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.
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
October 1982
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), .
(doi:10.1016/0377-0273(82)90041-5).
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.
This record has no associated files available for download.
More information
Published date: October 1982
Organisations:
Geochemistry
Identifiers
Local EPrints ID: 361794
URI: http://eprints.soton.ac.uk/id/eprint/361794
ISSN: 0377-0273
PURE UUID: bc0b5559-2161-49e4-bbb2-f20e4a6a16ab
Catalogue record
Date deposited: 03 Feb 2014 13:14
Last modified: 14 Mar 2024 15:56
Export record
Altmetrics
Contributors
Author:
R.W. Nesbitt
Author:
Bor-Ming Jahn
Author:
A.C. Purvis
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics