Mesozoic tectonic transition of the northeastern North China Craton: Evidence from adakitic rocks in southeastern Jilin Province, China

Chronological and geochemical studies of adakites and adakitic rocks are important in understanding the tectonic evolution and geodynamic processes. We present new zircon U–Pb ages, Hf isotope, and geochemical analyses of adakitic rocks exposed in the Baishan area, southeastern Jilin Province, China. These new ages, together with existing age data, indicate that adakitic magmatism in southeastern Jilin Province can be subdivided into four stages: Early–Middle Triassic (251–235 Ma), Late Triassic (221–219 Ma), late Early–early Late Jurassic (176–156 Ma), and Early Cretaceous (ca. 130 Ma). Early–Middle Triassic adakitic rocks occur in a nearly E–W-trending belt within the northern margin of the northeastern North China Craton, indicating a compressional tectonic setting caused by the scissor-like closure of the Paleo-Asian Ocean from west to east. Late Triassic adakitic rocks occur in the Tonghua area and formed in an extensional setting caused by delamination after subduction and collision between the Yangtze Craton and NCC. Late Early–early Late Jurassic adakitic rocks occur in the Baishan and Kaiyuan areas and originated from partial melting of thickened lower crust in a compressional setting related to subduction of the Paleo-Pacific Plate. Early Cretaceous adakitic rocks occur in the Baishan area and were derived from partial melting of thickened lower crust above the subduction zone and delaminated lower crust, indicating that the subducting Paleo-Pacific Plate retreated to the eastern part of southern Jilin Province during the Early Cretaceous (ca. 130 Ma) and that the tectonic setting of the northeastern part of the NCC changed from compression to extension, starting in the east and progressing westward. In summary, the northeastern part of the NCC has been affected by a series of tectonic events during the Mesozoic, such as the closure of the Paleo-Asian Ocean, the collision between the NCC and YC, and the subduction of the Paleo-Pacific Plate.

埃达克岩（adakites）与埃达克质岩（adakitic rocks）的年代学及地球化学研究，对阐明构造演化与地球动力学过程至关重要。本文报道了中国吉林省东南部白山地区出露的埃达克质岩的全新锆石U-Pb年龄、铪同位素与地球化学分析数据。结合已有年龄资料，本次新获取的年龄结果显示，吉林省东南部的埃达克质岩浆作用可划分为四期：早-中三叠世（251~235 Ma）、晚三叠世（221~219 Ma）、早侏罗世晚期-晚侏罗世早期（176~156 Ma）以及早白垩世（约130 Ma）。早-中三叠世埃达克质岩呈近东西向展布于华北克拉通（North China Craton, NCC）东北部北缘，指示古亚洲洋（Paleo-Asian Ocean）自西向东呈剪刀式闭合所引发的挤压构造环境。晚三叠世埃达克质岩分布于通化地区，形成于扬子克拉通（Yangtze Craton, YC）与华北克拉通俯冲碰撞后拆沉作用导致的伸展构造环境。早侏罗世晚期-晚侏罗世早期埃达克质岩见于白山与开原地区，其起源于与古太平洋板块（Paleo-Pacific Plate）俯冲相关的挤压构造背景下增厚下地壳的部分熔融。早白垩世埃达克质岩分布于白山地区，源自俯冲带之上增厚下地壳与拆沉下地壳的部分熔融，表明早白垩世（约130 Ma）时俯冲的古太平洋板块向吉林南部东部后撤，华北克拉通东北部的构造环境由挤压转为伸展，且该转变自东向西逐步推进。综上，华北克拉通东北部在中生代期间受到一系列构造事件的影响，包括古亚洲洋闭合、华北克拉通与扬子克拉通碰撞，以及古太平洋板块俯冲。