川南须家河组第四段TONSTEINS的岩石地化特征

对四川南部上三叠统须家河组第４段（Ｔ３ｘｊ＾４）中的５层ＴＯＮＳＴＥＩＮＳ做了较详细的岩石学、地球化学研究。结果表明，它们都是同沉积的酸性火山灰，在泥炭沼泽环境下，经过水解和后期成岩作用，转变成质地较纯的高岭石粘土岩。ＴＯＮＳＴＥＩＮＳ的岩石结构类型较简单，以致密型和团粒－致密型为主，结晶型较少。同层ＴＯＮＳＴＥＩＮ的岩石结构的某些亲石元素含量及组合关系在较大范围内保持稳定，并具有显著的标志性；Ｔ

PETROLOGIC AND GEOCHEMIC CHARACTERISTICS OF TONSTEIN IN THE 4 TH INTERVAL OF XUJIAHE FORMATION IN SOUTHERN SICHUAN

Five seams of mudstone from the 4 th interval (T 3xj 4)of Xujiahe formation in Southern Sichuan were geochemically and petrologically researched in detail. Results have shown that the TONSTEINS are all synsedimentary acid volcanic ash,which were turned to relatively pure kaolinitic mudstone through hydrolysis and diagenesis in peat moor environment.For these mudstones the types of lithological texture are relatively simple,dominated by compact or crumby-compact textures.The types of lithological texture,the content of lithophile elements and their composite relations are stable in large area.They are very important marked beds for regional coal-seam correlation and for chronostratigraphic framework establishment.