Petrogeochemistry and SHRIMP dating of ga'erqin pillow basalt in Duolong, Northern Tibet

Duolong is one of the largest porphyry Cu (Au) ore concentration areas, its dynamic history always being the hot topic for study. Pillow basalt was discovered in Jurassic marine sedimentary strata of Ga'erqin area. Geochronological and geochemical study is helpful to revealing the evolution history of Bangong Co-Nujiang Ocean. Geochemical data show that basalt has low REE (∑REE 38.01 × 10^-6∼63.56 × 10^-6) and no significant differentiation between LREE and HREE. The chondrite-normalized REE patterns are flat, similar to features of E-MORB. SHRIMP dating shows that the age of pillow basalt is (298 ± 11) Ma, coinciding with ages of mafic dykes and basalt in Late Carboniferous to Early Permian strata. All of these phenomena may be the products of large-scale volcanic activity for the opening of Bannu Ocean in early Permian strata.