今天是2018年12月11日

北阿尔金野马泉二长花岗岩成因及其构造意义

DOI:10.3799/dqkx.2018.719

作者:郑坤,吴才来,郜源红,郭文峰,陈红杰,吴迪,高栋

联系地址:中国地质科学院地质研究所,北京 100037

摘要:野马泉二长花岗岩为北阿尔金地区出露面积最大的花岗岩体,为探讨其成因、形成环境及其与北阿尔金区域构造演化的关系,对其进行了岩石学、地球化学、锆石U-Pb年代学及Hf同位素等方面的研究.研究结果表明,野马泉岩体为中-粗粒等粒或似斑状二长花岗岩,岩体侵位时代为450~453 Ma.岩石具较高的Na2O/K2O比值为1.72~2.29,铝饱和指数A/CNK为0.99~1.10,P2O5与SiO2含量呈负相关,具Ⅰ型花岗岩特征.轻稀土富集而重稀土亏损,较弱的负Eu异常,微量元素特征显示富集Rb、Ba、Th、U、K 等元素,相对亏损Nb、Ta、P、Ti 等元素.锆石ε Hf( t )值为5.52~10.75,二阶段模式年龄t DM2为0.75~1.09 Ga,其源岩可能主要是0.75~1.09 Ga的新生地壳(基性岩).结合区域构造背景,野马泉二长花岗岩体可能形成于同碰撞-后碰撞环境,为造山带根部基性岩石部分熔融形成.

关键字:二长花岗岩;地球化学;U-Pb年代学;Hf同位素特征;岩石成因;北阿尔金

Petrogenesis and Tectonic Implications of Yemaquan Monzogranite from North Altyn

Author:Zheng Kun, Wu Cailai, Gao Yuanhong, Guo Wenfeng, Chen Hongjie, Wu Di, Gao Dong

Author Address:Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China

Abstract:Yemaquan monzogranite pluton is the largest outcrop in North Altyn, with a medium-coarse grain and porphyritic texture. This paper aims to discuss the genesis and diagenesis environment of the monzogranite, and the tectonic evolution of North Altyn. Thus, it is necessary to study petrology, geochemistry, zircon U-Pb chronology and Hf isotope of the pluton. The zircon U-Pb age data suggest that the monzogranite was generated at 450-453 Ma. The rock shows significant features of I-type granite with high ratio of Na2O/K2O (1.72-2.29), aluminum saturation index (A/CNK=0.99-1.10) and negative correlation between P2O5 % and SiO2%. The REE pattern shows depletion of HREE, relative enrichment of LREE, and slightly negative Eu anomaly. In the primitive mantle-normalized trace-element diagram, the rock shows strong enrichment of Rb, Ba, Th, U, K and depletion of Nb, Ta, P, Ti. The values of ε Hf( t ) range in 5.52-10.75. The two-stage model ages (t DM2) vary from 0.75 to 1.09 Ga. These characteristics indicate that the source rock was formed from the juvenile crust (basites). Considering the regional tectonic setting, it is concluded that the monzogranite was generated by partial melting of the basites at the root of the orogenic belt in the syn-collision to post-collision environment.

Keyword:monzogranite; geochemistry; U-Pb chronology; Hf isotopic characteristics; petrogenesis; North Altyn

 

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作者简介:郑坤(1989-),男,博士,矿物学、岩石学、矿床学专业.ORCID: 0000-0003-4935-2157. E-mail: zhengkun163mail@163.com

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