Deposit types/Platinum, Chromium, Nickel

Layered intrusion PGM and chromite (Bushveld type)

Platinum-group metals in sulphide layers and chromitite layers in big layered mafic and ultramafic intrusions.

What it is

Platinum-group metals in sulphide layers and chromitite layers in big layered mafic and ultramafic intrusions.1

How it forms

Repeated layers of crystals settled in a large magma chamber. The PGM-rich sulphide sits near the first reappearance of olivine after thick plagioclase-pyroxene rocks, and chromite forms layers lower down.1

Host rocks

Norite, gabbro, anorthosite, pyroxenite, dunite and harzburgite.1

Where it forms

Cratons, mostly in Precambrian shields.1

How old

Generally Precambrian; may be as young as Tertiary1

How geologists look for it

The ore zone is hard to see on weathered surfaces, so exploration needs extensive sampling and chemical analysis.1

Mines of this type

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Mines

An example ofImpala RustenburgSee Impala Rustenburg, an example of this deposit type.1An example ofMogalakwenaSee Mogalakwena, an example of this deposit type.1An example ofNkomatiSee Nkomati, an example of this deposit type.1

Sources

  1. Mineral Deposit Models (Bulletin 1693, Cox and Singer, eds., 1986) US Geological Survey

From the Prospector Trails mining history dataset: each fact links to the source it was checked against. Figures are as the source gives them, in the money of their day. Not investment advice.

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