Grenvillian, massif-type anorthosites in the Sierras Pampeanas

CASQUET, C.; PANKHURST, R.J.; RAPELA, C.W.; GALINDO, C.; DAHLQUIST, J.; BALDO, E.; SAAVEDRA, J.; GONZÁLEZ-CASADO, J.M.; FANNING, C.M.

JOURNAL OF THE GEOLOGICAL SOCIETY

The Geological Society of London

Año: 2004 vol. 162 p. 9 - 12

0016-7649

We report the discovery of massif-type anorthosites in the Andean basement of the Western Sierras Pampeanas of Argentina. U–Pb zircon dating (SHRIMP) of a cogenetic gabbronorite dyke yields ages of 1070 ± 41 Ma for igneous emplacement and 431 ± 40 Ma for metamorphism. These anorthosites are petrologically and geochemically comparable to those of the Grenville province of Laurentia. Palaeogeographical reconstructions of Rodinia at 1.0 – 1.1 Ga suggest that the Sierras Pampeanas anorthosites were part of a large anorthosite province in the late Mesoproterozoic.   Keywords: Argentina, Neoproterozoic, Rodinia, SHRIMP zircon dating.