, at Notre-Dame-du-Laus, Quebec (R.F. Martin, unpubl. data), roughly 95
km north of the thesis area, unaltered forsterite, spinel and phlogopite phenocrysts in an
orange carbonate rock have δ18O values of 15.3, 14.9 and 15.1‰, respectively. The value
for the calcite at the Parker mine is 17‰ (all ±0.1‰). These are crustal values, and they
107
are evidently primary, not affected by a subsolidus process in the case of the noncarbonate minerals. For example, the forsterite is still fresh. The conclusion seems
inescapable that there are crustal silicocarbonatites in this part of the Grenville Province.
The color of orange calcite is attributed to an orange pigment concentrated along
cleavages planes in the calcite. It could well be bastnäsite-(Ce) or hydroxylbastnäsite(Ce), because coarse crystals of this mineral are deep orange in color. Furthermore, the
orange calcite is relatively enriched in the light rare-earth elements. The pink calcite
contains exsolution-induced domains of ferroan dolomite, which likely is a pinkish
mineral. The pink coloration is probably a reflection of this pigment, or possibly an
oxidized equivalent. On the other hand, no progress was made on the question of the
origin of the blue color in calcite. The hypothesis of Calderon et al. (1983), that radiation
damage is the cause, does not seem applicable in this case because the blue marble is
strikingly free of micro-inclusions of particles that appeared as a result of metasomatism,
by exsolution or other processes. The levels of U and Th are low and do not seem
sufficient to cause damage.
Is it reasonable to propose that carbonate rocks of sedimentary origin can melt in
the deep crust? Lentz (1999) has provided clear evidence that at the pressures and
temperatures indicated by classical geothermobarometry to the west (Kretz 1959, Kretz &
Garrett 1980) and to the east (Peck et al. 2005), there is no doubt that melting of calcite is
a viable process. In an environment rich in H2O, Lentz (1999, Fig. 3, reproduced here as
Fig. 7.2) showed the melting of the assemblage portlandite + periclase + calcite + V to
liquid can be expected at close 650°C at 400 MPa. The solidus at 800 MPa will not differ
108
significantly. In fact, the melting temperature can be expected to be lowered by the
addition of other components, like calcium phosphate, calcium sulfate, and calcium
fluoride. Figure 7.2B shows that the temperature of melting of the assemblage periclase +
calcite + V is very sensitive to the ratio CO2/(H2O + CO2); the poorer the fluid phase in
H2O, the greater the temperature of melting of the assemblage will be.
Fig. 7.2. A. Pressure vs. temperature diagram illustrating decarbonation
reactions A, B, and C, and, more importantly in this context, the melting
curves Portlandite + Periclase + Calcite + V = L and the vapor-saturated
granite solidus. B. An isobaric plot of T (°C) vs. X (CO2) at 100 MPa
illustrating the dependence of melting temperature on X (CO2). This figure
is taken from Lentz (1999).
.
The presence of a melt clearly requires the presence of a mixed H2O + CO2 gas phase.
The viscosity of a carbonate melt is expected to be very low, comparable to the viscosity
of water (Treiman & Schedl 1983). Of course, if the melt is a silicocarbonatite owing to
digestion of silicate country-rocks, the viscosity will be greater, possibly like that of a
109
syrup. In their descriptions of classic “vein-dikes” in the Grenville Province of Ontario,
Moyd (1990) and Joyce (2006) emphasized the existence of “suspended” crystals,
completely surrounded by calcite. The same feature was illustrated in Chapter 5, where
evidence of a “flow differentiation” was presented. It is clear that once the silicocarbonate
magma formed, it crystallized rapidly. In spite of this rapid crystallization, a euhedral
morphology of silicate crystals is the norm. In view of the inferred depth of crystallization
of these assemblages, equivalent to 700 or 800 MPa, rapid crystallization did not occur by
a thermal quench, but rather by a “vapor pressure” quench, owing to the formation of
bubbles upon crystallization of any anhydrous or non-carbonate phase, and the rapid
escape of the gaseous constituents.
