江西朱溪超大型钨矿成矿年代学及矿物学研究

发布时间：2018-02-14 23:57

本文关键词： 朱溪钨矿矽卡岩型矿床富氟流体榍石和磷灰石U-Pb定年稀土配分特　出处：《南京大学》2017年硕士论文　论文类型：学位论文

【摘要】：江西朱溪钨矿是一个近年新发现的超大型钨矿床,它位于于江南造山带的东部。朱溪矿区现已探明钨资源储量286万吨,超越之前报道106万吨储量的大湖塘钨矿,再次刷新了钨矿储量规模的世界记录,成为新的世界最大钨矿。朱溪世界级超大型钨矿床的发现对钨矿产资源开发和钨矿床研究均具有重要的意义。目前对于朱溪矽卡岩型白钨矿矿床的岩相学、矿物学的基础研究还比较薄弱,成矿年龄还没有精确的年代学数据约束。本文在总结前人研究的基础上,对朱溪钨矿矽卡岩矿物的矿物成分进行了分析,并且利用LA-ICP-MS对朱溪矿石中的榍石、磷灰石通过原位U-Pb定年方法获得了白钨矿的成矿年龄,对朱溪钨矿的成矿年龄和时代进行了探讨。朱溪钨矿矿体主要产于燕山期侵入岩与碳酸盐岩接触带的矽卡岩或矽卡岩化大理岩中。对钻孔采集到的花岗岩样品进行岩石地球化学研究表明,朱溪矿区黑云母花岗岩具有高硅、富碱,高分异的特征,属于钙碱性、过铝质花岗岩。黑云母花岗岩微量元素中Rb、U、Ta等元素富集,以及Ba、Nb、Sr和Ti等元素亏损。稀土元素总量偏低,轻稀土相对富集。根据矿物共生组合和交代关系,朱溪矽卡岩型白钨矿成矿划分为早矽卡岩阶段、晚矽卡岩阶段、石英硫化物阶段。矽卡岩矿物的电子探针分析结果表明,石榴子石主要为钙铝榴石-钙铁榴石端元组分;单斜辉石以透辉石-钙铁辉石系列为主。与白钨矿密切共生的矽卡岩矿物萤石、符山石、磷灰石和榍石为富氟的矿物,表明朱溪钨矿成矿流体为富氟体系,这有利于钨的运移和沉淀。利用LA-ICP-MS对白钨矿进行的原位分析,对朱溪钨矿中白钨矿中微量元素和稀土元素进行了详细的研究。根据白钨矿REE元素配分特征,将朱溪钨矿矿化划分为两个大的阶段,两个阶段成矿流体性质明显不同,所反应的环境也不同,第Ⅰ阶段环境为氧化环境,第Ⅱ阶段则是从还原环境过渡到氧化环境。第Ⅱ阶段应是主要成矿阶段,形成了朱溪钨矿的主体。总体上,朱溪矽卡岩型白钨矿呈现轻稀土富集的稀土配分模式,这可能是由于石榴子石等富集重稀土的矿物沉淀导致白钨矿重稀土的亏损。通过榍石原位LA-ICP-MS U-Pb定年测得成矿年龄为154±3Ma,磷灰石LA-ICP-MSU-Pb定年结果:137±9Ma～148± 16Ma,属于燕山期,与前人测得的成岩年龄在误差范围内基本一致,表明成矿作用与华南燕山期岩浆活动密切相关。
[Abstract]:The Zhuxi tungsten deposit in Jiangxi Province is a newly discovered super-large tungsten deposit in recent years. It is located in the eastern part of the Jiangnan orogenic belt. The Zhuxi mining area now has proven tungsten reserves of 2.86 million tons, surpassing the previously reported 1.06 million tons of Dahutang tungsten deposit. Set a new world record for the size of tungsten reserves, The discovery of Zhuxi world-class tungsten deposit is of great significance to the development of tungsten mineral resources and the study of tungsten deposit. The basic study of mineralogy is still weak, and the metallogenic age is not yet constrained by the exact chronological data. Based on the previous studies, the mineral composition of skarn minerals in Zhuxi tungsten deposit is analyzed in this paper. The metallogenic age of scheelite was obtained by in situ U-Pb dating of sphene and apatite from Zhuxi ore by LA-ICP-MS. The metallogenic age and age of Zhuxi tungsten deposit are discussed. The orebody of Zhuxi tungsten deposit mainly occurs in skarn or skarn marble in the contact zone between intrusive rocks and carbonate rocks in Yanshanian period. The study of geochemistry shows that, Biotite granites in Zhuxi mining area are characterized by high silicon, high alkali and high differentiation. They belong to calc-alkaline and peraluminous granites. The biotite granites are enriched in trace elements such as RbCU, Ta, and the depletion of elements such as Baan, NbSr, Ti, etc. The total amount of rare earth elements is relatively low. According to the mineral symbiotic assemblage and metasomatism, the scheelite deposits in Zhuxi skarn type are divided into early skarn stage, late skarn stage and quartz sulfide stage. The pomegranate is mainly composed of calcium aluminite and calcium iron garnet, and the clinopyroxene is mainly diopside-calcium ferrite series. The skarn minerals fluorite, talisite, apatite and sphene are fluorine-rich minerals closely associated with scheelite. The results show that the ore-forming fluid of Zhuxi tungsten deposit is a fluorine-rich system, which is beneficial to the migration and precipitation of tungsten. The in-situ analysis of scheelite is carried out by LA-ICP-MS. The trace elements and rare earth elements of scheelite in Zhuxi tungsten mine are studied in detail. According to the partition characteristics of REE elements in scheelite, the mineralization of Zhuxi tungsten deposit is divided into two major stages, and the ore-forming fluid properties of the two stages are obviously different. The reaction environment is also different, the first stage is oxidation environment, the second stage is transition from reducing environment to oxidizing environment, the second stage should be the main metallogenic stage, forming the main body of Zhuxi tungsten deposit. The zhuxi skarn type scheelite presents a rare earth distribution pattern of LREE enrichment. This may be due to the depletion of heavy rare earths in scheelite as a result of precipitation of heavy rare earths such as pomegranate. The metallogenic age measured by LA-ICP-MSU-Pb dating of sphene in situ is 154 卤3 Ma. and the age of apatite LA-ICP-MSU-Pb is: 137 卤9 Ma-148 卤16 Ma. which belongs to Yanshanian period. It is consistent with the previous diagenetic ages in the error range, indicating that the mineralization is closely related to the Yanshanian magmatism in South China.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.67

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