Extending the Pampean orogen in western Argentina: New evidence of Cambrian magmatism and metamorphism within the Ordovician Famatinian belt revealed by new SHRIMP U–Pb ages

LARROVERE, MARIANO A.; CASQUET, CÉSAR; ACIAR, R. HERNÁN; BALDO, EDGARDO G.; ALASINO, PABLO H.; RAPELA, CARLOS W.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021 vol. 109

0895-9811

New SHRIMP U?Pb zircon and monazite ages from the Sierra de Fiambal´a (Sierras Pampeanas, NW Argentina)record coeval granitoid peraluminous magmatism and high-grade metamorphism at ca. 525 Ma (LowerCambrian) that resulted from the collisional Pampean orogeny. The Sierra de Fiambal´a, however, is well withinthe Ordovician accretionary Famatinian orogenic belt and west of what is commonly regarded as the Pampeanorogenic belt in the Eastern Sierras Pampeanas (ESP). It is thus an inlier that can be correlated chronologicallyand stratigraphically with the Pampean high-grade metamorphic domain in the Sierras de C´ordoba (ESP).Moreover, in the Fiambal´a inlier, Ediacaran to early Cambrian meta-sedimentary rocks of the Ancaj´an Series, ofan alleged Laurentian source, predominate relative to the Puncoviscana Formation of Gondwanan provenance.Two tectonic interpretations are proposed for the origin of the Fiambal´a inlier: (1) it is a Pampean basementthrusted westward during the Famatinian orogeny or (2) it was rifted away from the main Pampean orogenic beltsometime between the end of the Pampean orogeny and the start of the Famatinian orogeny and later reworkedby the latter in coincidence with the proposal by Weinberg et al. (2018). The evidence given here confirms thatrocks of the Pampean orogen extend far westward of the main Pampean belt (≥300 km).