Reaction texture and Fe-Mg zoning in granulite garnet from SØstrene Island, Antarctica: Modeling and constraint on the time scale of metamorphism during the Pan-African collisional event |
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| Authors: | J Ganguly B J Hensen W Cheng |
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| Institution: | (1) Department of Geosciences, University of Arizona, 85721 Tucson, AZ, USA;(2) Department of Applied Geology, University of New South Wales, 2033 Kensington, NSW, Australia |
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| Abstract: | Garnets from the S⊍strene island, Antarctica, show reaction textures corresponding to two metamorphic episodes, one at c.
1000 Ma (M1) and the other at c. 500 Ma (M2). The latter is associated with a Pan-African tectono-metamorphic event that has
been interpreted to represent a continent-continent collision followed by extensional collapse. Reaction-diffusion modeling
of the compositional zoning of garnet associated with the development of reaction texture during M2 yields a time scale of
∼ 5–16 Myr for the duration of the peak of this overprinting metamorphism at ∼ 730 ± 20‡C. The associated velocity of the
reaction front is ∼∼ 5.0-1.6Μm/Myr. The inferred duration of peak metamorphism during the Pan-African event seems to be in
good agreement with the available U-Pb SHRIMP ages of zircon and monazite that may be interpreted to have formed at the beginning
and end stages of crystallization of granite during the metamorphic peak. |
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| Keywords: | Time scale tectono-metamorphism diffusion reaction |
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