【摘要】 巢湖平顶山北坡剖面下三叠统岩石化学成分分析表明,SiO2、Al2O3、Fe2O3、FeO、MgO、Na2O、K2O、TiO2、P2O5及微量元素Ba、V、Be、Nb、Zn、Cu、Ni、Co、Pb主要富集在下三叠统格里斯巴赫(Griesbachian)、迪纳(Dienerian)及斯密斯(Smithian)亚阶中,形成了8次显著的正异常,异常的强度、规模由下向上呈下降趋势;微量元素Sr和常量元素CaO主要富集在下三叠统上部斯帕斯(Spathian)亚阶中,其含量由下向上呈逐渐增加趋势.前者含量与碳酸盐岩的碳同位素组成(δ13C)呈负相关关系,后者含量与碳酸盐岩的碳同位素组成(δ13C)呈正相关关系.海相碳酸盐岩碳同位素组成(δ13C)指示初始生产力大小,同时亦是海洋生态环境改善的指示标志;负相关表明环境恶化、生物萧条,正相关表明环境适宜、生物繁盛.据常量元素和微量元素分布异常特点在下三叠统地层中识别出8次地质事件,其规模及影响强度由早到晚逐渐变小及减弱;晚二叠世末期及早三叠世初期的火山喷发将各种有害元素大量输向海洋,导致海水中粘土矿物、微量元素含量异常增高,海洋生态环境恶化.随着时间推移,火山活动逐渐平息,海洋中各种有害组分逐渐排除,海水得到净化,生态环境渐渐恢复.更多还原

【Abstract】 Results of chemical analysis on rock samples collected from the north Pingdingshan Section,Chaohu,Anhui Province,Southeastern China,suggest that main elements of SiO2,Al2O3,Fe2O3,FeO,MgO,Na2O,K2O,TiO2,P2O5 and trace elements of Ba,V,Be,Nb,Zn,Cu,Ni,Co,Pb are rich in the Griesbachian,the Dienerian,as well as in the Smithian Subseries in the Lower Triassic.Eight distinct positive anomalies have been identified in the Lower Triassic on the basis of results of main and trace elements mentioned above.In ascending order,strength,size of anomalies and content of these elements in the Lower Triassic decrease gradually.In contrast to these elements,Sr and CaO are relatively concentrated in the Spathian subseries in the uppermost part of the Lower Triassic.Furthermore,trace element of Sr and main element of CaO enrich gradually up the north Pindingshan Section.Content of the former elements has negative correlation with δ13C values of carbonate,while the content of the later elements is positively related with δ13C values of carbonate.Commonly,δ13C value is used as an indicator of marine primary production and also used as an indicator to define restoration of marine ecological environment.Negative correlation between element contents and δ13C values indicates that the deteriorating marine environment is the tremendous disaster to the Early Triassic marine fauna in the Lower Yangtze region,while the positive correlation between element contents and δ13C values present that the feasible marine environment to the Early Triassic fauna.Eight marine geo-events have been identified in the Early Triassic based on the pronounced anomalies of trace elements and main elements.Strength of these events became weaker and weaker from the early Early Triassic to the late Early Triassic.A plenty of trace elements from the terrestrial volcano eruptions fluxed into the sea during the Late Permian and the Early Triassic,resulting in high content of argillaceous minerals and high grade of trace elements which led to paleocean environment deteriorating.Marine environment recovered as soon as the superfluous trace elements and argillaceous minerals deposited on the sea floor after volcano activities ceased.更多还原