Character and post-ore changes, modifications and preservation of Cenozoic alkali-rich porphyry gold metallogenic system in western Yunnan, China
滇西富碱斑岩型金成矿系统特征与变化保存

The Cenozoic alkali-rich porphyry type gold-polymetallic deposits are not only closely related to the Himalayan alkali-rich porphyries in space and time, but also suffered strongly secondary enrichment, so that is the best natural laboratory of study metallogenic post-ore changes and preservation. The ore-bearing porphyry is characterized by a set of alkali-rich K2O+Na2O>8%) rock that from basic to intermediate-acid, came from the enriched mantle that formed in the tectonic evolution process of Tethys, and suffered partial melting when up to boundary between crust and mantle in the Early Cenozoic. The main ore-bearing porphyry formed in 33~38Ma, the large-scale mineralization concentrated in 34±2Ma; both of them are related to crust-mantle exchange and structural deformation that in the process of tectonic dynamic system transformation, and also possible controlled by the eastward escape of Qinghai-Tibet Plateau and pulsating uplift of asthenosphere. Later, the India plate changed into clockwise rotation from previous counterclockwise rotation; the oblique reverse rotation and rollback subduction of India Plate led to lithosphere extension, multiple sinistral or right-lateral strike-slip movement, strongly tectonic uplift, emplacement of high-K magmatic that come from the depression melting of depleted mantle, large-scale fluid activities, and regional laterization. The ore-forming system suffered strongly post-ore changes and deformation, went through multiple metallogenic, and characteristiced by obvious diachronism. The supergene gold minerlization started after the formation of gold deposits.