Comparative analysis of typical gold-bearing districts restricted to terrigenous-schistose bedsof southern border of the North-Asian craton (geodynamics of formation, structural features, metallogenic potential)

The comparative analysis of two gold-bearingdistricts (Bodaibinsky and Selemdzhinsky) localised among the terrigenous-schistose beds of the southern border of the North-Asiancraton showed a certain similarity in the formation and structure of the objects under comparison, as well as in the individual features oftheir geological development. The similarity is manifested by the restriction of the districts to the joint of the different-oriented gravityfield gradient zones of orders I and II, identical thickness of the earth's crust, fold-thrust structure of the ore-enclosing deposits, presenceof carbonaceous terrigenous accumulations, metamorphism of sediments of different intensity (from epidote-amphibolite to phyllitefacies) with predominant green-schist facies, manifestation of tectonic-magmatic activity, and similar scenario of the formation of oreplacer concentrations (availability of ore-preparation periods governing the accumulation of precious metals in the intermediatecollectors, change of ore-preparation periods by ore-generation stages that completed the redistribution of precious-metal mineralizationwith Au concentration, and manifestation of placer-forming stages responsible for the accumulation of gold in loose deposits).Individual features of geological development of the gold-bearing districts under comparison allow the explanation of a different levelof their metallogenic potential. These are the geodynamic regimes of the sedimentary bed accumulation (riftogenic trough inBodaibinsky district and subduction trench in Selemdzhinsky one), periods of sedimentation and their duration (Proterozoic-Palaeozoicin the trough and Palaeozoic in the trench), lithological composition of sediments (carbonate-terrigenous in the trough andvolcanogenic-terrigenous in the accretionary prism), time of ore generation (Late Palaeozoic in Bodaibinsky and Late Mesozoic inSelemdzhinsky), geodynamic conditions of ore generation (regime of the passive margin in Bodaibinsky and the transform margin inSelemdzhinsky), and petrochemical composition of ore-generating magmatic complexes (predominantly granitoid in Bodaibinsky andessentially andesitoid in Selemdzhinsky). Among the particularly important distinctive features that cardinally influenced the formationof the metallogenic potential of the districts compared are the geodynamic regimes of sedimentation and ore genesis. In this connection,the geodynamic factor is necessary to be taken into account in the prediction evaluation of gold-bearing territories of the total border ofthe North-Asian craton.

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