黄铁矿精细结构与晶胞参数的关系及其标型意义

Relationship between Fine Structure and Cell Parameters of Pyrite and Their Typomorphic Significance

黄铁矿是内生金矿床中主要的载金矿物,其标型特征对金矿成矿有重要的指示意义。笔者讨论了黄铁矿精细结构中键长、键角对晶胞参数的影响及其标型意义。实验黄铁矿样品采自山东莱州三山岛海域金矿ZK3007号钻孔岩心,测试利用单晶X射线衍射技术,获得了黄铁矿晶体的精细结构数据,并利用空间几何关系及偏导数分析了键长、键角变化对黄铁矿晶胞参数的影响。通过研究发现,黄铁矿的晶胞参数主要受其内部配位八面体大小影响,而受配位体间致密程度影响较小;配位八面体的大小主要与结构中的Fe-S键长密切相关;Fe-S键长变化的原因与Co、Ni、Cu等代替Fe及As代替S的类质同像有关。键长、键角等精细结构研究从本质上解释了黄铁矿晶胞参数变化,对黄铁矿晶胞参数标型特征的表征及金矿找矿有重要的实际意义。

Pyrite is the main gold bearing mineral in endogenetic gold deposits,and its typomorphic characteristics have important implications for gold mineralization.At present,the typomorphic characteristics of pyrite are mainly focused on the morphology and physicochemical properties,while the microstructure characteristics of pyrite,such as unit cell parameters,bond length&bond angle,are less studied.Moreover,the existing studies mainly focus on the influence of composition on cell parameters.Few people have analyzed the relationship between fine structure of pyrite characterized by bond length&bond angle and cell parameters.The experimental samples were collected from Sanshandao Gold Deposit in Laizhou,Shandong Province.The crystal structure data of pyrite were collected by single crystal X-ray diffraction,and the fine structure data were obtained by analytical software.The influence of bond length&bond angle on the lattice parameters of pyrite was analyzed by spatial geometric relationship and partial derivative.It was found that the lattice parameters of pyrite were mainly affected by the internal coordination octahedron.The effect of the size of the ligands is less affected by the gap between the ligands.The size of the octahedron is closely related to the length of the Fe-S bond in the octahedron,and the size of the space between the coordination bodies can be characterized by the Fe-S-Fe bond angle or the S-S bond length.The reason for the change of Fe-S bond length is related to the isomorphism of Co,Ni,Cu replacing Fe and As replacing S.This provides a theoretical basis for the change of unit cell parameters,and is of great significance for guiding gold production with the typomorphic characteristics of unit cell parameters.