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.
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