投稿时间：2017-07-15
修订日期：2018-02-22
网络发布日期：2018-04-25
中文摘要:河南省老里湾银铅锌矿床位于华北克拉通南缘华熊地块崤山断隆区，是近年来在崤山东部浅覆盖区新发现的一处大型矿床。老里湾矿床的矿体受断裂构造控制，主要呈浸染状、细脉浸染状和脉状赋存于早白垩世花岗斑岩体内的NW向和NNW向断裂破碎带中，亦有少量的矿体产于中元古界熊耳群火山岩内的断裂中。根据矿物共生组合、矿石组构及脉体穿插关系，将老里湾银铅锌矿床的成矿过程划分为3个成矿阶段，即：①绢云母+闪锌矿+方铅矿+黄铁矿阶段（早阶段）；②重晶石+闪锌矿+方铅矿+银矿物±碳酸盐±石英阶段（中阶段）；③闪锌矿+方铅矿+银矿物阶段（晚阶段）。文章对花岗斑岩的石英斑晶和热液阶段重晶石流体包裹体的研究表明，石英斑晶中主要发育含子矿物多相包裹体（S型）、富液两相水溶液包裹体（WL型）及少量的富气两相水溶液包裹体（WG型）；重晶石中主要发育WL型包裹体。花岗斑岩的石英斑晶中包裹体完全均一温度介于338~586℃，平均494℃；盐度w（NaCleq）介于11.0%~70.2%，密度为0.87~1.27 g/cm3，属于高温、高盐度的H2O-NaCl体系。成矿中阶段的重晶石中包裹体均一温度为128~401℃，平均254℃；盐度w（NaCleq）为1.6%~8.1%，密度0.59~0.95 g/cm3，属于中温、低盐度的H2O-NaCl体系。成矿中阶段重晶石中流体的δ18O水值介于5.9‰~8.4‰，δDV-SMOW值介于-89.7‰~-65.5‰，表明成矿流体为岩浆水。重晶石的δ13CPDB变化于-22.9‰~-12.5‰，具有花岗质岩浆演化形成的流体特征。矿石金属硫化物的δ34S值介于1.9‰~5.9‰，平均3.5‰，具有深源硫的特征；成矿阶段重晶石的δ34S值介于9.2‰~11.1‰，平均10.2‰。重晶石的δ34S值大于硫化物的δ34S值，是同位素分馏造成的。矿床金属硫化物的Pb同位素组成较为集中，206Pb/204Pb介于17.262~17.430；207Pb/204Pb介于15.444~15.501；208Pb/204Pb介于37.774~38.050。S-Pb同位素组成表明老里湾矿床的成矿物质主要来自矿区内的早白垩世花岗质岩浆。崤山东部发育斑岩型钼铅锌银成矿系统，老里湾银铅锌矿床属于该成矿系统的浅部脉状矿化端员。初始中低盐度流体的降温是老里湾银铅锌矿床矿质沉淀的主要机制。
Abstract:The Laoliwan deposit, located in western Henan Province, is a newly discovered large silver-lead-zinc deposit in the Xiaoshan uplift of the Huaxiong block on the southern margin of the North China craton. Orebodies of the deposit are composed of disseminated, veinlet disseminated, and vein-type ores. Most of the orebodies are hosted in NW-and NNW-extending faults developed in the Early Cretaceous granite porphyry, with a small amount of orebodies occurring within NW-and NNW-extending faults developed in the Xiong'er Group. The ore-forming process in the deposit can be divided into three stages according to the mineral association, ore fabric, and vein body interpenetration:① sericite+sphalerite+galena+pyrite stage (early stage); ② barite+sphalerite+galena+silver mineral±carbonate±quartz stage (middle stage); and ③sphalerite+galena+silver mineral stage (late stage). Three types of fluid inclusions (FIs) have been distinguished in quartz phenocryst of granite porphyry and barite of hydrothermal stage, i.e., liquid-rich (WL type), gas-rich (WG type), and daughter mineral-bearing (S type) inclusions. The FIs in quartz phenocrysts of the granite porphyry are composed of WL-, WG-, and S-types, their homogenization temperature, w(NaCleq), and density vary from 338℃ to 586℃(494℃ on average), 11.0% to 70.2%, and 0.87 g/cm3 to 1.27 g/cm3, respectively, and fluid in this stage generally belongs to the H2O-NaCl system with high temperature and high salinity. The FIs in barite of the middle stage only consist of WL-type, their homogenization temperature, w(NaCleq), and density vary from 128℃ to 401℃ (254℃ on average), 1.6% to 8.1%, and 0.59 g/cm3 to 0.95 g/cm3, respectively, and the fluid in this stage generally belongs to the H2O-NaCl system with medium temperature and low salinity. The ore-forming fluid of the Laoliwan deposit is a medium temperature and low salinity fluid, which belongs to the H2O-NaCl system. The δ18OH2O and δDH2O values of ore-forming fluids in the middle stage vary from 5.9‰ to 8.4‰ and -89.7‰ to -65.5‰, respectively, indicating that the ore-forming fluids mainly originated from magma. The δ13C values of barite vary from -22.9‰ to -12.5‰, consistent with the δ13C values of evolutional granitic magma, which implies that the ore-forming fluids mainly originated from magma. The δ34S values of metal sulfides from the ore range from 1.9‰ to 5.9‰ with an average of 3.5‰, which reveals the characteristics of deep source sulfur. the δ34S values of barite from the middle stage vary between 9.2‰ and 11.1‰ with an average of 10.2‰, higher than the values of the metal sulfides, implying that sulfur isotope experienced fractionation during the mineralization. The lead isotope composition of metal sulfides is relatively concentrated, and their 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios vary from 17.262 to 17.430, 15.444 to 15.501, and 37.774 to 38.050, respectively. Both S and Pb isotopes indicate that the ore-forming materials of the Laoliwan deposit chiefly originated from the Early Cretaceous granitic magma. Porphyry ore-forming system exists in western Xiaoshan, and the Laoliwan Ag-Pb-Zn deposit belongs to shallow vein-type mineralization of the ore-forming system. The cooling of the initial medium-low salinity ore-forming fluids was the dominant mechanism for precipitation of Ag, Pb, and Zn in the Laoliwan deposit.
keywords:geology fluid inclusion H-O-C-S-Pb isotopes porphyry ore-forming system hydrothermal vein-type Ag-Pb-Zn deposit Laoliwan western Henan Province
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基金项目:河南省国土资源厅省"两权价款"地质科研项目（编号：豫国土资函[2016]106号-01）和中国地质调查局中国矿产地质与成矿规律综合集成和服务（矿产地质志）项目（编号：DD20160346）资助
引用文本：
常云真,裴海洋,范海洋,赵康,王中杰.2018.豫西老里湾银铅锌矿床流体包裹体和同位素特征及其地质意义[J].矿床地质,37(2):246~268CHANG YunZhen,PEI HaiYang,FAN HaiYang,ZHAO Kang,WANG ZhongJie.2018.Fluid inclusion study and isotopic characteristics of Laoliwan Ag-Pb-Zn deposit in western Henan Province[J].Mineral Deposits37(2):246~268
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