| 青海玉树尕龙格玛VMS型矿床流体包裹体及H-O-S-Pb同位素特征 |
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| 引用本文： | 王键,孙丰月,禹禄,姜和芳,王飞,宁传奇.青海玉树尕龙格玛VMS型矿床流体包裹体及H-O-S-Pb同位素特征[J].地球科学,2017,42(6):941-956. |
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| 作者姓名： | 王键 孙丰月 禹禄 姜和芳 王飞 宁传奇 |
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| 作者单位： | 吉林大学地球科学学院，吉林 长春 130061 |
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| 基金项目： | 中国地质调查局项目12120113098300国家自然科学基金项目41272093 |
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| 摘 要： | 为确定中国三江成矿带北段尕龙格玛VMS(volcanogenic massive sulfide)型矿床的成矿物理化学条件、成矿物质来源、成矿流体来源，探讨成矿机制，对矿体特征、流体包裹体显微测温和激光拉曼光谱分析以及S、Pb、H、O同位素进行了系统研究.矿体赋存于晚三叠世巴塘群英安质火山岩中，具有VMS型矿床的双层结构，由下部热液流体补给通道相的脉状-网脉状矿化系统和上部海底盆地卤水池喷气-化学沉积系统组成.通道相中流体包裹体可分为富气相包裹体和水溶液包裹体，均一温度为175.6~263.3 ℃，盐度为1.05%~6.29% NaCl eqv.，密度为0.820~0.935 g/cm3，激光拉曼光谱分析包裹体气相成分为H2O、CO2和少量N2；沉积相重晶石中仅发育水溶液包裹体，均一温度为105.2~157.1 ℃，盐度为0.18%~5.55% NaCl eqv.，密度为0.735~1.173 g/cm3，显示了流体由通道相向沉积相温度显著降低，盐度保持不变，密度变大的趋势，与典型VMS型矿床流体特征相似.氢氧同位素(δ18OH2O:0.25‰~1.75‰，δD:-103.2‰~-65.3‰)研究表明，成矿流体主要来源于岩浆水和海水的混合.综合分析前人硫同位素研究结果(δ34S:1.13‰~2.45‰，12.36‰~12.37‰)及本次获得硫同位素结果(δ34S:-22.9‰~-14.7‰)表明硫来源于岩浆和细菌还原的海水硫酸盐或基底岩石.硫化物方铅矿的206Pb/204Pb、207Pb/204Pb和208Pb/204Pb分别为18.449~18.519、15.699~15.777和38.875~39.141，具有高放射性铅的特征，μ值为9.65~9.80，结果显示Pb等成矿物质主要来自于上地壳，并有岩浆物质参与成矿.成矿流体与海水的混合作用是尕龙格玛矿床形成的主要机制.
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| 关 键 词： | 三江成矿带 尕龙格玛 成矿流体 矿床 S同位素 Pb同位素 H、O同位素 岩石学 |
| 收稿时间： | 2016-12-10 |
Fluid Inclusions and H-O-S-Pb Isotope Systematics of the Galonggema Cu Deposit in Yushu,Qinghai Province,China |
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| Abstract: | In order to determine the metallogenic physicochemical condition, ore-forming materials, ore-forming fluid and metallogenic mechanism of Galonggema VMS (volcanogenic massive sulfide) deposit in the northern Sanjiang metallogenic belt, China, orebody features, fluid inclusion microthermometry, laser Raman spectroscopy, and S, Pb, H, O isotopes are studied in this paper. It is found that deposit is hosted in the Late Triassic Batang Group dacite-volcanic tuff and consists of two parts, namely, lower ore belt of vein-stockwork mineralization system belonging to hydrothermal fluid supply channel, and upper ore belt of exhalative-chemical deposit system of submarine basin brine pond. Fluid inclusions (FIs) in vein-stockwork mineralization are both aqueous and gas-rich, homogenization temperature from 175.6 to 263.3 ℃, and salinities of 1.05%-6.29% NaCl equivalent (eqv.) and densities of 0.820-0.935 g/cm3. Laser Raman spectroscopic analyses of the gas phase components of FIs show they are dominated by H2O, CO2 and minor amounts of N2. Fluid inclusions in barite in exhalative-chemical deposit system are only aqueous FIs, homogenization temperature from 105.2 to 157.1 ℃, and salinities of 0.18%-5.55% NaCl eqv. and densities of 0.735-1.173 g/cm3 suggesting from lower ore belt to upper ore belt metallogenic temperature drops, salinities does not change, and the density of fluid increases. Hydrogen and oxygen isotopic study (δ18OH2O: 0.25‰-1.75‰, δD: -103.2‰ to -65.3‰) shows that metallogenic fluid is a mixture of seawater and magmatic water. The predecessors research results of sulfur isotope previous research indicates that the sulfur were provided by magma and bacteria reduction seawater sulfate or basement rock. Lead isotopic compositions of galena show 206Pb/204Pb ratios ranging from 18.449 to 18.519, 207Pb/204Pb ratios from 15.677 to 15.777, and 208Pb/204Pb ratios from 38.875 to 39.145, respectively. Lead isotopes has high radioactive lead isotope compositions with μ values of 9.65~9.80. It suggests that the lead mainly was sourced from crustal components and little from magma. The mixing of ore-forming fluid and seawater is the main metallogenic mechanism of Galonggema deposit. |
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