Geology, fluid inclusions, and H-O-S-Pb isotopes of the Chigou porphyry Cu deposit in Southern Qinling, central China: Implication for ore genesis
Geology, fluid inclusions, and H-O-S-Pb isotopes of the Chigou porphyry Cu deposit in Southern Qinling, central China: Implication for ore genesis
复制标题
南秦岭赤沟斑岩铜矿床地质、流体包裹体及H-O-S-Pb同位素：对成矿的启示
DOI：
10.1016/j.oregeorev.2020.103723
复制
发表时间：
2020
影响因子：
3.3
通讯作者：
Fang-Fang Zhang
中科院分区：
文献类型：
--
作者：
Zhong-Yu Zhang;Wang Yin-Hong;Jia-Jun Liu;Fang-Fang Zhang
池沟斑岩铜存款矿床位于南秦岭成矿带东段、华中造山带南缘。铜矿化与石英闪长岩、石英闪长斑岩和花岗斑岩共生，呈脉状、细脉状、浸染状或细脉-浸染状产出于主斑岩中。成矿作用可分为三个阶段：第一阶段为石英+钾长石+黄铁矿±黄铜矿，第二阶段为石英+钾长石+黄铜矿±辉铜矿，第三阶段为石英+方解石+黄铁矿。含石英脉中流体包裹体可分为富汽两相（V型）、富液两相（L型）、高盐度（H型）和富CO2（C型）4种类型。将FI在330-473 °C的温度下（对于阶段I）、174-345 °C的温度下（对于阶段II）和128-272 °C的温度下（对于阶段III）均质化，相应的盐度为3.8-53.6重量% NaCl当量，1.4-15.1重量% NaCl当量，和0.4-7.7重量%的NaCl当量，分别氢、氧同位素数据表明，成矿流体以岩浆特征为主，后期被大气降水稀释。不同阶段黄铜矿和黄铁矿的δ 34 S值变化范围较窄，为−0.2 ~ −2‰，与典型岩浆热液体系的硫同位素值一致。黄铜矿的206 Pb/204 Pb、207 Pb/204 Pb和208 Pb/204 Pb比值与斑岩岩体相似。所有稳定同位素和放射性同位素结果表明，成矿组分（即金属和硫）来自岩浆与地壳物质的水库。激光拉曼显微光谱和流体包裹体分析结果表明，池沟存款是由一个初始为高温-中温、高氧逸度（fO 2）和富CO2的流体系统形成的，估计深度为0.7-2.1 km。温度和fO 2的降低以及流体沸腾是控制池沟硫化物沉淀的关键因素。
The Chigou porphyry Cu deposit is located in eastern segment of the Southern Qinling metallogenic belt, on the southern margin of the Central China Orogenic Belt. Copper mineralization is associated with quartz diorite, quartz diorite porphyry and granite porphyry, and occurs as veins, veinlets, disseminations, or veinlet-disseminations within host porphyries. Ore-forming process could be divided into three stages: stage I quartz + K-feldspar + pyrite ± chalcopyrite, stage II quartz + chlorite + chalcopyrite ± molybdenite and stage III quartz + calcite + pyrite. Four types of fluid inclusions (FIs) were distinguished in quartz-bearing veins, including vapor-rich two-phase (V-type), liquid-rich two-phase (L-type), hypersaline (H-type), and CO2-rich (C-type) inclusions. The FIs were homogenized at temperatures of 330–473 °C for stage I, 174–345 °C for stage II, and 128–272 °C for stage III, with corresponding salinities of 3.8–53.6 wt% NaCl equiv., 1.4–15.1 wt% NaCl equiv., and 0.4–7.7 wt% NaCl equiv., respectively. Hydrogen and oxygen isotope data indicate that the ore-forming fluids have a dominant magma signature and were diluted by meteoric water during the late stage. Chalcopyrite and pyrite from different stages record a narrow range of δ34S values from −0.2 to −2‰, consistent with the sulfur isotopic values of typical magmatic-hydrothermal system. Chalcopyrite has similar206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios to those of porphyry intrusions. All stable and radiogenic isotope results reveal that the ore-forming components (i.e. metal and sulfur) were sourced from a magmatic reservoir with some crustal materials. Laser Raman micro spectroscopy data and fluid inclusion analytical results suggest that the Chigou deposit was formed by an initially high- to intermediate-temperature, high-oxygen fugacity (fO2) and CO2-rich fluid system at an estimated depth of 0.7–2.1 km. Decreases in temperature andfO2as well as fluid boiling were critical factors controlling sulfide precipitation at Chigou.