In their report on the road cut, Belley et al. (2010) were impressed with the
occurrence of molybdenite and schorl in certain cross-cutting bodies of calcite. Fourestier
(2008) also documented molybdenite, but in dikes of graphic granite found along the road
cut described here. The association of molybdenite with both intrusive carbonate and
felsic rocks, and the juxtaposition of carbonate and felsic silicate melts in the thesis area,
recall the presence of important molybdenite mineralization to the west of the thesis area,
at the Moss mine, north of Quyon, Quebec (Lentz & Creaser 2005), located roughly 40
km west of the road cut. A Re–Os model age of 1053 ± 4 Ma was acquired for the
molybdenite in a pegmatitic veinlet cut by a calcite vein. The host anorogenic granite cuts
the Onslow syenite. The Wakefield syenite also could be of the same age, associated with
anatexis at a stage of relaxation after an orogenic pulse of the Ottawa orogeny. However,
the possibility also exists for anatexis at a younger age. Kennedy et al. (2010) have shown
that at the Yates mine, Otter Lake, Quebec, there were two distinct episodes of formation
110
of crustal silicocarbonatite. One occurred at roughly 1015 Ma and another at 998 Ma (U–
Pb dates acquired on titanite). These findings emphasize the need to carefully document
the ages of emplacement of the crustal silicocarbonate (CSC: cf. Morteani et al. 2013),
the A-type granite, pegmatite, aplite, syenite and rheomorphic fenite encountered in this
portion of the Central Metasedimentary Belt.
111
CHAPTER 8. CONCLUSIONS AND SUGGESTIONS
FOR FUTURE WORK
Three broad questions were raised as objectives in this investigation of the
carbonate-bearing rocks along the Chelsea road cut: 1) what is the mineralogy of the
regional white marble and the multicolored calcite-bearing rocks? 2) What are the
geochemical and isotopic attributes of the calcite? 3) What petrogenetic information can
be extracted from these data? Many aspects of these questions were answered, but as
usual, more questions have arisen.
The quartzofeldspathic and carbonate rocks exposed along the road cut were
regionally metamorphosed as a result of repeated cycles of subduction and collision that
have affected the southeastern margin of Laurentia. In their writings, Ralph Kretz and
William Peck, working to the west and east of the thesis area, respectively, have
documented a pressure of close to 7 kbar (25 km) and a minimum temperature of 700°C.
McLelland et al. (2010, Fig. 5) have shown that the periods of compression began
roughly 1280 million years ago in this area; each was followed by a stage of gravitational
collapse and delamination, which caused the area to be affected by an influx of fluids and
heat associated with a diapiric uprise of an asthenospheric mantle. The coarser grain-size
and mild state of deformation of the orange, pink and blue calcite-dominant rocks,
compared to the regional marble, are consistent with a hypothesis that the melting of the
marble coincided with such a late influx of heat and fluid from the mantle. Whether the
melting took place at the end of the Ottawan cycle, at approximately 1020 m.y., or the
112
Rigolet cycle, at approximately 980 m.y., or both, remains an open question and awaits
radiometric dating of the metasomatic assemblages.
Another unknown at this point is the timing of emplacement of the Wakefield
syenite. The date of emplacement of two bodies of carbonatite in the vicinity, 1026 and
1028 m.y. (could these be examples of crustal silicocarbonatite?) was mentioned in
Chapter 3. Could the emplacement of a syenite batholith be coeval with these
manifestations of carbonatite magmatism? Note that mantle-derived carbonatites are not
known to be associated with the emplacement of AMCG (anorthosite – mangerite –
charnockite – granite) complexes. This may be an argument in favor of a strictly crustal
generation of small batches of carbonatitic magma.
The rising wave of hot fluid of “mixed” crust + mantle origin caused localized
metasomatism of the regionally developed marble. This step introduced Na, K, Ba, Sr,
REE, U, Th, Nb, and Ti into the marble, and was followed by its localized melting. Signs
of rheomorphism of K-metasomatized gray gneiss, leading to syenitic and granitic
anatectic melts, were discovered along this road cut; rheomorphism of fenite represents a
new complication in efforts to unravel the processes at work in the Grenvillian crust
(Martin & Sinai, 2012).
The following discoveries were made:
1) The coarse orange to pink carbonate exposed as dike rocks are of igneous origin.
Although wollastonite was noted along the road cut, these are not skarn rocks.
113
2) Carbonatitic magmas of crustal derivation do occur in the Grenville Province, as
do rheomorphic fenites of syenitic and granitic composition.
