| 内蒙古东乌旗沙麦钨矿床成矿机制：来自流体包裹体及稳定同位素的证据 |
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| 引用本文： | 吴皓然. 内蒙古东乌旗沙麦钨矿床成矿机制：来自流体包裹体及稳定同位素的证据[J]. 地质与勘探, 2024, 60(4): 685-699 |
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| 作者姓名： | 吴皓然 |
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| 作者单位： | 中国冶金地质总局矿产资源研究院, 北京;北京科技大学土木与资源工程学院, 北京 |
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| 基金项目： | 中国地质调查局项目(编号：12120113056700)资助 |
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| 摘 要： | 内蒙古东乌旗沙麦钨矿床位于中亚巨型缝合带的最东段,矿床内广泛发育云英岩化,钨矿体主要受NW向断裂构造控制,呈黑钨矿-石英脉状产出在燕山期沙麦岩体（岩性主要为黑云母二长花岗岩）和泥盆系围岩地层（岩性主要为角岩化砂岩、砂砾岩）中。成矿阶段从早到晚分别为：石英-黄玉阶段（Ⅰ）、云英岩-黑钨矿阶段（Ⅱ）和晚期硅化阶段（Ⅲ）。本文对矿床流体包裹体及C-H-O-S同位素进行了研究,结果显示：矿床中普遍发育CO2-H2O包裹体及水溶液气液两相流体包裹体。从成矿早期至成矿晚期,矿床流体中富CO2包裹体逐渐减少,CO2含量逐渐降低。成矿早期可见熔体包裹体与流体包裹体共存的现象,属低盐度、富CO2的岩浆来源流体。矿床成矿作用从早到晚,流体包裹体均一温度分别为279~341℃、196~286℃、103~201℃;流体盐度分别为(1.6~9.1)%NaCleq、(3.0~11.1)%NaCleq、(0.9~4.7)%NaCleq。激光拉曼光谱分析结果显示,流体中的气相主要是CO2,部分含有H2O和CH4。成矿流体从早期中高温、中盐度流体向晚期低温、低盐度流体演化,属NaCl-H2O-CO2±CH4热液体系。矿床稳定同位素研究表明,沙麦钨矿床的成矿流体主要来源于岩浆水,并在成矿晚期混入了大气水。矿床硫的来源与早白垩世岩浆-热液系统或深部幔源岩浆相关,并混入了部分地层硫。综合分析认为,沙麦钨矿为一岩浆期后热液型钨矿床。燕山期侵入体从深部携带成矿物质,经历了岩浆分异和流-熔体相互作用等过程,形成区内岩浆-热液成矿系统。流体的不混溶是导致含钨络合物分解乃至最后沉淀成矿的主要原因。
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| 关 键 词： | 流体包裹体 激光拉曼光谱 C-H-O-S同位素 沙麦钨矿 东乌旗 内蒙古 |
| 收稿时间： | 2024-01-11 |
| 修稿时间： | 2024-06-12 |
Metallogenic mechanism of the Shamai tungsten deposit in Dong Ujimqin Banner of Inner Mongolia: Evidence from fluid inclusions and stable isotopes |
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| Wu Haoran. Metallogenic mechanism of the Shamai tungsten deposit in Dong Ujimqin Banner of Inner Mongolia: Evidence from fluid inclusions and stable isotopes[J]. Geology and Prospecting, 2024, 60(4): 685-699 |
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| Authors: | Wu Haoran |
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| Affiliation: | Institute of Mineral Recourses Research, China Metallurgical Geology Bureau, Beijing; Civil and Resource Engineering School, University of Science and Technology Beijing, Beijing |
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| Abstract: | The Shamai tungsten deposit is located in the easternmost section of the Central Asian giant suture zone, with widespread development of biotitization. The tungsten ore body is mainly controlled by NW-trending fault structures and is produced in the form of wolframite quartz veins in the Yanshanian Shamai rock body (mainly composed of biotite diorite) and the Devonian surrounding rock strata (mainly composed of brecciated sandstone and sandstone). The mineralization stages from early to late are as follows: quartz topaz stage (I), greisen-wolframite stage (II), and late silicification stage (III). Fluid inclusions and C-H-O-S isotopes of the shamai deposit showe that CO2-H2O inclusions and aqueous gas-liquid two-phase fluid inclusions are commonly developed. From the early to late stages of mineralization, the CO2 rich inclusions in the ore deposit gradually decrease, and the CO2 content gradually decreases. In the early stages of mineralization, the coexistence of melt inclusions and fluid inclusions was observed, belonging to low salinity and CO2 rich magma derived fluids. From early to late ore-forming process of the ore deposit, the uniform temperatures of fluid inclusions are 279～341 ℃, 196～286 ℃, and 103～201 ℃, respectively, and the fluid salinity is (1.6～9.1)% NaCleq, (3.0～11.1)% NaCleq, and (0.9～4.7)% NaCleq, respectively. The results of Laser Raman spectroscopy analysis show that the gas phase in the fluid is mainly CO2, with some containing H2O and CH4. The ore-forming fluid evolved from early medium-high temperature and medium salinity fluids to late low temperature and low salinity fluids, belonging to the NaCl-H2O-CO2±CH4 hydrothermal system. Research on stable isotopes of the deposit indicates that the ore-forming fluid of the Shamai tungsten deposit mainly comes from magmatic water, and mixed with atmospheric water in the late stage of mineralization. The source of sulfur in the deposit is related to the Early Cretaceous magmatic hydrothermal system or deep mantle derived magma, and some surrounding rock-derived sulfur. Comprehensive analysis suggests that the Shamai tungsten deposit is a post magmatic hydrothermal tungsten deposit. The Yanshanian intrusive body carried ore-forming materials from deep and underwent processes such as magma differentiation and flow melt interaction, forming a magmatic hydrothermal ore-forming system within the region. The immiscibility of fluids is the main reason for the decomposition and ultimately precipitation of tungsten containing complexes. |
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| Keywords: | fluid inclusion Laser Raman spectroscopy C-H-O-S isotopes Shamai tungsten deposit Dong Ujimqin Banner Inner Mongolia |
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