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The geochemistry of central Australian granulites in relation to the chemical and isotopic effects of granulite facies metamorphism

✍ Scribed by C. M. Gray

Book ID
104746727
Publisher
Springer
Year
1977
Tongue
English
Weight
883 KB
Volume
65
Category
Article
ISSN
0010-7999

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✦ Synopsis

Metamorphism to intermediate-pressure granulite grade had a minimal effect on the geochemistry of layered gneisses in central Australia. The overall composition of the terrain is granodioritic and major element compositions have equivalents in igneous and sedimentary supracrustal rocks. K, Rb, Sr and probably Th concentrations, and K/Rb ratios are normal; the initial isotopic composition of Sr shows the usual range of crustal rocks. However, U is strongly depleted and was lost by a pervasive process, probably dehydration, rather than by anatexis. Comparison with other areas in which major chemical depletions and unusually low initial Sr isotopic ratios are postulated leads to alternative interpretations of these areas which do not involve large scale chemical migration. An intermediate composition for the lower crust may result from a high density of basic intrusions rather than chemical processes.

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