Reaction mechanism for the replacement of calcite by dolomite and siderite: implications for geochemistry, microstructure and porosity evolution during hydrothermal mineralisation

Carbonate reactions are common in mineral deposits due to CO 2 -rich mineralising fluids. This study presents the first in-depth, integrated analysis of microstructure and microchemistry of fluid-mediated carbonate reaction textures at hydrothermal conditions. In doing so, we describe the mechanisms...

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Bibliographic Details
Published in:Contributions to mineralogy and petrology 2013-10, Vol.166 (4), p.995-1009
Main Authors: Pearce, Mark A., Timms, Nicholas E., Hough, Robert M., Cleverley, James S.
Format: Article
Language:English
Subjects:
Earth and Environmental Science
Earth Sciences
Geochemistry
Geology
Microstructure
Mineral Resources
Mineralogy
Original Paper
Petrology
Porosity
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Summary:Carbonate reactions are common in mineral deposits due to CO 2 -rich mineralising fluids. This study presents the first in-depth, integrated analysis of microstructure and microchemistry of fluid-mediated carbonate reaction textures at hydrothermal conditions. In doing so, we describe the mechanisms by which carbonate phases replace one another, and the implications for the evolution of geochemistry, rock microstructures and porosity. The sample from the 1.95 Moz Junction gold deposit, Western Australia, contains calcite derived from carbonation of a metamorphic amphibole—plagioclase assemblage that has further altered to siderite and dolomite. The calcite is porous and contains iron-rich calcite blebs interpreted to have resulted from fluid-mediated replacement of compositionally heterogeneous amphiboles. The siderite is polycrystalline but nucleates topotactically on the calcite. As a result, the boundaries between adjacent grains are low-angle boundaries (
ISSN:0010-7999
1432-0967
DOI:10.1007/s00410-013-0905-2