Fluid evolution of the Wushan skarn-dominant copper deposit in the Middle-Lower Yangtze River metallogenic belt, Eastern China
Fluid evolution of the Wushan skarn-dominant copper deposit in the Middle-Lower Yangtze River metallogenic belt, Eastern China
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长江中下游成矿带巫山矽卡岩型铜矿床流体演化
DOI：
10.1016/j.oregeorev.2019.103035
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发表时间：
2019-09
影响因子：
3.3
通讯作者：
Luo Xiao-Ya
中科院分区：
文献类型：
--
作者：
Wen Chun-Hua;Shao Yong-Jun;Li Bin;Jeffrey M. Dick;Lai Jian-Qing;Huang Ge-Fei;Luo Xiao-Ya
武山矽卡岩铜存款（1.37 Mt，含铜1.17%）位于长江中下游多金属带。矽卡岩型矿体主要产于早白垩世花岗闪长斑岩（148-138 Ma）的石炭纪和二叠纪碳酸盐岩中。成矿作用经历了热液演化、矽卡岩形成和斑岩成矿两个阶段。矽卡岩期在接触带形成块状、浸染状、细脉和角砾岩型矿化，而斑岩矿化仅以浸染状和细脉型矿化为特征。根据流体成分和相组合，将流体包裹体分为子矿物包裹体、CO2包裹体、蒸汽包裹体和水汽包裹体4种类型。内矽卡岩中的原生流体被解释为从低盐度初始流体演化而来的两个不混溶相。初始过饱和流体具有相对较低的盐度，宽范围的Th值（433-626 °C）意味着非均质圈闭，对应于371-646 bar的压力和3.7-6.5 km的静水深度。原生流体包裹体显示S型包裹体（~ 30.0wt%NaCl equiv）与富汽、富液包裹体共存，表明流体不渗透，非均质捕获导致相分离。原生富蒸汽包裹体的均一温度（347-434 °C）代表捕获温度，对应的捕获压力范围为152 - 374 bar，流体静力学深度为1.5-3.7 km。幕式斑岩铜矿化规模很小，在流体演化过程中具有明显的降温降盐趋势。一个类似的场景发生在斑岩幕，其中流体的不可渗透性导致铜矿化。显着的趋势，降低温度和盐度的两个矿化幕反映了从岩浆流体为主的系统的混合源流体，包括地层水从围岩和/或大气降水的变化。在流体化学转变的控制下，这种混合过程产生了一个相对较冷的流体系统，具有较低的盐度，这促进了Cu-Fe硫化物的沉淀。H-O-C同位素特征进一步表明，流体和金属都主要来自岩浆源，多个流体脉冲有助于形成五山存款中的矽卡岩矿物和硫化物。
The Wushan copper skarn deposit (1.37 Mt at 1.17% Cu) is located in the Middle-Lower Yangtze River polymetallic belt. Skarn orebodies mainly occur in the Carboniferous and Permian carbonates adjacent to Early Cretaceous granodiorite porphyries (148–138 Ma). Ore deposition underwent two episodes of metallogenic events, involving hydrothermal evolution followed by skarn formation and porphyry-related mineralization. The skarn episode formed massive, disseminated, veinlet- and breccia-style mineralization at the contact zone, whereas porphyry mineralization is characterized as disseminated and veinlet-style only. Various types of fluid inclusions (daughter mineral-bearing, CO2-bearing, vapor and aqueous–vapor) are classified based on their fluid composition and phase assemblages.The hydrothermal fluids are mainly derived from a magmatic origin, which exsolves during the melt-fluid differentiation. Primary fluid in endoskarn is interpreted as representing two immiscible phases evolving from a low-salinity initial fluid. The initial supersaturated fluid has a relative low salinity and the wide range of Thvalues (433–626 °C) implies heterogeneous trapping, corresponding to pressures of 371–646 bars and hydrostatic depth of 3.7–6.5 km. Primary fluid inclusions trapped in syn-ore quartz show the coexistence of S-type inclusions (~30.0 wt% NaCl equiv) with vapor-rich and liquid-rich inclusions, indicating fluid immiscibility and phase separation from heterogeneous trapping. The homogenization temperatures (347–434 °C) of primary vapor-rich inclusions represent the trapping temperatures, corresponding the trapped pressures range from 152 to 374 bars and a hydrostatic depth of 1.5–3.7 km. Copper mineralization in episode porphyry occurs on a very small scale and have a clear trend of decreasing temperatures and salinities during fluid evolution. A similar scenario occurred during the porphyry episode in which fluid immiscibility led to copper mineralization.Significant trends of decreasing temperatures and salinities for both mineralization episodes reflect the change from a magmatic fluid-dominated system to a mixed source fluid that incorporated formation water from the country rocks and/or meteoric water. Controlled by the chemical transition of the fluid, this mixing process produced a relatively cool fluid system with lower salinities, which enhanced the precipitation of Cu–Fe sulfides. H–O–C isotope signatures further indicate that both the fluid and metal are predominantly derived from magmatic sources, and that multiple fluid pulses contributed to form skarn minerals and sulfides in the Wushan deposit.
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影响因子：
3.5
作者：
A. Kerkhof;U. Hein
通讯作者：
A. Kerkhof;U. Hein
影响因子：
5
作者：
J. Lynch;F. Longstaffe;B. Nesbitt
通讯作者：
J. Lynch;F. Longstaffe;B. Nesbitt
影响因子：
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作者：
S. Sheppard
通讯作者：
S. Sheppard
影响因子：
3.1
作者：
P. E. Brown
通讯作者：
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影响因子：
12.1
作者：
Baker, D. R.;Alletti, M.
通讯作者：
Alletti, M.