JOURNAL OF PETROLOGY
VOLUME 44
NUMBER 11
PAGES 2081±2112
2003
DOI: 10.1093/petrology/egg071
An Isotope and Trace Element Study of the
East Greenland Tertiary Dyke Swarm:
Constraints on Temporal and Spatial
Evolution during Continental Rifting
K. HANGHéJ*, M. STOREY AND O. STECHER
DANISH LITHOSPHERE CENTRE, éSTER VOLDGADE 10, 1350 COPENHAGEN K, DENMARK
RECEIVED SEPTEMBER 4, 2000; ACCEPTED MAY 26, 2003
Dykes of the East Greenland Tertiary dyke swarm can be
divided into pre- and syn-break-up tholeiitic dykes, and postbreak-up transitional dykes. Of the pre- and syn-break-up
dykes, the most abundant group (Tholeiitic Series; TS) has
major element compositions similar to the main part of the East
Greenland flood basalts. A group of high-MgO tholeiitic dykes
(Picrite---Ankaramite Series; PAS) are much less common, and
are equivalent to some of the oldest lavas of the East Greenland
flood basalts. Isotopic compositions of the TS and PAS dykes
partly overlap with those for Iceland, but Pb isotopic compositions extend to less radiogenic values than those seen in either
Iceland or North Atlantic mid-ocean ridge basalt (MORB).
The isotopically depleted source required to account for this
isotopic variation is interpreted as subcontinental lithospheric
mantle with low 87 Sr/86 Sr and 206 Pb/204 Pb and high eNd. The
post-break-up Transitional Series (TRANS) dykes are isotopically distinct from Iceland and MORB, and are interpreted
as the products of contamination of Iceland plume melts with
continental crust. Comparison of the Nd---Sr---Pb isotopic and
trace element compositions of dykes from different segments of
the East Greenland margin indicates that there is no systematic
compositional change with distance from the presumed protoIcelandic plume centre. This suggests that a northwardincreasing crustal thickness observed offshore may be attributed
to active upwelling rather than a systematic rise in temperature
towards the plume centre.
KEY WORDS:
melting
isotopes; trace elements; mantle sources; mantle
*Corresponding author. Present address: Woods Hole Oceanographic Institution, G&G, MS# 8, Woods Hole, MA 02543, USA.
Telephone: ‡1 (508) 289 2946. Fax ‡1 (508) 457 2183. E-mail:
[email protected]
INTRODUCTION
The East Greenland Tertiary Igneous Province is part
of the rifted volcanic margin related to the opening of
the North Atlantic Ocean (Fig. 1). The province comprises flood basalts, mafic and felsic intrusive centres,
and a coast-parallel dyke swarm, which is exposed for
more than 500 km along the present coastline. Offshore
from the province, a thick seaward-dipping reflector
sequence (SDRS), which was drilled by Ocean Drilling
Program (ODP) Legs 152 and 163, consists of voluminous subaerially erupted basalt flows (e.g. Larsen &
Saunders, 1998). The Greenland---European continent
that was rifted during the Tertiary consists of rocks
ranging in age from early Archaean to late Mesozoic.
In Greenland, the Caledonian front marks the western
extent of deformation associated with the Caledonian
orogeny as Greenland and Europe collided in
Silurian---Devonian time. The basement west of the
Caledonian front (Fig. 1) consists of Archaean blocks
and Proterozoic mobile belts (e.g. Escher & Watt,
1976; Bridgwater et al., 1978) whereas east of the
Caledonian front it consists of deformed Precambrian
basement and early Palaeozoic sedimentary and
igneous rocks (Henriksen & Higgins, 1976).
In the North Atlantic region, active volcanism is at
present restricted to the Mid-Atlantic Ridge. Iceland
represents an area of high magma supply associated
with the thermal and compositional anomaly generally
referred to as the Iceland hotspot or mantle plume
(Fig. 1). Some plate tectonic reconstructions place the
Published by Oxford University Press
JOURNAL OF PETROLOGY
VOLUME 44
NUMBER 11
NOVEMBER 2003
Fig. 1. Distribution of onshore and offshore basalts in the North Atlantic Igneous Province. ODP drill sites on the Greenland margin are
shown. FIGR, Faeroe---Iceland---Greenland Ridge; JMR, Jan Mayen Ridge. Selected sea-floor magnetic anomalies are shown by dashed lines.
Iceland hotspot beneath central Greenland during the
time of break-up, but the timing and exact location for
the initial impact of the Iceland plume is subject to
different interpretations. Lawver & M
uller (1994) proposed that the Iceland plume dates back as far as
the Permo-Triassic, and placed the centre of the
hotspot beneath central West Greenland at 60 Ma,
and beneath central East Greenland around 40 Ma
(Fig. 2). Brooks (1973), White & McKenzie (1989)
and Saunders et al. (1997) proposed that the arrival
and emplacement of the plume head preceded the riftrelated volcanism in the North Atlantic, and placed
the hotspot under central East Greenland (the
Kangerlugssuaq area) before initial break-up at
58---60 Ma.
The East Greenland margin is thus potentially an
early manifestation of the Iceland mantle plume.
Igneous rocks exposed along the margin provide a
unique possibility to examine how the proto-Icelandic
plume interacted with the lithosphere as break-up
proceeded, and whether other mantle sources [e.g.
mid-ocean ridge basalt (MORB) source mantle and
continental lithospheric mantle] were involved in the
melt generation. The East Greenland margin can also
potentially provide information about the compositional and thermal structure of the Iceland plume at
the time of break-up, because of the good temporal and
spatial control and exposure of different structural
levels.
This study documents and examines the geochemistry of the East Greenland coastal dyke swarm, a major
expression of the break-up-related magmatism. In general, the dykes represent magmas that are equivalent to
the flood basalts erupted at the surface. However, as
the dykes occur in areas outside the area covered by
flood basalts, some dykes may have no preserved eruptive equivalents. This study is complementary to continuing studies of the East Greenland lavas (e.g. Larsen
et al., 1996a; Pedersen et al., 1997; Tegner et al., 1998b)
by extending, both geographically and temporally,
information about the nature of magmatism along
the rifted margin before, during and subsequent to
break-up. We present new major and trace element
data for 115 dykes, and Sr, Nd and Pb isotope data
for a representative selection of the dyke samples. The
main aim of the chemical and isotopic study is to
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HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Fig. 2. Map showing the localities studied in this work and the three main segments of the dyke swarm after Myers (1980). Proposed hotspot
track of Lawver & M
uller (1994) is shown on insert map of Greenland, with numbers indicating location at time in million years.
identify the mantle sources for magmas generated during formation of this volcanic rifted margin, and to
place constraints on the temporal and spatial variations in magma chemistry.
THE EAST GREENLAND DYKE
SWARM
Field relations and sampling
The coastal dyke swarm of the East Greenland margin
was first described by Wager (1935, 1947), and subsequently by Nielsen (1978) and Myers (1980), and most
recently by Klausen & Larsen (2002). It consists of an
10---30 km wide zone along the present coastline,
where coast-parallel dykes constitute up to 450% of
the outcrop. The swarm is most dense from Cape
Wandel north of Ammasalik to Nansen Fjord just
north of Kangerlugssuaq Fjord, although Tertiary
dykes are present north of Nansen Fjord and at least
as far south as Skjoldungen, some 400 km south of
Ammasalik (Fig. 1). The offshore extension of the
dyke swarm is unknown, but as the frequency of
dykes generally increases seawards, the most intense
zone of dyking is probably located offshore.
Typically the dyke density decreases from more than
50% on the outer coast to less than 5% some
20---30 km inland. Locally, sheeted dykes with dyke
densities 490% occur. Associated with the rifting, a
large monocline structure [the coast-parallel flexure of
Wager & Deer (1938)] developed along the entire
margin, causing seaward rotation of fault blocks with
resultant landward dip of dykes, as pointed out for the
Kangerlussuaq region by Nielsen (1978) and Nielsen &
Brooks (1981). Progressive rotation has ensured that
dykes on the outer part of the coast are rotated more
than dykes further inland, and that early dykes are
rotated more than late dykes. The development of the
monocline structure was accommodated by Tertiary
normal faulting at various scales, ranging from slip
along dyke margins to large fault zones with associated
cataclasite and pseudotachylyte formation (Karson
et al., 1998).
Four localities were chosen for detailed geochemical
work, and these are (from south to north) Tasiilaq,
Langù, Fladù and I. C. Jacobsen Fjord (Fig. 2). At
these localities, collection of representative samples was
accomplished through detailed mapping for crosscutting relations and sampling in different parts of the
swarm, i.e. the most inland part where the dyke density
is less than 5%, the middle part with intermediate dyke
2083
JOURNAL OF PETROLOGY
VOLUME 44
densities, and the outer part where dyke densities reach
more than 50%.
Analytical methods
Most dykes were sampled close to the margin, i.e. in
the most fine-grained portion of the dyke. Weathered
surfaces were removed before the samples were crushed
in a jaw crusher and then powdered to approximately
200 mesh in an agate shatter box.
The dykes were analysed for major elements by
the GEUS (Geological Survey of Denmark and
Greenland) laboratory in Copenhagen. SiO2, TiO2,
Al2O3, Fe2O3, MnO, MgO, CaO, K2O and P2O5
were determined by X-ray fluorescence (XRF) on
fused beads. Na2O was analysed by atomic absorption
spectrometry, and FeO by titration as described by
Kystol & Larsen (1999). Some trace element abundances (Zn, Cu, Co, Ni, Sc, V and Cr) were determined by XRF on pressed powder tablets at the
Geological Institute at University of Copenhagen.
For additional trace element concentrations, the dykes
were analysed by inductively coupled plasma mass
spectrometry (ICP-MS) (Fisons PQ2‡ PlasmaQuad)
at the College of Oceanography and Atmospheric
Sciences, Oregon State University, using a digestion
procedure involving fusion of the samples to ensure
that possible residual phases, such as zircon and chromite, were completely dissolved. Sample solutions were
prepared by fusing 200 mg of whole-rock powder
with 800 mg of lithium-metaborate flux in graphite
crucibles at 1100 C, and dissolving the resulting
glass bead in 50 ml of 2N HNO3. Before analysis, the
samples were further diluted with 1% HNO3 in proportions 1:10. Instrumental drift was corrected using
internal standard solutions added to the sample solutions as described by Pyle et al. (1995). Element concentrations for the samples were determined from
regression curves for rock standards processed along
with the samples [BHVO-1, BIR-1, BR or BE-N,
W-2; using recommended values from Govindaraju
(1989, 1994) and Cheatham et al. (1993)]. The reproducibility of a monitor sample, which was analysed at
least three times for every 20 samples, is 6% or less for
most elements.
Thirty-two of the samples were analysed for Sr, Nd
and Pb isotope compositions on a VG-354 multicollector mass spectrometer at the Danish Centre for
Isotope Geology at the University of Copenhagen.
These were selected to ensure a range of compositions
within each group, and to avoid altered samples (on
petrographic criteria) and those obviously contaminated with continental crust (e.g. samples with anomalously high SiO2 contents and La/Nb ratios). Samples
selected for isotope analyses were acid-leached
NUMBER 11
NOVEMBER 2003
following the multi-step HCl-leaching procedure
described by Mahoney (1987), with the aim of eliminating all secondary phases. Results are given in
Tables 1 and 2.
CLASSIFICATION AND
CHRONOLOGY OF DYKES
This study uses a modified version of the classification
proposed by Nielsen (1978), Gill et al. (1988) and
Hansen (1997), based on field relations and major
element chemistry. The dykes analysed in this study
can be divided into three main groups, the Tholeiitic
Series (TS), the Picrite---Ankaramite Series (PAS), and
the Transitional Series (TRANS) (Fig. 3). Importantly, the distinctions between these groups are not
very rigorous. All three groups have a range of compositions, and some dykes are intermediate between the
groups. This is especially true for dykes of the Transitional Series and Tholeiitic Series.
Tholeiitic Series (TS)
These dykes, in terms of major elements, are similar to
most of the flood basalts and specifically to some lavas
from the oldest part of the flood basalt sequence, the
Lower Basalts (e.g. Gill et al., 1988; Larsen et al., 1989;
Hansen, 1997). The TS dykes in this study are further
divided into high Zr/Nb TS dykes and low Zr/Nb TS
dykes (Fig. 4) on the basis of their trace element compositions. With the exception of one low Zr/Nb TS
dyke, all TS samples are hypersthene normative.
Dykes of the TS constitute more than 70% of the
dyke swarm at all localities. They are typically 2---20 m
wide and strike roughly parallel to the coast at all
localities. They generally dip 60 to 70 landward
and they tend to be wider and more steeply dipping
in the regions furthest from the coast. Crosscutting
relations within the TS dykes are common, and show
that the low Zr/Nb TS dykes generally are younger
than the high Zr/Nb TS dykes, although they in some
cases appear to be contemporaneous.
Petrographically there is no obvious difference
between high Zr/Nb TS dykes and low Zr/Nb TS
dykes. Both types are typically medium- to coarsegrained dolerites, with ubiquitous plagioclase, clinopyroxene, olivine and Fe---Ti oxide minerals. Low
abundances of plagioclase and/or olivine phenocrysts
are common, but phenocryst-rich types are rare.
Plagioclase, clinopyroxene and oxide minerals are
generally not altered. Partly fresh olivine phenocrysts
are very rare, and groundmass olivine is always completely replaced. The most common secondary phases
are chlorite, sericite and epidote.
2084
HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Table 1a: Major and trace element analyses of Tholeiitic Series dykes
410630
410631
410632
410637
410638
410639
410662
410663
410669
410683
417364
417366
417368
417370
417383
417384
417386
SiO2
46.73
48.03
48.38
48.26
47.06
48.38
48.32
48.75
48.18
47.30
45.58
47.76
47.92
47.67
48.32
47.74
47.60
TiO2
2.39
2.39
2.40
2.35
2.00
2.07
1.46
2.58
2.15
2.28
4.37
3.64
2.94
3.64
3.07
2.98
3.78
Al2O3
13.96
13.95
13.97
14.17
14.86
13.95
15.51
13.88
13.68
14.97
11.61
12.57
13.08
12.53
13.07
12.87
11.88
Fe2O3
3.63
2.67
2.71
2.68
1.87
2.50
2.19
2.66
3.49
1.81
2.16
3.59
2.51
3.47
3.21
2.21
3.41
FeO
9.44
9.42
9.47
9.71
9.00
9.57
8.31
10.69
9.06
10.62
14.86
11.58
12.18
11.84
11.40
12.55
13.30
MnO
0.21
0.18
0.19
0.19
0.18
0.19
0.17
0.21
0.21
0.20
0.24
0.22
0.23
0.22
0.22
0.23
0.23
MgO
7.23
6.67
6.66
6.75
8.09
7.12
7.35
5.79
6.64
6.32
5.76
5.48
6.07
5.48
5.19
6.09
5.34
CaO
11.42
11.79
11.80
11.70
12.48
12.25
12.46
10.73
11.52
10.89
9.36
10.06
10.96
10.09
9.60
10.84
9.52
Na2O
2.48
2.53
2.32
2.34
1.97
2.13
2.14
2.43
2.56
2.59
2.34
2.47
2.45
2.47
3.19
2.42
2.54
K2O
0.40
0.27
0.16
0.28
0.31
0.19
0.20
0.21
0.29
0.20
0.31
0.78
0.42
0.79
0.74
0.47
0.49
P2O5
0.25
0.25
0.26
0.26
0.16
0.20
0.13
0.27
0.22
0.23
0.35
0.41
0.33
0.42
0.35
0.33
0.40
Vol.
