坦桑尼亚某绿岩带型金矿床中黄铁矿的标型特征及意义

黄铁矿是金矿床中主要的贯通性载金矿物，通过对坦桑尼亚某绿岩带型金矿床中黄铁矿的形态、化学组成和物理性质等标型特征进行详细研究，能够从某种程度上识别出含金矿体，对野外勘查工作具有重要指导意义。通过野外地质观察和室内分析对绿岩带型金矿床中的黄铁矿标型特征进行了详细研究，结果表明：该矿床中黄铁矿呈浅黄—黄色，以细粒为主，具有半自形和碎裂结构的黄铁矿含金性最好；主矿体即金矿化强烈区域黄铁矿晶形以五角十二面体和五角十二面体与其他单形的聚形为主。主成矿阶段的黄铁矿主量元素整体表现出亏S、富Fe的特点，而微量元素富As、Sb，表明形成了载金能力较好的P型黄铁矿；主矿体附近黄铁矿的热电性主要表现为P型黄铁矿，表明该含金矿脉剥蚀程度总体较低，且目前揭露的仅为矿脉浅部，向深部矿脉仍有较大的延伸，由此推断该矿床深部具有良好的找矿前景。

Typomorphic Characters and Significance of Pyrite in a Greenstone Belt Type Gold Deposit in Tanzania

The greenstone belt around Victoria Lake in Northwest Tanzania is one of the world famous gold metallogenic belts，but its overall research level is relatively low，especially lack of research on major gold-bearing minerals.Pyrite is mainly connectivity gold-bearing mineral in gold deposit，through observing，analyzing and studying the typomorphic characteristics such as morphology，chemical composition and physical properties of pyrite in greenstone belt type gold deposits around Victoria Lake in Tanzania，the organic relationship between typomorphic characteristics and gold grade is found out and applied to the field gold exploration.It is helpful for geologists to distinguish the characteristics of gold-bearing ore bodies in time and accurately，and it has an important guiding significance for field exploration to some extent recognition gold ore body.In this paper，the typomorphic characteristics of pyrite in the greenstone belt type gold deposit have been studied in detail by means of field observation，microscopic observation，electron probe analysis and ICP-MS.The results show that the pyrite in the deposit is light yellow-yellow，mainly fine particles and it has best gold-bearing for pyrite with subhedral and cataclastic structure.It is mainly composed of pentagonal dodecahedron，pentagonal dodecahedron and other monomorphic polygons in the main ore body which gold mineralization is strong.The S/Fe average value of pyrite in the main metallogenic period is 1.96，and it shows that the characteristics of the main content elements of pyrite in the main metallogenic stage，with deficient S and rich Fe as a whole，and showing the sulfur fugacity of the hydrothermal system in the main metallogenic period is low，while the trace elements are rich in As and Sb，which is positively correlated with the content of Au element.It shows that these elements displace S element in pyrite and form P-type pyrite with better gold-carrying capacity.Pyroelectricity of pyrite near the main ore body is P-type pyrite，it mainly shows the lower denudation extent of overall gold vein，and the exposed vein is only shallow，and there is still a large extension to the deep of the vein，thus it has a good prospecting for deep.