STRUCTURE-FACIES AND TECTONIC DIVISION OF SOUTHER SIKHOTE-ALIN

A new scheme of structural-facial and tectonical subdivision of South Sikhote-Alin is proposed. The whole of the territory is subdivided into three structural-facial zones: Grodekovo, Khankay and Sikhote-Alin. The Grodekovo zone occupies the western part of the Primorye region, shows a meridional strike and is distinguished from other zones by a wide distribution of thick volcanic and volcanic-detrital Permian deposits of the geosynclinal type, an abundance of great upper Paleozoic granitoid intrusions and continental facies of Mesozoic and Cenozoic sediments. The Sikhote-Alin zone of the Sikhote-Alin geosyncline proper represents a complicated structure in consequence of repeated, sometimes intensive tectonic movements, resulting in an unequal deformation of different parts of the geosyncline; the downwarping of the latter was widespread and continuous at one time and differentiated and quickly replaced by uplifts at another. The Sikhote-Alin geosyncline deposits are grouped as follows: schistose (Devonian - Lower Carboniferous); siliceous-terrigenousspilitic (chiefly upper Paleozoic); terrigenous, enclosing flysch and flysch-like formations (Mesozoic); volcanic (Mesozoic-Cenozoic); and continental (of Tertiary tectonic depressions). The latter two refer to the geanticlinal stage of development of Sikhote-Alin. The territory under consideration represents an area of Paleozoic folding considerably reworkedby powerful Mesozoic movements, clearly reflected in the following zones: 1) Inner zone—zone ofintensely dislocated Mesozoic (including lower Senonian) deposits, penetrated by numerous, sometimesbig intrusions. 2) Outer zone-zone of less intensely dislocated Mesozoic deposits overlyinga shallow and exposed Paleozoic basement. Mesozoic magmatism is clearly manifested but lessabundant than in the former zone. 3) Subplatform of Mesozoic folding, characterized by the presenceof only slightly crumpled or practically uncrurnpled Mesozoic deposits and by the absence, or quiteinconsiderable development of post-Paleozoic intrusive activity. The structure of the zones is complicated;they are subdivided into geotectonic units of lesser dimensions. —Auth. English Summ.