Resumo

VUJOVICH, GI  e  OSTERA, HA. Evidence of the Pampean cycle in the basament of the north-western sector of Sierra de San Luis. Rev. Asoc. Geol. Argent. [online]. 2003, vol.58, n.4, pp.541-548. ISSN 0004-4822.

A preliminary zircon U-Pb age is presented for a feldspar-biotite gneiss from the Nogoli Metamorphic Complex, Sierra de San Luis, at San Francisco del Monte de Oro. The data show a cristallization age of 554 ± 4,8 Ma, which represents one of the first evidences of the Pampean Cycle in this geological setting. An episodic lead loss for Cretaceous times (112 ± 23 Ma) is postulated, based on the lower intercept of the discordia line. This age could be associated with anomalous thermal gradients due the extensional and rifting processes which affected Gondwana during the opening of the South Atlantic Ocean.

Palavras-chave : U-Pb ages; Zircons; San Luis Range; Sierras Pampeanas; Pampean Cycle.

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