%0 Book Section
%T Geoquímica isotópica (Sr y Nd) de las anortositas (“massif type anorthosites”)grenvillianas de las Sierras Pampeanas Occidentales (Argentina).Fuentes magmáticas e implicaciones geotectónicas
publisher Instituto Geológico y Minero de España
%D 2005
%U 84-7840-592-5
%@ https://hdl.handle.net/20.500.14352/53066
%X Massif-type anorthosites are igneous complexes that consist for the most part of anorthosite, a plagioclase-rich plutonic rock. They are particularly abundant within or near the worldwide Grenvillian mobilebelt (1.0-1.2Ga), which resulted from the assembly of the Mesoproterozoic supercontinent of Rodinia.In two of the most western Sierras Pampeanas (Sierras of Maz and Espinal, NW of Argentina), twoanorthositic igneous complexes have been discovered recently (Casquet et al. 2005a). Coarse-grainedanorthosites is the predominant rock type in these complexes. The age of crystallization is of 1070 ± 41Ma (U-Pb SHRIMP, in zircons). These rocks have a superposed regional metamorphism of Ordovician age(431±30 Ma; U-Pb SHRIMP, in zircons). These complexes are the only ones mentioned in Argentina andare the first of recognized Grenvillian age in Sudamerica.Nd and Sr isotope composition suggest that primary magmas derived from a depleted source. Moreovermoderate contamination with an enriched continental component is also inferred. Nd model agessuggest that the depleted source formed coeval with the anorthosite magmatism, which is compatible witha mantle plume probably related to the early break up of Rodinia.
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