青海锡铁山铅锌矿矿床成因研究-资源勘查工程毕业论文

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 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 divided 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 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 represent unerupted sub-seafloor fluid activity. Fluids in altered stockwork rocks and carbonates have similar H2O-NaCl-CO2system and higher temperature,both belonging to the sedimentary-exhalative system.The fluids migrate from the pipe facies to the unstratified ore badies.The homogenization temperature 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 fluid 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 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 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