Hydrogeology of the Archean Crystalline Rock Massif in the Southern Part of the Yenisseyskiy Ridge (Siberian Craton)

Abstract

The manuscript deals with the hydrogeological condition of Archean rock massif investigated for underground building of radioactive wastes isolation. Exploration methods included well boring up to depth of 700 m, geophysical logging, hydrogeological pumping tests; water and rock sampling. Pumping tests carried out with systematically scaled intervals of 50 meters isolated by packers. Water samples were tested with chemical methods for main ions, ICP MS for trace elements and for radioactivity. Rock samples were tested in porosity, permeability, chemical composition, physical properties. Rock massif is represented by lower Archean gneisses pierced b y dykes of dolerite. All rocks have very low reservoir properties due to an intense metamorphism. Laboratory tests have indicated that an average open porosity is equal to 0.33%. Almost 70% of obtained values of hydraulic conductivity belong to the range of 0.0001 m·day-1 – 0.001 m·day-1, while average hydraulic conductivity is equal to 0.004 m·day-1. There were found four vertical zones depending on the bases of drainage and differing in rock permeability and filtration conditions. The TDS of groundwater varies from 140 to 641 mg·L-1, the type of water is HCO3–Na–Ca, water has alkaline and reductive media.