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Zoned Cr, Fe-spinel from the La Perouse layered gabbro, Fairweather Range, Alaska

G.K. Czamanske·G. R. Himmelberg·F.E. Goff
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Abstract

Zoned spinel of unusual composition and morphology has been found in massive pyrrhotite-chalcopyrite-pent-landite ore from the La Perouse layered gabbro intrusion in the Fairweather Range, southeastern Alaska. The spinel grains show continuous zoning from cores with up to 53 wt.% Cr 2 O 3 to rims with less than 11 wt.% Cr 2 O 3 . Their composition is exceptional because they contain less than 0.32 wt.% MgO and less than 0.10 wt.% Al 2 O 3 and TiO 2 . Also notable are the concentrations of MnO and V 2 O 3 , which reach 4.73 and 4.50 wt.%, respectively, in the cores. The spinel is thought to have crystallized at low oxygen fugacity and at temperatures above 900°C, directly from a sulfide melt that separated by immiscibility from the gabbroic parental magma.

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G.K. Czamanske, G. R. Himmelberg, F.E. Goff. 1976. Zoned Cr, Fe-spinel from the La Perouse layered gabbro, Fairweather Range, Alaska. https://doi.org/10.1016/0012-821x(76)90163-1

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