SKAERGAARD PETROGRAPHIC SUITE
Introduction
The 1974 University of Oregon Expedition collected the rocks for this suite to the
Skaergaard Intrusion. The expedition was under the leadership of Dr. A. R. McBirney. The
expedition included six geologists from the University of Oregon and geologists from Oregon
State University, The University of Saskatchewan, Stellenbosch University, The Lunar Science
Laboratory, and the Geophysics Laboratory of the Carnegie Institution. The expedition spent
three weeks in the intrusion.
Reference
Wager, L. R. and Deer, W. A., 1939, Geological Investigations in East Greenland, pt. 3. The
Petrology of the Skaergaard Intrusion, Kangera lugssuag, East Greenland, Meddelelser
om Grb'lnland, v. 105 #4.
Wager L. R. and Brown, G. M., 1966, The Skaergaard Intrusion East Greenland in Layered
Igneous Rocks, Freeman, 588p.
McBirney, A. R., 2007, Igneous Petrology, 3rd ed: Jones and Bartlett, p. 232 264.
Revised October 26, 2010
Skaergaard Intrusion
Maps and Cross Sections
Figure 1. Simplified map of the Skaergaard intrusion. Units of the Layered Series are
Lower Zone (LZ) a, b, and c; Middle Zone (MZ); and Upper Zone (UZ) a, b, and c. The
Marginal Border Series (MBS) and Upper Border Series (UBS) merge in the southern
part of the map and are not shown separately (from McBirney, A. R., 1993, Figure 6-21.
3
Skaergaard Intrusion
4
Figure 2. Cross section from A to B of Figure 1.
Figure 3. Schematic north-south section through the Skaergaard intrusion showing its inferred
original form before tilting and erosion. The line of present sea level indicates the amount of
flexure toward the south. The crosshatched pattern indicates a later intrusion known as the
Basistoppen Sheet. The structure and topography above the present surface is inferred from the
estimated original depth of the intrusion and its relationship to contemporaneous volcanic rocks. The
root zone is constructed from geophysical data (from McBirney, A. R., 1993, Figure 6-22, a).
Skaergaard Intrusion
5
Figure 4. Simplified east-west section through the Skaergaard intrusion at its present level of
exposure. View is toward the south looking down dip (from McBirney, A. R., 1993, Figure 622, b).
Skaergaard Intrusion
Figure 5. Stratigraphic column of the Skaergaard intrusion
(from McBirney, A. R., 1993, Figure 6-24).
6
Skaergaard Intrusion
7
Figure 6. Location map of Western Minerals samples (Oregon Numbers). Numbers refer to Western
Minerals field numbers.
Skaergaard Intrusion
8
Sample Descriptions
The first number refers to the UNI collection number. The second number refers to the
sample site on the sketch map (Figure 6).
UNI-118 (Oregon No. 7): Chilled Margin. This fine grained basalt formed when the Skaergaard
magma was chilled against the country rock as it was intruded. This rock contains
uniformly sized grains of olivine, plagioclase, magnetite, and clinopyroxene. This
sample was collected along the northwest margin of the intrusion on the north side of
Uttentals Sund.
UNI-119 (Oregon No. 8): Gabbro Picrite. This sample is a medium grained olivine rich gabbro
contained as blocks in the marginal zone of the intrusion along its northern contact. The
rock contains abundant euhedral olivine crystals in a matrix of plagioclase, magnetite,
and poikelitic pyroxene. The olivine is Fo81 and is the most magnesium rich in the
intrusion. This sample was collected from the marginal border group on Uttentals
Plateau.
UNI-120 (Oregon No. 4): Perpendicular Feldspar Rock. This sample is composed of a medium
grained olivine gabbro containing elongated feldspar crystals. The plagioclase crystals
contain cores of An72 and rims of An77 and are elongated parallel to their c axis. These
plagioclase crystals grew perpendicular to the intrusion contact in what is called the
tranquil division of the marginal border group. The groundmass contains euhedral to
subhedral crystals of olivine, plagioclase, magnetite, and orthopyroxene, enclosed in
poikelitic crystals of clinopyroxene. This sample was collected approximately 30 meters
east of the western margin of the intrusion on Mellamo Island.
