Compositional variation of glauconites in Upper Cretaceous-Paleogene sedimentary iron-ore deposits in South-eastern Western Siberia
| Parent link: | Sedimentary Geology Vol. 355.— 2017.— [P. 20-30] |
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| Summary: | Title screen Glauconite occurs either as unaltered greenish or as altered brownish variety in Upper Cretaceous-Palaeocenesediments in the southeastern corner of Western Siberia. Studied section within the Bakchar iron-ore depositincludes Ipatovo, Slavgorod, Gan'kino and Lyulinvor formations, which are represented by sandstones, siltstones,claystones and oolitic ironstones of coastal-marine facies. The origin of unaltered glauconite is explained by the“verdissement theory”. Transgressions during Lower Coniacian, Santonian and Campanian favored the formationof unaltered glauconites in dysoxic to anoxic conditions. Subaerial exposure of glauconite resulted in leaching ofpotassium, oxidation of iron and formation of iron hydroxides in Upper Coniacian, Maastrichtian and Palaeocene.Glauconite ultimately converts to leptochlorite and hydrogoethite by this alteration. Abundant microscopic goldinclusions, besides sulphides, sulphates, oxides and silicates characterize this glauconite. Mineral inclusionsinclude precious, rare metals and non-ferrous metals. The concentration of gold in glauconite may be as highas 42.9 ppb. Abundant inclusions of various compositions in glauconites indicate enrichment of marinesediments in precious and non-precious metals. While major element composition of glauconites is affected bysubaerial exposure, the broadly similar micro-inclusions in both altered and unaltered varieties are possiblyrelated to the comparatively immobile nature of REE and trace elements. Режим доступа: по договору с организацией-держателем ресурса |
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2017
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| Online Access: | https://doi.org/10.1016/j.sedgeo.2017.04.006 |
| Format: | Electronic Book Chapter |
| KOHA link: | https://koha.lib.tpu.ru/cgi-bin/koha/opac-detail.pl?biblionumber=655804 |