Petrographic and petro-geochemical compositions of Mesozoic (?) igneous rocks of the Polovinkinskaya depression (Aldan-Stanovoy shield)

The article considers the features of the petrographic and geochemical compositions of the Mesozoic igneous rocks of the Polovinkinskaya depression from earth bores K1, K2, K3, located within the central part of the Aldan-Stanovoy shield, on the boundary of the Tynda and Nimnyr terranes within the Amginskaya zone of tectonic mélange. Based on the relationship of rocks, as well as on the features of the petrographic composition, the following sequence of introduction and formation is assumed: 1) gabbro; 2) hornblende-augite andesites. This is confirmed by the values and variations of the petrochemical composition. According to the petrochemical and geochemical characteristics, gabbros are close to the tholeiitic series. Andesites belong to the calc-alkaline petrochemical series, latites of the shoshonite type. The presence of such rocks as gabbro and andesites is typical for mature island arcs and active continental margins, which does not contradict the existing ideas of predecessors. Similar in geological structure objects are gold-producing gabbro-tonalite-granodiorite-granite (GTGG) massifs of the Urals, which are supra-subduction formations on the active continental margin of the Andean type. The presence of rocks of the GTGG formation within the Polovinkinskaya depression serves as a favorable factor for noble-metal ore-generating processes.