1.69
1.47
1.25
1.40
2.10
1.19
1.53
1.67
1.86
2.25
2.85
1.33
1.23
1.34
1.34
1.08
1.36
Total
99.83
99.62
99.56
100.07
100.07
99.75
99.78
99.86
99.85
99.67
99.79
99.89
100.31
99.95
99.70
99.79
99.84
wt %
ppm
Sc
43
34
35
35
40
42
37
35
39
31
41
28
34
29
34
38
36
V
375
339
343
341
350
354
282
350
383
361
662
411
349
416
445
380
543
Cr
206
202
208
213
281
199
230
85
181
94
71
51
68
56
27
73
66
Co
57
51
51
51
54
51
48
51
50
54
79
61
97
66
63
68
71
Ni
96
83
84
91
131
96
100
59
83
91
86
52
61
53
41
62
66
Cu
187
158
154
164
183
141
143
234
222
178
254
266
221
261
158
246
244
Zn
113
105
116
117
89
114
79
100
98
112
142
131
144
135
159
126
150
Rb
8.64
3.00
5.31
5.65
3.78
7.43
4.94
5.25
5.15
3.83
13.46
7.68
13.03
14.16
10.62
Sr
323.50
9.53
282.38
271.03
308.90
282.36
196.26
199.98
253.80
211.82
236.41
261.37
311.65
256.42
310.98
323.68
281.08
315.23
Y
32.04
28.12
28.07
27.99
20.39
29.26
25.97
39.97
36.52
31.13
32.38
34.73
33.72
34.53
38.33
37.84
40.54
Zr
156.01
148.50
147.72
146.42
86.53
133.09
83.65
162.55
140.57
150.55
179.72
192.97
158.47
190.80
220.32
173.78
254.15
Nb
14.10
13.60
13.59
13.80
8.38
13.74
8.49
14.20
15.19
12.22
9.85
15.88
12.06
14.84
20.58
16.73
14.03
Ba
111.74
84.79
73.54
99.03
63.03
55.40
37.92
56.85
66.20
67.88
74.67
153.90
96.79
152.90
214.88
132.23
115.46
La
12.11
13.04
13.92
13.55
7.86
12.45
7.07
12.03
11.25
10.71
14.06
20.16
15.52
19.71
21.39
16.26
16.98
Ce
30.77
32.13
32.16
33.44
19.91
29.94
17.28
31.45
26.99
27.55
33.71
45.32
34.39
44.29
47.69
40.03
42.25
Pr
4.44
4.61
4.75
4.83
3.03
4.36
2.62
5.04
4.08
4.48
5.95
7.46
5.71
7.21
6.90
5.84
6.81
Nd
20.94
21.64
21.65
22.00
14.25
19.88
12.05
23.60
18.53
20.80
27.22
32.82
26.01
32.18
30.29
26.92
31.03
Sm
5.55
5.54
5.41
5.91
3.71
5.09
3.48
6.44
5.03
5.73
7.26
8.24
6.86
8.22
7.01
7.10
8.15
Eu
1.80
1.92
1.88
2.01
1.47
1.73
1.29
2.14
1.71
1.92
2.45
2.68
2.29
2.63
2.15
2.22
2.64
497
Gd
6.02
5.91
5.93
6.38
4.26
5.79
4.11
7.05
5.57
5.95
7.52
8.43
7.24
8.19
7.27
7.25
8.23
Tb
1.00
0.99
0.98
1.03
0.76
0.99
0.74
1.20
0.99
1.05
1.22
1.36
1.22
1.32
1.18
1.24
1.31
Dy
5.79
5.59
5.61
6.05
4.37
5.97
4.38
6.97
6.08
6.16
6.83
7.51
7.02
7.49
6.84
7.15
7.28
Ho
1.19
1.11
1.11
1.21
0.89
1.25
0.94
1.45
1.36
1.31
1.36
1.53
1.46
1.50
1.43
1.41
1.44
Er
3.15
2.85
2.80
3.03
2.29
3.35
2.51
3.77
3.52
3.28
3.34
3.82
3.68
3.77
3.70
3.73
3.57
Tm
0.47
0.40
0.41
0.44
0.35
0.49
0.39
0.58
0.53
0.50
0.47
0.54
0.53
0.54
0.54
0.55
0.50
Yb
2.76
2.43
2.40
2.55
2.02
3.05
2.43
3.43
3.44
3.10
2.86
3.37
3.29
3.33
3.27
3.23
2.96
Lu
0.40
0.35
0.35
0.37
0.30
0.43
0.35
0.49
0.50
0.41
0.42
0.50
0.49
0.48
0.46
0.48
0.42
Hf
3.97
3.77
3.73
3.82
2.37
3.38
2.37
4.91
3.87
4.27
4.95
5.54
4.28
5.32
5.56
4.56
6.68
Ta
0.94
0.95
0.92
0.94
0.60
0.97
0.51
0.91
0.96
0.83
0.83
1.39
1.09
1.35
1.42
1.14
0.90
Th
0.93
1.15
1.15
1.18
0.60
1.03
0.56
1.25
1.10
0.98
0.91
1.89
1.37
1.84
1.86
1.48
1.06
U
0.25
0.28
0.27
0.28
0.13
0.30
0.18
0.36
0.30
0.31
0.30
0.58
0.42
0.58
0.58
0.44
0.35
11.06
10.92
10.87
10.61
10.32
9.68
9.85
11.45
9.26
12.32
18.24
12.15
13.14
12.86
10.70
10.39
18.12
Zr/Nb
Norm
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
Locality
ICJ
ICJ
ICJ
ICJ
ICJ
ICJ
Fé
Fé
Fé
Fé
TAS
TAS
TAS
TAS
TAS
TAS
TAS
2085
JOURNAL OF PETROLOGY
VOLUME 44
NUMBER 11
NOVEMBER 2003
Table 1a: continued
417387
426502
426509
426510
436628
436629
436632
436666
436667
436670
436672
436689
436707
436708
436711
417376
426549
SiO2
47.23
48.78
47.82
47.17
47.36
47.74
47.54
47.53
48.26
47.30
47.56
47.71
47.48
48.22
47.28
47.85
48.24
TiO2
3.69
2.69
2.68
2.54
3.47
2.43
2.84
3.68
2.73
3.69
3.52
3.74
2.12
3.51
2.02
2.73
3.01
Al2O3
12.20
13.77
13.94
13.95
12.23
13.60
12.81
12.42
13.20
12.39
12.54
12.58
13.62
12.35
14.46
13.37
12.99
Fe2O3
3.12
2.96
2.36
2.23
3.57
1.80
3.11
4.26
2.61
4.17
3.73
3.11
2.84
3.93
2.77
2.78
2.34
12.99
11.05
9.80
10.76
12.05
10.47
11.49
11.23
10.79
11.34
11.37
12.34
9.99
11.14
9.27
10.85
11.83
wt %
FeO
MnO
0.22
0.20
0.19
0.20
0.24
0.19
0.23
0.24
0.22
0.24
0.23
0.24
0.19
0.24
0.20
0.22
0.22
MgO
5.26
5.63
6.67
6.29
5.56
7.09
5.84
5.45
6.11
5.37
5.64
5.21
6.54
5.48
7.50
6.46
5.86
CaO
9.99
10.28
11.12
11.26
10.56
11.65
11.01
10.30
11.02
10.36
10.65
9.85
11.97
10.38
12.35
10.97
10.77
Na 2O
3.84
2.20
2.91
2.81
2.55
2.10
2.68
2.47
2.67
2.52
2.52
2.61
2.46
2.66
2.03
2.56
2.53
K 2O
0.86
0.39
0.44
0.55
0.31
0.64
0.29
0.60
0.26
0.27
0.42
0.70
0.50
0.31
0.10
0.79
0.53
P2O5
0.38
0.27
0.28
0.29
0.36
0.24
0.32
0.42
0.32
0.44
0.41
0.45
0.24
0.40
0.20
0.29
0.33
Vol.
1.57
1.35
1.47
1.59
1.48
1.45
1.61
1.30
1.57
1.63
1.37
1.30
2.15
1.48
1.72
1.19
1.17
101.33
99.58
99.67
99.63
99.75
99.40
99.76
99.90
99.75
99.72
99.95
99.85
100.11
100.09
99.90
100.07
99.82
Total
ppm
Sc
32
30
33
34
39
38
36
37
35
33
37
38
43
34
36
37
38
V
523
328
384
385
402
372
379
426
387
417
411
472
372
360
327
362
406
Cr
64
57
169
85
52
215
84
65
154
57
73
66
90
71
274
114
83
Co
67
56
58
65
54
53
55
55
48
55
54
56
56
54
54
53
53
Ni
61
59
89
72
52
98
63
57
69
55
58
56
69
56
120
80
62
Cu
218
221
136
166
273
189
210
293
186
314
206
305
177
260
158
204
251
Zn
141
121
93
102
111
114
137
129
119
139
120
153
118
155
100
121
121
Rb
15.01
8.93
6.62
7.19
5.07
14.73
5.33
16.62
5.53
5.92
11.54
17.37
9.49
5.65
2.02
14.56
12.77
Sr
301.67
283.71
293.97
314.57
254.30
228.07
280.24
252.92
252.87
266.42
259.06
264.37
272.22
272.35
219.90
306.27
243.58
Y
39.04
34.49
29.03
28.08
47.11
31.96
40.47
49.99
39.67
51.24
48.77
52.53
38.31
45.09
28.36
35.33
44.16
Zr
258.11
150.55
149.22
147.23
231.30
156.54
207.77
286.04
206.79
292.22
272.76
313.11
192.33
246.32
120.69
170.05
219.18
Nb
13.19
10.58
13.99
13.86
19.09
13.46
19.31
28.29
20.30
27.68
26.98
31.21
20.91
25.17
10.71
16.30
18.67
Ba
121.47
82.92
99.48
145.74
101.38
82.88
102.79
147.66
94.62
130.48
123.50
156.96
109.63
103.86
44.09
183.67
105.24
La
16.12
11.70
16.91
16.34
20.60
12.24
18.52
26.60
19.79
26.85
25.12
27.94
18.48
22.67
9.65
14.47
18.08
Ce
40.55
30.16
35.91
36.02
51.78
31.41
46.67
66.69
48.82
67.84
62.08
65.76
43.25
53.65
23.83
35.31
43.32
Pr
6.41
4.49
5.70
5.76
7.54
4.61
6.60
9.16
6.82
9.13
8.55
9.19
6.08
7.61
3.64
5.21
6.34
Nd
29.32
21.44
24.59
24.68
35.07
21.66
29.65
41.03
29.95
41.38
38.75
40.75
27.99
34.83
16.93
24.26
29.06
Sm
7.69
6.11
6.05
6.03
8.99
5.66
7.54
9.88
7.52
9.94
9.47
9.95
7.03
8.89
4.46
6.29
7.60
Eu
2.45
2.01
2.07
2.00
2.83
1.81
2.36
2.91
2.30
2.96
2.82
2.94
2.23
2.74
1.55
2.06
2.39
Gd
7.89
6.64
6.42
6.05
9.87
5.97
7.61
10.21
7.79
10.12
9.62
9.98
7.44
9.13
5.04
6.56
7.96
Tb
1.26
1.12
1.07
0.98
1.65
1.01
1.28
1.72
1.31
1.71
1.61
1.65
1.24
1.51
0.88
1.08
1.33
Dy
7.09
6.30
6.03
5.61
9.92
5.95
7.43
9.76
7.78
9.90
9.35
9.69
7.05
8.48
5.25
6.23
7.86
Ho
1.31
1.26
1.26
1.16
2.08
1.26
1.60
2.13
1.63
2.13
1.95
2.02
1.46
1.73
1.07
1.28
1.64
Er
3.50
3.32
3.21
2.94
5.38
3.21
4.13
5.46
4.28
5.46
5.12
5.25
3.86
4.56
2.87
3.32
4.24
Tm
0.50
0.47
0.46
0.42
0.81
0.46
0.62
0.81
0.64
0.79
0.74
0.79
0.61
0.70
0.43
0.49
0.67
Yb
2.79
2.76
2.90
2.71
5.05
2.91
3.87
5.15
4.09
5.11
4.89
4.88
3.49
3.89
2.60
2.89
3.84
Lu
0.38
0.43
0.43
0.40
0.70
0.42
0.55
0.75
0.60
0.74
0.71
0.68
0.47
0.51
0.37
0.42
0.58
Hf
6.60
3.91
4.05
4.03
5.94
4.20
5.65
7.74
5.60
7.85
7.39
7.95
5.17
6.58
3.34
4.64
5.72
Ta
0.89
0.76
1.25
1.24
1.40
0.92
1.33
2.04
1.54
2.04
1.95
2.13
1.36
1.61
0.73
1.10
1.28
Th
1.07
0.96
1.35
1.26
1.64
1.00
1.52
2.48
1.66
2.55
2.37
2.69
1.66
2.17
0.75
1.31
1.63
U
0.34
0.27
0.46
0.42
0.45
0.33
0.49
0.76
0.52
0.76
0.69
0.80
0.51
0.66
0.25
0.38
0.51
Zr/Nb
19.57
14.23
10.67
10.62
12.12
11.63
10.76
10.11
10.19
10.56
10.11
10.03
9.20
9.79
11.27
10.43
11.74
Norm
ne
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
Locality
TAS
TAS
TAS
TAS
Lé
Lé
Lé
Lé
Lé
Lé
Lé
Lé
Fé
Fé
Fé
TAS
TAS
2086
HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
426550
410627
410629
410660
410661
410665
410666
410667
410668
410670
410678
410679
410681
410693
410694
416410
417113
SiO2
45.51
48.27
48.69
48.64
47.91
48.00
48.73
47.44
46.66
47.46
47.30
47.24
47.59
47.28
48.50
47.55
48.64
TiO2
2.66
3.64
2.28
3.12
3.03
3.09
2.28
3.76
3.29
3.04
3.74
3.24
2.36
3.58
2.87
1.83
1.31
Al2O3
13.81
12.76
13.94
13.52
13.63
13.04
13.85
12.84
13.30
13.36
12.86
12.92
13.51
13.02
13.80
13.99
15.08
Fe2O3
3.91
2.77
2.44
3.07
4.40
4.01
3.47
2.75
4.12
3.38
4.04
4.25
3.44
3.73
2.64
3.03
2.28
10.75
11.43
9.56
9.00
9.43
10.19
8.40
11.27
10.54
9.85
10.22
10.53
10.07
10.33
8.77
9.43
7.90
wt %
FeO
MnO
0.27
0.22
0.20
0.18
0.23
0.22
0.20
0.22
0.24
0.21
0.22
0.22
0.23
0.22
0.19
0.20
0.17
MgO
4.93
5.30
6.70
6.26
5.31
5.23
6.38
5.54
5.04
6.03
5.36
5.26
6.51
5.64
7.42
7.11
7.78
CaO
9.34
9.59
11.48
11.39
10.22
9.48
10.99
9.96
10.21
10.89
10.38
10.75
11.66
10.59
11.09
11.69
12.33
Na2O
2.83
2.86
2.69
2.41
2.66
2.82
2.59
2.85
2.63
2.72
2.39
2.57
2.19
2.27
2.40
2.28
2.42
K 2O
0.70
0.89
0.57
0.34
0.85
1.04
0.65
0.66
0.88
0.33
0.89
0.65
0.33
0.86
0.38
0.43
0.26
P 2O5
0.61
0.57
0.27
0.36
0.39
0.43
0.29
0.48
0.52
0.42
0.48
0.45
0.28
0.46
0.33
0.20
0.15
Vol.
4.10
1.40
1.19
1.35
1.90
1.91
1.88
1.95
2.29
2.14
1.87
2.00
1.45
1.94
1.54
1.92
1.95
Total
99.42
99.71
100.01
99.65
99.98
99.48
99.70
99.71
99.73
99.82
99.74
100.08
99.60
99.91
99.93
99.66
100.26
ppm
Sc
39
31
36
31
31
32
32
34
30
32
29
31
38
33
28
40
36
V
374
396
357
339
395
393
340
405
427
374
410
384
365
425
297
324
287
Cr
96
75
142
226
83
42
133
74
29
108
67
57
121
81
406
113
274
Co
63
52
50
47
49
50
47
50
53
52
50
53
55
53
49
60
49
Ni
140
46
80
96
50
52
81
56
36
69
56
49
80
60
198
89
58
Cu
37
133
165
182
272
208
191
235
105
199
243
252
199
226
154
187
137
Zn
154
129
116
113
103
104
92
111
140
116
116
141
116
121
102
84
73
7.63
16.26
12.53
9.15
21.05
24.66
14.82
17.69
23.67
7.19
22.04
18.36
13.70
19.40
13.51
9.42
3.49
Sr
31654
444.81
300.02
307.10
277.91
333.24
287.90
369.21
394.58
349.99
351.43
286.96
230.12
357.34
337.79
247.74
313.65
Y
52.10
32.71
30.42
34.58
39.05
41.77
35.40
40.53
33.28
32.54
38.10
43.85
34.42
37.10
31.89
32.57
19.90
Zr
286.69
194.83
155.86
184.88
189.30
216.11
164.24
218.78
158.77
181.13
235.92
251.87
154.87
215.30
193.80
96.22
74.32
Nb
10.60
30.10
20.45
23.55
32.24
32.86
24.56
35.36
37.32
24.95
32.76
36.30
18.02
30.58
22.04
11.03
10.12
Ba
1022.80
403.87
134.28
79.05
189.80
285.78
216.75
283.45
316.48
180.20
338.93
168.19
71.26
249.89
97.41
140.17
113.17
La
37.64
28.69
18.11
17.30
22.45
24.74
18.26
25.76
26.27
18.93
24.32
25.62
13.83
28.35
20.04
10.69
9.45
Ce
78.85
64.66
40.72
43.37
51.46
58.48
43.77
61.26
61.47
45.12
57.02
60.98
34.08
61.59
46.18
26.37
21.81
Pr
11.30
8.47
5.37
6.68
7.48
8.61
6.36
8.97
8.79
7.00
8.80
9.39
5.44
8.41
6.53
3.85
3.03
Nd
47.77
35.69
23.14
29.51
31.53
36.48
26.90
38.85
36.82
30.23
37.55
39.67
24.07
35.38
28.46
17.71
12.91
Sm
9.75
7.71
5.57
7.18
7.19
8.37
6.34
8.79
7.36
7.07
8.51
9.12
5.97
7.89
6.89
4.97
3.19
Eu
2.69
2.70
1.73
2.31
2.17
2.65
2.03
2.78
2.46
2.33
2.56
2.60
1.89
2.54
2.15
1.64
1.23
Rb
Gd
9.19
7.41
5.63
7.08
7.16
8.40
6.61
8.53
7.23
6.71
7.96
8.56
6.26
7.62
7.09
5.16
3.60
Tb
1.48
1.12
0.92
1.14
1.16
1.31
1.08
1.31
1.09
1.09
1.27
1.42
1.08
1.27
1.15
0.92
0.63
Dy
8.55
6.27
5.39
6.33
6.71
7.53
6.38
7.52
6.21
6.13
7.20
8.13
6.32
6.86
6.13
5.69
3.65
Ho
1.82
1.23
1.11
1.25
1.42
1.53
1.35
1.51
1.28
1.25
1.47
1.69
1.35
1.40
1.20
1.19
0.76
Er
4.74
3.10
2.91
3.11
3.69
3.98
3.46
3.91
3.32
3.04
3.70
4.38
3.48
3.73
3.04
3.34
2.08
Tm
0.73
0.45
0.46
0.46
0.56
0.58
0.51
0.58
0.50
0.46
0.55
0.66
0.53
0.54
0.47
0.49
0.32
Yb
4.12
2.68
2.61
2.56
3.35
3.55
3.13
3.49
3.03
2.83
3.31
4.11
3.27
3.15
2.62
3.07
1.96
Lu
0.69
0.39
0.38
0.37
0.49
0.53
0.46
0.49
0.46
0.40
0.46
0.57
0.45
0.44
0.34
0.44
0.30
Hf
6.36
4.59
3.74
5.62
5.66
6.09
4.49
6.24
4.58
4.77
6.29
6.46
4.23
5.42
5.33
2.63
1.90
Ta
0.58
1.99
1.34
1.52
2.04
2.00
1.51
2.20
2.36
1.65
2.15
2.34
1.16
1.92
1.51
0.80
0.60
Th
0.72
1.95
1.54
1.96
2.68
2.42
1.97
2.51
2.28
1.74
2.37
2.72
1.28
2.22
1.72
0.97
0.72
U
0.19
0.44
0.35
0.56
0.68
0.63
0.51
0.62
0.61
0.45
0.60
0.78
0.37
0.59
0.52
0.23
0.21
27.05
6.47
7.62
7.85
5.87
6.58
6.69
6.19
4.25
7.26
7.20
6.94
8.59
7.04
8.79
8.73
Zr/Nb
7.35
Norm
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
Locality
TAS
ICJ
ICJ
Fé
Fé
Fé
Fé
Fé
Fé
Fé
Fé
Fé
Fé
Fé
Fé
TAS
TAS
2087
JOURNAL OF PETROLOGY
VOLUME 44
NUMBER 11
NOVEMBER 2003
Table 1a: continued
417377
426501
426506
436614
436626
436627
436631
436633
436634
43668
436710
SiO2
45.48
45.76
46.56
46.43
47.78
47.50
48.24
47.65
47.18
47.45
48.07
TiO2
1.84
3.07
3.34
4.12
3.14
2.33
2.62
3.61
3.68
3.26
2.89
A12O3
14.36
13.35
13.52
12.78
12.67
13.90
14.49
12.61
12.92
12.99
13.24
Fe2O3
2.05
3.99
3.17
3.45
3.19
2.25
2.50
3.68
3.73
3.63
3.49
FeO
10.45
9.54
11.22
11.88
11.45
9.81
10.05
11.16
10.34
10.72
9.87
MnO
0.21
0.18
0.22
0.24
0.22
0.20
0.20
0.23
0.22
0.23
0.21
MgO
7.64
5.91
5.89
4.98
5.21
7.02
5.39
5.25
5.45
5.42
5.72
CaO
10.15
10.12
10.61
9.73
10.82
12.22
10.67
9.86
10.02
10.48
10.38
Na2O
3.29
2.96
2.55
3.15
2.48
2.22
2.70
2.63
2.38
2.53
2.83
K2O
0.92
0.83
0.92
1.03
0.51
0.19
0.65
0.74
1.17
0.72
0.62
P2O5
0.46
0.36
0.41
0.55
0.43
0.27
0.34
0.51
0.48
0.45
0.39
Vol.
