Research On The Black Rock Series Of Cambrian Niutitang Formation In Qianxi Nayong, Wangchen

Black Rock Series has always been one of the focus of domestic and foreignscientists. To sedimentology and geochemistry as the means of research, mainly basedon the element geochemistry and oganic geochemistry analysis, this paper studies theblack rock series of Cambrian Niutitang Formation in Qianxi Nayong. We discussesthe sedimentary environment of the black rock series, the organic parent material, theorganic matter type and maturity, preliminary discussion of the black rock series"metal" cause of formation. The main conclusions are as following:(1) According to the study area of rock features and paleontology, the NiutitangFormation identified as neritic sedimentary environment. Black rock series iscomposed of carbonaceous shale, siliceous shale, chert, phosphate rock, limestone,rich in nickel, molybdenum and other metals. The rock color is generally deep, asdark gray and black. It contains mostly black shale.(2) Based on element geochemical characteristics analysis，we can draw theconclusion that the sedimentary environment is low-energy anoxic reducingenvironment of the black rock series in the Early Cambrian Niutitang Formation inQianxi Nayong. In this environment, the preservation of organic matter is good, andthe metal-rich sediments is likely to be formated under the influence of hydrothermalactivity.(3) Based on the determination of organic carbon were analyzed, and accordingto the actual content of organic carbon by restoring the obtained organic matterabundance, we conclude that the study area of high organic carbon content, highorganic matter abundance, as a set of good hydrocarbon source rock. We indicatedthat sedimentary environment of the set of black rock series is an anoxic reducingsedimentary environment.(4) We extracted plenty of normal paraffin hydrocarbons, isoprenoid, terpenoid and steride from the samples of the black rock series。Through to these biomarkerparameters analysis, we found that in the study area are rich in organic matter, itsparent material for marine input, mainly for algae and bacteria; organic matterpreserved, reaction of the sedimentary environment for low-energy residenceenvironment; organic matter maturity is high, close to or reached oil generationthreshold.In the research area of the black rock series of Cambrian Niutitang Formationcontains carbonaceous shale, siliceous shale, chert and limestone, phosphate rock, itsformation have a closely connection with anoxic event correlation of the SinianCambrian. Large-scale transgression, mentioned a lot of terrigenous clastic, algae andother microorganisms multiply, black rock series is provided by forming a favorablesedimentary environmental hypoxia. High organic matter abundance, its parentmaterial derived from algae, the organic matter in shallow water reducingenvironment well preserved. In the geological evolution of the process, a higherdegree of thermal evolution of organic matter, Generally has reached the oil thresholdor high maturity stage. Through the organic qualitative evaluation, we conclude thatthe black rock series of Cambrian Niutitang Formation in Qianxi Nayong is a set ofgood hydrocarbon source rock.