UNI-121 (Oregon No. 5): Course Clot Material. This sample is a coarsely crystalline olivine
gabbro from the marginal border zone of the intrusion. It is composed of large
intergrown crystals of plagioclase and clinopyroxene with included euhedral crystals of
olivine and anhedral magnetite. These clot bands which occur at irregular intervals
within the Marginal Border Group are often partially altered to chlorite minerals. This
sample was collected approximately 50 meters from the intrusion margin on Mellamo
Island.
UNI-122 (Oregon No. 9): Lower Zone A. This sample is an olivine gabbro containing cumulate
olivine and plagioclase in a matrix of intercumulate poikelitic clinopyroxene and
accessory magnetite. This sample was collected along Uttentals Sund in the northwest
corner of the intrusion.
UNI-123 (Oregon No. 10): Lower Zone B. This sample is an olivine gabbro with cumulate
olivine, plagioclase, and clinopyroxene in a matrix of poikelitic clinopyroxene and minor
amounts of magnetite. It was collected along the northern shore of Uttentals Sund at the
site of the 1965 drilling attempt of the Skaergaard intrusion.
UNI-124 (Oregon No. 11): Lower Zone C. This sample is an olivine gabbro with cumulate
olivine, plagioclase, clinopyroxene, and magnetite with intercumulate poikelitic
clinopyroxene and abundant anhedral magnetite. This sample was collected from the
eastern edge of Kramers Island.
UNI-125 (Oregon No. 25): Middle Zone. This sample is a course-grained gabbro with cumulate
clinopyroxene, plagioclase, and magnetite. Interstitial minerals include clinopyroxene
and magnetite. Olivine is generally absent from this zone but rare crystals do exist. This
sample was collected from the southeast corner of Krammers Island.
UNI-126 (Oregon No. 23): Upper Zone A. This sample is a ferrodiorite with cumulate olivine,
plagioclase, clinopyroxene, and magnetite. The intercumulate material is primarily
poikelitic clinopyroxene and anhedral magnetite. This sample was collected .5
kilometers south of Forbindels glacier along Uttentals Sund.
Skaergaard Intrusion
9
UNI-127 (Oregon No. 21): Upper Zone B. This sample is a ferrodiorite with cumulate olivine,
plagioclase, clinopyroxene, and apatite. Intercumulate minerals include plagioclase,
clinopyroxene, and magnetite. This sample was collected from the south side of Home
Bay.
UNI-128 (Oregon No. 26): Upper Zone C. This sample is a ferrogabbro containing cumulate
olivine, plagioclase, magnetite, and apatite. The original intercumulate wollastonite has
been inverted to a patchy pyroxene during cooling. Collected along Skaergaard bay near
the foot of Basisglacier.
UNI-129 (Oregon No. 28): Sandwich Horizon. This sample is a ferrogabbro containing cumulate
crystals of olivine, plagioclase, apatite, and inverted wollastonite. This horizon also
contains dendritic magnetite and myrmekititc quartz. The sandwich horizon represents
the final product of the layered series differentiation and is believed to have formed from
residual liquids trapped between the layered series and the Upper border group. This
sample was collected from the eastern slopes of Baststoppen.
UNI-130 (Oregon No. 29): Upper Border Group. This sample is a medium grained plagioclase
rich gabbro containing cumulate plagioclase, clinopyroxene, and olivine. Alteration has
introduced quartz, chlorite, and zeolite. The rocks of the upper border group are often
altered due to their having formed above the cooling Skaergaard magma. This sample
was collected approximately ½ kilometer north of the southern margin of the intrusion
near the entrance to Skaergaard.
UNI-131 (Oregon No. 30): Melano Granophyre. This sample of granophyre contains quartz,
plagioclase, orthoclase and abundant magnetite and pyroxene. The quartz forms
myrmekitic intergrowths with orthoclase and the pyroxene occurs as long, often
dendritic, needles which give the rock a streaky appearance. Melano granophyre bodies
occur as disseminated masses in much of the lower portion of the upper border group.
This sample was collected from the south side of Basistoppen.
UNI-132 (Oregon No. 16): Tinden Sill. This sample is an acid granophyre containing
plagioclase, orthoclase and quartz crystals and areas of myrmekitic intergrowths of
quartz and orthoclase. This sill represents the most differentiated rock in the Skaergaard
complex. This sample was collected from the north side of Tinden Peak near
Brodretoppen glacier.
