柴达木盆地昆北地区路乐河组/下干柴沟组泥岩地层地球化学特征及古环境意义  

Geochemistry and paleoenvironment significance of Lulehe Formation/Xiaganchaigou Formation located in the north area of Qaidam Basin

作　　者：余平辉 马锦龙 廖建波[1] 李志勇[1] 邸俊 YU Ping-hui;MA Jin-long;LIAO Jian-bo;LI Zhi-yong;DI Jun(Research Institute of Petroleum Exploration&Development-Northwest,Lanzhou 730000,Gansu,China;School of Earth Sciences&Mineral Resources,Lanzhou University,Lanzhou 730000,Gansu,China)

机构地区：[1]中国石油天然气股份有限公司勘探开发研究院西北分院,甘肃兰州730000 [2]兰州大学地质科学与矿产资源学院,甘肃兰州730000

出　　处：《干旱区地理》2020年第3期679-686,共8页Arid Land Geography

基　　金：国家科技重大专项(2017ZX050002-003)资助。

摘　　要：柴达木盆地昆北地区位于柴达木盆地西部南区的昆仑山前缘,该地区构造活动频繁,地层完整,是研究古环境和古气候理想地区。通过采集昆北地区切26井新生界下部泥岩样品,对其进行微量元素分析。结果表明:在地层界线附近,路乐河组Cu、U、Cr、Sr元素含量平均值分别为18.34×10-6、3.24×10-6、141.68×10-6、107.10×10-6,下干柴沟组下段为28.17×10-6、3.35×10-6、192.07×10-6、217.05×10-6。下干柴沟组下段微量元素有明显增大趋势,指示沉积环境发生变化。U与陆源碎屑来源指示元素Th相关性差(R2=0.174 5),表明U主要为自生成因,因此其含量的增加可以指示原始沉积水体还原程度的增强。Cr与U表现为弱相关(R2=0.420 9),表明水体环境的变化对Cr的富集有一定的影响;氧化还原指标U/Th、V/Cr表明研究区古环境为氧化水体沉积环境,U/Th、V/Cr指标在下干柴沟组下段变大表明水体加深,还原性增强。利用Sr/Cu比值变化以及结合化石种属演化等推测地层界线附近古气候经历了干旱-湿润-干旱的旋回变化。Kunbei area of Qaidam Basin is in front of Kunlun Mountains in the southern part of Western Qaidam Basin,Qinghai Province,China.It is adjacent to the Qinghai-Tibet Plateau.Therefore,the tectonic activities are unusually frequent.Furthermore,very thick sedimentary strata have remained from the Cenozoic Era.Therefore,it is an ideal area for studying the paleoenvironment and paleoclimatic evolution.Fresh drilling core samples were collected,and trace elements were detected in the lower Cenozoic mudstone samples of Well Qian 26 in Kunbei area.The changes of trace element contents and their correlations were studied,and the ratio of characteristic elements was further calculated.The results showed that the average contents of Cu,U,Cr,and Sr in the Lulehe Formation were 18.34×10-6,3.24×10-6,141.68×10-6,and 107.10×10-6,respectively,near the stratum boundary,while those in the Lower Ganchaigou Formation were 28.17×10-6,3.35×10-6,192.07×10-6,and 217.05×10-6,respectively.Compared to the Lulehe formation,the content of trace elements in the lower part of the Xiagangchaigou Formation increased obviously,indicating that the sedimentary environment has changed.The correlation between U and Th,the indicator elements of terrigenous clastic rocks,was poor(R 2=0.1745).This indicates that U was mainly autogenic,so the increase in U content may indicate an increase in the degree of reduction of the original sedimentary body.The weak correlation between Cr and U(R 2=0.4209)indicates that the change of water environment had some influence on the enrichment of Cr.The correlation between Cu and U was poor(R 2=0.1231),indicating that the original sedimentary environment had limited influence on the enrichment of Cu,and the increase of its content may be more controlled by the deposition of organic matter and terrigenous debris sources.The correlation between Sr and U was poor(R 2=0.1929),indicating that water environment was not the main factor controlling Sr enrichment.The values of U/Th and V/Cr were 0.19-0.35 and 0.10-0.13,res

关 键 词：柴达木盆地昆北地区 路乐河组/下干柴沟组 地球化学 氧化还原环境 古气候 

分 类 号：P618.13[天文地球—矿床学] P532[天文地球—地质学]