祁连山某地铂-金砂矿中等轴铁铂矿的研究

A STUDY OF ISOFERROPLATINUM IN A PLATINUM-GOLD PLACER FROM QILIAN MOUNTAINS, NORTHWESTERN CHINA

本文研究了我国西北祁连山某地与超基性岩有关的冲积-洪积层中的铂-金砂矿矿物，重砂矿矿物鉴定表明，除了自然金、自然锇、依锇矿、铬铁矿等之外，还发现了铂-铁合金矿物。根据铂-铁合金矿物的光性、化学成分及X射线衍射数据，将其定名为等轴铁铂矿（isoferro－Platinum）．这是国内首次报道该矿物的完整矿物学资料。

Isoferroplatinum was identified in several platinum-group element (PGE) minerals from an al-luvial-diluvial platinum-gold placer related to chrome bearing ultrabasic rocks. The mineral isshaped as rounded grains or irregular grains (0. 6 × 0. 7~ 1. 0 × 1. 8mm), with a bright yellowish-white reflection color and an isotropic feature under reflected light microscope. Microprobe analysisyielded 90. 48%~ 91. 56% Pt and 8. 56% ~ 9. 10% Fe (Table 1 ), with a molecular formula ofPt2.85-3.00Fe. Based upon the X-ray powder diffraction data of two samples, a values were deter-mined as 0. 3863± 0. 0001nm (Sample No. 2) and 0. 3868± 0. 0003nm (Sample No. 6), with unit-cell volumes of 0. 05 765 ± 0. 00004 (nm) 3 and 0. 05787± 0. 0001 (nm)3, respectively (Table 2). Thesedata are consistent with those of natural and synthetic isoferroplatinum documented by Cabri et al.(1975). The studied isoferroplatinum is associated with native gold, osmium, iridosmine andchromite. This assemblage provides a valuable indicator for prospecting primary PGE ores in thearea.