Intersertal Ferrothoeleiite

Intersertal Ferrothoeleiite

Ferrotholeiite

KBR-7

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-8 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. Between the location this sample was collected and KBR-6 was collected, there is a thin gabbro pegmatite which was not collected. 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 ( 2mm - 5 mm). There is a calcic residue on heavily oxidized weathered surface. A subophitic micro-texture is also present. Spherulitic pyroxenes are clearly visible in cross polarized light.
Thin sections are shown in plain and cross polarized light at 40x magnification.
The rock is composed of 40% plagioclase, 40% pyroxene (mainly augite), 10% biotite, 5% olivine, and 5% 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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