Dolerite

Title

Dolerite

Alternative Title

Diabase or Microgabbro

Identifier

KBR-18

Description

This is dolerite from the "Dragon's Back" dyke, from the farm Romance. It is the youngest dolerite body in the area and contains biotite and hornblende. Emplacement of this dolerite took place at a much deeper crustal level than the gabbros. It has an aphanitic- porphyritic texture and is holocrystalline. The groundmass is light gray and subhedral. It contains slightly darker gray fine grained subhedral phenocrysts that comprise 30% of the dolerite. There is pinkish- brown blotchy weathering.
The thin sections are shown in plain polarized light and cross polarized light at a magnification of 400x and contains 60% plagioclase, 35% pyroxenes, and 5% 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.

Abstract

Differentiation of tholeiitic Karroo magma at Birds River, South Africa

Unit

Lesotho Formation

Number of Thin Sections

1

Geolocation