PETROGENESIS OF CU-BEARING PORPHYRY ASSOCIATED WITH CONTINENT-CONTINENT COLLISIONAL SETTING: EVIDENCE FROM THE YULONG PORPHYRY CU ORE-BELT, EAST TIBET

Abstract

Giant porphyry Cu deposits were formed not only in continental- and island-arcs, but also in continent-continent collisional setting. However, the petrogenesis of ore-bearing porphyry associated with the continent-continent collisional setting remains hotly controversial. This paper takes the Yulong porphyry Cu ore-belt, east Tibet as example, and presented detailed petrographical, element geochemical and Sr-Nd-Pb-Hf isotopic data for these ore-bearing porphyries. As a result, the ore-bearing porphyries are shoshonitic and show some affinities with the adakite, and were derived directly by low degree partial melting of the phlogopite-garnet clinopyroxenite that was produced by the slab-derived silicate-carbonate fluid metasomatism and by addition of small amounts of slab-derived melt hybridization at Mesoproterozoic age in an lherzolitic lithosphere at a depth of > 100km. A regional-scale strike-slip fault system caused by the India-Asia continental collision triggered melting of the metasomatized lithospheric mantle. This is important to further understand the source and origin of diverse granites and the geneses of porphyry deposits especially in continental collision settings.