| 北山成矿带金窝子金矿床成矿流体时空演化与成矿机制 |
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| 引用本文： | 王钏屹,王琦崧,疏孙平,张静.北山成矿带金窝子金矿床成矿流体时空演化与成矿机制[J].地球科学,2018,43(9):3126-3140. |
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| 作者姓名： | 王钏屹 王琦崧 疏孙平 张静 |
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| 作者单位： | 1.中国地质大学地质过程与矿产资源国家重点实验室, 北京 100083 |
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| 基金项目： | 国家自然科学基金项目41572065国家重点基础研究发展计划"973计划"项目2014CB440802 |
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| 摘 要： | 金窝子金矿床位于晚古生代塔里木板块与哈萨克斯坦板块俯冲碰撞带南缘的北山裂谷中，属于造山型矿床，目前该矿床成矿流体时空演化及成矿机制尚不明确，利用岩相学、显微测温和激光拉曼光谱分析对不同成矿阶段、不同海拔标高的脉石矿物中的流体包裹体进行了系统研究.依据矿物共生组合及脉体穿插关系，金矿床热液成矿过程可划分为3个阶段，从早到晚依次为:黄铁矿-石英阶段（早阶段）、石英-黄铁矿-多金属硫化物阶段（中阶段）、石英-碳酸盐阶段（晚阶段），金矿化主要发育在中阶段.脉石矿物中流体包裹体发育两种类型:NaCl-H2O包裹体（W型）和CO2-H2O-NaCl包裹体（C型），前两个阶段发育W型和C型包裹体，晚阶段只发育W型包裹体.从早阶段到晚阶段，流体包裹体完全均一温度的峰值分别为200~300 ℃、160~240 ℃、120~180 ℃，盐度依次为1.4%~14.8% NaCleqv、0.4%~14.5% NaCleqv、0.2%~7.6% NaCleqv.从早阶段到晚阶段，流体由CO2-H2O-NaCl体系向NaCl-H2O体系演变，完全均一温度和盐度均呈现出降低趋势，表现为由中温、中低盐度、富CO2的变质流体向中低温、低盐度、贫CO2的大气降水演化的趋势.矿脉垂向上的均一温度和盐度随深度增加表现出"低-高-低"的特点，可能与成矿流体多期次叠加有关.自矿区西南向东北包裹体均一温度逐渐升高，成矿深度逐渐增加，反映了矿区东北部可能为热源中心，表明矿区东北部应具有深部找矿前景.包裹体的物理化学特征及氢氧同位素特征表明，流体的混合可能是金沉淀的主要机制.
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| 关 键 词： | 矿床 流体包裹体 时空演化 金窝子金矿床 北山 |
| 收稿时间： | 2018-03-24 |
Temporal and Spatial Evolution of Ore-Forming Fluid and Metallogenic Mechanism in the Jinwozi Gold Deposit,Beishan Metallogenic Belt |
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| Abstract: | The Jinwozi gold deposit is located in the central Beishan area, southern margin of the subduction-collision zone between the Late Paleozoic Tarim and Kazakhstan plates. The ore genesis of the Jinwozi gold deposit belongs to the orogenic type.However, the temporal and spatial evolution of ore-forming fluid and the metallogenic mechanism remain relatively unclear. The fluid inclusions in quartz from different mineralization stages and depths were analyzed by petrography, microscopic temperature measurement and laser Raman spectrum in this paper.The hydrothermal ore-forming process can be divided into three stages according to mineral assemblages and crosscutting relationships among the veins, from early to late, i.e., pyrite-quartz stage (early stage); quartz-pyrite-polymetallic sulfide stage (middle stage); quartz-carbonate stage (late stage). The gold mineralization mainly occurs in the middle stage.Two types of fluid inclusions are identified based on petrography and laser Raman spectroscopy:NaCl-H2O inclusions (W-type) and CO2-H2O-NaCl inclusions (C-type). Both of the two fluid inclusion types can be observed in the early stage and middle stage quartz; while only the W-type inclusions occur in the late stage.The homogenization temperatures of early stage fluid inclusions range from 200℃ and 300℃, with salinities of 1.4%-14.8% NaCleqv. The fluid inclusions of middle stage are homogenized between 160℃ and 260℃, with salinities of 0.4%-14.5% NaCleqv; and in late stage they are 120-180℃ and of 0.2%-7.6% NaCleqv, respectively.From early to late stage, the ore-forming fluid system evolved from a CO2-H2O-NaCl system to a NaCl-H2O system, with the homogenization temperature and salinities decreasing gradually. The results show that the ore-forming fluid system has evolved from the mesothermal, medium-low salinity, CO2-rich metamorphic water to the mesothermal-epithermal, low salinity and CO2-poor meteoric water. From the shallow to deep of the orebody, the homogenization temperature and salinity firstly increase and then decrease, which might be caused by the multi-superposition of ore-forming fluids. The homogenization temperature and ore-forming depth increase gradually from southwest to northeast area at Jinwozi gold deposit, which indicates that the northeastern intrusion may be a heat source center. Therefore, it is prospected that there will be a good metallogenic potential in the northeastern mining area. The physicochemical and hydrogen-oxygen isotopic data of fluid inclusions show that fluid mixing might be the dominant mechanism of gold deposition. |
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