Rb-Sr isotopic studies of a polymetamorphic granulite terrane,Strangways Range,central Australia |
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Authors: | SS Iyer PJ Woodford AF Wilson |
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Institution: | Department of Geology and Mineralogy, University of Queensland, St. Lucia, Queensland, Australia 4067 |
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Abstract: | Rb-Sr isotopic investigation of forty rocks from three different granulite localities in the Strangways Ranges, central Australia indicated two distinct granulite metamorphisms, namely M1: 1860±80 m.y., and M2: 1470±60 m.y. and 1430±60 m.y., λ=1.39x10?11yr?1. M2 has been recorded in the felsic granulites of two of the three localities. Although the Sr isotopic systems in the felsic granulites seem to show a normal growth in a closed system during M2, the Rb-Sr systems for some calcareous and mafic granulites have not completely re-equilibrated during M2, as shown by the scatter with respect to the reference isochrons for M1 and M2. Ca-carbonate rocks display unusually low level of Sr (20–120 ppm. Sr, and high Ca/Sr ratios). Schistose zones of retrogression in the granulites, dated by K-Ar and 40Ar-39Ar methods at ≈350 m.y., yield anomalous Rb-Sr data. |
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