3) The orange to pink calcite-dominant dike rocks contains phenocrysts of pargasite,
phlogopite. titanite and betafite sensu lato. The rocks are best described as
silicocarbonatite.
4) The orange color of calcite is attributed to an orange pigment located along
cleavage planes in the calcite. The pigment may be bastnäsite-(Ce) or
hydroxylbastnäsite-(Ce), the rare earths possibly exsolved from the hightemperature calcite. This is a conjecture rather than a firm finding.
5) The pink color of calcite is tentatively attributed to exsolution lamellae of ferroan
dolomite. The regional marble was first strongly depleted in dolomite during the
episodes of prograde metamorphism. Once melted, batches of carbonate melt
acquired minor amounts of Mg by assimilation (dissolution) of the fenitized gray
gneiss. The high-temperature calcite then exsolved blebs of dolomite, which are
ferroan, and thus likely pinkish.
6) The origin of the blue color in calcite is likely not due to radiation.
7) There is evidence of the presence of a sulfide melt in addition to immiscible blobs
of mafic silicate melt in carbonate melt, and of batches of rheomorphic felsic
silicate melt.
8) The subjacent Wakefield syenite pluton, inferred to be of crustal origin, probably
played a role as a source of some of the constituents added during metasomatism.
114
9) The mantle component of the aqueous fluid that caused progressive depletion in
the ratios δ18O and δ13C in the direction of typical mantle values is inferred to
have been the source of the HFSE added to the marble.
As for the future, more analyses of calcite of various colors will be required to
establish the typical levels of concentration of trace elements structurally bound in the
calcite, occluded as exsolution-induced micro-particles, or included as foreign particles
at the time of growth. These analyses will be done by laser-ablation – inductively coupled
plasma – mass spectrometry (LA–ICP–MS). In addition, oxygen isotope analyses of
silicates, phosphates, sulfate and oxide minerals will be required to test the hypothesis
that these also contain a mixture of crustal and mantle oxygen, as has been found in other
localities of crustal silicocarbonatite. The phenomenon of melting of marble is considered
to be of regional importance in the Grenville Province, and likely is the main process at
work in the “skarns” of Shaw et al. (1963).
115
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123
APPENDIX I. LIST OF SAMPLES, THEIR COORDINATES, AND THE
TYPE OF ANALYSIS CARRIED OUT
COORDINATES
DESCRIPTION
TYPE OF
ANALYSIS
FS1
N 45° 35' 23.4" W 75° 53' 40.5"
Orange Marble
EMPA,XRF
ICP-MS
FS2
N 45° 34' 7.72" W 75° 53' 17.9"
Pink Marble
EMPA, XRF
ICP-MS
FS3
N 45° 34' 7.72" W 75° 53' 17.9"
Pink Marble
EMPA
FS4
N 45° 34.8' 53" W 75° 53' 23.4"
Blue Marble
EMPA, XRF
ICP-MS
FS5
N 45° 35' 23.4" W 75° 53' 40.5"
Orange Marble
EMPA
FAH 100
N/A
Pale pink marble with
coarse pargasite
EMPA
FAH 101
N/A
Pale pink to orange
marble with pargasite
EMPA
FAH 102
N/A
Yellow-pale orange
marble
EMPA
FAH 103
N/A
Pale pink marble with
coarse diopside
EMPA
FAH 104
N/A
"Leopard" rock with
scapolite in pyroxenite
EDS
FAH 105
N/A
Pale pink marble with
coarse diopside
EMPA
NAME
124
FAH 106
N/A
Orange marble with
coarse phlogopite
EMPA,SEM
FAH 108
N 45° 35' 22.5" W 75° 53' 39.9"
Gray syenite dike
in pink marble
EMPA
FAH 109
N/A
Coarse phlogopite in
gray-pink marble
EMPA,SEM
FAH 111
N/A
Pink marble with coarse
diopside and pargasite
EMPA
FAH122
N 45° 34' 43" W 75° 52' 45"
Pink syenite in contact
with orange marble
EDS
FAH127
N 45° 35' 22.3" W 75° 53' 40"
Wollastonite lens in
marble, diopside and
amphibole
EDS
FAH132
N45° 35.1' 20" W75° 53.3' 33"
White marble with green
grain of serpentine
EDS
FAH138
N 45° 34' 8.54" W 75° 53' 23.6"
Pink syenite
EDS
FAH140
N 45° 35' 29" W 75° 52' 47.6"
Gneiss, fenite and
orange marble
EDS
FAH143
N45° 35' 002" W75° 53' 27.3"
White regional marble
with black bands of
amphibole and graphite
EDS
FAH 150
N45° 35' 14.7" W75° 53' 36.9"
Mafic rock contains
amphibole and scapolite
EDS
Note: for the sake of convenience, the term “marble” is applied loosely in these
appendices to include carbonate-dominant dike rocks.
