且干布拉克蛭石的矿物学研究

A MINERALOGICAL STUDY OF VERMICULITE FROM TSEGANBRARK XINJIANG

本文对产于新疆且干布拉克的我国最大蛭石矿的组成、结构和谱学特征做了系统的阐述。研究表明:且干布拉克蛭石是由金云母风化而成。由于风化的不完全,该蛭石保留了许多金云母的特征。该蛭石不是个严格矿物学意义上的蛭石,它是由金云母、严格矿物学意义上的蛭石、以及两者组成的多种混层矿物的混合物。金云母风化过程中可能有杂质铁相生成。蛭石的颜色和多色性,可能起因于其中的O^(2-)→Fe^(2+23+)和Fe^(2+)→Fe^(3+)

The structure, composition and spectroscopy of vermiculite occurring in the largest vermiculite deposit in China is dealt with in this paper.The chemical compositions of vermiculite and original mica reveal that the vermiculite from Tsegaubrark is a product of phlogopite weathering. Because of insufficient weathering. the mineral is rich in K_2O and poor in interlayer water.The vermiculite from Tseganbrark is not a pure vermiculite but a mixture of phlogopite, vermiculite and several kinds of mixed-layer minerals composed of phlogopite and vermiculite. There may be five mixed-layer structures, i. e., 1: 1, 2: 1, 2: 4, 1: 3 and 3: 1 phlogopite/vermiculite mixed-layers, except 1: 1 type which seems to be regular, the others are irregular.Double endothermic trough on DTA curves at about 100℃ and 150℃ may be assigned to two kinds of interlayer water occurring in different structural environments. Two infrared absorption peaks near 3700 and 3680cm^(-1) may be due to hydroxyl vibrations of Mg_3OH of phlogopite and vermiculite, respectively. Resonances of structural Fe^(3+)(g_(eff)= 4.29)and iron impurity(g≈2.00)lie on ESR profiles.The color and pleochromatism of vermiculite may result from the charge transfer of O^(2-)→Fe^(3+,2+)and Fe^(2+)→Fe^(3+).