Variety and complexity of the Late-Permian Emeishan basalts: Reappraisal of plume-lithosphere interaction processes

New petrographic, major element, trace element and isotopic data (Sr and Nd) for 17 Emeishan basalts from the Lijiang-Shangri-La area of SW China are integrated with published data comprising similar to 300 mafic rocks from the Emeishan large igneous province (LIP) to create a comprehensive model for this LIP event We find large compositional variations in the Emeishan basalts that were generated by melting of heterogeneous mantle sources and interaction between the Emeishan plume and lithosphere The Emeishan basalts can be generally grouped into high-Ti and low-Ti classes, but our samples argue that a more detailed classification scheme is required, and the two classes are better separated by the line TiO2= 0.08MgO +291 We suggest that high-Ti basalts are products of deep melting plume head material similar to oceanic island basalts (OIB5). with little lithospheric overprint. The low-Ti basalts. alternatively, were generated from shallower melting of the plume head and have significant lithospheric inputs via either direct crustal contamination or by inherited subduction components in the lithosphere The Vietnam picrites and low-Ti basalts are distinct from other ELIP samples, and probably derived from a much more depleted mantle component. either intrinsic to the mantle plume itself or entrained in the plume head during its ascent We infer that the thermal structure, spatially distributed compositional heterogeneities within the plume head, and varying degrees of interaction with overlying lithosphere and crust control the composition of lavas from a given locality. (C) 2010 Elsevier B.V. All rights reserved.