论晋北石炭二叠系紫色高岭石粘土的成因

晋北地区石炭二叠系煤层中与四号及九号煤伴生的含有机质的软质耐火粘土,即高岭石粘上,俗称紫矸或紫木节。对紫矸的成因过去有两种看法:(1)原生沉积的;(2)后期风化残积“由煤变来的”。笔者认为除这两个因素同时存在外,还与成岩后生作用中有机酸的淋滤和高岭石的重结晶、有序化等有关,尤其是后期风化表生作用使有机质氧化淋滤去SiO_2形成一水软铝石、褪色、溶蚀多孔、质地疏松,形成今日所见紫色高岭石粘土。

ON THE GENESIS OF THE BROWN KAOLINITE CLAY IN NORTHERN SHANXI PROVINCE

In the northern Shanxi province occurs some organic material-bearing clay which can be used as soft refractory material. The authors consider that the clay and the closely associated coal seam are formed by bog sedimentation on the sand mass in fluvial sediments. Clay were formed in high-level-peat-bog area while coal seam in low-level-peat-bog area. The weathered alumium silicates from the periphery of ancient continent are the source material of clay transported by water flow as suspension. There are some organic material coal in the clay.During deuterogenic processes kaolinite was strongly oriented without intense recrystallization. The clay was decolored with oxidation of organic material, formed as porous, losse kaolinitic clay or brown kaolinitic clay or boehmite-bearing clay (boehmite is about 30 percent) leaching during supergene processes.The clay is intercalated with a 10--20 or 20--30cm-layer of tonstcin composed of oriented kaolinite. This layer is more resistant to weathering, because of consists of flint clay with less TiO_2 and organic material and without boehmite. The others are inclined that the layer was formed as a result of colloidal precipitation.