Troctolite
Troctolite is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with minor pyroxene. It is an olivine-rich anorthosite, or a pyroxene-depleted relative of gabbro. However, unlike gabbro, no troctolite corresponds in composition to a partial melt of peridotite. Thus, troctolite is necessarily a cumulate of crystals that have fractionated from melt.
Troctolite is found in some layered intrusions such as in the Archean Windimurra intrusion of Western Australia, the Voisey's Bay nickel-copper-cobalt magmatic sulfide deposit of northern Labrador,[1] the Stillwater igneous complex of Montana and the Tertiary Rhum layered intrusion of the island of Rùm, Scotland.[2] Troctolite is also found in the Merensky Reef of the Bushveld Igneous Complex, South Africa and in the Lizard complex in Cornwall.[3]
References
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- ↑ http://gac.esd.mun.ca/gac_2001/seven/sub_program.asp?sess=98&form=10&abs_no=237 Geology of the Voisey's Bay Deposits abstract
- ↑ http://www.turnstone.ca/rhumal.htm Troctolite (allivalite): Isle of Rhum, northwestern Scotland
- ↑ http://www.projects.ex.ac.uk/geomincentre/06The%20Lizard.pdf The Lizard
- Blatt, Harvey and Robert J. Tracy, 1996, Petrology: Igneous, Sedimentary and Metamorphic, 2nd ed., p. 72, Freeman, ISBN 0-7167-2438-3