UNI-133 (Oregon No. 27): Transgressive Granophyre. This sample is a medium grained
granophyre with anhedral crystals of quartz and orthoclase, euhedral crystals of
plagioclase, and accessory hornblende and biotite. It comes from one of the many postSkaergaard granophyre dikes that cut through the layered series. This sample was
collected ½ kilometer south of Forbindelses glacier along Uttentals Sund.
UNI -134 (Oregon No. 2): Unaltered Gneiss. This sample is strongly foliated feldspathic gneiss
of Precambrian age. The lighter bands are composed primarily of quartz, orthoclase, and
plagioclase while the darker bands are composed of magnetite, clinopyroxene, and quartz
with only scattered feldspar crystals. This sample was collected from the western end of
Mellamo Island approximately 100 meters from the intrusion.
UNI-135 (Oregon No. 1) Contact Altered Gneiss. This sample is recrystallized feldspathic
gneiss showing a slight remnant foliation. It is composed primarily of quartz, orthoclase,
and plagioclase, and contains as accessory minerals biotite, chlorite, and magnetite. The
intrusion is in contact with Precambrian gneiss along its western and northern margins.
This sample was collected approximately 1 meter west of the contact on Mellamo Island.
Skaergaard Intrusion
10
UNI-136 (Oregon No. 6) Fused Gneiss. This sample comes from a partially melted gneiss block
included in the marginal border zone of the intrusion. The rock has a mottled appearance
caused by darker bands of Skaergaard material surrounding lighter areas of fused gneiss.
The darker bands contain crystals of olivine, plagioclase, magnetite, and clinopyroxene,
while the lighter areas are composed of cores of fused gneiss surrounded by lighter
reaction rims of euhedral quartz. The rock also contains scattered blebs of chalcopyrite.
The sample was collected from the marginal border group on Uttentals Plateau.
UNI-137 (Oregon No. 3) Dolerite Dike. This sample was collected from a fine-grained, post
Skaergaard, basaltic dike approximately .5 meters in width. Post Skaergaard dikes
ranging from a few centimeters to many meters in width are very abundant in the
southern portion of the intrusion. This sample was collected on Mellamo Island near the
western contact of the intrusion.
UNI-138 (Oregon No. 17) Contact Altered Dike. This sample represents a fine grained basalt
dike, which has been altered to a granular hornfels by its close proximity to the
Skaergaard intrusion. This sample from a pre-Skaergaard Tertiary dike was collected 3
meters south of the southern margin of the intrusion.
UNI-139 (Oregon No. 24) Altered Basalt. This sample represents a fine-grained basalt which has
been altered to a granular hornfels by the Skaergaard intrusion. It was collected on the
east side of the intrusion near Miki's Fiord.
UNI-140 (Oregon No. 22) Basistoppen Sheet. This sample is a spotted gabbro containing
plagioclase, orthopyroxene, and magnetite.
The Basistoppen sheet is a large
differentiated basic sill in the southern portion of the intrusion. The mafic minerals in
this sill are often altered giving the rock its characteristic mottled or spotted appearance.
This sample was collected from Skillenunatak along Skaergaard Bay.
UNI-141 Basalt, Tertiary plateau type, Skaergaard Bay.
Skaergaard Intrusion
11
Thin Section Descriptions
The first number refers to the UNI collection number and the following letter refers to
the reference number of Western Minerals.
UNI-118 (Western Minerals L). Chilled Margin - Close to the contact, the chilled margin rocks
have a fine-grained granular texture and commonly may not be present depending on the
amount of assimilation of silica from the wall rocks. Small fragments of gneiss
commonly occur as xenoliths or xenocrysts.
UNI-119 (Western Minerals M). Gabbro Picrite - This particular rock is closer to a feldspathic
peridotite than a gabbro but the name applied by Wager is widely accepted. Blocks of
this composition are found near the margin of the intrusion along the northern boundary
where the lowest levels of the intrusion are exposed. The olivine is the most Mg-rich in
the intrusion. Presumably the blocks were carried up to their present level from a deeper
horizon, perhaps in the feeding channel.
