河南瓦房铅锌矿床地质、流体包裹体和稳定同位素特征

河南瓦房铅锌矿床位于华北克拉通南缘熊耳山—外方山矿集区,矿体赋存于熊耳群鸡蛋坪组上段(Chj3)的地层中,矿石矿物有黄铁矿、方铅矿、闪锌矿和少量黄铜矿、赤铁矿、褐铁矿。该矿床热液成矿过程划分为3个阶段:石英-黄铁矿阶段(早阶段),石英-多金属阶段(中阶段),石英-碳酸盐脉阶段(晚阶段)。矿石中石英和方解石中捕获的原生包裹体类型有NaCl-H2O型两相、NaCl-CO2-H2O型三相和纯气相。气液两相包裹体3个阶段均一温度范围分别为150~260、150~230和110~160℃,3个阶段盐度(w(NaCl))平均值分别为12.22%、8.55%和6.29%。中阶段方解石的δ13 CVPDB平均值为-7.34‰,δ18 OSMOM平均值为15.56‰;晚阶段方解石的δ13 CVPDB平均值为-3.05‰,δ18 OSMOW平均值为2.21‰。早阶段硫化物的δ34S值为2.747‰~7.737‰,中阶段硫化物的δ34S值为-11.187‰~7.286‰。认为早中阶段成矿流体为变质流体,与中生代扬子克拉通和华北克拉通发生陆陆碰撞诱发中—新元古代时期的俯冲板片变质脱水有关,成矿晚阶段流体有大气降水的混入。硫同位素表明硫来源于中—新元古代的沉积地层,是海相硫酸盐的还原产物,在晚阶段,由于大气降水的混入导致δ34S出现负值。瓦房铅锌矿床地质特征、成矿流体特征与造山型矿床相似,因此,瓦房铅锌矿床属于造山型铅锌矿床。

Characteristics of Geology,Fluid Inclusions and Stable Isotope of Wafang Pb-Zn Deposit in Henan

Wafang Pb-Zn deposit is located in the Xiong'er-Waifang Mountains of the southern margin of the North China craton.The ore bodies are existed in the upper Jidanping Formation of Xiong'er Group,and the ore minerals are pyrite,galena,sphalerite and little chalcopyrite,limonite,and hematite.The hydrothermal ore-forming processes are divided into three stages:quartz-pyrite stage (early stage),quartz-polymetal stage (middlestage),and quartz-carbonate vein stage (late stage).The fluid inclusions in quartz and calcite of ores are NaCl-H2O two-phase,NaCl-CO2-H2O three-phase,and pure gas.The homogeneous temperatures the two-phase inclusions in the three stages are 150-260 ℃,150-230 ℃ and 110-160 ℃,respectively.The average salinity w(NaCl) in the three stages are 12.22％,8.55 ％,6.29 ％,respectively.The δ13CVPDB and δ18 OSMOW of the calcites of the middle stage are high withthe mean of-7.34‰ and 15.56‰,respectively,showing the characteristics of freshwater carbonate.The δ13 CVPDB and δ18 OSMOW of the late stage are at an average of-3.05‰ and 2.21‰,respectively.The δ34S values of sulfides in the early and middle stages are 2.747‰-7.737‰ and -11.187‰-7.286‰,respectively.We conclude that the ore-forming fluid in the early and middle stages was metamorphic fluid,which was related to the metamorphic dehydration of the Meso-Neoproterozoic slab subduction during Mesozoic continental collision between Yangtze and North China craton,then mixed with meteoric water in the late stage.The S isotope indicates that sulfur was derived from Meso-Neoproterozoic sedimentary stratigraphy by the reduction of marine sulfate.In the middle and late stages,negative δ34S values occurred due to the mixing with meteoric waters.The characteristics of geology and ore-forming fluid in Wafang Pb-Zn deposit are similar to orogenic deposits.