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1、青海锡铁山铅锌矿矿床成因研究Study on genesis of Xitieshan lead-zinc deposit, in Qinghai Province摘 要锡铁山铅锌矿床产于青海省柴达木盆地北缘早古生代烈焰的中基性火山-沉积岩系中，发育一套完整的喷流沉积系统，包括管道相，近喷口相以及喷流沉积相，是我国规模最大的铅锌矿床之一。矿体中产有非层状和层状矿体两类矿体，其中非层状矿体铅锌矿体呈不规则状产于大理岩中，是锡铁山矿床的主要矿体类型，非层状矿体产于大理岩边部，规模较小。本文的成矿流体初步研究表明，代表喷流管道相的网脉状蚀变岩的温度，盐度范围非常宽，多期次的流体活动强烈，具有喷流系统
2、管道相的明显特征。代表近喷口相的产于厚层状大理岩中的非层状铅锌矿体旁侧的碳酸盐中包裹体个体大，温度高，亦有明显的形成于未喷出海底的中-高温热液活动特征。碳酸盐（大理岩）与网脉状蚀变岩有相同的H2O-NaCl-CO2流体类型，温度稍低，流体从管道相流向非层状矿体，具有继承性。层状矿体流体的均一温度及冷冻温度范围与非层状矿体基本相同。流体包裹体的温度、盐度、气液相成分测试以及同位素组地球化学研究证明锡铁山矿床形成于喷流沉积系统。管道相成矿流体以深源为主，深源流体的CO2等气相组分溢出及深源流体与海水的混合作用导致了成矿物质沉淀。结合成矿模式认为，矿床铅同位素具有造山带与上地壳混合来源的特点。显示喷
3、流成矿过程中铅及成矿金属物质主要有喷流卤水提供，少量物质来源于海水。层状矿体与非层状矿体均属于形成于喷流沉积过程，非层状矿体属未喷出海底的热液矿体。关键词矿床地质特征；流体包裹体；同位素特征；喷流沉积型；锡铁山铅锌矿Abstract The Xitieshan lead-zine deposit in Qinghai Province,China occurs in an Early Paleozoic sequence of intermediate-basic volcanic rocks and sediments developed in the northern margin of
4、the Qaidam basin,It has been recognized that there is a complete exhalation sedimentary system that includes breccias pipe-stockwork,non-bedded andbedded ores and marble from exhalation sediments.It is one of the biggest lead-zine dsposits in China.The lead-zine orebody contained in marble can be di
5、vided into two types, i.e. unstratified and bedded ones. The unstratfied orebody occurs unconformably in the main orebody.Our preliminary study of ore-forming fluids shows that fluid inclusions is quartz form altered stockwork rocks that represent the pipe facies have a wide range of temperature and
6、 salinity.The intense fluid activities are characteristics of the pipe facies of the exhalative system.Fluid inclusions in carbonates near the unstratified ore badies hosted in thickbedded marble which represents vent-proxinmal facies are large in size and have moderate to high temperature.they repr
7、esent unerupted sub-seafloor fluid activity. Fluids in altered stockwork rocks and carbonates have similar H2O-NaCl-CO2 system and higher temperature,both belonging to the sedimentary-exhalative system.The fluids migrate from the pipe facies to the unstratified ore badies.The homogenization temperat
8、ure and freezing temperature of sluid inclusions from stratifid ore bodies are similar with unstatified ore bodis,but lack the inclusions of great gas/liquid ratio and containing daughter minrals and CO2 component in fluid and the homogenization temperature is slightly lower .That is to say their fl
