Regional metamorphism of the Mathinna Group, northeast Tasmania
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 × 100 km. The b 0 white mica variation (b 0 9.020 ± 0.008 Å) 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.
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Lachlan Fold Belt;
Document Type: Research Article
North Flinders Exploration, 24 Greenhill Rd, Wayville, SA 5034, Australia
School of Earth Sciences, University of Tasmania, Tas. 7001, Australia
Mineral Resources Tasmania, PO Box 56, Rosny Park, Tas. 7018, Australia
Centre for Ore Deposit Research, University of Tasmania, Tas. 7001, Australia
Publication date: April 1, 2001