Evolution of Aptian and Albian magmatism of Western and Northern Chukotka (Northeast Russia) based on zircon U-Pb geochronology and rock geochemistry

Across western and northern Chukotka, a region spanning 400 000 km2, we have defined three different tectono-magmatic systems that were active during the Aptian-Albian (123–100 Ma) time span: (1) the Tytylveem post-collisional belt (123–105 Ma); (2) the Chaun province of extension-related magmatism (109–100 Ma); and (3) the earliest eruptive units (106–100 Ma) of the subduction-related Okhotsk-Chukotka volcanic belt (OCVB). The observed tectono-magmatic systems are characterized by their location and by their different chemical and isotopic compositions. The general enrichment of magma sources successively increases from the OCVB to the Tytylveem belt and then to the Chaun province. While the Tytylveem belt was active, the volcanic loci shifted northwest along the strike of the belt, perhaps because of diachronous delamination of the lithosphere of the once present, but extinct, South Anyui ocean. On the scale of the entire region of NE Asia, the tectonic re-arrangement that controlled magmatism in the Early Cretaceous was marked by the extinction of major subduction zones on the periphery of the closing Oimyakon and South Anyui oceanic basins followed by magmatic events likely caused by lithospheric delamination and/or extension. Along the Pacific margin of Asia, subduction-related volcanism was nearly continuous during the entire Cretaceous.在面积达40万平方千米的楚科奇西部与北部区域，我们识别出3套形成于白垩纪阿普第期-阿尔布期（123~100 Ma）的构造-岩浆系统，其活动时限分别为：（1）提季尔维姆后碰撞带（123~105 Ma）；（2）与伸展作用相关的查翁岩浆省（109~100 Ma）；（3）与俯冲作用相关的鄂霍次克-楚科奇火山岩带（Okhotsk-Chukotka volcanic belt, OCVB）的最早喷发单元（106~100 Ma）。本次观测到的构造-岩浆系统以其产出位置、地球化学与同位素组成特征作为区分标志。岩浆源区的整体富集程度从鄂霍次克-楚科奇火山岩带至提季尔维姆带依次升高，再至查翁岩浆省进一步增强。在提季尔维姆带活动期间，火山喷发位点沿该带走向向西北方向迁移，这一现象可能与业已消亡的南阿纽伊洋岩石圈的穿时拆沉作用有关。就东北亚全域尺度而言，早白垩世控制岩浆作用的构造重组事件，以闭合中的奥伊米亚康洋盆与南阿纽伊洋盆周边主要俯冲带的消亡为标志性特征，后续伴随了可能由岩石圈拆沉及/或伸展作用引发的岩浆活动。在亚洲滨太平洋边缘地带，俯冲相关的火山作用在整个白垩纪期间近乎持续发育。