UNI-120 (Western Minerals N). Perpendicular Feldspar Rock - The marginal border group
contains slender plagioclase crystals that are oriented normal to the contact and give the
rock a comb or crescumulate texture. Small olivines and poikilitic pyroxene occur
between the elongated feldspar crystals.
UNI-121 (Western Minerals 0). Pegmatoidal Material - The marginal border group contains
bands and clots to coarsely crystalline rock. Although the exact mechanism for their
formation is unknown, they are believed to have formed from volatile-rich liquids. They
contain large crystals of olivine, plagioclase, pyroxene, and apatite and together with
biotite, calcite, quartz, sphene, and alteration products. The biotite is now largely altered
to chlorite.
UNI-122 (Western Minerals A). Lower Zone A - Olivine (Fo65) and labradorite form large
granular crystals surrounded by poikilitic pyroxene. Magnetite occurs as an accessory
mineral that crystallized from the trapped intercumulate liquid. Biotite has formed
between magnetite and plagioclase as a result of reaction with volatiles escaping from
the underlying gneiss.
UNI-123 (Western Minerals B). Lower Zone B - Olivine, labradorite, augite, and inverted
pigeonite are cumulus phases at this level. Poikilitic pyroxene and accessory magnetite
fill in the intercumulate areas. Note the exsolution textures of the pyroxenes.
UNI-124 (Western Minerals C). Lower Zone C - Magnetite is abundant at all levels above the
base of this zone. Note the reaction rims between magnetite and pyroxene; this is
thought to be the result of sub-solidus reduction of the magnetite and desilication of
adjacent pyroxene to produce an iron-rich olivine. Feathery intergrowths of pyroxene
and spinel formed near the edges of some of the plagioclase, possibly as a result of
locally concentrated water, which favored a shift of the plagioclase to a more albitic
composition. The plagioclase is well oriented.
UNI-125 (Western Minerals D). Middle Zone - At this level olivine ceased to crystallize as a
primary phase but is still present in small amounts due to late reactions between
magnetite and pyroxene. Plagioclase is now about An5 and the pyroxene is intermediate
between iron and magnesium end members1.
UNI-126 (Western Minerals E). Upper Zone A - Olivine (hortonalite) reappears as a cumulus
phase at the base of the upper zone and becomes increasingly iron rich upward. The
pyroxenes have a brownish color and a high refractive index because of their high iron
content.
1
This may be a typographical error in the Western Minerals’ descriptions. A composition of
An50 would be more expected.
Skaergaard Intrusion
12
UNI-127 (Western Minerals F). Upper Zone B - About 100 meters above the base of the upper
zone apatite becomes a cumulate mineral. This rock contains about 2.7% P 205. Olivine
and pyroxene are very iron rich and when oxidized exsolve magnetite along fractures.
UNI-128 (Western Minerals G). Upper Zone C - Near the top of the upper zones the pyroxenes
are almost pure hedenbergite. They crystallized initially as Fe-wollastonite but on
cooling entered the stability range of clinopyroxene. The greenish patchy pyroxenes are
typical of inverted Fe-wollastonite, while the brown optically continuous pyroxenes have
grown entirely as clinopyroxene. The olivine is essentially pure fayalite, but the
plagioclase is still only andesine. Scattered patches of granophyre have crystallized from
the trapped liquid.
UNI-129 (Western Minerals H). Sandwich Horizon - This is thought to be the last rock to
crystallize as the layered sequences of the roof and the floor converged. The olivine is
nearly pure fayalite and the pyroxene pure hedenbergite. The rock is rich in residual
components, including high concentrations of excluded trace elements. Note that the
silica mineral crystallized originally as quartz.
UNI-130 I (Western Minerals I). Upper Border Group  - The last of the rocks of the upper
border group that crystallized from the roof downward have many of the features of the
main layered series, but tend to be richer in plagioclase and to have been hydrotherrmally
altered by gases that streamed up through them. This rock which comes from just above
the sandwich horizon crystallized tridymite as the initial silica phase, but crystallized
quartz as the rock cooled. The needle-like quartz crystals are pseudomorphs of
tridymite. The tridymite - quartz transition occurred at about 980ºC at this pressure
level.
