Boron- and phosphate-rich rocks in the Larsemann Hills, Prydz Bay, East Antarctica: tectonic implications

Autor:	Steven D. Boger, Edward S. Grew, Andrew G. Christy, CJ Carson
Rok vydání:	2013
Předmět:	geography geography.geographical_feature_category Tourmaline Geochemistry Geology Ocean Engineering engineering.material Granulite Continental arc Gondwana Craton Tectonics engineering Biotite Water Science and Technology Gneiss
Zdroj:	Geological Society, London, Special Publications. 383:73-94
ISSN:	2041-4927 0305-8719
DOI:	10.1144/sp383.8
Popis:	Granulite-facies paragneisses enriched in boron and phosphorus are exposed over c. 15 x 5 km(2) in the Larsemann Hills, Antarctica. The most widespread are biotite gneisses containing centimetre-sized prismatine crystals, but tourmaline metaquartzite and borosilicate gneisses are richest in B (676-19 700 mu g/g or 0.22-6.34 wt%; B2O3). Chondrite-normalized rare-earth element (REE) patterns give two groups: (1) La-N > 150, Eu*/Eu 0.4, which comprises most borosilicate and sodic leucogneisses (2.5-7.4wt%; Na2O). Enrichment in boron and phosphorus is attributed to premetamorphic hydrothermal alteration, either in a rifted, most likely marine basin or in a mud volcanic system located inboard of a c. 1000 Ma continental arc that was active along the leading edge of the Indo-Antarctic craton. This margin developed before collision with the Australo-Antarctic craton (c. 530 Ma) merged these rocks into Gondwana and sutured them into their present position in Antarctica. Rocks lithologically similar to those in the Larsemann Hills include prismatine-bearing granulites in the Windmill Islands, Wilkes Land, and tourmalinequartz rocks, sodic gneisses and apatitic iron formation in the Willyama Supergroup, Broken Hill, Australia.
Databáze:	OpenAIRE
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