Porphyroblastic Metasediments

Title

Porphyroblastic Metasediments

Alternative Title

Hybrid rock

Identifier

KBR-13

Description

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 12 and KBR 14 to note this range. This sample has an aphanitic- porphyritic texture and is holocrystalline. There is a light gray anhedral ground mass and medium-grained phenocrysts (1 mm- 3 mm).There are fine, snaky veins of reddish material on the fresh surface. Minor euhedral phenocrysts of plagioclase with reaction rims (4 mm).
The thin sections shown in plain polarized light and cross polarized light at 40x magnification.
The rock is 40% plagioclase, 20% pyroxenes (Enstatite), and 20% opaques.

Date

No date given.

Contributor

Western Minerals, Inc.

Is Part Of

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

Spatial Coverage

Karoo- Birds River, Eastern Cape, South Africa

Temporal Coverage

183-179 Ma (Jurassic)

Accrual Method

Purchased from Western Minerals, Inc.

Unit

Lesotho Formation

Number of Thin Sections

1

Geolocation