REPORT No. 30
Geology and Mineral Deposits
of the
Hanson Lake Area,
Saskatchewan
by
A. R. BYERS
1957
DEPARTMENT OF MINERAL RESOURCES
Metallic & Industrial Minerals Branch
Geology Division
HON . J . H . BROCKELBANK
J , T . CAWLEY
MINISTER
DEPUTY MINISTER
$1.00
PROVINCE OF SASKATCHEWAN
$1.00
CONTENTS
INTRODUCTION
Location and Access ................. ........................ .......................... .
Physiography ....... .. ..... ....... .... .. ....... ... ................. .. .. ..... .... ... ........
1
Flora and Fauna ...... .... ........ ............... .......... .......... ...................
2
Field Work .... ....... ................................... .... ..................... .... .......
2
Personnel and Acknowledgments ...................... ..... ...... ..... ......
2
Previous W ork ............. ......... ....... ...... ........ ........... ............ ..........
3
References ....................................................................................
3
GENERAL GEOLOGY . . ...... .... .. ... ..... .. ... .. . ....... ... ... ... ..... .... ... ... ..... ... .... .
3
General Statement ............. ......... ............ .... .......... ............... .. .....
3
T able of Formations ......................................... ............ .............
4
Amisk Group ............. .. .. ... .. ... .................. .. ..... ................... .......... .
5
General Statemen t .. ........................ ... ........................... ......
5
Volcanic Rocks ( 1) .......... ... ............... ................................
5
Clastic Sediments (2) ........... ................................. .......... .
7
Cale-silicate and Pyroclastic Rocks (3) .... ........................... ... ..
9
Diopside-plagioclase rock (3a) ............ .. ..........................
9
Actinolite-biotite-diopside-garnet gneiss (3b) ... .............
10
Pyroclastic rocks (3c) ............. .......... .................................
10
Kisseynew-type gneisses ....... .......... ...................... .......... ...........
11
Biotite Gneiss ( 4) and Migmatite ( 4a) ..................... .....
11
H ornblende Gneiss (5) , Amphibolite (Sa) and
Migmatite (Sb) ............... ............................................ .. .. .
12
Intrusive Rocks ... .... ... ... .. ... ... ............... ... .................. .... .... ...........
13
Amphibolite, metadiori te, metagabbro (6) ........... ........
13
Granodiorite and Related Rocks ( 7, 7a, and 7b) ..........
14
Quartz-feldspar porphyry (8) ................................. ........
15
and derived Quartz-sericite schist (8a) ....................... .. .
15
Diorite and Related Rocks (9, and 9a to 9h) ... .............
16
Microcline Granite ( 10) .................................... ................
20
Pegmatite .. .... ................ ... .. ...................................................
21
Ordovician Dolomite and Sandstone (11 ) ................. ........ ...
22
Win'nipeg Sandstone ................ .............. .... ........................
22
Red River Dolomite ..... ........ ......... ......... ...........................
27
Pleistocene and Recent .......... ................ ...... ..............................
27
STRUCTURAL GEOLOGY ...................................... ... ....... ........ ............
Folds ........................................ ....... ............ .... .. ..... .................. ......
Faults ............. ............................................... ................................
Lineation ............................. .................................................. .. .....
Foliation ...... .... .... ............ ... ..... ........ ............. .................. ........... ....
27
27
30
31
32
33
General Statement .................................... .................................. 33
History of Prospecting Activity .................... .......... .................. 33
Description of Properties ............... ........................ ............... ...... 34
Cyprus Exploration Corporation Limited (1) ................ 34
Hudson Bay Exploration and D evelopment Company,
Limited ........................................... ........... ....... ........... .... 35
Parrex Mining Syndicate (Trust) ............... .. .............. ..... 38
Ramsay Showing (4) .......................... ................ ..... ......... 40
Wings or Blue Bird Prospect (5) ...... ................ .. ............ 43
Young Showing
43
ECONOMIC GEOLOGY ............................. ...................... ...................
ILLUSTRATIONS
Geological Map 30A, H anson Lake, Saskatchewan ............ In pocket
Plate 1 .. ................ .............................................. ......... .... ...... ...............
Figure I. Dacite, fl ow breccia. South shore Agnew Bay,
45
fu~n~b ..........................................................................
~
Figure 2. D acite, flow banding. East side of Bertram Bay,
H anson Lake ............................ .. ............................................
45
Plate 2 ...... ........ ..... ............... ....... .............. ... .................... .................... 46
Figure I. Contact betwen dacite (right) and tuff (left ).
East of Bertram Bay, H anson Lake ...................................... 46
Figure 2. Interlayed tuff and agglomerate beds. Grain
gradation indicates tops towards top of picture. East
shore Bertram Bay, H anson Lake ....... ....... ... ...................... . 46
Plate 3 ................. ......... ........................................................................ 47
Figure 1. Contact between Winnipeg sandstone and overhanging Red River dolomite. Just west of entrance to
Mcllvenna Bay, H anson Lake .............................................. 47
Figure 2. Winnipeg sandstone, illustrating its unconsolidated character. Just west of entrance to Mcllvenna Bay,
H anson Lake ....................... ............................................ ....... 47
Figure 1.
Pole diagrams of fold structures, H anson Lake area .. 29
Figure 2. Plan of diamond drill holes and vertical projection
of zones of sulphide mineralization. Mineral Showing No. 2,
Hudson Bay Exploration and Development Company, Limited 37
Figure 3. Plan of trenches and diamond drill holes with vertical
projection and depth of sulphide in tersections. Mineral Showing No. 4, Ramsay prospect .................................................. 41
INTRODUCTION
Location and Access
The area covered by this report is bounded by latitudes 54° 37' 30"
and 54° 45' 00" north and longitudes 102° 45' and 103° 00' west. The
area forms the northwest quarter of the H anson Lake topographic map
sheet, 63-L-10, on a scale of one inch to one mile. Hanson Lake is 37
miles west of Flin Flon, Manitoba, and 100 miles east-southeast of La
Ronge, Saskatchewan. Flin Flon is serviced by the Canadian National
Railways and both places are connected to the southern parts of the
province by all-weather highways and by regularly scheduled airline fligh ts.
H anson Lake is easily accessible by float-equipped a ircraft which may
be chartered at either Flin Flon or La Ronge. A more arduous and time
consuming method of travel is by canoe and outboard motor from Denare
Beach on the east shore of Amisk Lake. The route crosses Amisk Lake
then up the Sturgeon-Weir and H anson Rivers to Hanson Lake. The trip
involves two portages on the Sturgeon -Weir and fou r portages along the
H anson River. The journey from Denare Beach to Hanson Lake requires
a full day.
H anson Lake with its numerous long bays provides easy access to the
eastern two -thirds of the area. The southwestern section may be reached
by a canoe and portage route up the Bad Carrot River and through Bad
Carrot, Side, and Pasowun Lakes. A portage connects th e south end of
Pasowun Lake with Bigstone Lake to the west. The northwest part of the
area may be reached by canoe from Bigstone Lake up Tulabi Brook to
Tulabi Lake. This is rather a difficult route and float-equipped aircraft
are recommended for gaining access to Tula bi Lake.
Physiography
The H anson Lake area lies just south of the h eight of land between
th e Churchill River and Saskatchewan River drainage systems. H anson
Lake, with an elevation of approximately 1,050 feet a bove sea level, lies
immediately north of the Precambrian-Paleozoic contact which is marked
by a fairly well -defined, though deeply indented, north-facing escarpment
rising 20 to 60 feet above the country to the north.
South of the escarpment the topograph y is quite flat with very
extensive areas of muskeg and swamp. For a mile or more north of the
escarpment the local relief is very low, in the order of 10 to 20 feet, and
only a few rounded outcrops protrude through the muskegs and glacial
deposits. Farther north the topography is controlled to some extent by the
n ature of the underlying bedrock. Valleys and ridges have a gross linear
arrangement paralleling the foliation and formational trend of the bedrock.
Even in the northern section of the map-area, however, the local relief is
low with the ridges rarely rising more than 50 feet above the adjacent
flat-bottomed valleys.
Pleistocen e glacial action modified to some extent the preglacial topography by removing the covering of the soil and weathered rock from
much of the northern half of the map-area and depositing a thin mantle
of glacial drift in the southern half. Glacial striae and grooves as well as
a few small drumlins south of H anson Lake show that the movement of
the glacial ice was from north to south.
-
1-
At several points about Hanson Lake elevated shoreline deposits occur
at 10 and 30 feet above the present level of the lake. These deposits were
probably formed during or shortly after the withdrawal of the Pleistocene
ice sheet when the level of the lake must have been higher than it is today.
Flora and Fauna
The area is well wooded except for the extensive areas of swamp south
and southwest of H anson Lake. Spruce is abundant and widely distributed.
Other common trees are balsam in the low-lying areas, jackpine in areas
underlain by the basal Paleozoic sands, and birch and poplar on hills and
ridges underlain generally by till. A forest fire in the spring of 1954
destroyed much of the forest cover in the area between Bad Carrot River
and Mcllvenna Bay.
Northern pike are found in all the lakes and pickerel are also widely
distributed. White fish are abundant in H anson Lake and a limited
amount of commercial fishing has been done.
Game and fur-bearing animals are abundant especially beaver, muskrat, moose and bear.
Field Work
The field work was carried out during the summer of 1954. Aerial
photographs on a scale of 1 inch to 1,320 feet were used and geological
data plotted on Kodatrace overlays and later transferred to a quarter-mile
base map. Generally traverse spacing varied from quarter-mile to half-mile
intervals, but in areas which appeared to be of economic interest all the
larger outcrops were examined.
The geological map accompanying this report shows about 60 per
cent of the structural data as plotted on the original field map. Omissions
have been made where several symbols repeated the same information. No
anomalous observations have been omitted.
Aerial photographs of the area may be obtained from the National Air
Photographic Library, Topographical Survey, Ottawa. From south to north
they are numbered as follows: A9896-54 to 70, A9865-56 to 76, A9865
-77 to 95, A9895-96 to 113, A9867-2 to 20, and A9866-26 to 43. The
photographs are sharp and clear, but the scale varies slightly between
flight lines.
The area is covered by Mineral Claims Map No. 63-L-IO-NW on a
scale of one inch to one-half mile. This map may be obtained from the
Chief Mining Recorder, Department of Mineral Resources, Government
Administration Building, Regina, or from the recorders office at Flin Flon.
Personnel and Acknowledgments
The writer wishes to acknowledge the willing and able work of L. A.
Clark and W. Petruk as senior assistants, and C. N. Chernoff and Ore.st
Lesiuk who acted as junior assistants on the field party.
The Hudson Bay Exploration and Development Company Limited
through the kindness of Mr. A. A. Koffman, chief geologist, provided much
useful information and supplied camping equipment on Hanson Lake. The
writer is also indebted to Mr. A. L. Parres, consulting ~eologist, who
supplied data on the work done by Cyprus Exploration and Parrex Mining
Syndicate.
-2-
Previous Work
Reconnaissance mapping of the D eschamba ult Lake area by the Geological Survey of Canada (De Lury, 1926) included the area around
Tulabi Lake. In 1933, Wrigh t and Stockwell (1934 and 1935 ) mapped the
entire area on a scale of two miles to one inch in their study of the west
half of the Amisk Lake area. Eastwood ( 1949) when mapping the Snake
Rapids area extended his work west to include the east section of the
Hanson Lake area in order to study the sedimentary formations and basic
intrusions exposed there.
References
Budding, A. J., and Kirkland, S. J. T. ( 1956): The Geology of the Reindeer River area; Rept. No. 22, D ept. of Mineral Resources, Saskatchewan.
Byers, A. R., and Dahlstrom, C. D. A. (1954) : Geology and Mineral
D eposits of the Am isk-Wildnest Lakes area, Saskatchewan; Rept. No.
14, Dept. of Mineral Resources, Saskatchewan.
Clark, L. A. (1955) : Sulphide Deposits of the H anson Lake Area; Uni\·.
of Sask., Dept of Geo!., unpub. M.Sc. thesis.
Chernoff, C. N. (1955) : The Winnipeg Sandstone, Hanson Lake Area;
Univ. of Sask., Dept. of Geo!., unpub. B.E. thesis.
DeLury, J. E., (1926): Wapawekka and Deschambault Lake area: Saskatchewan; Geo!. Surv., Canada. Sum. Rept., 1924, pt. B, pp. 23-50
Eastwood, G. E. P. (1949): Snake Rapids, Saskatchewan; Geo!. Sur.,
Canada, Paper 49-18 (Map and Descriptive notes).
Kirkland, S. J. T . (1957): The Geology of Manawan Lake area, Saskatchewan; Rept. No. 27, Dept. of Mineral Resources, Saskatchewan.
Kupseh, W. 0 . (1953): Ordovician and Silurian Stratigraphy of East
Central Saskatchewan; Rept. No. 10, Dept. of Natural Resources,
Sask. Geo!. Survey.
Pctruk, W. (1955): Petrofabric analysis of the Amisk and Missi sediments
in the Amisk and H anson Lakes area; Univ. of Sask., Dept. of Geo!.,
unpub. M.Sc. thesis.
Wright, J. F., and Stockwell, C. H . (1934): West h alf of Amisk Lake
area, Saskatchewan; Geo!. Surv., Canada, Sum. Rept. 1933, pt. C,
pp. 12-22.
............... .............. ........................................... ( 1935): Amisk Lake, Saskatchewan; Geol. Surv., Canada, Map 314A, with descriptive notes, scale
two miles to one inch.
GENERAL GEOLOGY
General Statement
All the consolidated rocks of the H anson Lake area arc of Precambrian
age except the Paleozoic dolomite and basal sandstone. Unconsolidated
Pleistocene glacial deposits and Recent alluvium partly mask the bedrock
especially in the south half of the area.
The oldest rocks consist of apparently conformable sedimentary and
volcanic strata and their metamorphic equivalents. These have been highly
folded and intruded by two distinct sequences of igneous rocks: ( 1) an
older syntectonie sequence with a composition of granodiorite to quartz
diorite, and (2) a younger, largely post-tectonic sequence with a composition of diorite to gabbro.
-3-
Recognizable volcanic rocks underlie most of the central part of the
area. They consist of massive to fragmental lava flows with interbedded,
narrow bands of pyroclastic rocks. The average composition of the lavas
is dacite. The tuffs, being less resistant to weathering and erosion than the
lavas, usually do not outcrop but are topographically expressed as valleys.
The recognizable sedimentary rocks are structurally above the volcanic
sequence and underlie most of the main part of Hanson Lake. They consist
of greywacke with some interbedded argillite and conglomerate. Lithologi­
cally the sedimentary and volcanic strata are identical to the sequence
that underlies the area between Amisk Lake and the Sturgeon-Weir River
and which are assigned to the Amisk group.
Table of Formations
Cenozoic
Paleozoic
Precambrian
Recent and
Pleistocene
Ordovician
Till, gravel, sand, clay, peat.
Unconformity
Red River
Mottled and non-mottled
Fm. (50-60') dolomites.
Winnipeg
White to grayish orange,
Fm. (10-20') friable quartz sandstone.
Unconformity
Pegmatite and microcline
granite.
Granodiorite, quartz diorite,
diorite, gabbro, pyroxenite
and peridotite, related por­
phyritic and metamorphic
equivalents.
Amphibolite, metadiorite,
quartz porphyry, quartz­
feldspar porphyry, and
derived quartz-sericite
schist, metagabbro.
Post-tectonic
Tectonic age
uncertain
Syntectonic
Granodiorite, quartz diorite,
related porphyritic and
metamorphic equivalents.
Kisseynew-type
gneisses
Intrusive Contact
Biotite and/or hornblende
gneiss, calc-silicate gneiss,
amphibolite, and garneti­
ferous facies of these rocks.
