Geology of the Bunger Hills-Denman Glacier region, East Antarctica

The Bunger Hills area, which forms part of the East Antarctic Shield, consists predominantly of

granulite facies orthogneiss (pyroxene-quartz-feldspar gneiss), with subordinate maficgranulite and garnet, sillimanite, and

cordierite-bearing paragneiss. The igneous precursors of granodioritic orthogneiss crystallised about 1500 - 1700 Ma ago,

whereas late Archaean (2640 Ma) tonalitic orthogneiss occurs in the Obruchev Hills, in the southwest of the area. Metamorphism

reached a peak of about 750 - 800 ° C and 5 - 6 kb (Mj) 1190±15 Ma ago (U-Pb zircon age) and was accompanied by the first of

three ductile deformation events (Dj). Voluminous, mainly mantle-derived plutonic rocks were emplaced between 1170 (during D 3 )

and 1150 Ma. They range in composition from gabbro, through quartz gabbro, quartz monzogabbro, and quartz monzodiorite, to granite.

Abundant dolerite dykes, of at least four chemically distinct groups, were intruded at about 1140 Ma. Their intrusion was associated

with the formation of shear zones, indicating at least limited uplift; all subsequent deformation was of brittle-ductile or brittle

type. Alkaline mafic dykes were emplaced 500 Ma ago. Marked geochronological similarities with the Albany Mobile Belt of Western

Australia suggest that high-grade metamorphism in both areas was the result of continental collision between the Archaean Yilgarn

Craton of Australia and the East Antarctic Shield. However, Gondwana reconstructions and the composition of the plutonic rocks

suggest that the Bunger Hills metamorphics may have formed in an Andean-type continental arc, with the actual collision zone

having been to the east of the present Bunger Hills. Exposures west of the Denman Glacier are also mainly granulite-facies

gneiss, intruded by a variety of mafic to felsic plutonic rocks. They differ from the Bunger Hills in being partly derived

from Archaean protoliths (- 3000 Ma), in lacking isotopic evidence for a Mesoproterozoic high-grade event, and in not being

intruded by dolerite dyke swarms. They also show evidence of much more extensive 500 - 600 M a (Pan-African) metamorphism

and plutonism (syenite to granite), and in this regard they are comparable with the Leeuwin Block metamorphics of southwestern

Australia, although these were derived from significantly younger protoliths (T^D model ages: 1100 - 1500 Ma). If this early

Palaeozoic activity was also a consequence of continental collision, it would explain the markedly different geological history

of the terranes on either side of the Denman Glacier and could account for the final uplift of the Bunger Hills. However, the

compressional tectonic regime implicit in the collision hypothesis was followed by an extensional regime, which, in southwestern

Australia, eventually resulted in the formation of the Perth Basin rift zone. This structure is aligned with the Denman Glacier

trough on our preferred Gondwana reconstruction, suggesting that it may have extended well to the south before the breakup of

Gondwana.

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Date (Publication)
1996-01-01T00:00:00
Citation identifier
Geoscience Australia Persistent Identifier/https://pid.geoscience.gov.au/dataset/ga/7

Citation identifier
Digital Object Identifier/http://dx.doi.org/10.26186/5c638cd2a20a0

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Australian Geological Survey Organisation

 Canberra
Author

Sheraton, J.W.

 1
Author

Tingey, R.J.

 2
Author

Oliver, R.L.

 3
Author

Black, L.P.

 4
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Bulletin

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244

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0644452471

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Commonwealth of Australia (Geoscience Australia)
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Commonwealth of Australia (Geoscience Australia)

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Download the Bulletin (pdf)

Download the Bulletin (pdf)

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Australian Government Security ClassificationSystem

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2018-11-01T00:00:00
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Commonwealth of Australia (Geoscience Australia)

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Document
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Legacy AGSO BMR Bulletins

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Date info (Revision)
2018-04-20T06:13:55
Date info (Creation)
1999-08-03T00:00:00

Metadata standard

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AU/NZS ISO 19115-1:2014

Metadata standard

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ISO 19115-1:2014

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ISO 19115-3

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Geoscience Australia Community Metadata Profile of ISO 19115-1:2014

Edition

Version 2.0, September 2018

Citation identifier
https://pid.geoscience.gov.au/dataset/ga/122551

 
 

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