INVESTIGADORES
RAPELA Carlos Washington
artículos
Título:
Age and origin of coeval TTG, I- and S-type granites in the Famatinian belt of NW Argentina
Autor/es:
PANKHURST, R.J; RAPELA, C.W.; FANNING, C.M.
Revista:
EARTH AND ENVIRONMENTAL SCIENCE TRANSACTIONS OF THE ROYAL SOCIETY OF EDINBURGH
Editorial:
ROYAL SOC EDINBURGH
Referencias:
Lugar: Edinburgo; Año: 2000 vol. 91.1 p. 151 - 168
ISSN:
1755-6910
Resumen:
Three granitoid types are recognised in the Famatinian magmatic belt of NW
Argentina, based on lithology and new geochemical data: (a) a minor trondhjemite-tonalitegranodiorite
(TTG) group, (b) a metaluminous I-type gabbro-monzogranite suite, and (e) S-type
granites. The latter occur as small cordieritic intrusions associated with I-type granodiorites and as
abundant cordierite-bearing facies in large batholithic masses. Twelve new SHRIMP U-Pb zircon
ages establish the contemporaneity of all three types in Early Ordovician times (mainly 470-
490 Ma ago). Sr- and Nd-isotopic data suggest that, apart from some TTG plutons of
asthenospheric origin, the remaining magmas were derived from a Proterozoic crust-lithospheric
mantle section. Trace element modelling suggests that the TTG originated by variable melting of a
depleted gabbroid source at 10-12kbar, and the I-type tonalite-granodiorite suite by melting of a
more enriched lithospheric source at e. Skbar. The voluminous intermediate and acidic I-types
involved hybridisation with lower and middle crustal melts. The highly peraluminous S-type
granites have isotopic and inherited zircon patterns similar to those of Cambrian supracrustal
metasedimentary rocks deposited in the Pampean cycle, and were derived from them by local
anatexis. Other major components of the S-type batholiths involved melting of deep crust and
mixing with the I-type magmas, leading to an isotopic and geochemical continuum.