Amisk group
Greywacke, minor amounts
of argillite, conglomerate,
locally garnetiferous and
may contain staurolite and
sillimanite.
Cale-silicate and pyroclastic
rocks, locally garnetiferous.
Dacitic lava and flow brec­
cia, pyroclastic rocks,
locally garnetiferous.
-4-
To the north and west, the volcanic and sedimentary rocks are in
contact with either gneiss or large masses of syntectonic granodiorite and
quartz diorite. For mapping purposes the gneisses have been divided into
two main groups, a biotitic series and hornblendic series. Both groups have
been derived mainly from sediments, but the hornblendic series includes
some volcanic rocks and possibly metamorphosed basic sill-like intrusions.
In the Jackpine Lake and Tulabi Lake areas the sediments which gave rise
to the gneisses are structurally lower or beneath the volcanic series and,
therefore, must be older. No evidence has been found that would indicate
an unconformity between the two series.
To the cast the sediments are cut off by a major intrusive mass of
post-tectonic dioritc and gabbro which underlies the east and southeast
parts of the area.
To the south the volcanic-sedimentary belt passes beneath the almost
flat-lying Ordovician dolomite a nd basal sandstone.
The Precambrian sedimentary and volcan ic rocks throughout the area
have been altered by regional metamorphism to a uniform metamorphic
grade corresponding to the amphibolite facies or garnet-staurolitc zone or
staurolite-kyanite subfacics. Locally the silliman ite-almanditc subfacics
has been reached.
Amisk Group
General Statement
The rocks included in this group although metamorphosed still retain
sufficient primary structures that they can be readily distinguished as being
of either sedimen tary or volcanic origin. Strictly speaking they should be
referred to as mctasedimentary and metavolcanic rocks; however, in the
following descriptions the prefix meta will be omitted. They are assigned to
the Amisk group because of their very marked lithological similarity to the
sediments and lavas as mapped in the Amisk Lake-Sturgeon-Weir River
area, 12 to 18 miles east of Hanson Lake, by Eastwood (1949) and Byers
and Dahlstrom (1954). On the Amisk Lake sheet, Map 3 14A by Wrigh t
and Stockwell, t he sediments forming the islands in the central part of
Hanson Lake are classified as Missi. However, Wright and Stockwell
(1934, p. 16c) in their report place the sediments in their Wekusko
(Amisk) group, but state th at they may belong to the Missi series. Lithologically the sediments are unlike the Missi strata, but are very similar to
the Amisk sediments on the west side of Amisk Lake. Therefore, they arc
placed in the Amisk group.
The volcanic rocks underlie most of the central part of the map-area
to the west of the main section of H anson Lake. They are conformably
overlain by the sedimentary strata which form the islands and shorelines
in and along the central part of the lake.
The volcanic and sedimentary rocks are isoclinally folded, the former
into several large folds with a plunge to the south, and the latter into
many small folds which plunge either north or south.
T he high degree of folding, lack of marker horizons, and scarcity of
outcrop make it impossible to estimate the thicknesses of the two series.
Volcanic Rocks (1)
The most prevalent and characteristic rocks of this group are massive
lavas and flow breccias of dacitic composition. Minor quantities of rhyolite,
andesite, agglomerate, tuff, and calcareous sediments occur as narrow
bands interlayered with the lavas.
5-
The dacitic lavas are very fine- to fine-grained, hard, grey to dark
grey rocks which weather to lighter shades of grey or pinkish grey. Parallel
flakes of dark biotite frequently produce paper-thin black streaks through out the rock. A porphyritic texture is common with small, one-sixteenth to
one-eighth inch, white feldspars being the most common type of phenocryst. Small one-sixteenth inch blue-grey, round, grains of quartz may also
be present, and in a few of the more basic darker coloured flows hornblende occurs as needle-like phenocrysts. Poorly developed, rounded
crystals of garnet, from one-eighth to three-quarter inch in diameter, are
frequently present and often occur in bands which are more highly foliated
than the massive or fragmental lava on either side.
Amygdules, flow banding, and flow breccia are primary structures
preserved in the flows. Amygdules are not common or, if present, have not
been recognized. They are usually filled with white quartz and have the
shape of flat ellipsoids elongated parallel to the d irection of foliation.
Original flow banding is represented by lenses and irregular bands or
streaks of various shades of grey from one-quarter inch to two inches wide
and from six to 30 inches long, see Plate I, Fig. 2. The structure is easily
distinguished on weathered surfaces where slight differences in texture and
composition have been emphasized by differential weathering. The flow
breccia is characterized by the presence of numerous angular to ellipsoidal
fragments which weather lighter in colour than the enclosing matrix, see
Plate I, Fig. 1. In a few flows the fragments are slightly darker than the
matrix. In either, however, the fragments are of the same composition as
the matrix. The fragments range in size from one-quarter inch to eigh t
inches and average about three to four inches. Only a few fragments may
be present or they may become so numerous as to form 80 per cent or more
of the rock.
Foliation and lineation are secondary structures superimposed on the
dacitic rocks. A weak foliation or schistosity is generally present and is
produced by the parallel orientation of the micaceous minerals, biotite and
sericite, and where strongly developed by the flattening of amygdules and
fragments. Lineation is marked by the elongation of amygdules, quartz
J.?henocrysts, fragments, and the smearing out of biotite.
The few rhyolitic rocks interbanded with the dacitc are much finer
grained and have a cherty texture. On fresh surfaces they are irregularly
mottled in shades of grey and pinkish-buff. The occasional basic flow is
green to dark grey-green and resembles typical andesitic grecnstonc. In a
few places a poorly developed pillow structure was observed.
Microscopically the dacitic lavas are porphyritic even though the texture may not show in the hand specimen. The phenocrysts are original or
primary, but the groundmass is completely recrystallized and possesses a
granoblastic to lepidoblastic texture. Plagioclase, quartz, and biotite are the
essential minerals. Accessories are apatite and magnetite. Hornblende may
or may not be present, other minerals that may be common locally are
sericite, microcline, chlorite, garnet, calcite, hematite, and pyrite.
The composition of the plagioclase ranges from basic oligoclase to
andesine. In the thin sections examined, the plagioclase invariably forms
phenocrysts as well as occurring in the groundmass. The phenocrysts show
albite and combined Carlsbad-albite twinning, many are euhedral but some
are broken and crushed especially around their margins. The plagioclase of
the groundmass is generally untwinned and forms subhedral to anhedral
grains. Most of the plagioclase contains dust-like particles of hematite
which give a reddish brown shade or tinge to the feldspar which is usually
somewhat saussuritized and sericitized.
-6-
Quartz may form phenocrysts and is invariably present in the groundmass where it and plagioclase form a simple mosaic texture. The quartz
phenocrysts are usually crushed and recrystallized in multi-grain units
h aving wavy to sutured intergrain boundaries. The quartz may be clear or
contain dusty inclusions, and strain sh adows are nearly always present.
Biotite occurs as small flakes scattered throughout the groundmass
generally with a parallel orientation. When sufficient biotite is presen t
the texture of the groundmass becomes lepidoblastic. In some slides the
biotite also occurs in multi-grain aggregates which may represent original
phenocrysts. The pleochroism is strong but variable in shades of brown,
green, tan, and yellow.
H ornblende, when present, may be in the form of euhedral primary
phenocrysts or secondary highly poikiloblastic, irregular grains in the
groundmass. The phenocrysts are often twinned and pleochroism is green,
yellow-green, colourless. It may be partly replaced by biotite. The pleoch roism of the poikiloblastic h ornblende is blue green to yellow-green.
Garnets have a pinkish tinge in ordinary transmitted light. They for m
very irregular poikiloblastic grains with quartz, biotite and magneti te
forming the inclusions. Many show some alteration to chlorite, particularly
along small fractures.
Sericite has three modes of occurrence: (I ) minute fl akes within
plagioclase phenocrysts; (2) irregular ragged grains interleaved with and
replacing biotite in the groundmass; a nd (3) as large post-tectonic fla kes
crossing the foliation with a h aphazard orientation.
Potash feldspar, usually microcline, when presen t occurs along intergrain boundaries between plagioclase and quartz or as anhedral grains
within the quartz-plagioclase mosaic of the groundmass.
The rocks of pyroclastic and sedimentary origin which are interbedded
with th e dacitic lavas a re described later in division 3; calc-silicate and
pyroclastic rocks.
Clastic Sediments (2)
Greywacke is the dominant rock type composing this division with
minor amounts of interbedded conglomerate, calcareous beds, argillite, and
iron formation. The sediments underlie the main section of Hanson Lake
and outcrop along the shores and on the islands in the lake. The bands of
conglomerate (2a) occur at a number of horizons within the section and
outcrop mainly in the southeast part of the la ke.
The western margin of the sedimentary belt is delineated by long,
narrow sills of porphyritic rocks, and nowhere have the sediments been
observed in direct contact with the dacitic volcanic rocks on the west.
Structurally they appear to be conforma ble w ith primary structures indicating tha t both groups face east. There is no evidence of a conglomerate at
the base of the sedimentary series. T he eastern part of the belt is intruded
and cut off by a major intrusion of diorite.
The greywacke is grey, dark grey, or black on fresh surfaces a nd
weathers to ligh ter shades of grey or brownish grey. The size of grain i~
very fine to medium. It is usually well stratified in beds from a fraction of
an inch to 30 inches thick. The interbedded ba nds of conglomerate with
the greywacke are in the order of a few tens of feet thick and consist of
light-coloured pebbles in a matrix of greywacke. The pebbles are round to
elliptical, and in the latter the long axis of the ellipse parallels the axis of
the fold. The pebbles consist of dacite and quartzite.
-
7-
Graded bedding, in spite of the recrystallization of the original constituents, is present in some beds. In recrystallized beds secondary biotite,
hornblende, and staurolite are commonly concentrated in the upper half
of the beds and, where primary grain gradation is not apparent, their
presence is an indication of the position of the upper side of the beds.
Garnets are generally irregularly distributed throughout the beds and cannot be relied upon for structural interpretation. Cross-bedding was not
observed.
A well-developed foliation or cleavage is always present. This
cleavage has a steep dip and strikes north. The relationship between bedding and cleavage (Billings1 ) proved useful in determining the attitude
of the folds and invariably corroborated the evidence obtained from
primary and secondary grain gradation.
As observed in thin sections the original constituents of the greywackc
are largely recrystallized and consist of a mosaic of quartz, oligoclaseandesine, biotite, and hornblende, and minor, variable amounts of garnet,
staurolite, andalusite, cordierite, muscovite, sillimanite ( var. fibrolite) ,
microcline, tremolite, calcite, chlorite, epidote, zoisite, magnetite, apatite,
and tourmaline.
The quartz is largely recrystallized and exhibits an undulose extinction
which is usually parallel to the optic axis. Some clear grains fill interstices
between larger grains, but the majority contain numerous minute inclusions generally as trains crossing the grains. A few large grains show relict
structures of crush quartz. Whenever several recrystallized quartz grains are
together they have sutured interlocking boundaries.
Plagioclase feldspar is a common constitutent and ranges from basic
oligoclase to andesinc. Most of the plagioclase forms anhedral, untwinned
grains that are partly altered to saussurite and sericite. The majority that
show albite twinning are small, clear, subhedral grains. A few large grains
have a poikiloblastic texture and cut across grains of quartz, mica and
feldspar.
Biotite is the prevalent mafic mineral and is later than hornblende. It
is greenish brown when associated with hornblende, elsewhere it is typically brown to straw yellow. Metamics with well-developed pleochroic
halos are invariably present and are especially pronounced in the east and
southeast parts of the belt. Most of the flakes have sharp, distinct borders,
and very few show any evidence of being warped or bent thus indicating
a post-tectonic origin. The flakes are elongated in the direction of foliation.
Garnets which are red in hand specimen are colourless to pale pink
in thin section. They occur as round poikiloblastic, anhedral to subhedral
grains containing quartz, biotite, and magnetite. Many contain fractures
perpendicular to the foliation and along which the garnets arc altered to
chlorite.
Staurolite occurs as anhedral to subhedral metacrysts generally in
biotitc-rich bands where it is closely associated with sillimanite and andalusite. Some grains contain inclusions of quartz and feldspar, and many are
partly altered to muscovite.
Sillimanite forms individual sheaf-life aggregates and also occurs as
highly acicular crystals within grains of biotite, garnet, and andalusite.
Some of the larger aggregates are partly altered to muscovite.
JBillings, M. P. (1954): "Structural Geology" (2nd ed.); Prentice-Hall, New York,
pp. 345-351.
-8-
Andalusite occurs as well-developed, euhedral crystals commonly
crossed by fractures perpendicular to the foliation. It shows replacement
by muscovite.
Cordierite was only observed in thin sections from the southeast part
of the belt. It occurs in the same bands as staurolite and is often replaced
or surrounded by muscovite.
Both the clinochlore and penninite variet ies of chlorite were observed.
The chlorite replaces biotite and garnet.
Muscovite occurs either as large metacrysts where it has replaced
staurolite, andalusite, and cordierite, or in smaller flakes which parallel
the foliation, and cut and replace biotite.
The mineral assemblage indicates both progressive and regressive
· metamorphism. The former is confirmed by the fact that garnet formed
after biotite, and the latter by chlorite replacing biotite and garnet, and
muscovite replacing staurolite, andalusite, sillimanite, and cordieritc.
Cale-Silicate and Pyroclastic Rocks (3)
This division includes altered and recrystallized sediments which at
the present time contain as their major constituents two or more of the
following minerals : actinolite, tremolite, diopside, garnet, and basic plagioclase. They form bands from a few tens to several hundreds of feet thick
which are interbedded with volcanic rocks of division 1, sediments of
division 2, and gneissic groups 4 and 5. Some within the volcanic group
retain sufficient evidence of their fragmental pyroclastic origin that they
may be referred to as tuff and agglomerate. One calc-silicate band interbedded with greywacke (2) occupies the center of the long narrow
peninsula separating Agnew Bay from the main section of Hanson Lake.
At least five mappable bands are interbedded with the dacitic volcanic
rocks and several others too narrow to be shown on the map are known
to occur in the area between Hanson and Side Lakes. At Tulabi Lake calcsilicate rocks are interbanded with biotite-garnet gneisses.
These calc-silicate and pyroclastic rocks are economically importan t
since they form the host rock for most of the known base metal prospects
in the area.
A diopside-plagioclase rock (3a) is the most common type. It is fin e
to coarse grained, well banded to quite massive, and grey green to mottled
black and white. The massive variety might easily be mistaken for gabbro
except it is softer and will effervesce when tested with dilute hydrochloric
acid. The rock also weathers with a characteristic rough, pitted surface.
Microscopically the texture is granoblastic with biotitc showing a preferred orientation parallel to the gneissic structure. Poikiloblastic meta crysts are common. The mineralogy is complex. The bulk of the rock is
composed of variable amounts of diopside, plagioclase, hornblende, calcite,
and biotite, but microcline, sphene, apatite, epidotc, zoisite, quartz, chloritc,
and talc are nearly always present.
The diopside is pale green to colourless and occurs as small grains in
a granoblastic mosaic or as large poikiloblastic metacrysts. Lamcllar twinning is common. The diopside is later than biotite and brown-green horn blende, but in turn is replaced along fractures and grain boundaries by
pale-green actinolite. Both the biotite and hornblende show some alteration to ehlorite.
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Plagioclase forms clear, unaltered, irregul ar gra ins often with albitc
twinning. It is usually andesine but two sections examined contained
anorthite. Microline when presen t is in terstitial to the other minerals, and
i·s later than the plagioclase.
Calcite may form much of th e rock or it may be absent enti rely.
