张广才岭南段尚志地区花岗岩类成因及其地质意义

发布时间：2018-06-26 11:42

本文选题：黑云母花岗岩 + 地球化学　；参考：《西北大学》2015年硕士论文

【摘要】：张广才岭位于兴蒙造山带的东端,处于古亚洲洋构造域和环太平洋中生代构造域的交汇部位,是我国东北地区地质构造的一个重要的组成单元。印支期花岗岩类岩石在本区分布广泛,特别是发育有巨大体积的花岗岩基。其中,尚志地区一面坡岩体、苇河岩体及长林岩体出露面积较大。本文通过对一面坡、苇河及长林三个岩体系统的岩石学、地球化学、Sr-Nd同位素地球化学、锆石Hf同位素地球化学及锆石U-Pb年代学研究,重点讨论了岩石的成因、成岩物质来源以及本区花岗岩类形成演化的地质意义。研究工作取得以下主要认识：1.锆石U-Pb年代学分析获得一面坡岩体形成年龄为211±4Ma,属于晚三叠世侵位的花岗岩体。岩石具有相对亏损的锆石Hf同位素组成,εHf(t)=+1.75-+13.81；而苇河岩体和长林岩体形成年龄分别是186±2 Ma和186±4 Ma,为同一时期花岗岩体。它们的锆石Hf同位素组成分别为εHf(t)=-1.67-+11.28和εHf(t)=+2.42-+10.43。2.一面坡岩体、苇河岩体及长林岩体主要岩性均为黑云母花岗岩。其中,一面坡岩体相对富硅、富碱,属于高钾钙碱系列,为准铝质/弱过铝质的高分异I型花岗岩类；苇河岩体同样属于高钾钙碱系列,准铝质/弱铝质I型花岗岩类,但主要成岩矿物普通角闪石、斜长石和副矿物榍石及磷灰石等,在岩石形成过程中发生了较低程度的分离结晶作用,因此不属于高分异型花岗岩；而长林岩体则属于钙碱-高钾钙碱系列,为准铝质/弱铝质,没有发生明显分异作用的I型花岗岩类。3.结合张广才岭地区已有的研究成果以及区域地质构造演化历史,本文认为张广才岭南段尚志地区花岗岩分两期,第一期为由于古亚洲洋闭合伸展作用下,使得新增生的下地壳物质发生局部熔融形成岩浆,之后又经过了高程度的分异演化过程,形成的晚三叠世高分异I型花岗岩；第二期形成于早侏罗世,是由于古太平洋俯冲消减,随着区域构造体制由挤压向伸展转换,岩石圈减薄,使得软流圈地幔中的玄武质岩浆上涌,并底侵上覆下地壳,导致先期形成的加厚地壳部分熔融的产物。
[Abstract]:Zhang Guangcailing is located at the eastern end of the Xingmeng orogenic belt and at the intersection of the Paleo-Asian oceanic tectonic domain and the Mesozoic tectonic domain around the Pacific Rim. It is an important constituent unit of the geological structure in Northeast China. Indosinian granitic rocks are widely distributed in this area, especially the granitic bedrock with huge volume. One slope rock mass, Weihe rock body and Changlin rock body in Shangzhi area have a large exposed area. In this paper, the petrology, geochemistry, zircon HF isotope geochemistry and zircon U-Pb chronology of the three rock bodies, including the mianpo, Weihe and Changlin rock bodies, are studied, and the genesis of the rocks is discussed. The source of diagenetic material and the geological significance of granitic formation and evolution in this area. The main findings of the research work are as follows: 1. The zircon U-Pb chronological analysis shows that the formation age of the slope rock is 211 卤4 Ma, which belongs to the late Triassic emplacement granite body. The rocks have relatively depleted zircon HF isotopic composition, 蔚 HF (t) = 1.75- 13.81, while the Weihe and Changlin intrusions are formed at 186 卤2 Ma and 186 卤4 Ma, respectively, and belong to the granite body of the same period. The isotopic compositions of zircon HF are 蔚 HF (t) (-1.67-11.28) and 蔚 HF (t) = 2.42-10.43.2, respectively. The main lithology of the slope, Weihe and Changlin rock bodies are biotite granites. Among them, the mianpo rock body is relatively rich in silicon and alkali, belongs to the high potassium calcium alkali series, quasi aluminum / weak peraluminous high grade iso-I type granite, the Weihe rock body also belongs to the high potassium calcium alkali series, quasi aluminous / weak aluminium I type granite, But the main diagenetic minerals, such as common hornblende, plagioclase and accessory mineral sphene and apatite, have been separated and crystallized to a lesser extent during the formation of rocks, so they are not high grade allotropic granites. The Changlin rock body belongs to the Calcium-Alkali-high-potassium calc-alkali series, which is quasi-aluminous / weakly aluminous, and there is no obvious differentiation of I-type granitoids. 3. Based on the existing research results in Zhangguangcailing area and the history of regional geological tectonic evolution, this paper considers that the Shangzhi granite in the southern section of Zhangguangcaoling is divided into two phases, the first stage is due to the closed extension of the Paleo-Asian Ocean. Resulting in partial melting of the newly accreted lower crust material to form magma, and then the formation of the late Triassic high-grade heterogeneous I-type granite through a high degree of differentiation and evolution, the second stage of which was formed in the early Jurassic, the second stage of which was formed in the early Jurassic. Because of the subduction of the Paleo-Pacific Ocean, the lithosphere thinned as the regional tectonic system changed from compression to extension, which resulted in the upwelling of Black Tortoise magma in the asthenospheric mantle and the underplating of the crust. The product of partial melting of the thickened crust that was formed in advance.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.121

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