2.71
3.32
1.26
1.54
1.75
1.86
1.85
1.80
2.06
1.80
2.08
Total
99.57
99.38
99.66
99.87
99.68
99.77
99.70
99.74
99.63
99.67
99.79
wt %
ppm
Sc
31
26
32
30
34
36
29
28
37
30
32
V
293
366
404
451
396
336
343
143
481
427
372
Cr
98
42
111
33
34
199
51
7
21
29
69
Co
66
60
65
55
56
49
49
33
53
53
51
Ni
84
75
77
50
43
104
54
3
27
36
58
Cu
10
156
180
270
200
194
157
52
48
105
205
Zn
154
125
107
147
140
113
97
156
136
140
116
Rb
10.50
16.26
19.90
17.60
10.94
3.82
12.07
16.73
20.45
21.80
12.19
Sr
561.77
564.39
375.38
376.53
292.10
243.67
385.09
302.84
332.38
292.25
397.43
Y
23.63
26.15
36.55
41.55
36.02
32.06
32.21
51.41
38.49
44.13
34.37
Zr
134.46
208.13
214.76
313.28
230.52
156.02
203.42
299.80
239.49
260.33
201.12
Nb
23.80
23.23
24.21
43.38
26.96
18.27
25.20
38.85
32.21
35.13
26.50
Ba
546.60
276.44
306.52
268.04
156.84
81.24
153.83
219.18
364.87
220.16
304.44
La
24.63
23.56
22.88
40.17
26.87
17.59
22.97
35.44
30.50
32.42
23.81
Ce
48.25
53.06
50.93
91.20
63.37
40.89
54.61
81.43
70.47
75.98
53.97
Pr
7.15
7.86
7.53
11.87
8.69
5.74
7.32
10.56
9.10
9.94
7.11
Nd
38.23
32.71
31.41
50.42
37.84
25.19
31.29
44.75
39.32
41.84
30.71
Sm
5.81
7.00
7.40
10.67
8.46
6.17
6.97
9.89
8.53
9.10
7.05
Eu
1.97
2.16
2.33
3.14
2.62
1.97
2.22
2.83
2.71
2.70
2.35
Gd
5.58
6.14
7.37
10.11
8.54
6.60
6.85
9.86
8.35
9.05
6.78
Tb
0.87
0.93
1.18
1.58
1.35
1.12
1.09
1.66
1.32
1.50
1.08
Dy
4.79
4.74
6.54
8.91
7.73
6.60
6.27
9.47
7.61
8.56
6.21
Ho
0.99
0.95
1.27
1.78
1.57
1.38
1.26
2.01
1.56
1.79
1.27
Er
2.52
2.22
3.12
4.58
3.98
3.57
3.25
5.25
4.02
4.77
3.36
Tm
0.37
0.32
0.49
0.66
0.61
0.55
0.48
0.80
0.58
0.70
0.50
Yb
2.34
1.70
2.81
3.99
3.59
3.37
3.03
4.86
3.65
4.39
3.04
Lu
0.35
0.23
0.40
0.58
0.52
0.50
0.43
0.74
0.52
0.66
0.42
Hf
3.46
4.76
5.48
7.62
5.65
4.26
5.36
8.02
6.14
6.75
5.10
Ta
1.79
1.59
1.60
3.02
1.90
1.31
1.70
2.61
2.16
2.43
1.72
Th
2.26
1.63
1.95
3.83
2.33
1.50
1.94
3.32
2.50
3.22
1.92
U
0.68
0.50
0.56
1.01
0.61
0.38
0.56
0.94
0.66
0.90
0.50
Zr/Nb
5.65
8.96
8.87
7.22
8.55
8.54
8.07
7.72
7.44
7.41
7.59
Norm
ne
ne
hy
hy
hy
hy
hy
hy
hy
hy
hy
Locality
TAS
TAS
TAS
Lé
Lé
Lé
Lé
Lé
Lé
Lé
Fé
Sc, V, Cr, Co, Ni, Cu, Zn were analysed by XRF, other trace elements by ICP-MS. ICJ, I. C. Jacobsen Fjord; Fé, Fladù; TAS,
Tasiilaq; Lé, Langù.
2088
HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Table 1b: Major and trace element analyses of PAS dykes
410684
416401
416405
417111
417382
426547
426548
426553
436691
438121
wt %
SiO2
TiO2
Al2O3
Fe2O3
FeO
MnO
MgO
CaO
Na2O
K2O
51.08
1.48
47.60
2.32
47.56
1.46
47.02
2.26
44.29
1.63
44.12
1.28
45.98
1.42
49.40
1.96
43.72
1.34
5.85
12.12
2.77
10.72
2.45
13.20
2.05
10.08
2.77
12.05
1.89
12.50
1.97
9.56
0.18
8.01
0.15
9.15
0.17
6.38
2.88
9.15
8.17
0.16
8.06
0.16
9.30
0.20
7.06
2.78
9.24
10.52
10.16
12.97
12.19
9.23
11.71
10.81
10.98
9.57
9.96
0.17
22.98
6.89
2.02
0.40
1.25
0.94
2.18
7.46
0.98
17.61
8.26
2.08
0.40
1.79
1.27
0.66
0.79
0.17
1.69
0.24
0.18
0.94
0.79
0.22
2.16
0.35
0.22
0.16
5.26
0.22
1.30
0.13
3.87
99.55
3.24
99.43
0.15
5.00
100.04
1.87
99.42
99.34
99.24
99.43
99.61
11.42
0.97
9.17
0.16
11.38
9.84
4.93
7.73
0.17
20.62
8.73
0.39
1.82
0.50
Vol.
0.15
1.88
Total
99.84
P2O5
43.77
2.49
0.13
0.21
4.37
99.37
0.16
22.84
ppm
Sc
27
29
32
36
38
22
26
29
33
24
V
245
259
350
272
343
200
224
263
330
227
1720
Cr
922
1643
554
1410
466
2510
1460
866
587
Co
60
94
66
63
57
105
79
59
58
97
Ni
365
1044
329
345
191
1080
807
303
204
1200
Cu
99
144
172
117
132
34
82
116
122
84
Zn
83
22.16
98
90
101
105
171
68
75
114
92
Rb
Sr
Y
Zr
Nb
Ba
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Hf
Ta
Th
U
Zr/Nb
6.09
7.46
17.66
5.63
8.76
14.17
5.12
32.62
19.93
204.31
17.02
166.84
19.91
254.74
25.52
208.61
17.65
301.79
23.60
229.04
14.39
216.92
17.11
331.44
18.06
272.28
23.05
161.28
15.90
116.30
8.43
171.01
16.96
134.57
8.29
90.00
8.44
129.13
13.45
113.39
11.88
82.89
8.67
88.85
8.03
130.86
6.86
75.39
4.18
113.46
11.19
40.50
18.96
57.88
10.13
132.98
10.31
87.51
13.71
88.54
11.42
208.59
9.18
163.77
9.55
121.54
10.75
53.96
4.65
26.95
4.07
40.99
6.59
24.60
4.20
24.82
3.64
29.12
4.64
27.70
4.00
21.52
3.13
23.05
3.41
26.94
4.09
12.86
2.06
17.57
4.11
27.71
6.17
19.46
5.30
15.85
3.84
20.17
4.77
17.46
4.17
14.15
3.47
15.58
3.98
19.18
4.97
9.93
2.91
1.32
4.11
1.86
5.58
1.79
5.51
1.28
3.96
1.67
4.99
1.26
3.85
1.12
3.52
1.28
3.91
1.64
5.24
1.02
3.34
0.67
3.65
0.84
4.26
0.91
5.11
0.64
3.49
0.81
4.48
0.58
2.92
0.57
3.29
0.63
3.47
0.88
4.80
0.57
3.16
0.75
1.86
0.82
1.96
1.04
2.49
0.67
1.75
0.93
2.28
0.53
1.33
0.66
1.72
0.70
1.72
0.94
2.32
0.61
1.51
0.27
1.61
0.26
1.51
0.36
2.14
0.25
1.48
0.32
2.06
0.20
1.02
0.25
1.51
0.26
1.52
0.35
1.97
0.22
1.28
0.22
3.26
0.22
4.53
0.30
3.68
0.22
2.38
0.30
3.29
0.14
3.01
0.22
2.32
0.21
2.41
0.26
3.49
0.19
2.09
0.56
1.10
1.41
1.50
0.62
0.65
0.70
0.65
1.05
0.96
0.77
0.74
0.58
0.59
0.56
0.54
0.46
0.55
0.26
0.36
0.25
13.80
0.49
0.23
16.24
0.20
10.67
0.35
9.60
0.24
9.54
0.18
9.56
0.18
11.06
0.18
10.08
19.08
0.12
18.04
Norm
hy
hy
hy
hy
hy
hy
hy
hy
hy
hy
Locality
Fé
TAS
TAS
TAS
TAS
TAS
TAS
TAS
Lé
Lé
Sc, V, Cr, Co, Ni, Cu, Zn were analysed by XRF, other trace elements by ICP-MS.
2089
JOURNAL OF PETROLOGY
VOLUME 44
NUMBER 11
NOVEMBER 2003
Table 1c: Major and trace element analyses of Transitional Series dykes
410628
410633
410634
410635
410636
410659
410664
410682
410697
417110
417365
417367
417369
417371
417373
417379
417388
SiO2
50.13
51.13
47.93
48.02
47.56
48.64
50.14
50.06
46.84
49.91
46.35
46.52
52.95
49.86
47.60
51.81
46.45
TiO2
3.30
2.84
3.38
3.37
3.44
3.40
3.14
2.78
3.47
2.91
2.25
2.19
2.38
2.49
2.62
2.38
2.17
Al2O3
12.95
12.99
13.04
13.01
14.11
12.83
13.47
13.58
13.15
15.10
16.49
16.57
14.04
13.95
13.20
13.55
16.57
Fe2O3
3.27
2.57
3.41
3.83
3.31
3.58
4.02
3.02
4.70
3.98
1.50
1.71
3.17
3.01
3.65
2.95
1.05
FeO
11.09
11.22
11.64
11.13
10.16
10.48
8.65
10.28
9.91
7.30
8.21
7.96
8.55
10.13
11.52
9.33
8.70
MnO
0.22
0.28
0.23
0.23
0.20
0.23
0.23
0.27
0.23
0.16
0.18
0.17
0.15
0.17
0.25
0.18
0.16
wt %
MgO
4.50
3.32
4.83
4.82
5.12
4.62
4.00
3.30
4.82
4.97
3.67
3.56
3.61
4.35
4.90
4.76
3.63
CaO
8.84
7.86
9.11
9.17
9.62
8.89
8.07
7.86
8.72
9.43
7.11
7.60
6.87
7.10
9.35
8.13
7.45
Na2O
2.96
3.21
3.18
2.98
3.47
3.13
3.67
3.42
3.66
3.77
6.04
5.72
4.00
4.81
3.37
3.94
5.69
K 2O
0.83
0.98
0.87
0.87
0.65
1.08
1.18
1.50
1.14
0.72
0.98
1.22
1.38
1.16
0.82
0.77
1.24
P 2O5
0.39
1.12
0.41
0.40
0.50
0.49
0.63
1.24
0.54
0.40
0.71
0.72
0.44
0.39
0.40
0.33
0.71
Vol.
1.37
2.07
2.00
2.16
1.88
2.21
2.20
2.46
2.55
1.38
6.16
5.64
2.21
2.51
2.17
1.44
5.57
Total
99.86
99.58
99.99
99.98
100.03
99.57
99.41
99.78
99.73
100.02
99.65
99.56
99.75
99.93
99.83
99.57
99.40
ppm
Sc
37
28
37
38
27
29
26
16
28
26
11
9
21
28
39
34
10
V
425
143
481
493
353
421
285
110
384
334
192
177
294
414
415
366
179
Cr
35
7
21
20
41
29
12
5
20
85
3
3
5
7
9
3
2
Co
49
33
53
55
52
50
42
34
55
43
32
31
54
56
64
44
39
Ni
24
3
27
27
35
37
12
52
31
52
2
3
14
35
27
17
4
Cu
66
52
48
55
77
134
24
3
58
72
15
20
37
32
135
69
30
Zn
143
156
136
149
137
143
126
157
116
114
112
121
117
113
107
98
84
29.45
20.59
20.19
24.76
12.48
996.51 1109.44
376.55
400.60
390.98
29.71
35.01
32.34
36.41
31.22
28.78
281.97
279.46
240.14
203.66
193.75
271.52
40.48
46.24
24.58
19.49
29.07
15.70
41.93
113.17
737.48
595.05
548.05
509.99
281.19
260.00
770.53
30.99
9.45
41.10
41.74
43.35
37.73
26.33
23.52
42.96
66.99
21.81
80.05
88.42
93.71
82.13
55.47
53.61
86.28
14.59
8.91
3.03
10.86
11.18
11.31
10.25
7.30
7.03
11.75
49.97
62.09
37.21
12.91
41.80
45.04
46.03
41.07
30.36
30.92
44.31
10.74
12.93
7.78
3.19
7.85
8.79
9.01
8.27
6.63
6.91
8.45
2.67
3.17
3.85
2.64
1.23
2.38
2.79
2.60
2.41
2.04
2.24
2.52
8.76
8.59
10.57
12.03
7.26
3.60
6.93
7.20
8.05
7.49
6.42
6.90
7.30
1.26
1.34
1.66
1.86
1.17
0.63
0.99
1.05
1.24
1.14
1.05
1.08
1.04
Rb
18.55
22.87
16.19
17.05
13.15
31.34
32.50
33.12
31.48
3.49
14.93
Sr
305.98
338.08
325.78
295.03
482.47
330.57
292.81
403.08
428.44
313.65
Y
37.19
55.67
35.86
34.77
30.85
44.84
55.63
54.97
34.03
19.90
27.63
Zr
195.75
241.98
176.48
169.81
229.84
291.32
255.47
236.92
186.04
74.32
261.96
Nb
22.92
39.58
27.64
26.74
26.82
37.37
46.07
46.45
35.15
10.12
Ba
324.14
415.29
241.91
232.69
182.16
285.90
339.24
719.46
316.23
La
23.86
44.80
25.74
25.87
33.81
27.38
34.79
40.27
Ce
52.70
102.00
57.26
56.54
76.29
75.71
97.39
113.01
Pr
6.80
13.34
7.42
7.40
9.93
9.37
12.01
Nd
29.12
56.84
31.07
30.99
42.05
39.50
Sm
6.64
12.50
6.90
6.90
9.19
8.86
Eu
2.18
4.16
2.23
2.30
3.06
Gd
6.57
12.38
7.04
7.08
Tb
1.08
1.90
1.16
1.20
23.66
427.40 1019.18
Dy
6.47
10.85
6.82
6.79
6.96
7.78
9.73
10.67
6.52
3.65
5.02
5.28
6.82
6.36
5.84
6.10
5.29
Ho
1.37
2.27
1.44
1.43
1.26
1.60
2.01
2.19
1.28
0.76
0.92
1.00
1.34
1.21
1.22
1.20
0.98
Er
3.52
5.72
3.80
3.84
3.18
4.13
5.26
5.57
3.42
2.08
2.34
2.44
3.47
3.23
3.30
3.18
2.48
Tm
0.53
0.84
0.59
0.60
0.44
0.63
0.82
0.84
0.52
0.32
0.35
0.35
0.52
0.48
0.52
0.46
0.37
Yb
3.24
5.02
3.55
3.65
2.50
3.75
4.79
5.05
3.02
1.96
1.89
2.00
3.08
2.84
3.03
3.05
2.02
Lu
0.49
0.74
0.52
0.54
0.36
0.55
0.74
0.69
0.41
0.30
0.28
0.32
0.46
0.46
0.47
0.45
0.29
Hf
4.78
5.81
4.36
4.45
5.50
7.00
7.70
6.00
4.79
1.90
5.39
6.12
7.08
5.79
5.08
4.82
5.72
Ta
1.54
2.65
1.86
1.87
2.53
2.35
2.95
3.17
2.26
0.60
2.24
2.58
1.54
1.32
1.78
1.05
2.47
Th
2.84
3.30
2.20
2.15
3.39
2.98
3.84
3.80
2.30
0.72
3.29
3.66
3.68
3.13
2.16
1.42
3.70
U
0.47
0.74
0.47
0.50
0.88
0.76
0.94
0.94
0.61
0.21
0.91
1.02
0.73
0.65
0.60
0.39
1.01
Zr/Nb
8.54
6.11
6.39
6.35
6.24
7.80
5.54
5.10
5.29
7.35
6.47
6.10
11.37
12.32
7.01
12.34
6.48
Norm
hy
hy
hy
hy
hy
hy
hy
hy
ne
hy
ne
ne
hy
ne
hy
hy
ne
Locality
ICJ
ICJ
ICJ
ICJ
ICJ
Fé
Fé
Fé
Fé
TAS
TAS
TAS
TAS
TAS
TAS
TAS
TAS
2090
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
HANGHéJ et al.
417389
417390
417392
426503
426507
426527
426528
426542
436671
436686
436687
436688
436703
436704
436705
436706
436709
SiO2
47.73
49.72
50.79
49.63
49.38
53.14
53.37
50.09
48.39
48.34
48.44
49.05
49.68
49.17
48.98
45.23
47.66
TiO2
1.71
2.19
2.61
1.78
2.50
2.58
2.64
2.11
3.30
2.86
2.04
2.41
2.74
2.78
2.95
3.69
2.91
Al2O3
17.31
15.22
13.85
15.06
13.59
13.15
13.24
14.48
13.27
12.95
16.14
12.80
13.52
13.47
13.75
13.34
13.39
wt %
Fe2O3
2.89
1.91
2.72
2.92
2.99
3.65
3.65
2.66
4.14
4.18
3.32
4.42
2.97
1.73
3.67
2.60
5.21
FeO
7.22
10.11
9.84
8.97
10.63
9.18
9.12
9.41
9.83
10.58
8.59
11.30
10.01
11.05
10.28
11.50
8.96
MnO
0.16
0.18
0.19
0.15
0.20
0.18
0.18
0.18
0.23
0.23
0.17
0.25
0.21
0.20
0.22
0.21
0.22
MgO
3.29
4.04
4.28
4.94
4.65
3.97
3.96
5.21
4.50
5.02
5.80
4.99
4.52
4.69
5.24
5.18
4.98
CaO
8.38
7.40
8.26
7.86
8.63
7.63
7.36
8.25
7.79
9.50
8.70
9.52
9.14
8.36
9.98
9.63
8.63
Na 2O
4.96
4.50
3.55
3.72
3.59
3.27
3.36
3.68
3.72
2.87
3.25
2.73
2.59
3.69
2.80
3.01
3.77
K 2O
1.60
1.58
0.88
0.65
0.65
1.14
1.24
0.50
1.93
0.80
0.73
0.72
0.88
1.20
0.65
1.46
0.86
P2O5
0.55
0.44
0.38
0.41
0.41
0.45
0.46
0.41
0.60
0.40
0.38
0.31
0.40
0.38
0.39
0.86
0.38
Vol.
