Retrowedge-related Carboniferous units and coeval magmatism in the northwestern Neuquén province, Argentina

摘要: The studied Carboniferous units comprise metasedimentary (Guaraco Norte Formation), pyroclastic (Arroyo del Torreon and sedimentary (Huaraco Formation) rocks that crop out in the northwestern Neuquen province, Argentina. They form part of basement Basin are mostly coeval with Late Paleozoic accretionary prism complex Coastal Cordillera, south-central Chile. U–Pb SHRIMP dating detrital zircon yielded a maximum depositional age 374 Ma (Upper Devonian) for Guaraco Formation 389 Arroyo Formation. Detrital magmatic from grouped into two main populations Devonian Ordovician (Famatinian) ages. In Formation, also (Famatinian), as well Neoproterozoic Mesoproterozoic both units, there is conspicuous population grains (from 406 ± 4 to 369 5 Ma), indicative active magmatism at time range. eHf values this range between −2.84 −0.7, TDM-(Hf) Mesoproterozoic, suggesting primary sources contained small amounts recycled crustal components. chemical composition corresponds recycled, mature polycyclic sediment continental provenance, pointing passive margin minor inputs rocks. signature Huaraco indicates arc was provenance sediments unit, which consistent occurrence tuff—mostly very scarcely Formation—with volcanic-arc signature, jointly indicating during deposition units. interpreted represent deposits Lower (younger than older 326 Ma) precede onset Chile extend earliest stage accretion, retrowedge position. formations considered be basin early frontal (Eastern Series) presence volcanism provides evidence Mississippian can correlated limited exposures same Frontal Cordillera (Argentina). would have migrated West (Coastal Batholith) Pennsylvanian–Permian times (coevally later basal prism/Western Series). source origin discussed various possible geotectonic scenarios, preferred model being developed Chilenia block, related west-dipping subduction beneath before shortly after its collision against Cuyania/Gondwana, around 390 not linked independent, Devonian–Mississippian arc, south, Patagonia.