欢迎访问现代地质!

现代地质 ›› 2025, Vol. 39 ›› Issue (04): 995-1015.DOI: 10.19657/j.geoscience.1000-8527.2024.027

• 矿床学与岩石学 • 上一篇    下一篇

内蒙古集宁地区小大青山中生代花岗岩岩石特征及其成因意义

武将伟1(), 胡浩2, 张富臣3, 牛毅4, 周志广2,*(), 张达2   

  1. 1.五矿勘查开发有限公司,北京 100010
    2.中国地质大学(北京) 地球科学与资源学院,北京 100083
    3.中水北方勘测设计研究有限公司,天津 300222
    4.天津市地质环境监测总站,天津 300191
  • 出版日期:2025-08-10 发布日期:2025-08-27
  • 通信作者: *周志广,男,教授,1967年出生,主要从事构造地质学教学和区域构造研究工作。Email:zhouzhg@cugb.edu.cn
  • 作者简介:武将伟,男,高级工程师,1983年出生,主要从事地质矿产勘查与区域构造研究工作。Email:wujw@minmetals.com
  • 基金资助:
    国家自然科学基金项目(4227020154)

Petrological Characteristics and Petrogenetic Significance of Mesozoic Xiaodaqingshan Granite in Jining Area, Inner Mongolia

WU Jiangwei1(), HU Hao2, ZHANG Fuchen3, NIU Yi4, ZHOU Zhiguang2,*(), ZHANG Da2   

  1. 1. Minmetals Exploration & Development Co.,Ltd.,Beijing 100010,China
    2. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    3. China Water Resources Beifang Investigation, Design and Research Co.,Ltd.,Tianjin 300222, China
    4. Tianjin Central Station of Geological Environmental Monitoring, Tianjin 300191, China
  • Published:2025-08-10 Online:2025-08-27

摘要:

华北克拉通北缘中段中生代岩浆岩岩石特征复杂,在花岗岩形成上存在认识分歧,制约了成岩动力学的深入认识。本文选取该构造带的内蒙古中生代小大青山花岗岩体为研究对象,开展了岩相学、锆石U-Pb定年、全岩元素组成和Sr-Nd-Pb同位素组成等研究,阐释岩浆岩成因和源区属性,并进一步探讨研究区中生代构造动力学环境。研究结果表明,二长花岗岩锆石206Pb/238U加权平均年龄为(135.4±1.2) Ma,代表其寄主的花岗岩类形成于早白垩世。岩石具有高硅(73.37%~77.21%)、富碱(5.93%~8.78%)、高铝饱和指数(1.02~1.32)的特征,属于过铝质高钾钙碱性系列;富集大离子亲石元素Rb、K和高场强元素Th、U,亏损Nb、Ba、Sr、Ti和P;富集轻稀土元素而亏损Eu元素;低(87Sr/86Sr)i值(0.7094~0.7391)、高负εNd(t)值(-15.37~-16.19)、206Pb/204Pb比值为17.158~17.365、207Pb/204Pb比值为 15.437~15.442、208Pb/204Pb比值为 37.881~38.082。地球化学特征综合反映小大青山花岗岩属于高分异I型花岗岩,岩石主要系下地壳物质部分熔融的产物。结合区域地质证据,认为内蒙古集宁地区小大青山花岗岩形成于后造山阶段,其形成可能受蒙古—鄂霍次克洋盆闭合和古太平洋板块俯冲的联合控制。

关键词: 锆石U-Pb测年, 地球化学, 集宁地区, 蒙古—鄂霍次克洋, 古太平洋

Abstract:

The Mesozoic magmatic rocks in the middle segment of the northern margin of the North China Craton have complex petrological characteristics, and there are divergent understandings on the formation of granites, which restricts the in-depth understanding of petrogenetic dynamics. In this paper, the Mesozoic Xiaodaqingshan granite pluton in Inner Mongolia, located in this tectonic belt, is selected as the research object. Studies on petrography, zircon U-Pb dating, whole-rock element composition, and Sr-Nd-Pb isotope composition are carried out to explain the genesis and source properties of the magmatic rocks, and to further discuss the Mesozoic tectonic dynamic environment in the study area. The results show that the weighted average 206Pb/238U age of zircons from monzogranite is (135.4±1.2) Ma, indicating that the host granites formed in the Early Cretaceous. The rocks are characterized by high silica (73.37%-77.21%), high alkali (5.93%-8.78%), and high aluminum saturation index (1.02-1.32), belonging to the peraluminous high-K calc-alkaline series. They are enriched in large ion lithophile elements (Rb, K) and high field strength elements (Th, U), depleted in Nb, Ba, Sr, Ti, and P; enriched in light rare earth elements and depleted in Eu; with low (87Sr/86Sr)i values (0.7094-0.7391), highly negative εNd(t) values (-15.37 to -16.19), 206Pb/204Pb ratios of 17.158-17.365, 207Pb/204Pb ratios of 15.437-15.442, and 208Pb/204Pb ratios of 37.881-38.082. Comprehensive geochemical characteristics indicate that the Xiaodaqingshan granite is a highly differentiated I-type granite, mainly derived from partial melting of lower crustal materials. Combined with regional geological evidence, it is considered that the Xiaodaqingshan granite in Jining area, Inner Mongolia, formed in the post-orogenic stage, and its formation may be controlled by the combined effects of the closure of the Mongolia-Okhotsk Ocean basin and the subduction of the Paleo-Pacific Plate.

Key words: zircon U-Pb dating, geochemistry, Jining area, Mongolia-Okhotsk Ocean, Paleo-Pacific Ocean

中图分类号: