Stages of Late Proterozoic magmatism and periods of Au mineralization in the Yenisei Ridge

摘要

Geological, isotopic, and geochemical data permitted distinguishing the Mesoproterozoic (1.6-1.05 Ga), Early Neoproterozoic (1.05-0.8 Ga), and Late Neoproterozoic (0.8-0.6 Ga) stages of magmatism and crustal evolution in the Yenisei Ridge. Each of them contributed to the regional Au metallogeny. In the Early Mesoproterozoic, crustal destruction and stretching in the southwestern Siberian craton (Yenisei Ridge) led to the initiation of a pericratonic trough, the formation of rift mafic associations (Rybnaya-Panimba volcanic belt), and the accumulation of fine-grained terrigenous sediments (Sukhoi Pit Group). Black carbonaceous shales and the picrite basalt-basalt association were enriched in Au. In the early Neoproterozoic, the terrigenous strata of the Sukhoi Pit Group were deformed, metamorphosed, and granitized as a result of the Grenville orogeny. Granite-gneiss domes formed in the earlier, syncollisional, period (1.05-0.95 Ga) of this stage, and K-Na granitoid plutons formed in the late collisional one (0.88-0.86 Ga). Premineral metasomatites formed in the zone where these plutons influenced enclosing black shale-terrigenous strata. They host Au deposits, which formed later. The formation of quartz-reef zones correlates with that of thrust nappes (0.85-0.82 Ga). The latter is genetically related to the final stage of the evolution of a collisional orogen. In the Late Neoproterozoic, rift and intraplate magmatism was most intense and frequent (780, 750, 700, 670-650 Ma) in the Tatarka-Ishimba fault system. Manifestations of Mesoproterozoic volcanism and all the Au deposits of the Central metallogenic belt in the Yenisei Ridge are concentrated here. The three periods of gold-arsenopyrite-quartz, gold-sulfide, and Au-Sb mineralization correlate well with the initiation and evolution of rift structures and the manifestations of intraplate magmatism at 800-770, 720-700, and 670-650 Ma. The tectonomagmatic processes which took place in these periods might have been crucial in Au ore accumulation.