Intraplate magmatism and oceanic plate stratigraphy of the Paleo-Asian and Paleo-Pacific Oceans from 600 to 140 Ma

This paper reviews localities of intraplate basalts of the Paleo-Asian and Paleo-Pacific Oceans, which occur as fragments of former oceanic islands, seamounts and plateaus in accretionary complexes of Altai-Sayan, Russian Far East and Southwest Japan. Special emphasis is given to their relationships with associated rocks of oceanic plate stratigraphy (OPS), major and trace element chemistry and criteria for their identification in structurally complex orogenic belts. Accretionary complexes (ACs) host the Late Neoproterozoic–Early Cretaceous OPS units of the two paleo-oceans, which have a number of features in common: i) similar succession of oceanic sediments (pelagic chert – hemipelagic terrigenous slope facies – reef carbonates); ii) intraplate basalts occur at the bottom of the sedimentary sections and are usually overlain by a carbonate “cap”; iii) typical OIB-type chemistry of basalts is characterized by LREE–Nb–Ti enrichment. There is a 100 Ma time gap in the evolution of the oceanic intraplate magmatism, which is probably a result of our insufficient knowledge of other ACs of Central Asia. The study of intraplate magmatism and OPS of paleo-oceans is very important because it is an integral part of the study of orogenic belts incorporating many commercially valuable mineral deposits. Identification of intraplate OPS units should be based on a combination and mutual correlation of geological, lithological and geochemical features of basalts and their associated sediments. OPS units, both magmatic and sedimentary, provide a full geological record of the evolution of paleo-oceans from their opening, through subduction and formation of accretionary complexes, and finally to their closure accompanied by active tectonics, orogeny and ore mineralization.