125
APPENDIX II.A. PINK MARBLE: ELECTRON-MICROPROBE
DATA
(First in wt. %, then recalculated in apfu)
MgO
MnO
CaO
FeO
NiO
CO2
SO3
CoO
SrO
Total
FS3-C1-1
1.62
0.08
54.57
0.16
0.05
43.25
0.00
0.00
0.26
100.00
FS3-C1-2
0.44
0.06
56.06
0.09
0.05
43.10
0.01
0.00
0.19
100.00
FS3-C1-3
1.61
0.08
54.87
0.17
0.00
43.03
0.00
0.00
0.25
100.00
FS3-C1-4
0.61
0.06
56.60
0.09
0.06
42.48
0.00
0.00
0.11
100.00
FS3-C2-1
0.79
0.07
55.60
0.07
0.08
43.18
0.01
0.01
0.19
100.00
FS3-C2-2
0.05
0.03
56.48
0.02
0.06
43.32
0.00
0.01
0.03
100.00
FS3-C2-3
0.25
0.06
56.26
0.02
0.00
43.31
0.03
0.00
0.07
100.00
FS3-C2-4
2.01
4.01
47.16
1.75
0.00
45.01
0.00
0.00
0.06
100.00
Average
0.92
0.55
54.70
0.30
0.04
43.34
0.01
0.00
0.14
100.00
FS2-C2-1
0.07
0.06
56.08
0.02
0.04
43.71
0.00
0.00
0.02
100.00
FS2-C4-1
0.16
0.08
53.70
0.10
0.07
45.81
0.01
0.02
0.06
100.00
FS2-C4-3
0.12
0.07
54.92
0.04
0.05
44.80
0.00
0.00
0.00
100.00
Average
0.12
0.07
54.90
0.05
0.05
44.77
0.00
0.01
0.03
100.00
C-8(3)-1
0.03
0.35
54.96
0.05
0.00
44.59
0.00
0.00
0.02
100.00
C-8(3)-2
0.03
0.40
54.65
0.06
0.00
44.85
0.01
0.00
0.01
100.00
C-8(3)-3
0.03
0.44
54.70
0.03
0.00
44.79
0.00
0.01
0.00
100.00
C-8(3)-4
0.02
0.41
54.35
0.05
0.00
45.14
0.00
0.01
0.02
100.00
C-8(3)-5
0.01
0.17
55.39
0.03
0.02
44.38
0.00
0.00
0.00
100.00
Average
0.02
0.35
54.81
0.04
0.00
44.75
0.00
0.01
0.01
100.00
Name
Mg
Mn
Ca
Fe
Ni
C
S
Co
Sr
Total
FS3-C1-1
0.04
0.00
0.98
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS3-C1-2
0.01
0.00
1.01
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS3-C1-3
0.04
0.00
0.99
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS3-C1-4
0.02
0.00
1.02
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS3-C2-1
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS3-C2-2
0.00
0.00
1.01
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS3-C2-3
0.01
0.00
1.01
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS3-C2-4
0.05
0.06
0.84
0.02
0.00
1.02
0.00
0.00
0.00
1.98
Average
0.02
0.01
0.98
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS2-C1-1
0.00
0.00
0.98
0.00
0.00
1.01
0.00
0.00
0.00
1.99
126
FS2-C2-1
0.00
0.00
1.00
0.00
0.00
1.00
0.00
0.00
0.00
2.00
FS2-C4-1
0.00
0.00
0.94
0.00
0.00
1.02
0.00
0.00
0.00
1.98
FS2-C4-3
0.00
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
Average
0.00
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-8(3)-1
0.00
0.00
0.98
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-8(3)-2
0.00
0.01
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-8(3)-3
