地学前缘 ›› 2016, Vol. 23 ›› Issue (5): 252-265.DOI: 10.13745/j.esf.2016.05.025

• 非主题来稿选登 • 上一篇    下一篇

西昆仑喀来子钡铁矿床地质特征、时代及成因探讨

郑梦天，张连昌，朱明田，李智泉   

  1. 1. 中国科学院 矿产资源研究重点实验室; 中国科学院 地质与地球物理研究所, 北京 100029
    2. 中国科学院大学, 北京 100049
    3. 新疆地质矿产勘查开发局 第二地质大队, 新疆 喀什 844002
    4. 新疆维吾尔自治区地质矿产勘查开发局, 新疆 乌鲁木齐 830000
  • 收稿日期:2015-10-13 修回日期:2015-11-13 出版日期:2016-09-15 发布日期:2016-09-15
  • 通讯作者: 张连昌(1959—)，男，博士，研究员，矿床地球化学专业。E-mail:lczhang@mail.iggcas.ac.cn
  • 作者简介:郑梦天(1991—)，男，博士研究生，矿床学专业。E-mail:zhengmengtian@mail.iggcas.ac.cn
  • 基金资助:

    国家自然科学基金项目(41372100)；南疆“305”项目(2015BAB05B02)

Geological characteristics, formation age and genesis of the Kalaizi BaFe deposit in West Kunlun.

 ZHENG  Meng-Tian, ZHANG  Lian-Chang, SHU  Meng-Tian, LI  Zhi-Quan   

  1. 1. Key Laboratory of Mineral Resources, Chinese Academy of Sciences; Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
    3. No.2 Geological Party, Xinjiang Bureau of Geology and Mineral Resources, Kashi 844002, China
    4. Xinjiang Bureau of Geology and Mineral Resources and Development, rümqi 830000, China
  • Received:2015-10-13 Revised:2015-11-13 Online:2016-09-15 Published:2016-09-15

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摘要：

喀来子大型钡铁矿床位于新疆西昆仑塔什库尔干地区，矿体赋存于原“布伦阔勒群”变火山沉积岩序列中。作为西昆仑地区独有的钡铁矿床，其矿石具条纹条带状构造，矿石矿物以磁铁矿和重晶石为主。矿区出露围岩主要为变泥质碎屑沉积岩(含石榴石二云石英片岩)，并夹少量变火山熔岩(黑云斜长变粒岩和黑云斜长片麻岩等)。矿体夹层黑云斜长片麻岩LAICPMS锆石UPb年龄显示原火山熔岩的形成年龄为(537.2±6.4) Ma，从而间接约束了喀来子钡铁矿床的成矿年龄。依此，本文建议“原古元古界布伦阔勒群”应分离出一套寒武纪(火山)沉积成矿系列。矿石中磁铁矿氧同位素(δ18O=5.0‰~9.2‰)、硫酸盐(δ34S=39.3‰~41.4‰)和黄铁矿硫同位素(δ34S=17.0‰~23.5‰)特征表明，喀来子钡铁矿床为经历细菌还原作用(BSR)的热液喷流沉积型矿床(SEDEX)。具体成因机制可能为：在早寒武世半封闭的海水环境中，富含铁钡的海底热液沿断裂等构造喷流至海底，与周围温度较低的海水混合导致温度、pH和氧逸度等因素发生突变，从而促使相关矿物沉淀。其中，重晶石为热液流体中钡与经BSR作用后残余的SO2-4反应生成，黄铁矿为含铁热液与SO2-4还原产物H2S相结合形成。当H2S消耗完全后，富铁热液在弱氧化条件下沉淀于海底形成磁铁矿。

关键词: 重晶石, 磁铁矿, 锆石U Pb定年, 硫氧同位素, 喀来子钡铁矿床, 西昆仑

Abstract:

Located in Taxkorgan area of western Kunlun Mountains, the largescale Kalaizi BaFe deposit is hosted in the metamorphic volcanic sedimentary sequences of previously defined “Bulunkuole Group”. As a unique BaFe deposit in western Kunlun Mountains, the ore minerals mainly consist of magnetite and barite, and the ores are characterized by banded or laminated structure. While the wallrocks consist predominantly of metaargillaceous clastic rock (garnetbearing twomica quartz schist), which is interlayered with magnetitebarite ore, and a small amount of metaacid volcanic rocks (biotite plagiogneiss and biotite plagioclase granulite). LAICPMS zircon UPb dating age of biotite plagiogneiss limits the oreforming age of the Kalaizi BaFe deposit to ca. 537.2±6.4 Ma, which also suggests that the previously defined “Bulunkuole Group” can isolate the Cambrian volcanosedimentary metallogenic series. Oxygen isotope compositions of magnetite samples, sulfur isotope compositions of sulfate minerals and pyrite show that the ore deposit was marine hydrothermalexhalation sedimentary type deposit (SEDEX) that was affected by bacterial sulfate reduction. So the specific mineralization mechanism may be as follows: in the Early Cambrian semirestricted marine basin, when barium and ironbearing hydrothermal fluids were migrated and encountered with sea water by fault, the minerals precipitated because of the changes in temperature, pH and oxygen fugacity. To summarize, barite formed by mixing of bariumbearing hydrothermal fluids and sulfatebearing pore waters. Pyrite precipitated where ironbearing hydrothermal fluids encountered pore waters that had been charged with H2S by bacterial sulfate reduction. And after the H2S was consumed, magnetite precipitated directly by suboxic ironbearing hydrothermal fluids in the sea floor.

Key words: barite, magnetite, zircon U Pb dating, sulfur and oxygen isotopes, Kalaizi Ba Fe deposit, Western Kunlun Mountains

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