Genesis and tectonic significance of the Early Cretaceous intermediate volcanic rocks in Chaihe-Moguqi area, central Da Hinggan Mountains

In this paper, the authors studied the Early Cretaceous intermediate volcanic rocks in Chaihe-Moguqi area, central Da Hinggan Mountains. The intermediate volcanic rocks consist of andesite, dacite, intermediate lava and tuff, formed from ~140 to ~130Ma. Chemical analyses show that the intermediate volcanic rocks are classified as high-K calcalkaline volcanic rocks, and are characterized by enrichment of light rare earth elements (LREEs), large ion lithophile elements (LILEs), Ba, Sr, and depletion of heavy rare earth elements (HREEs), high field strength elements (HFSEs), with no distinct Eu anomalies. All the geochemical characteristics suggest that the Early Cretaceous intermediate volcanic rocks were derived from the partial melting of a juvenile lower crustal basaltic rocks, and might have been affected by the fluid caused by earlier subduction event. The authors hold that the generation of the Early Cretaceous intermediate volcanic rocks was related to the lithospheric extensional setting after the final closure of the Mongol-Okhotsk Ocean and subsequent continental thickening.