THE PHENOMENON OF RAPID ACCUMULATION OF SEDIMENTS BELONGING TO THE UDOKAN GROUP AND THE FORMATION OF THE UNIQUE UDOKAN COPPER DEPOSIT (ALDAN SHIELD, SIBERIAN CRATON)

Abstract

We analyzed new geological and geochronological data on sedimentation and metamorphism in the junction area of the Aldan and Stanovoy Superterranes comprising the southern flank of the Siberian craton. The analysis was focused on early Proterozoic deposits belonging to the Udokan group. It is confirmed that highly metamorphosed rocks at the base of the Udokan group (Kolar subgroup of the Stanovoy suture zone) differ sharply from other rock associations included in this group (Chiney and Kemen subgroups of the Aldan Superterrane). They differ in the degree of metamorphic alterations, style of tectonic deformation, igneous complexes intruding them, and show a complete lack of copper mineralization. There are thus grounds to exclude the Kolar subgroup from the Udokan group. According to our data, the age of the sediments in the Udokan group, including the Chiney and Kemen subgroups, is 1.90‒1.87 Ga, i.e. in the study area, sedimentation lasted for no more than 30 Ma and proceeded simultaneously with the copper mineralization within the intracontinental extensional basin at the stage of collapse of the early Proterozoic orogen.