The Signature of Metasomatized Subcontinental Lithospheric Mantle in the Basaltic Magmatism of the Payenia Volcanic Province, Argentina

Abstract The Payenia region of Argentina (34.5–38°S) is a large Pliocene‐Quaternary volcanic province basaltic compositions in the Andean Cordillera foothills representing northernmost extent back‐arc volcanism Southern Volcanic Zone (SVZ). Although chemical diversity basalts has been characterized previously, processes and sources responsible for such variation remain controversial. Here, we report new whole‐rock major trace element concentrations, Sr‐, Nd‐, Hf‐, Pb‐isotope ratios high‐precision olivine oxygen‐isotope suite 35 alkaline from Payenia. These lavas have elements that define compositional range arc‐influenced to intraplate signature. Variable crustal contamination and/or recent slab‐derived inputs inadequately account elemental isotopic systematics spatial variations lavas. We present simple forward model indicating early metasomatism subsequent melting metasomatized subcontinental lithospheric mantle (SCLM) significantly contributed lava range. Isotopic ingrowth calculations radiogenic Sr, Nd, Hf, Pb suggest SCLM occurred at 50–150 Ma, consistent with timing breakup Gondwana development proto‐Pacific arc. Variations δ 18 O values modeled melts indicate within can fractionate oxygen isotopes even when metasomatizing melt MORB‐like values, providing different explanation low‐δ signatures observed continental arc settings.