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GEOREF RECORD

An unusual ruby-sapphire-sapphirine-spinel assemblage from the Tertiary Barrington volcanic province, New South Wales, Australia

F. Lin Sutherland and Robert R. Coenraads
An unusual ruby-sapphire-sapphirine-spinel assemblage from the Tertiary Barrington volcanic province, New South Wales, Australia
Mineralogical Magazine (August 1996) 60 (4): 623-638

Abstract

Small, corroded, crystalline aggregates of ruby-sapphire-sapphirine-spinel occur in corundum-bearing alluvial deposits derived from the Barrington shield volcano. The sapphirine has a near 7:9:3 (MgO:Al (sub 2) O (sub 3) :SiO (sub 2) ) composition and, together with the corundum, shows reaction rims of pleonaste. Spinel in these aggregates has a composition Sp (sub 68-73) Hc (sub 27-29) Cm (sub 0.3) . Potential origins for these aggregates include metamorphic recrystallization of aluminous material (< 1460 degrees C) or high-T-high-P crystallization reactions related to lamprophyric or basaltic magmas (< or = 1300 degrees C and 20 kbar). Sapphirine-spinel thermometry suggests final crystallization for the aggregates at approximately 780-940 degrees C and reaction with the host magmas at > 1000 degrees C. The Barrington gemfield includes two distinct corundum sites. One, typical in E Australia, is dominated by blue-green, well-crystallized, growth-zoned sapphire, commonly containing rutile silk and Fe-rich spinel inclusions. The other, an unusual suite, is dominated by ruby- and pastel-coloured sapphires; these have little crystal shape or growth zonation, and restricted mineral inclusions of chromian pleonaste and pleonaste. Chemical analyses are given for sapphirine and a range of spinels. It is tentatively suggested that sapphirine may be of use as an alluvial indicator mineral for ruby.


ISSN: 0026-461X
Serial Title: Mineralogical Magazine
Serial Volume: 60
Serial Issue: 4
Title: An unusual ruby-sapphire-sapphirine-spinel assemblage from the Tertiary Barrington volcanic province, New South Wales, Australia
Affiliation: Australian Museum, Mineralogy and Petrology Section, Sydney, NSW, Australia
Pages: 623-638
Published: 199608
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 53
Accession Number: 1996-073284
Categories: General mineralogy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
S32°00'00" - S32°00'00", E151°30'00" - E151°30'00"
Secondary Affiliation: Gemmological Association of Australia (N.S.W. Division), AUS, Australia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199622
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