In situ zircon U–Pb and Lu–Hf isotope systematic on magmatic rocks: Insights on the crustal evolution of the Neoproterozoic Goiás Magmatic Arc, Brasília belt, Central Brazil.

Autor: Matteini, M., Junges, S.L., Dantas, E.L., Pimentel, M.M., Bühn, B.
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Zdroj: Gondwana Research; Jan2010, Vol. 17 Issue 1, p1-12, 12p
Abstrakt: Abstract: The Mara Rosa arc constitutes the northern portion of the Goiás Magmatic Arc, an important tectonic component of the Brasília Belt that represents the result of the convergence of the Amazonian and San Francisco cratons between 900 and 600 Ma. New in situ zircon U–Pb and Lu–Hf isotope data by LA-MC-ICP-MS on representative magmatic rocks permitted to characterize three Neoproterozoic magmatic events in the Mara Rosa arc. Zircons from a metavolcanic rock yielded a U–Pb crystallization age of 916±5 Ma with positive ε Hf values (+8 to +12) suggesting that the host magma derived from a depleted mantle. Two orthogneisses showed heterogeneous zircon populations: the youngest zircons from the two samples gave U–Pb crystallization ages of 792±8 Ma and 811±7 Ma respectively; the abundant inherited zircons (with Meso- to Paleoproterozoic U–Pb ages) showed, for both samples, negative ε Hf and old T DM values, suggesting an important contribution of Paleoproterozoic to Archean crust in the petrogenesis of the host magmas. Zircons from post-orogenic qz-diorite yielded a crystallization age of 638±4 Ma, with a variation in ε Hf values (+1 to +8) suggesting that the host magma involved both a juvenile and a recycled older crustal components. [Copyright &y& Elsevier]
Databáze: Supplemental Index
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