Ore-controlling Characteristics of Devonian Stratum in the Dachang Sn Ore-field, Guangxi (South China)

The Dachang ore-field, which locates in Nandan county of Guangxi province, China, is an important tin-polymetallic mining industry and the typical research base for cassiterite-sulfide deposit in this world. In this mineralization zone, almost all of the deposits are hosted by Devonian stratum, which evolves every group of Devonian. It is undeniable that Devonian stratum is one of the key factor for the formation of Sn polymetallic deposit. The diversity and disparity of Devonian stratum tend to cause the different deformation in the same tectonic stress field and form the favorable space, which is rather important for the migration and filling of the ore fluid. The alternate phenomenon, specially between the limestone and mudstone or shale, make Devonian stratum an excellent reservoir and cover in itself. According to the hydrothermal diagram of Al2O3-SiO2, the sedimentary environment of Devonian stratum is rather complicate, which show that it experienced several times of sea-level changes and turbulence during the formation of Devonian stratum.