3.40
2.01
2.04
3.41
2.11
1.46
1.29
2.75
2.27
1.82
2.39
1.58
2.69
2.79
1.29
2.75
2.62
Total
99.20
99.29
99.39
99.48
99.34
99.80
99.85
99.73
99.96
99.55
99.93
100.08
99.35
99.49
100.20
99.47
99.60
ppm
Sc
12
23
27
28
30
29
30
36
26
34
27
38
26
29
34
31
31
V
222
283
370
268
358
375
374
300
342
419
262
450
410
410
382
364
406
Cr
3
4
17
35
12
14
14
37
9
25
28
35
16
26
31
14
11
Co
36
48
53
44
61
45
48
53
48
49
48
48
47
46
50
51
56
Ni
13
11
21
44
24
16
15
76
15
35
65
29
20
34
46
19
32
Cu
54
52
68
17
101
30
34
77
32
69
34
151
53
82
184
76
223
Zn
101
104
91
107
124
130
171
146
150
124
118
114
131
135
107
112
130
Rb
33.93
33.51
15.39
10.39
12.08
16.42
18.55
5.45
39.80
13.92
13.66
14.77
13.40
25.35
16.15
30.75
21.69
Sr
694.14
467.68
360.38
582.59
353.29
388.62
429.58
491.64
378.25
290.94
451.25
224.36
356.95
355.82
331.35
493.86
260.84
Y
28.32
32.62
36.00
27.74
32.01
28.76
32.29
32.35
37.64
39.84
29.58
39.97
31.22
39.08
36.95
31.39
38.29
Zr
177.48
208.68
215.82
167.33
172.75
206.31
239.35
218.57
229.37
218.31
182.62
168.91
188.83
212.66
213.35
177.24
220.51
Nb
36.74
31.06
30.01
12.82
20.41
14.75
15.85
15.71
37.34
23.56
19.46
18.92
25.16
32.61
27.85
39.33
31.80
Ba
447.31
332.53
406.57
586.53
245.03
567.73
820.55
332.09
634.90
380.62
333.89
242.24
309.24
330.52
204.00
718.03
271.18
La
38.34
30.22
28.56
26.94
25.73
28.13
30.32
28.95
37.10
26.71
25.42
20.40
31.86
30.49
27.34
34.08
25.59
Ce
80.15
62.43
63.98
57.55
56.69
62.03
60.00
57.55
82.98
63.00
59.72
47.72
65.68
65.61
59.36
77.75
57.06
Pr
9.40
8.05
8.04
8.21
7.30
8.01
8.13
8.08
10.44
8.29
8.00
6.48
8.40
8.59
7.96
10.48
7.47
Nd
35.73
32.46
33.39
32.60
31.12
33.17
32.82
33.19
43.46
35.32
34.32
27.99
34.04
35.71
33.71
43.99
31.99
Sm
6.40
6.59
7.04
6.53
6.92
7.09
7.05
7.00
8.89
7.91
7.01
6.61
7.03
7.59
7.63
8.89
7.05
Eu
2.00
1.98
2.20
2.03
2.24
2.22
2.23
2.10
2.82
2.54
2.26
2.12
2.27
2.34
2.36
3.20
2.27
Gs
5.99
6.15
7.20
5.90
6.87
6.52
6.64
6.31
8.43
8.20
6.70
7.07
6.84
7.66
7.57
8.22
7.09
Tb
0.93
0.98
1.15
0.88
1.09
1.00
1.02
0.98
1.33
1.35
1.08
1.24
1.08
1.26
1.27
1.15
1.13
Dy
5.20
5.33
6.60
4.95
6.28
5.46
5.23
5.40
7.61
7.89
5.95
7.63
6.03
7.29
7.09
6.16
6.52
Ho
1.07
1.09
1.38
0.94
1.28
1.09
1.08
1.04
1.60
1.69
1.22
1.66
1.16
1.54
1.47
1.21
1.35
Er
2.79
2.98
3.57
2.49
3.15
2.76
2.72
2.74
4.15
4.31
3.17
4.58
3.08
4.02
3.80
3.04
3.61
Tm
0.44
0.47
0.55
0.38
0.50
0.41
0.43
0.41
0.60
0.64
0.46
0.72
0.49
0.63
0.59
0.45
0.54
Yb
2.72
2.67
3.51
2.11
3.05
2.36
2.30
2.44
3.73
4.12
2.82
4.65
2.80
3.73
3.46
2.54
3.27
Lu
0.42
0.41
0.52
0.30
0.47
0.33
0.33
0.34
0.55
0.64
0.41
0.68
0.38
0.50
0.46
0.33
0.48
Hf
3.78
5.31
5.25
3.97
4.40
5.21
5.35
4.99
6.17
5.71
4.72
4.63
4.88
5.54
5.61
4.45
5.57
Ta
2.19
1.88
1.92
0.73
1.37
0.93
0.91
1.00
2.65
1.63
1.50
1.29
1.60
2.07
1.84
2.53
2.00
Th
3.79
2.42
2.60
1.02
2.47
1.65
1.62
1.20
3.23
2.35
1.61
1.73
2.40
2.80
2.36
2.40
2.38
U
0.98
0.65
0.78
0.31
0.51
0.36
0.36
0.36
0.83
0.68
0.48
0.51
0.52
0.70
0.61
0.69
0.66
Zr/Nb
4.83
6.72
7.19
13.05
8.46
13.99
15.10
13.92
6.14
9.27
9.38
8.93
7.50
6.52
7.66
4.51
6.93
Norm
ne
ne
hy
hy
hy
hy
hy
hy
ne
hy
hy
hy
hy
hy
hy
ne
hy
Locality
TAS
TAS
TAS
TAS
TAS
TAS
TAS
TAS
Lé
Lé
Lé
Lé
Fé
Fé
Fé
Fé
Fé
Sc, V, Cr, Co, Ni, Cu, Zn were analysed by XRF, other trace elements by ICP-MS.
2091
JOURNAL OF PETROLOGY
VOLUME 44
Table 1d: Reproducibility of
monitor standard 95358
95358*
SD %y
ppm
Rb
514
583
Sr
19247
241
Y
3019
365
Zr
12332
530
Nb
867
291
Ba
5364
409
La
809
469
Ce
2054
272
Pr
322
352
Nd
1545
359
Sm
454
383
Eu
158
404
Gd
508
503
Tb
089
521
Dy
523
538
Ho
109
616
Er
293
541
Tm
043
819
Yb
262
581
Lu
038
773
Hf
328
274
Ta
069
538
Th
067
589
U
021
638
NUMBER 11
NOVEMBER 2003
phase of magmatism. All PAS dykes are hypersthene
normative.
The PAS dykes typically have olivine phenocrysts
and clinopyroxene and/or olivine microphenocrysts in
a groundmass of olivine, clinopyroxene, Fe---Ti oxide
minerals and plagioclase. The least MgO-rich samples
have a doleritic texture with less than 5% phenocrysts.
The more MgO-rich dykes typically have more abundant phenocrysts and commonly also have a quench
texture in the groundmass defined by composite starshaped plagioclase grains. Some PAS dykes contain
partly resorbed olivine xenocrysts and/or dunite
fragments.
Groundmass clinopyroxene and plagioclase is commonly altered, and groundmass olivine is always
replaced. Phenocrysts are typically partly replaced
with fresh centres. The most common secondary phases
are chlorite, sericite and epidote.
The Transitional Series (TRANS)
*Average composition of monitor standard; n ˆ 23.
yRelative standard deviation for monitor standard.
Tholeiitic Picrite---Ankaramite Series (PAS)
These dykes correspond to parts of the Lower Basalts
(e.g. Nielsen, 1978; Hansen, 1997; Gill et al., 1998), are
relatively rare, and probably constitute less than 1% of
the dyke swarm. Most samples of PAS dykes come from
the Tasiilaq area, which reflects higher sampling intensity in that area, rather than an increased abundance
of PAS dykes. Most of the PAS dykes strike roughly
parallel to the coast.
The PAS dykes range in thickness from less than
05 m to more than 10 m, and dip between 50 landwards and vertical. Although volumetrically insignificant, the tholeiitic PAS are important in this study
because they are amongst the oldest of the dykes.
Crosscutting relations show that the PAS dykes are
generally older than, or contemporaneous with, the
oldest of the TS dykes, and thus belong to the earliest
This group contains both hypersthene normative and
nepheline normative dykes, and does not correlate with
any known sequence in the flood basalts (Fig. 3). The
transitional dykes constitute 20---30% of the dyke
swarm, and at all localities they are uncommon in the
most inland areas. They are always amongst the
youngest in groups of crosscutting dykes. They are
usually light grey, coarse-grained dolerites, wider
than 5 m, and subvertical with an overall coast-parallel
strike. The transitional dykes thus post-date the coastal
flexure.
The TRANS dykes typically have a fine-grained
doleritic texture with ubiquitous plagioclase, clinopyroxene and Fe---Ti oxide minerals, and occasional
olivine and apatite. Some samples have primary biotite
and amphibole. Small amounts of plagioclase phenocrysts (55%) are common.
The TRANS dykes are often very altered with
sericitized plagioclase, and completely replaced clinopyroxene. Olivine is never fresh. Some samples are
relatively unaltered with fresh plagioclase, clinopyroxene and biotite.
Crosscutting relations show that the relative chronology of the dykes is, from oldest to youngest, PAS,
high Zr/Nb TS dykes, low Zr/Nb TS dykes and
TRANS dykes. This chronology can only be considered approximate in the sense that the PAS, high Zr/
Nb and low Zr/Nb groups occasionally show crosscutting relationships discordant to this general chronology. This is consistent with the observation of
intercalated PAS and TS lavas in the Lower Basalts
(Nielsen & Brooks, 1981; Gill et al., 1988; Hansen,
1997).
2092
HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Table 2: Sr---Nd---Pb isotope data
Sample
Type
Locality
143
Nd/144 Nd
143
Nd/144 NdInit (2SE)
87
eNd
Sr/86 Sr
87
Sr/86 SrInit (2SE)
Rb (ppm) Sr (ppm) Sm (ppm) Nd (ppm)
417382
PAS
TAS
0.512957
0.512896
0.000015
6.49 0.703411
0.703408
0.000008
0.34
243.16
3.49
13.18
416417
PAS
TAS
0.512901
0.512846
0.000013
5.52 0.703384
0.703374
0.000027
1.89
435.66
5.94
24.85
416401
PAS
TAS
0.512899
0.512844
0.000006
5.48 0.703130
0.703125
0.000007
0.42
292.24
4.86
20.30
417368
TS high Zr/Nb TAS
0.512967
0.512896
0.000006
6.48 0.703460
0.703455
0.000010
0.48
251.65
2.81
9.02
TS high Zr/Nb TAS
0.512923
0.512859
0.000006
5.77 0.703450
0.703446
0.000007
0.55
364.96
3.54
12.75
417387
TS high Zr/Nb TAS
0.513015
0.512946
0.000009
7.46 0.703329
0.703326
0.000011
0.39
319.03
4.05
13.38
417386
TS high Zr/Nb TAS
0.513014
0.512954
0.000007
7.62 0.703283
0.703279
0.000007
0.52
314.24
4.68
17.82
417370
426502
TS high Zr/Nb TAS
0.512981
0.512914
0.000023
6.85 0.703461
0.703450
0.000007
0.25
257.40
2.23
7.70
416410
TS high Zr/Nb TAS
0.513015
0.512943
0.000054
7.41 0.703540
0.703522
0.000008
0.49
345.36
2.97
10.86
417364
TS high Zr/Nb TAS
0.513058
0.152997
0.000014
8.46 0.703343
0.703331
0.000010
1.35
281.78
3.20
12.01
417366
TS high Zr/Nb TAS
0.512969
0.512906
0.000011
6.69 0.703465
0.703462
0.000010
1.21
159.25
2.03
5.77
TS high Zr/Nb Lé
0.512963
0.512901
0.000007
6.58 0.703733
0.703702
0.000007
3.73
284.55
6.33
23.39
436689
TS high Zr/Nb Lé
0.512968
0.512906
0.000006
6.68 0.703664
0.703644
0.000008
2.14
259.12
6.40
23.52
436629
TS high Zr/Nb Lé
0.513009
0.512940
0.000006
7.34 0.703747
0.703701
0.000008
3.68
188.66
3.39
11.22
16.76
436672
436666
TS high Zr/Nb Lé
0.512965
0.512903
0.000007
6.63 0.703658
0.703632
0.000011
2.48
225.07
4.53
436707
TS high Zr/Nb Fé
0.512951
0.512885
0.000005
6.28 0.707103
0.706998
0.000008 11.85
268.83
2.86
9.96
410683
TS high Zr/Nb Fé
0.512999
0.512923
0.000007
7.01 0.704415
0.704383
0.000010
2.69
202.16
3.00
9.05
410662
TS high Zr/Nb Fé
0.513017
0.512933
0.000018
7.22 0.703475
0.703464
0.000008
0.64
134.40
1.08
2.97
TS high Zr/Nb ICJ
0.512994
0.512925
0.000007
7.06 0.703846
0.703799
0.000007
5.65
287.14
3.26
10.90
0.512818
0.000005
4.96 0.703856
0.703836
0.000007
3.54
428.01
5.63
22.95
410630
436614
TS low Zr/Nb
Lé
0.512874
436627
TS low Zr/Nb
Lé
0.512954
0.512882
0.000006
6.22 0.703655
0.703643
0.000007
1.15
227.46
2.97
9.46
436668
TS low Zr/Nb
Lé
0.512894
0.512828
0.000006
5.17 0.704198
0.704115
0.000011 10.35
297.29
3.99
13.90
410660
TS low Zr/Nb
Fé
0.512977
0.512905
0.000007
6.66 0.703479
0.703463
0.000007
2.18
316.17
4.16
13.20
410661
TS low Zr/Nb
Fé
0.512913
0.512852
0.000007
5.63 0.704231
0.704102
0.000007 18.04
333.98
3.61
13.54
410679
TS low Zr/Nb
Fé
0.512918
0.512854
0.000014
5.66 0.704366
0.704256
0.000007 14.17
306.23
4.56
16.24
410682
TRANS
Fé
0.512693
0.512651
0.000006
1.47 0.705595
0.705442
0.000010 39.1
502.93
5.65
25.81
Fé
0.512731
0.512687
0.000008
2.17 0.705920
0.705739
0.000008 38.29
416.38
5.89
25.63
0.512474
0.000009 ---2.00 0.706762
0.706729
0.000011
5.35
320.20
3.19
12.34
22.67
410664
TRANS
410628
TRANS
ICJ
0.512523
417390
TRANS
TAS
0.512402
0.512362
0.000007 ---4.18 0.704151
0.704136
0.000014
1.52
1181.46
5.17
417388
TRANS
TAS
0.512556
0.512518
0.000009 ---1.14 0.703269
0.703266
0.000014
5.16
655.89
6.05
30.37
417373
TRANS
TAS
0.512751
0.512706
0.000007
2.54 0.703471
0.703458
0.000011
1.21
641.83
2.55
12.36
417367
TRANS
TAS
0.512553
0.512514
0.000015 ---1.22 0.703285
0.703281
0.000030
1.68
253.93
2.86
12.14
0.000010 47.54
325.33
6.58
28.70
320.80
6.45
28.36
294.24
5.75
26.01
BCR-1 (1)
0.512627
0.000007 ---0.21 0.704999
BCR-1 (2)
0.512617
0.000006 ---0.41
BCR-1 (3)
0.512623
0.000006 ---0.29 0.705006
Sample
Type
Locality
206
Pb/204 Pb
207
Pb/204 Pb
208
Pb/204 Pb
206
Pb/204 PbInit
0.000007
207
Pb/204 PbInit
207
Pb/204 PbInit
Pb (ppm)
U (ppm)
Th (ppm)
417382
PAS
TAS
17.117
15.234
36.932
16.995
15.228
36.868
1.21
0.27
0.43
416417
PAS
TAS
17.688
15.325
37.339
17.526
15.317
37.286
1.55
0.45
0.45
416401
PAS
TAS
16.955
15.225
36.810
16.858
15.221
36.782
1.80
0.32
0.28
417368
TS high Zr/Nb
TAS
17.753
15.384
37.681
17.596
15.377
37.628
0.93
0.26
0.27
TAS
18.031
15.410
37.909
17.803
15.400
37.788
0.89
0.36
0.58
15.297
37.428
17.187
15.292
37.302
1.00*
0.22
0.69
417370
TS high Zr/NB
417387
TS high Zr/Nb
TAS
17.309
417386
TS high Zr/Nb
TAS
17.552
15.345
38.685
17.485
15.342
38.619
1.52
0.18
0.54
426502
TS high Zr/Nb
TAS
16.807
15.208
37.910
16.515
15.195
37.791
0.76
0.40*
0.50*
416410
TS high Zr/Nb
TAS
17.692
15.344
37.572
17.377
15.329
36.866
0.82
0.36
1.41
417364
TS high Zr/Nb
TAS
16.721
15.247
36.882
16.665
15.245
36.822
2.14
0.22
0.72
417366
TS high Zr/Nb
TAS
18.054
15.405
37.891
17.806
15.394
37.572
0.32
0.18
1.23
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Table 2: continued
Pb/204 Pb
207
Pb/204 Pb
208
Pb/204 Pb
206
Pb/204 PbInit
207
Pb/204 PbInit
207
Pb/204 PbInit Pb (ppm) U (ppm) Th (ppm)
Type
436672
TS high Zr/Nb Lé
18.277
15.429
38.231
18.171
15.424
38.003
1.39
0.26
1.69
436689
TS high Zr/Nb Lé
17.243
15.382
39.543
17.170
15.379
39.456
3.27
0.42
1.51
436629
TS high Zr/Nb Lé
16.165
15.310
42.260
16.126
15.308
42.215
1.49
0.10
0.35
436666
TS high Zr/Nb Lé
18.324
15.437
38.229
18.205
15.431
38.105
1.24
0.26
0.82
436707
TS high Zr/Nb Fé
18.115
15.478
39.367
18.037
15.474
39.310
1.10
0.15
0.33
410683
TS high Zr/Nb Fé
17.454
15.335
38.905
17.371
15.331
38.839
1.02
0.15
0.36
410662
TS high Zr/Nb Fé
18.377
15.470
38.326
18.120
15.458
38.147
0.20
0.91
0.19
410630
TS high Zr/Nb ICJ
17.865
15.365
37.940
17.836
15.364
37.869
1.69
0.09
0.65
436614
TS low Zr/Nb
Lé
16.926
15.339
37.765
16.861
15.336
37.674
2.65
0.31
1.32
436627
TS low Zr/Nb
Lé
18.152
15.438
38.224
18.048
15.434
38.143
1.04
0.19
0.45
436668
TS low Zr/Nb
Lé
18.410
15.486
38.567
18.252
15.478
38.452
1.42
0.39
0.87
410660
TS low Zr/Nb
Fé
18.450
15.485
38.410
18.344
15.480
38.278
1.08
0.20
0.76
Fé
18.008
15.377
38.006
17.765
15.366
37.854
1.05
0.45
0.86
15.436
38.818
18.006
15.433
38.727
1.47
0.19
0.71
410661
TS low Zr/Nb
Locality
206
Sample
410679
TS low Zr/Nb
Fé
18.080
410664
TRANS
Fé
16.959
15.207
37.709
16.789
15.199
37.635
3.78
1.40
1.86
410628
TRANS
ICJ
16.677
15.164
37.947
16.395
15.151
37.890
3.03
1.87
1.15
417390
TRANS
TAS
16.146
15.070
36.324
15.940
15.061
36.076
1.69
0.79
2.88
417388
TRANS
TAS
17.533
15.285
37.293
17.412
15.280
37.181
2.61
0.69
1.94
417373
TRANS
TAS
16.734
15.201
36.740
16.611
15.196
36.643
1.72
0.47
1.13
TAS
17.490
15.269
37.232
17.331
15.261
37.087
1.33
0.46
1.28
BCR-1 (1)
18.801
15.620
38.685
13.00
1.58
5.73
BCR-1 (2)
18.832
15.644
38.751
5.03
BCR-1 (3)
18.827
15.639
38.736
5.73
417367
TRANS
TS and PAS samples are age-corrected to 58 Ma. TRANS samples are age-corrected to 48 Ma. Measured values at Danish
Centre for Isotope Geology are for La Jolla, 143 Nd/144 Nd ˆ 0.5118568 (2SD ˆ 0.0000209); for NBS987, 87 Sr/86 Sr ˆ 0.710259
(2SD ˆ 0.000022). Pb isotopic ratios are corrected for fractionation using the NBS 981 standard values of Todt et al. (1996);
the measured values average 16.873 (2SD ˆ 0.0096) for 206 Pb/204 Pb, 15.417 (2SD ˆ 0.011) for 207 Pb/204 Pb, 36.467 (2SD ˆ
0.034) for 208 Pb/204 Pb. Within-run errors for Pb are 50.009 (% SE) and total procedure blank for Pb is 280 pg (sample size
before leaching 1 g). Three separate aliquots of BCR-1 were processed and analysed.
