河南冷水北沟铅锌银矿床流体包裹体研究及矿床成因  

Fluid inclusion constraints on the origin of the Lengshuibeigou Pb-Zn-Ag deposit,Henan province

作　　者：祁进平[1] 陈衍景[1] 倪培[2] 赖勇[3] 丁俊英[2] 宋要武[4] 唐国军[3] 

机构地区：[1]中国科学院广州地球化学研究所成矿动力学重点实验室,广州510640 [2]南京大学内生矿床国家重点实验室,南京210093 [3]北京大学造山带与地壳演化实验室,北京100871 [4]河南省地质调查院,郑州450007

出　　处：《岩石学报》2007年第9期2119-2130,共12页Acta Petrologica Sinica

基　　金：国家973项目2006CB4035008和2006CB403504课题;自然科学基金项目(编号40425006和40352003);中国博士后科学基金(编号20060400768)

摘　　要：河南栾川冷水北沟铅锌银矿床位于华北克拉通南界栾川断裂北侧。矿床赋存于中-晚元古代浅变质碎屑岩建造中,受断裂控制,矿体呈脉状;矿石主要由金属硫化物,少量石英和碳酸盐组成;围岩蚀变和成矿过程分为4个阶段,以石英- 黄铁矿组合(Ⅰ阶段)、黄铁矿-闪锌矿组合(Ⅱ阶段)、多金属硫化物(Ⅲ阶段)和碳酸盐(Ⅳ阶段)为标志。包裹体研究表明,成矿流体为含 CH_4的碳水体系,盐度为0.22～13.8 wt% NaCl eqv.。从早到晚,流体包裹体均一温度为420℃～340℃(Ⅰ)、370℃～280℃(Ⅱ)、320℃～260℃(Ⅲ)和<260℃(Ⅳ)。Ⅰ、Ⅱ阶段的流体盐度低于8 wt% NaCl eqv.,Ⅲ阶段增高至13.8 wt%NaCl eqv.,甚至偶见子晶。Ⅰ、Ⅱ阶段的流体包裹体均一压力分为两组,即180～200MPa 和70～80MPa,代表着深约8km 的静水与静岩压力系统的共存或交替;Ⅲ阶段只有70～80MPa 一组压力,指示开放环境注入的静水压力体系。Ⅰ、Ⅱ阶段静岩与静水压力系统的交替现象完全吻合于断层阀模式,含 CH_4的 CO_2-H_O 流体的脉动沸腾消耗了流体成矿系统热能,并使盐度不断增高、成矿。该认识可被Ⅱ阶段广泛存在的沸腾流体包裹体组合证明,也与流体包裹体成分类型、矿物共生组合特征、矿石组构的规律演化相一致。以上表明,冷水北沟是一个典型的形成于碰撞造山挤压向伸展转变期的造山型 Pb-Zn-Ag 矿床实例,成矿机理可由碰撞造山成岩成矿与流体作用模型(即 CMF 模式)所解释。The Lengshuibeigou Pb-Zn-Ag deposit in Henan province is located to the north of the Luanchuan fault along the southern margin of North China craton. The deposit is a fault-controlled vein-type deposit, hosted by Meso-Neoproterozoic strata. The ores consist of sulfides and a small amount of quartz and carbonates. Ore-forming process includes four stages marked by four kinds of parageneses ： quartz-pyrite stage （ Ⅰ ） pyrite-sphalerite stage （ Ⅱ ） , polymetallic sulfide stage （Ⅲ ） , and carbonate stage （ Ⅳ ）. Microthermometric data of fluid inclusions indicate that ore-forming fluids are CO2 ± CH4-H2O system, characterized by low salinities of 0.22 - 13.8 wt% NaCl eqv. From early to late the homogeneous temperatures of fluid inclusions decrease from 420℃ - 340℃（ stage Ⅰ）, through 370℃ - 280℃ （ stage Ⅱ） , to 320℃ ~ 260 ℃ （Ⅲ） , and to 〈 260℃ （ stage Ⅳ）. The salinities of stages I and II fluids are lower than 8wt% NaCl eqv. The salinities of stage III fluids are up to 13.8wt% NaCl eqv, and with daughter crystals can be occasionally observed. Fluid inclusions of both stages I and II yield two group of homogeneous pressures, i.e. 70 - 80MPa and 180 - 200MPa, which can be interpreted to represent alternating between hydrostatic and lithostatic fluid-systems at the depth of ca. 8 km, possibly related to fault-valve activities. The fluid inclusions of stage III yield only one group of 70 - 80MPa, suggesting an open-space filling hydrostatic fluid-system. The characteristic of alternating lithostatic and hydrostatic pressures during stages I and II is extremely analogous to the fault-vavle model. Pulsative fluid boiling of CH4-bearing CO2-rich fluids gradually release heat and increase the salinities of the fluid system. This is strongly supported by the observations of boiling fluid inclusions in stage II minerals, and by the regularly evolved compositional types of fluid inclusions, mineralogical parageneses and ore fabrics. All the above suggest that the

关 键 词：冷水北沟铅锌银矿床 流体包裹体 成矿流体 造山型铅锌银矿床 秦岭造山带 

分 类 号：P618.4[天文地球—矿床学] P618.52[天文地球—地质学]