安徽省马山矿区硫化物矿石中黄铁矿与磁铁矿的后成合晶

在安徽省马山矿区的硫化物矿石中，黄铁矿与磁铁矿呈后成合晶交代磁黄铁矿的结构，是成矿系统物理化学条件向磁黄铁矿-黄铁矿-磁铁矿三相点演化的产物。系统经过三相点的几率甚小，因而这种结构在矿石中十分少见。

A SYMPLECTITE OF PYRITE AND MAGNETITE IN SULPHIDE ORE FROM MASHAN, ANHUI PROVINCE

In the sulphide ore from Mashan, Anhui Prdvince, a symplectite of pyrite and magnetiteis found in contact with a pyrrhotite grain with an enbayed boundary convex to the pyrrhotite andis hence interpreted to have resulted from the replacement of pyrrhotite. The magnetite is scat-tered unevenly as spots, branches, worm-like rods and irregular grains, measuring from less than1 micron to several tens of microns in size, in the host pyrite. The compositions of pyrrhotite,pyrite and magnetite related to the symplectite are given by electron microprobe analyses. Such atexture is likely to be formed when the ore-forming system reaches the three-phase point ofpyrrhotite, pyrite and magnetite from the pyrrhotite stability field. The extremely small probabili-ty for the system to reach this point could be used to interpret the rare occurrence of such symplec-tite in natural ores.