Geodynamic setting of the high-grade amphibolites and associated igneous rocks from the accretionary complex of Povorotny Cape, Taiganos Peninsula, northeastern Russia

The petrology and geochemistry of high-grade amphibolites and associated ga bbro, volcanic rocks and peridotites from Povorotny Cape (northeastern Russ ia) are considered with the aim to examine the geodynamic setting of differ ent rock complexes related with the accretionary structure of this area. Ge ochemical and petrological evidence indicates that the following two predom inant groups of igneous rocks were involved in the construction of the Povo rotny Cape accretionary structure: (1) MORB and within-plate members (proto lith of high-grade amphibolites, gabbro, dolerites, volcanic rocks and spin el lherzolites; (2) different products of suprasubduction magmatism, includ ing boninites (gabbro and ultramafic cumulates, dolerites, volcanic rocks a nd spinel harzburgites). The P-T metamorphic conditions of the rock assembl ages indicate that the Povorotny Cape rock complexes were affected by two m ain metamorphic events. The first corresponded to high-pressure-medium-temp erature conditions and was unique to the high-grade amphibolite, and the se cond occurred in the form of low-temperature recrystallization under greens chist-facies conditions and manifested itself in virtually all igneous rock s of Povorotny Cape and in part of the high-grade amphibolites. The igneous and metamorphic rock complexes of Povorotny Cape were formed during the fo llowing main tectonic episodes: (1) generation of MORB and within-plate mag matic rock assemblages (gabbros, dolerites and volcanic rocks), including r esidual peridotites in an oceanic basin; (2) subduction of part of these ro cks to a relatively shallow position within a warm subduction zone, while t he remaining oceanic lithosphere was detached and tectonically incorporated into a suprasubduction complex; (3) formation of a suprasubduction magmati c complex that included a boninite series; (4) exhumation of the high-grade amphibolites and spinel lherzolites and their tectonic mixing with the oce anic and suprasubduction igneous complexes. (C) 2000 Elsevier Science B.V. All rights reserved.