Phantom recycled carbonates and mantle pyroxenites: insight from the low-δ26Mg intraplate basaltic province across central-eastern Asia

Abstract

Mass recycling from subduction to magmatic extrusion shapes our habitable environment and Earth's interior. Subducted igneous crust may form pyroxenites before participating magmatism, but the deep journey of associated carbonates remains unclear. Here we report new Mg-isotope data for ˜89 to 81 Ma basaltic rocks in Langshan area, central Asia (δ 26 Mg = -0.391 to -0.513 synthesis for post-110 Ma basalts across eastern Asian continent. The merged low-δ 26 Mg basaltic province normally interpreted as derivations from carbonated sources paradoxically displays geochemical signatures (low Ca/Al and high K 2 O contents) resembling partial melts of uncarbonated sources. Negative correlations of δ 26 Mg vs TiO 2 and FCKANTMS, the proxy of pyroxenitic melts, and adiabatic melting modeling suggest presence of Mg-isotopically light source pyroxenites transformed from decarbonated altered oceanic crust. This may explain ubiquitous pyroxenitic contributions in many low-δ 26 Mg basaltic suites and has significant implication for deep carbon cycling. Hosted fileessoar.10512814.1.docx available at https://authorea.com/users/563886/articles/610974phantom-recycled-carbonates-and-mantle-pyroxenites-insight-from-the-low-%CE%B426mgintraplate-basaltic-province-across-central-eastern-asia Phantom recycled carbonates and mantle pyroxenites: insight from the low-26 Mg intraplate basaltic province across central-eastern Asia