Genesis of the Wurinitu W-Mo deposit, Inner Mongolia, northeast China: Check for Constraints from geology, fluid inclusions and isotope systematics
Genesis of the Wurinitu W-Mo deposit, Inner Mongolia, northeast China: Check for Constraints from geology, fluid inclusions and isotope systematics
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内蒙古乌日尼图钨钼矿床成因：地质、流体包裹体和同位素系统学的制约
DOI：
10.1016/j.oregeorev.2018.01.031
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发表时间：
2018
影响因子：
3.3
通讯作者：
Zhang Zhao-Chong
中科院分区：
文献类型：
--
作者：
Wang Yin-Hong;Zhang Fang-Fang;Liu Jia-Jun;Xue Chun-Ji;Zhang Zhao-Chong
乌里里图钨钼矿床位于东北中国大兴安岭二连-东乌珠穆沁成矿带内。钨、钼矿化一般以脉状赋存于中、下奥陶统围岩中的石英中，或以侵入于早白垩世二长花岗岩中的形式出现。流体包裹体研究和多种同位素分析为确定热液流体的演化、金属和流体的来源以及矿物沉淀机制提供了系统的证据，这些对岩浆-热液系统具有重要意义，但人们对此知之甚少。在乌里图W矿化(I)、Mo矿化(II)和石英碳酸盐(III)成矿阶段的石英脉中，发现了L(富液两相FIA)、V(富气两相FIA)和L-V(液-汽两相FIA)三种流体包裹体组合。成矿流体由钨、钼成矿阶段的高-中温、中-低盐度H2O-NaC l- ± -CO2体系演化为石英-碳酸盐阶段的低温低盐度H2O-Nacl体系，圈闭温度分别为∼365 °C、∼2 66 °C和∼198 °C。δDH2O= −116~−92‰)表明，I期流体主要来源于岩浆水，II期和III期流体主要来自大气降水。硫((206Pb/204Pb = 18.099–18.728,207Pb/204Pb = 15.527–15.616，)和铅同位素(δ34SVCDT= 1.9-4.0‰)和208Pb204Pb值( = 38.019-38.465)表明热液中的成矿金属来自花岗岩浆。这些观测结果表明：(1)乌里图钨钼矿床是岩浆-热液成矿系统；(2)钨、钼成矿作用分别发生在203294bar 和102bar∼的静岩石压力下；(3)流体沸腾和与大气降水的混合作用可能是控制该矿床大规模成矿的关键因素。
The Wurinitu W–Mo deposit is located in the Erlian-East Ujimqin metallogenic belt in the Great Xing’an Range, NE China. Tungsten and molybdenum mineralization generally occurs as veins in quartz hosted by the Middle to Lower Ordovician wall rocks or as disseminations in the Early Cretaceous monzogranite intrusions. Fluid inclusion studies and multiple isotope analyses, provide systematic evidence to determine the evolution of the hydrothermal fluids, the source of metals and fluids, as well as mineral precipitation mechanisms, which are significant for the magmatic-hydrothermal system but are poorly understood. Three types of fluid inclusion assemblages (FIAs), including L (liquid-rich two-phase FIAs), V (vapor-rich two-phase FIAs), and L-V (liquid–vapor two-phase FIAs), have been identified in quartz veins from the W-mineralization (I), Mo-mineralization (II), and quartz – carbonate (III) stages at Wurinitu. The ore-forming fluids evolved from a high- to moderate-temperature and moderate- to low-salinity H2O–NaCl ± CO2system in the W- and Mo- mineralization stages to a low-temperature and low-salinity H2O–NaCl system in the quartz-carbonate stage; they were trapped at temperatures of ∼365 °C, ∼266 °C, and ∼198 °C. The results of hydrogen and oxygen isotope analyses (δ18OH2O= −4.0 to +7.7‰; δDH2O= −116 to −92‰) indicate that the stage I fluids dominantly originated from magmatic water, and the stages II and III show addition of meteoric water. Sulfur (δ34SVCDT= 1.9–4.0‰) and lead isotope values (206Pb/204Pb = 18.099–18.728,207Pb/204Pb = 15.527–15.616, and208Pb/204Pb = 38.019–38.465) suggest that the ore metals in the hydrothermal fluids were derived from the granitic magma. All these observations reveal that (1) the Wurinitu W–Mo deposit is a magmatic-hydrothermal ore system, (2) W- and Mo- mineralization occurred under lithostatic pressure of 203–294 bars, and hydrostatic pressure of ∼102 bars, respectively, and (3) fluid boiling and mixing with meteoric water might be the key factors controlling the large-scale ore deposition at Wurinitu.