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Evidence of a water-rich silica gel state during the formation of a simple pegmatite

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Thomas, R and Davidson, P (2012) Evidence of a water-rich silica gel state during the formation of a simple pegmatite. Mineralogical Magazine, 76 (7). pp. 2785-2801. ISSN 0026-461X

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Abstract

This study reports the discovery of inclusions, which are inferred to represent trapped primary silicate
gels, in simple pegmatites genetically connected to the Precambrian Rønne granite of Bornholm Island,
Denmark. These inclusions are randomly associated with more typical melt and alkali-carbonate-rich
and bicarbonate-rich fluid inclusions. Their relationship to the latter and to the formation of the
pegmatite bodies is discussed. The silicate gel inclusions become increasingly common towards the
quartz cores of the pegmatites, and are considered to demonstrate increasing water and alkali carbonate
concentrations in the pegmatite-forming liquid, and an accompanying tendency for sol/gel formation.
This discovery may have important implications for the formation of the quartz cores of pegmatites.
The possible origin of the alkali-carbonate concentrations in pegmatite-forming fluids is also briefly
discussed.

Item Type: Article
Keywords: Precambrian pegmatites, nahcolite-rich inclusions, silica gel inclusions, origin of alkali carbonate melts, quartz core formation
Journal or Publication Title: Mineralogical Magazine
Page Range: pp. 2785-2801
ISSN: 0026-461X
Identification Number - DOI: 10.1180/minmag.2012.076.7.11
Additional Information:

Copyright 2012 The Mineralogical Society

Date Deposited: 07 Oct 2013 03:05
Last Modified: 31 Jan 2015 16:00
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