伴金黄铁矿(Pyrite)结构的研究  

Study on the Crystal Structure of the Pyrite with Au

作　　者：张维睿 韦承谦[2] 张金平 张婉静[2] 

机构地区：[1]西澳大学地质学系 [2]北京大学化学系

出　　处：《北京大学学报（自然科学版）》1991年第2期184-191,共8页Acta Scientiarum Naturalium Universitatis Pekinensis

摘　　要：应用多晶X射线衍射和Rietveld拟合和修正测定了含金与无金两类共20个黄铁矿样的精细结构。它们属于空间群T_h^6-Pa3。两类样品的晶胞参数无明显差别,平均值分别为a_0=5.4154(?)和a_0=5.4156(?),而硫原子坐标参数显著不等,含金的(?)_s=0.3849,无金的(?)_s=0.3868。依上述参数计算Fe-S和S-S键长,进而应用键价法算出结构中Fe离子的电价。结果说明含金的黄铁矿中Fe-S键短于五金的,而S-S键则相反;Fe离子价不相等,前者高于后者;大部分矿样中,Fe离子占有率小于1.000。在黄铁矿中容纳着上述离子变价和缺位等非完整性。因此就精细结构而言黄铁矿是一个具有不同程度非完整结构的系列。 含金矿样中Fe离子高于正二价的事实说明,当金以Au^(3+)(Au^+)迁移至含有Fe^(2+)和S_2^(2-)的热液体系中,Fe^(2+)部分地被氧化成Fe^(3+),而Au^(3+)(Au^+)被还原为Au与FeS_2共沉淀下来分散在黄铁矿晶格之外。The fine structure of Pyrite type were worked out by means of polycrystalline diffractometry and Rietveld profile analysis refinement. We used twenty samples about two kinds of Pyrite with gold and without. The space group is Th6-Pa3. The average value of lattice parameters for the two kinds of samples are almost equal but the coordinations of S atom are no equal obviously, x3 = 0.3849 for the former x3= 0.3868 for the latter. From the coordinations we have derived lengths for Fe-S and S-S bonds as well as calculated atomic valences for Fe by bond valence theory.The lengths is shorter for Fe-S bond and longer for S-S, the atomic valence for Fe is higher in the sample with gold. In the most of the samples the occupancy of Fe deviates from unity. So the Pyrite type can tolerate such imperfect as variety of atomic valence and vacancy. So far as the fine structure is concerned the Pyrite type should be a series of forms containing different imperfect structure. In the Pyrite with gold high valence state for Fe imply that Au3+ or Au+ ions migrete into thermal liquid containing Fe2+ and S22- and are reduced to Au by Fe2+, co-depositing down with FeS2, in dispersing at outside of the Pyrite lattice.

关 键 词：伴金 黄铁矿 精细结构 X射线衍射 

分 类 号：P578.292[天文地球—矿物学]