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Causes for large-scale metal zonation around mineralized plutons; fluid inclusion LA-ICP-MS evidence from the Mole Granite, Australia

Andreas Audetat, Detlef Guenther and Christoph A. Heinrich
Causes for large-scale metal zonation around mineralized plutons; fluid inclusion LA-ICP-MS evidence from the Mole Granite, Australia
Economic Geology and the Bulletin of the Society of Economic Geologists (December 2000) 95 (8): 1563-1581

Abstract

Detailed reconstruction of the fluid evolution in several ore deposits associated with the Sn-, W-, and base metal-mineralized Mole granite shows that multiple factors contributed to the zonal metal distribution around this intrusion. Information about the mechanism of ore formation was obtained from field relationships, detailed petrographic studies and laser ablation-ICP-MS microanalysis of single fluid inclusions. Pre-mineralization fluid inclusions in Sn deposits are characterized by high Sn/W ratios, whereas early fluid inclusions from W deposits contain higher W concentrations and comparatively low Sn/W ratios. This indicates that the metal ratio in these deposits was predefined by the composition of the magmatic input fluid. However, in both types of deposits the input fluid actually contained much higher concentrations of base metals (Pb, Zn, Cu, etc.) than Sn and W, demonstrating that metal precipitation was highly selective. The metal zonation around the Mole granite, therefore, reflects both a compositional variation of the source fluid, as well as sequential metal precipitation from it. An additional process contributing to metal fractionation occurred by phase separation of the hydrothermal fluid into saline brine and low-density vapour, whereby Cu, B, Li, As (+ or - S, Ag, La) preferentially partitioned into the vapour phase. Analyses on six assemblages of unambiguously coexisting vapour and brine inclusions allowed direct determination of vapour/brine distribution coefficients for 24 elements.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 95
Serial Issue: 8
Title: Causes for large-scale metal zonation around mineralized plutons; fluid inclusion LA-ICP-MS evidence from the Mole Granite, Australia
Affiliation: ETH Zentrum, Department of Earth Sciences, Zurich, Switzerland
Pages: 1563-1581
Published: 200012
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 53
Accession Number: 2001-007869
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
S29°19'00" - S29°19'00", E151°41'60" - E151°41'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
Update Code: 200103
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