U-Pb and Lu-Hf isotope systematics of lower crust from central-southern Mexico - Geodynamic significance of Oaxaquia in a Rodinia Realm
Por:
Weber, B, Scherer, EE, Schulze, C, Valencia, VA, Montecinos, P, Mezger, K, Ruiz, J
Publicada:
1 sep 2010
Resumen:
Combined U-Pb ages and Lu-Hf isotope systematics of individual zircon grains from lower crustal rocks of late Mesoproterozoic (Grenville) age, reveal a long geologic evolution of the Oaxaquia terrane (also Oaxaquia) of E and S Mexico. Zircon grains from migmatites, which are host rocks of the AMCG (anorthosite-mangerite-charnockite-granite) suite, have complex internal structures. They contain zoned cores, surrounded by high-U zones, and low-U metamorphic overgrowths. Most of these grains crystallized at similar to 1.2 Ga, but some cores are as old as similar to 1.35 Ga. Igneous crystallization of the protoliths was followed by migmatization and by granulite facies metamorphism at similar to 1.0 Ga, and late stage retrogression. Lutetium-hafnium isotope systematics reveal that both AMCG and host rocks have a limited range of (176)Hf/(177)Hf((i)) (0.28215-0.28224) with epsilon(Hf(1.2 Ga)) approximate to+5 to +7 indicating crust formation from a depleted source throughout the Oaxaquia te
Filiaciones:
Schulze, C:
Univ Nacl Autonoma Mexico, Inst Geol, Coyoacan 04510, DF, Mexico
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