Genesis of the migmatites of Breidvagnipa, East Antarctica

概要

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Various types of migmatites and peraluminous granites are widely distributed at Breidvagnipa, which is situated in the granulite-facies part of the Lutzow-Holm Complex (LHC) on the eastern coast of Lutzow-Holm Bay, East Antarctica. The migmatites consist of paleosome, melanosome, and leucosome, and are intimately associated with peraluminous granite. Modes of field occurrence and petrological features are consistent with the paleosome, melanosome, and leucosome and granite representing original rock, restite, and melt, respectively. The migmatites at Breidvagnipa are therefore regarded as the result of partial melting of pelitic metamorphic rocks during high-grade metamorphism in the LHC. Thermobarometric calculations indicate peak pressure and temperature conditions at Breidvagnipa of ∿0.8GPa and 870℃. The age of the high-grade metamorphic event is estimated at ∿570Ma, on the basis of a Rb-Sr whole rock isochron from the migmatite. This age is consistent with previously reported U-Pb zircon ages from the LHC.
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