Granulite facies metasomatism; zoned calc-silicate boudins from the Rauer Group, East Antarctica

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Authors:Buick, Ian S.; Harley, Simon L.; Cartwright, Ian C.
Author Affiliations:Primary:
University of Melbourne, Department of Geology, Parkville, Victoria, Australia
Other:
University of Edinburgh, United Kingdom
Monash University, Australia
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 113(4), p.557-571. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1993
Note:In English. 46 refs.; illus. incl. 4 tables, geol. sketch map
Summary:Calc-silicate boudins from the Rauer Group, East Antarctica, were metamorphosed under granulite facies conditions during late Proterozoic (ca. 1,000 Ma) M3 metamorphism. Boudin cores contain low to moderate aCO2 assemblages including wollastonite, grossular-andradite (grandite) garnet, clinopyroxene, scapolite, plagioclase, quartz, and calcite. Petrological and stable isotopic evidence suggests that these core assemblages resulted from pre-peak M3 infiltration of water- rich fluids; there is no evidence for a pervasive fluid phase under peak M3 conditions. The boudins are separated from the surrounding Fe-rich pelites and semi-pelites by a series of concentric, high-variance reaction zones developed under peak M3 conditions. Variations in mineral assemblage, mineral composition and whole rock composition across these zones suggest that they formed by diffusional mass-transfer, controlled principally by a chemical potential gradient in Ca across the original calc-silicate-paragneiss lithological boundary. As a consequence of the near-complete decarbonation of the calc- silicates before the M3 peak, development of the diffusion-controlled reaction zones did not liberate significant CO2 during granulite facies metamorphism. Similar calcite-poor, low aCO2 calc-silicate horizons in other granulite facies terrains are unlikely to have been important local fluid sources during deep crustal metamorphism. (Auth.)
Subjects:Alkaline earth metals; Aureoles; Boudinage; C-13/C-12; Calc-silicate composition; Carbon; Chain silicates; Clinopyroxene; Diffusion; Facies; Framework silicates; Granulite facies; Iron; Isotope ratios; Isotopes; Magnesium; Mass transfer; Metals; Metamorphism; Metasomatism; Migration of elements; Mineral assemblages; O-18/O-16; Orthopyroxene; Oxygen; P-T conditions; Polymetamorphism; Prograde metamorphism; Pyroxene group; Reaction rims; Scapolite; Scapolite group; Sedimentary structures; Silicates; Soft sediment deformation; Stable isotopes; Whole rock; Antarctica; East Antarctica; Prydz Bay; Southern Ocean; Antarctic Ocean; Dragon Point; Elephant Island; Filla Island; Hop Island; Little Italy Island; Long Point; Rauer Group; Viking Island
Abstract Numbers:93M/5003
Record ID:1993019872
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from the Antarctic Bibliography, United States
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