Apatite and sphene are always present, the latter in amounts u p to fi ve
per cen t.
A ctinolite- biotite-diopside:gamet gneiss (3 b) occurs interbanded with
the dacitic lavas and may represent a h ighly altered tuffaceous sediment
or tuff. The rock is medium to coarse gra ined. generally dark green, and
varies from faintly gneissic to well banded. The banding may be either
regular or len ticular and h ighly con torted. In many respects it closely
resembles the diopside-plagiocl ase rock (3a) except that it con tains much .
actinolite and locally abun dant garnet. Weathered surfaces arc characteristically rough and pi tted. In most outcrops it may be seen interbedded with
a very fine- to fine-grained, grey to grey-green, siliceous-looking rock. The
dark-green actinolite-diopsi de bands are one inch to four inches thick, are
medium to coarse grained, and in places contain many large, irregularsh aped garnets. The siliceous bands are one-h alf in ch to two inches thick,
are often cherty-looking, and the only visible minerals arc biotite, sericite,
and small garnets.
Microscopically the actinolite-diopside rock h as a granoblastic texture
made up principally of actinolite and diopside, with or without garnet, and
minor quantities of plagioclase, hornblende, biotite, chlorite, calcite,
sphen e, apatite, quartz, and sulphides. T h e siliceous biotitic rock h as a
foliated mosaic or lepidoblastic texture formed by quartz, plagioclase, and
biotite, with minor amounts of hornblende, muscovite, calcite, chloritc,
apatite, staurolite, and magnetite. Ga rnet may be a major constituen t.
The actinolite is weakly pleochroic in pale sh ades of green. The
crystal h abit is euhedral elon gated prisms to irregular poikiloblastic grains
containing numerous inclusions of quartz, biotite, calcite, and feldspar. Most
of the actinolite shows no evi dence of alteration from diopsi dc and h as the
appearance of being a primary metamorphic mineral.
The garnets which are locally abundant are colourless to pale pink in
thin section. They form small subhedral crystals to large irregular highly
poikiloblas tic grains conta ining numerous inclusions of quartz. hornblende,
calcite, biotite, and magnetite. Man y are cracked and seamed by chloritc.
The plagioclase in the sections examined shows considerable variation
in the anorthite content, from andcsine to anorthite. Most of the plagioclase, h owever, is basic andesin e. It is generally fresh and u ntwinned, but
albite and pericline twins occur in some crystals.
T wo varieties of biotite were noted, a brown and a green. The brown
is the more common type and forms up to 25 per cent of the siliceous
bands. It occurs as small fl akes with parallel orientation and produces a
lepidoblastic texture. The green variety is highly pleochroic from light to
dark green. It is closely associated with garnet and frequently follows the
edges of the garnet metacrysts, thus it appears to be a residue produced
during the growth of the garnets.
Pwoclastic rocks (3c) form several mappable bands which are intcrbcdded with the dacitic lavas. The pyroclastic nature of these bands is
evident from agglomeratic beds which contain angul ar to elliptical lightcoloured dacitic fragments in a green amphibolitic matrix, see Plate 2,
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10 -
Fig. 2. The beds vary in thickness from a few inches to several feet, and
the fragments range from one-quarter inch to 10 inches but average about
two inches. Several beds showing grain gradation were noted; the fragments graded from one-half inch on one side of the beds to very finegrained material on the upper side. The agglomeratic beds are interlayered
with very fine- to fine- grained, grey to dark-grey beds which are from
one-quarter inch to several inches thick. In places the fine-grained tuif
contains metacrysts of hornblende and the rock may resemble a hornblende
porphyry. Garnets are often present in the tuffaceous beds, in the matrix
of the agglomcratic beds, and in the dacitic fragments. Bands of dacitic
tuff with agglomeratic beds arc difficult to distinguish from flows of
dacite. The elastic or fragmental texture and bedded structure can be detected only on clean weathered surfaces. Furthermore, they often contain
fragments of feldspar and quartz which are easily mistaken for phenocrysts.
These pyroclastic rocks arc mineralogically simple compared with the
calc-silicate rocks (3a) and (3b) . Under the microscope they are seen to
consist mainly of pale-green actinolite, partly saussuritized plagioclase
(andesine and labradorite) , biotite, and quartz, with minor amounts of
calcite, sericite, and magnetite. No garnets were observed in the three thin
sections examined, although they arc a common constituent in many outcrops. Calcite occurs in n arrow vcinlcts and replaces the other minerals.
The texture is granoblastic to porphyroblastic with the actinolite forming
a decussate aggregate, and, if much biotitc is present, the texture tends
to be lepidoblastic.
Kisseynew-Type Gneisses
Biotite Gneiss (4) and Migmatite (4a)
Biotite gneiss and related migmatite, both generally garnetiferous, outcrop in and around Tulabi Lake and in the northeast corner of the maparea. They occupy the axial position in south-plunging anticlinal structures
and are, therefore, structurally below the hornblendic gn eisses of group 5.
Bands of hornblende gn eiss too narrow to be shown on the map are in terlaycrcd with the biotite gneiss.
The biotite and biotitc-garnet gneisses are fine to medium grained and
consist of various amounts of feldspar, quartz, biotite, hornblende, and, in
places, garnet. The fresh surface is medium to dark grey and the rock
weathers to lighter shades of grey. Gneissic structure may be inconspicuous to very pronounced with interbanding of dark biotite-rich layers and
lighter-coloured, quartz-feldspar-rich material. In some outcrops the banding closely resembles sedimentary bedding.
The biotite gneisses grade into composite gneisses or migmatite in
which layers of biotite gneiss arc separated by bands of coarser-grained.
granitic material often containing metacrysts of wh ite feldspar which range
from one-quarter to three-quarters of an inch in maximum dimension.
In places narrow sills of aplite and pegmatite make up much of the rock.
East of Tulabi Lake the rocks consist of 50 per cent or more of the
granitic material which forms regular bands from two to six inches wide.
with further decrease in the amount of fine-grained biotite gneiss the
migmatite grades into gneissic granodiorite. In the northeast section of the
map-area biotite gneiss occurs only in the southeast part of the belt, and
most of the area is underlain by biotite migmatite containing 50 per cent
or more of granitic material which increases in amount northwards
and the migmatite gradually grades into gneissic granodiorite. Much of the
gneissic banding in this area is highly contorted, and numerous small
irregular folds which are characteristic of deformation in a mobile or
highly viscous material are common.
-
II -
Microscopically the biotitc gneisses h ave a granoblastic texture with
quartz and oligoclase forming a simple mosa ic or a wavy granulitie fabric.
T he quartz is usually strained to varying degrees and h as sutured boundaries. The grains invariably contain trains of minute inclusions. The
oligoclase is unaltered and commonly sh ows albite twinning. Large grains
are generally poikiloblastic with inclusions of quartz and biotite. They
often grow across contacts between the light and dark bands. If the biotite
content is high, the texture is lepidoblastic. The biotite is pleochroic from
dark brown to light tan. Dark, pleochroic halos surround numerous metamicts some of which are large enough to be identified as zircon. The
biotite shows some alteration to penninite along cleavages, sometimes with
the release of minute grains of magnetite.
Minor constituents are blue-green hornblende, apatite, muscovite,
magnetite, and microcline. The microcline is interstitial to quartz and
plagioclase and also veins the oth er minerals. It appears to h ave been introduced. The limited amount of microscopic study to date indicates a gradual
increase in the content of potash feldspar towards the north in both the
Tulabi Lake area and the area northeast of H anson Lake. Garnet wh en
present is confined mainly to the biotite-rich layers.
Under the microscope the granitic material of the biotite migmatite
shows a granoblastic texture with quartz and plagioclase formi ng a simple
mosaic and the biotite and h ornblende having a subparallel arrangement.
T he rock has essentially the composition of gradodiorite. Most of the microcline is interstitial to the quartz and plagioclase, but it also forms a few subhedral to anhedral grains. Apatite, magnetite, zircon, chlorite, sericite, and
sphene are minor constituents. In the porphyroblastic facies the metacrysts
of white feldspar are oligoclase.
Hornblende Gneiss (5), Amphibolite (5a), and Migmatite (5b)
Hornblendic gneisses structurally overlie the biotitic gneisses in the
northwest and northeast sections of the map-area and surround a central
core of quartz diorite in the a rea of Jackpine Lake. Like the biotite gneisses
they show all gradations from a hornblendic gneiss of obvious sedimen tary
origin to a rock consisting largely of granitic material with only a few
narrow bands and elongated inclusions of the origin al sedimentary materia l.
In places, especially west and south of Tulabi Lake, the hornblende
gneisses are interlayered with a dark green, banded to massive amphibolite.
All three types may contain garnet.
Sills of aplite and pegmatite are common and are exceptionally n umerous northwest of Jackpine Lake and north of Botham Bay on the east side
of Hanson Lake.
The hornblende gneiss (5) consists of alternating ligh t and dark bands
from one-quarter inch to four inches thick. The light-coloured bands
consist almost entirely of quartz and feldspar, and the dark bands in
addition contain much hornblende and usually some biotite. Garnets may
be present and in some b ands are abundant. The needles of horn blende
often show parallel alignment and plunge in the direction of the major
fold axes.
Microscopically the dark bands consist of a granoblastic aggregate of
quartz and plagioclase with h ornblende and biotite oriented parallel to the
margins of the bands. The h ornblende is strongly pleochroic and is either
blue green or brown green. The biotite is pleochroic from light brown to
almost black. Metamicts with pleochroic halos are rare or entirely absent
-12-
in some thin sections. Both the hornblende and biotite show some alteration to chlorite. The light-coloured bands consist of a wavy granulitic
aggregate of quartz and plagioclase. The grain orientation parallels the
banding and thin flakes of biotite are perfectly aligned. The feldspar in
both types of banding is andesine. It is clear and unaltered and shows both
albite and pericline twinning. The quartz is always strained and contains
trains of minute inclusions. The contacts between the gneissic bands appear
sharp in hand specimens, but, under the microscope, plagioclase and quartz
grains are seen to project across the contacts. Minor constituents are
magnetite, apatite, calcite, microcline, epidote, sph ene, and zircon.
The amphibolites (Sa) interlayered with the hornblende gneiss west
and south of Tulabi Lake are typically dark green to black and are usually
banded, but in places appear quite massive. They are fine to medium
grained and consist essentially of hornblende and feldspar. The welldeveloped banding is suggestive of a sedimentary origin. Mineralogical
and structural evidence suggests that the massive type may have originally
been sills of gabbroic composition.
Microscopically the gneissic variety consists essentially of variable
amounts of dark-green, slightly poikiloblastic hornblende, andesine, and
quartz. Accessory minerals are apatite, magnetite, epidote, calcite, and
pyrite. The massive type consists of green hornblende and zon ed basic
andesine with accessory apatite, magnetite, biotite and quartz.
Hornblende migmatite (Sb) consists of alternating layers of horn blende gneiss and granitic material wh ich together form a composite gneiss
somewhat similar to that already described under biotite migmatite. However, the plagioclase is andesine instead of oligoclase, microcline is less, or
entirely absent, and the granitic layers have the composition of quartz
diorite rather than granodiorite.
Intrusive Rocks
Amphibolite, metadiorite, metagabbro (6)
This group includes a variety of types from fine-grained, massive,
dark-grey to black rocks of doubtful origin to medium- to coarse-grained
altered diorite and gabbro. They .outcrop in the area between Side Lake
and Bertrum Bay on the west side of Hanson Lake.
Small masses of fine-to coarse-grained metagabbro outcrop on the east
side of Bad Carrot Lake and at the north end of Side Lake. The rock is
dark grey to green with the coarser-grained variety mottled grey and dark
green. In thin section the rock is seen to consist almost entirely of hornblende and altered plagioclase. Accessory constituents are chlorite, saussurite, sericite, epidote, zoisite, apatite, magnetite, pyrite, chalcopyrite,
quartz, and garnet. The texture is equigranular-anhedral or allotriomorphic
The plagioclase is altered to a mixture of saussurite, sericite, epidote, and
dusty hematite. A green to yellow-brown hornblende forms over SO per
cent of the rock. I t occurs as anhedral grains with ragged borders and containing fine-grained disseminated magnetite. Larger grains also contain
inclusions of quartz, plagioclase, and apatite. The hornblende is partly
altered to chlorite.
The relationship of the metagabbro to the other intrusive rocks is
unknown. However, the alteration and recrystallization of the original
minerals would indicate they are more closely related to the syntectonic
granodiorite (7) th an to the post-tectonic diorite (9) .
-13-
The rocks of Unit 6 which border the northern half of the mass of
granodiorite lying between Side and Bad Carrot Lakes and the western
side of the granodiorite mass south of Jackpine Lake are very fine- to finegrain ed amphibolite and altered diorite. Petrographic evidence indicates
that the amphibolite is the result of metamorphism of volcanic rocks. The
small size and irregularity of the intrusions of diorite make it impossible to
separate them from the amphibolite on the scale of mapping employed.
In thin section the amphibolite is seen to consist principally of hornblende and plagioclase. The hornblende is a bluish green to green variety
and forms subparallel to parallel prisms which produce a nematoblastic
texture. The plagioclase is andesine and forms anhedral to subhedral,
generally untwinned grains interstitial to the hornblende. Minor constituents are biotite, chlorite, quartz, magnetite, calcite and apatite. The
metadiorite has approximately the same mineral composition but has an
equigranular-anhedral or allotriomorphic texture. Also some of the andesine
is zoned and shows combined albite-Carlsbad twinning.
Granodiorite and Related Rocks (7, 7a, and 7b)
Granodiorite and quartz diorite underlie extensive areas west and
northeast of Hanson Lake. They form masses which show conformable
relationships with the surrounding rocks. North of Jackpine Lake the main
body of quartz diorite occupies an anticlinal position with respect to the
major structure. Elsewhere, granodiorite forms large sills and phacolithlike concordant structures.
The granodiorite (7) and quartz diorite (7b) are typically mediumgrained, grey or pink rocks composed of quartz, feldspar, hornblende and/
or biotite. They can be distinguished from each other only with the aid of
the petrographic microscope, the quartz diorite containing little if any
microcline. On weathered surfaces the colour may vary from almost white
to salmon pink to dark grey, or dark grey mottled with light grey or
pink.
The granodiorite is either equigranular or porphyritic (7 a). The contact between the two types is either quite sharp or gradational over several
tens of feet. The phenocrysts are crystals of white plagioclase, up to threequarters of an inch long, in a medium grained equigranular groundmass.
A distinct foliation is a characteristic structure. It is formed by the
parallel alignment of biotite, h ornblende, and lenticular grains of quartz.
This foliation parallels the contacts of the larger masses, but in smaller
bodies it conforms with the regional foliation. A gneissic structure is developed near contacts where the granitic material has locally assimilated
biotite or hornblende gneiss.
Lineation of the mineral grains is often pronounced especially about
the nose of a plunging fold. The lineation results from the subparallel to
parallel alignment of needles of hornblende, ellipsoidal gra ins of quartz,
and elongated smears of biotite crystals. This lineation invariably plunges
in the same direction as the major fold axis.
As observed in thin section under the microscope the granodiorite and
quartz diorite are very similar. They possess the same texture and mineral
constituents except the quartz diorite contains at most only two per cent of
potash feldspar. The texture is foliated subhedral-granular to anhedralgranular or allotriomorphic. In the porphyritic facies of the granodiorite
phenocrysts of plagioclase are embedded in a groundmass having the above
-
14 --
texture. The phenocrysts and many of the larger grains of plagioclase in the
normal granodiorite and quartz diorite are partly crushed and drawn out
parallel to the foliation.
