U-Pb data on detrital zircons from Middle Cambrian siliciclastic levels of the Argentinean Precordillera: Implications for the Cuyania Terrane evolution

NAIPAUER, M., CINGOLANI, C.A., VUJOVICH, G.I., AND MCCLELLAND, W.C.

Bariloche

Simposio; VI South American Symposium on Isotope Geology; 2008

INGEIS

U-Pb DATA ON DETRITAL ZIRCONS FROM MIDDLE CAMBRIAN SILICICLASTIC LEVELS OF THE ARGENTINEAN PRECORDILLERA: IMPLICATIONS FOR THE CUYANIA TERRANE EVOLUTION   Naipauer, M.1, Cingolani, C.A.2, Vujovich, G.I.3 and McClelland, W.C.4   1 Cátedra de Geología Argentina (UNLP) calle 60 y 122 s/n 1900, La Plata, Argentina, maxinaipauer@gl.fcen.uba.ar 2 Centro de Investigaciones Geológicas (UNLP-CONICET), calle 1 n. 644, 1900-La Plata, Argentina. 3 Laboratorio de Tectónica Andina (UBA-CONICET), Pabellón II, Ciudad Universitaria, Buenos Aires. 4 Geological Sciences, University of Idaho. USA.   Keywords: Geochronology U-Pb, Cambrian units, provenance, detrital zircons, Argentinean Precordillera.   ABSTRACT Based on a combination of geological evidence, the Argentine Precordillera has been recognized as an early Paleozoic suspect terrane of probable Laurentian origin, whereas other interpretations allow considering a parautochthonous Gondwanian derivation. Detrital zircons geochronological research from several Lower Paleozoic units was carried out during the last years, in order to constrain the paleogeographic models. The objective of the present paper is to extend our understanding regarding provenance of Cambrian units, using U-Pb geochronological data on detrital zircons obtained from siliciclastic levels intercalated in the carbonate platform. The new obtained ages on detrital zircon grains analyzed from the Middle Cambrian Soldano Member of the La Laja Formation and also from the Los Ratones Olistolith, are characterized by a unimodal distribution, with age range from ca. 1360-1380 Ma as the most abundant found within the studied key-time from two localities of the eastern and central Precordillera. The qualitative optical analyses of zircon grains allow us to interpret a provenance from plutonic and volcanic rocks, and with a minor contribution from metamorphic rocks. These results clearly coincide with a derivation from the Granite-Rhyolite Province of Laurentia, based on geochronology and type of source rock. With this data set we discuss the possibility that the detrital zircons of the Cambrian units were either derived from a source presently not exposed, or that they are indicating a direct connection with the Laurentian margin at least since 510 Ma (Middle Cambrian).