0.00
0.01
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-8(3)-4
0.00
0.01
0.96
0.00
0.00
1.02
0.00
0.00
0.00
1.98
C-8(3)-5
0.00
0.00
0.99
0.00
0.00
1.01
0.00
0.00
0.00
1.99
Average
0.00
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
127
APPENDIX II.B. ORANGE MARBLE: ELECTRON-MICROPROBE
DATA
(First in wt. %, then recalculated in apfu)
Name
FS1-C1-1
MgO
0.84
MnO
0.07
CaO
56.12
FeO
0.24
NiO
0.05
CO2
42.38
SO3
0.00
CoO
0.00
SrO
0.30
Total
100.00
FS1-C1-2
0.76
0.09
55.17
0.20
0.02
43.48
0.03
0.00
0.26
100.00
FS1-C1-3
0.81
0.09
55.66
0.21
0.02
42.90
0.03
0.00
0.29
100.00
FS1-C1-4
0.88
0.08
55.84
0.23
0.04
42.65
0.00
0.01
0.27
100.00
FS1-C1-5
0.85
0.07
54.90
0.23
0.04
43.60
0.00
0.00
0.31
100.00
FS1-C1-6
0.84
0.07
55.62
0.23
0.06
42.90
0.02
0.00
0.26
100.00
FS1-C2-1
0.72
0.09
55.27
0.22
0.06
43.35
0.03
0.00
0.26
100.00
FS1-C2-2
0.61
0.07
55.61
0.11
0.01
43.33
0.00
0.00
0.25
100.00
FS1-C2-3
0.71
0.09
56.30
0.19
0.05
42.34
0.03
0.01
0.27
100.00
FS1-C2-4
0.73
0.08
55.80
0.19
0.04
42.94
0.00
0.00
0.23
100.00
FS1-C2-5
0.71
0.09
56.03
0.19
0.04
42.62
0.01
0.00
0.31
100.00
FS1-C2-6
0.72
0.11
55.73
0.20
0.04
42.96
0.02
0.00
0.22
100.00
FS1-C3-1
0.82
0.10
55.48
0.18
0.03
43.08
0.01
0.00
0.31
100.00
FS1-C3-2
0.83
0.10
56.22
0.19
0.03
42.30
0.01
0.00
0.32
100.00
FS1-C3-3
0.91
0.09
54.91
0.13
0.07
43.70
0.00
0.00
0.20
100.00
FS1-C3-4
0.79
0.08
55.63
0.19
0.04
42.99
0.00
0.01
0.28
100.00
Avarage
0.78
0.09
55.64
0.20
0.04
42.97
0.01
0.00
0.27
100.00
FS5-C1-1
0.09
0.08
54.90
0.00
0.00
44.85
0.02
0.01
0.06
100.00
FS5-C1-2
0.07
0.06
54.46
0.02
0.05
45.32
0.00
0.01
0.02
100.00
FS5-C1-3
0.32
0.14
54.25
0.18
0.02
44.95
0.01
0.01
0.11
100.00
FS5-C1-4
0.39
0.16
54.59
0.25
0.12
44.33
0.03
0.00
0.13
100.00
Avarage
0.22
0.11
54.55
0.12
0.05
44.86
0.02
0.00
0.08
100.00
6-7-5-1
0.40
0.14
52.88
0.30
0.00
45.77
0.03
0.00
0.46
100.00
6-7-5-2
0.43
0.12
53.61
0.28
0.00
45.11
0.00
0.00
0.45
100.00
6-7-5-3
0.43
0.12
53.00
0.28
0.00
45.72
0.00
0.00
0.46
100.00
6-7-5-4
0.39
0.13
53.86
0.27
0.00
44.87
0.03
0.00
0.46
100.00
6-7-5-5
0.42
0.13
53.72
0.30
0.01
44.96
0.01
0.00
0.46
100.00
Avarage
0.41
0.13
53.41
0.29
0.00
45.29
0.01
0.00
0.46
100.00
C-10-4-1
0.00
0.24
54.91
0.02
0.00
44.79
0.03
0.01
0.01
100.00
C-10-4-2
0.04
0.70
53.75
0.05
0.00
45.43
0.02
0.01
0.01
100.00
128
C-10-4-3
0.00
0.01
56.04
0.00
0.00
43.86
0.04
0.00
0.05
100.00
C-10-4-4
0.00
0.31
54.93
0.03
0.01
44.61
0.03
0.02
0.07
100.00
C-10-4-5
0.01
0.30
55.47
0.02
0.01
44.16
0.00
0.02
0.01
100.00
