Литосфера (Jan 2020)
Large and super-large orogenic golden deposits: Geodynamics, structure, genetic consequences
Abstract
Research subject. Large and super-large orogenic gold deposits are widely distributed across all continents. This work was aimed at characterizing 24 giant facilities with reserves and resources of more than 500 tons of metal.Materials and methods. The work was based on the authors’ long-term fieldwork research into large and super-large gold deposits in Central Asia and the North-East of the Russian Arctic. In addition, an extensive bibliographic analysis of publications devoted to the largest gold deposits in the world was carried out.Results. A structural analysis showed that the formation of these deposits underwent two main stages. The early – subduction stage – was characterized by the development of gentle disturbances, such as thrusts, thrust nappies, viscous discontinuities and crushing zones, while the structural paragenesis included isocline lying folds and cleavage of the axial surface. The second stage – collision-transpression – began with the deformation of the previously formed structure into open and compressed folds with steep axial surfaces; as a result of further compression, a series of longitudinal discontinuous disturbances developed. An oblique collision of interacting plates lead to the development of shear transpression structural paragenesis, in which oblique cracks predominate. It is established that, in orogenic gold deposits, different stages were characterized by ore-controlling and ore-bearing structures. The binding of ore-bearing disturbances to different stages enabled isolation of deposits of various types that differ in structural and morphological features. The main characteristics of the identified types of deposits are provided. The formation of these deposits occurred during convergent processes, with the ore-controlling structures being a surface manifestation of the movement of block terrains along the surface of the detachment.Results. It is concluded that the surface of the detachment is not only a tectonic zone, but also a channel that provides a link between various deep levels of the subduction zone, from where ore-bearing hydrothermal fluids emerge.
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