Engineering and geological zoning of the Malmyzhsky deposit weathering crusts (Svoboda area)

Introduction. Interest in the study of weathering crusts arose at a time when geological engineers faced the problem of developing open pits formed by eluvial soils. However, the exact and detailed division of the weathering crusts into engineering-geological zones, especially when studying mineral deposits, is not given due attention even today. Therefore, in the course of prospecting, it is important to correctly determine weathering crust type and profile, and establish the possibility of changing the engineering and geological conditions when opening the rock mass by mine workings for further slope stability prediction of the designed mining structures. Research aim is to determine vertical engineering-geological zoning of the Malmyzhsky deposit weathering crusts (Svoboda area) and identify patterns in alluvial deposits physical and mechanical properties change, which define the safety of mine development. Methodology. A significant number of Russian and foreign scientists have considered the formation of weathering crusts from different positions. They established the geochemical zoning and engineeringgeological zoning of the weathering crusts. Results. The article describes the Svoboda area at the Malmyzhsky gold-copper-porphyry deposit. Engineering and geological zoning of the weathering crust section was carried out according to a set of features, including structural and textural features, mineral composition, physical and mechanical properties of rocks. Within it, three zones are identified at the Malmyzhsky field, the Svoboda area: IV – dispersed, III – litomarge, and II – clastic. Physical and mechanical properties of rock building up the considered weathering crust have been analyzed proving that change in geological conditions within even one zone of the Malmyzhsky gold-copper-porphyry deposit (Svoboda area) entails a change in the choice of projected pit wall angles.

RYBACHY SITE AS AN OBJECT FOR ADDITIONAL STUDY OF GOLD-BEARING WEATHERING CRUSTS (SIKHOTE-ALIN)

The paper deals with the problem of assessing the gold content of pre-Quaternary weathering crusts, which are widespread in the foothills of the doming-block geomorphological structures of the Amur Region, Khabarovsk and Primorsky Territories, by framing large and medium-sized Cenozoic depressions and depressions. For a more detailed mining and geological study and assessment of the gold content of the weathering crusts, we recommended the Rybachy site as one of these objects (not fully studied), and the entire Mukhenskaya area as a promising one.

ON THE GOLD MINERALIZATION IN WEATHERING CRUSTS OF THE RYBACHY SITE (WESTERN SIKHOTE-ALIN)

The author addresses an issue of gold presence in pre-Quaternary crusts of weathering that are widespread in sub-mountain areas of the doming-block geomorphological structures of the Amur Region, the Khabarovsk and Primorsky Territories along the periphery of large- and medium-sized Cenozoic basins and depressions. For a more detailed mining and geological study and assessment of the gold content of the weathering crusts, we recommended the Rybachy site as one of these objects (insufficiently studied), and the entire Mukhenskaya area as a promising one. These sites are located in the zone of articulation of the eastern side of the Middle Amur Depression with the folded structures of the West Sikhote-Alinsky volcanic belt. The author gives examples of large gold deposits, related to weathering crusts with their brief description (Olympiada, Kuranakh), as well as a brief description of alluvial deposits of weathering crust (sub-basalt cl.Paskhalny, an eluvial-alluvial placer of the Bolotisty Stream). The search work of the DVIMS (Far Eastern Institute of Mineral Raw Materials) in 2002 indicated the potential of weathering crusts within the Rybachy prospect for gold mineralization. This is supported by elevated gold in heavy mineral concentrates from the linear weathering crusts and residual blankets, as well as from non-commercial placers (from 0.01 to 4.0 g/t and higher); the occurrence of fracture zones, brecciation, secondary silicification close by fractures, and abundant Late Cretaceous silicic and intermediate dikes. Zones of hydrothermally altered rocks (silicification, chloritization, sericitization, argillization) are widespread here.