LITHOCHEMISTRY AND CONDITIONS OF SEDIMENTATION OF THE PALEOPROTEROZOIC IRON-SILICEOUS FOR-MATION OF THE KRIVOY ROG BASIN (UKRAINIAN SHIELD)

Based on modern lithochemical dataset statistical processing methods, the chemical composition features of the Paleoproterozoic iron ore (iron-siliceous) formation of the Saksagan Formation of the Kryvyi Rig basin of the Ukrainian Shield have been clarified with a view to improve the lithochemical systematics of the Precambrian iron-siliceous formations and to elucidate the general paleogeo-graphic (climatic, facies) conditions of their clastogenic-chemogenic sedimentation. A series of binary diagrams illustrates the relation-ship between iron-siliceous and shale layers. Using the cluster analysis method, lithochemical typification of shale rocks of the iron-siliceous formation was carried out: 12 "elementary" clusters were distinguished between two lithochemical groups and four subgroups separated by the mineral composition. The correspondence between lithochemical and mineral types of shale rocks has been indicated. The lithochemical types are arranged in a regular sequence, which corresponds to the initial authigenic-mineralogical and authigenic-lithofacial zonality of the sediments and allows, in general, denoting the facies isomorphic series of meta-sediments from metaclasto-genic to metachemogenic ones. An empirical classification diagram of rocks in the coordinates Al2O3 and (Fe2O3 + FeO) is proposed for dividing them into areas of chemogenic, chemogenic-clastogenic, and clastogenic sedimentation. The most iron-rich rocks – sec-ondarily unoxidized red-banded jaspilites – are characterized by the highest Fe2O3 / FeO ratio, which indicates their formation under shallow, well aerated conditions. The lithochemical features of the rocks in combination with the peculiarities of their occurrence, stratification and distribution confirm, on the whole, the protohumid type of lithogenesis in the conditions of low-lying shallow basins with a subplatform tectonic regime.

Abstract licence: CC BY-NC-SA

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