Avarage
0.01
0.31
55.02
0.02
0.00
44.57
0.02
0.01
0.03
100.00
C-2-1
0.75
0.32
53.83
0.31
0.00
44.25
0.00
0.00
0.54
100.00
C-2-2
0.82
0.33
53.48
0.33
0.00
44.53
0.03
0.00
0.48
100.00
C-2-3
0.00
0.14
56.36
0.01
0.00
43.47
0.01
0.01
0.00
100.00
C-2-4
0.00
0.01
56.54
0.01
0.00
43.44
0.00
0.01
0.00
100.00
C-2-5
0.10
0.16
55.66
0.00
0.00
44.02
0.01
0.00
0.05
100.00
Avarage
0.48
0.14
55.00
0.16
0.02
43.94
0.01
0.00
0.23
100.00
Mn
Ca
Fe
Ni
C
S
Sr
Total
Name
Mg
Co
FS1-C1-1
0.02
0.00
1.02
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS1-C1-2
0.02
0.00
0.99
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS1-C1-3
0.02
0.00
1.00
0.00
0.00
0.98
0.00
0.00
0.00
2.01
FS1-C1-4
0.02
0.00
1.01
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS1-C1-5
0.02
0.00
0.98
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS1-C1-6
0.02
0.00
1.00
0.00
0.00
0.98
0.00
0.00
0.00
2.01
FS1-C2-1
0.02
0.00
0.99
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS1-C2-2
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS1-C2-3
0.02
0.00
1.02
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS1-C2-4
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS1-C2-5
0.02
0.00
1.01
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS1-C2-6
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS1-C3-1
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS1-C3-2
0.02
0.00
1.02
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS1-C3-3
0.02
0.00
0.98
0.00
0.00
1.00
0.00
0.00
0.00
2.00
FS1-C3-4
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
Avarage
0.02
0.00
1.00
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS5-C1-1
0.00
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
FS5-C1-2
0.00
0.00
0.96
0.00
0.00
1.02
0.00
0.00
0.00
1.98
FS5-C1-3
0.01
0.00
0.96
0.00
0.00
1.01
0.00
0.00
0.00
1.99
FS5-C1-4
0.01
0.00
0.97
0.00
0.00
1.00
0.00
0.00
0.00
1.99
Avarage
0.01
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
6-7-5-1
0.01
0.00
0.93
0.00
0.00
1.02
0.00
0.00
0.00
1.97
129
6-7-5-2
0.01
0.00
0.95
0.00
0.00
1.02
0.00
0.00
0.00
1.98
6-7-5-3
0.01
0.00
0.93
0.00
0.00
1.02
0.00
0.00
0.00
1.98
6-7-5-4
0.01
0.00
0.95
0.00
0.00
1.01
0.00
0.00
0.00
1.99
6-7-5-5
0.01
0.00
0.95
0.00
0.00
1.01
0.00
0.00
0.00
1.99
Avarage
0.01
0.00
0.94
0.00
0.00
1.02
0.00
0.00
0.00
1.98
C-10-4-1
0.00
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-10-4-2
0.00
0.01
0.95
0.00
0.00
1.02
0.00
0.00
0.00
1.98
C-10-4-3
0.00
0.00
1.00
0.00
0.00
1.00
0.00
0.00
0.00
2.00
C-10-4-4
