Browsing by Author "Ghiglione, M.C."
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Item The low‑grade basement at Península La Carmela, Chilean Patagonia: new data for unraveling the pre‑Permian basin nature of the Eastern Andean Metamorphic Complex(2021) Rojo, D.; Calderón, Mauricio; Ghiglione, M.C.; Suárez, R.J.; Quezada, P.; Cataldo, J.; Hervé, F.; Charrier, R.The Eastern Andean Metamorphic Complex at Península La Carmela (48°50’S) consists of quartz-rich metaturbiditic sequences with tectonic slices of pillow metabasalt bodies deformed under low-grade metamorphic conditions. Previous and new detrital zircon U–Pb geochronological data from metasandstones indicate a preferred early Carboniferous maximum depositional age of the protolith, interpreted from the youngest single zircon grains of several metasedimentary rocks in the area. The wide spectrum of zircon ages from Península La Carmela, includes Neoproterozoic-early Paleozoic components and subordinate ancient zircon grains (>2200 Ma). They were sourced from cratonic regions and/or reworked material from older metasedimentary successions and plutonic belts in southwestern Gondwana (e.g., North Patagonian and Deseado massifs or from the Tierra del Fuego Igneous and Metamorphic Complex). The pillow metabasalts have geochemical afnities of normal mid-oceanic ridge basalts and island-arc tholeiites with Nb–Ta negative anomalies, derived from a depleted mantle source (εNdt of+6 and+7.5). In consideration that pillow metabasalts with ocean island basalt afnities are reported, we propose that metaturbiditic successions and metabasalts were tectonically juxtaposed within a pre-Permian accretionary wedge of an active continental margin, after the development of island arcs and back-arc marginal basins.Item Thermochronological Evidence for Eocene Deformation in the Southern Patagonian Andes: Linking Orogenesis Along the Patagonian Orocline(2023) Goddard, A.L.Stevens; Fosdick, J.C.; Calderón, Mauricio; Ghiglione, M.C.; VanderLeest, R.A.; Romans, B.W.Thermochronologic results from zircon fission track and (U-Th)/He data collected across the Patagonian batholith, basement and thrust belt of the southern Patagonian Andes between 51°S and 53°S resolves new spatiotemporal patterns of Paleogene rock cooling that allows us to reconstruct deformational and erosional events along- and across-strike. Our study applies a novel modeling strategy, the Path Family Approach, to filter geologically plausible thermal solutions from inverse modeling results for rocks in this study according to a sample's structural and tectonic context. Our results identify minimal cooling and interpreted exhumation of batholith rocks throughout the Paleogene. However, in the western domain we identify synchronous cooling of Jurassic volcaniclastic rocks in the thrust belt both along- and across-strike between 50 and 35 Ma, which we interpret as a period of out-of-sequence deformation that coincides with the start of a distinct period of orogenesis in the Fuegian Andes (54°S). This finding may suggest that the southern Patagonian Andes and Fuegian Andes evolved as a connected orogenic system along the bend of the Patagonian orocline. In the central domain, modeled cooling of thermally reset Cretaceous basinal strata from 60 to 50 Ma corresponds to a well-recognized erosional unconformity in the adjacent Cenozoic foreland depocenter, indicating that contemporaneous exhumation occurred beyond the margins of the basin. Although not diagnostic, exhumation within the orogenic belt, beyond the Cenozoic foreland basin, provides a new regional context to interpret the cause of this regional erosion event. Collectively these results inform the Paleogene tectonic evolution of the orogen.