Pb—Sn—Fe—Sb—S体系相关系

用抽空石英管法研究以Fe_(0·96) Sb_(2·04) S_(4·12)为投影顶点,8×(PbS-SnS-SnS_2)为投影平面的Pb-Sn-Fe-Sb-S体系的相图表明,由于Pb(?)Sn~(2+)之间互相取代,500℃时辉锑锡铅矿固溶体中Sn~(2+)变化范围(以单位分子式11个金属原子总数为计量)是0—4.8个原子,400℃时则为0—4.0个原子。同时,Sn~(4+)变化范围是1.3—2.3个原子和1.5—2.1个原子。圆柱锡矿固溶体变化范围较小。500℃时Sn~(2+)变化范围是0.4—1.8个原子,400℃时为0.5—1.7。Sn~(+4)变化范围则分别为3.2—4.2个原子和3.3—4.2个原子。变更Fe含量(0.81—1.09)及Sb含量(1.83—2.29)进行的几组合成实验表明,上述两个矿物中Fe、Sb含量变化范围很小,不超过±0.15个原子。辉锑锡铅矿固溶体可与方铅矿、块硫锑铅矿、针硫锑铅矿、硫锡铅矿、硫锡矿、圆柱锡矿等形成平衡结线。而圆柱锡矿不与方铅矿、硫锡矿、硫锡铅矿形成平衡结线,但可与辉锑矿、SnS_2及上述其他矿物形成平衡结线。结合锡的硫化物及氧化物(锡石)热力学稳定场计算表明,在本体系内辉锑锡铅矿在300℃时稳定区的硫活度在lga_(s2)=-20(atm)附近,氧活度小于lga_(o2)=-40(atm),而圆柱锡矿稳定区硫活度大于lga_(s2)=-10(atm)。     

Mutual Pb2+/Sn2+ substitution in sulfosalts

Summary In naturally occurring sulfides and sulfosalts, the elements tin and lead can substitute for each other and form solid solution series. The best known example is the montesite series between teallite and herzenbergite. Within a coordinated research program including ore microscopy, X-ray and microprobe studies, mineral syntheses and Mössbauer spectroscopy, other lead sulfosalts were discovered which show considerable solid solution series.Natural tin-bearing jamesonites which have been recently discovered have also been confirmed experimentally.The present work reveales a broad solid solution field for franckeite ranging from Pb-rich potosiite to Sn-rich incaite. The well-established silver-free franckeite formula exhibits an ideal composition of(Pb, Sn) ₆ ²⁺ Fe²⁺ Sn ₂ ⁴⁺ Sb ₂ ³⁺ S ₁₄ ^2– . Valencies of the Fe, Sn, and Sb in franckeite shown in this formula have been confirmed by Mössbauer spectroscopy. Frequently observed trace amounts of Ag, Zn, Ge, and In are not essential in the structure.Numerous microprobe analyses of cylindrites indicate that they form a restricted solid solution series with slight Pb/Sn²⁺ variations. Cylindrite forms at increased sulfur fugacity. Experiments and microprobe analyses on ores demonstrate the direct replacement of tin-rich franckeite or incaite by pseudomorphic lamellae of cylindrite during controlled sulfdization but no characteristic cylinders were observed. In the replacement reaction most or all of the bivalent tin was oxidized to quadrivalent tin to form cylindrite Pb₄FeSn₄Sb₂S₁₆.Contribution to the Ore Mineralogy Symposium (IMA/COM) at the 14th General Meeting of the International Mineralogical Association, at Stanford, California, in July, 1986.