0.00
0.00
0.98
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-10-4-5
0.00
0.00
0.99
0.00
0.00
1.00
0.00
0.00
0.00
2.00
Avarage
0.00
0.00
0.98
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-2-1
0.02
0.00
0.96
0.00
0.00
1.00
0.00
0.00
0.01
2.00
C-2-2
0.02
0.00
0.95
0.00
0.00
1.01
0.00
0.00
0.00
1.99
C-2-3
0.00
0.00
1.01
0.00
0.00
0.99
0.00
0.00
0.00
2.01
C-2-4
0.00
0.00
1.01
0.00
0.00
0.99
0.00
0.00
0.00
2.01
C-2-5
0.00
0.00
0.99
0.00
0.00
1.00
0.00
0.00
0.00
2.00
Avarage
0.01
0.00
0.99
0.00
0.00
1.00
0.00
0.00
0.00
2.00
130
APPENDIX II.C. BLUE MARBLE: ELECTRON-MICROPROBE DATA
(First in wt. %, then recalculated in apfu)
Name
MgO
MnO
CaO
FeO
NiO
CO2
SO3
6-7-1-1
0.11
0.02
56.26
0.01
0.00
43.52
0.02
6-7-1-2
0.10
0.02
56.05
0.00
0.01
43.78
6-7-1-3
0.10
0.00
56.57
0.01
0.00
6-7-1-4
0.10
0.00
55.49
0.01
6-7-1-5
0.10
0.02
56.40
Avarage
0.10
0.01
FS4-C1-1
0.01
FS4-C1-2
SrO
Total
0.02
0.05
100.00
0.02
0.00
0.03
100.00
43.29
0.01
0.01
0.01
100.00
0.00
44.36
0.02
0.01
0.01
100.00
0.01
0.00
43.44
0.01
0.00
0.03
100.00
56.15
0.01
0.00
43.68
0.02
0.01
0.02
100.00
0.01
57.15
0.01
0.10
42.70
0.01
0.00
0.02
100.00
0.00
0.00
56.74
0.00
0.05
43.17
0.01
0.00
0.02
100.00
FS4-C2-1
0.01
0.02
56.88
0.01
0.08
42.96
0.02
0.00
0.03
100.00
FS4-C2-2
0.01
0.01
56.72
0.00
0.07
43.13
0.02
0.03
0.01
100.00
Avarage
0.01
0.01
56.87
0.00
0.08
42.99
0.02
0.01
0.02
100.00
FS4b-C1-2
0.00
0.02
54.39
0.00
0.02
45.54
0.02
0.00
0.02
100.00
FS4b-C1-3
0.00
0.00
55.00
0.00
0.04
44.93
0.00
0.03
0.00
100.00
FS4b-C2-1
0.00
0.02
55.15
0.00
0.10
44.73
0.01
0.00
0.00
100.00
FS4b-C2-2
0.00
0.01
55.24
0.00
0.12
44.61
0.00
0.00
0.03
100.00
Avarage
0.00
0.01
54.95
0.00
0.07
44.95
0.01
0.01
0.01
100.00
C-6-4-1
1.62
0.02
54.19
0.00
0.00
44.13
0.01
0.00
0.03
100.00
C-6-4-2
1.62
0.00
54.34
0.00
0.01
43.97
0.01
0.00
0.06
100.00
C-6-4-3
1.63
0.01
54.35
0.00
0.00
43.98
0.00
0.00
0.02
100.00
C-6-4-4
1.61
0.02
54.17
0.00
0.01
44.14
0.02
0.00
0.03
100.00
C-6-4-5
1.65
0.01
54.26
0.00
0.01
44.02
0.01
0.00
0.03
100.00
Avarage
1.62
0.01
54.26
0.00
0.01
44.05
0.01
0.00
0.04
100.00
Name
Mg
Mn
Ca
Fe
Ni
C
Co
Sr
Total
6-7-1-3
0.00
0.00
1.02
0.00
0.00
0.99
0.00
0.00
0.00
2.01
6-7-1-4
0.00
0.00
0.99
0.00
0.00
1.01
0.00
0.00
0.00
1.99
6-7-1-5
0.00
0.00
1.01
0.00
0.00
0.99
0.00
0.00
0.00
2.01
Avarage
0.00
0.00
1.00
0.00
0.00
1.00
0.00
0.00
0.00
2.00
FS4-C1-1
0.00
0.00
1.03
0.00
0.00
0.98
0.00
0.00
0.00
2.02
FS4-C1-2
0.00
0.00
1.02
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS4-C2-1
0.00
0.00
1.02
