摘要:
借助于X光衍射仪、透射电子显微镜(TEM)和扫描电子显微镜(SEM)等手段,较详细地揭示了内蒙大青山晚古生代(C2—P1)煤系中降落火山灰的蚀变特征,以此来论述沉积环境对火山灰蚀变作用的影响。泥炭沼泽环境中,降落火山灰以原地直接高岭石化为主,残留较多的火山玻屑和晶屑形态,并具斑状结构;非泥炭沼泽环境中,降落火山灰以异地凝胶化—多种粘土矿物化为主,微层理、微层面等沉积岩特征明显。火山灰降落的环境不同,其蚀变作用和蚀变产物亦不同。本文对加深煤系火山事件沉积的认识和研究煤系高岭岩的成因机理颇有意义。
关键词:
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沉积环境 /
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火山灰 /
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蚀变 /
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大青山
Abstract:
By the aid of X ray diffractometer, transmit electron microscopes (TEM) and scQan electron microscopes (SEM), authors have revealed the altered features of landing ash from Daqingshan Inner Mongolia Late Paleozoic era (C 2—P 1 ), and discussed the effect of depositional setting on ash alteration. In peat moor, the landing ash is directly altered into kaolinite in situ,forming cryptocrystalline kaolinite mudstone. The mudstone is almost monomineralic and keeps the shapes of crystallinoclastic and shard. Under TEM, the kaolinites in the form of unitary and aggregate are mostly glassy.Their arris are not tidy, with different shapes small particle size and strong aggregation. Under SEM, worm kaolinites and pisolite kaolinites are usually paragenetic. Both made up porphyritic texture in the range of micron. In non peat moor, the landing ash is firstly altered into gel, then into clay minerals in allochthon, becoming clay mudstone. The mudstone is polymineralic, with mineral components composed of illite, montmorillonite and interstratified illite montmorillonite and so on. Under TEM, the kaolinites are coagulative and clastic; under SEM, the sedimentary characters are often seen, such as microbedding and microbedding plane made up of oriented clay minerals. After the ash transferred by air deposits, its alteration and products in peat moor are different from non peat moor because the conditions of physics and chemistry vary with environment. The paper shows much to insight on deeply understanding of volcanic event strata and studing genesis of kaolinton in coal series.
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