云南小湾断层泥矿物特征及其构造意义

通过显微镜观察、X射线衍射、红外光谱和化学分析等方法研究云南小湾断层泥中伊利石矿物特征,结果显示:(1)断层泥中的伊利石发育定向排列,其集合体呈扭折褶皱变形,有时呈流状构造充填在碎屑之间;(2)伊利石的X射线衍射特征为△(002)-(001)]>8°,Ir>1,BB₁<4°,属ISII有序混层,膨胀层约占15%,晶胞参数b₀=8.993Å,1M多型结构;(3)层间阳离子2Ca+Na+K≈1,MgO含量变化1.05%-2.89%,结晶水(H₂O⁺)含量变化4.43%-5.23%。综合上述特征认为,断层泥伊利石不同于其它成因的伊利石,它是断层活动的直接产物,因此,根据它的特征可以推测断层活动机制。

CHARACTERISTICS OF MINERALS IN FAULT GOUGE FROM XIAOWAN ,YUNNAN ,AND THEIR GEOLOGICAL SIGNIFICANCE

Fault gouges are direct products of faulting and hence record a great deal of information on fault activity. In this paper, the chemical composition, crystal pattern and structure of the illite from fault gouges at Xiaowan, Yunnan, are studied by XRD, microscopic observation and chemical analysis. The studies are synthesized as follows. (1) An oriented alignment of illite generally develops in fault gouges, kink band or fold frequently develops in the aggregates of illite, forming a flow structure in between clastic grains. (2) The interlayer ions (2Ca+Na+K)≈1 within the illite form fault gouges is higher than that within the illite of weathering and marine origin, the crystal water (H⁺O) within the illite from fault gouges is lower than that within the illite weathering and marine origin and MgO within the illite from fault gouges is higher than that within the illite of weathering and is lower than that within the illite of marine origin. In conclusion, the illites from the fault gouges at Xiaowan are different from the illites of weathering and marine origin. The illite from fault gouges is products of the lower grade metamorphism due to the fault motion. (3) XRD analyses show that illite from fault gouges at Xiaowan belnog to ISII structure: △(002)-(001)] >8°;Ir >1; BB1 <4°; 1 M pleomorphism; b₀ value of illite is 8.993Å; The patterns interlayer positive ions2Ca+Na+K]≈1 ;which show that the growth of illite from fault gouges are of low pressure and temperature (<200℃). (4) The frictional heating caused by rapidly faulting may lead to chemical and physical changes occurring in some minerals from the fault and even silicate minerals are fused. The order ISII structure and 1 M pleomorphism of the illite from fault gouges show that the growth of illite are of low temperature (<200℃), and characters of low temperature and microstructure of the illite from fault gouges show that the fault motion at Xiaowan is creep slip.