滇东黔西晚二叠世煤系中火山灰蚀变粘土岩的元素地球化学特征

对滇东?黔西晚二叠世煤系中同沉积火山灰蚀变粘土岩夹矸?正常沉积粘土岩和煤层共采46件样品,用多种仪器分析方法测定微量元素30余种?研究表明,煤系各层段中赋存的夹矸是由性质不同的火山灰沉积蚀变形成的,各层夹矸的微量元素含量及组合关系各有特点并在较大范围内保持良好的稳定性,可用于判定层位;正常沉积粘土岩与夹矸的原始物质性质不同,其微量元素含量和组合面貌各有自己特定的分布范围,两者易于区别?

Element Geochemistry of Volcanic Ash Derived Tonsteins in Late-Permian Coal-Bearing Formation of Eastern Yunnan and Western Guizhou,China

Over 30 trace elements(with concentration lower than l%o) from 46 samples have been determined during the study by various techniques,including INAA and ICP. These samples were collected from the synsedimentary volcanic ash derived tonsteins, non-cineritic claystones, and the coal seams within the coal-bearing formation of the eastern Yunnan and western Guizhou Provinces. The analytical results demonstrate the fact that the concentrations of various trace elements source materials. The terrigenous non-cineritic claystones are characterized by their high contents in V,Ti,Sc,Cr,Co, and Ni,medium contents in Nb, Ta, Hf, Zr and REE,and low in The U and Th/U ratio,with an indistinct negative anomaly of SEu(0. 63-0. 93),which is, in overall, consistent with the properties of the basalt from the erosional region. On the other hand,tonsteins are low in V,Ti,Sc,Cr,Co, and Ni, contents, medium to high in REE,Nb,Ta,Hf,Zr, Th and U, and high in Th/U ratio, with a distinct bEu anomaly (normally in the range of 0. 2-0. 4 ). The characteristics of tonstein geochemistry of trace elements can be distinguished from those of the non-cineritic claystones, as indicative of their unique volcanic ash-fall origin. As far as the tonsteins are concerned,those from the lower section (P_2.1) of the coal-bearing formation are high in Li,13e, Ti, Zr, Hf, Nb, Ta and REE contents, as compared to those from the middle and upper sections (P_2.2+3). As shown on the plots of correlations between Hf-Ta,Ti-Ta,Ti-V,Hf-Sc, Lu-Hf and Lu-Th,tonsteins from P_2.1.1horizon always fall in an isolated distribution area,separating from the tonsteins of P_2.2+3 horizon. These results suggest that from the tonsteins from the two different horizons were probably derived comparison of the concentration and assemblage of trace elements between various magmatic rocks, the source materials of tonsteins from Pz.1horizon were mostly compased of alkalene volcanic ash,whereas those from Pz.z+a were apparently acidic. Based on a convergence of evidence obtained from different approaches,including the analytical results of the distribution and assemblage of trace elements in tonsteins, it is discovered that the tonsteins from different horizons are ofter characterized by their unique properties,which remain quite consistent over a great lateral extent. An integrated and customized use of these properties makes possible the establishment of tonstein stratigtaphy, thus facilitating the more precise and reliable coal seam correlation.