Intersertal Ferrothoeleiite

Intersertal Ferrothoeleiite

Ferrotholeiite

KBR-10

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 through KBR-9 and 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 is holocrystalline. It has a consistent dark gray color with fine veins of quartz < 1mm wide. There are medium grained subhedral plagioclase phenocrysts (2 mm - 5 mm). There is a calcic residue on a heavily oxidized weathered surface. There is also a subophitic micro-texture. Poikolitic pyroxenes are visible in plain polarized light.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is comprised of 70% plagioclase, 30% pyroxenes (mainly augite), and <2% opaques.

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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