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Direct oxygen measurements of Cr-rich spinel: Implications for spinel stoichiometry


Kamperman, M and Danyushevsky, LV and Taylor, WR and Jablonski, W, Direct oxygen measurements of Cr-rich spinel: Implications for spinel stoichiometry, American Mineralogist, 81, (9-10) pp. 1186-1194. ISSN 0003-004X (1996) [Refereed Article]

DOI: doi:10.2138/am-1996-9-1017


The availability of a synthetic multilayer crystal and accurately calibrated oxide and silicate standards make it possible to use the electron microprobe for precise O analysis of spinel. A requirement of the O measurement routine described is the use of repetitive statistical analyses of the O standards and subsequent corrections and recalibration. A representative set of O analyses for each spinel population studied is essential to obtain reliable data, and the danger of using single datum is emphasized. Magnesiochromite spinel grains, having broad compositional similarities but different petrogenetic and cooling histories, were analyzed for O and their stoichiometry was assessed. Diamond-indicator spinel from the Aries kimberlite and Argyle lamproite is stoichiometric. Spinel inclusions in olivine phenocrysts from Ti-poor tholeiitc from the Hunter Fraction Zone and Ca-rich boninite from the Tonga Trench show a range of nonstoichiometry. High Fe2+/ Fe3+ values calculated assuming stoichiometry for such spinel are invalid. Spinel samples from metamorphosed volcanics from the Peak Hill-Glengarry Basin and the Heazlewood River Ultramafic Complex are also nonstoichiometric. having significant Fe83O4-Cr83O4 components. Our results demonstrate that nonstoichiometry is a common feature of Cr-rich spinel. This has important implications for the use of Fe3+ and Fe2+ concentrations to estimate the oxidation state or temperature of formation.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Mineralogy and crystallography
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Danyushevsky, LV (Professor Leonid Danyushevsky)
UTAS Author:Jablonski, W (Mr Jablonski)
ID Code:8189
Year Published:1996
Web of Science® Times Cited:12
Deposited By:Earth Sciences
Deposited On:1996-08-01
Last Modified:2011-08-19

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