The granodiorite (7 and 7a) consists essentially of oligoclase, microquartz diorite (7b) contains oligoclase, quartz, hornblende, and a variable
quartz diorite (7b) contains oligoclase, quartz, hornblede, and a variable
amount of biotite; microlinc when present is only a minor constituent.
Zircon and apatite are characteristic accessories. Other minor constituents
as observed in thin section are chlorite, garnet, magnetite, sphene, epidotc,
calcite, sericite, and pyrite.
The oligoclasc has an anorthite con tent which ranges from 18 to 28
per cent. The majority of the grains conta in dust-like particles of hematite
which colour the feldspar a faint reddish-brown. Some sericite is usually
present. Many of the crystals show albite twinning and some have combined albite-Carlsbad or albite-pericline twins. The larger grains and
phenocrysts often have crush ed borders, and the albite twin lamellae are
bent and broken.
Quartz form s anhedral grains interstitial to the plagioclase. Most
grains show strain. Much of the quartz contains n umerous inclusions often
in trains or string-like arrangements. In several slides quartz forms a micrographic intergrowth with feldspar.
Microcline is generally clear and unaltered and forms 20 to 45 per
cent of the feldspar content of the granodiorite. I t occurs interstitially to
quartz and plagioclase and less frequen tly as subhedral crystals. It embays
and replaces the plagioclasc and occasionally veins quartz. Myrmekitc is
a minor constituent.
The hornblende is green to yellow brown and forms subhedral prisms
which lie in the plane of foliation and are often aligned in the direction
of the regional plunge of the major fold structures. Alteration of the horn blende is slight and when present consists of replacement by biotite and
chlorite.
Biotite is stron gly pleochroic, straw yellow to dark reddish brown or
black. The flakes are aligned parallel to the folia tion. A few radioactive
metamicts surrounded by pleochroic halos form inclusions. Some of the
biotite is partly altered to chlorite.
Quartz-feldspar porphyry (8)
and derived quartz-sericite schist (Sa)
Quartz-feldspar porphyry forms a small stock and numerous dykes and
sills which mainly intrude dacitic rocks of group 1 in the area between
Bertrum and Agnew Bays and the main section of H anson Lake.
The colour of the porphyry may be either grey or pinkish grey or
mottled pink and grey, with weathered surfaces having lighter shades of
the same colours. The rock is massive and possesses a foliation which in
the larger bodies of porphyry is not as well developed as the foliation in
the adjacent volcanic rocks. In places it is difficult to distinguish the intrusive porphyry from massive, porphyritic sections of dacitic lavas. Quartz is
the characteristic mineral and forms grey to opalescent bluish-grey, round
to ellipsoidal phenocrysts ranging in diameter from one-eighth to onequarter inch. The phenocrysts may be unevenly and widely scattered or
they may form as much as 20 per cent of the rock. Smaller, one-eighth inch
-15-
phenocrysts of grey and pink feldspar may also be present. The groundmass is apahanitic to very fine grained with visible quartz, feldspar, biotite,
and muscovite.
The study of thin sections shows there are two types of porphyry,
although this is not apparent in hand specimens nor in the field. The
difference between the two is in the amount of potash feldspar and the
anorthite content of the plagioclase. The bulk of the porphyry has the
composition of granite and contains albite as the plagioclase feldspar.
However, the porphyry on the west side of the peninsula separating Agnew
Bay from the main section of Hanson Lake and some other smaller bodies
of porphyry contain only a trace of microcline and have the composition
of quartz diorite.
The essential minerals forming the quartz-feldspar porphyry (granite
type) are orthoclase, microcline, quartz, albite, with an anorthite content
ranging between five and eight per cent, and some biotite. Minor components are apatite, zircon, magnetite, sericite, epidote, and calcite. The
essential minerals composing the quartz-feldspar porphyry (quartz diorite
type) are oligoclase, with an anorthite content ranging from 15 to 22 per
cent, quartz, and biotite. Accessory minerals are hornblende, apatite, zircon,
magnetite, sphene, microcline, calcite, and chlorite.
The quartz phenocrysts show all stages of cataclastic breakdown and
recrystallization from single anhedral grains with crushed borders to elliptical aggregates consisting of many grains of quartz with highly sutured
interlocking boundaries. The large single grains of quartz often contain
numerous minute black, opaque inclusions, and they invariably contain
strings or "bubble trains" of liquid-gas inclusions. Quartz also occurs in
the groundmass where it forms a simple mosaic with the feldspar.
The potash feldspar is both orthoclase and microcline which forms
clear, unaltered grains interstitial to the quartz and plagioclase of the
groundmass. Perthite was noted in several of the slides.
Plagioclase occurs as corroded and partly crushed phenocrysts and as
anhedral grains in the groundmass. It is mainly untwinned but may show
albite and combined albite-pericline twinning. It contains dust-like inclusions which give it a pale brown colour, and some sericite is usually
present. As previously mentioned the composition of the plagioclase is
albite in the granite-type porphyry and oligoclase in the quartz dioritetype porphyry.
Biotite, pleochroic from black to pale brown, forms small flakes with
parallel orientation throughout the groundmass. It is partly replaced by
scricite and chlorite.
The quartz-feldspar porphyry is altered to a quartz-sericitc schist (8a)
where it is cut by shear or fau lt zones. This is a highly foliated or schistose,
ligh t-coloured rock with eyes of quartz embedded in a sericitic groundmass.
Diorite and Related Rocks (9, and 9a to 9h)
A large batholith of diorite with facies which range in composition
from granodiorite to pyroxenite underlies the map-area south of Botham
Bay, and east and southeast of Hanson Lake. The size of the intrusion is
not known. To the south it passes beneath the flat-lying Ordovician dolomites, and its eastern extent beyond the map-area has not been indicated
-16-
on the adjoining map-sheet. Smaller related intrusions, usually in the form
of sills or dykes, cut the Amisk sediments and volcanic rocks within a
distance of several m iles from the main intrusion.
The main intrusion in the south part cJ. Hanson Lake is distinctl y
discordant as it cuts across and distorts the regional trend of the Amisk
strata. T he northeast margin south of Both am Bay is, however, conformable to the structural trend. Foliation within the intrusion is poorly defined
by parallel orientation of biotite and feldspar. It is best developed n ear the
margin and may be entirely lacking in the interior part of the mass. Unlike
the granodiorite (7) gneissic structure is rarely observed in the diorite.
Microscopic study of thin section shows a primary igneous texture with
only minor granulation and no recrystallization of the mineral constituents.
The diorite and related facies not only intrude Amisk strata but also
the quartz- feldspar porphyry (8) and the granodiorite (7). The textural
and structural features of the main intrusion indicate th at it is late syntectonic or even post- tectonic in age.
Diorite (9) and quartz diorite (9b) form the bulk of the intrusion.
T h ey are almost undistinguishable from each other in outcrop and hand
specimens, and, therefore, will be described together. T hey are mainly
medium grained, and usually mottled in shades of grey and black; a mauve
to buff-grey colour is typical. Visible minerals are feldspar, biotite, and
hornblende. The biotite is a ch aracteristic feature and occurs as large,
bright, shiny black fl akes scattered unevenly th roughout the rock.
Microscopically the diorite and quartz diorite h ave an anhedral to subhedral texture with biotite and hornblende segregated in clusters. The
essential minerals are andesine, biotite, and hornblende. Quartz forms 10
to 15 per cent of the quartz diorite but is only a minor accessory in the
diorite. Apatite, sphene, and titaniferous magnetite are diagnostic accessories. Other minerals occurring in minor amounts are hypersthene, myrmekite a radioactive metamict, orthoclase, microcline, zircon, sericite, saussurite, chlorite and leucoxene.
The andesine feldspar h as a composition range of An3 0 to An 43 and
commonly shows normal-type zoning. Many of the crystals h ave irregu lar,
corroded outlines and the albite twinning lamellae are frequently bent and
broken. There is usually some alteration to a m ixture of sericite and
saussurite.
Biotite, deep reddish brown to pale yellow brown, occurs as large
flakes showing some bending of the basal cleavage planes and as smaller
crystals usually accompanying hornblende with which it may be intergrown. The biotite commonly contains inclusions of apatite, sphene and
radioactive metamict. Some alteration to chlorite has occurred along the
basal cleavage.
The hornblende is typically green and often poikilitic with inclusions
of apatite and feldspar. It is embayed and replaced by andesine and quartz.
Rarely the hornblende surrounds cores of either n early colourless diopsidic
pyroxene or uralitized h ypersthene. Some alteration to chlorite occurs along
·
cleavage planes.
Quartz is interstitial to the andesine and mafic constituents. Occasionally it forms a myrmekitic intergrowth with the plagioclase.
Midway between H anson and Bay Lakes a northwest-trending fault
intersects the diorite which is mylonitized over a width of 30 or more feet.
-
17-
A few partly crushed feldspars give a porphyritic appearance to hand specimens, and the zone was originally mapped as a dyke of porphyry cutting
the diorite. Besides the mechanical breakdown of the rock, quartz and
microcline h ave been introduced as stringers and veinlets parallel to the
foliation.
•
Granodiorite (9a) closely resembles the quartz diorite and diorite but
usually has a reddish tinge, being mottled pink, grey and black. In places
it appears to grade into the diorite, but in other outcrops it definitely intrudes the diorite (9, and 9b) and gabbro (9c and 9d).
Microscopically it is similar to the quartz diorite but potash feldspar
is an essential rather than an accessory constituent. Both microcline and
orthoclase are present as large anhedral grains and smaller-grained aggregates interstitial to quartz and plagioclase. In places the granodiorite has a
porphyritic texture with phenocrysts of calcic oligoclase.
Gabbro (9c) and hypersthene gabbro ( 9d) underlie most of the area
in and about Winn Bay at the south end of Hanson Lake. Outcrops on
the peninsula west of Winn Bay show an interlayering of diorite and
gabbro in thick bands which trend north. In other places the diorite forms
dykes which intrude the gabbro.
The gabbro and hypersthene gabbro are medium grained, massive,
medium- to dark-grey rocks which weather with a grey and dark green or
black mottled surface. The two gabbros can be distinguished from each
other only microscopically, and in hand specimens they may even closely
resemble more basic hornblendic facies of the diorite. The hypersthene
gabbro is confined largely to the peninsula west of Winn Bay.
Microscopically the texture of the gabbro is anhedral to subhedral
equigranular. Some thin sections show a parallel alignment of the feldspar
crystals. The essential minerals are calcic plagioclase, hornblende, and
augite. In the noritic variety hypersthene is the principal pyroxene. Characteristic accessories are apatite and magnetite. Other minerals occurring
in minor quantities include biotite, a radioactive metamict, pyrite, pyrrhotite, epidote, saussurite, and chlorite.
The plagioclase is labradorite with an anorthite content between 55
and 65 per cen t. Albite, albite-Carlsbad, and albite-pericline twinning are
present. Some of the plagioclase shows normal zoning with a more calcic
core. Very minute dust-like inclusions give the labradorite a greyish cast,
and also many of the crystals contain minute rod-like inclusions with
parallel orientation. In the area of the north-trending fault which crosses
Winn Bay the gab bro is crushed and the plagioclase is almost completely
altered to saussurite. Elsewhere it is fresh-looking and unaltered.
Hypersthene forms anhedral to subhedral crystals and is weakly
pleochroic from colourless to pale pink. It generally contains numerous
needle-like inclusions showing parallel orientation. A few crystals show
lamellar intergrowth with a colourless to pale-green augite. Much of the
hypersthene is rimmed by either uralite or a pale-green h ornblende which
fills the interstices between plagioclase and pyroxene to form irregular,
optically continuous areas of the amphibole.
In the normal gabbro (9a) the pyroxene is a colourless to pale-brown
diopsidic augite containing numerous oriented rod-like inclusions. The
augite is partly altered to secondary green hornblende which in turn may
show some alteration to chlorite.
18 -
Primary h ornblende where presen t is a deep-brown variety and forms
irregular anhedral grain interstitial to the plagioclase and pyroxenes. It is
sometimes intergrown with a deep red-brown biotite. Occasionally the
hornblende is partly altered to either a green secondary h ornblende or to
chlorite.
Pyroxenite ( 9e) outcrops in the south half of the peninsula between
Winn and Mcllvenna Bays. The u ltrabasic rock was n ot observed in contact with the h ypersthene gabbro (9d) but less basic facies of the former
closely resemble th e more basic facies of the latter. A dyke of biotite pyroxenite cuts the diorite (9) northwest of Bay Lake. D ykes and small masses
of ul trabasic rock also intrude the Amisk volcanic and sedimentary rocks.
The ultrabasic rock is ma inly pyroxen ite, but locally olivine is dominant and the rock may be classed as peridotite. The pyroxenite is medium to
coarse grained, dark grey on fresh surfaces, a rusty grey-green on weathered surfaces, and the only visible mineral is pyroxene. The peridotite is finer
grained, dark green to black, and weathers blue grey to reddish brown.
Microscopically the pyroxenite shows a mosaic texture composed of
anhedral grains of clinopyroxene with variable minor amounts of olivine,
plagioclase, apatite, h ornblende, antigorite, biotite, magnetite, pyrrhotite,
and chlorite.
The clinopyroxen e is colourless diopside and pale-green augite in
about equal proportions. The olivine occurs interstitially to the. pyroxenes.
I t is crossed by fractures along which it is altered to antigorite. The plagioclase when present is also an interstitial component and is a calcic labradoritc. Locally the pyroxenite contains a little nickeliferous pyrrhotite.
Quartz diorite porphyry or feldspar porphyry (9{) outcrops as a long,
narrow sill on the east side of the peninsula between Agnew Bay and
Hanson Lake, and also forms most of the long island immediately south of
the peninsula. This rock-type h as been placed in division 9 because of its
mineralogical similarity to the diorite, especially in the content and amount
of the accessory minerals: apatite, sphcne, and titaniferous magnetite. I n
hand specimens th e rock is porphyritic with one-sixteenth to one-eighth
inch white feldspar phenocrysts scattered throughou t an aphanitic to very
fine-grained, dark grey groundmass. The weathered surface h as a greygreen colour.
As observed in thin sections the rock consists essentially of plagioclase,
hornblende, and quartz, with accessary biotite, apatite, sphcnc, a radioactive metamict, titaniferous magnetite, leucoxene, epidote, sericite, calcite,
and pyrite.
The plagioclase is calcic oligoclase and forms the feldspar phenocrysts
as well as anhedral grains in the groundmass. The phenocrysts show albite,
albite-Carlsbad , and albite-pericline twinning. The plagioclase is slightly
altered with development of minute flakes of sericite and rods of epidotc.
A green h ornblende, oligoclase, and quartz form most of the groundmass together with some biotite and the accessory minerals mentioned
previously.
Diorite porphyry (9g) outcrops on the narrow peninsula northwest of
Winn Island in H anson Lake. Its relationship to the quartz diorite porphyry (9f) and metadiorite (9h) is not known through lack of outcrop.
In the field the rock was referred to as feldspar-h ornblende porphyry with
one-eighth to one-quarter inch white feldspars and small needle-like
-19 -
crystals of black hornblende embedded in a very fine- to fine-grained grey
groundmass. The weathered surface is spotted white and black on a
"salt-and-pepper" background.
As seen in thin section the rock is mineralogically the same as the
diorite (9). Basic oligoclase, green h ornblende, and deep-brown biotite are
the essential minerals and occur as phenocrysts as well as in the groundmass. Accessory minerals are apatite, sphene, titaniferous magnetite, quartz,
a radioactive metamict, sericite, chlorite, calcite, and pyrrhotite.
A highly altered and crushed facies of the diorite porphyry also outcrops on the peninsula. The granulation has broken down and destroyed
the original phenocrysts and the texture of the rock is aphanitic to very
fine grained rather than porphyritic. The fresh surface is grey with black
streaks, and the rock weathers grey to brownish grey to speckled grey and
black, often with a fine pitted surface.
