New data on the composition of ophiolites from the Kumroch-Valagin segment of the Achayvayam-Valagin paleoarc (Eastern Kamchatka)

This study presents new data on the geochemistry and mineral chemistry of ultramafic and mafic rocks in ophiolits from the base of the Kumroch segment of the Achayvayam-Valagin paleoarc. The new data enabled us to consider peridotites and the associated diabases and gabbros enclosed as separated blocks into a serpentinite mélange as a single ophiolite complex formed in a supra-subduction setting and subsequently disintegrated as a result of nappe formation. The variations identified in the geochemistry and compositions of rock-forming minerals are shown to be characteristic of the other study ophiolite complexes of Eastern Kamchatka. This is suggested to reflect spatial-temporal heterogeneity of partial melting during evolution of the Achayvayam-Valagin island arc.