Lithotectonic Complexes and Tectonic Evolution of the Palana Island Arc, Western Kamchatka

摘要

New data on the geological structure, age, and composition of rock sequences in western Kamchatka (the Palana area) are discussed. It has been established that the geological structure of the Palana area is composed of the Upper Cretaceous (occasionally, Lower Cretaceous) rock complexes formed in island-arc and marginal-sea settings. The studied volcanic rocks of the shoshonitic and calc-alkaline island-arc series accumulated in a common Palana island arc at different depths and, presumably, in laterally isolated areas. They were derived from several depleted and then metasomatically reworked mantle sources likely by partial melting of spinel peridotites that occurred in the upper mantle beneath this region. The composition of volcanic rocks is consistent with the fractional crystallization or anatectic melting of basic magmas. Tectonic movements in the island-arc/marginal-sea system apparently started in the mid-Cretaceous, although the main deformation and development of the fold-thrust structure took place at the Cretaceous-Cenozoic boundary in response to the closure of the marginal sea. The fold-thrust structure of the Palana area is characterized by western vergence with a sinistral strike-slip component. The Cenozoic was marked by several deformation stages that reflect accretionary processes in the easterly areas of Kamchatka.