Intersertal Ferrothoeleiite

Intersertal Ferrothoeleiite

Ferrotholeiite

KBR-8

The intersertal ferrotholeiite samples are highly fractionated and were most likely emplaced before the gabbro of the formation. They have textures associated with rapidly frozen or highly viscous melts. KBR-7 and KBR-9 through KBR-11 are also intersertal ferrotholeiites. Intersertal is a texture marked by the occurrence of interstitial glass between laths of feldspar, usually in basalts. It has an aphanitic- porphyritic texture and holocrystalline. It has a consistent dark gray color with fine veins of quartz <1 mm wide. There are medium grained subhedral plagioclase phenocrysts (2 mm - 5 mm). There is a calcic residue on a heavily oxidized weathered surface. Radiating pyroxene crystals are clearly visible in plain polarized light.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is comprised of 55% plagioclase, 15% pyroxene, 12% biotite, 10% opaques, and 8% olivine.

No date given.

Western Minerals, Inc.

http://www.geosciencecollections.milne-library.org/collections/show/17

Karoo- Birds River, Eastern Cape, South Africa

183-179 Ma (Jurassic)

Purchased from Western Minerals, Inc.

Lesotho Formation

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