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Trace-element compositions of sapphire and ruby from the eastern Australian gemstone belt

Jacqueline Wong, Charles Verdel and Charlotte M. Allen
Trace-element compositions of sapphire and ruby from the eastern Australian gemstone belt
Mineralogical Magazine (December 2017) 81 (6): 1551-1576


Significant uncertainty surrounds the processes involved in the formation of basalt-hosted corundum, particularly the role that the mantle plays in corundum generation. Some previous studies have suggested that trace-element ratios (namely, Cr/Ga and Ga/Mg) are useful for distinguishing two types of corundum: 'magmatic' and 'metamorphic', designations that include mantle and crustal processes. However, recent studies, including this one, have discovered transitional groups between these end-members that are difficult to classify. We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to measure trace-element concentrations in sapphire and ruby crystals from eight alluvial deposits that span a significant length of the eastern Australian gemstone belt. Additionally, we collected LA-ICP-MS U-Pb and trace-element data from zircon megacrysts at Weldborough, Tasmania, which is also within the gemstone belt. Our sapphire and ruby results reveal a continuum in trace-element compositions, an observation that raises questions regarding previous classifications that ascribe corundum from basalt-hosted gemfields to either 'magmatic' or 'metamorphic' sources. The spatial association of basalt-related gemfields in eastern Australia with a long-lived convergent margin suggests a link between corundum formation and Al-enrichment of the mantle wedge during periods of subduction.

ISSN: 0026-461X
EISSN: 1471-8022
Serial Title: Mineralogical Magazine
Serial Volume: 81
Serial Issue: 6
Title: Trace-element compositions of sapphire and ruby from the eastern Australian gemstone belt
Affiliation: University of Queensland, School of Earth and Environmental Sciences, St. Lucia, Queensl., Australia
Pages: 1551-1576
Published: 201712
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 92
Accession Number: 2018-033578
Categories: General mineralogy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables, sketch map
S37°30'00" - S28°15'00", E141°00'00" - E153°30'00"
S29°00'00" - S10°00'00", E138°00'00" - E153°00'00"
S43°40'00" - S39°30'00", E143°49'60" - E148°30'00"
S39°00'00" - S34°00'00", E140°00'00" - E150°00'00"
Secondary Affiliation: Queensland University of Technology, AUS, Australia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201808
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