阿尔泰南缘吉木乃地区下二叠统沉积环境的地球化学判别  

Geochemical Discrimination of Early Permian Sedimentary Environment in Jimunai Area,Southern Altai

作　　者：冯杨伟 FENG Yangwei(State Key Laboratory for Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China;Centre for Orogenic Belt Geology,CGS,Xi'an 710054,Shaanxi,China;Shandong Provincial Key Laboratory of Depositional Mineralization&Sedimentary Mineral,Shandong University of Science and Technology,Qingdao 266590,Shandong,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室 [2]东华理工大学地球科学学院 [3]中国地质调查局造山带地质研究中心 [4]山东科技大学山东省沉积成矿作用与沉积矿产重点实验室

出　　处：《西北地质》2019年第4期98-107,共10页Northwestern Geology

基　　金：东华理工大学博士科研启动基金项目“煤系石墨矿床成矿富集机理研究”;山东省沉积成矿作用与沉积矿产重点实验室开放基金（DMSM2019008）;国家自然科学青年基金项目（41502081）共同资助

摘　　要：选用对沉积环境反映比较敏感的元素,对吉木乃地区珠万喀腊剖面早二叠世卡拉岗组14件泥岩样品开展主量元素、微量元素、稀土元素分析,分析研究区地层中微量元素含量及其比值与沉积介质环境之间的对应关系,进而探讨吉木乃地区早二叠世沉积期的湖盆气候条件、盐度、氧化还原条件等沉积环境特征。研究结果表明,古盐度指标w(B)、[m(Sr)/m(Ba)]和[m(B)/m(Ga)]平均值分别为51.32×10^-6、0.29%和2.42%,共同反映出吉木乃地区早二叠世为淡水环境,期间存在多个水体咸淡变化的次级旋回;氧化-还原条件指标V/(V+Ni)、Th/U和&U平均分别为0.82%、3.62%和0.92%,揭示出吉木乃地区下二叠统为缺氧环境下的沉积;经北美页岩标准化后发现泥岩中稀土元素比北美页岩的含量低,推测当时沉积应为化学风化作用较弱的较干燥气候,同时水体可能较安静。The elements that are sensitive to the depositional environment have been selected for analyzing the major elements,trace elements and rare earth elements of 14 dark mudstone samples from early Permian Kalagang Formation at Zhuwankala section in Jimunai area.And then,the relationship between the contents and ratios of the strata's trace elements and the related sedimentary environment in the studying area has been analyzed.Finally,the sedimentary environment characteristics of Jimunai area in Early Permian,such as lake-basin climatic conditions,salinity,redox conditions,have been discussed.The results show that the Paleo-salinity indexes such as w(B),[m(Sr)/m(Ba)]and[m(B)/m(Ga)]are 51.32×10^-6,0.29%and 2.42%,respectively,indicating a freshwater sedimentary environment in Jimunai area during Early Permian,with multiple secondary cycles of brackish water.The V/(V+Ni),Th/U and&U values are 0.82%,3.62%and 0.92%,respectively,which suggest that the Jimunai area developed under an anaerobic environment during Early Permian.After standardizing by North America shale,it's found that the REE contents in mudstone is lower than North America shale,and it's speculated that the paleoclimatic environment was dry climate sedimentary condition with weak chemical weathering and calm water.

关 键 词：吉木乃地区 卡拉岗组 古盐度 氧化-还原条件 下二叠统 

分 类 号：P618.13[天文地球—矿床学]