新疆阿勒泰喀纳斯群变质岩地球化学特征及原岩恢复

发布时间：2017-12-28 12:18

本文关键词：新疆阿勒泰喀纳斯群变质岩地球化学特征及原岩恢复　出处：《新疆大学》2017年硕士论文　论文类型：学位论文

【摘要】：阿勒泰造山带是中亚造山带的重要组成部分,其是否存在前寒武纪大陆地壳基底以及造山带中深变质岩石的时代以及变质岩的成因及物源方面一直存在争议。本文以阿勒泰喀纳斯岩群片岩、片麻岩为研究对象,通过地球化学研究表明,该套变质岩的SiO2含量在58.76%~63.28%之间,里特曼指数均小于1,属于钙碱性系列,主量元素K-A关系落入泥质粉砂岩亚区,说明研究区片岩为副变质岩,原岩主要为泥质沉积岩,个别为砂质沉积岩。大离子亲石元素Rb,Th,Ce,Zr和Hf等呈较明显的富集,高场强元素Ta,Nb,P,Ti等大多为亏损状态,具有明显的Eu负异常,反映出与岛弧岩浆活动特征,认为该套地层处于岩浆型被动陆缘。源区物质主要为中-酸性大陆岛弧火山岩,并夹杂少量其他碎屑物。该套变质岩中的La、Ce、∑REE、δEu、LREE/HREE的值显示其原岩主体形成于大陆岛弧背景。LA-ICP-MS锆石U-Pb定年结果表明其锆石主要为岩浆锆石,206Pb/238U年龄集中在为500~530 Ma,其中31个点构成的谐和年龄为(500±3Ma)Ma,从而判定其为该套地层的下限年龄,另有一组年龄(931.2±9.2Ma)为前寒武世古老锆石的年龄信息,间接证明阿勒泰造山带存在前寒武纪大陆地壳基底,也基本上可以确定喀纳斯群形成于寒武世之后的观点。以上地球化学特征表明,喀纳斯群变质岩很可能沉积于活动大陆边缘的大陆岛弧相关环境,推测喀纳斯群发生沉积作用与变质作用的时间在550±18Ma至430Ma之间,结合前人的观点和地层间的接触关系,认为喀纳斯群为早古生代地层。
[Abstract]:The Aletai orogenic belt is an important part of the Central Asian orogenic belt, the existence of Precambrian orogenic belt and continental crust basement metamorphic rocks and metamorphic rocks in the era of the geneses and sources has been controversial. This paper takes Aletai Kanas schist and gneiss rock group as the research object, through the study of geochemistry indicates that the content of SiO2, the metamorphic rocks are between 58.76%~63.28%, the Litman index is less than 1, belong to the calc alkaline series. The relationship between the main elements of the K-A amount in siltite sub region, shows that the study area is metamorphic schist, original rocks argillaceous sedimentary rocks, individual arenaceous sedimentary rocks. The large ion affinity elements Rb, Th, Ce, Zr and Hf are enriched obviously. The high field strength elements Ta, Nb, P, Ti and so on are mostly depleted, showing obvious negative Eu anomalies, reflecting the characteristics of magmatic activity along the island arc, and think that the strata are in the magmatic passive continental margin. The source area is mainly medium - acid continental island arc volcanic rocks, with a small number of other debris. The values of La, Ce, sigma REE, Delta Eu and LREE/HREE in the metamorphic rocks show that the main rocks are formed in the continental island arc background. LA-ICP-MS zircon U-Pb dating results indicate that the magmatic zircon zircon mainly concentrated in the age of 500~530, 206Pb/238U Ma, in which 31 points of the Concordia age (500 + 3Ma) Ma, so as to determine which is the strata of the lower age, a group of age (931.2 + 9.2Ma) for pre Cambrian ancient the zircon age information, indirect evidence of the Aletai orogenic belt in Precambrian continental crust basement, also basically can determine the formation of the Kanas group in the world after the Cambrian view. The above shows that the geochemical characteristics of continental arc environment probably sedimentary metamorphic rocks of the Kanas group in the active continental margin, suggesting that the time Kanas group occurred sedimentation and metamorphism between 550 + 18Ma to 430Ma, with the previous point of view and the formation of the contact relationship, that the Kanas group of Early Paleozoic strata.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.3

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