Intracontinental rift-related magmatism in the eastern Emeishan Large Igneous Province traced by zircon oxygen isotopes

Abstract

Rift systems associated with mantle plume activity are potential conduits for the transfer of voluminous magmas and fluids, and also contribute to ore formation in magmatic and hydrothermal systems. The Panxi (Panzhihua-Xichang) rift within the ~260 Ma Emeishan Large Igneous Province (LIP) is a typical case where world-class Fe-Ti-V oxide and relatively small Cu-Ni sulfide deposits are hosted in mafic-ultramafic intrusions. However, whether similar rifts exist in other parts of the Emeishan LIP remains unclear. Here we carry out an integrated SIMS analysis of zircon U-Pb-O isotopes from volcanic tuffs from the eastern part of the Emeishan LIP. Our results indicate that magmatic zircons with U-Pb ages coeval with the timing of the Emeishan magmatism have δ18O values lower than that of mantle, and as low as +2.94‰. In conjunction with previously reported evidence from sedimentary units, we propose that the silicic magmas with relatively low δ18O values in the eastern Emeishan LIP were derived from crustal recycling of hydrothermally altered rocks within an extensional setting associated with mantle plume activity. Our results combined with previous data suggest that the rifts triggered by the mantle plume activity in the eastern Emeishan LIP may be the potential locales for the exploration of magmatic sulfide deposits.