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Chemical zoning of muscovite from the Ervedosa granite, northern Portugal

Published online by Cambridge University Press:  05 July 2018

M. E. P. Gomes  and
A. M. R. Neiva
M. E. P. Gomes*
Affiliation:
Department of Geology, University of Trás-os-Montes and Alto Douro, 5000 Vila Real, Portugal
A. M. R. Neiva
Affiliation:
Department of Earth Sciences, University of Coimbra, 3000 Coimbra, Portugal
*
*E-mail: [email protected]
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Abstract

The tin-bearing muscovite granite from Ervedosa contains unzoned primary muscovite. This Hercynian S-type granite was hydrothermally altered at the stanniferous quartz vein walls and contains three types of muscovite: (1) very small unzoned muscovite replacing albite; (2) small unzoned hydrothermal muscovite replacing K-feldspar and quartz; and (3) zoned subhedral muscovite.

In the zoned muscovite, the core has a composition similar to that of magmatic muscovite from the unaltered granite, while the rim has a composition similar to that of hydrothermal muscovite replacing K-feldspar and quartz in the altered granite. The rim corresponds to a late overgrowth richer in the celadonitic component than the core. Infiltrated mineralizing fluids reacted with biotite and K-feldspar of the unaltered granite. We interpret the rim of muscovite to have precipitated from these solutions.

Keywords

chemically zoned muscovitemagmatic muscovitehydrothermal muscoviteS-type granite
Type
Research Article
Information
Mineralogical Magazine , Volume 64 , Issue 2 , April 2000 , pp. 347 - 358
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2000

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