INSTITUTO SUPERIOR DE CORRELACION GEOLOGICA
Unidad Ejecutora - UE
The San Blas Pluton: An Example of the Carboniferous Plutonism in The Sierras Pampeanas, Argentina
J.A. DAHLQUIST, R.J. PANKHURST, C.W. RAPELA, C. CASQUET, C.M. FANNING, P.H. ALASINO, M. BÁEZ
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Elsevier Science Ltd.
Lugar: Oxford, USA; Año: 2006 vol. 20 p. 341 - 341
Abstract New U-Pb zircon sensitive high-resolution ion microprobe (SHRIMP) data is obtained from the San Blas Pluton (SBP), in the northeastern Sierra de Velasco, Sierras Pampeanas. A precise Carboniferous age (340 ± 3 Ma) is established for the SBP, which intrudes Ordovician granitoids developed during the Famatinian orogeny, confirming previous field observations that indicated later emplacement of the SBP. The SBP illustrates several petrological and geochemical characteristics of previously reported Carboniferous granitoids in the Sierras Pampeanas. Their generation is consistent with a regional reheating of the crust at ~ 342 Ma, resulting in the formation of relatively large amounts of granitic melts, which were emplaced into higher crustal levels along of master fractures (older master shear zones of Lower Paleozoic age). The SBP can be chemically defined as a typical A-type granitoid related to post-collisonal or post-orogenic magmatism. Its high REE content and extraordinarily high U and Th concentrations may have economic significance. Many previously published Devonian and Carboniferous K-Ar dates are reset Ordovician ages, but the existence of other Carboniferous bodies in the Sierra de Velasco cannot be discounted until detailed mapping of the whole Sierra is completed.