Horizontal and vertical zonation of the weathering rind of the northern part of the Krivy Rig Basin

S. V. Tikhlivets,O. M. Trunin

doi:10.15421/111955

Abstract

The ferriferous-siliceous formation of the Kryvyi Rih Basin has been formed as a result of the effect of different geological processes: sedimentation, diagenesis, dynamothermal metamorphism, metasomatosis, orogenesis, hypergenesis. Hypergenic changes are manifested to a different extent within iron ore deposits of the Kryvyi Rih Basin. In the south part of the basin, thickness of the weathering rind in some places reaches 1,000-1,500 m, it is up to 2,500 in the central, and in the northern part this parameter is much lower. Hypergenic processes are observed in the sections of all stratigraphic horizons of the Saksahanska suite of the iron ore deposits of the Kryvyi Rih Basin. The thickness of their manifestations changes depending on the horizon (schist, ferriferous). Therefore, over the study, we determined the impact of stratigraphic horizon on variance of thickness of the weathering rind within the northern area of the Kryvyi Rih basin, on example of the Hannivsk deposit. The surveys were performed in all hypsometric levels of the deposit. Schematic sections of the deposit`s weathering rind were made. The products of hypergenesis are hematite quartzites with qualitative parameters (total content of iron) no lower than in magnetic quartzites. In some deposits, the reserves of the hematite quartzites are quite large, but they are not being extracted. For more detailed study of the structure of the weathering rind, manifestation of its vertical zonation was investigated, a schematic section of the weathering ring within the ferriferous-siliceous formation of the deposit was made designating all mineralogical zones. We studied the variance of mineral composition of the ferriferous rocks depending on the manifestation of horizontal zonation of the weathering rind and impact of hypergenic processes on authigenic-metamorphogenic zonation of the productivity of the deposit`s layer. We developed a scheme of mineralogical zonation of the weathering rind, therefore facilitating the enlargement of the mineral-ore base of the Hannivsk deposit and the Kryvyi Rih Basin in general for further extraction and beneficiation of hematite quartzites.

Highlights

The processes of weathering are manifested in the layer of ferriferous-siliceous formation of the northern part of the Kryvyi Rih Basin and within the Hannivsk deposit due to interruptions of accumulation of sediments (Bespoyasko, 2005.; Ginzburg, 1987; Dmitriev, Kravchenko, 1965)
In the sections of the weathering rinds of all stratigraphic horizons of the Saksahanska suite, horizontal hypergenic mineralogic zonation of higher order is manifested, which was inherited during the weathering from their original authigenic-metamorphogenic geochemical zonation (Karpenko,EvtekhovV., EvtekhovaA., 2009)
The obtained data demonstrate that the thickness of the weathering rind of the Hannivsk deposit of the Kryvyi Rih basin changes from the northern to southern part of the deposit with the following pattern: in the central part it has highest value; towards the northern and southern part, thickness of the weathering rind significantly sixth ferriferous horizons

Summary

Introduction

The processes of weathering are manifested in the layer of ferriferous-siliceous formation of the northern part of the Kryvyi Rih Basin and within the Hannivsk deposit due to interruptions of accumulation of sediments (Bespoyasko, 2005.; Ginzburg, 1987; Dmitriev, Kravchenko, 1965). In the goethite-martite zone, it is practically absent (0.47 vol%), within the martite zone its amount equals on average 1.78 vol%; within the magnetite-martite zone – 12.49 vol%; within the martite-magnetite zone it functions as a rock-forming mineral (23.06 vol%); maximum content of magnetite was observed in the original non-weathered ferriferous rocks (35.83 vol%) This is explained by the decrease in activity of hypergenic processes with depth. In the sections of the weathering rinds of all stratigraphic horizons of the Saksahanska suite, horizontal hypergenic mineralogic zonation of higher (second) order is manifested, which was inherited during the weathering from their original authigenic-metamorphogenic geochemical zonation (Karpenko,EvtekhovV., EvtekhovaA., 2009) It was observed most completely in the section of productive layers. According to generalization of the results of the mapping of the faces of the quarry, made by the author, and data of boring of the exploration wells, a topomineralogical scheme of weathering rind of the Hannivsk deposits productive layer has been developed (Fig. 8)

Conclusions

Geological and Mineralogical Bulletin of Kryvyi