The Slides

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Slide 1

Possible flame-structure developed between olivine-rich and plagioclase-rich layers in mafic cumulates. Lens cap 6cm.

Slide 2

Weakly foliated harzburgite tectonite. Alternating bands of relatively orthopyroxene-rich and orthopyroxene-poor are seen. The orthopyroxene forms larger grains which weather to a distrinctive 'bronze' colour. The olivine is finer grained and weathered orange-red. A later vein of olivine gabbro cuts the harzburgite. Lens cap 6cm.

Slide 3

The top of the ridge comprises comprises 100% parallel-sided dolerite dykes. The lighter weathering slopes at the base of the ridge consists of about 15% dolerite dykes in gabbro and diorite.

Slide 4

Orange-brown weathering harzburgite makes up left of picture. These are overlain by lighter weathering, NW dipping, layered olivine gabbros. See Slide 10.

Slide 5

Transgressive layering structure in olivine gabbros. A thin anorthositic layer transgressively overlies rhythmically layered olivine gabbros. The olivine-rich base of the overlying rhythmic layer can be seen.

Slide 6

Intensely mylonitised dunites (lighter weathering colour) and harzburgites.

Slide 7

Channel-fill structure (25cm deep) in rhythmically-layered olivine gabbros.

Slide 8

Detail of 'bolster' form of pillow lava. Hammer shaft lies parallel to long-axis of tubes. See Slide 18.

Slide 9

About 60% of the outcrop comprises parallel-sided (but locally cross-cutting) dolerite dykes hosted by white weathering trondjemite.

Slide 10

The mountains are comprised of olivine gabbros. Harzburgites occur the wadi bed. See Slide 4.

Slide 11

The entire outcrop is made up of dolerite dykes intruding other dolerite dykes.

Slide 12

Adcumulate texture in anorthosite. Field of view 2cm. Note well developed lamination in plagioclase.

Slide 13

Partially assimilated (note crenulate margins) xenoliths of hydrothermally altered dolerite hosted by trondhjemite. Lens cap 6cm.

Slide 14

Pegmatitic dykes of websterite and gabbronorite cutting harzburgite. The gabbronorite post-dates the websterite. Lens cap 6cm.

Slide 15

Weak ratio layering in foliated pyroxene gabbro. The igneous fabric has been overprinted by 'spots' of actinolitic amphibole - a result of hydrothermal alteration.

Slide 16

Strongly foliated plagioclase lherzolite. Clots of plagioclase and clinopyroxene are strung out in matrix of olivine and orthopyroxene. Lens cap 6cm.

Slide 17

Varitextured gabbro showing leucocratic patches. The more mafic host has suffered extensive hydrothermal retrogression with much of the clinopyroxene being replaced by an actinolitic amphibole.

Slide 18

The wadi cliff is made entirely of variably hydrothermally altered basaltic pillow lavas. See Slide 8.

Slide 19

Lencocratic varitextured gabbro. Well developed needles of magmatic hornblende are seen.

Slide 20

Dunite pod in harzburgite. Anastomising form is typical when undeformed.

Slide 21

Partially resorbed dolerite xenoliths cut by later dolerite dykes. The host rock is varitextured gabbro.

Slide 22

Pod of pegmatitic olivine gabbro in harzburgite. Note diffuse margins. Lens cap 6cm.

Slide 23

Hydrothermally altered (greenschist facies) dolerite dykes.

Slide 24

Pillow lava intruded by dolerite dykes

Slide 25

Modally-graded cumulate peridotite. Stratigraphically, up is to the right. Dunite layers (red-brown) grade with increasing mode of clinopyroxene into wehrlite (dark-green). Lens cap 6cm.

Slide 26

Rhythmic layering in olivine gabbros. Olivine- and clinopyroxene-rich bases pass upwards into plagioclase-rich tops. The transition is not gradual however; internal ratio layering is also developed. A dyke of olivine gabbro intrudes a minor reverse fault.

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