Geochronological constraints on mantle metasomatism in the petrogenesis of alkalic porphyries and associated mineralization

摘要

There are well-developed alkali-rich porphyry polymetallic deposits in the eastern Jinshajiang-Ailaoshan fault, western Yunnan. The alkali-rich porphyries of this belt are found to contain some deep xenoliths. The studies on the geochronology for deep xenoliths hosted by alkalic porphyries and the mineralizing quartz veins, combined with the evidences from mineral crystallization age (116.0Ma) of mantle fluid metasomatism and the age (51.2Ma) of silicon-rich mineralizing fluid, show that the formation age of deep xenoliths is earlier than those of host alkalic porphyries, and the alkalic porphyry genesis and associated mineralization is basically identical to the ages, of which the mantle fluid processes penetrate to the processes of alkalic magma formation and associated mineralization. It has been suggested that the action of mantle fluids is not only an internal constraint to wide spread of the Cenozoic mineralization but also an important geochemical background for the formation of large and superlarge deposits in western Yunnan, China.