Lu Denggang, Liu Jia, Xia Qunke, Luan Zhikang, Zhou Jingjun, Lei Tianting, Wang Lu, Hanski Eero
Research Center for Earth and Planetary Material Sciences, School of Earth Sciences, Zhejiang University, Hangzhou 310058, China.
Key Laboratory of Silicate Cultural Relics Conservation, School of Cultural Heritage and Information Management, Shanghai University, Shanghai 200444, China.
Natl Sci Rev. 2025 Jun 2;12(8):nwaf230. doi: 10.1093/nsr/nwaf230. eCollection 2025 Aug.
Determining the composition, formation mechanisms and stability of the Hadean continental crust is essential for understanding the early geological history of Earth. Detrital zircons, largely from Jack Hills of Western Australia, provide the dominant direct records for the nature of continental crust during the Hadean eon and its formation processes. Although isotope and trace element compositions of these zircons are extensively determined, the major and trace element compositions of their host rocks and corresponding parental magmas remain largely debated, making the nature and evolution of the early Earth's crust ambiguous. Here, based on the comprehensive datasets for global magmatic zircons and their host rocks, we have developed machine learning models to reconstruct multiple major and trace element concentrations of the parental magmas from which Jack Hills zircons grew. The results show that the Hadean continental crust had SiO₂ contents ranging from 58 to 78 wt% with K₂O/Na₂O and Sr/Y ratios in the range of 0.1-1.2, and 1-103, respectively. It was generally not andesitic in lithochemistry, but rather felsic and dominated by low- to medium-pressure tonalite-trondhjemite-granodiorite (TTG) and potassic granites. These rocks would be derived from partial melting of low- and high-potassium mafic proto-crust, respectively, with the latter also incorporating contributions from tonalite. The lack of high-pressure TTGs does not preclude their formation at convergent plate margins, but suggests that the Hadean felsic crust would originate from the collisionally thickened rather than the deeply subducted oceanic crust. Therefore, the formation of continental crust on the Hadean Earth can be explained by the operation of convergent tectonics, outlining a petrogenetic model for Archean TTG rocks.
确定冥古宙大陆地壳的组成、形成机制和稳定性对于理解地球早期地质历史至关重要。碎屑锆石主要来自西澳大利亚的杰克山，为冥古宙时期大陆地壳的性质及其形成过程提供了主要的直接记录。尽管这些锆石的同位素和微量元素组成已得到广泛测定，但其寄主岩石和相应母岩浆的主量和微量元素组成仍存在很大争议，这使得早期地球地壳的性质和演化变得模糊不清。在此，基于全球岩浆锆石及其寄主岩石的综合数据集，我们开发了机器学习模型，以重建杰克山锆石生长的母岩浆的多种主量和微量元素浓度。结果表明，冥古宙大陆地壳的SiO₂含量范围为58至78 wt%，K₂O/Na₂O和Sr/Y比值分别在0.1 - 1.2和1 - 103之间。其岩石化学性质一般不是安山质的，而是长英质的，以低压至中压的英云闪长岩-奥长花岗岩-花岗闪长岩（TTG）和钾质花岗岩为主。这些岩石分别源自低钾和高钾镁铁质原始地壳的部分熔融，后者还包含英云闪长岩的贡献。缺乏高压TTG并不排除它们在会聚板块边缘形成的可能性，但表明冥古宙长英质地壳将起源于碰撞增厚的而非深度俯冲的洋壳。因此，冥古宙地球大陆地壳的形成可以通过会聚构造作用来解释，勾勒出了太古宙TTG岩石的岩石成因模型。
