Picritic porphyrites and associated basalts from the remnant Comei Large Igneous Province in SE Tibet: records of mantle‐plume activity

Abstract

AbstractPicritic porphyrites and associated basalts are found in Lower Cretaceous slates within the recently identified remnant Comei Large Igneous Province, SE Tibet. They provide an opportunity to explore the mantle potential temperature of this large igneous province and the genetic correlation between the picritic porphyrites and associated basalts. The high levels of MgO and CaO in olivine phenocrysts from the picritic porphyrites indicate that these olivines crystallized from high‐Mg magmas. By deducting the accumulated olivines, we determined a parental magma MgO content for the picritic porphyrites of c. 20% MgO, corresponding to a mantle potential temperature of >1550 °C for the parental magma. Such a high temperature provides solid evidence for a mantle‐plume origin of the remnant Comei Large Igneous Province. Parallel trace‐element patterns and similar εNd (T) and (177Os/178Os)T values in the picritic porphyrites and associated basalts suggest a common hot mantle source region for their generation.