摘要
在内蒙古大井锡石硫化物型铜银锡矿床的闪锌矿中发现了一种铜铁硫新出溶相矿物。作者研究了其光性、化学成分、晶体结构及出溶特征,提出了它作为闪锌矿中一种新的出溶相矿物的重要证据,并对其形成机理结合加热实验及已有的硫化物体系相平衡资料以及矿床地质特点进行了分析。
The present article describes an abnormal sphalerite from the Dajing cassiterite-sulfide type Cu-Ag-Sn deposit, Inner Mongolia, China. This unusual sphalerite displays in contrast to normal sphalerite a very pronounced pleochroism and anisotropism as a result of fine exsolved particles of a coherent, hitherto unknown Cu-Fe-S phase. Under high magnification (1250 X), the short prismatic crystals of the exsolved phase are arranged parallel or subparallel to a certain crystallographic direction of the sphalerite matrix. In one direction these minute grains (0<150nm) look similar to the coexisting chalcopyrite but in the perpendicular direction the exsolved phase appears to be merged in the matrix material and can not he distinguished from the sphalerite matrix. Microprobe and wet chemical analysis of the sphalerite involving both the matrix and the exsolved material yielded a constant composition containing 53.59% Zn, 6.72% Cu, 6.68% Fe and 32.62% sulfur (wt%). Analysis of the electron microscope gave for the exsolved phase a composition close to that of CuFeS_2. Diffraction pattern of the chalcopyritefree sphalerite obtained from the transmission electron microscope indicates a lattice parameter (1.076 nm) of the exsolved phase twice as large as the parameter of the basic sphalerite cell (0.538 nm). In this direction the structures of the exsolvate and the matrix are coherent. Heating experiments of the hand-picked sphalerite conducted in the temperature interval 200—700℃ indicate a sluggish rehomogenization to a preexistent high temperature primary phase. Heating at 645℃ for 5 days yielded as reequilibration product a normal sphalerite in coexistence with some chalcopyrite-like phase and trace of segregated sulfur. As a stable phase this exsolved Cu-Fe-S mineral in the 'abnormal sphalerite' is thus assumed to be formed under high sulfur fugacity conditions.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1990年第3期206-214,T002,共10页
Acta Geologica Sinica