UNI-130 J (Western Minerals J). Upper Border Group  This section shows the type of
alteration typical of much of the upper border group. Chlorite, epidote, and zeolite are
the typical alteration minerals. Note the two types of granophyric intergrowths. During
early stages of crystallization the silica mineral, tridymite, forms long slender
intergrowths with feldspar, but below the transition to quartz the texture became more
myrmekitic.
UNI-130 K (Western Minerals K). Upper Border Group  - The highest levels of the upper
border group contain large laths of labradorite with a composition close to those of the
lowest exposed part of the layered series. Poikilitic pyroxene has grown between the
plagioclase laths and comprises a large portion of the rock. Graphic magnetite crystals
and rare interstitial quartz crystallized from the trapped liquid.
UNI-131 (Western Minerals P). Melanogranophyre - This rock, originally called a hedenbergite
granophyre by Wager, has a coarse graphic texture with perthitic alkali feldspars and
iron-rich pyroxene. The melanogranophyre occurs as isolated bodies within the upper
border group and is believed to represent a miscible liquid which separated from the
main Skaergaard magma at a late stage in its differentiation history.
UNI-132 (Western Minerals R). Tinden Sill - This granophyre forms a large sill intruded into
the upper part of the Skaergaard intrusion and is the most differentiated rock in the
complex. Strontium isotope studies indicate that this sill is the product of melting of the
surrounding gneiss. The granophyre consists almost entirely of alkali feldspar and
quartz.
UNI-133 (Western Minerals Q). Transgressive Granophyre - Transgressive granophyres occur
within the layered series and upper border group as dikes and sills. They are composed
primarily of quartz, orthoclase, and plagioclase, hornblende and biotite.
UNI-134 (Western Minerals T). Foliated Gneiss - This specimen of foliated feldspathic gneiss
was collected 100 meters from the intrusion contact. It consists of a mosaic of quartz
and feldspar with biotite and granular aggregates of hypersthene and magnetite. Some of
the plagioclase has clear untwinned rims surrounding a cloudy interior.
Skaergaard Intrusion
13
UNI-135 (Western Minerals S). Contact Gneiss - This sample collected less than 1 meter from
the contact is surprisingly unaltered. Although there has been some recrystallization
there is still a remnant foliation. The minerals include quartz, cloudy feldspar, biotite,
chlorite, epidote, and magnetite.
UNI-136 (Western Minerals U). Fused Gneiss – This sample comes froma partially melted lock
of gneiss included in the margin border zone of the initrusion. The darker bands contain
olivine, plagioclase, magnetite, and clinopyroxenne. The lighter bands contain a larger
proportion of plagioclase and accessory biotite and clinozoisite. The lighter areas
represent partially fused gneiss and the darker areas the Skaergaard magma. Most of the
original quartz has been consumed in reaction with the olivine gabbro.
UNI-137
(Western Minerals V).
Basaltic Dike – This rock originally contained
microphenocrysts of augite, plagioclase, and olivine in a intergranular groundmass of
plagioclse, pyroxene, magnetite, and glass. The rock has been hydrothermally altered so
that the olivine has been reduced and pseudomorphed by serpentine, and the glassy
groundmass has been devirtified.
UNI-139 (Western Minerals W). Altered Basalt – This sample represents an altered basalt that
was in contact with the Skaergaard intrusion. It contains rounded aggregates of coarse
pyroxene in a fine grained matrix of granular pyroxene and anhedral platioclase. Olivine
has broken down completely and magnetite has recrystalized to elongated blebs and
irregular clots. Secondary biotite is intimately associated with the magnetite and apatite
is an abundant accessory mineral.
UNI-140 (Western Minerals X). Basistoppen Sheet – The Basistoppen sheet is a large sill (400
meters thick) which has been intruded into the upper portion of the Skaregaard intrusion.
This sample contains orthopyroxene and clinopyroxene both of which are partialllly
altered to chlorite. Other minerals include plagioclse and graphic magnetite. Although
this sill is believed to be later than the Sikaergaard intrusion it tends to be more altered.
The alteration of the mafic minerals in this rock gives it a characteristic spotted
appearance.
