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GEOREF RECORD

Hydrothermal formation of heavy rare earth element (HREE)-xenotime deposits at 100 degrees C in a sedimentary basin

Lisa Richter, Larryn W. Diamond, Petya Atanasova, David A. Banks and Jens Gutzmer
Hydrothermal formation of heavy rare earth element (HREE)-xenotime deposits at 100 degrees C in a sedimentary basin
Geology (Boulder) (March 2018) 46 (3): 263-266

Abstract

Most rare earth element deposits form from magmatic fluids, but there have also been discoveries of heavy rare earth element (HREE)-enriched hydrothermal xenotime deposits within sedimentary basins. As xenotime is notoriously insoluble, the question arises as to whether these lesser-known deposits form at typical basin temperatures or by influx of much hotter magmatic-hydrothermal fluids. The Browns Range District in northern Western Australia hosts deposits of xenotime that are enriched in HREEs and also uranium. The ore bodies consist of fault-controlled hydrothermal quartz-xenotime breccias that crosscut Archean basement rocks and overlying Paleoproterozoic sandstones. Analyses of fluid inclusions show that the xenotime precipitated at remarkably low temperatures, between 100 and 120 degrees C, in response to decompression boiling. The inclusions contain high excess concentrations of yttrium (10 (super -3) mol/kg), REEs (1-7 X 10 (super -5) mol/kg), and uranium (4 X 10 (super -5) mol/kg) in equilibrium with xenotime at these low temperatures, showing that availability of phosphate limited the amount of xenotime precipitated. The analyses further identify SO (sub 4) (super 2-) and Cl (super -) as the ligands that facilitated the elevated REE and uranium solubilities. These findings establish that significant REE transport and deposition is feasible at basin temperatures, and hence they raise the potential of unconformity settings for REE exploration. Moreover, the aqueous metal contents support a genetic link between this type of ore fluid and world-class Proterozoic unconformity-related uranium deposits elsewhere.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 46
Serial Issue: 3
Title: Hydrothermal formation of heavy rare earth element (HREE)-xenotime deposits at 100 degrees C in a sedimentary basin
Affiliation: Technical University Bergakademie Freiberg, Department of Mineralogy, Freiberg, Germany
Pages: 263-266
Published: 201803
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 10
Accession Number: 2018-041991
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2018074
Illustration Description: illus. incl. geol. sketch map
S20°00'00" - S18°00'00", E127°00'00" - E130°00'00"
Secondary Affiliation: University of Bern, CHE, SwitzerlandHemholtz Zentrum Dresden-Rossendorf, DEU, GermanyUniversity of Leeds, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201810
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