Magmatic sources, setting and causes of Eocene to Recent Patagonian plateau magmatism (36°S to 52°S latitude)

摘要: Continental back-arc and within-plate basaltic volcanic provinces provide a view into the evolution of mantle beneath continents mass flux materials that are subducted, but not extracted by arc volcanism. One largest continental mafic is Patagonian province where large plateau events ranging in age from late Paleocene to Recent have occurred absence major extension. The produced Eocene Posadas Formation (~ 46°S 50°S), Oligocene early Miocene Somuncura magmatic (41°S 43°S plus similar magmas up 46°S), Pliocene lavas east Chile Triple Junction (~46°S 49°S), Payunia (36°S 38.5°S). Tectonically, been respectively associated with Miocene-Recent collisions Farallon-Aluk Nazca-Antarctic spreading ridges trench, thermal anomaly linked Oligocene/early changes plate convergence vectors, steepening formally shallow subduction zone. Between 45°S-50°S Tertiary volcanism was largely absent, show almost no trace element affinity rocks as indicated Ba/La ratios 20) La/Ta 25). same true for pre-29 Ma pre-20 regions. Associated erupted near can higher ratios. This situation contrasts post-29 post-20 north 45°S which over 30 20 occur west. These fit introduction components magma sources result interaction Paleogene subducting slab region dehydration shallowly region. At time, Nd Sr isotopic most plot OIB field (most Σ = +5 -1; 87 Sr/ 86 0.7035 0.7048) being depleted, some enriched. Across plateau, these tectonic, chemical, data consistent volume due tectonic perturbations provoke melting hot has on verge since Mesozoic breakup Gondwana.