*Not analysed, values assumed for age correction.
A further constraint on the chronology was provided
by Tegner et al. (1998a), who obtained a 40 Ar/39 Ar
date of 562 06 Ma on a TS dyke from the Imilik
area between Tasiilaq and Langù (Fig. 2), and by a
preliminary 40 Ar/39 Ar age of 52 Ma obtained for a
dyke of the Transitional Series from Tasiilaq (R. A.
Duncan, personal communication, 2000).
The TS dykes and PAS dykes thus appear to be preand syn-break-up, i.e. intrusive equivalents of the
Lower Basalts and the main part of the flood basalts
[Main Lavas of Larsen et al. (1989)]. The transitional
dykes have no known geochemical equivalents in the
basalts, and are post-break-up, and perhaps contemporaneous with some of the post-rift gabbroic intrusions along the coast (Bernstein et al., 1998b).
The relative chronology is in accordance with previous
findings of Nielsen (1978) that the dyke swarm records
a general evolution from tholeiitic magmatism to transitional and alkaline magmatism.
RESULTS
Major element chemistry
Major element analyses are given in Table 1, and
shown in Fig. 5. The TS dykes have 47---50 wt %
silica and 2---5 wt % total alkalis. The alkali contents
are generally slightly higher in the low Zr/Nb TS dykes
than in the high Zr/Nb TS dykes. MgO contents range
from a little less than 5 wt % to 8 wt % with negatively
correlated TiO2, FeO*, P2O5, Na2O and K2O. There
is a positive correlation between MgO and Al2O3 concentrations, which range from 12 to 16%. CaO/
Al2O3 ratios are relatively constant around 075 to
085.
MgO contents for the PAS dykes range from 9 to
25 wt % and show a negative correlation with Na2O
and Al2O3 (Fig. 5). For samples with less than 15%
MgO, there is also a negative correlation with TiO2
and FeO*. Compared with the TS dykes, the PAS
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GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Fig. 3. TiO2 (wt %) against Mg number (molar Mg/(Mg ‡ Fe)). Data for Lower Basalts (Fram & Lesher, 1997; Hansen, 1997; Danish
Lithosphere Centre (DLC), unpublished data, 1995---1998) and Main Plateau Lavas (Larsen et al., 1989; DLC, unpublished data,
1995---1998). Fields for Tholeiitic Series (TS) and Picrite---Ankaramite Series (PAS) are the originally proposed fields from Gill et al. (1988).
Trace element chemistry
Fig. 4. Diagram of La/Yb against Zr/Nb used for the subdivision of
the TS dykes.
dykes are enriched in K2O, P2O5 and TiO2, i.e. similar
or higher concentrations than in the TS dykes for
higher MgO contents.
The TRANS dykes are relatively MgO- and
TiO2-poor ( 35---55 wt % and 2---35 wt %,
respectively), and there is no obvious correlation
between MgO and TiO2 (Fig. 5). For similar MgO contents, the TRANS dykes are richer in SiO2, Na2O and
K2O than the TS dykes, and poorer in TiO2, CaO and
FeO*, and they range in composition from tholeiitic
basalts and andesites to hawaiites and trachybasalts.
There is a negative correlation between MgO and
Na2O, K2O and P2O5. The CaO/Al2O3 ratios are lower
for the TRANS dykes (04---075) than for the TS dykes,
and there is a positive correlation with MgO (Fig. 5).
Trace element abundances in the TS dykes are illustrated as primitive mantle-normalized trace element
variation diagrams in Fig. 6a. The main difference in
trace element characteristics between the high Zr/Nb
TS dykes and low Zr/Nb TS dykes is that the latter
show greater enrichment in the most incompatible elements such as Ba, Nb and the light rare earth elements
(LREE). For elements to the right of Ti [Y and middle
to heavy REE (MREE---HREE)] the high Zr/Nb TS
dykes are slightly more enriched than the low Zr/Nb
TS dykes (Fig. 6a). Most of the TS dykes have a
positive Ti anomaly and negative K and Sr anomalies
relative to primitive mantle.
Figure 6b is a primitive mantle-normalized diagram
for PAS dykes with MgO contents between 9 and
15 wt %. For elements more incompatible than Sr,
the PAS dykes have trace element contents as high as
some of the TS dykes, despite the more primitive nature of the PAS dykes. For elements less incompatible
than Sr (including Y and the MREE---HREE), the
PAS dykes are less enriched than the TS dykes.
In Fig. 6c mantle-normalized trace element abundances of the least evolved TRANS samples (with
MgO 45 wt %) are shown. The pattern for the
TRANS dykes is generally similar to that of the low
Zr/Nb TS dykes, i.e. they have a relatively steep pattern in the mantle-normalized diagram.
Dykes of all three groups resemble ocean-island
basalt (OIB) compositions in that they are enriched
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Fig. 5. Major element compositions of dykes. Oxides are in wt % and chemical analyses are normalized to 100% volatile free with Fe2O3/FeO
ratios of 015 as suggested by Brooks (1976). Arrows show the direction of the evolution of liquid with simple fractionation, i.e. subtraction of
olivine, clinopyroxene, plagioclase and magnetite, using representative mineral compositions from Fram & Lesher (1997) and Hansen (1997).
in incompatible elements, and in a diagram of Zr/Y
against Nb/Y ratios (Fig. 7) most of the dykes plot in
the field of enriched Icelandic basalts. Fitton et al.
(1997, 1998b) has proposed that this diagram can be
used to distinguish between Icelandic and MORB
mantle sources.
Isotope data
A total of three PAS dykes (all from Tasiilaq), 22 TS
dykes and seven TRANS dykes were analysed for their
Sr---Nd---Pb isotopic compositions. Age-corrected Sr,
Nd and Pb isotope data for the dykes are given in
Table 2 and shown in Figs 8---11 along with data for
North Atlantic MORB and Iceland.
The TS and PAS groups have eNd ranging from
‡496 to ‡846, which is almost entirely overlapping
with present-day values from Iceland (Fig. 8). 87 Sr/
86
Sr ranges from 070328 to 070442, with the exception of one sample (436707) with 87 Sr/86 Sr 07071.
Most samples thus have slightly higher 87 Sr/86 Sr
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GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Fig. 6. Incompatible element abundances of dykes normalized to
primitive mantle (Sun & McDonough, 1989). (a) All TS dykes with
5---6 wt % MgO. Continuous and dashed black lines show average
composition for all low Zr/Nb TS and high Zr/Nb TS dykes, respectively. (b) PAS dykes with 9---15 wt % MgO compared with TS
dykes. (c) TRANS dykes with over 5 wt % MgO compared with
TS dykes.
than present-day Iceland basalts, although the PAS
dykes and some TS dykes from Tasiilaq do overlap
with Iceland compositions (Fig. 8). The low Zr/Nb
TS dykes tend to have lower eNd than the high Zr/Nb
TS dykes.
The TRANS dykes show a range in 87 Sr/86 Sr from
070327 to 070676, similar to that of the TS and PAS
dykes, but they have much lower eNd values, ranging
from ÿ418 to ‡ 254, and thus plot below the Iceland
and MORB fields in Fig. 8.
Pb isotope data for the TS and PAS dykes show a
wide range of compositions and extend to less radiogenic 206 Pb/204 Pb, 207 Pb/204 Pb and 208 Pb/204 Pb values
than reported for MORB and Iceland (Figs 9 and
10), and also to higher 208 Pb/204 Pb. 207 Pb/204 Pb vs
206
Pb/204 Pb for the TS and PAS dykes show a welldefined trend in Fig. 9a, which projects into the
Iceland and MORB fields. On a plot of 208 Pb/204 Pb
vs 206 Pb/204 Pb (Fig. 9b) some of the samples fall along a
trend that is an extension of the MORB and Iceland
fields, although there is considerably more scatter than
in 207 Pb/204 Pb vs 206 Pb/204 Pb. Figure 10 shows 208 Pb/
204
Pb vs 207 Pb/204 Pb, and again most of the dykes fall
on a well-defined trend. Dykes that define this trend
tend to have slightly elevated 208 Pb/204 Pb for a given
207
Pb/204 Pb relative to Iceland.
The TRANS dykes extend to the least radiogenic Pb
isotopic compositions measured for the East Greenland
dykes (206 Pb/204 Pb ˆ 15940---17411; 207 Pb/204 Pb ˆ
15061---15280; 208 Pb/204 Pb ˆ 36076---37890), and
do not overlap with either the Iceland or MORB
compositional fields. In terms of 207 Pb/204 Pb vs 206 Pb/
204
Pb (Fig. 9a) the transitional dykes fall along, and
extend, the trend of the tholeiitic dykes. In Fig. 9b
(208 Pb/204 Pb vs 206 Pb/204 Pb) and in Fig. 10 (208 Pb/
204
Pb vs 207 Pb/204 Pb), the four TRANS samples from
Tasiilaq plot along the same trend as the PAS dykes
and most of the TS dykes, whereas the two TRANS
samples from Fladù and I. C. Jacobsen Fjord plot at
higher 208 Pb/204 Pb.
87
Sr/86 Sr and eNd are plotted against 206 Pb/204 Pb in
Fig. 11. There is no correlation between 206 Pb/204 Pb
and 87 Sr/86 Sr for the dykes (Fig. 11a); however, there is
a weak negative correlation between eNd and 206 Pb/
204
Pb for the high Zr/Nb TS dykes (Fig. 11b). In both
plots the TS and PAS dykes plot in an array trending
towards the radiogenic end-member in Iceland (in
terms of Pb isotopes) as defined by Torfajokull (Stecher
et al., 1999).
DISCUSSION
Isotopic signature of the PAS and TS dykes
The range in Pb isotopic compositions of the TS and
PAS dykes requires that at least three components were
involved in their generation: a component with high
206
Pb/204 Pb; a component with low 206 Pb/204 Pb and
high 208 Pb/204 Pb; and a component with low 206 Pb/
204
Pb and 208 Pb/204 Pb.
The high
206
Pb/204 Pb component
In a diagram of 208 Pb/204 Pb against 207 Pb/204 Pb
(Fig. 10) most TS and PAS dyke samples fall on a
line from the least radiogenic of the dykes towards the
most radiogenic end of the Iceland array represented
by Torfajokull. That the dykes trend towards this
composition, and not the low 206 Pb/204 Pb end of the
Iceland array or MORB, is seen especially clearly in
Fig. 11b (eNd vs 206 Pb/204 Pb). The TS and PAS dykes
furthermore resemble OIB compositions in that they
are enriched in incompatible elements, and in a diagram of Zr/Y against Nb/Y ratios (Fig. 7) most of the
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Fig. 7. Nb/Y and Zr/Y variation in East Greenland dykes. The parallel lines mark the limit of Iceland data according to Fitton et al. (1997).
Compositions of primitive mantle (PM), MORB and OIB are from Sun & McDonough (1989), and lower crust (LC), bulk crust (BC) and
upper crust (UC) are from Taylor & McLennan (1995).
Fig. 8. Initial (age-corrected according to Table 2) eNd, i.e. 104 {[143 Nd/144 Ndsample (t)/143 Nd/144 NdCHUR (t)] --- 1}, and 87 Sr/86 Sr
compositions for the dykes compared with North Atlantic MORB
and Iceland. Error bars (2s) for repeat analyses of BCR-1 are
smaller than symbol size. Iceland and MORB data for this and
following figures are from Sun & Jahn (1978), Dupre & Allegre
(1980), Cohen & O'Nions (1982), Condomines et al. (1983), Ito
et al. (1987), Shirey et al. (1987), Elliott et al. (1991), Mertz et al.
(1991), Nicholson et al. (1991), Nicholson & Latin (1992), Frey et al.
(1993), Hemond et al. (1993), M
uhe et al. (1993), Hanan & Schilling
(1997), Taylor et al. (1997) and Stecher et al. (1999).
dykes plot together with enriched Icelandic basalts.
Thus both the isotopic and trace element characteristics of the TS and PAS dykes are consistent with the
involvement of the enriched Iceland plume in their
petrogenesis.
The low
206
Pb/
204
Pb components
There are no North Atlantic MORBs with Pb isotopic
compositions as unradiogenic as those found in the
Fig. 9. Pb isotopic compositions for dykes, North Atlantic MORB
and Iceland. (a) Initial 207 Pb/204 Pb against 206 Pb/204 Pb. (b) Initial
208
Pb/204 Pb against 206 Pb/204 Pb. Error bars are 2s for repeat analyses
of BCR-1. Data sources for MORB and Iceland are given in Fig. 8.
dykes, and from Figs 8---11 it is apparent that mixing
of MORB melts with an Icelandic composition (or a
relatively radiogenic dyke composition) cannot explain
the observed trends for the dykes. Unradiogenic 206 Pb/
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HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
mantle, either may account for both the low
Pb and high 208 Pb/204 Pb components.
204
208
Pb/
Crustal contamination
Fig. 10. Initial 208 Pb/204 Pb against 207 Pb/204 Pb for dykes, North
Atlantic MORB and Iceland. Error bars are 2s for repeat analyses
of BCR-1. Data sources for MORB and Iceland are given in Fig. 8.
Fig. 11. Pb, Sr and Nd isotopic compositions for dykes, North
Atlantic MORB and Iceland. (a) Initial 87 Sr/86 Sr against 206 Pb/
204
Pb. (b) Initial eNd against 206 Pb/204 Pb. Error bars (2s) for repeat
analyses of BCR-1 are smaller than symbol size. Data sources for
MORB and Iceland are given in Fig. 8.
204
Pb signatures in flood basalt provinces are usually
attributed to either crustal contamination or a contribution from the subcontinental mantle (e.g. Dickin,
1981; Mahoney et al., 1992). Because of the wide
range of 208 Pb/204 Pb in both crust and lithospheric
Contamination with upper and lower crust has been
argued to be the most plausible explanation for the
variation in the isotopic compositions of the Lower
Basalts in the East Greenland flood basalt sequence
(Fram & Lesher, 1997; Hansen & Nielsen, 1999) and
in the continental succession of ODP Legs 152 and 163
(Fitton et al., 1998a; Saunders et al., 1999). In the case
of upper-crustal (amphibolite-facies gneiss) contamination as envisaged for some of the Lower Basalts
(Hansen & Nielsen, 1999) and the later part of the
offshore ODP Leg 152 continental succession (Fitton
et al., 1997, 1998a), there is a correlation between SiO2
and several incompatible element ratios and isotopic
compositions, most notably between SiO2 and 87 Sr/
86
Sr. For those lavas from the Lower Basalts that
have relatively low 87 Sr/86 Sr ratios, Fram & Lesher
(1997) and Hansen & Nielsen (1999) proposed a
lower-crustal silicic contaminant similar to Lewisian
and East Greenland granulite-facies gneiss. The lavas
of the lower part of the continental series of ODP Leg
152 are also interpreted as contaminated with lower
crust, although a mafic rather than silicic contaminant
is inferred because of a lack of correlation between SiO2
and isotopic compositions (Fitton et al., 1998a).
The trace element characteristics for most of the
continental sequence of ODP Legs 152 and 163 and
for the Lower Basalts are consistent with crustal contamination. For example, they show relative depletion
in Nb and Ta, giving rise to relatively high La/Nb
ratios (Fitton et al., 1998b; Hansen, 1997).
The East Greenland dykes are in some respects similar in isotopic compositions to many of the contaminated lavas of the Lower Basalts and ODP Legs 152
and 163. For example, they are generally characterized
by low 206 Pb/204 Pb compared with Iceland and North
Atlantic MORB (Fig. 12). There are, however, several
notable differences indicating that the source of the
unradiogenic Pb in the TS and PAS dykes is different
from that for the lavas of the Lower Basalts and ODP
Leg 152. First, the dykes lack a positive correlation of
eNd with 206 Pb/204 Pb exhibited by lavas from the
Lower Basalts and the continental succession of ODP
Leg 152 (Fig. 12c). Such trends are expected from
contamination with Archaean or Proterozoic crust (or
EM-1 type lithospheric mantle). Furthermore, the TS
and PAS dykes lack any significant correlation of isotopic ratios with either SiO2 or trace element ratios
indicative of crustal contamination, such as La/Nb
and Nb/U (Fig. 13).
If the low 206 Pb/204 Pb compositions of the dykes
are the result of crustal contamination, then the
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Fig. 12. Isotopic compositions of dykes of this study compared
with East Greenland flood basalts, SDRS from ODP Leg 152, Iceland,
North Atlantic MORB, East Greenland crustal lithologies,
West Greenland lamproites, and average Lewisian granulite- and
amphibolite-facies gneisses. (a) 207 Pb/204 Pb against 206 Pb/204 Pb.
(b) 208 Pb/204 Pb against 207 Pb/204 Pb. (c) eNd against 206 Pb/204 Pb.
Data sources for MORB and Iceland as Fig. 8. Data for flood
basalts from Hansen & Nielsen (1999) and Peate & Stecher
(2003). Data for ODP Leg 152 from Fitton et al. (1998a). Basement
data from Leeman et al. (1976), Dickin (1981), Taylor et al. (1992)
and Kalsbeek et al. (1993). Data for West Greenland lamproites
from Nelson (1989).
contaminant must have relatively high eNd (or low Nd/
Pb) and incompatible element ratios similar to the uncontaminated magma. The granulite- and amphibolitefacies gneisses described from East Greenland are
NUMBER 11
NOVEMBER 2003
characterized by low eNd, and `normal' crustal trace
element abundances and ratios (e.g. Nb and Ta depletion), and can therefore not account for the isotopic
and trace element characteristics of the TS and PAS
dykes by contamination of Iceland plume derived
melts.
