Пустовалов Л.В., Новые данные о происхождении липецких и тульских железных руд

form of the ore bodies; 3) the close connection of the ore accumulations with shallow-water deposits of continental-lacustrine type and 4) the presence among them of ores, morphologically identical with contemporaneous lake and bog ores. The ore-bearing sediments are confined to deposits, whose age is defined by B. S e m i k h a t o v and T. D a v y d o v a as coal-bearing СД The author is, however, not sure, in the correctnes of this determination and with more cau­ tion, defines the age of the ore-deposits as Post-Devonian and Pre-Upper Jurassic. The ore-bearing lacustrial deposits in the environs of Lipetsk are transgres- sively overlain by Upper Jurassic and Cretaceous (Cryvlug) rocks. It is therefore, not seldom observable that the upper parts of the ore-bodies are eroded by the Jurassic and Cretaceous transgressions. The author distinguishes four genetic ore-types in the environs of the town of Lipetsk: 1) primary ores (primary, sedimentary ores of lake or bog origin, still preserving their typical morphological features); 2) secondary ores (also in primary occurrence, having suffered no local secondary regrouping and alteration of minerals); 3) redeposited ores (enclosed as clastic material in the Jurassic and Cretaceous rock capping the ore-body), and 4) metasomatic ores (arising due to penetration of iron from the sedimentary ore-bed into the subjacent rocks, chiefly into Devonian limestones). The main bulk of the iron ores in the environs of Lipetsk consists of ores of the first and second type; they are represented exclusively by limonite. Meta­ somatic ores play in the environs of Lipetsk an insignificant subordinate r6le. Processes of secondary migration of iron in the rocks of the environs of Lipetsk are examined by the author with more detail in a special paper (L. V. P u s t o v a l o v : Processes of migration of iron in the Lipetsk and Tula iron-ore districts. L i e s e g a n g ’ s phenomena in a coarse dispersion medium and crystal space lattice).