The Occurrence And Enrichment Regulation Of Metallic Elements In Black Rock Serials In Lower Cambrian In Zhenping Area, Shanxi

The black rock serials are widely distributed in the world. As many large and superlarge scale ore deposits were discovered, the black rock serials are drawing plenty of attention. So research of the black rock serials and associated deposits is important. The black rock serials are well developed in Sinina and Cambrian in Dabashan area, and some valuable ore deposits have been discovered in some area. So, this paper focus on the black rock serials in Zhenping area, Shanxi, and researchs the occurrence and enrichment regulation of metallic element, willing to offer some new discoveries.The black rock serials in Zhenping area, Shanxi mainly distribut in Yangjiabao Formation and the upper Zhuangzigou Formation. Yangjiabao Formation mainly contains dark-gray thin-thick carbonaceous siliceous rocks, mixied with gray-black thin carbon-bearing siliceous rocks. Zhuangzigou Formation contains carbonaceous slates, carbonaceous siliceous slates, mixed with marlstone and carbon-bearing limestone. Some phosphatic podule and plenty of secondary pyrite are found in black rock serials.Some kinds of methods had been used such as polished section distinguish, scan distinguish, electronic probe and chemical component analysis, in order to analyze the sedimentary facies and provenance and summarize the occurrence and enrichment regulation and mineralization stages.The northern margin of the Yangtze platform including this area was a basin comprising siliceous shale in early Cambrian. The sedimentary pattern belonged to gentle clinothem slope facies. Yangjiabao Formation was deposited in the basin mainly in form of siliceous rocks, while Zhuangzigou Formation was deposited lower which contained more carbon component and mixed with thin limestone or lenses.Chemical component analysis showed that Fe、Zn、Cu、Pb、Mo、Ti、V、Mn、 Cr in black rock serials in Lower Cambrian in this area had different levels of mineralization anomalies, part of samples reached the cutoff grade of associated deposit, but mineralization were uneven. These mineralized elements such as Fe, Zn, Cu, Pb, Ti had a positive correlation, and Fe was less correlated with V, Cr, Mo, U, showing that Fe, Zn, Cu, Pb, Ti had the same material source and enrichment regulation. U in the samples was low and less correlated with other elements, probably for the enrichment of U in black rock series was secondary oxidation.Scan distinguish showed that V was occurred in three forms like clay mineral (roscoelite)、colloidal dispersion (free oxide) and adsorption state (V-Ti oxide aggregate). The V-Ti oxide aggregates were distributed in the rock matrixes by disseminate or like stars in shape. Analysising its crystal-chemical formula basing on the atom ratios showed that its valence wasn’t zero, furtherly showing that the V-Ti oxide was not a mineral crystal. Co, Ni, Mo were mainly occurred in pyrite, nicopyrite and nickel sulfide, and some Cr was occurred in pyrite as isomorphism and little Cu, Pb, Zn, Ti, V, Mn occurred in pyrite. Pyrite was automorphic-hypidiomorphic or in form of framboid, and sphalerite was colloidal, in form of lump. Colloidal sphalerite was occurred in micropore of rocks with size about dozens of microns. W mainly distributed in tungstite (H2WO4), hydrotungstite (H2WO4·H2O) by disseminate, maybe being adsorbed on clay minerals. Ni mainly occurred in sulfide, and Cu, Fe, Ni were mainly formed on the of micropore wall of rocks, depositing from outside to inside. precious metals such as Pt and Pr were some mainl absorbed in colloidal matters, collophane, Fe oxide and hydroxide, hydroxide and other carbonaceous shale.Major elements, trace elements and rare earth elements analysis showed that the black rock series had different kinds of provenances such as terrene, biology, inner ocean basin, submarine volcanoes and hydrothermal sedimentation. Volcanic debris were found in this strata, indicating terrestrial source or submarine volcanoes were existed. Abundant organic materials indicated that biological source was probably. Diversity of provenances and their interaction determined the diversity of metallic elements and their original enrichment.There were two stages of mineralization in black rock serials in this area. In the early stage, sedimentation was dominant and metallogenetic matters were originally enriched, which was characterized by V Fe and Zn synsedimentary colloidal minerals. In the second stage, mineralization has been remoulded. Chalcocite and sphalerite which reached industrial grade were found in hydrothermal quartz and calcite. Reconstruction and recrystallization of wall rocks along the ductile shearing foliations were strong, and elements content was more than tens of times than average.Meanwhile, on the basis of research of the occurrence and enrichment regulation of metallic elements in black rock serials, we optimized some ore-searching targets in the prospective areas. We had optimized Zhuxi-Wangyuhe Zn, Cu, V ore-searching target and Xiaohekou-Miaoping Zn, Cu, V ore-searching target. Carbon-bearing siliceous slates or silicon-bearing carbonaceous slates were prospective rocks, while overlapping of faults, folds and ductile shear zones were prospective structures.