This point is illustrated in Fig. 14, which shows mixing hyperbolae for 143 Nd/144 Nd and 206 Pb/204 Pb
compositions resulting from the mixing of the TS
dyke sample with the highest 206 Pb/204 Pb (sample
410660) with a low 206 Pb/204 Pb granulite-facies gneiss
[average Lewisian of Dickin (1981)]. The mixing lines
show that although contamination with granulitefacies gneiss can account for the observed variation of
the continental succession of ODP Leg 152, such a
contaminant with low eNd cannot easily explain the
isotopic compositions of the TS and PAS dykes. If a
primitive Icelandic basalt is used instead of the dyke
composition in the mixing calculations, much less contamination is needed to shift the isotopic composition,
and the bulk mixing hyperbola intersects the dyke data
at higher 143 Nd/144 Nd and lower 206 Pb/204 Pb. However, bulk mixing still fails to account for the samples
with the lowest 206 Pb/204 Pb, and in this case, also the
samples with the highest 206 Pb/204 Pb. Selective contamination (an effective higher Pb/Nd in the low
206
Pb/204 Pb end-member) would give a better fit for
dyke samples with low 206 Pb/204 Pb, but would give a
worse fit for high 206 Pb/204 Pb dyke samples (see Fig. 14
for details).
Mafic lower crust described from the Lewisian has a
wide range of isotopic compositions (Cohen et al.,
1991). Of the samples described by Cohen et al.
(1991) two mafic gneisses have isotopic compositions
characterized by low 87 Sr/86 Sr and 206 Pb/204 Pb and
high eNd. Addition of this type of lower crust could
account for the observed trend of the dykes. However,
this requires more than 80% addition of crust to
410660 to produce the composition of the least radiogenic TS dykes assuming bulk mixing (Fig. 14). If the
primitive Icelandic composition is used as the high
206
Pb/204 Pb end-member, up to 55% bulk contamination is required to reproduce the dyke data.
Because of the heterogeneity of crustal lithologies,
crustal contamination of the TS and PAS dykes as an
explanation for the observed isotopic variations is possible. It seems unlikely, however, that contamination
with silicic upper or lower crust, as represented by
amphibolite- and granulite-facies gneisses, is significant.
Contamination with relatively depleted mafic crust
offers a better explanation because it has the appropriate isotopic composition and lacks the incompatible
element signatures characteristic of salic crust. The
degree of contamination required, however, to explain
the isotopic variation in the dykes is relatively high.
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GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Fig. 13. (a) and (b) 87 Sr/86 Sr against SiO2 and La/Nb; (c) and (d) Nb/U and La/Nb against 206 Pb/204 Pb; (e) and (f ) La/Nb against SiO2
and eNd.
Lithospheric mantle contribution
An alternative hypothesis to crustal contamination is
that the source of the low 206 Pb/204 Pb is the continental
lithospheric mantle.
Intuitively this is an attractive model, because depletion is readily understood in mantle rocks. Although
part of the subcontinental lithospheric mantle is isotopically enriched, samples of depleted continental lithospheric mantle are fairly common. Xenoliths from East
Greenland (Bernstein et al., 1998a; Hanghùj et al.,
2001) may be representative of this kind of mantle,
and recent Nd isotopic analyses of pyroxene separates
from these xenoliths show that their 143 Nd/144 Nd ratios
vary from 05122 to 05135 (K. Hanghùj, unpublished
data, 2001). A model involving a depleted mantle in
the petrogenesis is also attractive in terms of mass
balance, because small degrees of partial melting produce melts with relatively high abundances of incompatible elements from the depleted mantle, even if the
absolute abundances of incompatible elements are low
in the mantle rocks.
An example of how depletion of a primitive mantle
source by melting controls the subsequent radiogenic
isotope characteristics is shown in Table 3. The
results indicate that residual mantle rocks with eNd 4
‡40 can be generated by 15% melting of a primitive mantle 2000 Myr ago, and that the 206 Pb/
204
Pb and 87 Sr/86 Sr of the residue will be 16 and
07015, respectively. Figure 14 shows the direction
of the mixing hyperbola for simple binary mixing
of small-degree melts (05% batch melting) of this
restite with sample 410660. As can be seen from
Fig. 14, the depleted mantle has too high eNd and/or
too high 206 Pb/204 Pb to be a suitable end-member
for the dykes. The calculation in Table 3 takes into
account the degree of depletion of the primitive
mantle, degree of melting of the restite, age of depletion and trace element partition coefficients. Changing
these parameters will change the composition of
the model low 206 Pb/204 Pb end-member, but will
not significantly affect the coupling of the isotopic systems during mantle melting. If fractional melting is
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Fig. 14. Diagram of 143 Nd/144 Nd and 206 Pb/204 Pb with results of mixing calculations. Fine black lines are mixing hyperbolae for (1) bulk
mixing of average Lewisian granulite-facies gneiss (Dickin, 1981) with the most enriched (in terms of Pb isotopic composition) of the dyke
samples, 410660, (2) bulk mixing of average Lewisian granulite-facies gneiss with a primitive Icelandic basalt (Breddam, 2002), (3) bulk
mixing of Lewisian mafic crust (Cohen et al., 1991) with dyke sample 410660, and (4) bulk mixing of Lewisian mafic crust with primitive
Icelandic basalt. The compositions of the end-members are given in Table 3. Tick marks indicate amount of contamination in 10%
increments. The dotted envelope represents permissible bulk mixing hyperbolae (calculated by a Monte Carlo simulation) for mixing average
Lewisian granulite-facies gneiss and 410660, where both end-members are allowed to vary as shown by the white boxes (crust: 143 Nd/144 Nd ˆ
05106---05110 and 206 Pb/204 Pb ˆ 135---145; dyke: 143 Nd/144 Nd ˆ 05129---05130 and 206 Pb/204 Pb ˆ 180---185). Dashed lines show selective
contamination of 410660 with 15 and 25% average Lewisian crust. The lines are calculated hybridization paths assuming that Pb diffusivity is
an order of magnitude greater than Nd diffusivity (Lesher, 1990). The upper trajectory represents the geochemical evolution of the basaltic
end-member as hybridization proceeds, and the lower trajectory is the complementary path for the gneissic end-member. Chemical
equilibrium is in essence simple binary mixing represented by the intercept with the bulk mixing curve. Arrow shows direction to melts
from depleted mantle (Table 3).
Table 3: Compositions used in mixing calculations
410660
Icelandic
Lewisian
Lewisian
Primitive
Residue after 15%
0.5% melting of
basalt
granulite
mafic crust
mantle at 2000 Ma
melt extraction at 2000 Ma
residue at present
Rb (ppm)
0.635
Sr (ppm)
21.1
0.444
Sm (ppm)
Nd (ppm)
13.2
5.39
25
1.2
1.354
0.021
U (ppm)
Pb (ppm)
87
1.08
0.234
5
0.159
0.185
0.701492
0.510048
Sr/86 Sr
143
Nd/144 Nd
206
Pb/204 Pb
0.512977
18.344
0.513099
18.361
0.51082
13.950
0.513152
13.498
15.4306
0.0016
1.4684
0.0724
0.128
0.00005
0.00154
0.701492
0.510048
15.4306
0.298500
75.477900
1.082000
3.135300
0.006400
0.132400
0.701592
0.513923
16.1392
The Icelandic basalt is an olivine tholeiite from Kistufell with 10.29 wt % MgO (Breddam, 2002). Lewisian granulite
composition is from Dickin (1981), and Lewisian mafic crust from Cohen et al. (1991). Calculation of melt composition
from previously depleted mantle assumes batch melting in the garnet stability field. Melting mode from Lesher & Baker
(1997), partitioning coefficients from Shimizu & Kushiro (1975) (Sm and Nd), Green (1994) (Rb and Sr) and Lundstrom et al.
(1994) (U and Pb).
assumed (not shown) the result is a larger degree of
depletion of the restite, which is more pronounced for
87
Sr/86 Sr and 206 Pb/204 Pb than for 143 Nd/144 Nd, and
the composition is still too depleted in Nd (and Sr)
relative to Pb to be a suitable low 206 Pb/204 Pb endmember.
Therefore, straightforward depletion of mantle
material cannot provide a low 206 Pb/204 Pb component
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GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
consistent with the isotopic range of the TS and PAS
dykes. Thus, if the low 206 Pb/204 Pb component is lithospheric mantle, this mantle would have to be modified
by metasomatic processes.
Isotopic signature of the transitional dykes
The TRANS dykes have distinctly different isotopic
compositions from Icelandic basalts, with relatively
unradiogenic lead and neodymium. As for the early
TS and PAS dykes, the Pb isotopic compositions of
the TRANS dykes plot along a trend indicating the
presence of a component with high 206 Pb/204 Pb and a
component with low 206 Pb/204 Pb and variable 208 Pb/
204
Pb. The low 143 Nd/144 Nd ratios for the transitional
dykes and the lack of correlation between Nd and Pb
isotopic compositions (Fig. 11a) imply that the low
206
Pb/204 Pb and 208 Pb/204 Pb component is different
from that of the TS and PAS dykes. The high 206 Pb/
204
Pb component appears to be similar to the high
206
Pb/204 Pb component of the TS and PAS dykes,
and is assumed to be the Icelandic plume.
The origin of the low
Transitional Series
206
Pb/204 Pb component in the
The main differences between the TRANS and
TS dykes are a more pronounced enrichment in
incompatible elements and the less radiogenic Nd
isotope compositions in the former. The TRANS
dykes also extend to slightly lower 206 Pb/204 Pb.
Figure 13 show variations in silica concentration, Sr
isotopic composition and La/Nb and Nb/U ratios.
From Fig. 13e, it is evident that the TRANS dykes
with the highest SiO2 contents also have the highest
La/Nb indicative of crustal contamination. The
TRANS dykes selected for isotope analysis, however,
were all selected because of their low La/Nb
(076---104) similar to mantle values (e.g. Sun &
McDonough, 1989), and Fig. 13d shows that for these
samples, there is no correlation between La/Nb and
206
Pb/204 Pb. There is, however, a weak negative correlation of La/Nb and eNd for the same samples
(Fig. 13f ). Nb/U has been suggested as another ratio
sensitive to crustal contamination by Hofmann (1997),
who argued that mantle values for Nb/U are 437 and
that this ratio decreases with contamination by continental crust. Nb/U values for the dykes are shown
versus 206 Pb/204 Pb in Fig. 13c and, as for La/Nb,
there is no correlation with Pb isotopic composition.
If La/Nb is a sensitive indicator of crustal contamination as suggested by Thompson et al. (1983), some of
the transitional dykes appear to be generally more
affected by crustal contamination than the TS and
PAS dykes. Figure 15 shows La/Nb against eNd when
mixing a TS dyke with a crustal contaminant with eNd
Fig. 15. Diagram of eNd against La/Nb ratios for TRANS dykes. TS
and PAS dykes are shown for comparison. Hyperbola shows results of
calculations for mixing a TS dyke (410660) and a crustal contaminant with La/Nb ˆ 6 [average Greenland crust from Wedepohl et al.
(1991)] and eNd ˆ ÿ35 [average Lewisian gneiss from Dickin (1981)].
of ÿ35 (average Lewisian) and La/Nb of six [average
Greenland crust of Wedepohl et al. (1991)]. The mixing hyperbola (assuming bulk mixing) shows that
10---25% assimilation can account for the variation
in eNd and that La/Nb does not change significantly.
Similar calculations for Pb (not shown) give a similar
result, i.e. the low La/Nb values of the TRANS dykes
analysed for isotopes are not inconsistent with contamination with continental crust. Also the Pb and Nd
isotopic compositions can be modelled as 10---20%
bulk assimilation of continental crust (Fig. 14) where a
TS dyke constitutes the isotopically enriched endmember. One preliminary Os isotopic analysis of
TRANS dyke 417390 gives 186 Os/187 Os 41
(K. Hanghùj, unpublished data, 2001), which is also
consistent with crustal contamination.
The origin of the low 206 Pb/204 Pb component in the
present-day Iceland plume
Several models have been put forward to explain the
isotope characteristics of Iceland basalts. Hart et al.
(1973) suggested mixing of a plume component and
MORB to explain the variation in isotope compositions
in Iceland and along the Reykjanes Ridge. Thirlwall
(1995), however, pointed out that the Pb isotopic compositions are inconsistent with simple mixing of a plume
component and MORB, because binary mixing on
diagrams of 207 Pb/204 Pb vs 206 Pb/204 Pb and 208 Pb/
204
Pb vs 207 Pb/204 Pb will give rise to linear data arrays
between the end-members. He proposed that the offset
of Iceland data relative to MORB on these diagrams
(see Figs 9 and 10) is due to a relatively recent increase
in U/Pb in the Iceland plume source, and ternary mixing of thisÐpossibly somewhat heterogeneousÐplume
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source with MORB source and a depleted mantle
source different from MORB mantle. Kerr et al.
(1995) raised similar objections to the model of simple
mixing between a plume and a MORB source, but
interpreted the compositional range of Iceland samples
as an inherent feature of the plume. Recently, Hanan &
Schilling (1997) and Hanan et al. (2000) have proposed
that ternary mixing of plume mantle, depleted MORB
mantle and EM1 type mantle may account for the
spatial and temporal geochemical variation in Iceland.
Fitton et al. (1997) and Kempton et al. (2000) instead
proposed a model that involves four geochemical reservoirs, an enriched Iceland plume source, a depleted
Iceland plume source, a depleted sheath surrounding
the plume and finally shallow MORB mantle. Chauvel
& Hemond (2000) suggested, on the basis of trace
element chemistry and Pb, Sr and Nd isotope compositions, that the Iceland plume is composed entirely of
(heterogeneous) recycled Archaean oceanic lithosphere,
where melting of the basaltic portion (‡ harzburgite)
gives rise to alkali basalts, and melting of the gabbroic
portion (‡ harzburgite) gives rise to picrites. Skovgaard
et al. (2001) found that Os and O isotopic compositions
of Icelandic picrites are consistent with a contribution
from recycled oceanic lithosphere.
MORB mantle does not appear to contribute significantly to the East Greenland dyke swarm. Instead, the
dykes record binary mixing between a lithospheric
component and a plume component as discussed
above. In Figs 11 and 14, the dyke data trend towards
the enriched rather than the depleted portion of the
Iceland array, and therefore do not provide evidence
for both an enriched and a depleted plume source.
However, this may be due to lack of sampling of such
a depleted plume component. Because of the relatively
thick lithospheric lid during rifting, depleted portions
of the plume would melt less, or not at all, leading to
magmas dominated by the more fusible enriched
plume component. Alternatively, there is no depleted
component inherent to the plume, and the most
depleted of the Iceland samples may be products of
ternary mixing between an enriched plume source,
MORB source and a relatively depleted source of old
continental lithospheric mantle, mobilized by thermal
erosion during break-up. A mechanism for the incorporation of lithospheric mantle into the shallow asthenosphere could be transient heating at the arrival of the
Iceland hotspot under Greenland (e.g. Larsen et al.,
1996b). Plume-related delamination of continental
lithospheric mantle has also been proposed to explain
the anomalous trace element and isotopic compositions
at the 39 ---41 segment of the South West Indian
Ridge (Mahoney et al., 1992), for segments of the
Shona and Discovery ridges (Douglass et al., 1999),
and for the Kerguelen Plateau (Storey et al., 1992).
NUMBER 11
NOVEMBER 2003
MANTLE MELTING CONDITIONS
DURING CONTINENTAL RIFTING
For simple decompression melting, the depth
and degree of melting significantly influences the
composition of the mantle-derived liquids. This is in
turn dependent on the potential temperature of the
mantle, which determines at which depth the solidus
is intersected, and on the thickness of the lithosphere,
which controls at which depth melting ceases. Quantitatively addressing the melting dynamics in the
Greenland Tertiary provides constraints on the
temporal and spatial variation of the lithospheric
thickness and the thermal structure of the mantle.
Fram & Lesher (1993) showed that there is a general
positive correlation of Dy/Yb(N) (N denotes normalization to chondrite) and fractionation-corrected TiO2
for the North Atlantic province. They explained this in
terms of progressive lithospheric thinning where the
earliest melts [Lower Basalts with high Dy/Yb(N)]
were generated under thick lithosphere, and modern
ocean ridge basalts [Iceland and adjacent ridges
with low Dy/Yb(N)] under thin lithosphere. Subsequently, trace element data on sections though the
SDRS drilled during ODP Leg 152 (Fram et al.,
1998) and the East Greenland Plateau Basalts (Tegner
et al., 1998b) have been used to refine mantle
melting models, offering high temporal resolution for
the transition between continental and oceanic
magmatism.
For example, Fram et al. (1998), using La/Sm(N)
and Lu/Hf ratios in the SDRS, suggested that the lowest units are generated by 4---5% melting of a depleted
mantle source at mean pressures greater than 2 GPa,
whereas the top units are consistent with 10---12%
melting at 25---1 GPa. The data are interpreted as the
lithospheric lid thinning from 60 km to less than 25 km
in less than 5 Myr.
Tegner et al. (1998b) showed that Fe- and Ti-rich
lavas from the lower and upper portions of the East
Greenland Plateau Basalts plot in two distinct groups
in terms of La/Sm(N) and Dy/Yb(N). In the lower
part of the succession, La/Sm(N) increases regularly
up-section, whereas Dy/Yb(N) decreases. In the upper
part of the succession La/Sm(N) is much more variable, and shows a positive correlation with Dy/Yb(N).
This is interpreted in terms of falling potential temperature during the eruption of the lower portion, and
as variations in the dynamics of melt segregation and in
lithospheric thickness in the upper portion. The regular decline in mean pressure of melting coupled with an
increase in degree of melting (thinned lid effect)
observed in the SDRS off the SE Greenland margin is
not observed in the Plateau Basalts. The different REE
characteristics observed in the main groups of dykes
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HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
can likewise be understood in terms of variations in
depth and degree of melting. In the following section,
the dykes are discussed in the context of a specific mantle
melting model similar to that of Tegner et al. (1998b).
Mantle melting modelling
The mantle melting model presented in Fig. 16 is
made using the computer algorithm REEBOX first
described by Fram & Lesher (1993) and subsequently
modified by Fram et al. (1998) and Tegner et al.
(1998b). REEBOX simulates dynamic decompression
melting assuming a triangular melting regime defined
by simple corner flow.
The source mantle used in the calculation is depleted
relative to primitive mantle (Sun & McDonough, 1989)
by 05% batch melting of a spinel lherzolite. Incremental non-batch melting over a range of pressures and a
uniform melt productivity of 1% per 01 GPa is
assumed. Partitioning coefficients and reaction coefficients are from Baker & Stolper (1994), Green (1994)
and Lesher & Baker (1997). The initial mineral mode is
50% olivine, 25% orthopyroxene, 15% clinopyroxene
and 10% garnet. For the garnet---spinel transition, reaction coefficients are assumed to vary linearly between 3
and 25 GPa, and the spinel---plagioclase transition is
likewise assumed to be linear between 14 and 1 GPa.
The composition of the residue is recalculated after each
01 GPa increment of decompression melting and
adjusted for pressure-dependent phase transitions (see
Fram & Lesher, 1997). Results are shown in Fig. 16 in
terms of La/Sm(N) and Dy/Yb(N) ratios.
