CAJ | 학술논문

多才玛超大型铅锌矿床位于青藏高原东北部北羌塘地块,受NW向断裂构造的控制,矿体呈脉状、透镜状,赋矿围岩为二叠系九十道班组灰岩,矿石为浸染状、角砾状、块状和网脉状构造,矿石矿物组成简单,金属矿物主要有方铅矿、闪锌矿、黄铁矿,脉石矿物主要有方解石、白云石、重晶石、石英。在野外地质观察基础上,对脉石矿物进行了显微观察及包裹体测温研究,结果表明：矿石中方解石和石英中所捕获的原生流体包裹体有气液两相包裹体、富气体气液两相包裹体、纯气体包裹体3种类型,邻近分布,其均一温度相近；脉石矿物的流体包裹体主要以气液相包裹体居多,其他两类次之；包裹体测温结果显示,成矿流体冰点温度为-19.3~-0.5℃,均一温度变化范围为97~497℃,峰值范围为120~180℃；流体盐度变化范围为0.9%~21.9%NaCleq,平均盐度9.2%NaCleq；大部分包裹体流体密度为0.7~1.00 g/cm3,平均密度0.94 g/cm3；估算的成矿压力为5~10 MPa,对应成矿深度为0.5~1 km之间。成矿流体呈低温、中低盐度、中等密度、低压、浅成相的矿床成矿环境特征。结合区域成矿背景、矿床地质和流体包裹体特征,认为多才玛铅锌矿床为造山逆冲推覆带背景下的MVT型铅锌矿床。
다재마초대형연자광상위우청장고원동북부북강당지괴,수NW향단렬구조적공제,광체정맥상、투경상,부광위암위이첩계구십도반조회암,광석위침염상、각력상、괴상화망맥상구조,광석광물조성간단,금속광물주요유방연광、섬자광、황철광,맥석광물주요유방해석、백운석、중정석、석영。재야외지질관찰기출상,대맥석광물진행료현미관찰급포과체측온연구,결과표명：광석중방해석화석영중소포획적원생류체포과체유기액량상포과체、부기체기액량상포과체、순기체포과체3충류형,린근분포,기균일온도상근；맥석광물적류체포과체주요이기액상포과체거다,기타량류차지；포과체측온결과현시,성광류체빙점온도위-19.3~-0.5℃,균일온도변화범위위97~497℃,봉치범위위120~180℃；류체염도변화범위위0.9%~21.9%NaCleq,평균염도9.2%NaCleq；대부분포과체류체밀도위0.7~1.00 g/cm3,평균밀도0.94 g/cm3；고산적성광압력위5~10 MPa,대응성광심도위0.5~1 km지간。성광류체정저온、중저염도、중등밀도、저압、천성상적광상성광배경특정。결합구역성광배경、광상지질화류체포과체특정,인위다재마연자광상위조산역충추복대배경하적MVT형연자광상。
The Duocaima ultra-large-scale Pb-Zn deposit is located in the northern Qiangtang terrane of the northeastern Qinghai-Tibetan Plateau, in-between the Kekexili-Jinsha River and Longmucuo-Shuanghu-Lancang River suture zones. The Duocaima Pb-Zn deposit is controlled by NW-trending fault structure, whose ore bodies are vein-like and lenticular. The ore-hosting rocks are the Permian limestone of the Jiushidaoban Formation. The ore mineral assemblage is simple, which commonly show structures such as disseminated, brecciated, lumpy and vein-like types. The metallic minerals mainly consist of galena, sphalerite and pyrite, and the gangue minerals mainly consist of calcite, dolomite, barite and quartz. On the basis of field geological observation, we have carried out inclusion temperature study on the gangue minerals. The primary fluid inclusions trapped in calcite and quartz can be divided into three types, i.e., gas-liquid phase inclusion, gas-rich gas-liquid phase inclusion and pure gas inclusion. The three types of inclusions are commonly concurrence and have similar homogenization temperatures. The gas-liquid phase inclusion is the major type of fluid inclusions of in the gangue minerals. The results of inclusion temperature show that the freezing point temperature of ore-forming fluid is–19.3––0.5 ℃ and the homogenization temperature vary in range of 97–497 ℃ with peak range of 120–180 ℃. The fluid salinity vary from 0.9%to 21.9%NaCleq with an average of 9.2%NaCleq. The fluid density is 0.70–1.00 g/cm3 and the average density is 0.94 g/cm3. The estimated ore-forming pressure is 5–10 MPa, corresponding to depth of 0.5–1 km. The characteristics of the ore-forming fluid show that the ore mineralization was took place under shallow depth via ore-forming fluids of low temperature, low salinity, and middle density. Combining with the characteristics of regional ore-forming background, deposits geology and fluid inclusion, we propose that the Duocaima Pb-Zn deposit is a MVT Pb-Zn deposit formed in the orogenic thrust-nappe belt.