浙江省罗山岭头金银矿床地质特征和成矿机制研究

发布时间：2018-05-16 03:28

  本文选题：罗山金银矿床 + 侵入岩　； 参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：浙中东阳地区罗山金银矿床位于江绍断裂带和丽水-余姚断裂带之间、陈蔡-遂昌隆起带北东侧,次级构造芙蓉山破火山口的南东侧。论文在总结前人工作基础上,对罗山金银矿床的矿床地质特征、成矿流体、岩石地球化学、成矿年代学等方面进行了研究,并探讨了罗山金银矿床的成因类型,建立了成矿模式。矿床赋存在新元古界基底陈蔡群变质岩及混合岩中,主要受NE-NEE向构造裂隙控制;矿体主要呈脉状产出,倾向呈SE、SSE,倾角在60-80°;主要矿石类型为石英脉型,发育低温蚀变类型,如硅化、绢云母化和碳酸盐化等。矿区脉岩广布,与矿床空间和成因皆有紧密联系,矿区中酸性侵入岩为过铝质高钾钙碱质系列岩石,稀土配分曲线上,轻稀土富集,负Eu异常较明显,微量元素蛛网图显示“TNT”异常,表现为俯冲带形成的岛弧型火山岩特征,侵入岩为热液成矿提供了成矿物质和热源。根据野外观察可以将主成矿期划分三个成矿阶段:黄铁矿-石英阶段;石英-多金属硫化物阶段;石英-碳酸盐阶段。石英-多金属硫化物阶段为矿床主成矿阶段。矿石石英流体包裹体类型以富液相包裹体为主,缺乏含CO2和含子晶包裹体,均一温度集中在140~220℃,流体盐度为0.70~5.26%(Na Cleq),密度为0.738~0.955g/cm3,成矿压力为62.58~110.05 bar,成矿深度为0.23~0.53km,流体性质跟浅成低温热液型相似,为低温低盐度低密度流体,成矿流体以古大气降水为主;矿石铅同位素在208Pb/204Pb-206Pb/204Pb图上主要表现为造山带(岛弧)壳幔混合铅,并结合前人资料,可以得出成矿物质主要来自基底变质岩及混合岩的结论;硫同位素特征显示成矿物质为深源(下地壳或上地幔)。对矿区侵入岩做了系统的LA-ICP-MS U-Pb同位素年龄测定:辉绿玢岩的成岩年龄为129~130Ma,花岗斑岩的成岩年龄为154.9±2.9Ma,石英斑岩的成岩年龄为131.2±3.3Ma,混合岩年龄为230.1±2.4Ma,根据脉岩与矿体的空间关系和成因联系,推测矿床成矿时代为:129~230Ma。矿床总体表现为浅成低温热液金银矿床。
[Abstract]:The Luoshan gold and silver deposit in Dongyang area of central Zhejiang is located between Jiangshao fault zone and Lishui-Yuyao fault zone east of Chen Cai-Suichang uplift belt and south of the crater of secondary structure Furongshan crater. On the basis of summarizing the previous work, this paper studies the geological characteristics, ore-forming fluid, petrogeochemistry, metallogenic chronology of the Luoshan gold and silver deposit, and discusses the genetic types of the Luoshan gold and silver deposit. A metallogenic model was established. The deposit occurs in the metamorphic rocks and migmatites of the Chencai Group in the Neoproterozoic basement, which is mainly controlled by the NE-NEE trending structural fissures, the orebody is mainly vein-like, tends to be SESSE with a dip angle of 60-80 掳, and the main ore type is quartz vein type, which develops low temperature alteration type. For example, silicification, sericite and carbonization. Dikes are widely distributed in the ore area and are closely related to the space and genesis of the deposit. The intermediate-acid intrusive rocks in the ore area are peraluminous, high-potassium, calc-alkali series rocks. On the rare earth distribution curve, the REE is enriched with LREE, and the negative EU anomaly is obvious. The trace element cobweb shows "TNT" anomaly, which is characterized by island arc volcanic rocks formed in subduction zone, and intrusive rocks provide ore-forming material and heat source for hydrothermal mineralization. According to field observation, the main metallogenic stage can be divided into three stages: pyrite-quartz stage, quartz-polymetallic sulfide stage, quartz-carbonate stage. The quartz-polymetallic sulfide stage is the main metallogenic stage of the deposit. The types of fluid inclusions in quartz ores are mainly rich liquid inclusions, lacking of CO2 and subcrystalline inclusions, and the homogenization temperature is concentrated at 140 ~ 220 鈩，

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