摘要：The tuffs of the Yanchang Formation in the Or-dos Basin are sedimentary rocks generated under a special background. In-depth research will play an important role in analyzing and detennining the tectonic environment of the upper and lower strata in the tuff, the type of original basin, and the coupling relationship between the southern area of the Ordos Basin and the Qinling Orogenic Belt. In this paper, a number of modem analysis and testing techniques such as scanning electron microscopy, energy spectrum analysis and main trace elements are used to conduct in-depth research on the geochemical characteristics of the Yanchang Formation tuff. The results show that the tuff is mainly composed of fcld-spar and clay minerals. Tlic neutral igneous rock are mainly derived from the active continental margin and partly from the dynamic continental margin and the oceanic island arc. In the traditional sense, the Yanchang Formation tuffs arc divided into three types: tuffs with relatively weak volcanic ash alteration, obvious tuff structure, and relatively gentle HREE; porphyiy with strong volcanic ash alteration, vague tuff structure, and depleted HREE; Tuffs with relatively high Ba content, developed siliceous bands or silicalite, and enriched HREE.
关键词：Tuff interlayer rocks;geochemical characteristics;scanning electron microscope;major elements;Yanchang Formation