As observed in thin section the original phenocrysts are completely
granulated and drawn out into lenticular streaks. Most of the plagioclase is
replaced by a mixture of calcite, sericite, and chlorite, what remains is
recrystallized albitc. Hornblende is completely altered to biotite and
chlorite.
Hornblende gabbro (9h) forms large sills on the east side of the
peninsula west of Winn Island in H anson Lake. Also a few smaller,
irregular-shaped bodies and dykes intrude the Amisk volcanic rocks and
quartz porphyry in the area to the west. The rock is fine to medium
grained, porphyritic to equigranular, and of a dark grey-green to green
colour. The weathered surface is generally mottled black and grey. Hornblende forms from 50 to 80 per cent of the rock and the remainder is
mainly feldspar. In a few outcrops a little quartz is visible.
As seen in thin section the rock consists mainly of green hornblende
and calcic andesine or labradorite with minor and variable amounts of
biotite, magnetite, quartz, apatite, a radioactive metamict, epidote, saussurite, chlorite, and calcite.
The hornblende is pleochroic in sh ades of green, yellow green, and
yellow brown. It may show zoning and is freq uently twinned. In the porphyritic facies the hornblende forms large phenocrysts with corroded boundaries and a poikilitic texture with plagioclase inclusions. The hornblende
is sometimes broken and crushed.
Andesine or labradorite forms anhedral grains interstitial to the hornblende. When quartz is present it is often in myrmekitic intergrowth with
the feldspar.
Biotite when present is usually intergrown with the hornblende and
is partly altered to chlorite. Magnetite is relatively abundant as an acces sary mineral and forms up to five per cent of the rock.
The hornblende gabbro is placed in Unit 9 because it definitely intrudes the quartz porphyry (8), the minerals composing it are relatively
unaltered, and the rock is massive and unfoliated indicating a post-tectonic
age.
Microcline Granite (10)
An elongated mass of microcline granite intrudes the dacitic volcanic
rocks east and southeast of Bad Carrot Lake. Larger intrusive masses occur
just north of the map-area, but only the south end of one such mass out-
-20-
crops within the map-area where it intrudes the gneissic rocks north of
Botham Bay.
The granite is medium grained, equigranular to porphyritic, massive
with a poorly developed foliation, leucocratic, and pink or pink and grey
mottled on both fresh and weathered surfaces.
Much of the granite east of Bad Carrot Lake is not typical of the
microcline granite. It is cut by a major fault zone and is highly crushed
and altered. Fresh and weathered surfaces are coloured a deep salmon red.
In the thin sections examined the granite is composed of up to 60 per
cent potash feldspar, quartz, sodic oligoclase, and biotite. Accessory constituents are zircon, apatite, a radioactive metamict, sericite, chlorite, and
calcite.
The potash feldspar is mainly microcline but orthoclase may be present.
The microcline forms poikilitic phenocrysts enclosing quartz and/ or oligoclase, and it also occurs as anhedral grains which embay plagioclase and
quartz. Both perthitic and antiperthitic intergrowths are present. The
potash feldspar is generally clear and unaltered, but in the crushed granite
east of Bad Carrot Lake it is a distinct brownish-red colour being clouded
with minute particles of hematite.
The sodic oligoclase is generally partly altered to sericite and clouded
with hematite dust. It is subhedral to euhedral and frequently the albite
twinning lamellae are bent and broken. Myrmekite forms interstitial patches
and marginal rims.
Quartz is interstitial, usually strained, sometimes crushed, and contains minute inclusions or "bubble trains." Biotite is pleochroic from deep
brown to straw yellow. It is generally partly altered to chlorite. Inclusions
are a radioactive metamict, apatite, and quartz.
Pegmatite
Although not shown on the geologic map accompanying this report,
sills, dykes and irregular bodies of pegmatite are common in the northern
half of the map-area. They increase in number and size to the north.
Pegmatite is exceptionally abundant to the north of Hanson and Jackpine
Lakes. Some bodies north of the map-area are sufficiently large to constitute mappable units on the scale of one mile to one inch.
The majority of the pegmatite bodies consist essentially of feldspar
and quartz. Muscovite is often present in appreciable amounts. The feldspar crystals are mostly from one inch to two inches long, but, in some of
the larger bodies, may attain a length of 24 to 30 inches. The quartz is
white to smoky, occupies an interstitial position to the feldspar crystals
or, in some places, regular intergrowths of quartz and feldspar develop a
typical graphic structure. Crystals or books of muscovite up to three inches
in diameter and one-half inch thick are associated with quartz-rich facies
of the pegmatite. Sometimes the muscovite crystals form a radiating structure with a garnet at the center. These garnets are dodecahedral and up
to three-quarter inch in diameter.
In addition to feldspar, quartz, and muscovite, a few pegmatites
contain scattered crystals of one or more of the following: biotite, zircon,
tourmaline, uraninite, and secondary radioactive minerals. In one dyke
-
21
just north of Hanson Lake cubic crystals of uraninite up to l Y:i inches
on a side are surrounded by a radiating fracture zone, and the feldspar is
stained a deep red. Quartz in the vicinity of the crystals is almost black.
The colour of the pegmatites depends on the colour of the feldspar.
Thus, some pegmatites are uniformly white to light grey, others are pink
to salmon red, and some may be coarsely mottled pink and white.
Structurally the pegmatite bodies are massive an d do not show any
zoning of the mineral constituents. Contacts with the surrounding rocks
are usually sharp.
Thin section study of the pegmatites indicates a compositional range
from granite to granodiorite depending on the relative amounts of potash
feldspa~ and plagioclase.
The plagioclase varies from calcic oligoclase in th e granodioritic pegmatite to albite in granitic pegmatite. The colour in h and specimens may
be ei ther white or buff. It is frequently embayed and replaced by microcline which may also form a patch-type antiperthitic intergrowth with the
plagioclase. The potash feldspar is invariably microcline which in h and
specimens may be either white or pink.
Ordovician Dolomite and Sandstone (11)
In the south h alf of the area the Precambrian-Paleozoic contact is
marked by a north-facing escarpment which rises 20 to 60 feet above the
country to the north. The escarpment is not straight but is deeply indented
by long, narrow, south-trending muskeg or drift-filled valleys which are
probably underlain by Precambrian rocks. Nine small, flat-topped outliers
of the Paleozoic strata occur just to the north of the main escarpment.
The nearly horizontal strata of O rdovician age rest with great unconformity upon the Precambrian rocks and consist of a basal sandstone
overlain by dolomite.
Bruce (1918) on the basis of fossils collected at Namew and Amisk
Lakes placed the age as middle Ordovician. Kupsch (1953) from fossils
collected in the Namew Lake-Ballantyne Bay area correlates the sandstone
with the Winnipeg formation and the dolomites with the Red River.
Winnipeg Sandstone
The Winnipeg sandstone is a greyish orange, medium-grained sand
wh ich is friable but will stand up in vertical faces, see Plate 3, Fig. 2.
T he outcrop pattern is linear and follows the base of the P aleozoic
escarpment. Talus at the base of the outcrops of dolomite effectively prevents a complete section of the sandstone from being observed. However,
on the west side of the peninsula at the entrance to Mcllvenna Bay the
talus of dolomite is not present, and it was possible by digging a pit to
obtain a complete section of the basal sands.
The following data have been taken from Chernoff's study (1955) of
the sandstone.
Section 1 (Hanson Lake)
Location: South shore of Hanson Lake, just west of the entrance to
Mcllvenna Bay.
-22-
Elevation: Base of the section is abou t one foot a bove leYel of H anson
Lake.
Section: Measured with a cloth metall ic tape and sampled by C. Chernoff,
L. Clark, W. Petruk, and 0. Lesiuk, 1954. Mechanical analysis and
heavy mineral study by C. Chernoff, 1955.
T hickness in
Unit
Description
feet and inches
O verlying
D olomite: mottled greyish orange, 10YR7/ 4, and very
pale orange, 10YR8/ 2. H as poor pin-point porosity
w ith concentration s of iron oxide in the pores. Mediocrystalline with floating sand grains. Microscopic examination reveals 95 per cent dolomite, 4 per cent
quartz, and 1 per cent iron ox ide coating.
No. 12
No. 11
Quartzose dolomite; greyish orange, 1OYR7/ 4. Quartz
grains are of silt size, sub-rounded, medium sphericity.
Dolomite and calcite are medio-crystalline. Poor pinpoint porosity with concentrations of iron oxide in the
pores. Microscopic examination reveals 20 per cent
quartz, 77 per cent dolomite and calcite and 3 per cent
iron oxide (coating on carbonate and quartz grains).
Carbonates fill fractures in the quartz grains.
Calcareous orthoquartzite; dark yellowish
5"
orange,
10YR6/ 6. Quartz is of a very fine sand-grain size.
No. 10
No. 9
No. 8
Carbonate matrix effervesces in cold, dilute hydrochloric acid. Quartz gra ins are sub- rounded and highly
spherical. Microscopic examination reveals 42 per cent
quartz (some gra ins contain gas bubble inclusion s,
many have undulatory extinction) , 50 per cent carbonate, 8 per cent iron oxide ( coatin~ the grains and
concentrated in pin head masses in the pores), traces
of muscovite, bioti te, tourmaline, and rounded grains
of magnetite.
3"
Calcareous orthoquartzite; dark yellowish orange,
10YR6/ 6. Quartz is of very fine sand-grain size.
Carbonate matrix effervesces in cold dilute HCI. Poor
pin-point porosity. Microscopic examination: 55 per
cent quartz (well-rounded, highly spherical, bubble
inclusions, and undulatory extinction), 40 per cent
carbonate (some rhombohedrons, probably dolomite,
are well developed along the edges of the pores) , 5 per
cent iron oxide coating the grains.
5"
Calcareous orthoquartzite; moderate reddish brown,
10R4/ 6. Quartz of fine sa nd-grain size. carbonate
matrix effervesces in cold dilute HCI. 45 per cent
quartz, 45 per cent carbonate and 10 per cent iron
oxide coating the grains, trace of biotite.
4"
Orthoquartzite, very pale orange, 5YR8/ 2. W ell
sorted, well rounded, highly spherical quartz grains in
the coarse-grained sand range. Quartz grains h ave a
-
23 -
Unit
Thickness in
feet and inches
very thin coating of iron oxide on them. The sand is
easily shoveled but stands up in vertical faces. Cross3'4"
bedding is visible throughout the layer.
Description
No. 7
Orthoquartzite, same as above except that crossbedding is confined to the lower part of the bed with
no discernable cross- bedding in the upper part.
No. 6
Orthoquartzite, same as above, cross-bedding is again
visible in the lower part only.
1'11"
No. 5
Orthoquartzite, same as above, no visible cross-bedding
4"
No. 4
Orthoquartzite, same as above, no visible cross-bedding.
1'9"
No. 3
Orthoquartzite, same as above.
6'8"
No. 2
Oligomicitic, quartz pebble breccia, greyish orange,
10YR8/ 4. Very angular quartz pebbles up to four
inches across in a coarse-grained well sorted matrix.
The average d iameter of the sand grains is 0.4 mm.
I ron oxide coats the sand and pebbles and also fills
fractures in the pebbles. The thickness of the bed is
variable from ll,i" to 2".
Total thickness of Winnipeg sandstone
No. 1
1'5"
2"
17'0"
Kaolinitic clay; quartzose, white, silt to clay range,
some quartz grains are up to fine sand-grain size, noncalcareous. Kaolinitic odour. No preferred orientation
of the platy clay particles. Greasy when wet. Thickness is variable from 1 to 2 inches.
2"
Total thickness of section measured
17'2"
Underlying Weath ered Precambrian.
Structural features
Horizontal beds from four inches to six feet in thickness are observable in the outcrop. The bedding planes are sharply defined by bands,
a quarter inch thick, of a reddish sand containing quartz grains in two
millimeter diameter range.
Faint cross-bedding is discernable in the upper six feet of the unconsolidated sand. No cross-bedding can be seen in the lower nine feet or in
the indurated, overlying sandstone.
Dips taken by Brunton compass in two directions at right angles to
each other indicate horizontal beds.
Textural features
Samples were taken by the writer with the aid of Messrs. Lloyd Clark,
Orest Lesiuk and William Petruk. Samples were secured from the lower
and upper part of each bed. For th e lower six-foot bed three samples were
taken and then mixed for th e sieve analyses. The approximate weight of
-24-
each sample obtained was in the order of 300 to 400 grams. The samples
were split by hand quartering to 50-gram representatives which were used
in the analyses.
The following data represent some of the results of screen analyses
made by C. Chernoff:
W eight per cent
Unit
Unit
Tyler
Mesh
5
9
16
32
60
115
250
Pan.
Larger than very coarse sand, 1.98 1 mm.
plus .. ...................... ........... .. .......... .............. .... ...
Very coarse sand (0.491-l.98 l mm.) .. ........
Coarse sand (0.495-0.991 mm.) ..................
Medium sand (0.246 - 0.495 mm.) ......... .....
Fine sand (0.124-0.246 mm.) ........................
Very fine sand (0.061-0.124 mm.) .......... .. ..
Smaller than very fine sand (0.06 1 mm.) ..
Median diameter (Md.) .................. ..............
Sorting coefficient (So.) ..... ....... ... ................ .
0.94
7.70
24.20
54.00
12.59
0.37
0.19
0.40mm.
1.40
8
0. 19
4.05
29.71
59.85
5.98
0.19
0.44mm.
1.22
The foll owing are average rnlues of sphericity and roundn ess :
I . Material retained on Tyler mesh screen No. 9
Value
Sphericity
R oundness
.7- .9
.4- .6
.1- .3
O per cent
15 per cent
85 per cent
12 per cent
62 per cent
26 per cent
2. Material retained on T yler mesh screen No. 16
Value
.7-.9
.4-.6
.1-.3
Sphericity
88 per cent
12 per cent
0 per cent
Roundness
61 per cent
29 per cent
10 per cent
3. Material retained on Tyler mesh screen No. 32
Value
.7- .9
.4-.6
.1- .3
Sphericity
98 per cent
2 per cen t
0 per cent
Roundness
75 per cent
22 per cent
3 per cent
4. Materi al retained on Tyler mesh screen No. 60
Value
.7- .9
.4-.6
.1-.3
Sphericity
75 per cent
25 per cent
0 per cent
Rou ndness
57 per cent
3 1 per cent
12 per cen t
5. Material retained on T yler mesh screen No. 115
Sphericity
Roundness
Value
.7- .9
51 per cent
24 per cent
56 per cent
.4-.6
43 per cent
20 per cent
6 per cent
.1-.3
-
25 -
6. Material retained on Tyler mesh screen No. 250
Value
Sphericity
Roundness
.7-.9
.4-.6
.1- .3
51 per cent
33 per cent
16 per cent
5 per cent
54 per cent
41 per cent
The sphericity of the grain decreases with decrease of grain size, and
the highest sphericity occurs in th e grain sizes which are most abundant.
The roundness is best developed in the coarser fractions, and angularity is
most pronounced in the finer material.
The majority of the grains fo rming the coarser fractions are highl y
frosted and pitted, while the finer- grained particles tend to be frosted and
pitted to a lesser degree or are devoid of frosting and pitting. Some of the
pits in the larger grains are fa irly deep and have a small diameter suggesting that chem ical action may have been important in producing the pits.
A h eavy mineral analysis of a SO-gram sample of sand representative
of the section was made and yielded approximately 70 grains of heavy
minerals as follows:
1. Magnetite, abundant. Grains well rounded.
2. Tourmaline, most ab undant. The most common is a brown-black
variety, other types, however, are present. Grains are either well rounded,
spherical in shape, or are prism s with rounded ends.
