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Geoquímica isotópica (Sr y Nd) de las anortositas (“massif type anorthosites”) grenvillianas de las Sierras Pampeanas Occidentales (Argentina). Fuentes magmáticas e implicaciones geotectónicas

Casquet, César and Galindo Francisco, Mª del Carmen and Rapela, Carlos W. and Pankhurst, R.J. and Baldo, Edgardo G. and Dahlquist, Juan A. and Fanning, C.M. and González Casado, José Manuel and Saavedra, Julio (2005) Geoquímica isotópica (Sr y Nd) de las anortositas (“massif type anorthosites”) grenvillianas de las Sierras Pampeanas Occidentales (Argentina). Fuentes magmáticas e implicaciones geotectónicas. In Geociencias, recursos y patrimonio geológicos : 30º Aniversario del Comité Nacional Español / Programa Internacional de Geociencias (PICG/IGCP). Geología y geofísica (3). Instituto Geológico y Minero de España , Madrid, pp. 123-128. ISBN 84-7840-592-5

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Abstract

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 mobile
belt (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), two
anorthositic igneous complexes have been discovered recently (Casquet et al. 2005a). Coarse-grained
anorthosites is the predominant rock type in these complexes. The age of crystallization is of 1070 ± 41
Ma (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 and
are the first of recognized Grenvillian age in Sudamerica.
Nd and Sr isotope composition suggest that primary magmas derived from a depleted source. Moreover
moderate contamination with an enriched continental component is also inferred. Nd model ages
suggest that the depleted source formed coeval with the anorthosite magmatism, which is compatible with
a mantle plume probably related to the early break up of Rodinia.

Item Type:Book Section
Uncontrolled Keywords:Argentina, Sierras Pampeanas, Neoproterozoic, Anorthosites, Rodinia, Nd model ages
Subjects:Sciences > Geology > Geochemistry
ID Code:12143
Deposited On:02 Feb 2011 10:53
Last Modified:02 Feb 2011 10:53

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