摘要
伴随深部地质过程的地幔流体作用是引发地壳中成矿作用的重要物质源和动力源。由于地幔流体的超深源性及由此决定其性质和演化的复杂性,使人们很难具体捕捉其实际存在,或者多数情况下很难准确界定。通过岩相学、岩石化学、电子探针和扫描电镜及能谱分析的综合研究发现,地幔流体活动的现实微观踪迹和存在方式可以表现为富铁熔浆包体和富铁微晶玻璃,二者在透射偏光显微镜下无光性,呈黑色不透明状;反射偏光显微镜下不反光,但在电子显微镜下呈显微晶质结构,显示微晶金属和非金属矿物之间呈熔离交生,超微晶矿物组成以硅酸盐和石英为主,尤其是经过成分配比换算,得到碳硅石,含铬自然铁、钛铁矿、磷灰石和含钛镜铁矿等地幔标型矿物,反映了地幔流体的熔浆性质。捕捉和揭示深部地质过程中地幔流体作用的现实微观踪迹,对于深入分析和认识地壳地质作用的机制和成矿效应具有重要理论和现实意义。
Mantle fluid metasomatism in the deep geologic process is an important substance supplier and energetic contributor and the complexity of its nature and evolution make it difficult to be observed and confirmed.Based on the researches of petrography,petro-chemistry,electron microprobe(EMP),scanning electron microscopy(SEM) and energy spectrum(EP),it is discovered that there are two kinds of the actual microcosomic traces of mantle fluid,that is Fe-rich melt xenolith and Fe-rich micro-glass.Both are of non optics under transmitted polarized light appearing to be black opaque and can not reflect light under the reflected polarized light.EMP results show that the Fe-rich melt xenolith and Fe-rich micro-glass are of micro-crystalline texture and unmixing texture composed of micro-metals and micro-nonmetals.The micro-minerals are mainly silicates and quartz,and after the ratios calculation we get the SiC,Cr-bearing natural iron,ilmenite,apatite and Cr-bearing specularite and all of these are indication minerals of mantle,suggesting the nature of mantle fluid be similar to the melt.The study of the actual microcosomic traces of mantle fluid in deep geologic process is of high significance to the mineralizing mechanism in the Earth's Crust.