U-Pb LA-ICP-MS geochronology of detrital zircon grains from low-grade metasedimentary rocks (Neoproterozoic - Cambrian) of the Mojotoro Range, northwest Argentina

Abstract

The first results of U–Pb detrital zircons were obtained in three lithostratigraphic units of the Puncoviscana Complex in NW Argentina: Chachapoyas, Alto de la Sierra and Guachos Formations. The Chachapoyas Formation has a maximum sedimentation age of 569 Ma and a minimum age of 533 Ma, based on the U–Pb age of an intrusive porphyry granitic. The Alto de la Sierra Formation, composed by sandstones and volcaniclastic rocks, has a maximum age of 543 Ma. A maximum age of 517 Ma is here reported for the deposition of the Guachos Formation, the youngest unit. The contact between the Chachapoyas and Guachos formations is by a tectonic relation, and it's probably coincident with a stratigraphic unconformity between them (unconformity Tilcara I). The Lizoite Formation is overlying by an unconformity (Tilcara II unconformity) the Puncoviscana Complex, and represents the basal unit of the Mesón Group. The provenance zircon data for that formation indicate a maximum depositional age of 513 Ma.