Partial melting during tectonic exhumation of a granulite terrane: an example from the Larsemann Hills, East Antarctica
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Anatectic migmatites in medium-to low-pressure granulite facies metasediments exposed in the Larsemann Hills, East Antarctica, contain leucosomes with abundant quartz and plagioclase and minor interstitial K-feldspar, and assemblages of garnet-cordierite-spinel-sillimanite.Abstract:
Anatectic migmatites in medium- to low-pressure granulite facies metasediments exposed in the Larsemann Hills, East Antarctica, contain leucosomes with abundant quartz and plagioclase and minor interstitial K-feldspar, and assemblages of garnet–cordierite–spinel–ilmenite–sillimanite. Qualitative modelling in the system K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O2, in conjunction with various P–T calculations indicate that the high-grade retrograde evolution of the terrane was dominated by decompression from peak conditions of c. 7 kbar at c. 800 °C to 4–5 kbar at c. 750 °C. Extensive partial melting during decompression involved the replacement of biotite by the assemblage cordierite–garnet–spinel within the leucosomes. These leucosomes represent the site of partial melt generation, the cordierite–garnet–spinel–ilmenite assemblage representing the solid products and excess reactants from the melting reaction. The extraction and accumulation of this decompression-generated melt led to the formation of syntectonic pegmatites and extensive granitic plutons. Leucosome development and terrane decompression proceeded during crustal transpression, synchronous with upper crustal extension, during a progressive Early Palaeozoic collisional event. Subsequent retrograde evolution was characterized by cooling, as indicated by the growth of biotite replacing spinel and garnet, thin mantles of cordierite replacing spinel and quartz within metapelites, and garnet replacing orthopyroxene and hornblende within metabasites. P–T calculations on late mylonites indicate lower grade conditions of formation of c. 3.5 kbar at c. 650 °C, consistent with the development of late cooling textures.read more
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References
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Experimental determination of the fluid-absent melting relations in the pelitic system
Daniel Vielzeuf,John R. Holloway +1 more
TL;DR: In this article, the melting of a natural metapelite under fluid-absent conditions was studied experimentally and a series of P-T, T-XH2O, and liquidus diagrams were proposed.
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The origins of granulites: a metamorphic perspective
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Fluid-absent (dehydration) melting of biotite in metapelites in the early stages of crustal anatexis
TL;DR: Experimental investigation of the fluid absent melting reaction has shown that the reaction has a positive dP/dT at least up to 10 kbar, compared to a calculated backbending in a simplified system.
Journal ArticleDOI
An experimental study of the partitioning of Fe and Mg between garnet and orthopyroxene
TL;DR: In this article, the effects of Calcium on Fe-Mg partitioning between garnet and orthopyroxene were investigated in the pressure-temperature range 5-30 kbar and 800-1,200° C in the FeO-MaggO-Al2O3-SiO2 (FMAS) and CaO-FeO-mgO-aluminous Orthopyroxenes (CFMAS) systems.