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Komatiites: An early precambrian phenomenon

Komatiites: An early precambrian phenomenon
Komatiites: An early precambrian phenomenon
Using the presently accepted definition, komatiites are ultramafic volcanic rocks characterised by bladed and/or skeletal olivine texture (spinifex texture). Where textural evidence is absent,the geochemical definition is equivocal and as a result there is considerable ambiguity, particularly among the basaltic types. If the added control of Al2O3/TiO2 ? 25 is added to the definition, this eliminates rocks of the boninite group and also the low-Ti basalts found in some ophiolite complexes. The bulk of komatiites occur in the Archaean and the most obvious explanation is that the eruption of high (up to 30%) MgO melts was controlled by an enhanced geothermal gradient. There is some evidence to suggest that the high CaO/Al2O3 ratio characteristic of some komatiites (e.g. Barberton) is found only in those greenstone belts older than 3.0 b.y.
0377-0273
31-45
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Jahn, Bor-Ming
9f65e666-cea8-45f2-b3f6-c8f7c5c0367a
Purvis, A.C.
99993f02-a163-45e4-a86c-e66e25fccf34
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Jahn, Bor-Ming
9f65e666-cea8-45f2-b3f6-c8f7c5c0367a
Purvis, A.C.
99993f02-a163-45e4-a86c-e66e25fccf34

Nesbitt, R.W., Jahn, Bor-Ming and Purvis, A.C. (1982) Komatiites: An early precambrian phenomenon. Journal of Volcanology and Geothermal Research, 14 (1-2), 31-45. (doi:10.1016/0377-0273(82)90041-5).

Record type: Article

Abstract

Using the presently accepted definition, komatiites are ultramafic volcanic rocks characterised by bladed and/or skeletal olivine texture (spinifex texture). Where textural evidence is absent,the geochemical definition is equivocal and as a result there is considerable ambiguity, particularly among the basaltic types. If the added control of Al2O3/TiO2 ? 25 is added to the definition, this eliminates rocks of the boninite group and also the low-Ti basalts found in some ophiolite complexes. The bulk of komatiites occur in the Archaean and the most obvious explanation is that the eruption of high (up to 30%) MgO melts was controlled by an enhanced geothermal gradient. There is some evidence to suggest that the high CaO/Al2O3 ratio characteristic of some komatiites (e.g. Barberton) is found only in those greenstone belts older than 3.0 b.y.

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Published date: October 1982
Organisations: Geochemistry

Identifiers

Local EPrints ID: 361794
URI: https://eprints.soton.ac.uk/id/eprint/361794
ISSN: 0377-0273
PURE UUID: bc0b5559-2161-49e4-bbb2-f20e4a6a16ab

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Date deposited: 03 Feb 2014 13:14
Last modified: 18 Jul 2017 02:58

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