9、uid is continuum.The deposit is evidenced an sedimentary exhalative on system by isotope geochemical study and fluid in feeders were deeply sourced.Escape of deeply-sourced gaseous componnts such as CO2 and mixing of deely-sourced fluids with seawater caused precipitation of ore-forming materials. A
10、 study of Pb isotope geochemistry suggests that the first array, consisting of most of the ore samples, represents a two-component mixing line in which the less radiogenic component can be identified as orogenic lead reservoir probably coming from Tianjianshan Group through the exhalation brine. The
11、 radiogenic end-member can be identified as upper crust lead reservoir probably derived from seawater.Keywords： Geological-features; Fluid inclusions; Isotopic characteriestics; Sedimentary-exhalative type; Xitieshan lead zinc deposit目 录1 前言11.1 研究的目的及意义11.2 位置与交通、自然地理及经济状况11.2.1 位置与交通11.2.2 自然地理及经济
12、状况11.3 以往工作评述22 区域地质特征32.1 地层42.2 地质构造52.2.1 构造层划分52.2.2 褶皱构造62.2.3 断裂构造62.3 岩浆活动62.3.1 侵入岩62.3.2 火山岩62.4 区域地质演化72.5 区域物、化探特征82.5.1 区域航磁场特征82.5.2 区域布伽重力场特征82.5.3 区域化探特征82.6 区域矿产概括93 矿区及矿床地质、地球化学特征93.1 矿区地质特征93.1.1 地层93.1.2 构造113.1.3 岩浆岩133.2 矿床地质特征133.2.1 矿体特征143.2.2 矿石矿物组成、组构特征及矿石类型183.2.3 围岩蚀变特征21
13、3.2.4 矿化期次213.3 矿床地球化学特征223.3.1 硫同位素地球化学223.3.2 铅同位素地球化学特征234 锡铁山铅锌矿矿床流体包裹体研究264.1 流体包裹体岩相学特征264.2 显微测温结果264.3 流体成分测试284.4 氢氧同位素特征315 锡铁山铅锌矿矿床成因335.1 矿床类型335.1.1 矿床地质特征345.1.2 成矿流体特征345.2 成矿流体355.2.1 成矿流体的性质355.2.2 成矿流体的来源355.3 成矿物质365.3.1 硫同位素365.3.2 铅同位素375.4 成矿流体的演化与矿床成因38结论39参考文献40谢 辞41附录421 前言1
14、.1 研究的目的及意义研究目的：通过锡铁山铅锌矿矿床的矿床地质特征和成矿流体研究，探讨该矿床的成因，以期为进一步找矿提供科学依据。研究意义：随着我国社会经济的快速发展，对资源的消耗越来越快，铅锌矿是我国工业生产的重要原料之一，是人们生活必不可缺少的材料，有关矿床成因的正确认识，对于开采及寻找找下一个矿产基地，有重要的指导意义。本文通过锡铁山铅锌矿矿床的矿床地质特征、成矿流体及成矿物质来源的研究，探讨该矿床的成因，为矿床的开采和勘探以及为附近地区的找矿预测提供科学据。1.2 位置与交通、自然地理及经济状况1.2.1 位置与交通锡铁山地处柴达木盆地北缘优地槽褶皱带的南东段；北东以大柴旦乌兰深断裂为
15、界，与欧龙布鲁克山及宗务隆山褶皱带相邻；南西以残山山前壳层断裂带为界，与柴达木盆地新生代拗陷相接。属青海省海西蒙古族藏族自治州大柴旦镇所辖。锡铁山铅锌矿床东距西宁市699公里（铁路），南距格尔木市137公里，西北距大柴旦镇75公里。青藏铁路在矿区东南9公里处通过，有支线直达矿区，交通便利（图1-1）。1.2.2 自然地理及经济状况锡铁山铅锌矿床位于青藏高原腹地，南部是柴达木盆地的戈壁沙漠，属祁连山系南西的西铁山铅石山北西南东走向的山脉之中，山势陡峻，切割剧烈；海拔31003700米，属构造剥蚀U型冲沟地貌。区内干燥多风少雨，昼夜温差大，年均降雨量平均42.1毫米，年均蒸发量2151.1毫米，湿润系数0.038，气压低、年平均为0.68个大气压。最高气温35.5，最低气温-19.7，平均5.3。每年二至五月为风季，多为西北风，最大风速3.1米/秒。每年十月至翌年四月为冰冻期，最大冻土深度为1.72米。属典型的内陆沙漠性气候。图1-
