兴凯地块南部中生代花岗岩年代学、地球化学及成因研究

发布时间：2018-04-28 06:52

本文选题：兴凯地块南部 + 锆石U-Pb测年　；参考：《吉林大学》2015年硕士论文

【摘要】：兴凯地块大部分位于俄罗斯境内，西北部以敦-密断裂为界与佳木斯地块相邻，北部与那丹哈达-比金地体相接（邵济安，1995），处于古亚洲洋构造域和古太平洋构造域的叠加部位，构造演化十分复杂。兴凯地块经历了与松嫩-张广才岭地块拼合、西太平洋俯冲和敦密断裂左行走滑等一系列构造演化，因此兴凯地块南部为研究东北地区区域构造演化提供了一个很好的窗口。兴凯地块南部有较大面积的花岗岩出露，黑龙江地质局（1993）通过地质接触关系将其划分为印支期并统归到东带花岗岩，但缺乏精确的同位素测年数据支持，同时，有关这些花岗岩形成的成因和形成时的构造背景等还没有系统的研究资料。本文选取了兴凯地块南部八楞山岩体、金场沟岩体、天岭桥岩体及风月桥林场岩体进行了岩石学、年代学、地球化学及锆石Hf同位素研究。这些花岗岩主要为二长花岗岩，部分为花岗闪长岩。锆石LA-ICPMS U-Pb测年结果显示，岩性为二长花岗岩的八楞山岩体形成时代为204±2Ma、金场沟岩体形成时代为203±2Ma、天岭桥岩体形成时代为205±2.4Ma；岩性为花岗闪长岩的风月桥林场岩体形成时代分别为202±2.5Ma。整体来看，兴凯地块南部花岗岩形成时代非常接近，由于国际地层表将201.3Ma作为三叠纪和侏罗纪的界限及测年的误差因素，本文将其划分为晚三叠世末期-早侏罗世初期。上述花岗岩地球化学成分上比较富硅，SiO2含量在69.61%~77.27%，其中花岗闪长岩的SiO2含量69.61%~69.98%，二长花岗岩SiO2含量为74.24%~77.27%；弱过铝质，铝饱和指数A/CNK在1~1.1之间；二长花岗岩富钾，K2O/Na2O=1.08~1.33，碱含量为w(K2O)+w（Na2O）=8.02%~8.39%，花岗闪长岩相对富钠，K2O/Na2O=0.58~0.65，碱含量为w(K2O)+w（Na2O）=6.71%~7.83%；二者稀土元素总量差异较大，轻稀土元素较为富集，亏损重稀土元素；富集大离子亲石元素Rb、Th、U、K等，亏损高场强元素Sr、P、Ti等，二长花岗岩有中等至较强的铕负异常（δEu=0.19~0.43），花岗闪长岩的铕负异常则中等偏弱（δEu=0.57~0.82）。综上，兴凯地块南部花岗岩均具有富硅、较富铝，为弱过铝质的特征，二长花岗岩为高钾钙碱性高分异I型花岗岩，，花岗闪长岩为钙碱性I型花岗岩。兴凯地块南部花岗岩锆石Hf同位素数据显示：二长花岗岩和花岗闪长岩的εHf（t）均为正值，为4.39~9.32，二阶段Hf模式年龄比较年轻，为新元古代（0.65~0.96Ga）。结合岩石主量、微量元素特征、区域大地构造演化等方面的研究，认为花岗岩浆来源于太平洋板块向西俯冲背景下新元古代地壳的部分熔融。
[Abstract]:The Xingkai block is mostly located in Russia, bordering the Jiamusi block on the northwestern side of the Dundon-Mi fault, and connecting the northern part with the Nathanhada-Bir gold terrane (Shao Ji'an Jian-1995), which is located in the superimposed part of the paleo-Asian ocean tectonic domain and the paleo-Pacific tectonic domain. The tectonic evolution is very complicated. The Xingkai massif has undergone a series of tectonic evolution, such as the combination with the Songne-Zhangguangcailing block, the subduction of the western Pacific Ocean and the left strike-slip of the Dumi fault. Therefore, the southern part of the Xingkai block provides a good window for the study of the regional tectonic evolution in the northeast region. There is a large area of granite outcrop in the south of the Xingkai block, which was divided into Indosinian and classified to the east by geological contact relationship, but it lacks accurate isotopic dating data. At the same time, There is no systematic study on the genesis and tectonic setting of these granites. In this paper, the Palangangshanite, Jinchanggou, Tianlingqiao and Fengyuqiao Linchang in the southern Xingkai block are selected for petrology, geochronology, geochemistry and zircon HF isotopic studies. These granites are mainly two-feldspar granodiorite and part granodiorite. The zircon LA-ICPMS U-Pb dating results show that the age of formation of the Palangshan, Jinchanggou, Tianlingqiao, Tianlingqiao and Fengyunqiao stands is 204 卤2Ma, 203 卤2Maand 205 卤2.4Marespectively, and that of Fengyunqiao Linchang with granodiorite is 202 卤2.5Ma. On the whole, the formation age of granites in the southern Xingkai block is very close. Because the international stratigraphic table regards 201.3Ma as the boundary of Triassic and Jurassic and the error factor of dating, this paper divides it into late Triassic and early Jurassic. The SiO2 content of granodiorite is 69.611.The SiO2 content of monzogranite is 77.270.The content of SiO2 in granodiorite is 69.61and the content of SiO2 is 77.270.The content of SiO2 is weak peraluminous, and the A/CNK of aluminite is between 11.1. The content of K _ 2O / Na _ 2O is 1.33 and the alkali content is 8.022 ~ 8.39. The granodiorite is relatively rich in sodium K _ 2O / Na _ 2O _ (0.58) 0.65, and the alkali content is w _ (K _ 2O) _ (6.71) ~ (7.83); the total amount of rare earth elements is quite different, the light rare earth element is more enriched, and the heavy rare earth element is depleted; the large ion lithophile element RbTH _ (+) K is enriched. The EU negative anomaly (未 EU _ (0.19) ~ (0.43) in the monzogranite is moderate to stronger than that in the granodiorite (未 EU _ (0.57) 0.82 ~ (2) ~ (-1), and the EU negative anomaly in the granodiorite is moderately weak (未 EU _ (0.57) ~ (0.82). All the granites in the southern Xingkai block are silicon-rich and aluminum-rich, characterized by weak peraluminite. The monzogranites are characterized by high potassium calc-alkaline and high-grade iso-I-type granodiorite, and granodiorite is calc-alkaline I-type granodiorite. The zircon HF isotopic data of granites in the southern Xingkai block show that the 蔚 Hftt of both the monzogranite and granodiorite are positive at 4.390.32, and the age of the two-stage HF model is relatively young, which is the Neoproterozoic age of 0.65U 0.96Gaan. Based on the study of rock principal quantity, trace element characteristics and regional tectonic evolution, it is considered that the magma originated from partial melting of the Neoproterozoic crust in the westward subduction of the Pacific plate.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.121;P597.3

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