Skaergaard Intrusion
14
Sample
Number
UNI-118
UNI-119
UNI-120
UNI-121
UNI-122
UNI-123
UNI-124
UNI-125
UNI-126
UNI-127
UNI-128
UNI-129
UNI-130
UNI-131
UNI-132
UNI-133
UNI-134
UNI-135
UNI-136
UNI-137
UNI-138
UNI-139
UNI-140
SiO2
TiO2
Al2O3
Fe2O3
48.67
39.57
47.23
48.2
45.48
47.93
41.05
42.16
44.44
37.06
43.46
55.1
55.3
58.81
75.03
71.56
68.17
70.37
59.58
47.61
43.17
47.89
49.17
0.56
0.37
0.4
0.4
1.31
1.3
4.83
6.07
5.28
5.55
3.0
1.16
0.94
1.26
0.31
0.44
0.63
0.65
0.89
1.58
3.75
1.74
2.2
17.37
1.61
16.7
19.18
13.8
16.31
10.2
10.21
11.22
10.41
7.41
9.9
18.52
12.02
13.71
15.63
16.13
15.37
15.1
10.92
9.26
14.36
11.23
2.19
0.44
0.65
1.33
0.49
1.36
5.63
4.8
4.18
4.05
3.06
4.75
2.18
5.77
1.56
0.76
0.58
0.47
0.52
3.8
2.23
1.63
4.19
FeO
5.75
17.77
8.6
7.4
12.94
9.65
16.06
14.89
16.54
20.41
28.07
15.14
7.47
9.38
0.58
2.14
2.09
2.52
7.31
7.25
11.68
10.14
17.28
MnO
MgO
CaO
Na2O
0.13
0.24
0.13
0.13
0.17
0.16
0.23
0.24
0.28
0.5
0.28
0.14
0.08
0.21
0.01
0.03
0.05
0.05
0.1
0.19
0.22
0.19
0.33
8.16
37.59
11.13
8.47
13.26
8.88
8.46
7.12
4.79
5.69
0.21
0.13
0.21
0.72
0.15
0.43
1.82
1.52
5.38
13.49
15.08
7.28
1.28
12.65
1.12
12.88
11.7
8.71
10.24
10.38
10.91
8.67
9.72
9.73
7.76
8.2
5.03
0.69
0.31
2.07
1.89
4.21
8.07
9.28
10.51
7.62
2.26
0.26
1.86
2.72
2.49
2.39
2.18
2.31
2.91
2.73
2.31
3.86
4.51
3.87
4.24
5.01
4.4
4.11
3.26
2.74
1.5
3.01
3.62
K2O
0.11
0.05
0.07
0.15
0.29
0.24
0.17
0.2
0.24
0.27
0.41
1
1.3
2.25
3.85
3.22
3.22
2.85
1.98
0.1
0.27
0.22
0.81
H2O+
H2O-
P2O5
TOTAL
0.96
0.95
0.35
0.27
0.75
0.74
0.58
0.54
1.83
0.41
1.35
0.92
0.41
0.21
0.28
0.3
0.4
0.39
1.17
3.62
0.8
2.76
1.47
0.2
0.02
0.07
0.17
0.06
0.14
0.28
0.07
0.11
0.18
0.2
0.19
0.14
0.19
0.13
0.05
0.16
0.15
0.13
0.58
0.1
0.1
0.11
0.02
0.03
0.04
0.05
0.14
0.09
0.05
0.02
0.14
2.67
0.86
0.24
0.42
0.71
0.03
0.07
0.31
0.29
0.2
0.17
0.1
0.18
0.78
99.48
100.07
100.1
100.17
99.85
99.35
99.79
99.75
100.59
99.58
100.33
100.3
99.61
100.43
100.03
99.9
100.03
100.63
99.83
100.12
99.59
100.01
100.19
Revised October 26, 2010
Hutton Thin Section Collection
206 – Basic xenolith, Border Group, Kraemerso, Greenland, W & D 4136, p. 201
207 – Perpendicular feldspar rock, Mallemo, Greenland, W & D 1849, p. 144
208 – Hypersthene olivine gabbro. Foot N.W. ridge gabbro Fjaeld, Greenland, W & D 1708, p.
