Petrogeochemical conditions and geodynamic settings of volcanic rocks in the Kiselyovka-Manoma accretionary complex (Russian Far East).

The Kiselyovka-Manoma accretionary complex formed at the end of the Early Cretaceous during subduction of the Pacific oceanic plate underneath the Khingan-Okhotsk active continental margin along the east of Eurasia. It is composed of Jurassic-Early Cretaceous oceanic chert, siliceous mudstone, and limestone that include a significant amount of basic volcanic rocks. The known and newly obtained data on the petrogeochemistry of the Jurassic and Early Cretaceous basalt from various parts of the accretionary complex are systemized in the paper. Based on the comprehensive analysis of these data, the possible geodynamic settings of the basalt are considered. The petrogeochemical characteristics provide evidence for the formation of basalt in different parts of the oceanic floor within the spreading ridge, as well as on oceanic islands far from the ridge. The basalts of oceanic islands are mostly preserved in the accretionary complex. The compositional variations of the basalts may be controlled by the different thickness of the oceanic lithosphere on which they formed. This is explained by the varying distances of the lithosphere from the spreading zone. [ABSTRACT FROM AUTHOR]