The extensive Changba‐Lijiagou Pb‐Zn deposit is located in the north of the Xihe–Chengxian ore cluster in West Qinling. The ore bodies are mainly hosted in the marble, dolomitic marble and biotite‐calcite‐quartz schist of the Middle Devonian Anjiacha Formation, and are structurally controlled by the fault and anticline. The ore‐forming process can be divided into three main stages, based on field geological features and mineral assemblages. The mineral assemblages of hydrothermal stage I are pale‐yellow coarse grain, low Fe sphalerite, pyrite with pits, barite and biotite. The mineral assemblages of hydrothermal stage II are black‐brown cryptocrystalline, high Fe shalerite, pyrite without pits, marcasite or arsenopyrite replace the pyrite with pits, K‐feldspar. The features of hydrothermal stage III are calcite‐quartz‐sulfide vein cutting the laminated, banded ore body. Forty‐two sulfur isotope analyses, twenty‐five lead isotope analyses and nineteen carbon and oxygen isotope analyses were determined on sphalerite, pyrite, galena and calcite. The δ³⁴S values of stage I (20.3 to 29.0‰) are consistent with the δ³⁴S of sulfate (barite) in the stratum. Combined with geological feature, inclusion characteristics and EPMA data, we propose that TSR has played a key role in the formation of the sulfides in stage I. The δ³⁴S values of stage II sphalerite and pyrite (15.1 to 23.0‰) are between sulfides in the host rock, magmatic sulfur and the sulfate (barite) in the stratum. This result suggests that multiple S reservoirs were the sources for S^2– in stage II. The δ³⁴S values of stage III (13.1 to 22‰) combined with the structure of the geological and mineral features suggest a magmatic hydrothermal origin of the mineralization. The lead isotope compositions of the sulfides have ²⁰⁶Pb/²⁰⁴Pb ranging from 17.9480 to 17.9782, ²⁰⁷Pb/²⁰⁴Pb ranging from 15.611 to 15.622, and ²⁰⁸Pb/²⁰⁴Pb ranging from 38.1368 to 38.1691 in the three ore‐forming stages. The narrow and symmetric distributions of the lead isotope values reflect homogenization of granite and mantle sources before the Pb‐Zn mineralization. The δ¹³C_PDB and δ¹⁸O_SMOW values of stage I range from –0.1 to 2.4‰ and from 18.8 to 21.7‰. The values and inclusion data indicate that the source of fluids in stage I was the dissolution of marine carbonate. The δ¹³C_PDB and δ¹⁸O_SMOW values of stage II range from –4 to 1‰ and from 12.3 to 20.3‰, suggesting multiple C‐O reservoirs in the Changba deposit and the addition of mantle‐source fluid to the system. The values in stage III are –3.1‰ and 19.7‰, respectively. We infer that the process of mineralization involved evaporitic salt and sedimentary organic‐bearing units interacting through thermochemical sulfate reduction through the isotopic, mineralogy and inclusion evidences. Subsequently, the geology feature, mineral assemblages, EPMA data and isotopic values support the conclusion that the ore‐forming hydrothermal fluids were mixed with magmatic hydrothermal fluids and forming the massive dark sphalerite, then yielding the calcite‐quartz‐sulfide vein ore type at the last stage. The genesis of this ore deposit was epigenetic rather than the previously‐proposed sedimentary‐exhalative (SEDEX) type.

中文翻译：

---

中西部西秦岭长坝-李家沟铅锌矿床的成因：S-Pb-C-O同位素的约束

广泛的昌巴—李家沟铅锌矿床位于西秦岭西河—承县矿石群的北部。矿体主要存在于中泥盆纪安家岔组的大理石，白云岩大理石和黑云母方解石-石英片岩中，并受断层和背斜的控制。根据矿场的地质特征和矿物组合，成矿过程可分为三个主要阶段。热液阶段I的矿物组合为浅黄色粗粒，低铁闪锌矿，带矿的黄铁矿，重晶石和黑云母。热液阶段II的矿物组合为黑褐色隐晶质，高铁锰铁矿，无矿的黄铁矿，镁铁矿或毒砂代替有矿的黄铁矿，钾长石。水热阶段III的特征是方解石-石英-硫化物脉状切割层状带状矿体。在闪锌矿，黄铁矿，方铅矿和方解石上确定了42个硫同位素分析，25个铅同位素分析以及19个碳和氧同位素分析。的δ ^34个阶段的价值观I（20.3至29.0‰）是与所述一致的δ ^34个在地层硫酸盐的S（重晶石）。与地质特征，包括特征和EPMA数据相结合，我们建议，TSR已在硫化物的形成阶段中起到了关键作用I的δ ³⁴ II阶段闪锌矿和黄铁矿（15.1〜23.0‰）的S值在硫化物之间在主体岩石中，岩浆中的硫和硫酸盐（重晶石）在地层中。该结果表明，在第二阶段中，多个S储层是S ^{2 –}的来源。的δ ³⁴第三阶段的S值（13.1至22‰）与地质和矿物特征的结构相结合，暗示了成矿作用的岩浆热液成因。在三个成矿阶段，硫化物的铅同位素组成分别为²⁰⁶ Pb / ²⁰⁴ Pb（范围从17.9480至17.9782），²⁰⁷ Pb / ²⁰⁴ Pb（范围从15.611至15.622）和²⁰⁸ Pb / ²⁰⁴ Pb（范围从38.1368至38.1691）。铅同位素值的狭窄和对称分布反映了Pb-Zn矿化之前花岗岩和地幔源的均质化。的δ ¹³ C ^ _PDB和δ ¹⁸ ö _SMOW第一阶段的值范围为-0.1至2.4‰和18.8至21.7‰。数值和包裹体数据表明，第一阶段的流体来源是海相碳酸盐的溶解。的δ ¹³ C ^ _PDB和δ ¹⁸ ö _SMOW第二阶段的取值范围为–4到1‰和12.3到20.3‰，表明长坝矿床中有多个C-O储层，并向系统中添加了地幔源流体。第三阶段的值分别为–3.1‰和19.7‰。我们推断成矿过程涉及蒸发盐和含沉积有机物的单元，这些同位素通过同位素，矿物学和包裹体证据通过热化学硫酸盐还原作用相互作用。随后，地质特征，矿物组合，EPMA数据和同位素值支持了以下结论：成矿热液与岩浆热液混合并形成块状深色闪锌矿，然后在该处生成方解石-石英-硫化物脉状矿石类型。末期。