Composition And Evolution Characteristics Of Organic Matter Of The Lower Cambrian Black Shale In Guizhou

With the decrease of min eral r esources reserves,co mp rehensive utilization of resources beco me mor e and more imp ortant to be researched.Black shale resources ar e abund antal in Guizhou Province,and it has a good p otential for develop ment and utilization.The research on mineral comp osition,chemical co mp osition and organic matter of black shale can p rovide basic research data for the comp rehensive develop ment and utilization of resources.This p ap er took Guizhou Zuny i Fenggan g,Qiandon gnan Cen gon g,B ijie Zhijin Niutitang Formation of the lower Cambrian black shale as the research object.Based on data collection and analy sis,field investigation,samp le collection,samp le test,results analy sis and so on were carr ied out.The co mp osition and organic matter of black shales were sy stematically studied and discussed,and the comp rehensive utilization of black shale were dev elop ed.Research shows:The main minerals of the Niutitang Formation black shale in Guizhouare were quartz and clay minerals.Secondary minerals were py rite,feldsp ar and dolomite etc.The mean value of qu artz content was45.23%.The average content of clay minerals which were mainly illite was 34.87%,while contained illite mixed lay er,kaolinite,chlorite etc.The chemical comp osition of black shale was mainly Si O₂,between 74.87%and54.32%.The content of Al₂O₃ ranked second.Trace elements as,M o,Pb and W had different degrees of accumu lation.The enrichment factor of M o was the highest,which was 44.5 times.Trace element analy sis showed that the black shale was formed in the ano xic env ironment,and was influen ced by the hot water dep osition.The analy sis of char acteristics of rar e earth elements showed that Ce and Eu have found negative anomalies.The black shale formed in sed imentary environment of the continental margin.The main source of material may be terrigenous.Rar e earth elements of black shale h ad the light enrich ment and heavy rare earth relative loss characteristics.The origin al or ganic carbon content of black shale in the study area was between 3.024%and 8.22%,and organic carbon in the adjacent ar ea was fro m 5%to 6.5%.The p otential hy drocarbon gen eration amount was0.0046?0.1462 mg/g,and the hy drocarbon gener ation p otential was relatively little.The kerogen ty p e in the study area was mainly of typ e I.The vitrinite reflectance(Ro)r an ged from 2.47%to 2.91%,the average was 2.628%.The high est p eak temp erature(Tmax)of organic matter py roly sis was 564.2 degrees,and the organic matter evolution was in the high-over mature stage.The content of M o,V,Ni element in the black shale had linear correlation with the organic carbon content,and the content increased with the increase of organic carbon content.The M ulti-metal lay er near the bottom of the black shale in Zhijin contains M o,V,Ni,Ag and U and other metal elements,the content of Mo,Ni achieved industrial grade.Co lloid al p hosp hurany lite existed in the contactin g zone of the bott om black shale and p hosp horus ore,its value shall b e conf irmed by further work.Illite was the main clay min eral in black shale,the content of K₂O was about 5.09%,named as p otassium shale.Potassium could be extracted from black shale to make p otassium comp ound fertilizer.The chemical comp osition of black shale was basically in accordance with the firing of ceramic ceramic standard,which can b e used for f irin g ceramic.At the same time,it can also b e used to mak e glass ceramics.Organic matter has an imp ortant influence on shale gas formation.The mean valu e of organic carbon content of black shale in the study area was 5.63%,which was benef icial to increase the content of shale gas.However,the average content of hy drocarbon gen eratin g p otential was 0.0537 mg/g,and the hy drocarbon gen eratin g p otential was relatively little.The reason may be that the generation and exp ulsion efficien cy of black shale was lower.The typ e of organic matter was dominated by I typ e.The degree of thermal evolution was the high-over mature stage.Low activation ener gy of kerogen basic p y rolysised comp letely during the early stage of or ganic matter evolution,the hy drocarbon p otential of the remained stable kero gen was relatively low,which was not conduciv e to the formation of shale gas.