Characteristics Of Granites And Discuss On The Genesis Of The Tongcun Porphyry Mo(Cu) Deposit, Kaihua, Zhejiang Province

The Tongcun porphyry-Mo(Cu) deposit, in Kaihua,west of Zhejiang Province, locates in eastern part of Qiantang synclinore,which is a new important metallogenic belt founded by China Geological Survey and the geological prospecting has continuously achieved new breakthrough these years. Tongcun deposit has been in medium-scale. Study of the genesis of this deposit means a lot to realization of metallogenic process and the sources of metallogenic materials, as to provide a guide to the prospecting job. Comprehensive lithology, lithogeochemistry, isotopic geochemistry and dating of ore-bearing porphyry provides an important theoretical and pratical meanings to the disclosure of the process and evolution and discuss on geotectonic setting of granite in this district.On the basis of field work and investigaton, this essay conducts a systematical summary of geologaical characteristics of mine lot and ore body, using various modern testing methods and then systematically analysizes and investigates the granite in Tongcun deposit, finally receiving some achievements as follows: This essay brings forward for the first time that the rock type of Tongcun ore-deposite is metaluminous-peraluminous High-K calc-alkali I-type granite, and the source of magma is mainly from lower crust, with a small dye of mental materials, and formed in continental margin (arc) setting.This essay also puts forward that the diagenesis age of mottled granodiorite and mineralized porphyry is separately about (162.1±3.4 )Ma and (162.6±3.2 )Ma by zircon SHRIMP dating for the first time, which represent the age of granites closely associated with metallogy.After a study on systematical investigation of geologaical characteristics of this deposit,this essay conducts a test on H-O isotopes and S-Pb isotopes of ore and granite,with the results revealing that the metallogenic fluid is mainly magma water, still mixed with little atmospheric water, and metals from the lower crust with little contribution of mental materials.According to the study above, it is concluded that the Tongcun Mo(Cu) deposit was formed in Lower Juro during squeeze-extensional transition stage of the South China. On the basis of field work, the former studies of predecessors and isotope tracing analysis, it’s ensured that old crust basement contributes a great deal to the diagenetic and metallogenic process of Tongcun deposit.