云南马关都龙锡锌多金属矿床鲕状黄铁矿微束分析

Microanalysis of Oolitic Pyrite in Dulong Sn-Zn Polymetallic Deposit, Maguan, Yunnan Province, China

鲕状黄铁矿是都龙锡锌多金属矿床中的特殊硫化物矿物之一。本文通过扫描电镜观测其矿物微形貌结构特征,并利用电子探针分析其化学成分,为认识该类矿物成因及其与成矿作用的关系提供依据。扫描电镜观测显示,该矿床中黄铁矿鲕粒主要由黄铁矿微晶组成,在鲕粒纹层孔隙中发现了丝状体、杆状体、球状体等微生物成因显微组构。这些微生物化石与热液喷流沉积成因硫化物矿床、热泉、海底热液喷口中的微生物化石具有诸多相似特征,表明该矿床形成过程中可能存在热水沉积成矿作用,微生物在黄铁矿鲕粒形成过程中可能起到转换硫源、吸附金属元素、粘结黄铁矿微晶等作用。电子探针观测显示,黄铁矿鲕粒中的Zn含量较高,暗示鲕状黄铁矿可能作为后期成矿作用Fe、Zn、S等成矿元素的物源之一。从鲕粒边部到中心Zn含量逐渐递减的趋势,并由交代作用在鲕粒边部形成富Zn边。

Oolitic pyrite is one kind of feature minerals in Dulong Sn-Zn polymetallic deposit, Yunnan Province, China. In this paper, the micro-morphological characteristics of oolitic pyrite were studied by using field emission scanning electron microscope（SEM） and its chemical components were analyzed with electronic probe. These analytic results provid micro-scale evidences for the genesis of oolitic pyrite and its relationship with mineralization. The SEM results show that a lot of filaments, rhabdoids and spheroidites occur at micro fractures in the lamina of ooids. These micro-textures have similar morphology characteristics with micro-fossils occurring at exhalative hydrothermal sedimentary sulfide ore deposits, hot springs and hydrothermal vents under sea, indicating that their microbe genesis which might be related to exhalative hydrothermal sedimentation. The microbes might play a role to transform sulfide source, absorb metal elements and cement pyrite crystallites during pyrite ooids＇ forming. In addition, the electronic probe results show that the pyrite ooids have a high concentration of Zn, suggesting that pyrite ooids might be a source providing some ore-forming elements such as S, Fe and Zn, etc. The edge of oodis is brighter than inner under micro-scope as the result of metasomatism. The characteristics of the concentration of Zn show a gradually decreasing trend from edge to center.