Density Structure of the Lithosphere of the Sikhote-Alin Orogenic Belt

For the first time, a detailed density 3D model of the lithosphere of the Sikhote-Alin orogenic belt to a depth of 130 km has been created. Two extended submeridional linear zones of low density are distinguished in the upper mantle and characterized. Large tin and gold deposits in the northern Sikhote-Alin are spatially confined to these zones. The present-day density structure of the lithosphere in the region, the formation of which began at the turn from the Late Jurassic to the Early Cretaceous, reflects its density differentiation resulting from the two main geodynamic processes: (1) a subduction regime replaced by a transform regime of the Bureya-Sikhote-Alin active continental margin, the stage (s) of which was (were) characterized by the emergence of mantle low-density zones, associated with the ascent of fluids and melts in the suprasubduction mantle wedge and the formation of intermediate magma chambers; and (2) intraplate rifting, spatially localized in zones of mantle thickening.