Because La is more incompatible than Sm during
mantle melting, an increase in La/Sm(N) corresponds
to a decrease in the mean extent of melting (F). Yb is
compatible in garnet relative to Dy, and an increase in
Dy/Yb(N) reflects an increase in the proportion of melt
derived from a garnet-bearing source, i.e. an increase in
mean pressure (P) (Fig. 16a). As discussed by Tegner
et al. (1998b), a positive correlation between F and P can
be understood in terms of lithospheric control, whereas a
negative correlation indicates changes in mantle temperature. A relative enrichment of the source mantle
(e.g. primitive mantle) would shift the curves to higher
La/Sm(N) and Dy/Yb(N). This implies that progressive depletion of the mantle source also will lead to
a positive correlation between La/Sm(N) and Dy/
Yb(N). This is seen by the slope of the individual
melting curves, which reflects progressive depletion as
mantle moves upwards through the melting column.
Results
High Zr/Nb Tholeiitic Series
All TS dykes are shown in Fig. 16b. The high Zr/Nb
TS dykes have REE characteristics somewhat similar
to the flood basalts (Tegner et al. 1998b), consistent
with starting pressures of 31---26 GPa, segregation
pressures of 25---19 GPa and 2---10% melting. In
Fig. 16c---e the high Zr/Nb TS dykes are shown by
filled symbols by locality. There is a weak negative
correlation between La/Sm(N) and Dy/Yb(N) for
Tasiilaq and Langù. Although Tasiilaq shows the
greatest range in composition, there is a substantial
overlap between all four localities in terms of La/
Sm(N). In terms of Dy/Yb(N), however, the localities
are offset relative to each other. High Zr/Nb TS
dykes from Langù and Fladù have lower Dy/Yb(N)
than those from Tasiilaq and I. C. Jacobsen Fjord.
Interestingly, within the high Zr/Nb TS group, the
oldest dykes in groups of crosscutting dykes have
lower La/Sm(N) ratios than younger dykes (not
shown). This temporal relationship is similar to what
is found for the older portion of the flood basalts
(Tegner et al., 1998b).
If the plume was centred under the Kangerlussuaq
area or further north and if the plume was a
discrete feature, one would expect that the
I. C. Jacobsen Fjord and Fladù dykes would show a
larger contribution from garnet-bearing mantle than
dykes from areas further from the plume centre.
Instead, the dyke data are consistent with elevated
temperatures in a large region (including all dykesampling localities), with local fluctuations perhaps
indicating that along-axis variations in mantle upwelling and lithospheric thickness play an important role.
Segregation pressures are similar for the various localities, although the largest range is found in Tasiilaq.
Low Zr/Nb Tholeiitic Series
The low Zr/Nb TS dykes generally plot at higher La/
Sm(N) than the high Zr/Nb TS dykes, but at similar
Dy/Yb(N). With the exception of a few samples, they
fall along the 27 GPa melting curve at segregation
pressures between 27 and 22 GPa and mean degrees
of melting lower than 5% (Fig. 16b---e). There is no
systematic change in composition with relative age for
this group.
Recalling that the low Zr/Nb TS dykes are younger
than the high Zr/Nb dykes, the data are thus consistent
with a scenario of temporal cooling of the mantle
source (relatively shallow solidus intersection) as suggested by Tegner et al. (1998b) for the Plateau Lavas.
The relatively high La/Sm(N) can be explained in two
ways. First, it may simply reflect higher segregation
pressures and accompanying low degrees of melting,
which would indicate a relatively thick lithosphere.
Second, it may suggest that the source is heterogeneous, e.g. veined, and that the low Zr/Nb TS dykes
represent a relatively larger proportion of the enriched
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Fig. 16. (a) Model curves for pooled mantle melts in terms of La/Sm(N) and Dy/Yb(N). (N) denotes normalization to chondrite. Bold
continuous curves show composition of pooled melts for different starting pressures Psolidus. Thin continuous lines contour segregation pressures
Psegregation, and dashed curves give mean extent of melting F. Arrows show effects of (1) source depletion, (2) lithospheric thinning or
incomplete pooling, and (3) fall in potential temperature. Shaded areas show compositions of Plateau Basalts from Tegner et al. (1998b).
(b)---(f) give dyke compositions with superimposed melting model from (a). [Note change of scale in (f).]
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HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
component. Importantly, the second possibility can
only be applicable together with lithospheric thickening, unless the mantle source has actually changed to
contain an enriched component during the formation
of the margin. This is because low-degree melts (high
proportion of the more fusible enriched component)
from a veined mantle would be diluted by melt fractions from higher in the melting column (small proportion of enriched component) if the thickness of the
lithosphere permits melting at similar levels as for the
high Zr/Nb TS dykes.
Near-constant solidus intersection pressures and
variable segregation pressures are also inferred from
LREE-enriched lavas from the upper portion of the
Plateau Basalts (Tegner et al., 1998b). This is partly
interpreted in terms of lithospheric thickening because
of residual mantle accumulation, and partly as variation in melt segregation dynamics. The low Zr/Nb TS
dykes are similar to these late-LREE enriched lavas,
but appear to be even more enriched. This may be
because of lower potential temperature, a slightly
more enriched mantle, or a combination of both. Isotopic data for the dykes and the Plateau Basalts
(Fig. 12) do not support an isotopically more enriched
source for the dykes. If the difference is due to greater
enrichment, it thus has a recent origin. Fram & Lesher
(1997) suggested recent LREE enrichment of the mantle source for the Lower Basalts on the basis of isotopic
and trace element compositions.
Picrite---Ankaramite Series
With the exception of two samples (416401 and
426547), the PAS dykes fall on a well-defined trend of
slightly decreasing Dy/Yb(N) with increasing La/
Sm(N) (Fig. 16b). The variation in La/Sm(N) is
greater and the Dy/Yb(N) ratios are generally higher
than for the high Zr/Nb TS dykes, indicating starting
pressures of 432 GPa to 27 GPa, segregation pressures from 26 to 20 GPa and 2---12% melting.
Assuming that the mantle source for the PAS and
TS dykes is the same, the data are in agreement with
lower-degree melts segregated from greater depths
than the high Zr/Nb dykes [causing the offset to higher
La/Sm(N) and Dy/Yb(N)] during a phase of source
mantle cooling (resulting in the trend of decreasing F
and P, which is also observed for the lower portion of
the Plateau Basalts). The PAS dykes are generally
older than the high Zr/Nb TS dykes, and the difference
in F can be due to a greater lithospheric thickness, i.e.
an expression of the lid effect, or to changes in the
`plumbing' allowing melts from greater depths to segregate more frequently, i.e. less efficient pooling. Such
a change in segregation style may be related to the
onset of sea-floor spreading.
Transitional dykes
Most of the TRANS dykes fall outside the array defined
by the model melting curves (Fig. 16f ). This is not
surprising if we recall that the transitional dykes have
Nd isotopic compositions more enriched than the TS
and PAS dykes, thus excluding the somewhat depleted
source mantle used in these calculations as the exclusive
source for their geochemical characteristics.
There is overlap in the data for the four localities.
The data from Langù, Fladù and I. C. Jacobsen Fjord
do not show any correlation between La/Sm(N) and
Dy/Yb(N), but the data from Tasiilaq (which is also
represented with most data points) show a positive
correlation.
The isotopic data discussed above indicate that the
isotopic characteristics of the TRANS dykes can be
explained by 10---25% crustal contamination of plume
melts. Figure 16f show mixing curves between the TS
dyke (410660) used for mixing calculations in Fig. 14
and lower and bulk crust (Taylor & McLennan, 1995).
The mixing curves show that contamination fails to
produce the high Dy/Yb(N) compositions, and that
more than 35% crust is needed to explain the remaining data. This amount of bulk assimilation is inconsistent with the isotopic data and implies that some other
lithospheric component is needed if the asthenospheric
(plume) end-member is the same as for the TS dykes.
This lithospheric component could be melts from a
garnet-bearing crust or lithospheric mantle, i.e. melting
of the lower crust of Taylor & McLennan in Fig. 16f
would produce highly LREE-enriched and HREEdepleted liquids. Alternatively, bulk assimilation of
crust with higher La/Sm(N) and Dy/Yb(N) than the
crustal examples in Fig. 16f could explain the data.
Implications for mantle melting and
lithospheric control
Seismic transects show that offshore crustal thickness
decreases away from the proposed plume track at the
time where sea-floor spreading was initiated (before
Chron 24r) (Dahl-Jensen et al., 1997; Holbrook et al.,
2001). If the mantle melts by passive upwelling this will
simply be an expression of a thermal gradient along the
margin. The modelling of the dykes indicates that there
was no systematic thermal zonation of the mantle
source (plume), i.e. there is no evidence for increased
degrees of melting close to the proposed plume centre
relative to the more distal parts. This may indicate that
the mantle upwelling is not passive, and that melt
productivity is determined by active upwelling as well
as mantle temperature. Active upwelling can also
explain how low to moderate degrees of melting,
equivalent to those seen for MORBs, can lead to the
anomalously thick crust of the SDRS found offshore
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(Fram et al., 1998). If active upwelling is assumed
under the East Greenland margin, the degree of melting calculated for the dykes would have no bearing on
melt productivity, which may increase northwards in a
systematic fashion as observed offshore.
When the dykes are compared with the flood basalts,
they do extend to lower Dy/Yb(N), which at constant
lithospheric thickness (and the same source) would be
indicative of lower potential temperature. Recalling
the isotopic composition of the dykes and the main
part of the flood basalts (Fig. 12), it is evident that
the low 206 Pb/204 Pb component present in the dykes is
either lacking or sampled less in the flood basalts. So,
although there is no systematic change in apparent
temperature and source composition within the dyke
swarm (i.e. towards the plume centre), there does
appear to be a difference between the dykes and the
flood basalts. This difference must be related to source
characteristics (because of the difference in isotopic
composition), and may or may not reflect differences
in melting dynamics. The source difference may be
related to the fact that whereas the dyke swarm
intruded basement of Archaean and Proterozoic age,
the main part of the flood basalts may overlie basement
of Caledonian age, which may lack the depleted lithospheric mantle component envisaged as the source of
the low 206 Pb/204 Pb component in the dykes.
The quantitative modelling of REE data for the
dykes supports the conclusion of Tegner et al. (1998b)
that the mantle source along the rifted margin cooled
during flood basalt volcanism. The temporal change
from the progressive cooling trend observed in the high
Zr/Nb TS dykes, PAS dykes and the lower portion of
the Plateau Basalts, to LREE-enriched melts generated
at near-constant Psolidus (the low Zr/Nb TS dykes and
late upper portion of the Plateau Basalts) is consistent
with smaller-degree melts from a possibly heterogeneous mantle segregating at more variable pressures.
This indicates increased lithospheric thickness, possibly
caused by accumulation of residual mantle, and variability in melt segregation dynamics.
The data for the TRANS dykes are ambiguous and
difficult to compare directly with the TS dykes. This is
because an additional source or contaminant is
required in the genesis of the TRANS dykes as shown
by the isotope data, and the calculations of F and P
depend on which additional component is chosen.
SUMMARY AND CONCLUSIONS
Dykes of the East Greenland coastal dyke swarm can be
divided into three main groups: pre- and syn-break-up
tholeiitic picrite---ankaramite dykes (PAS); syn-breakup tholeiitic dykes (TS dykes); post-break-up, transitional-to-alkaline dykes (TRANS dykes).
NUMBER 11
NOVEMBER 2003
Pre- and syn-break-up dykes
Of the early dykes, the most abundant group is the TS
dykes. This group consists of moderately LREEenriched tholeiites, with major element compositions
similar to the East Greenland flood basalts. This group
can be further subdivided into a high Zr/Nb group
and a low Zr/Nb group, where the latter is generally
more enriched in terms of incompatible elements and
Sr---Nd---Pb isotopic compositions. The PAS dykes
are much less abundant than the TS dykes. They are
equivalent to some of the lavas in the Lower Basalts
and have incompatible element characteristics that
preclude them as parental to the TS dykes. Isotopic
compositions for the TS and PAS dykes partly overlap
with those for Iceland, but Pb isotopic compositions
extend to less radiogenic values than those seen in either
Iceland or North Atlantic MORB. The isotopically
depleted source required to account for the isotopic
variation of the early tholeiitic dykes is interpreted as
subcontinental lithospheric mantle with low 87 Sr/86 Sr
and 206 Pb/204 Pb and high eNd. The different incompatible trace element ratios of the groups are interpreted
to represent different degrees and depths of melting
within the proto-Icelandic plume.
Comparison between dykes from different segments
of the East Greenland margin does not show a systematic compositional change with distance from the
presumed proto-Icelandic plume centre, indicating
that the systematic changes in crustal thickness offshore
may be attributed to active upwelling. Subtle geochemical differences within the dyke swarm can probably be attributed to variations in melting regimes and
possibly geochemical heterogeneity of the lithosphere.
Post-break-up dykes
The post-break-up TRANS dykes have more alkaline
compositions and are enriched in LREE relative to
most of the early tholeiitic dykes. The TRANS dykes
are isotopically distinct from Iceland and MORB, both
in terms of 206 Pb/204 Pb ratios (159---174) and eNd
(---418 to ‡254). The isotopic characteristics are interpreted in terms of contamination of Iceland plume
melts with continental crust.
The dyke swarm in the context of the
North Atlantic Igneous Province
Pre- and syn-break-up dykes from all localities appear
to have the enriched (relative to MORB) protoIcelandic plume as the most significant source
component, and there is no evidence of a contribution
from a MORB mantle source, or a depleted component
inherent to the plume. Instead, the data suggest contribution from an isotopically depleted lithospheric
source. In terms of models for the formation of volcanic
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HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
rifted margins, the data presented here thus lend no
support to models that involve substantial melt
generation in reservoirs other than enriched plume
mantle, e.g. so-called non-plume models, where the
primary source would be expected to be MORB mantle (e.g. Mutter et al., 1988; King & Anderson, 1995).
Models in which the continental lithospheric mantle is
the main source region for flood basalt volcanism
(Gallagher & Hawkesworth, 1992) are likewise not
supported by the data.
Quantitative modelling of REE data show that the
PAS and high Zr/Nb TS dykes can be generated by
moderate to low degrees of melting of a slightly
depleted mantle at decreasing mean pressures of melting, consistent with a declining temperature during
flood basalt volcanism. The low Zr/Nb TS dykes represents lower degrees of melting at near-constant temperatures but at variable segregation pressures,
reflecting local variations in segregation dynamics
and lithospheric control. REE systematics of the
dykes cannot be explained by a systematic rise in temperature towards the plume centre, and instead a
model for the formation of the margin involving active
upwelling and local lithospheric control is preferred.
ACKNOWLEDGEMENTS
Kent Brooks and Troels Nielsen are thanked for sharing their ideas, knowledge and enthusiasm about the
geology of East Greenland. Both have contributed tremendously to this study in innumerable ways. Many
colleagues and guests at the Danish Lithosphere Centre
provided constructive comments and dicussions; we
especially wish to thank Henriette Hansen, who
endured particularly numerous discussions and versions of this work, and Chip Lesher for discussions
about mantle melting and more. David Christie,
Andy Ungerer and Chi Meridith helped with ICPMS analyses at COAS, Oregon State University.
Andy Saunders and Richard Arculus are thanked for
constructive and helpful reviews. This work was
funded by the Danish National Research Foundation.
REFERENCES
Baker, M. B. & Stolper, E. M. (1994). Determining the composition
of high-pressure mantle melts using diamond aggregates.
Geochimica et Cosmochimica Acta 58, 2811---2827.
Bernstein, S., Kelemen, P. B. & Brooks, C. K. (1998a). Depleted
spinel harzburgite xenoliths in Tertiary dykes from East
Greenland: restites from high degree melting. Earth and Planetary
Science Letters 154, 221---235.
Bernstein, S., Kelemen, P. B., Tegner, C., Kurz, M. D., Blusztajn, J.
& Brooks, C. K. (1998b). Post-breakup basaltic magmatism along
the East Greenland Tertiary rifted margin. Earth and Planetary
Science Letters 160, 845---862.
Breddam, K. (2002). Kistufell: primitive melt from the Iceland
mantle plume. Journal of Petrology 43, 345---373.
Bridgwater, D., Davies, F. B., Gill, R. C. O., Gorman, B. E.,
Myers, J. S., Pedersen, S. & Taylor, P. (1978). Precambrian and
Tertiary geology between Kangerlugssuaq and Angmagssalik,
East Greenland. Grùnlands Geologiske Undersùgelse, Rapport 83, 1---17.
Brooks, C. K. (1973). Rifting and doming in southern East
Greenland. Nature 244, 23---25.
Brooks, C. K. (1976). The Fe2O3/FeO ratio of basalt analyses: an
appeal for a standardized procedure. Bulletin, Geological Society of
Denmark 25, 117---120.
Chauvel, C. & Hemond, C. (2000). Melting a complete section of
recycled oceanic crust: trace element and Pb isotopic evidence
from Iceland. Geochemistry, Geophysics, Geosystems 2000-02-14.
Cheatham, M. M., Sangrey, W. F. & White, W. M. (1993). Sources
of error in external calibration ICP-MS analysis of geological
samples and an improved non-linear drift correction procedure.
Spectrochimica Acta 48B, E487---E506.
Cohen, R. S. & O'Nions, R. K. (1982). The lead, neodymium and
strontium isotopic structure of ocean ridge basalts. Journal of
Petrology 23, 299---324.
Cohen, A. S., O'Nions, R. K. & O'Hara, M. J. (1991). Chronology
and mechanism of depletion in Lewisian granulites. Contributions to
Mineralogy and Petrology 106, 142---153.
Condomines, M., Gr
onvold, K., Hooker, P. J., Muehlenbachs, K.,
O'Nions, R. K., Oskarsson, N. & Oxburgh, E. R. (1983).
Helium, oxygen, strontium and neodymium isotopic relationships
in Icelandic volcanics. Earth and Planetary Science Letters 66,
125---136.
Dahl-Jensen, T., Holbrook, W. S., Hopper, J. R., Korenaga, J.,
Larsen, H. C., Kelemen, P. B., Detrick, R. & Kent, G. (1997).
Structure of the upper crust at the SE Greenland volcanic rifted
margin out to Chron 21 times. EOS Transactions, American
Geophysical Union 78, F668.
Dickin, A. P. (1981). Isotope geochemistry of Tertiary igneous rocks
from the Isle of Skye, N.W. Scotland. Journal of Petrology 22,
155---189.
Douglass, J., Schilling, J.-G. & Fontignie, D. (1999). Plume---ridge
interactions of the Discovery and Shona mantle plumes with the
southern Mid-Atlantic Ridge (40 ---55 S). Journal of Geophysical
Research 104, 2941---2962.
Dupre, B. & Allegre, C. J. (1980). Pb---Sr---Nd isotopic correlation and
the chemistry of the North Atlantic mantle. Nature 286, 17---22.
Elliott, T. R., Hawkesworth, C. J. & Gr
onvold, K. (1991). Dynamic
melting of the Iceland plume. Nature 351, 201---206.
