中国的磷铁锂矿-磷锰锂矿系列矿物

Triphylite-Lithiophilite Series in China

磷铁锂矿与磷锰锂矿是一完全类质同象系列中两个端员矿物。磷锰锂矿在我国新疆伟晶岩中已有大量发现。笔者于1984年在福建南平稀有金属花岗伟晶岩中发现了典型的磷铁锂矿。此外,早在1980年笔者还在新疆青河富铍伟晶岩中发现了成分介于该类质同象系列中间的磷锰铁锂矿。对后两个产状的矿物进行了较详细的矿物化学成分和物理性质研究。结合前人的资料,文中系统地讨论了国内所发现的六个产状的磷铁锂矿-磷锰锂矿系列矿物的化学成分特征及变化规律,化学成分与光学性质、物理性质、晶胞参数等之间的相互关系,并系统地引用了大量国外资料作对比。讨论了矿物中Mg、Ca等含量对这些特征的影响。另外,笔者还研究了该系列矿物成分与红外光谱之间的关系,指出矿物的红外吸收谱带频率与铁锰比值间呈良好的线性关系,并给出了相关关系式。

Triphylite-lithiophilite, a perfect isomorphous series, has been found in six mineral occurrences of China. Of these, four are in the rare-metal granite pegma tires of Xinjiang where aU of the samples are lithiophilite. The Mn-rich features are also observed in other Fe, Mn minerals of Xinjiang pegmatites. In 1984, a few specimens of triphylite were discovered in Nanping rare-metal pegmatite of Fujian. The mineral is one of the few Fe, Mg-richest triphylites in the world. Another triphylite occurs in Shangxian pegmatite of Shanxi province. Up to now, a pe rfect triphylite-lithiophilite series has been found in China, whose mineralogical properties are all listed in the paper.Researches on the chemical composition of triphylite-lithiophilite show that, besides the major constituents Fe^(2+) and Mn^(2+), the cations at the oetahedral M(2) site in the minerals are Mg^(2+), Ca^(2+), Fe^(3+). The highest MgO content is 7.38 wt％. Generally speaking, Mg^(2+) replaces Fe^(2+) e+asily, while Ca^(2+) sometims substitues for Mn^(2+) at the M(2) site. Pure triphylite has not been found yet in the nature and LiFe[PO_4] contents of all native triphylites are lower than 80％. Nevertheless, there are very pure lithiophilites in nature.The paper illustrates the relations of chemical composition (Fe/Mn) to physical properties, optical properties and unit cell dimensions of the series. With the increase in Fe/Mn ratio, the specific gravity and the index of refraction will grow up, the cell parameters will decrease, and the optic axial angle will vary regularly. The rising of Mg^(2+), Ca^(2+) contents of the minerals, on the other hand, will also cause an obvious variation in the above properties.The IR spectral analysis of four triphylite-lithiophilite samples collected in China has been made to find the correlation between chemical composition and IR absorb peaks. The results show that there exists good linear correlation between absorb peaks from 475-455cm^(-1) and chemical composition; it is therefore feasible to use IR spectra for semi-quantitative determination of chemical composition of this series.