近日，黑龙江科技大学Wang, Jian小组在研究青海三江成矿带查涌铜多金属矿床流体包裹体，及H-O-S-Pb同位素系统中取得新进展。2024年5月8日出版的《地球化学学报》发表了这项成果。

据悉，查涌铜多金属矿床是近年来发现的一个铜多金属矿床，赋存于青藏高原北羌塘地体东北方向的三江成矿带。矿体赋存于粉砂岩中，受西北向断裂构造控制。

研究小组根据矿脉间的组合、组合和切割关系，将热液成矿期划分为3个成矿阶段：(1)辉钼矿成矿阶段、(2)铜多金属硫化物，和(3)石英-碳酸盐阶段。与硫化物矿物伴生的石英中存在两种类型的流体包裹体（FIs），即液态和富蒸汽包裹体。早期FIs既富含液体又富含蒸汽，在364.1-384.2℃的温度下均质化，盐度在0.70%-9.60%NaCl当量(eqv)之间。中期FIs也富含液体和蒸汽，在272.4-355.6℃的温度下均质化，盐度在0.53%-17.10% NaCl当量之间。晚期的FIs为液态，在209.4-255.3℃的温度下均质化，盐度在0.35%-6.87%NaCl当量之间。

该矿床样品的δ³⁴S值分别为21.8‰-19.2‰和5.5‰-6.0‰，表明硫分别来源于宿主沉积物和岩浆流体。矿床内金属矿物²⁰⁶Pb/²⁰⁴Pb、²⁰⁷Pb/²⁰⁴Pb、²⁰⁸Pb/²⁰⁴Pb值分别为18.439-18.458、15.656-15.679、38.772-38.863，表明金属来源于上地壳和造山带。矿床样品的δ¹⁸O_W值为2.99‰-7.99‰，δD_W值为-84.4‰至-73.9‰，表明成矿流体为岩浆流体，并混有少量大气降水。查涌铜多金属矿床成矿流体为高温、中低盐度H₂O-NaCl-CH₄-N₂ ±CO₂流体系统。早期高温岩浆流体因沸腾而降温，经大气降水的混合作用，逐渐演化为后期中低温低盐度流体，引导辉钼矿矿化，形成铜多金属硫化物脉和石英碳酸盐脉。

附：英文原文

Title: Fluid inclusion and H-O-S-Pb isotope systematics of the Chayong Cu-polymetallic deposit, Sanjiang Metallogenic Belt, Qinghai Province, China

Author: Wang, Jian, Wang, Hao, Sun, Fengyue, Wang, Fei, Li, Xiangwen, Yue, Hongju

Issue&Volume: 2024-05-08

Abstract: The Chayong Cu-polymetallic deposit is a recently discovered Cu-polymetallic deposit hosted in the Sanjiang Metallogenic Belt within the Tibetan Plateau of China to the northeast of the North Qiangtang terrane. The ore body occurs in siltstone and is controlled by a northwest-trending fault structure. According to the associations, assemblages, and cutting relationships between ore veins, the hydrothermal mineralization period can be divided into three mineralization stages: (1) a molybdenite mineralization stage, (2) a Cu-polymetallic sulfide stage, and (3) a quartz-carbonate stage. Two types of fluid inclusions (FIs), namely, liquid and vapor-rich inclusions, are present in quartz associated with sulfide minerals. Early-stage FIs are both liquid and vapor-rich, homogenized at temperatures ranging from 364.1 to 384.2 °C, and have salinities ranging from 0.70% to 9.60% NaCl equivalent (eqv). The middle-stage FIs are also both liquid- and vapor-rich, homogenized at temperatures ranging from 272.4 to 355.6 °C, and have salinities ranging from 0.53%–17.10% NaCl eqv. The late-stage FIs are liquid, homogenized at temperatures ranging from 209.4 to 255.3 °C, and have salinities ranging from 0.35%–6.87% NaCl eqv. The samples from the deposit have δ³⁴S values of 21.8‰ to 19.2‰ and 5.5‰ to 6.0‰, suggesting that sulfur was derived from the host sediments and magmatic fluids, respectively. The metallic minerals within the deposit have 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb²⁰⁶Pb/²⁰⁴Pb、²⁰⁷Pb/²⁰⁴Pb、²⁰⁸Pb/²⁰⁴Pbvalues of 18.439–18.458, 15.656–15.679, and 38.772–38.863, respectively, suggesting that the metals were derived from the upper crust and orogenic belts. The samples from the deposit have δ¹⁸O_W values of 2.99‰–7.99‰ and δD_W values ranging from -84.4‰ to -73.9‰, indicating that the ore-forming fluids were magmatic and mixed with minor amounts of meteoric water. The ore-forming fluid of the Chayong copper polymetallic deposit was a high-temperature, medium- to low-salinity H₂O–NaCl–CH₄–N₂±CO₂ fluid system. The early high-temperature magmatic fluid, due to boiling, decreased in temperature, and via the mixing of meteoric water, gradually evolved towards the later-stage medium- to low-temperature and low-salinity fluid, causing molybdenite mineralization and forming copper polymetallic sulfide veins and quartz carbonate veins.

DOI: 10.1007/s11631-024-00700-7

Source: https://link.springer.com/article/10.1007/s11631-024-00700-7