辽东-胶北地区~2.9-2.7Ga花岗岩类岩浆作用多样化与壳幔作用研究

Recent studies reveal that fundamental changes of early continental crust formation and evolution occurred globally during the Meso- to Neoarchean period. Particularly, the diversification of granitoid magmatism is one of the major characteristics accompanying the compositional change of continental crust and transition of geodynamic regimes during this period. In this proposal, systematic whole-rock major and trace elements and Sm-Nd-Mg isotopes, together with zircon U-Pb-Lu-Hf-O isotopes and trace elements, will be analyzed for the ~2.9-2.7 Ga dioritic-TTG gneisses and potassium-rich granitoids in the Eastern Liaoning and Jiaobei Provinces, North China Craton. These data will be integrated to (1) investigate the spatial and temporal distribution, source characteristics, petrogenesis, and thermal dynamic processes of different granitoid rock associations; and (2) quantitatively analyze the crust-mantle interaction processes, including juvenile crustal growth, and reworking and recycling of ancient crustal materials. Combined with regional research progresses, the ~2.9-2.7 Ga crust-mantle evolution history and their major features will be summarized. Accordingly, we plan to discuss the specific mechanism and crust-mantle geodynamic processes responsible for the Meso- to Neoarchean diversification of granitoid magmatism, and explore the transformation mechanism of global Meso- to Neoarchean geodynamics and their implications for the formation and evolution of early continental crust.

近年来研究表明中-新太古代时期是早期大陆地壳形成和演化的重要转折阶段，花岗岩类岩浆作用的多样化是这一时期陆壳性质和热构造体制转变的标志性记录。本项目拟选择辽东-胶北地区~2.9-2.7Ga闪长质-TTG片麻岩和富钾质花岗岩两个系列花岗岩类岩石为研究对象，通过全岩主微量元素和Sm-Nd-Mg同位素、锆石U-Pb-Lu-Hf-O同位素和微量元素研究，解剖不同系列花岗岩类岩石组合的时空分布、源区性质、成因机制和相关的热-动力学过程，定量分析它们记录的壳幔作用过程，包括初生地壳生长、古老陆壳活化和再循环。结合区域相关研究进展，总结~2.9-2.7Ga壳幔作用演化历史和典型特征，探讨中-新太古代花岗岩类岩浆作用多样化产生机制和壳幔动力学过程，深入探索中-新太古代热构造体制转折机制及其在早期大陆地壳形成演化中的意义。

开展太古宙晚期花岗岩类岩浆作用多样化的起源机制研究是探讨早期地球热动力学体制转折机制及其标志性特征的关键。本项目对辽东-胶北地区产出的不同期次和类型~2.9-2.7 Ga花岗岩类岩石组合开展了系统的地质学、岩石学、地球化学（全岩主微量和Mg同位素、锆石U-Pb-Lu-Hf-O同位素）以及壳幔作用综合对比研究，取得主要成果如下：（a）构建了中太古代初始热俯冲相关地质地球化学标志（高镁闪长质和高压-高δ18O TTG片麻岩组合），相关热俯冲作用启动事件在全球陆续发生于~3.6-3.5 Ga和<~3.0 Ga时期；（b）在辽东地区厘定出~2.78和~2.68 Ga两期TTG片麻岩，建立了与后撤型增生造山相关峰期地壳生长事件的鉴别标志；（c）在胶北地区识别出系列~2.7 Ga富钾花岗岩类岩石，提出岛弧体系的构建及其风化剥蚀和再循环过程是诱发太古宙花岗岩类岩浆作用多样化的重要机制；（d）辽东-胶北地区记录了~3.0-2.9 Ga、~2.7 Ga和~2.5 Ga三期富钾花岗岩类岩浆作用事件，其岩石类型和地球化学特征的多样化程度逐渐加强，反映壳幔作用程度逐渐增加，可能与热俯冲构造体制的启动及逐渐演化成熟过程有关。依托本项目，在Precambrian Research、Gondwana Research和Lithos等国际主流SCI期刊上发表论文4篇，相关成果对深入认识太古宙花岗岩类岩浆作用多样化的起源机制、地球早期热动力学体制演化及标志性特征等具重要意义。