Characteristics of isotope geochemistry of deep mantle constraints on metallization in alkali-enriched porphyry systems

Abstract

Numerous well-developed alkali-rich porphyry polymetallic deposits occur in the eastern Jinshajiang-Ailaoshan fracture, western Yunnan. These alkali-rich porphyries of this region are known to contain mantle xenoliths. Pb-Si-Sr-Nd isotope geochemistry suggests that silica-rich mineralizing fluids tend to replace and alter the country rocks and rockbodies, and to be contaminated with crustal rocks, thus forming ore deposits during the generation of alkalic magma. The mineralizing process of silica-rich fluids is essentially a continuation of mantle fluid metasomatism during mineralizing processes in the crust. The action of the mantle fluids is not only an internal constraint to widespread Cenozoic mineralization but also an important geochemical constraint for the formation of large and superlarge deposits in western Yunnan, China.