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Chemical variation in tourmalines from South-west England

Published online by Cambridge University Press:  14 March 2018

G. M. Power
G. M. Power*
Affiliation:
Department of Geology, University College of Wales, Aberystwyth
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Summary

Forty-eight samples of tourmaline from the granitic rocks of south-west England have been analysed by emission spectrography for Fe, Mn, Mg, Ca, Ti, Na, F, Li, Sc, V, Cr, Co, Ni, Cu, Ga, Rb, Sr, Zr, Sn, and Sc. The tourmaline reflects the fractionation trends of the rocks from which it comes in the proportion of Mg, Ca, Ti, and certain trace elements it contains and is considered likely to have been a primary product of the magma. Textural evidence that indicates a later development is interpreted as recrystallization, possibly at low temperature, with little change in chemical composition. Hydrothermal tourmaline has a distinctive chemical composition, being higher in Mg, Ca, Sr, and Sn and lower in Fe, Mn, and F and also tending to have a higher Cr, V, Ni, and Sc content. The chemical composition of the tourmalines is used to show that some quartz-tourmaline rocks are the product of extreme fractionation and are not completely tourmalinized granites. Parti-coloured tourmaline is shown to be the result of hydrothermal growth.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 36 , Issue 284 , December 1968 , pp. 1078 - 1089
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1968

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