Geodynamic setting and models of the emplacement of ophiolitic allochthons in the structure of accreted island arcs of the pacific north-western framing

Abstract

Based on the model of an oceanic island-arc breakup followed by accretion of rear and frontal parts of an arc to a continental margin of North-East Asia, the geodynamic nature of the ophiolites of Kamchatka and South Koryakia has been considered. The suprasubduction zone (SSZ) ophiolites originated in back-arc, fore-arc and intra-arc settings have been distinguished, and ophiolites of an ocean type have been distinguished only in one locality. The models of a SSZ ophiolites origin have been proposed. The emplacement of back-arc ophiolites has been supposed to be a result of the collapse (a closure) of a marginal basin, the emplacement of fore-arc ophiolites has been thought to be caused by their “pushing out” from a fore-arc basin, and the emplacement of the intra-arc basin ophiolites has been ascribed to a piling up of a newly formed basin crust before the beginning of the subduction. The emplacement of the ocean-type ophiolite in the front of the Olyutorsky folded structure has been attributed to a sliding accretion along the strike-slip fault movement related to the change in the motion direction of the Pacific plate 47 Ma ago.

Keywords

• офиолиты
• островные дуги
• субдукция
• аккреция