Boron- and phosphate-rich rocks in the Larsemann Hills, Prydz Bay, East Antarctica: Evidence for early Neoproterozoic rifting in an active continental arc?  

Authors / CoAuthors

Grew, E.S. | Carson, C.J. | Christy, A.G. | Boger, S.D.

Abstract

Granulite-facies paragneisses enriched in boron and phosphorus are exposed over a ca. 15 x 5 km area in the Larsemann Hills, East Antarctica. The most widespread are biotite gneisses containing centimeter-sized prismatine crystals, but tourmaline metaquartzite and borosilicate gneisses are richest in B (680-20 000 ppm). Chondrite-normalized REE patterns give two groups: (1) LaN>150, Eu*/Eu < 0.4, which comprises most apatite-bearing metaquartzite and metapelite, tourmaline metaquartzite, and Fe-rich rocks (0.9-2.3 wt% P2O5), and (2) LaN<150, Eu*/Eu > 0.4, which comprises most borosilicate and sodic leucogneisses (2.5-7.4 wt% Na2O). The B- and P-bearing rocks can be interpreted to be clastic sediments altered prior to metamorphism by hydrothermal fluids that remobilized B. We suggest that these rocks were deposited in a back-arc basin located inboard of a Rayner aged (ca. 1000 Ma) continental arc that was active along the leading edge the Indo-Antarctic craton. This margin and its associated back-arc basin developed long before collision with the Australo-Antarctic craton (ca. 530 Ma) merged these rocks into Gondwana and sutured them into their present position in Antarctica. The Larsemann Hills rocks are the third occurrence of such a suite of borosilicate or phosphate bearing rocks in Antarctica and Australia: similar rocks include prismatine-bearing granulites in the Windmill Islands, Wilkes Land, and tourmaline-quartz rocks, sodic gneisses and apatitic iron formation in the Willyama Supergroup, Broken Hill, Australia. These rocks were deposited in analogous tectonic environments, albeit during different supercontinent cycles.

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nonGeographicDataset

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73069

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Keywords

• External PublicationConference Paper

( Theme )

• Antarctic data

( Theme )

• geochemistry

( Theme )

• metamorphism

( Theme )

• tectonic history

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

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2011-11-10T00:00:00

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geoscientificInformation

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[-69.5, -69.3, 76.0, 76.5]

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