Isotopic studies on detrital zircons of Silurian–Devonian siliciclastic sequences from Argentinean North Patagonia and Sierra de la Ventana regions: comparative provenance

Abstract

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, toward the Atlantic border of Argentina. Both sequences show similar stratigraphical characteristics and were deposited in a shallow marine platform paleoenvironment. 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 southward, where the Pampean and Famatinian events 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 sources. 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. The main sedimentary sources of detrital zircons for both regions are of Cambrian-Ordovician and Neoproterozoic age, while a secondary mode is Mesoproterozoic. Zircons from older cratonic sources (Mesoarchean-Paleoproterozoic ages) are scarcely recorded. The sample from the upper section of the Devonian Lolén Formation (Ventana Group) shows an important change in the sedimentary provenance, with a main mode of Mesoproterozoic detrital zircons. Detrital source areas considering the orogenic cycles known for southwest South America (Famatinian, PampeanBrasiliano, Mesoproterozoic-'Grenvillian' and Paleoproterozoic-'Transamazonian') are proposed.

Provenance and reconnaissance study of detrital zircons of the Palaeozoic Cape Supergroup in South Africa: revealing the interaction of the Kalahari and Río de la Plata cratons

“…7). The similarity in detrital zircon age populations of the Cape Supergroup on the Kalahari Craton (this study) with those of early Palaeozoic successions in Eastern Argentina (Uriz et al 2010) support the proposed initial extend of the Cape Basin from the Kalahari Craton into Eastern Argentina ( Fig. 2) (Tankard et al 1982;Rapela et al 2003;Pankhurst et al 2006;Van Staden et al 2010b).…”

“…6). Detrital zircons of Siluro-Devonian age were also identified in Devonian successions in Eastern Argentina (Uriz et al 2010) and may point to a source in Patagonia. A Silurian magmatic event is known from the Deseado Massif in southern Patagonia (Fig.…”

Patagonia: where does it come from?

“…5), could represent the conjugate margin sequence of the lower Beacon Supergroup. Both sequences share a common Devonian history, but the sedimentation was interrupted in Sierra Grande in late Halpern, 1968;Ramos, 1983, and data from (a) Uriz et al, 2011) (Siddoway and Fanning, 2009) associated with subduction of the Marie Bird Land terrane as proposed by Dalziel and Grunow (1985). This magmatic arc with similar polarity is seen in western Patagonia (Fig.…”

“…The U-Pb detrital zircon analyses show a maximum sedimentation age of ca. 428 Ma (Uriz et al, 2011) for the middle part of this 2,130m thick sequence.…”

Geochronology and sources of late Neoproterozoic to Cambrian granites of the Saldania Belt

“…Both sets of data are interpreted as being the last magmatic phases of these respective regions. The results of the U-Pb study on detrital zircons presented by Uriz et al (2010) point to a substantial contribution from Neoproterozoic-Lower Cambrian and secondary Middle Cambrian crustal sources for the Silurian-Devonian units of the Sierra de Ventana, which probable came from the covered basement.…”