3. Zircon, common. Prismatic forms terminated by rounded ends, some
spherical grains are also present.
4. Garnet, rare. Irregular, poikilitic, grains.
5. Rutile, very rare. I rregular grains.
Light minerals other than quartz are very rare and include only
muscovite and chlorite. A few quartz grains show authigenic growth of
quartz which is rounded and frosted. This would suggest that some of the
sands h ave undergone at least two cycles of reworking. Most of the quartz
grains are clear, some, however, contain numerous inclusions often in the
form of " bubble trains." Less common are inclusions of magnetite, tourmaline, and zircon. Undulatory extinction and strains shadows are present in
some of the quartz.
The layer of kaolinitic clay overlying the weathered Precambrian and
underlying the sands is aph anitic to fine grained, white, frangible, structureless, and plastic when wet. I t contains some fine- grained quartz.
Microscopically the clay consists mainly of kaolinite and a li ttle
gibbsite. The kaolinite has the following optical properties : colourless,
biaxial, negative optic sign, low birefringence, refractive index between
1.55 and 1.56. The optical properties for the gibbsite are colourless, biaxial,
positive optic sign, high birefringence, and refractive index slightly above
1.54.
The material underlying the kaolinitic layer at the bottom of the pit
consists of highly weathered Precambrian quartz-sericite and chlorite
schists; the former obviously derived from the quartz-feldspar porphyry (8)
and the latter from a more basic igneous rock.
-26-
Red River Dolomite
The Red River dolomite outcrops almost continuously along the edge
of the Paleozoic escarpment and around the margins of the outliers. It often
forms vertical cliffs ten to 50 feet high.
The lowest part of the formation can be easily observed wherever the
Winnipeg sandstone is exposed, see Plate 3, Fig. I. Section 1, previously
described, illustrates the nature of the basal Red River beds. In other
places a few quartz pebbles up to one-half inch diameter occur with the
"floating" sand grains. Generally, the two lowermost beds have a high
content of hematite and in places contain concretions of that mineral.
Although fossils are scarce in the dolomite, in places they arc fairly abun dant in the ferruginous beds immediately above the contact with the
u nderlying Winnipeg sandstone.
The dolomite is not divisible into lower mottled and upper nonmottled units as in the Amisk Lake area (Byers and Dahlstrom, 1954,
p. 70) . Sections of mottled dolomite do occur but not necessarily in the
lower part of the formation , and when traced laterally for any distance the
mottling disappears.
The beds which range in thickness from two to 24 inches are irregular
and non-persistent. Even beds 36 to 48 inches thick h ave a lateral exten t
of only 100 to 200 feet. The beds in the lower 20 to 30 feet are mostly
thin in the order of two to four inches. The more massive beds occur at
irregular intervals higher up in the formation. Mud cracks and ripple
marks are common structures throughout the observed section which is in
the order of 80 feet. Joints are a common secondary structure. They occur
in several sets, with average stri kes as follows: (1) north, (2) cast, (3)
northwest, and ( 4) northeast. Many of the joints h ave curved surfaces •
both along stri ke and down dip and resemble giant conchoidal fractures.
Pleistocene and Recent
The superficial unconsolidated deposits were not a part of the field
investigation excep t in so far as th ey involved deposits of sand and gravel
which might prove to be of economic importance in the future. No extensive deposits of gravel were discovered during the field work. High grade
quartz sand occurs locally as thin sheet-like deposits immediately north of
the Paleozoic escarpment. They have been formed from the Winnipeg
sandstone.
Pleistocene till and glacial lake clay and silt form level or slightly
undulating surfaces with few outcrops of bedrock and extensive muskeg
and swamp cover in the area south and southwest of H anson Lake.
Recent deposits consist of local accumulations of beach sand and
gravel along lake shor"~. clay and silt along river valleys, and peat in
swamps and muskegs.
STRUCTURAL GEOLOGY
Folds
Three major south-plunging anticlines and two intervening synclines
form the main structural units in the Hanson Lake area. From west to
east they h ave been named the Tulabi Lake anticline, Side Lake syncline,
-27-
Jackpine Lake anticline, Hanson Lake syncline, and the Botham Bay
anticline. Graded bedding, relationship of cleavage to bedding, and minor
dragfolds were used to determine the attitude of the Hanson Lake syncline.
Graded bedding in tuffs, brecciated flow tops, flow contacts, see Plate 2,
Fig. 1, and mineral lineation were helpful in gaining a limited knowledge
of the structure west of Hanson Lake. Marker h orizons of h ornblende
gneiss outline the major structures in the northern part of the area, and
mineral lineation indicates the plunge of the fold axes. The attitude of the
anticlinal structures h as also been determin ed by the use of a statistical
method developed by Dahlstrom (Byers and Dahlstrom, 1954, Appendix,
p. 163).
The Tulabi Lake anticline is an open asymmetric fold with a vertical
to steeply dipping west limb and a more gently dipping east limb. A statistical analysis of the fold, see Fig. la, indicates that the axial plane strikes
south 18 degrees west and dips 60 degrees cast. This agrees with the strike
of the trace of the axial plane as indicated by the outcrop pattern. The
plunge as determined statistically is 18 degrees-south 7 degrees west, as
compared with an average plunge of 25 degrees-south 5 degrees east
determined from field observations of mineral lineation. The axial formation in the immediate area of Tulabi Lake is interbeddcd biotite gneiss and
calc-silicate gneiss. The crestal zone is crenulated by small folds which
also plunge south. South of Tulabi Lake the fold-structure is occupied by
a mass granodiorite with the form of a large phacoli th.
The Side Lake syncline lies east of the Tulabi La ke anticline with the
west limb of the syncline corresponding to the east limb of the Tulabi
Lake fold. The east limb of the syncline h as been largely eliminated by a
major, regional north-trending fault which passes through Guyader and
• Bad Carrot Lakes. The syncline is occupied by massive dacitic lavas and
a few n arrow bands of interbedded tuffs. A few poor top determinations
on flow contacts east and north of Side Lake indicate the strata face east.
Between Side and Bad Carrot Lakes the structure is intruded by a small
discordant boss of granodiorite.
The Jackpine Lake anticline is a nearly vertical isoclinal fold. The
west limb which is slightly overturned to the west, is partly cut out by the
large north-trending regional fault mentioned in the previous paragraph.
The statistical analysis, see Fig. 1b, indicates the axial plane strikes south
14 degrees west and dips 80 degrees east, and th e fold axis plunges 60
degrees-south 8 degrees east. The average plunge as determined from
field data on mineral lineation is 45 degrees- south IO degrees east. N orth
and west of Jackpine Lake the axial outcrop is quartz diorite. This igneous
mass is probably conformable and phacolithic in structure.
The Hanson Lake syncline underlies most of Hanson Lake. Its west
limb is sh ared with the Jackpine Lake anticline, but its east limb has been
almost entirely eliminated by the large batholithic intrusion of quartz
diorite south and east of Hanson Lake. The axial outcrop of the syncline
is largely greywacke with some interbedded conglomerate which outcrops
on the islands in the main section of Hanson Lake. This belt of sediments
is deformed into numerous small isoclinal folds which plunge either to the
north or south generally at angles not exceeding 30 degrees. A few of the
folds are slightly overturned to the west.
-
28 -
TU LAB I
FIG. lo
LAKE
L 1neot 1on
a nd po les
to
gneissos,ty ( 144 poles, con tour s
at
2-4-6-8 % ).
I
I
A.P.
,/
, ;,
A.t_/., .
~~
x
JACKPINE
FIG . lb.
L1neolions
6-18-24 %), and
contours at
poles
l o gne i ssos it y, (343 po l es,
at 1-2-4-6 - 12%).
co ntours
NORTHEA S T
F I G. l e.
gne issos i ty ,
at
HAN S ON
L ineotion
and poles
LAKE
(33 poi nts,
I
I
to
I
( 142 poles , contours
I A.P.
2-5- 10%) .
I
I
' •,?
A.L.
~ r-."" . .
I
' •
I
Figure I. Pole diagrams of fold structures, Hanson Lake area. (A.P. A.L. - axial line).
-29-
axial plane,
The Botham Bay anticline is a more complex structure than the two
other anticlinal folds and consists of several small folds which are superimposed on the limbs of the larger structure. The axial outcrop of the main
fold is biotite gneiss and in this respect it is similar to the Tulabi Lake
anticline. Sills and phacoliths of granodiorite form a considerable portion
of the structure. The statistical analysis, see Fig. le, of this fold indicates
an average plunge of 55 degrees-south 20 degrees east, and the strike and
dip of the axial plane as being south 10 degrees west and 70 degrees east,
respectively. Field data on mineral lineation and minor drag folds indicate
a plunge of 30 degrees-south 15 degrees east.
Faults
The larger faults and shear zones tend to parallel the regional strike
of the formations and are, therefore, difficult to recognize as they do not
cause any appreciable or obvious offsetting of contacts, even though the
amount of movement may be great. H owever, the major faults are accompanied by considerable deformation and alteration of the adjacent wallrocks, and they are in places marked by well developed topographic lineaments that are readily detected from the aerial photographs of the area.
A few of the more prominent lineaments occur in the area underlain by the
Ordovician dolomite south of the map-area.
The fault which trends north through Guyader and Bad Carrot Lakes
is either a branch or the main section of a regional fault structure which
extends at least as far as Numabin Bay at the south end of Reindeer Lake,
a distance of 112 miles. For most of its length the fault zone is marked by
a well developed topographic linear depression, and, in places, its presence
has been substantiated by geological mapping (Budding and Kirkland,
1956, pp. 33-34, and Kirkland, 1957). In the Hanson Lake area the fault
zone is characterized by a mylonitic and altered zone up to 600 feet wide.
H ornblende gneiss and amphibolite are partly chloritized and saussuritized.
Massive dacitic flows adjacent to the fault are fractu red and veined by
quartz and epidote. Intense red iron-staining of the rocks is a characteristic
feature especially where the fault intersects granodiorite and biotite gneiss.
Strong shearing at several places along the fault dips steeply east suggesting that the fault dips in the same direction. The magnitude of the move ment along the fault zone is unknown, but it must be large as the fault
has eliminated much of the east limb of the Side Lake syncline. Immediately north of the map-area the displacement of a granodiorite-hornblende
gneiss contact shows a left h and strike separation of about one mile. Budding and Kirkland (1956, p. 34) state that field data suggest a predominant
left hand movement, the cast side having moved up and to the north
relative to the west side.
At least two branch faults are associated with the major fault described
in the previous paragraph. One branches off to the southwest three miles
north of Bad Carrot Lake and then swings south to pass through Side
Lake. The second fault branches off to the south -southeast about one mile
north of Bad Carrot Lake. Both faults are marked by topographic lineaments for part of their known lengths and are accompanied by mylonitic
and altered zones similar to the main fault zone.
A north-trending shear zone cuts the volcanic rocks and intrusive
quartz-feldspar porphyry on the large peninsula separating Bertrum Bay
-
30-
and Hanson Lake proper. A zone of quartz-sericite schist along the \vest
shore of the entrance to Mcllvenna Bay probably represents the southerly
continuation of this fault. A marked topographic lineament in the flatlying Ordovician dolomite continues for 12 miles south of Hanson Lake
along the projected strike of this shear zone.
A north-trending fault intersects the mass of gabbro in the Winn Bay
area at the south end of Hanson Lake. Movement along the fault has
produced some crushing and mylonitization of the gabbro. The plagioclase
is partly to completely altered to saussurite, pyroxenes have gone over to
uralite, and hornblende is partly changed to chlorite.
Midway between Hanson and Bay Lakes a northwest-trending fault
has mylonitized the diorite over a width of about 30 feet. The mylonitc
has a porphyritic appearance with partly crushed feldspar crystals resembling phenocrysts. The fault zone is also marked by stringers and veinlets
of quartz and feldspar;
North of Botham Bay and near the east boundary of the map-area
a north-trending mineralized shear zone intersects garnet-biotite gneiss.
The zone dips 50 to 65 degrees cast. For a more detailed discussion of this
zone the reader is referred to the description of the Ramsay prospect in the
section on Economic Geology.
Minor faults with apparently small displacement are common throughout the area. Many trend north parallel to the major fault zones described
above, others fall into three general directions or sets which strike northwest, northeast, and east. The northwest and east-striking sets show left
hand strike separations, and the northeast-striking faults have right hand
strike separations. Oblique striae and grooves on fracture surfaces indicate
that nearly all the faults have a vertical component as well as a horizontal
component of movement.
Jointing is well developed in all rock types, but especially so in the
Ordovician dolomite. The joints form four sets or groups with average
strikes similar to those described in the previous paragraph on minor
faulting.
It is of interest to speculate on the age of the faulting, especially the
north-trending fault zones as they appear to have some control on the
localization of base metal mineralization. The displacement along the
faults is mainly post-folding since they cut and displace the fold-structures
and post-tectonic intrusions. The marked lineaments in the Ordovician
dolomite, which extend on strike of the fault zones for distances up to 12
miles south of Hanson Lake, would indicate some post-Ordovician movement. The vertical component of this movement must be slight, as there
is no obvious difference in the elevation of the Precambrian-Paleozoic
contact on either side of any of the larger fault zones. I t may be concluded
that most of the movement took place after the period of folding and
intrusion and before the deposition of the dolomite.
Lineation
Lineation is a common structure in all the Precambrian rocks of the
area and is best developed and most easily observed on the noses of minor
folds. The lineation finds expression in many ways, but invariably it is
-
31 -
approximately parallel to the axes of the folds, i.e. to the " b" tectonic
axis. Lineation in intrusive rocks is developed by the parallel orientation of
hornblende crystals, elongated quartz grains, and ellipsoidal plates of
biotite. In the dacitic volcanic rocks amygdules, quartz phenocrysts, and
fragments are elongated in the "b" tectonic direction.
Conformable syntectonic intrusions and massive dacitic lavas on the
crests of plunging folds often possess two distinct foliations. One is steeply
dipping and roughly parallels the axial plane of the fold, the other is
parallel to the formational trend and h as a gentle dip in the direction of
plunge. The line of intersection of the two foliations is approximately
parallel to the fold axis.
In the sedimentary band outcropping on the islands and shores of
Hanson Lake lineation in the form of elongated pebbles, streaking of
biotite, axes of small dragfolds, and lines of intersection of bedding and
foliation is in the direction of the axes of the larger folds.
Foliation
A petrofabric study of the greywacke forming the sedimentary belt in
the main section of Hanson Lake was made by Petruk (1 955) to determine
the origin of the foliation. Eight petrofabric diagrams of both biotite and
quartz were made from specimens obtained from the. troughs and limbs
of two synclines, one at the north end of the lake and the other near the
south end.
Biotite is the prevalent mafic mineral and its strong dimensional orientation produces the marked foliation of the greywacke. Most of the biotite
flakes have sh arp distinct borders and only a few are bent or strained.
Therefore, most of the biotite developed near the close of the period of
deformation. At the tops of beds the biotite flakes are often lenticular
with an elongation of up to 9X, in other places the elongation is about
3X or 4X.
The diagrams for biotite sh ow two maxima; one at "c" and the other
to one side, or they are symmetrically situated on either side of the "c"
fabric axis. The positions of the two maxima vary from IO degrees apart at
the synclin al axis to 35 degrees apart on the limbs of the folds. This
pattern suggests translation gliding of the biotite in intersecting planes
of slip under compression parallel to "c". D ifferential internal rotation of
the slip planes about the "b" fabric axis accounts for the variation in the
angle between the maxima. Megascopically the foliation is the mean
between the planes determined by the petrofabric analysis or it corresponds
to the more prominently developed plane. In the field this megascopic foliation ·parallels the fold axes and would, therefore, be referred to as axialplane flow cleavage.
