Uranium-bearing multi-element exogenic epigenetic deposits: Conditions of formation and sources of metals recovered by in-situ leaching

Numerous publications are concerned with the genetic problems of deposits o f uranium and associated elements and new methods of their in-situ leaching (ISL). However, the mechanisms of ore deposition from the infiltrational g roundwater on the reducing geochemical barriers in zones of stratal oxidati on of sediments by oxygen are poorly understood. This paper is focused on t he role of organic reducing agents in the formation of the ore-concentratin g geochemical barriers. We distinguish syngenetic, mixed, and epigenetic (r elative to the host rocks) reducers, which are important in the ore formati on during the solution-rock interaction. The role of acidic-basic interacti ons in this process is also considered. Particular emphasis is placed on th e sources of the ore-forming components of the multi-element deposits. Thei r polygenetic origin was demonstrated. The following two groups of elements are distinguished. The first group is composed of polyvalent elements accu mulating on the reducing geochemical barriers as insoluble compounds with e lements in low-valent state. Selenium, uranium, rhenium, molybdenum, copper , and vanadium can reach valuable accumulations in this association. The se cond group consists of univalent chemical elements that do not accumulate i n the natural physicochemical conditions of the exogenic infiltrational ore formation and are assumed to be diagenetic and sedimentary in origin. Thes e elements can be easily transferred to the technological sulfuric-acid sol utions, where they occur in concentrations high enough for commercial explo ration using ISL methods. This group includes scandium, yttrium, lanthanide s, and other rare and scattered elements, which form stable sulfate complex es in the H2SO4 technological solutions.