Deep geologic process of Machangqing Cu-Mo-Au ore deposit

Machangqing Cu-Mo-Au ore deposit is a typical deposit related to the Himalayan Epoch alkaline-rich porphyries along the Jinshajiang- Ailaoshan deep fault. From the rock body→ contanct zone→ wall-rocks, mineralization zones can be divided into Mo→Cu→Au, and the mineralization temperature cooled down as high→high-medium→medium-low→low. By the way of the geological age´s studies, we discovered that alkaline-rich porphyries formed at the same time and space as the mineralization. REE, trace elements show that the mineralizing fluid and the magmatic fluid came from enriched mantle. Analyzed with the trans-magmatic mineralization theory, we suggest that the mineralizing fluid is a kind of un-mixing mantle fluid which was contained in the alkaline-rich magma. During the Crystalline diagenetic process, the mantle fluid escaped from the magma varying degrees, and contaminated with the crustal fluid, forming a series mineralization. If the mantle fluid was trapped in the alkaline porphyries, the typical deposit of orthomagmatic metallogenic system, Machangqing porphyry Mo-deposit, formed. When mantle fulid entered into the contact zone between magma body and wall rock or strata next to the contact zone, the typical deposit of the contact-metasomatic metallogenic system, Mach- angqing porphyry Cu (Mo)-deposit formed. Some of the gold deposits in alkaline porphyries were controlled by the faults cutting through the rock body. In this process, the mantle fluid´s properties changed from magma→supercritical fluid→liquid going with the changes of depth, environment and physical and chemical condition. Moving fluid carried activated and enriched ore-material at suitable places. It is the deep geologic process causes crust-mantle contamination and profits to form large and supper-large deposits.