青海省天峻县曲公玛地区古元古代达肯大坂岩群地质特征  

Geological features of the Paleoproterozoic Daken Daban rock group in Qugongma area,Tianjun County,Qinghai Province

作　　者：郑月[1] 李铁笔 苑强[1] 李想[1] ZHENG Yue;LI Tiebi;YUAN Qiang;LI Xiang(Regional Geological and Mineral Resources Survey of Jilin Province,Changchun 130000,Jilin,China)

机构地区：[1]吉林省区域地质矿产调查所,吉林长春130000

出　　处：《吉林地质》2024年第4期16-25,共10页Jilin Geology

摘　　要：天峻县曲公玛地区广泛分布一套变质、变形较强的变质岩系,前人将其划归为中吾农山群土尔根大坂组、果可山组。通过对该套变质地层开展岩石地球化学及地层对比研究,发现其明显区别于典型的中吾农山群岩石特征,根据岩石特征划分为古元古代达肯大坂岩群,划分出片麻岩岩组、片岩岩组、大理岩岩组,通过地质剖面测量,该套地层变质程度为角闪岩相中压相系变质作用,普遍叠加了后期绿片岩相退变质作用,构造变形以线型紧闭褶皱为主;通过岩石地球化学分析,岩石中SiO_(2)含量为(47.29~81.32)×10^(-2),稀土总量∑REE=(71.17~415.69)×10^(-6),δEu值为0.26~1.04之间,L/H值为1.92~10.77,稀土元素标准模式曲线为左高右低,表现为轻稀土富集,重稀土亏损;微量元素Ba、Rb、Sr等大离子亲石元素明显富集,Nb、Ta、Ba、Ti等高场强元素具有明显的负异常,显示出陆源碎屑岩特征,原岩为基性-中酸性火山岩及碎屑岩的一套组合,因此,天峻县曲公玛地区广泛出露的变质地层重新划分为达肯大坂岩群,使柴达木北缘小区的北界北移,与宗务隆小区土尔根大坂组断层接触,为宗务隆晚古生代裂陷槽和欧龙布鲁克微陆块的构造单元划分提供了证据。There is a widely distributed metamorphic rock series with strong deformation in the Qugongma area of Tianjun County,which was previously classified as the Turgen Daban Formation and Guokeshan Formation of the Zhongwunong Mountain Group.Through the study of rock geochemistry and stratigraphic correlation of this metamorphic formation,it was found that it is significantly different from the typical rock characteristics of the Zhongwunong Mountain Group.According to the rock characteristics,it is divided into the Paleoproterozoic Daken Daban rock group,the gneiss rock group,the schist rock group,and the marble rock group.Through geological profile measurement,the metamorphic degree of this formation is the metamorphic process of the amphibolite facies and pressure facies series,which is generally superimposed with the retrograde metamorphic process of the later greenschist facies.The structural deformation is mainly characterized by linear closed folds;Through rock geochemical analysis,the SiO_(2)content in the rock is(47.29-81.32)×10^(-2).The total rare earth element∑REE is(71.17-415.69)×10^(-6),with aδEu value between 0.26-1.04 and an L/H value of 1.92-10.77.The standard mode curve of rare earth elements shows a high left and low right,indicating enrichment of light rare earths and depletion of heavy rare earths;Trace elements such as Ba,Rb,Sr and other large ion lithophile elements are significantly enriched,while high field strength elements such as Nb,Ta,Ba,Ti have obvious negative anomalies,showing characteristics of terrigenous clastic rocks.The original rock is a combination of basic to intermediate acidic volcanic rocks and clastic rocks.Therefore,the metamorphic strata widely exposed in the Qugongma area of Tianjun County have been reclassified as the Daken Daban rock group,causing the northern boundary of the northern margin of the Qaidam Basin to move northward and come into contact with the Turgen Daban Formation fault in the Zongwulong area,providing evidence for the structural unit division of t

关 键 词：达肯大坂岩群 地质特征 曲公玛 青海 

分 类 号：P588.3[天文地球—岩石学]