纳米比亚西北部Epembe铌钽矿床地质和年代学研究及资源量估算

发布时间：2018-05-29 06:40

本文选题：碳酸岩 + 铌钽矿床　；参考：《中国矿业大学》2017年硕士论文

【摘要】：研究区位于纳米比亚西北部Opuwo约80km的Epembe地区,对象为其内具有铌钽成矿潜力的碳酸岩岩体。收集了本区地质资料数据,采用野外观察采样、室内分析测试(包括光学显微镜、扫描电镜、电子探针和离子探针等)和地质建模等技术手段,研究了碳酸岩矿床地质、年代学特征和铌钽的资源潜力。主要结论如下。本区基底片麻岩首先受到Kunene杂岩体斜长岩的侵入,再有霞石正长岩侵入。碳酸质岩浆沿着霞石正长岩株中发育的NW-SE向断裂侵入形成Epembe碳酸岩体。碳酸岩以方解石为主,含少量磷灰石、烧绿石和微量锆石,细-粗粒结构,块状构造,呈脉状产出,延伸长度约10km。烧绿石为Epembe碳酸岩早期结晶产物,其成分从早期的富Ca变为晚期热液作用阶段富。这表明了碳酸岩浆的演化过程中烧绿石均有晶出,从而导致该矿物成分的明显改变,如Si、U、Th和Fe等元素出现富集,特别是在烧绿石环带周围。U和Th等元素的富集还导致了辐射变晶作用、蚀变作用和A空位的形成。Epembe铌钽矿床的成因为碳酸岩浆作用,但铌的聚集过程仍有待于进一步工作,可能与碳酸-硅酸岩浆对的岩结晶分异或熔离作用有关。U-Pb锆石测年结果表明碳酸岩浆的侵入时间在1148至1204 Ma,最佳拟合线显示一致线上交点年龄为1184.4±10 Ma。该结果表明Epembe碳酸岩体的形成时间略早于Swartbooisdrif富铁碳酸岩(位于Epembe以东约35km)。由于富钙碳酸岩常代表碳酸岩浆活动的早期,所以,位于泛非事件作用带南部的分别富钙和富铁的两个碳酸岩体属Kunene岩浆-构造活动期内的同一次岩浆作用。3D建模和计算结果表明,Epembe B区内脉状矿体中Nb2O5资源量为3827600t(下限品位0.16%wt),钽资源量为4391800t(下限品位0.01%wt)。
[Abstract]:The study area is located in the Epembe area of Opuwo about 80km in northwestern Namibia. The object of the study is the carbonate rock body which has the potential of niobium and tantalum mineralization. The geological data of the area are collected, and the geology of carbonate deposits is studied by means of field observation and sampling, laboratory analysis and testing (including optical microscope, scanning electron microscope, electron probe and ion probe, etc.) and geological modeling. Chronological characteristics and resource potential of niobium and tantalum. The main conclusions are as follows. The basement gneiss in this area was first intruded by the plagioclase of the Kunene complex and then by the nepheline syenite. The carbonated magma intruded into the Epembe carbonate along the NW-SE trending faults developed in the nepheline syenite. The carbonatite is mainly calcite, containing a small amount of apatite, pyrochlore and trace zircon, fine-coarse grain structure, block structure, vein-like occurrence, and its extension length is about 10 km. The pyrochlore is the early crystallization product of Epembe carbonate, and its composition changes from the early Ca rich stage to the late hydrothermal stage. This indicates that the pyrochlore has been crystallized during the evolution of carbonated magma, which leads to the obvious change of the mineral composition, such as the enrichment of elements such as Si-U, Th, Fe, and so on. Especially, the enrichment of elements, such as .U and Th, around the auriferous greenstone ring also leads to radiative metamorphism, alteration and formation of A vacancy. The formation of the niobium-tantalum deposit is due to carbonate magmatism, but the process of niobium accumulation still needs further work. The results of zircon dating indicate that the intrusive time of carbonate magma is 1148 to 1204 Ma.The best fitting line shows that the age of intersection on the consistent line is 1184.4 卤10 Ma. The results show that the formation time of Epembe carbonate is a little earlier than that of Swartbooisdrif iron-rich carbonate (about 35kmg) east of Epembe. Because calcium-rich carbonate rocks often represent the early stages of carbonated magma, The two carbonates rich in calcium and iron, located in the southern part of the pan-African event zone, belong to the same magmatism during the Kunene magma-tectonic activity period. The results of 3D modeling and calculation show that the Nb2O5 resource in the vein orebody in the Epembe B area is 3827600 t. The lower grade is 0.16% and the amount of tantalum resource is 4391800 t (the lower grade is 0.01).
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.2

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