Paleostress study of the Kvartsevoe rare metals deposit, East Kazakhstan

The Kvartsevoe rare metal deposit in East Kazakhstan was discovered in 1967 and is being currently re-evaluated after decades of inactivity. The geology of the area consists mainly of Devonian to Carboniferous metasediments, folded during the latest consolidation phase of the Altai orogen (i.e. Late Carboniferous-Permian) and intruded by series of post-kinematic Permian granites. Metals and elements of economic interest, in particular Lithium, are found in a ~300 m wide and ~700m long pegmatite body, associated with medium-earth biotite granites of phase II of the Kalba complex (i.e. 286±1 Ma). The deposit is represented by a series of pegmatite veins located in one of the projections of the Alypkelsky granite massif, the sedimentary host rocks near the deposit are hornfels of variable metamorphism up to the point of transformation into tourmaline-graphite-quartz-mica hornfels. Numerous quartz veins are found in the close vicinity of the Kvartsevoe deposit. Field observations suggest that the latter veins are genetically linked to the pegmatites. They cross-cut Permian granites and Paleozoic metasediments, show regular trends and typically extend 10s to 100s of metres. We conducted an integrated geochemical-structural study of the veins. Our preliminary results suggest vein emplacement under strike-slip stress regime with NW-SE orientation for the axis of minimum principal stress. The study seems, in addition, to confirm the genetic link between the veins and the pegmatites. Therefore, our findings suggest that the pegmatites were also emplaced under the same stress field. This latter result may be used in the future to predict the orientations of the pegmatites hosting economic metals in the subsurface.