西北太平洋从活动陆缘到沟-弧-盆体系转换的时间与机制：晚白垩世-古近纪岩浆作用记录

Northwestern (NW) Pacific Ocean is a natural laboratory to study interaction processes between an oceanic plate and a continental plate. This project takes the transformation timing and mechanism as well as its deep processes from active continental margin to trench-arc-basin system in NW Pacific Ocean as a key scientific problem, and systematically studies the geochronology and geochemistry of the Late Cretaceous-Paleogene igneous rocks in continental margin of northeastern Asia (including eastern part of NE China, the Sikhote-Alin-Sakhalin Orogenic Belt in Russian Far East, and Hokkaido Island). The aim of this project is: 1) to determine the episodes and rock association of the Late Cretaceous-Paleogene magmatisms, and further to constrain subduction processes of the (Paleo-) Pacific plate by using spatial variation of igneous rock associations; 2) to constrain changing time and mechanism of subduction nature of the (Paleo-) Pacific plate by using variations of igneous rock associations through time; and 3) finally to determine the transformation timing and mechanism as well as its deep processes from active continental margin to trench-arc-basin system in NW Pacific Ocean by synthesizing sedimentary formations, paleomagnetic data as well as changes of subduction direction of the (Paleo-) Pacific plate. This project is of important implications not only for ascertaining subduction history of the (Paleo-) Pacific plate beneath the Eurasia, but also for revealing deep geodynamic background of formation of late Mesozoic-Cenozoic mineral resources and environment variations in NE Asian continental margin.

西北太平洋是研究大洋板块与大陆板块相互作用过程的一个天然实验室。本项目围绕西北太平洋从活动陆缘到沟-弧-盆体系转换的时间与机制及其深部作用过程这一关键科学问题，拟通过对东北亚陆缘（包括我国东北东部、锡霍特阿林-萨哈林造山带和日本北海道）晚白垩世-古近纪火成岩年代学与地球化学的系统研究，查明东北亚陆缘晚白垩世-古近纪岩浆作用的期次与岩石组合，利用火成岩组合的空间变异，查明（古）太平洋板块的俯冲过程；通过晚白垩世-古近纪不同期次火成岩组合及其地球化学属性随时间的变异，限定大洋板块俯冲性质变化的时间与机制；综合同期沉积建造与古地磁等研究成果以及太平洋板块俯冲方向的变化，最终查明西北太平洋从活动陆缘到沟-弧-盆体系转换的时间与机制及其深部作用过程。该项研究不仅对重塑（古）太平洋板块在欧亚大陆下的俯冲历史, 而且对揭示东北亚陆缘晚中生代-新生代资源形成与环境变化的深部动力学背景均具有重要意义。

本项目围绕西北太平洋从活动陆缘到沟-弧-盆体系转换的时间与机制及其深部作用过程这一关键科学问题，对东北亚陆缘（包括我国东北东部、锡霍特阿林-萨哈林造山带和日本北海道）晚白垩世-古近纪火成岩进行了年代学与地球化学的系统研究，得出如下主要认识：1）查明了东北亚陆缘晚白垩世-古近纪岩浆作用的期次与岩石组合，利用火成岩组合的空间变异，并结合陆缘增生杂岩的研究，查明了中生代古太平洋板块的俯冲演化历史；2）通过晚白垩世-古近纪不同期次火成岩组合及其地球化学属性的时空变异，查明了西北太平洋从活动陆缘到沟-弧-盆体系转换的时间与机制；3）利用早新生代埃达克岩的时空分布及其地球化学属性变异，初步确定了古太平洋和太平洋之间洋脊俯冲的时间与方式。