«Proceedings of Gubkin University»

Classification and nomenclature of rocks composing basement weathering crust

UDC: 552.141, 552.181, 552.21, 552.22, 552.23
DOI: 10.33285/2073-9028-2022-3(308)-5-21

Authors:

¹ Gubkin Russian State University of Oil and Gas (National Research University), Moscow, Russian Federation

Keywords: weathering crust, basement, hypergenic-metasomatic class, Siberian platform, classification, nomenclature

Annotation:

Contrary to the generally accepted notion that the weathering crust is an intermediate element between the sedimentary cover and the basement, the paper proposes to consider the formation of the weathering crust as an independent geological object composed of its characteristic rocks. The attribution of weathering crust formations to rocks, with the resulting problems of classification and nomenclature, is a new direction of studying this object. The authors have developed a classification of the rocks of the weathering crust of the basement and the basis of the nomenclature (Sabirov, 2022). The principles of the classification hierarchy are presented according to the current petrographic Code, issued in 2009, under the auspices of VSEGEI. Despite the long history of studying weathering crusts, a number of fundamental issues related to their composition, spatial distribution and conditions of formation still remain unresolved. In particular, there is uncertainty in the attribution of the most intensively worked out or re-laid parts of the weathering crust to the basement or sedimentary cover. The problem lies in the fact that the structure and mineral composition of the formations composing the weathering crust retain many features of the original Early Precambrian rocks, and the geological bodies of the weathering crust actually lie according to the overlapping sedimentary cover deposits. Thus, theoretically, there are prerequisites for establishing the boundary “sedimentary cover-weathering crust”, however, it is often difficult to “highlight” it by geophysical methods without using core data, while the boundary “weathering crust-basement” is often not even distinguished, and there are no clear criteria for its determination. The development and systematic approach to the study of the structure and composition of the weathering crust rocks will create the basis for the effective development of additional hydrocarbon reserves that may be located in the reservoirs of the basement weathering crust rocks.

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