88
209 – Olivine hypersthene gabbro. E. Greenland, W & D 1109
210 – Olivine hypersthene gabbro, Border Group, Irnarmiut, Greenland, W & D 4288, p. 154
211 – Olivine hypersthene gabbro. Mallemo, Greenland, W & D 1837, p. 157
212 – Ferrogabbro, Greenland, W & D 2574
213 – Fayalite- ferro-gabbro. W. face of Basistoppen, Greenland, W & D 4139, p. 113, 115
214 – Fayalite ferrogabbro. W. face of Basistoppen, Greenland, W & D 4143, p. 110-2
215 – Olivine rich gabbro, Greenland, W & D 1710
216 – Hybrid, Mellemo, W. Border, Greenland, W & D 1249
217 – Lower Middle gabbro, Uttentals Sound, Greenland, W & D 1691, p. 85, 95
218 – Basic xenolith, outer border group, Kramerso
219 – Hortonolite ferrogabbro, Greenland, W & D 2584, p. 196
220 – Fayalite ferrogabbro (unlayered) purple band, west face Basistoppen, Greenland, W & D
4139, p. 112, 117, & 73
221 – Hypersthene olivine gabbro, Uttentals Plateau, Greenland, W & D 4084, p. 71, 88
222 – Middle gabbro, Greenland, W & D 2122
223 – Basic xenolith in outer border group, Kramers O, W & D 345, p. 201
224 – Olivine gabbro, Udloberen, Greenland, W & D 1827, p. 164
225 – Fayalite ferrogabbro with inverted beta Wollastonite, Basistoppen, Greenland, W & D
4143, p. 110
226 – Granophyre, S.E. slope of Uttenals Plateau, Greenland, (in layered series) W & D 4074, p.
185
227 – Hedebergite andesinite, W. face of Basistoppen, 250 m above “purple band”,
Kangerdlugssang, W & D No. 4136, p. 70, 77, 85, 113-6
228 – Hybrid, centre of Mellemo, Kangerdlugssang, W & D No. 1858, p. 156
229 – Granophyre in Border Group, Brodretoppen, Greenland, W & D No. 3045, p. 205
230 – Banded gabbro, layered series, near Basishusene, Uttentals Sound, Greenland, W & D No.
2573
231 – Fayalite ferrogabbro, unlaminated layered series, W. face of Basistoppen,
Kangerdlugssang. W & D No. 4139, p. 68, 70, 73, 85, 112-7
232 – Hypersthene olivine gabbro, Kraemers O, Kangerdlugssang, W & D No. 2308, p. 97
233 – Olivine gabbro, S. margin Border Group, zoom from outer contact, foot of W. ridge of
Tinden, Kangerdlugssang, W & D No. 2775
234 – Olivine gabbro, foot of Tinden, Kangerdlugssang, W & D No. 1225, c.f., p. 209-11
235 – Granophyre, Uttentals Sound, Kangerdlugssang, W & D No. 2562, p. 206
236 – Hybrid, near Basishusene, Kangerlugssang, W & D No. 2584, p. 187
237 – Hortonolite, ferrogabbro, near Main Base House, Kangerdlugssang, W & D No. 2569, p.
119
238 – Gabbro, Skaergaard Intrusion, E. Greenland. Exact location unknown
Revised October 26, 2010
Skaergaard Intrusion
18
Kodachrome slides.
Group 1. Kodachrome slides illustrating field relations.
1. View of the basaltic lavas and dikes on the south and east sides of the intrusion. Ship
gives scale of relief.
2. View looking northeast with basalts on the right overlying Precambrian gneisses and
amphibolites on the left.
3. View from the central part of the intrusion looking west. The contact between the
Gabbro and gneiss in clearly visible on Kraemer’s Island across the fjord.
4. View looking south and up section. The entire layered series and most of the upper
border group can be seen starting with LZa in the foregound. The large glacier is near
the boundary between MZ and Uza.
5. Gneiss contact on the east side of Uttentals Sound. The light brown gabbros are LZa and
LZb and the change to darker colors mark the base of LZc where magnetite becomes
abundant.
6. Chilled margin again gneiss.
7. Inclusions of wall rocks in the marginal gabbro.
8. Closer view of block gneiss showing rim melting and reaction with the surrounding
gabbro.
9. Acicular plagioclase and pyroxene in the tranquil zone of the marginal border group.
10. Blocks of ‘gabbro picrite’ in the marginal border group on Uttentals Plateau.
11. Banded division of the marginal border group on Mellemo Island.
12. Contact between the layered series on the left and marginal border group on the right.
Note the sharp angular discordance between the steeply dipping marginal border group
and the more nearly horizontal layered series.