0.00
0.00
0.99
0.00
0.00
0.00
2.01
131
S
CoO
FS4-C2-2
0.00
0.00
1.02
0.00
0.00
0.99
0.00
0.00
0.00
2.01
Avarage
0.00
0.00
1.02
0.00
0.00
0.99
0.00
0.00
0.00
2.01
FS4b-C1-1
0.44
0.00
0.37
0.01
0.00
1.09
0.00
0.00
0.00
1.91
FS4b-C1-2
0.00
0.00
0.96
0.00
0.00
1.02
0.00
0.00
0.00
1.98
FS4b-C1-3
0.00
0.00
0.97
0.00
0.00
1.01
0.00
0.00
0.00
1.99
FS4b-C2-1
0.00
0.00
0.98
0.00
0.00
1.01
0.00
0.00
0.00
1.99
FS4b-C2-2
0.00
0.00
0.98
0.00
0.00
1.01
0.00
0.00
0.00
1.99
Avarage
0.09
0.00
0.85
0.00
0.00
1.03
0.00
0.00
0.00
1.97
C-6-4-1
0.04
0.00
0.96
0.00
0.00
1.00
0.00
0.00
0.00
2.00
C-6-4-2
0.04
0.00
0.97
0.00
0.00
1.00
0.00
0.00
0.00
2.00
C-6-4-3
0.04
0.00
0.97
0.00
0.00
1.00
0.00
0.00
0.00
2.00
C-6-4-4
0.04
0.00
0.96
0.00
0.00
1.00
0.00
0.00
0.00
2.00
C-6-4-5
0.04
0.00
0.96
0.00
0.00
1.00
0.00
0.00
0.00
2.00
Avarage
0.04
0.00
0.96
0.00
0.00
1.00
0.00
0.00
0.00
2.00
132
APPENDIX II.D. WHITE MARBLE (REGIONAL): ELECTRONMICROPROBE DATA
(First in wt.%, then recalculated in apfu)
Name
MgO
MnO
CaO
FeO
NiO
CO2
SO3
6-7-3-1
0.23
0.03
55.87
0.02
0.00
43.73
0.02
6-7-3-2
0.24
0.02
55.94
0.03
0.00
43.68
6-7-3-3
0.24
0.00
56.39
0.02
0.00
6-7-3-4
0.24
0.01
55.90
0.01
6-7-3-5
0.24
0.02
55.88
6-7-7-1
0.23
0.00
6-7-7-2
0.24
6-7-7-3
SrO
Total
0.02
0.10
100.00
0.01
0.00
0.10
100.00
43.25
0.00
0.00
0.10
100.00
0.00
43.73
0.02
0.00
0.08
100.00
0.01
0.00
43.76
0.00
0.01
0.10
100.00
55.55
0.02
0.00
44.18
0.00
0.00
0.01
100.00
0.01
55.34
0.01
0.00
44.37
0.01
0.00
0.03
100.00
0.23
0.01
55.35
0.01
0.00
44.39
0.00
0.00
0.02
100.00
6-7-7-4
0.23
0.02
54.69
0.01
0.00
45.04
0.01
0.00
0.01
100.00
6-7-7-5
0.22
0.00
55.10
0.02
0.00
44.61
0.01
0.00
0.03
100.00
Avarage
0.23
0.01
55.60
0.02
0.00
44.07
0.01
0.00
0.06
100.00
Name
Mg
Mn
Ca
Fe
Ni
C
S
Co
Sr
Total
6-7-3-1
0.006
0.000
0.999
0.000
0.000
0.996
0.000
0.000
0.001
2.003
6-7-3-2
0.006
0.000
1.001
0.000
0.000
0.996
0.000
0.000
0.001
2.004
6-7-3-3
0.006
0.000
1.013
0.000
0.000
0.990
0.000
0.000
0.001
2.010
6-7-3-4
0.006
0.000
1.000
0.000
0.000
0.996
0.000
0.000
0.001
2.003
6-7-3-5
0.006
0.000
0.999
0.000
0.000
0.997
0.000
0.000
0.001
2.003
6-7-7-1
0.006
0.000
0.989
0.000
0.000
1.002
0.000
0.000
0.000
1.998
6-7-7-2
0.006
0.000
0.984
0.000
0.000
1.005
0.000
0.000
0.000
1.995
6-7-7-3
0.006
0.000
0.984
0.000
0.000
1.005
0.000
0.000
0.000
1.995
6-7-7-4
0.006
0.000
0.966
0.000
0.000
1.014
0.000
0.000
0.000
1.986
6-7-7-5
0.005
0.000
0.977
0.000
0.000
1.008
0.000
0.000
0.000
1.992
Avarage
0.01
0.00
0.99
0.00
0.00
1.00
0.00
0.00
0.00
2.00
133
CoO