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Regional metamorphism of the Mathinna Group, northeast Tasmania

journal contribution
posted on 2023-05-16, 13:18 authored by Patison, NL, Ronald BerryRonald Berry, Davidson, GJ, Taylor, BP, Bottrill, RS, Manzi, B, Ryba, J, Shepherd, RE
Regional variations in illite crystallinity of the Ordovician-Devonian Mathinna Group of northeast Tasmania indicates that metamorphic grade is dominantly anchizonal (200-300°C, sub-greenschist facies) over an area of 80 km x 100 km. The b0 white mica variation (b0 9.020∓0.008Å) is characteristic of intermediate pressure Barrovian-type metamorphism. Peak metamorphism does not correlate with stratigraphic position and does not change across most of the large faults, indicating that peak metamorphism occurred after east-directed thrusting and as a result of crustal thickening. Most Devonian granites in northeast Tasmania intruded at much lower pressure than the peak metamorphic conditions, suggesting very rapid unroofing in the Middle Devonian. These results are very similar to the metamorphic characteristics reported from the Lachlan Fold Belt in Victoria. The metamorphic history is used to support a thin-skinned model for the deformation in a tectonic wedge that tapered to the east and was subsequently exhumed by backthrusting to the west.

History

Publication title

Australian Journal of Earth Sciences

Volume

48

Pagination

281-292

ISSN

0812-0099

Department/School

School of Natural Sciences

Publisher

Blackwell Science Asia

Place of publication

Carlton, Victoria, Australia

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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