等轴锶钛石在我国的首次发现

笔者于1985—1986年,对华北地区岩浆岩型磷灰石矿床进行研究时,在山西省临县紫金山的钛榴霞石正长斑岩中,发现了与苏联的达乌松矿（Tausonite）相似的矿物,即等轴锶钛石。该矿物在我国的首次发现,对这一地区碱性岩的矿物学和岩石学研究无疑是很有意义的。本区等轴锶钛石一般为淡棕色,呈立方体或不规则柱状,折射率N=1.977±0.002,比重为4.66,均质体,个别具光性异常并呈环带构造,晶胞参数a0=3.905A,空间群Pm3m,晶胞体积v=59.55A。本文重点对该矿物的地质产状、矿物共生组合、物理性质与光学性质、矿物化学成分及X射线分析进行了研究。笔者认为本区等轴锶钛石是富钛富碱贫硅的碱性岩浆中早期结晶的产物。

Discovery of Tausonite in China

The mineral, which resembles tausonite in USSR, was found in a schorla-mite-bearing nephelinesyenite-prophyry body in Zijinshan, Linxian, Shanxi Province in 1985, when the authors were researching the magmatic apatite deposits in North China. This was the first time for the discovery of tausonite in China and it will be of great significance in petrologic and mineralogic study of alkaline rocks in this area, Tausonite is generally light brown in color, cubic or irregular-grained in form and optically istropic with occasionally optical abnormality and zoning structure. Its refractive index N= 1.977?0.002, specific gravity 4.66. crystal lattice parameter a0 = 3.905A, space group pm3m and unit cell volume V=59.55A. The geological occurrence, mineral paragenesis, physical and optical properties, chemical compositions and X ?ray diffractory spectroscopy of this mineral have been studied in the present paper. It is suggested that tausonite in the area studied was formed from the early crystallization of an alkaline magma which was rich in Ti and alkali but poor in Si,