A Research On Evolution And Different Types For The Skarn Deposits On Southern Margin Of Gangdisi Volcanic-magmatic Arc, Tibet

The volcanic-magma arc belts on southern margin of Gangdisi had ever gone through greatly complicated course of evolvement, especially history of ocean-continent conversion. According to plate tectonics, the course of evolvement of the volcanic-magma arc are divided into fivestages as followed: (1) Early ocean crust subduction (J₂)--commonvolcanic - arc stage; (2) Late ocean crust subduction (J₃-K₁)--peculiarvolcanic - arc(adakite) stage; (3) Post-arc spreading basin stage(J₃-K); (4)Ocean crust subduction completed--begining collision of platestage(70-50Ma); (5) Collision orogenic - quickly uplift - root of mountain delamination stage(20-10Ma).Based on the research of the different geological backgrounds in the course of evolvement on southern margin of Gangdisi volcanic-magmatic arc and different types of the skarn deposit, we find several characteristic types for the skarn deposits on southern margin of Gangdisi volcanic-magmatic arc. For example, there is the volcanic magmatic-hydrothermal transitional type of skarn Cu polymetallic deposit, located in common volcanic-arc which New-Tethys main ocean crust had subducted; a volcanic-hydrothermal type of skarn Cu(Au) deposit related to adakite locates in peculiar volcanic-arc which small ocean basin assocated with New-Tethys main ocean subducted; the strata-bound hot brine metasomatic type of skarn Cu polymetallic deposit exists in post-arc spreading basin, and there is also a magmatic-hydrothermal contact metasomatic type of skarn copper deposit concerned with porphyry. It is clearly show that the skarn deposit within volcanic-magma arc on southern margin of Gangdisi is characteristics of polygenetic, and belongs to category of polygenesis ore deposits.According to time - space distribution of different types for the skarn deposits, they can be divided into two metallogenic belts: the Cu-Au...