13. Cross bedding in LZa just above the basal contact and near the wall.
14. Same. Note the fine banding between the more prominent darker layers.
15. Typical outcrop of LZa on Uttentals Plateau.
16. Typical outcrop of LZ showing contact between LZb (light colored) and LZc (dark
colored) rocks. Man is standing just beyond the contact on LZb.
17. Zone of Abundant xenoliths in LZb. Blocks are thought to have come from the roof.
18. Strongly layered gabbro of LZb. Note folds produced by sliding of one layer over the
other.
19. View of Gabbro Peak from the north with rocks of MZ in foreground.
20. View of the west face of Wager Peak showing strong layering and large blocks,
presumably pieces of the Upper Border Group that sank from the roof.
Skaergaard Intrusion
19
21. Closer view of the same face showing layering draped over a large block. Block is the
size of a large house.
22. Upper part of MZ in same face showing the conspicuous Triple Group.
23. Block in MZ.
24. Rhythmic layering.
25. View of the upper part of the intrusion looking across Forbindels Glacier from the north.
Sandwich Horizon is just above the level of the two nunataks.
26. View of the southern part of the intrusion including UZ and the Upper Border Group.
27. Discontinuous layering in UZa. A transgressive granophyre can be seen in the upper part
of the outcrop.
28. Trough Band in UZa. Plunge of the axis of the trough can be followed to the crest of the
ridge and down to the bay in the background.
29. Closer view of layering in a trough band. Outcrop was defaced by members of an earlier
expedition. The origin of the troughs is still uncertain. The explanation offered by
Wager held that they resulted from deposition from turbidity currents flowing down the
axis of the trough, but the detailed structures do not all agree with this explanation.
30. Clots of granophyric material in UZc. In contrast with the granophyre produced by
melting of gneiss inclusions, these are thought to be segregations of a second immiscible
liquid.
31. Sandwich Horizon. Darker rocks below are UZc, lighter ones above are the lowermost
part of the Upper Border Group. The Sandwich Horizon is a patchy Zone between the
two units crystallizing from the top down and the bottom up.
32. Small body of granophyre in the Upper Border Group.
33. Larger granophyre in Upper Border Group. Note the later dikes.
Skaergaard Intrusion
20
Group 2. Kodachrome slides including maps, cross-sections, and relatives found
in the thin sections.
34. Map of Greenland. Skaergaard is located at 68N on the east coast where the
Precambrian rocks on the south meet the Eocene basalts on the north.
35. Map and cross-sections through the intrusion.
36. Hypothetical reconstruction of the original form of the intrusion.
37. Stratigraphic section of the intrusion.
38. Texture of chilled margin in this section. (See slide #6)
39. Thin section of gabbro picrite showing well-developed orthocumulate texture.
40. Thin section of gabbro from LZa showing characteristic poikilitic augite. (See LZa
outcrop 15)
41. Thin section of gabbro from LZb. Augite forms grains with about the same size and
form as the plagioclase and olivine. Wager interpreted this as evidence that augite was a
primary precipitate in LZb but an interstitial post-cumulate phase in LZa. The difference
may simply be due to differing nucleation rates, however.
42. Thin section of gabbro from LZb showing resorption of olivine, which has reacted with
the liquid to form pyroxene.
43. Exsolution texture in clinopyroxene caused by separation of Ca-poor pyroxene along
(001) planes of the host.
44. Thin section of gabbro from LZc showing abundant magnetite. (See slide #16)
45. Thin section, middle-zone gabbro. Resembles that of LZb, but lacks primary olivine.
46. Thin section of gabbro from UZa. Contains iron-rich olivine.
47. Thin section of gabbro from UZb. Contains large cumulous apatite crystals.
48. Thin section of gabbro from UZc. Patchy texture of pyroxene in the result of inversion
from Fe-wollastonite.
49. Specimen from an experimental charge showing immiscible texture between liquids with
the composition of UZc and granophyre. (See slide #31)
50. Thin section of specimen from the Sandwich Horizon. (See slide #32)
51. Graphic texture of quartz and feldspar in melanogranophyre from the Upper Border
Group.
52. Similar texture but with clinopyroxene.
53. Thin section of granophyre from the Tinden Sill.