Library Open Repository

Extreme alkali bicarbonate- and carbonate-rich fluid inclusions in granite pegmatite from the Precambrian Rønne granite, Bornholm Island, Denmark

Downloads

Downloads per month over past year

Thomas, R and Davidson, P and Schmidt, C (2011) Extreme alkali bicarbonate- and carbonate-rich fluid inclusions in granite pegmatite from the Precambrian Rønne granite, Bornholm Island, Denmark. Contributions to Mineralogy and Petrology, 161 (2). pp. 315-329. ISSN 0010-7999

[img] PDF
Thomas-Davidson-Schmidt-2010.pdf | Request a copy
Full text restricted
Available under University of Tasmania Standard License.

Abstract

Our study of fluid and melt inclusions in quartz and feldspar from granite pegmatite from the Precambrian Rønne granite, Bornholm Island, Denmark revealed extremely alkali bicarbonate- and carbonate-rich inclusions. The solid phases (daughter crystals) are mainly nahcolite [NaHCO3], zabuyelite [Li2CO3], and in rare cases potash [K2CO3] in addition to the volatile phases CO2 and aqueous carbonate/bicarbonate solution. Rare melt inclusions contain nahcolite, dawsonite [NaAl(CO3)(OH)2], and muscovite. In addition to fluid and melt inclusions there are primary CO2-rich vapor inclusions, which mostly contain small nahcolite crystals. The identification of potash as a naturally occurring mineral would appear to be the first recorded instance. From the appearance of high concentrations of these carbonates and bicarbonates we suggest that the mineral-forming media were water and alkali carbonate-rich silicate melts or highly-concentrated fluids. The coexistence of silicate melt inclusions with carbonate-rich fluid and nahcolite-rich vapor-inclusions indicates a melt-melt-vapor equilibrium during the crystallization of the pegmatite. These results are supported by results of hydrothermal diamond-anvil cell experiments in the pseudoternary system H2O - NaHCO3 - SiO2. Additionally, we show that boundary layer effects were insignificant in the Bornholm pegmatites, and are not required for the origin of primary textures in compositionally simple pegmatites at least.

Item Type: Article
Keywords: pegmatites, fluid and melt inclusions, molten carbonates, carbon dioxide, HDAC experiments
Journal or Publication Title: Contributions to Mineralogy and Petrology
Page Range: pp. 315-329
ISSN: 0010-7999
Identification Number - DOI: 10.1007/s00410-010-0533-z
Additional Information: The original publication is available at www.springerlink.com
Date Deposited: 09 Dec 2010 01:30
Last Modified: 18 Nov 2014 04:13
URI: http://eprints.utas.edu.au/id/eprint/10276
Item Statistics: View statistics for this item

Repository Staff Only (login required)

Item Control Page Item Control Page