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Russian Geology and Geophysics

2013 year, number 4

KINEMATIC RECONSTRUCTION OF THE EARLY CALEDONIAN ACCRETION IN THE SOUTHWEST OF THE SIBERIAN PALEOCONTINENT BASED ON PALEOMAGNETIC RESULTS

D.V. Metelkin
Keywords: Early Caledonian tectonic stage, kinematics, accretion, subduction, strike-slips, island arc, Siberian paleocontinent, paleomagnetic pole, paleotectonic reconstructions

Abstract

The kinematics of the Early Caledonian accretion process in the southwest (in modern coordinates) of the Siberian paleocontinent and the structure of its active continental margin are debatable subjects. This paper contains a generalization of paleomagnetic data on island-arc terranes of the AltaiSayan and BaikalVitim folded areas for the Late Vendian/CambrianEarly Ordovician interval, obtained mostly with the authors participation during the last two decades. The large accumulated database finally allows one to find unambiguously interpretable patterns in the distribution of paleomagnetic poles for the analyzed terrane system and to justify numerically the kinematics of the Early Caledonian accretion. In particular, the analysis of paleomagnetic data proves our idea stating that the transformation of the active continental margin in the Cambrian consisted in its breakup and segmentation as well as the detachment of fragments of the initially whole island arc along a system of sinistral strike-slips during the clockwise rotation of the craton and conform drift of the continental and oceanic lithospheric plates. This also validates the mostly oblique conditions of the subduction and subsequent accretion, which means a subduction-transform mode on the oceancontinent margin. We propose complemented version of the paleotectonic reconstruction for the Cambrian evolution of the western margin of the Siberian continent, based on the kinematic scheme constructed from paleomagnetic data.