A metamorphic and geochemical study of mafic rocks across the Pencksökket-Jutulstraumen Discontinuity, western Dronning Maud Land, East Antarctica

A petrological and metamorphic comparison of Mesoproterozoic metabasic rocks on the easern margin of the Archaean Grunehogna Craton and the adjacent Maud Belt in western Dronning Maud Land, East Antarctica, revealed a difference in peak metamorphic conditions from T = ~275° to 730°C and P=2 to 10.7 kbar over a distance of only 30 km across a major glacial valley. The lower grade constraints were derived from average P-T calculations using THER-MOCALC and thermodynamic modeling of phase equilibria together with chlorite geothermometry. The high-grade P-T constraint for the westernmost part of the Maud Belt closest to the glacier, derived from hornblende-plagioclase thermometry and geobarometric calculations with a garnet amphibolite assemblage, is very similar to that reported for the eastern Maud Belt and, therefore, does not support the concept of a westward decreasing metamorphic field gradient as previously proposed. In conjunction with a recent geochronological study on the eastern Maud Belt, this study suggests that the inferred sub-glacial boundary between the Grunehogna Craton and the Maud Belt, known as the Pencksökket-Jutulstraumen Discontinuity, may represent a major thrust that developed during Pan-African orogenesis (possibly as the continuation of the East African Mozambique Belt into East Antarctica) prior to extension and its development as a normal listric fault or succession of fault slices during the Mesozoic break-up of Gondwana.

Grantor dc:publisher.institution

Department of Geological Sciences

Year dc:date.issued

2005

Author dc:creator

• Grosch, Eugene Gerald

Advisor dc:contributor.advisor

• Frimmel, Hartwig E

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/4199

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/4199