Chigu Tso intrusions in the remnant Comei large igneous province, SE Tibet: implication for Early Cretaceous Kerguelen plume-Eastern Gondwana lithosphere interaction

English Abstract:

Chigu Tso intrusions are found within the Jurassic strata of the remnant Comei large igneous province (LIP), SE Tibet, providing an opportunity to explore how the Early Cretaceous Kerguelen mantle plume interacted with the Eastern Gondwana lithosphere. Chigu Tso intrusions consist of three series: 1) a pyroxenite to low-P₂O₅ gabbro fractional crystallization group; 2) a transitional medium-P₂O₅ diabase-norite-gabbro group; and 3) a high-P₂O₅ gabbro to diorite group. Zircon U-Pb age dating of Chigu Tso intrusions (pyroxenite 130 ± 2 Ma, gabbro 132 ± 1 Ma; Zhu et al., 2009; diorites 132.4 ± 1.0 Ma, 133.7 ± 1.4 Ma; this study) suggest that Chigu Tso intrusions should be part of the magma plumbing system of the remnant Comei LIP. The low ε_Nd(t) value of the pyroxenite (-1.8) is similar to SCLM-derived ultramafic rocks in Sylhet Traps (pyroxenite, -0.1 to -4.2; lamproite, -2.4 to -6.4; and kimberlites,-2.6 to -3.2; Ghatak et al., 2013). Isotope work in progress will resolve between the models of fractional crystallization of high-P₂O₅ gabbro and fractional melting of pyroxenite for the petrogenesis of the diorites. The presence of SCLM-derived ultramafic rocks and a crustal signature in the remnant Comei LIP, Bunbury basalts, Rajmahal-Sylhet traps, and Southern Kerguelen Plateau, suggest that the Eastern Gondwana lithosphere played an important role in the origin of this portion of Kerguelen plume-related magmatism.