SciELO - Scientific Electronic Library Online

 
vol.33 issue2Paleoenvironments and sequential stratigraphy of Ordovician marginal marine deposits of Sierra de Zapla (Sierras Subandinas, northwestern Argentina) and their relation with the Central Andean BasinRelation of surface and underground waters in Chungará and Cotacotani lake districts, northern Chile: an isotopic study author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand

Journal

Article

Indicators

Related links

Share


Revista geológica de Chile

Print version ISSN 0716-0208

Abstract

MURRA, Juan A  and  BALDO, Edgardo G. Tectonothermal ordovician evolution of the western margin of the Famatinian magmatic arc: metamorphism of the mafic and ultramafic rocks of Sierra de la Huerta -Las Imanas (Pampean Ranges, Argentina). Rev. geol. Chile [online]. 2006, vol.33, n.2, pp.277-298. ISSN 0716-0208.  http://dx.doi.org/10.4067/S0716-02082006000200004.

An important magmatic and tectonometamorphic activity of Early and Middle Ordovician age is registered in the pre-Andean basement of the Sierras Pampeanas of Argentina. These were linked to the development of a continental magmatic arc during the Famatinian Orogeny, resulting from the approach and attachment of an alleged exotic terrane (the Precordillera Terrane), to the south western Gondwana's margin (present coordinates). A suit of meta-mafic and ultramafic rocks are exposed in the Sierras de La Huerta and Las Imanas, at the western limit of the famatinian orogen. Metaperidotites (Ol-Opx-Cpx-Am-Spl), coronitic metapyroxenites (Opx-Cpx-Spl-Am-Pl), metaquartz-norites (Opx-Pl-Am-Qtz-Bt±Grt) and metadiorites (Pl-Am-Qtz-Bt-Ep) are associated with metasedimentary rocks (marbles, gneisses and migmatites with Sil+Kfs+Grt) that reached the peak and post-peak conditions of metamorphism at middle Ordovician time. The meta-mafic rocks record a first high-grade metamorphic event (M1-730ºC and 8.4±0.5 kbar) and a second lower pressure event (M2, 720ºC and 4.5 kbar) with Cum+Hbl+Mag in a coronitic assemblage. The meta-ultramafic rocks also record the two metamorphic events, but only for the second one it was possible to calculate the P-T conditions. At latitude 32º30'S, the Famatinian magmatic arc shows a systematic compositional variation normal to its trend, i.e. in an east-west direction, which could be related to present erosion levels. In this context, the mafic and ultramafic units of Sierras de La Huerta and Las Imanas, probably represent the deepest levels of the magmatic arc which is consistent with the position that they show marginal to the orogenic belt, i.e., where the uplift and erosion rates were larger

Keywords : Famatinian Orogen; Sierras Pampeanas; mafic-ultramafic; PT-path; Argentina.

        · abstract in Spanish     · text in Spanish

 

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License