THE CONTINENTAL CRUST OF NORTHEASTERN PATAGONIA

RAPELA, CARLOS; PANKHURST, ROBERT

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2020

0002-7014

21 1- Abstract22 The basement of northeastern Patagonia is characterized by early Paleozoic igneous and23 metamorphic rocks that do not crop out in the central, western and Andean sectors of the24 North Patagonian Massif. A review of U-Pb geochronology, geochemistry, and the Nd, Sr,25 Hf and O isotope signature of the early Cambrian and Early Ordovician magmatic rocks26 supports the hypothesis that the continental crust of northeastern Patagonia was essentially27 continuous with that of the Eastern Sierras Pampeanas in early Cambrian times.28 Mesoproterozoic lower crust is also inferred for this sector. New zircon Hf and O analyses29 of early Cambrian (Pampean) granites in the Sierras Pampeanas are indistinguishable from30 those of Cambrian granite in NE Patagonia, indicating an important crustal component in31 the source. The detrital zircon age patterns of the inferred basement are also similar in the32 two regions, strongly suggesting a southern Kalahari provenance. A modified hypothesis to33 explain the continuity of NE Patagonia with the Pampean belt of the Sierras Pampeanas34 during early Cambrian times, as well as their SW Gondwana geological affinity, is to35 consider this entire belt as an outboard sector of the mid-Cambrian rifting observed along36 the South America?South Africa?Weddell Sea margin. The detached sector would then37 have become juxtaposed against the Río de la Plata craton across the right-lateral Córdoba38 fault in late Cambrian times.