Escher, A. & Watt, W. S. (1976). Summary of the geology of
Greenland. In: Escher, A. & Watt, W. S. (eds) Geology of
Greenland. Copenhagen: Geological Survey of Greenland,
pp. 12---15.
Fitton, J. G., Saunders, A. D., Norry, M. J., Hardarson, B. S. &
Taylor, R. N. (1997). Thermal and chemical structure of the
Iceland plume. Earth and Planetary Science Letters 153, 197---208.
Fitton, J. G., Hardarson, B. S., Ellam, R. M. & Rogers G. (1998a).
Sr-, Nd-, and Pb-isotopic composition of volcanic rocks from the
southeast Greenland margin at 63 N: temporal variation in
crustal contamination during continental breakup. In:
Larsen, H. C., Saunders, A. D. & Wise, S. W., Jr (eds) Proceedings
of the Ocean Drilling Program, Scientific Results, 152. College Station,
TX: Ocean Drilling Program, pp. 351---357.
Fitton, J. G., Saunders, A. D., Larsen, L. M., Hardarson, B. S. &
Norry, M. J. (1998b). Volcanic rocks from the East Greenland
margin at 63 N: composition, petrogenesis, and mantle sources.
In: Larsen, H. C., Saunders, A. D. & Wise, S. W., Jr (eds)
2109
JOURNAL OF PETROLOGY
VOLUME 44
Proceedings of the Ocean Drilling Program, Scientific Results, 152.
College Station, TX: Ocean Drilling Program, pp. 331---350.
Fram, M. S. & Lesher, C. E. (1993). Geochemical constraints on
mantle melting during creation of the North Atlantic basin.
Nature 363, 712---715.
Fram, M. S. & Lesher, C. E. (1997). Generation and polybaric
differentiation of magmas of the East Greenland Early Tertiary
flood basalts. Journal of Petrology 38, 231---275.
Fram, M. S., Lesher, C. E. & Volpe, A. M. (1998). Mantle melting
systematics: the transition from continental to oceanic volcanism
on the southeast Greenland margin. In: Larsen, H. C.,
Saunders, A. D. & Wise, S. W., Jr (eds) Proceedings of the Ocean
Drilling Program, Scientific Results, 152. College Station, TX: Ocean
Drilling Program, pp. 373---386.
Frey, F. A., Walker, N., Stakes, D., Hart, S. R. & Nielsen, R.
(1993). Geochemical characteristics of basaltic glasses from the
AMAR
and FAMOUS axial valleys, Mid-Atlantic Ridge
(36 ---37 N): petrogenetic implications. Earth and Planetary Science
Letters 115, 117---136.
Gallagher, K. & Hawkesworth, C. J. (1992). Dehydration
melting and the generation of continental flood basalts. Nature
358, 57---59.
Gill, R. C. O., Nielsen, T. F. D., Brooks, C. K. & Ingram, G. A.
(1988). Tertiary volcanism in the Kangerlugssuaq region, E.
Greenland: trace-element geochemistry of the Lower Basalts and
tholeiitic dyke swarms. In: Morton, A. C. & Parson, L. M. (eds)
Early Tertiary Volcanism and the Opening of the NE Atlantic. Geological
Society, London, Special Publications 39, 161---179.
Govindaraju, K. (1989). Compilation of working values and sample
descriptions for 272 geostandards. Geostandards Newsletters 13,
1---113.
Govindaraju, K. (1994). Compilation of working values and sample
descriptions for 383 geostandards. Geostandards Newsletters Special
Issue 18, 1---158.
Green, T. H. (1994). Experimental studies of trace-element
partitioning applicable to igneous petrogenesisÐSedona 16 years
later. Chemical Geology 117, 1---36.
Hanan, B. B. & Schilling, J.-G. (1997). The dynamic evolution of
the Iceland mantle plume: the lead isotope perspective. Earth and
Planetary Science Letters 151, 43---60.
Hanan, B. B., Blichert-Toft, J., Kingsley, R. & Schilling, J.-G.
(2000). Depleted Iceland mantle plume geochemical signature:
artifact of multi-component mixing? Geochemistry, Geophysics,
Geosystems 4, 2000-2-14.
Hanghùj, K., Kelemen, P. B., Bernstein, S., Blusztajn, J. & Frei, R.
(2001). The Wiedemann Fjord mantle xenoliths, a record of
cratonic mantle formation by melt depletion in the Archaean.
Geochemistry, Geophysics, Geosystems 2, 2000GC000085.
Hansen, H. (1997). Studies of basalt petrogenesis in contrasting
tectonic settings of the North Atlantic Basalt Province. Petrogenesis of plagioclase ultraphyric basalts from Iceland and the Lower
Basalts of central East Greenland. Ph.D. thesis, University of
Copenhagen.
Hansen, H. & Nielsen, T. F. D. (1999). Crustal contamination in
Palaeogene East Greenland flood basalts: plumbing system
evolution during continental rifting. Chemical Geology 157, 89---118.
Hart, S. R., Schilling, J.-G. & Powell, J. L. (1973). Basalts from
Iceland and along the Reykjanes Ridge: Sr isotope geochemistry.
Nature 246, 104---107.
Hemond, C., Arndt, N. T., Lichtenstein, U. & Hofmann, A. W.
(1993). The heterogeneous Iceland plume: Nd---Sr---O isotopes
and trace element constraints. Journal of Geophysical Research 98,
15833---15850.
NUMBER 11
NOVEMBER 2003
Henriksen, N. & Higgins, A. K. (1976). East Greenland Caledonian
fold belt. In: Escher, A. & Watt, S. W. (eds) Geology of Greenland.
Copenhagen: Geological Survey of Greenland, pp. 182---246.
Hofmann, A. W. (1997). Mantle geochemistry: the message from
oceanic volcanism. Nature 385, 219---229.
Holbrook, W. S., Larsen, H. C., Korenaga, J., Dahl-Jensen, T.,
Reid, I. D., Kelemen, P. B., Hopper, J. R., Kent, G. M.,
Lizarralde, D., Bernstein, S. & Detrick, R. S. (2001). Mantle
thermal structure and active upwelling during continental
breakup in the North Atlantic. Earth and Planetary Science Letters
190, 251---266.
Ito, E., White, W. M. & G
opel, C. (1987). The O, Sr, Nd and
Pb isotope geochemistry of MORB. Chemical Geology 62,
157---176.
Kalsbeek, F., Austrheim, H., Bridgwater, D., Hansen, B. T.,
Pedersen, S. & Taylor, P. N. (1993). Geochronology of Archaean
and Proterozoic events in the Ammasalik area, South-East
Greenland, and comparisons with the Lewisian of Scotland and
the Nagsugtoqidian of West Greenland. Precambrian Research 62,
239---279.
Karson, J. A., Brooks, C. K., Storey, M. & Pringle, M. S. (1998).
Tertiary faulting and pseudotachylytes in the East Greenland
volcanic rifted margin: seismogenic faulting during magmatic
construction. Geology 26, 39---42.
Kempton, P. D., Fitton, J. G., Saunders, A. D., Nowell, G. M.,
Taylor, R. N., Hardarson, B. S. & Pearson, G. (2000). The
Iceland plume in space and time: a Sr---Nd---Pb---Hf study of the
North Atlantic rifted margin. Earth and Planetary Science Letters 177,
255---271.
Kerr, A. C., Saunders, A. D., Tarney, J., Berry, N. H. & Hards, V.
L. (1995). Depleted mantle-plume geochemical signatures: no
paradox for plume theories. Geology 23, 843---847.
King, S. D. & Anderson, D. L. (1995). An alternative mechanism of
flood basalt formation. Earth and Planetary Science Letters 136,
269---279.
Klausen, M. B. & Larsen, H. C. (2002). The East Greenland coastparallel dyke swarm and its role in continental breakup. In:
Menzies, M. A., Klemperer, S. L., Ebinger, C. J. & Baker, J. A.
(eds) Volcanic Rifted Margins. Geological Society of America, Special
Papers 362, 133---158.
Kystol, J. & Larsen, L. M. (1999). Analytical procedures in the
Rock Geochemical Laboratory of the Geological Survey of
Denmark and Greenland. Geological Survey of Greenland Bulletin
184, 59---62.
Larsen, H. C. & Saunders, A. D. (1998). Tectonism and volcanism
at the SE Greenland rifted margin: a record of plume impact and
later continental rupture. In: Larsen, H. C., Saunders, A. D. &
Wise, S. W., Jr (eds) Proceedings of the Ocean Drilling Program,
Scientific Results 152. College Station, TX: Ocean Drilling
Program, pp. 503---533.
Larsen, L. M., Watt, W. S. & Watt, M. (1989). Geology and
petrology of the Lower Tertiary plateau basalts of the Scoresby
Sund region, East Greenland. Geological Survey of Greenland Bulletin
157, 1---164.
Larsen, L. M., Watt, W. S., Tegner, C., Storey, M. & Stecher, O.
(1996a). High-Ti and low-Ti magmas within the central East
Greenland Tertiary plateau basalts. EOS Transactions, American
Geophysical Union 77(Supplement), 826.
Larsen, T. B., Yuen, D. A. & Smedsmo, L. J. (1996b). Thermomechanical modeling of pulsation tectonics and consequences on
lithospheric dynamics. Geophysical Research Letters 23, 217---220.
Lawver, L. A. & M
uller, R. D. (1994). Iceland hotspot track.
Geology 22, 311---314.
2110
HANGHéJ et al.
GEOCHEMISTRY OF EAST GREENLAND TERTIARY DYKE SWARM
Leeman, W. P., Dasch, E. J. & Kays, M. A. (1976). 207 Pb/206 Pb
whole-rock age of gneisses from the Kangerlugssuaq area, eastern
Greenland. Nature 263, 469---471.
Lesher, C. E. (1990). Decoupling of chemical and isotopic exchange
during magma mixing. Nature 344, 235---237.
Lesher, C. E. & Baker, M. B. (1997). Near-solidus phase relations
of mantle peridotite at 36---5 GPa. EOS Transactions, American
Geophysical Union 78, F812.
Lundstrom, C. C., Shaw, H. F., Ryerson, F. J., Phinney, D. L.,
Gill, J. B. & Williams, Q. (1994). Compositional controls on
the partitioning of U, Th, Ba, Pb, Sr and Zr between
clinopyroxene and haploblastic melts: implications for uranium
series disequilibria in basalts. Earth and Planetary Science Letters 128,
407---423.
Mahoney, J. J. (1987). An isotopic survey of Pacific oceanic
plateaus: implications for their nature and origin. In:
Mahoney, J. J., Le Roex, A. P., Peng, Z., Fisher, R. L. &
Natland, J. H. (1992). Southwestern limits of Indian Ocean
Ridge mantle and the origin of low 206 Pb/204 Pb mid-ocean ridge
basalt: isotope systematics of the Central Southwest Indian Ridge.
Journal of Geophysical Research 97, 19771---19790.
Mertz, D. F., Devey, C. W., Todt, W., Stoffers, P. & Hofmann, A. W.
(1991). Sr---Nd---Pb isotope evidence against plume--asthenosphere mixing north of Iceland. Earth and Planetary
Science Letters 107, 243---255.
M
uhe, R., Devey, C. W. & Bohrmann, H. (1993). Isotope and trace
element geochemistry of MORB from the Nansen---Gakkel Ridge
at 86 north. Earth and Planetary Science Letters 120, 103---109.
Mutter, J. C., Buck, W. R. & Zehnder, C. Z. (1988). Convective
partial melting. 1. A model for the formation of thick basaltic
sequences during the initiation of spreading. Journal of Geophysical
Research 93, 1031---1048.
Myers, J. S. (1980). Structure of the coastal dyke swarm and
associated plutonic intrusions of East Greenland. Earth and
Planetary Science Letters 46, 407---418.
Nelson, D. R. (1989). Isotopic characteristics and petrogenesis of the
lamproites and kimberlites of central west Greenland. Lithos 22,
265---274.
Nicholson, H. & Latin, D. (1992). Olivine tholeiites from Krafla,
Iceland: evidence for variations in melt fraction within a plume.
Journal of Petrology 33, 1105---1124.
Nicholson, H., Condomines, M., Fitton, J. G., Fallick, A. E.,
Gronvold, K. & Rogers, G. (1991). Geochemical and isotopic
evidence for crustal assimilation beneath Krafla, Iceland. Journal
of Petrology 32, 1005---1020.
Nielsen, T. F. D. (1978). The Tertiary dike swarms of the
Kangerlugssuaq area, East Greenland; an example of magmatic
development during continental break-up. Contributions to Mineralogy and Petrology 67, 63---78.
Nielsen, T. F. D. & Brooks, C. K. (1981). The East Greenland rifted
continental margin: an examination of the coastal flexure. Journal
of the Geological Society, London 138, 559---568.
Peate, D. W. & Stecher, O. (2003). Pb isotope evidence for
contributions from different Iceland mantle components in
Palaeogene East Greenland flood basalts. Lithos 67, 39---52.
Pedersen, A. K., Watt, M., Watt, W. S. & Larsen, L. M. (1997).
Structure and stratigraphy of the early Tertiary basalts of the
Blosseville Kyst, East Greenland. Journal of the Geological Society,
London 154, 565---570.
Pyle, D. G., Christie, D. M., Mahoney, J. J. & Duncan, R. A.
(1995). Geochemistry and geochronology of ancient southeast
Indian and southwest Pacific seafloor. Journal of Geophysical
Research 100, 22261---22282.
Saunders, A. D., Fitton, J. G., Kerr, A. C., Norry, M. J. & Kent, R.
W. (1997). The North Atlantic Igneous Province. In:
Mahoney, J. J. & Coffin, M. L. (eds) Large Igneous Provinces.
Washington, DC: American Geophysical Union, pp. 45---93.
Saunders, A. D., Kempton, P. D., Fitton, J. G. & Larsen, L. M.
(1999). Sr, Nd and Pb isotopes and trace element geochemistry of
basalts from the Southeast Greenland Margin. In: Larsen, H. C.,
Duncan, R. D., Allan, J. F. & Brooks, C. K. (eds) Proceedings of the
Ocean Drilling Program, Scientific Results, 163. College Station, TX:
Ocean Drilling Program, pp. 77---93.
Shimizu, N. & Kushiro, I. (1975). The partitioning of rare earth
elements between garnet and liquid at high pressures: preliminary
experiments. Geophysical Research Letters 2, 414---416.
Shirey, S. B., Bender, J. F. & Langmuir, C. H. (1987). Threecomponent isotopic heterogeneity near the Oceanographer transform, Mid-Atlantic Ridge. Nature 325, 217---223.
Skovgaard, A. C., Storey, M., Baker, J., Blusztajn, J., Hart, S. R.
(2001). Osmium---oxygen isotopic evidence for a recycled and
strongly depleted component in the Iceland mantle plume. Earth
and Planetary Science Letters, 194, 259---275.
Stecher, O., Carlson, R. W. & Gunnarson, B. (1999). Torfaj
okull:
a radiogenic end-member of the Iceland Pb-isotopic array. Earth
and Planetary Science Letters 165, 117---127.
Storey, M., Kent, R., Saunders, A. D., Hergt, J., Salters, V. J.,
Whitechurch, H., Sevigny, J. H., Thirlwall, M. F., Leat, P.,
Ghose, N. C. & Gifford, M. (1992). Lower Cretaceous volcanic
rocks on continental margins and their relationship to the
Kerguelen Plateau. In: Barbu, E. M. (ed.) Proceedings of the Ocean
Drilling Program, Scientific Results, 120. College Station, TX: Ocean
Drilling Program, pp. 33---53.
Sun, S.-S. & Jahn, B. (1975). Lead and strontium isotopes in postglacial basalts from Iceland. Nature 255, 527---530.
Sun, S.-S. & McDonough, W. F. (1989). Chemical and isotopic
systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders, A. D. & Norry, M. J. (eds)
Magmatism in the Ocean Basins. Geological Society, London, Special
Publications 42, 313---345.
Taylor, P. N., Kalsbeek, F. & Bridgwater, D. (1992). Discrepancies
between neodymium, lead and strontium model ages from the
Precambrian of southern East Greenland: evidence for a
Proterozoic granulite-facies event affecting Archean gneisses.
Chemical Geology 94, 281---291.
Taylor, R. N., Thirlwall, M. F., Murton, B. J., Hilton, D. R. &
Gee, M. A. M. (1997). Isotopic constraints on the influence
of the Icelandic plume. Earth and Planetary Science Letters 148,
E1---E8.
Taylor, S. R. & McLennan, S. M. (1995). The geochemical evolution
of the continental crust. Reviews in Geophysics 33, 241---265.
Tegner, C., Duncan, R. A., Bernstein, S., Brooks, C. K., Bird, D. K.
& Storey, M. (1998a). 40 Ar---39 Ar geochronology of Tertiary
mafic intrusions along the East Greenland rifted margin: relation
to flood basalts and the Iceland hotspot track. Earth and Planetary
Science Letters 156, 75---88.
Tegner, C., Lesher, C. L., Larsen, L. M. & Watt, W. S. (1998b).
Evidence from the rare-earth-element record of mantle melting
for cooling of the Tertiary Iceland plume. Nature 395, 591---594.
Thirlwall, M. F. (1995). Generation of the Pb isotopic characteristics of the Iceland plume. Journal of the Geological Society, London
152, 991---996.
Thompson, R. N., Morrison, A. P., Dickin, A. P. & Hendry, G. L.
(1983). Continental flood basalts . . . arachnids rule OK? In:
Hawkesworth, C. J. & Norry, M. J. (eds) Continental Basalts and
Mantle Xenoliths. Nantwich: Shiva, pp. 158---185.
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JOURNAL OF PETROLOGY
VOLUME 44
Todt, W., Cliff, R. A., Hanser, A. & Hofmann, A. W. (1996).
Evaluation of a 202 Pb---205 Pb double spike for high-precision lead
isotope analyses. In: Basu, A. & Hart, S. R. (eds) Earth Processes:
Reading the Isotopic Code. Geophysical Monograph, American Geophysical
Union 95, 429---437.
Wager, L. R. (1935). Geological investigations in East Greenland.
Part II. Geology of Kap Dalton. Meddelelser om Grùnland 105(3),
1---32.
Wager, L. R. (1947). Geological investigations in East Greenland.
Part IV. The stratigraphy and tectonics of Knud Rasmussens
Land. Meddelelser om Grùnland 134(5), 1---64.
NUMBER 11
NOVEMBER 2003
Wager, L. R. & Deer, W. A. (1938). A dyke swarm and coastal
flexure in East Greenland. Geological Magazine 75, 39---46.
Wedepohl, K., Heinrichs, H. & Bridgwater, D. (1991). Chemical
characteristics and genesis of the quartz---feldspathic rocks in the
Archean crust of Greenland. Contributions to Mineralogy and
Petrology 107, 163---179.
White, R. S. & McKenzie, D. (1989). Magmatism at rift zones: the
generation of volcanic continental margins and flood basalts.
Journal of Geophysical Research B94, 7685---7729.
White, R. S. & McKenzie, D. (1995). Mantle plumes and flood
basalts. Journal of Geophysical Research 100, 17543---17585.
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