内蒙古中北部晚古生代基性岩墙群的岩石成因与地球动力学意义

With the guideline of tracing lithospheric extension and deep crust-mantle interactions along convergent plate margins through mafic dyke swarms, this project intends to present a combined study of systematic field investigation and refined in-house petrologic-geochemical analysis on late Paleozoic mafic dyke swarms from the eastern segment of central-north Inner Mongolia. The specific aims are to garner multi-level high-precision petrologic and geochemical data about these dykes, to determine their spatial distribution and temporal sequence, to ascertain dyke petrogenesis and quantitatively assess their magmatic processes, trace regional lithospheric nature and extension-induced deep crust-mantle interactions. By making further systematic comparisons with coeval magmatic-tectonic events from neighboring regions, we strive to establish the spatial-temporal correlation between these dyke swarms and regional intermediate-felsic magmatic province and to fully characterize multiple relationship among mafic dyke genesis, geodynamic processes along convergent plate margins and rapid crustal generation.

本项目以基性岩墙群示踪汇聚板块边缘岩石圈伸展事件与深部壳幔相互作用为宗旨，以内蒙古中北部东段晚古生代基性岩墙群为研究对象，通过野外地质详查与室内精细岩石地球化学研究，获取多层次原始精确的数据资料，查明基性岩墙群的空间分布格局与侵位时间序列；构建基于多元精细岩石地球化学数据约束的基性岩墙群成因模型，定量化评估岩浆演化过程；示踪区域岩石圈地幔属性及其演化，反演伸展条件下的深部壳幔相互作用。综合类比区域相关岩浆构造事件，解析基性岩墙群与区域同期中酸性岩浆岩省的时空关联，阐明基性岩墙群的时空分布和迁移特征；为深入认识基性岩墙群成因、汇聚板块边缘地球动力学过程以及巨量地壳生长之间的耦合联系提供区域研究案例

遵循基性岩墙群示踪汇聚板块边缘岩石圈伸展事件与深部壳幔相互作用的立项视角，聚焦于内蒙古中北部古生代-中生代中基性岩墙群及相关中酸性侵入岩建造，通过野外地质详查并运用精细岩石地球化学实验手段，取得一系列相关岩石的高精度年代学、矿物学、岩石学、元素与同位素地球化学数据；厘定一系列记录古亚洲洋构造域和蒙古-鄂霍茨克构造域演化历程的关键岩浆序列，具体包括：1）见证西太平洋型洋内俯冲体系诞生与成熟的东乌旗乌拉盖早奥陶世辉长岩-闪长岩系列、二连浩特晚寒武世英云闪长岩和中晚奥陶世花岗岩-辉长闪长岩系列；2）见证乌里雅斯太板块边缘俯冲重启和弧后裂解的乌拉盖晚泥盆世花岗闪长岩系列与早石炭世辉绿岩-花岗岩系列；3）见证古亚洲洋板片回卷和洋脊俯冲过程的西乌旗中晚石炭世中基性侵入杂岩/辉长岩-花岗岩系列以及二连浩特地块晚石炭世富闪深成岩-花岗岩系列；4）见证古亚洲洋最终闭合阶段残余洋脊俯冲的辽北开原晚二叠世与晚三叠世中基性侵入岩系列；5）见证蒙古-鄂霍茨克构造域俯冲板片断离到造山后伸展的西乌旗-东乌旗早侏罗世与早白垩世中基性岩墙群。这些岩浆序列不仅重现了汇聚板块边缘从俯冲重启、板片回卷、弧后裂解、洋脊俯冲、弧盆关闭至弧-陆碰撞的完整构造旋回，而且例证了中亚造山带东段俯冲工场中多样性的陆壳生成与再造机制。