The geochronologic, geochemical and isotopic data of the Emeishan Large Igneous Province

The link between mantle plumes and the formation of Large Igneous Provinces (LIPs) is well established, although the anatomy of these plumes remains equivocal. Experimental studies and geophysical data suggest that the plume head is more likely to be irregular and asymmetric, rather than an axisymmetric flattened disk-like. The Emeishan large igneous province (ELIP) provides a unique opportunity to test this hypothesis. Pivoting on detailed petrographic, geochronologic, and geochemical evidence from the late Permian basalts in the Sichuan Basin (SCB), and in conjunction with a comprehensive compilation of geologic maps (scale at 1:200,000) and published data from the ELIP, we identified several giant radiating “fingering” structures. Based on the shallower mantle source from the center to margin in the ELIP and relief of the lithosphere-asthenosphere boundary, we propose a new model to explain the evolution of the Emeishan plume periphery, envisaging a “fingering, torn apart and plumelets”. As the plume-lithosphere interacted, the edges of the flattened plume head developed fingering structures. Dragged fingers might have been torn apart into some plumelets, which dispersed and were trapped beneath the thinnest lithosphere relief, and eventually erupted to form small-scale flood basalt in the Outer Zone (OTZ) of the LIP.