Glossary of geological terms

Below infrastructure

That part of a company’s mineral reserve that can only be accessed following certain capital expenditure which has yet to be approved.

Craton

A part of the earth’s crust that has attained stability and has been little deformed for a long period of geological time.

Diorite

A group of plutonic rocks intermediate in composition between acidic and basic.

Felsic

An igneous rock having abundant light coloured minerals.

Graben

A block of rock that lies between two faults and has moved downward to form a depression between two adjacent fault blocks.

Greenstone

A field term for any compact dark green altered or metamorphosed basic igneous rock that owes its colour to chlorite.

Horst

A block of rock that lies between two faults and has moved upward relative to the two adjacent fault blocks.

Kaapvaal Craton

The ancient protocontinental basement of South Africa.

Lacustrine

Pertaining to sediments formed in lakes.

Mafic

An igneous rock composed chiefly of dark, ferromagnesium minerals.

Ophiolite

A group of mafic and ultramafic igneous rocks derived by metamorphism, whose origin is associated with an early phase of the development of a geosyncline.

Plunge

The inclination of a fold axis or other linear feature, measured in the vertical plane.

Sub-outcrop

A rock stratum that unconformably underlies another rock stratum.

Syncline

Concave fold in stratified rock, in which strata dip down to meet in a trough.

Witwatersrand Basin

A sedimentary basin in South Africa.