CIG   05423
CENTRO DE INVESTIGACIONES GEOLOGICAS
Unidad Ejecutora - UE
artículos
Título:
Isotopic studies on detrital zircons of Silurian-Devonian siliciclastic sequences from Argentinean North Patagonia and Sierra de la Ventana regions: comparative provenance
Autor/es:
URIZ, NORBERTO JAVIER; CINGOLANI, CARLOS ALBERTO; CHEMALE JR. FARIDD; MACAMBIRA, MOACIR B.; ARMSTRONG, RICHARD
Revista:
INTERNATIONAL JOURNAL OF EARTH SCIENCES
Editorial:
SPRINGER
Referencias:
Lugar: Berlin; Año: 2010 vol. 100 p. 571 - 589
ISSN:
1437-3254
Resumen:
The Silurian-Devonian siliciclastic sedimentary units known as Sierra Grande Formation and the upper part of the Ventana Group, crop out in the eastern area of the North-Patagonian Massif and in the Ventania system, towards the Atlantic border of Argentina. Both sequences show similar stratigraphical characteristics and were deposited in a shallow marine platform paleoenvironment. If both units have been deposited within separate basins or, if they have a common sedimentological evolution is still a mater of debate. Previous contributions have provided evidence of an allochthonous Patagonia terrane that amalgamate to Gondwana during the Permian-Triassic. However, other lines of research support a crustal continuity southwards, where the Pampean and Famatinian Belts extend into the northern Patagonia. In either case, the detrital input to the Eo-Mesopaleozoic basins generated along the passive margin tectonic setting should reflect the sedimentary model. In this contribution, new age data on the sedimentary provenance of these units is provided by U-Pb and Lu-Hf isotopic studies on detrital zircons, using LA-ICP-MS and SHRIMP methodologies. These data show that are striking similarities in the main age distributions and frequency peaks of detrital zircon ages between the Sierra Grande Formation and the Providencia Formation (Ventana Group). The main sedimentary sources of detrital zircons are of Cambrian-Ordovician and Neoproterozoic in age, while a secondary mode is Mesoproterozoic. Zircons from the older cratonic sources (Mesoarchean-Paleoproterozoic ages) are scarcely recorded. The sample from the upper section of the Lolén Formation (upper Ventana Group) shows an important change in the sedimentary provenance, with a main mode of Mesoproterozoic detrital zircons. The younger zircon ages are restricted to the Silurian-Devonian (maximum depositional age for the study units). We proposed detrital source areas considering the orogenic cycles known for southwest South America: Famatinian, Pampean (Brasiliano), Sunsas or "Grenvillian" and Transamazonian. Finally we discuss the paleogeographic model that fit with the new isotopic data integrated the Sierra Grande-Ventania systems and the comparison with the other Gondwanan regions.