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Geochemical Features of Some Archaean and Post-Archaean High-Magnesian-Low-Alkali Liquids

Geochemical Features of Some Archaean and Post-Archaean High-Magnesian-Low-Alkali Liquids
Geochemical Features of Some Archaean and Post-Archaean High-Magnesian-Low-Alkali Liquids
High-magnesian-low-alkali liquids are found as mafic lavas ranging in age from Archaean to Cainozoic. The most magnesian lavas are represented by Archaean spinifex textured peridotitic komatiites, and in this study these liquids are used as a comparative base for younger, less magnesian liquids. The post-Archaean lavas fall into three categories: (1) the Cape Smith (Proterozoic) - Baffin Bay (Cainozoic) group, (2) the low-Ti ophiolitic basalts of Cyprus, which represent remelting of a sequentially depleted source, and (3) the boninite group, which are the products of (wet?) melting of a source that had previously experienced depletion and addition of incompatible element enriched phases. With the use of parameters such as Al$_{2}$O$_{3}$/TiO$_{2}$, Sc/Zr, Ti/V, a comparison of Archaean komatiites with the younger high magnesian lavas indicates that the bulk of the variation seen in these rocks types can be interpreted in terms of the amount of partial melting and nature of residual phases. However, some of the variability that occurs within individual lava provinces (particularly among the light rare earth elements) is best explained by a heterogeneity superimposed on a previously homogeneous source. The abundance of high-magnesian liquids declines sharply after the Archaean as does the maximum MgO content achieved by the lavas.
0080-4614
365-381
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Sun, S.-S.
4552e90c-1144-4295-9eb9-a72bd90f07eb
Nisbet, E.G.
ae7600ce-a1c2-44bc-9231-6b83daf9da25
O'Hara, M.J.
d635f7f8-c198-4fce-ac72-d59f5d6e211a
Smith, J.V.
26fc4298-f3aa-423c-9559-60a23d938060
Nesbitt, R.W.
6a124ad1-4e6d-4407-b92f-592f7fd682e4
Sun, S.-S.
4552e90c-1144-4295-9eb9-a72bd90f07eb
Nisbet, E.G.
ae7600ce-a1c2-44bc-9231-6b83daf9da25
O'Hara, M.J.
d635f7f8-c198-4fce-ac72-d59f5d6e211a
Smith, J.V.
26fc4298-f3aa-423c-9559-60a23d938060

Nesbitt, R.W., Sun, S.-S., Nisbet, E.G., O'Hara, M.J. and Smith, J.V. (1980) Geochemical Features of Some Archaean and Post-Archaean High-Magnesian-Low-Alkali Liquids. Philosophical Transactions of The Royal Society A, 297 (1431), 365-381. (doi:10.1098/rsta.1980.0222).

Record type: Article

Abstract

High-magnesian-low-alkali liquids are found as mafic lavas ranging in age from Archaean to Cainozoic. The most magnesian lavas are represented by Archaean spinifex textured peridotitic komatiites, and in this study these liquids are used as a comparative base for younger, less magnesian liquids. The post-Archaean lavas fall into three categories: (1) the Cape Smith (Proterozoic) - Baffin Bay (Cainozoic) group, (2) the low-Ti ophiolitic basalts of Cyprus, which represent remelting of a sequentially depleted source, and (3) the boninite group, which are the products of (wet?) melting of a source that had previously experienced depletion and addition of incompatible element enriched phases. With the use of parameters such as Al$_{2}$O$_{3}$/TiO$_{2}$, Sc/Zr, Ti/V, a comparison of Archaean komatiites with the younger high magnesian lavas indicates that the bulk of the variation seen in these rocks types can be interpreted in terms of the amount of partial melting and nature of residual phases. However, some of the variability that occurs within individual lava provinces (particularly among the light rare earth elements) is best explained by a heterogeneity superimposed on a previously homogeneous source. The abundance of high-magnesian liquids declines sharply after the Archaean as does the maximum MgO content achieved by the lavas.

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Published date: July 1980
Organisations: Geochemistry

Identifiers

Local EPrints ID: 361797
URI: http://eprints.soton.ac.uk/id/eprint/361797
ISSN: 0080-4614
PURE UUID: 644ed5fb-1a84-49eb-bf6c-38ca0ac32ef0

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Date deposited: 03 Feb 2014 13:30
Last modified: 20 Oct 2017 16:35

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