Petruk (1955, p. 45) concludes that the foliation was developed by
recrystallization of biotite into intersecting planes of slip, and, to a lesser
extent, into the AB plane of the strain ellipsoid.
The eight quartz diagrams all show single girdles about the " b" axis.
This would indicate that the greywacke has undergon e only one period of
deformation produced by compressional forces acting in an east-west
direction.
-32-
ECONOMIC GEOLOGY
General Statement
Within the past four years prospecting and exploration have disclosed
the presence of four base metal deposits which under prevailing conditions
are not mineable. The principal factor is the lack of an all -weather road
connecting the Hanson Lake area to the nearest railway, i.e. Flin Flon.
If additional work discloses other deposits or enlarges the tonnage of ore at
one or more of the known deposits, then undoubtedly surface transportation would be provided. With such a road two of the known deposits could
probably be mined at a profit by shipping concentrates to the smelter at
Flin Flon.
The deposits found to date consist principally of either chalcopyritc
and sphalerite (Ramsay and Hudson Bay Exploration and Development
prospects) or sphalerite and galena (Parrex and Young prospects). Chalcopyrite and pyrite are ubiquitous minerals in the H anson Lake area. They
occur disseminated in very small quantities in all the Precambrian rocks
especially in hornblende gneiss, amphibolite, and dacite. Small quantities
of disseminated nickeliferous pyrrhotite occur in the hypersthene gabbro
and pyroxenite underlying the peninsula between Winn and Mcllvenna
Bays at the south end of Hanson Lake.
The sulphide deposits are of the high temperature replacement-type
and occur in a variety of host rocks. To date the most important of these
host rocks appears to be the tuffaceous sediments and calc-silicate rocks of
group 3 which occur intercalated with the dacitic lavas. This is especially
true for the sphalerite-galena type of mineralization. Whatever the host
rock the deposits lie within or close to north-trending faults or shear zones.
Many of the sulphide deposits do not outcrop. Data on these were
made available by Mr. A. A. Koffman, chief geologist of Hudson Bay
Exploration and Development Company, Limited, and by Mr. A. L. Parres,
consulting geologist. These deposits were located by electromagnetic
surveys and later tested by diamond drilling. They are shown on the
geologic map accompanying this report by means of black dots and a letter
or letters signifying the nature of the principal metal or mineral forming
the deposit. Known electromagnetic anomalies which h ave not been tested
by diamond drilling up to June 1957 are indicated by a series of dots
unaccompanied by any letter.
History of Pi-ospecting Activity
The first known prospecting in the Hanson Lake area was carried out
during the mid 1930's when prospectors were looking mainly for goldbearing quartz veins. Up to the end of 1952 only two deposits of interest
had been found: (1) the Young prospect on the east shore and near the
north end of Agnew Bay showed the presence of sphalerite and galena,
and (2) the Blue Bird or Wings prospect near the north end of the long
island in Bertrum Bay indicated some chalcopyrite mineralization.
In 1948 or 1949 International Nickel Company of Canada, Limited
conducted a magnetic survey of the area underlain by gabbro, diorite, and
pyroxenite at the south end of Hanson Lake. This work was not recorded
-
33 -
and the results are not known to the writer. However, as no further work
was done and the claims allowed to lapse, the survey probably did not
indicate any interesting magnetic anomalies.
During 1953 and 1954 Hudson Bay Exploration and Development
Company, Limited made an electromagnetic survey using the Boliden
horizontal-loop method. The surveyed area includes th e west half of the
main section of Hanson Lake as ·far south as the north end of Winn
Island, the peninsula and bays to the west, and west of H anson Lake as far
as Bad Carrot and Jackpine Lakes. This survey was followed up by drilling 21 diamond drill holes for a total footage of about 11,900 feet, in order
to test the better looking anomalies indicated by the survey. The results
of this work are indicated on the geological map as previously described. The
electromagnetic survey was recorded for assessment work and a plan of the
results is open to inspection at the Department of Mineral Resources.
Government Administration Building, Regina.
I n 1954, Cyprus Exploration Corporation Limited outlined a conductor at the north end of Side Lake during an electromagnetic survey of a
limited area. Three diamond drill holes which tested this conductive zone
indicated copper mineralization.
In the summer of 1954 Mr. A. Ramsay discovered a mineralized shear
in biotite-garnet gneiss on the east shore of a small lake north of Botham
Bay. Trenching indicated interesting copper-zinc mineralization, and during October, 1954, January and February, 1955, a total of 6,000 feet of
diamond drilling was done by Tombill Gold Mines Limited to investigate
the deposit at depth.
During 1956 Parrex Mining Syndicate (Trust) had a combined airborne magnetic and electromagnetic survey made of the Hanson Lake area
with the exception of the area previously surveyed by Hudson Bay Exploration and Development Company, Limited. This airborne survey indicated
several anomalies which are now being checked by ground geophysical
surveys and diamond drilling. To the end of May, 1957, two anomalies
have been tested by drilling and are shown on the geologic map. One
anomaly lies beneath the Ordovician dolomite east of Winn Bay and is
produced by a zone of talcose rock containing disseminated magnetite.
The oth er anomaly lies beneath H anson Lake about three-quarters of
a mile northwest of the entrance to Mcllvenna Bay. The drilling of this
anomaly has indicated a sulphide deposit containing appreciable amounts
of lead and zinc.
Description of Properties
Cyprus Exploration Corporation Limited (1)
Cyprus Exploration Corporation Limited controlled several large
groups of claims south and west of H anson Lake during 1954. Field work
under the direction of Mr. A. L. Parres of Flin Flon consisted of surface
prospecting, a limited amount of diamond drilling, an electromagnetic
survey of a small area in the vicinity of Side Lake, and some test-pitting
and rock trenching.
The Side Lake prospect located by the electromagnetic survey was
tested by 1,061 feet of diamond drilling in three holes over a strike length
of 1,300 feet. The mineralized zone does not outcrop but lies beneath
-34-
muskeg and water at the north: end of the lake. The drill h oles intersected a recrystallized basic tuff intruded by narrow sills of diorite. The
mineralization is confined mainly to a north-striking shear zone which
intersects the band of tuff. Pyrite, pyrrhotite, and chalcopyrite occur as
grains, blebs, and narrow stringers which parallel the foliation. Some of the
chalcopyrite is closely associated with narrow sections of porphyritized or
granitized tuff. The copper content of the zone is indicated by the following intersections from south to north: H ole No. 1-70 feet a,·eraged 0.13
per cent, Hole No. 2-14 feet averaged 0.07 per cent, and H ole No. 36.5 feet ran 0.19 per cent copper. The true width of the zone would be less
than the lengths of the above intersections as the zone is nearly vertical
and the holes dip at about 45 degrees.
. Approximately 800 feet northwest of the north end of Side Lake, a
trench in slightly fractured gabbro exposes a little copper mineralization
consisting of a few small lenses and narrow veinlets of massive ch alcopyrite.
Three-quarters of a mile northeast of Side Lake a little chalcopyrite
mineralization occurs within 200 feet of the northwest contact of the body
of granodiorite which intrudes the dacitic rocks between Side and Bad
Carrot Lakes. Development work consisted of several trenches and seven
small pits in an area with a radius of 100 feet. A small amount of disseminated chalcopyrite occurs over a 30-inch width in one trench and several
3- to 6-inch widths in four of the other pits, but no zone of mineralization
has been outlined. The bedrock consists of amphibolite cut by an irregular
body and several n arrow sills of hornblende granodiorite. The foliation of
the amphibolite strikes north and dips steeply east. It is truncated by the
irregular body of granodiorite. Both rock-types are intersected by numerous
slip joints which fall into two sets, one striking east and dipping 80 degrees
south, and the other striking north 20 to 40 degrees west and dipping
vertically to steeply southwest. The ch alcopyrite is closely related to the
narrow sills of granodiorite and appears to be genetically related to them .
. Though pyrite is present, ch alcopyrite is the predominant sulphide. It is
disseminated throughout the narrower sills and often extends for a few
inches into the amphibolite. A li ttle massice chalcopyrite occurs concentrated along some of the slip joints as thin, irregular veinlets not more than
on e-eighth of an inch wide.
Hudson Bay Exploration and Development Company, Limited
In 1954 the above company controlled by staking or option a block
of about 200 claims bounded on the west by Jackpine and Bad Carrot
Lakes, on the east by a line down the middle of H anson Lake, on the
south by a line starting one-h alf mile south of Bad Carrot Lake and
extending east to the west shore of Hanson Lake, and on the north the
claims extended three-quarters of a mile beyond the north boundary of
the map-area. Exploration consisted of an electromagnetic survey of all the
claims. This work indicated the presence of at least ten conductive zones
of which seven were tested by diamond drilling. Twenty-one holes were
drilled, having a total footage of about 11 ,900 feet. Nine of the holes
with a combined footage of 7,078 feet were drilled to test a conductive zone
lying beneath the lake at the so uth end of Bertrum Bay (Mineral showing
No. 2). In the following paragraphs a brief description will be given of the
anomalies tested by diamond drilling.
-
35-
•
The conductive zone east of the large island in the nor.th central part
of H anson Lake was tested by one diamond drill hole which intersected
44 feet of metamorphosed grcywacke well mineralized with disseminated
pyrite. The entire section was sampled and assayed for gold, silver, copper,
and zinc with negative results.
The anomaly near the centre of the long peninsula separating Agn ew
Bay from the main section of H anson Lake was tested by three diamond
drill holes along a strike length of 2,100 feet. A hole near the south end
of the conductor intersected several feet of disseminated pyrite, and one
near the north end cut 15.5 feet, 32 feet, and five feet of disseminated
pyrrhotite and pyrite. These sections were sampled and assayed for precious and base metals with negative results. A third h ole, 800 feet south
of the north end of the conductive zone, intersected 7.5 feet of disseminated
sulphides containing 1.5 per cent zinc.
The long conductive zone near the center of the main section of
Hanson Lake was tested by one drill hole. This indicated two zones of
altered and pyritized sediments. The east zone, intersected from 216 to 242
feet from the collar of the hole, contained one 5-foot section with a copper
con tent of 0.10 per cent. The west zone from 252 to 281 feet contained
one 10-foot section with 0.30 per cent zinc.
The electromagnetic anomaly near the west shore of Hanson Lake
and just south of the mouth of the creek draining Jackpine Lake was tested
by two diamond drill h oles. The south hole intersected 85 feet of altered
and pyritized dacite containing no precious or base metals. The north hole
cut 136 feet of dacite and granodiorite containin g disseminated pyrite and
pyrrhotite. Sampling and assaying of this 136-foot section indicated the
following copper content: 0.10 per cent for 1.2 feet and 0.23 per cent for
0.8 feet.
One-half mile south east of th e above zone a weak conductor near the
west shore of the island in Bertrum Bay was tested by one drill h ole.
A 22.3 foot section from 286.4 to 308.7 feet contained a little disseminated
chalcopyrite. One 3.4-foot section assayed 0.37 per cent copper. The
copper content of the remainder of the zone is very low.
The conductive zone lying about 2,000 feet south of Bertrum Bay was
tested by one diamond drill hole which cut 135 feet of altered and mineralized basic tuff and dacite intruded by n arrow bodies of diorite. Mineralization consists of disseminated pyrite and pyrrhotite. One 0.6-foot section of
core assayed 0.18 per cent copper, and several sections contained a little
zinc, the best being a 4.0-foot length of core with 0.50 per cent of the metal.
The conductor underlying the south end of Bertrum Bay (showing
No. 2) was tested by n ine diamond drill holes over a strike length of
1,500 feet, see Figure 2, and to a vertical depth of 600 to 700 feet. This
drilling indicates that sulphide mineralization occurs in a series of small
lenses within a zone of weak sh earing approximately 400 feet wide and at
least 1,500 feet long. The best mineralized lens is between 100 to 200 feet
long, a little over 20 feet wide, and has an average grade of 0.25 per cent
copper and 1.5 per cent zinc.
-36 -
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Figure 2. Plan of diamond drill holes and Ycrtical projection of zones of sulphide
mineralization. Mineral showing No. 2, H udson Bay Exploration a nd Development Company, Lim ited.
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37 -
The rocks outcropping around the bay are mostly garnetiferous dacite
showing fragmental and flow banded structures. A few narrow dykes and
sills of quartz-feldspar porphyry and diorite intrude the lavas. The trend
of the foliation is north 15 degrees west and the dip is vertical. A weak
mineral lineation plunges 30 degrees south. A trench on the east side of the
bay exposes 12 feet of highly fractured dacite contai ning a little chalcopyri te and some malachite. The fractures strike n orth 5 degrees east and dip
80 degrees east. Elsewhere there are two sets of vertical joints, one set
striking north 58 degrees east and the other south 80 degrees east.
t
The d iamond drilling revealed the rocks under the bay to be in terlayered dacite and daci tic tuff intruded by narrow bodies of diorite, and
near the south end of th e zone by quartz porphyry. Mineralization is confin ed mainly to a weak, north-trending, steep-dipping shear zone which
intersects t he lavas and tuff.
The principal sulphides are pyrrhotite and pyrite, which mainly occur
disseminated th roughout the zones and less commonly as massive lenses a
few inches to several feet wide. Sphalerite, ch alcopyrite, and arsenopyrite
occur in minor amounts. Sphalerite and ch alcopyrite form irregular and
rounded grains and small blebs which are mainly included in the pyrrhotite and pyrite. In addition, ch alcopyrite frequen tly forms small, irregular
veinlets cutting the other sulphides and the gangue minerals. The arsenopyrite occurs as a few scattered subhedral to euhedral crystals. The study of
10 polished sections indicates the order of deposition from oldest to youngest to be as follows : Pyrite and arsenopyrite, quartz, sphalerite, pyrrhotite,
ch alcopyrite, a period of fracturing and introduction of late quartz and
pyrite, (Clark, 1956, p. 35). Alteration of the original dacitic rocks occurs
only within the mineralized zones and consists of a gen eral silicification
wi th minor sericitization and chloritization of the original rock forming
minerals.
Parrex Mining Syndicate (Trust)
This syndicate in June 1957 held over 1,270 claims in the vicinity of
H anson Lake. These included most of the ground formerly controlled by
Hudson Bay Exploration and Development Company, Limited, plus additional ground to th e west and south of H anson Lake. Initial prospecting
consisted of an airborne magnetic and electromagnetic survey of the area
not covered by the ground electromagnetic survey carried out in 1953 by
Hudson Bay Exploration and D evelopment Company, Limited. The airborne survey indicated a number of anomalies which are in progress of
being checked by electromagnetic ground surveys and tested by diamond
drilling. T wo anomalies which h ad been tested by the end of May, 1957
are shown on th e geological map accompanyi ng this report. One lies
beneath the Paleozoic sedimen ts about one mile east of the south end of
Winn Bay. The other, mineral showing No. 3, is about 600 feet east of
the west shore of H anson Lake and one-h alf mile northwest of the
entrance to Mcllvenn a Bay.
The conductive zone east of W inn Bay is associated with a marked
magnetic anomaly. Several diamond drill h oles reveal that the anomalies
are related to a zone of talc-chlorite schist containing disseminated magnetite and cutting post-tectonic gabbro and pyroxenite. Microscopic examination of thin sections of the core indicates that the talc-chlorite schist is an
alteration product of the intrusive rocks.
-38 -
•
Mineral showing No. 3 which lies beneath H anson Lake about 600
feet east of the shore was located by the airborne survey, and, up to the
end of May, 1957, had been investigated by drilling 12 holes over a length
of 1,000 feet. This work has indicated the presence of high grade lead-zinc
ore in wh at appears to be a number of individual lenses along a zone of
shearing cutting a recrystallized tuff. Additional detailed diamond drilling
will be required to determine the extent of these lenses or lens.
