Sedimentary Geochemistry And Ore-bearing Potentiality Of The Early Cambrian Black Rock Series In Shitai County, Anhui Province

The Early Cambrian black rock series have been paid attention by home and overseas scholars because of its relationship with oceanic anoxic event of the Early Cambrian black series and higher concentration of heavy metal. Supported by the"1:50000 Nancun and Dingxiang region ore resources investigation in Shitai county of Anhui province" from Department of Land and Resources Anhui Province, studies on the sedimentary and trace element geochemistry of the Early Cambria black rock series in Shitai area were carried out, evolution history and implication for the Early Cambrian sediment of Jiangnan structure belt as well. Main conclusions are present, as follows:(1) The depth of stratigraphic sections consisting of the Early Cambrian Hetang Formation and the Huangboling Formation locating at side of Jiangnan structure belt were field measued. From lower to upper layer of Hetang Formation, the dominated petrology is siliceous rocks/siliceous shales, siliceous-bearing carbonaceous shales, carbonaceous shales, shales, carbonaceous- bearing shales, calcic mudstones. The Huangboling Formation has identical rock assemblages as the Hetang Formation. But the 300 m depth of Hetang Formation is half of the 600 m depth of Huangboling Formation which suggests sedimentary environment diversities(2) The carbonaceous shales with higher content trace element compared with other layers of sedimentary setions may be multiple metals enchancement layer. This maybe an ore parent. And the trace element geochemstry characteristics show that the Early Cambrian black rock series were formed from hydrothermal fluid instead of standard ocean water. From early stage to late stage of the Early Cambrian, sedimentary environment changed from deoxidized condition to self-deoxidized to oxidized condition. Sedimentary environment evolutio may be sound relationship with rising and falling of sea level in the global scope. These sedimentary environment transition are supported by PAAS standarded REE patterns of rocks and Ce abnormity.(3) The Hetang Formation locates at south side of Jiangnan fault zone, the opposition side of Huangboling Formation. The differences of petrology, sedimentary and thickness beween the Hetang Fromation and Huangboling Formation have proved that the fault zone had fromed in Early Cambrian. The hydrothermal sedimentary characteristics recorded by the trace element indicate that the syngenetic fault control and affect the sedimentary environment of blace rock series at the both sides of Jiangnan deep fault zone.