国庆钨矿钾长花岗岩年代学、地球化学特征及其地质意义
DOI:
作者:
作者单位:

作者简介:

通讯作者:

中图分类号:

基金项目:

“十一五"国家科技支撑计划重点资助项目(2007BA25B04)


Chronology and geochemical characteristics of K-feldspar granite in the Gongqing tungsten deposit and their geological implications
Author:
Affiliation:

Fund Project:

  • 摘要
  • |
  • 图/表
  • |
  • 访问统计
  • |
  • 参考文献
  • |
  • 相似文献
  • |
  • 引证文献
  • |
  • 资源附件
  • |
  • 文章评论
    摘要:

    国庆钾长花岗岩岩体出露于蒙古自治区额济纳旗西南部的盘陀山一带,北邻牛圈子-洗肠井缝合带,LA-ICP-MS测得该岩体的U-Pb年龄为439.1±8 Ma。岩体SiO2含量73.31%~74.36%,A/CNK>1.1, K2O/Na2O=1.25~1.40,里特曼指数介于2.06~2.22之间,属于高钾钙碱性、过铝质花岗岩系列,岩体富集大离子亲石元素,亏损高场强元素。稀土和微量元素分析显示钾长花岗岩总体轻稀土元素富集,轻、重稀土元素分馏较低,具有较明显Eu负异常(δEu=0.65~0.77),具K、Rb、Ba、Th等元素富集,Nb、Ce、Zr、Hf、Sm、Y、Yb等元素亏损的特征。综合分析表明,国庆钾长花岗岩为壳源S型同碰撞花岗岩;结合区域构造演化历史,认为国庆钾长花岗岩为古老地壳物质重熔形成,是早志留世月牙山-洗肠井古洋盆闭合同碰撞阶段的产物。同时对该区志留—泥盆纪碰撞伸展环境下成矿前景初步分析,为矿床研究和区域矿产预测工作提供参考。

    Abstract:

    Located near Pantuoshan district in Ejina Banner of southwestern Mongolia, Guoqing K-feldspar granite body lies in southern Niujuanzi-Xichangjing suture zone. LA-ICP-MS U-Pb isotopic dating of zircon separated form the rock yields an average weighted 206Pb/238U age of 439.1±8 Ma. The results of geochemical study indicate that SiO2 are in the range of 73.31%~74.36%, A/CNK>1.1, and K2O/Na2O=1.25~1.40, the Rittmann index of k-feldspar granite varies from 2.06 to 2.22, suggesting a high-K calc-alkaline series and peraluminous nature. The results also indicate that Guoqing K-feldspar granite body is highly enriched in large ion lithophile elements and strongly depleted in high field strength elements. The chondrite-normalized REE and trace elements patterns demonstrate low fractionation level between LREE and HREE, (La/Yb) N=3.40~5.44, and negative Eu(δEu=0.65~0.77), which might have been related to the plagioclase residuals during the partial melt of the original rock. The spider diagrams are characterized by Nb, Ce, Zr, Hf, Sm, Y, Yb depletion and K, Rb, Ba, Th enrichment. Rb/Sr ratios are between 4.37 and 4.70, and such high Rb/Sr ratios (>2) suggest that Guoqing granite body was probably triggered by dehydration melting of mica during the geological process. High levels of Nb and Ta and characteristics of Ta>Nb indicate high-degree evolution of the granite body, which laid the foundation of tungsten elements enrichment. CaO/Na2O ratios range from 0.152 to 0.165, and all the values are lower than 0.3, suggesting the origination from re-melting of the early Precambrian crystalline basement. In addition, the inherited zircon in the granite body yields a large number of ages between 616 Ma and 1046 Ma. In Hongliuhe area, the zircon U-Pb age of granite that intruded into ophiolite is 404.8±5.2 Ma, implying that the south Tianshan oceanic crust was formed as early as Early Cambrian, and closed before Emsian. In Xichangjing area, the closure of South Tianshan Ocean was before 439.1±8 Ma, suggesting a scissors-type opening-closing tectonic pattern. The results of geochemical study show that the S-type K-feldspar granite, which was crust-derived, might have been formed by the closure of the Hongliuhe-Yueyashan Paleo-ocean during the syn-collision stage. There are Yingzuihongshan, Wangxushan and Guoqing tungsten ore deposits in Xichangjing area. These ore deposits which were formed in the contact zone or the fissure system surrounding the granite intrusion have a close relationship with Silurian-Devonian granite intrusions. Moreover,in the tectonic setting of transformation from collision to extension from Silurian to early-Devonian, the granites related to such tectonic settings deserve detailed studies, which can not only help understand the tectonic evolution but also provide a theoretic basis for the exploration of regional mineral resources.

    参考文献
    相似文献
    引证文献
引用本文

李 鹏,吕新彪,陈 超,曹晓峰,玛依拉·艾山,苏妤芸,2011,国庆钨矿钾长花岗岩年代学、地球化学特征及其地质意义[J].岩石矿物学杂志,30(1):13~24. LI Peng, Lv Xin_biao, CHEN Chao, CAO Xiao_feng, Mayila Aishan, SU Yu_yun,2011,Chronology and geochemical characteristics of K-feldspar granite in the Gongqing tungsten deposit and their geological implications[J]. Acta Petrologica et Mineralogica,30(1):13~24.

复制
分享
文章指标
  • 点击次数:
  • 下载次数:
  • HTML阅读次数:
  • 引用次数:
历史
  • 收稿日期:
  • 最后修改日期:
  • 录用日期:
  • 在线发布日期:
  • 出版日期: