Porphyroblastic Metasediments

Porphyroblastic Metasediments

Hybrid rock

KBR-12

The porphyroblastic metasediments/hybrid rocks were interpreted by Eales and his co-workers to be metamorphosed "Red Beds" Formation sediments but could be magmatic in origin. The samples illustrate the range in textures; see KBR 13 and KBR 14 to note this range. This sample has an aphanitic porphyritic texture. There are unfoliated coarse-grained metasediments (2 mm- 4 mm) and subhedral muscovite phenocrysts (2 mm - 3 mm) as well as red anhedral phenocrysts. There is a rusty-looking weathered surface. In thin section, radiating pyroxenes are clearly visible.
Thin sections are shown in plain polarized light and cross polarized light at 40x magnification.
The rock is comprised of 70% plagioclase, 22% pyroxene (mainly augite), and 8% 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

1