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

As to the third ore-horizon by all explorers, inclusive of the present author, they are regarded as an ore of lacustrine origin. The author has had the possibility to establish that the mineralization of the top parts of the Upa limestones is connected with a zone of ancient conti­ nental weathering having taken place in Post-Upinian and Pre-Carboniferous time. It was realized at the expense of destruction of the subjacent Upa limestones holding inclusions of strongly weathered and, lower down, — of fresher pyrite. The ancient, Post-Upinian zone of continental weathering is represented by an areno-argillaceous rock, from 0 to 1,5 m. in thickness, containing the following minerals: limonite, gypsum, alimite, jarosite, kaolin, allophane, bauxite and inellite. In the adjoined summarized geological columnar section the author sepa­ rates the rocks of the ancient zone of continental weathering overlying the Upa limestone, as a special stratigraphic unit. To the main industrial ore horizons located between the Productus giganteus beds and the Upper Jurrassic deposits the author also gives an independent stra­ tigraphic significance. By a series of his detailed observations the author is proving that the ore- bearing areno-argillaceous rocks underlying the Productus giganteus beds present fossil lacustrine sediments. C o r r e s p o n d i n g l y , he r e g a r d s t h e i n d u ­ s t r i a l o r e o f t h e e n v i r o n s o f T u l a as a f o s s i l l a k e ore. In doing so, he is chiefly basing upon the following facts: 1) the ore bodies and associated rocks have a closed irregular form; 2) the ore bodies and ore-bearing rocks are confined to depressions in underlying rocks of Carboniferous age; 3) the ore- bearing rocks enclose clastic material derived from the Carboniferous rocks; moreover, the clastic material is much more abundant along the sides of the ore bodies (in the littoral zone) than in the central parts of the ore nests; 4) certain samples of the Tula ores have an external aspect which is not to be distinguished from the contemporaneous lake ores and 5) the ores are enclosed in areno- argillaceous rocks showing all the features of continental, fresh-water, lacustrine deposits. A certain ferruginous character of the Jurassic and Cretaceous rocks over- lying the ore-bearing horizon of sedimentary origin is explained by the author by an assimilation of the ore-minerals during the transgressive advance of the Jurassic and Cretaceous seas. The author many times observed in the Jurassic and Cretaceous rocks a clastic limonite, both in the form of pebbles and iri that of small grains. For the environs of Tula the author distinguishes the same genetic ore types, as those separated by him in the environs of Lipetsk (L. V. P u s t o v a l o v . Genesis of the iron-ores in the environs of Lipetsk after field observations in the summer of 1930). The author expresses the supposition that the lacustrine iron ores of the town of Lipetsk are formations belonging to the same geological age (P u s t o- v a l ov , L. V. What are the Tula and Lipetsk iron-ore districts? Vestnik G. Pr. S., 1931, №№ 3 — 4). The processes of secondary migration of iron in the environs of Tula are examined by the author in detail in a special paper ( P u s t o v a l o v , L. V. Pro­ cesses 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 in a crystal space lattice).