Characteristics of Granites and Their Relationship to Mineralization, Dachang Ore-Field, Guangxi, China

The Dachang ore field is the world famous tin-polymetallic ore district, which locates in the Danchi mineralization belt, Guangxi Zhuang Autonomous Region (or Guangxi province), South China. There are several large and super large deposit in this metallogenic belt, such as Changpo deposit, Tongkeng deposit, Bali-longtoushan deposit, Beixiang tin-polymetallic deposit, Wuxu Sb polymetallic deposit, etc. It is very obvious that these deposits surround the Longxianggai concealed rock, which was considered one of the most important factors for the formation of Dachang tin-polymetallic deposit. So the Longxianggai concealed rock has been the key for solving the deposit genesis. Granite porphyry is the porphyritic texture, the phenocrysts are mainly quartz, feldspar, plagioclase, and the groundmass typically consists of quartz, feldspar and plagioclase. The content of phenocryst is about 15%, yet the content of groundmass is about 85%. By the diagram of Al2O3/(K2O+Na2O+CaO)–SiO2, two samples is the orebearing rock, yet the other two samples is the non-ore rock. It is suggest that only a part of rock can supply the metallogenic material, the other rock isn’t the ore-bearing rock which can’t supply the ore-forming elements. In the Dachang ore district, the magmatic rock isn’t the unique material source. There is some other material source, which is also the important form of material source.