The syndicate has made public the data on three holes, spaced
over a length of 600 feet, as follows:
Core length
in feet
10.0
26.2
11.0
Gold
oz. / ton
0.034
0.036
0.06
Silver
oz/ ton
2.93
5.6
3.1
Copper
per cent
1.33
0.9
1.18
Zinc
per cent
19.21
20.5
23.1
Lead
per cent
9.95
15.9
14.8
True widths are less than core lengths as the ore appears to dip vertically and the holes were drilled at angles of 50 to 60 degrees to the
horizontal.
The w riter visited the property in June, 1957 and examined in detail
the cores from four h oles. Four polished sections and 15 thin sections were
prepared from specimens of core collected at the time of the vis it.
The ore zone lies within a 100 to 250-foot wide ban d of recrystallized
tuff interla.yered between dacitic lavas and intruded by a sill-like body of
quartz-feldspar porphyry (8) similar to that underlying the peninsula to
th e north. The form ations strike north and dip vertically. A section from
east to west across the zone in the vicinity of hole number 1 would show
the following sequence: dacite, tuff, quartz- feldspar porphyry, tuff, quartzscricite-fuchsite schist with minor sulphides (I 0-15 feet), nearly massive
sulphides (7-10 feet), tuff, and dacite.
The dacite is typically very fine to fine grained, massive to irregularly
flow banded, and grey in colour. Some sections are porphyri tic with onesixteenth to one-eighth inch phenocrysts of white feldspar and grey quartz.
The rock is poorly foliated unless considerable biotite is present, then the
foliation is emph asized by paper-th in streaks of black biotite. Miscroscopically, the dacite is similar to the dacitic lavas described under volcanic
rocks (1).
The tuff is fine to coarse grained and usually well banded in shades of
grey and green. The bands range in thickness from one-quarter inch to
eight inches, and some of the thicker beds contain an gular to elliptical,
light coloured fragments up to a maximum size of two inches. Microscopically, the tuff is similar to the pyroclastic rocks (3c), and consists of variable
amounts of altered plagioclase, actinolite, biotite, chlorite, and sericite with
accessory garnet, calcite, magnetite, and h ematite.
Megascopieally and microscopically the quartz porphyry is similar to
the quartz porphyry (8) wh ich outcrops on the peninsula to the west and
north of the anomaly. It is fine to medium grained with one-eighth to onequarter inch phenocrysts of white and pink feldspar and grey opalescent
quartz in a massive grey groundmass wh ich, in the medium-grained facies,
is speckled with flakes of black biotite.
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•
The quartz-sericite-fuchsite schist forms the wall rock on the east side
of the massive sulphides and represents an altered facies of the tuff into
which it grades. The schist is very fine grained, highly foliated, and banded in shades of grey and grey-green. Thin sections show that the grey
bands consist essentially of sericite and quartz with minor amounts of
biotite, chlorite (penninite), garnet, and sulphides. The grey-green bands
in add ition contain a bright green, micaceous mineral tentatively identified
as fuchsite on the basis of refractive indices and optic angle: Nx=l.56 1.57, NY= l.59-1.60, NZ= l.60-1.61, optic angle (- ) about 42 degrees.
T he sulphide minerals are pyrite, pyrrhotite, sphalerite, galena, and ch alcopyrite. T hey occur as grains and crystals or in narrow veinlets which
parallel and cut across the foliation. Pyrite in the form of cubes an d octahedrons shows a preference for bands containing biotite. I t is bordered and
replaced by pyrrhotite, sphalerite, galena, and ch alcopyrite. Blebs and
stringers of sph alerite, galena, and chalcopyrite break across and distort the
foliation produced by the parallel alignment of sericite, chlorite, and
biotite. The galen a and chalcopyrite cut and replace the sphalerite, and
the galena in turn is bordered and replaced by ch alcopyrite. The assay
results show that in places along the zone there are sufficient quantities
of lead and zinc to make ore grade material.
The zone of main sulphide mineralization consists of nearly massive
sulphides made up mainly of fine-grained, dark-brown sphalerite and
galena with minor variable amounts of arsenopyrite, pyrite, pyrrhotite, and
chalcopyrite. Argentitc and tetrahedrite were detected in one of the
polished sections.
The arsenopyrite occurs as euhedral crystals and very fine-grained,
compact aggregates. It is highly fractured and is cut and replaced by the
other sulphides with the exception of pyrite. The relationship of pyrite and
arsenopyrite is unknown as the two minerals were not observed in contact.
Pyrite, however, was probably formed at about the same time, as it too is
cut and replaced by pyrrhotite, sphalerite, galena, and chalcopyrite which
were deposited in the order named. Both arsenopyrite and pyrite are cut
by quartz, sericite, and chlorite. However, sphalerite, galena, and chalcopyrite vein and replace these gangue minerals. Argentite is closely associated with galena and they appear to have been deposited simultaneously.
Multi-grain aggregates of quartz form small elliptical to rounded blebs
which give a spotted appearance to the ore. Microscopically the quartz
grains have simple to sutured intergrain boundaries and are only slightly
strained. Nearly all the blebs observed under the microscope contain sphalerite as minute veinlets along the intergrain boundaries and as individual
grains, 0.01 millimeters in diameter, en tirely within the quartz. Other
ganguc minerals include sericite, biotite, chlorite (penninite), a colourless
garnet, and fuchsite.
The contact between the sulphides and the tuffaceous wall rock on the
west side of the ore zone is relatively sharp. A few veinlets of massive
galena or coarse-grained chalcopyrite and pyrite continue out into the wall
rock for a distance of two to three feet. Actinolite and biotite are partly
altered to chlori te for a distance of 25 feet from the ore.
Ramsay Showing (4)
T h is showing lies along the east shore of a small lake just north of
Botham Bay in the northeast corner of the map-area.
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Figure 3. Plan of trenches and diamond drill holes with vertical projection a nd depth
of sulphide intersections. Mineral showing No. 4, Ramsay prospect.
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41-
The mineralized zone was found, staked, and trenched by Mr. D. A.
Ramsay in the summer of 1954. The property was then optioned by
Tombill Gold Mines Limited. After additional trenching and 6,000 feet of
diamond drilling in 23 holes, see Figure 3, which tested the zone for a
strike length of 1,400 feet and to a vertical depth of 400 feet, the company
dropped their option and the claims reverted to Mr. Ramsay in 1955.
During 1956 Mr. Ramsay did some more trenching which extended
the zone an additional .1,000 feet to the north of the original showing on
the shore of the lake.
The exploratory work to date has indicated a body of copper-zinc
mineralization about 850 feet long. The results of the diamond drilling
suggest the deposit may be a lens which plunges southeast parallel to the
plunge of the folds in the gneiss. According to an unpublished report by
Mr. John H. Low, consulting geologist, dated February 17, 1955, the
average grade of this body is 1.70 per cent copper and 3.13 per cent zinc,
and the average true thickness is 4.4 feet.
The bedrock in the immediate vicinity of the showing consists of
biotite-garnet gneiss with a few narrow bands of intercalated h ornblende
gneiss and amphibolite. Aplite and pegmatite intimately intrude the gneiss
in the form of narrow sills, lenses, and blebs usually not more than four
inches thick, although a few sills of pegmatite attain a width of 10 feet.
The gneiss is tightly folded into small isoclinal folds which strike north
and are overturned to the west. The average dip of the limbs is 65 degrees
east, and the plunge of the fold axes is 35 to 40 degrees-south 20 degrees
east. The general trend of the foliation is north with a variable dip between
40 and 75 degrees to the east.
The copper-zinc mineralization is confined to the hanging wall side
of a moderately strong shear zone which roughly follows the trend of the
gneissosity and has an average dip of 50 degrees east. The diamond drilling
indicates there are local rolls in both the hanging wall and the footwall ,
and accordingly th e dip varies from 40 to 65 degrees. The thickness of the
shear zone is also variable from 20 to 70 feet. Within this zone the biotitc
and hornblende of the gneiss is partly altered to chloritc, variety penninite.
Chalcopyrite and sphalerite are closely related to a plagioclase-rich pegmatite which forms sill-like bodies from three inches to 10 feet thick. This
rock is composed of grey to light greenish grey oligoclase with minor
quartz and a small amount of biotite. As observed in the trenches, pyrite.
pyrrhotite, sphalerite, chalcopyrite, and cpvellite are most abundant in the
sheared gneiss and the pegmatite where the latter rock is in bands not
over three feet thick. The sulphide minerals either replace the primary
rock-forming minerals as massive, intergranular fillings, or they form small
stringers and veinlets which occupy fractures cutting the pegmatite and
gneiss.
The study of polished sections revealed the following order of sulphide
emplacement from early to late in the sequence of mineralization: pyrite
sphalerite, chalcopyrite, and covellite. The covellite occurs in many places
throughout the zone of sulphide mineralization as blue-black to deep
indigo-blue grains which become a d~ep purple when wet. In polished
sections it was observed replacing chalcopyrite and to a greater extent
sphalerite. Besides the sulphide minerals a few flakes of native copper were
observed along minute fractures cutting the plagioclase-quartz pegmatite.
-42-
In addition to th e mineralized zone described above, two other zones
are known to occur. O ne lies about 200 feet east of the south end of the
main zone. It outcrops as a poorly exposed, untren ched patch of gossan.
Diamond drilling indicated a narrow zone containing some copper and
zinc. The other zone outcrops 1,000 feet west of the main zone and about
650 feet north of the lake. It outcrops as a zone of gossan striking n orth
along the east ma,gin of an outcrop of biotite gneiss. Where exposed the
zone is about ten feet wide and h as been explored by three small trench es
over a length of 45 feet. The mineralization consists of dissemin ated pyrite
and a very small amoun t of ch alcopyrite.
Wings or Blue Bird Prospect (5)
This showing in the northern h alf of the long island in Bertrum Bay
was discovered and staked by Mr. S. C. Simpson of Cranberry Portage,
Manitoba in 1935 under a prospecting agreemen t with The Consolidated
Mining and Smelting Company of Canada, Limited. T he original claims
were known as the W ings. Trenching the following year showed erratic
distribution of copper and the claims were allowed to lapse in 1938. Subsequently the ground was restaked as the Blue Bird, Katie, and Marie
claims by Mr. Ch arl ie Young of Flin Flon. In 1954 they were under option
to Hudson Bay Exploration and Development Company, Limited, but the
option was dropped in 1956. In 1957 the claims were under option to
Parrex Mining Syndicate (Trust) .
The ch alcopyrite mineralization occurs in a band of actinolite- biotited iopside-garnet gneiss (3 b) which is intruded by a few n arrow dikes and
sills of highly altered d iorite. Chalcopyrite is the principal sulphide mineral,
and there are traces of it in every trench over a width of more than 100
feet, but the total amount is very low. The ch alcopyr ite is mostly associated
with the bands of actinolite-diopside-garnet rock and occurs as grains, an d
widely spaced stringers which are seldom over one-sixteen th inch wide.
In a few places the rock con tains up to four per cen t chalcopyrite, but this
is unusual. Besides chalcopyrite the zone also contains some disseminated
magnetite and pyrite, and a few quartz veinlcts with ch alcopyrite and
pyrite. The microscopic exa mination of polished sections showed the presen ce of sph alerite. Supergene minerals include malach ite, and some
azuri te and hematite along joint and slip planes.
In 1954 the H udson Bay Exploration and Development Company,
Limited drilled a hole beneath the trenched area. This hole intersected 38
feet of erratic copper mi neralization. The best sample was a 0.8-foot section
wh ich assayed 1.15 per cen t copper and 0.5 per cent zinc. H owever, the
hole did not completely cross the zone, and did not reach th e downward
projection of the western section of the zone which contains the better
m ineralization as exposed on the surface.
Young Showing
A showing of galena and sphalerite is located on the east side of
Agnew Bay just north of the northern edge of the map-area. The
property, known as the Blackie group of claims, is owned by Mr. Charlie
Young, a Flin Pion busin ess man. I n 1954 the claims were under option to
Hudson Bay Exploration and Development Compan y, Limited. The com-
43 -
pany carried out an electromagnetic survey of the claims and diamond
drilled two conductive zones, but did no work on the original showing.
The option lapsed and Mr. Young retained ownership of the claims. In
1957 the claims were under option to Parrex Mining Syndicate (Trust) .
Although the anomalies drilled by Hudson Bay Exploration and
Development Company, Limited are not with in the present map-area but
lie just to the n orth of it, a brief description of them ..,ill nevertheless be
given. One conductor underlies the main section of H anson Lake 2,000
feet east of the west shore and 1,400 feet from the north end of the lake.
This conductive zone coincided with a magnetic anomaly. It was tested by
one diamond drill h ole which intersected 40 feet of metamorphosed sediments well mineralized with magnetite. The other anomaly lies 200 to
300 feet west of the shore at the north end of the lake. This conductor was
tested by one drill hole which intersected 30 feet of dissem inated pyrite.
The assays of core samples indicate that the zones contain no precious
metals, copper, or zinc.
The original showing near the east shore of Agnew Bay was explored
some years before 1954 by trenching and test-pitti ng. A trench runs eastwest across the zone of mineralization, it is 60 feet long, fi ve to 10 feet wide,
and the depth va ries from three feet at the west end to 25 feet at the east
end. The trench exposes a band of actinolite-biotite-diopside-garnet gneiss
(3 b) . The gneissic banding stri kes north IO degrees cast and dips SO to
75 degrees east. A few one-eighth to one-half inch wide quartz stringers
and lenses occupy fractures which ro ughly parallel the ba nding. At the
east end of the trench the gneiss is cut by a north-striking fa ult and fractured over a width of six inches. Some of the fractures contain stringers of
massive sphalerite and some dissemina ted galena. Near the centre of the
trench the tuff is again fractured over a n arrow wi dth, a nd a few of the
Fractures are filled with massive sphalerite and galena.
The spha lerite is a dark brown to black, iron-r ich variety. The only
other sulphide noted was a little pyrrhotite. Microscopic study shows that
the sulphides replace the actinolite and biotite of the h ost rock along
intergrain boundaries. Adj acent to the sulphides the origin al plagioclase is
highly saussuritized and the ferro-magnesian minerals are chloritized to
penninite. The sulphides were deposited in the following order: pyrrhotitc,
sph alcrite and galena (youngest).
A second trench exposes the gneiss (3b) just before it goes under the
water of Agnew Bay at a point 1,700 feet south of the a bove showing. Herc
the rock is sparsely mineralized with very fine-grained, disseminated
pyrite and a little ch alcopyrite.
Another trench on the opposite side of the peninsula and a bout 700
feet west of the shore of H anson Lake exposes a IS-foot section of pyritized
calc-silicate rock close to its contact with greywacke on the east. This
pyrite mineralization is the southern extension of the zon e which produced
the second electromagnetic anomaly at the northwest en d of the lake as
described above.
-44-
Plate 1
Figure I.
Dacite, flow breccia. South shore Agnew Bay, Hanson Lake.
Figure 2.
Dacite, flow banding. Ea t side of Bertrum Bay, H anson Lake.
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45-
Plate 2
Figure 1.
Contact between dacite (right) and tuff (left). East of Bertrum Bay, Hanson Lake.
Figure 2.
Interlayered tuff and agglomerate beds. Grain gradation indicates tops towards top of
picture. East shore Bertrum Bay, Hanson Lake.
- 46 -
Plate 3
Figure 1.
Contact between Winnipeg sandstone and overhanging Red River dolomite. Just west
of entrance to Mcllvenna Bay, Hanson Lake.
Figure 2.
Winnipeg sandstone, illustrating its unconsolidated character. Just west of entrance
to Mcllvenna Bay, Hanson Lake.
-47-