Variation in si4+-content of phengites through a three stage deformation sequence |
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| Authors: | Clive A Boulter Arne Råheim |
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| Institution: | 1. Department of Geology, University of Tasmania, Hobart, Australia
2. Research School of Earth Sciences, Australian National University, Canberra, Australia
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| Abstract: | Three important phases of deformation (D1-D3) affect the Precambrian metamorphic rocks of the Strathgordon region, S.W. Tasmania. Textural analysis has related phengite development to the deformation events in quartz + phengite phyllites. Phengite chemistry suggests a prograde metamorphic history at about 4 kb from 400°C at D1 to 450°C at D2. The significant feature of this work is that a sharp break in conditions, shown by a marked change in the composition of the phengites, occurs from D2 to D3, the latter taking place at about 250°C and at a pressure <4 kb. A pronounced hiatus in the deformation history is indicated for the D2/D3 interval. During D3 water was introduced. |
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