【作者】 刘恒；

【导师】 刘磊；

【作者基本信息】 中南大学 ， 岩石学、矿物学、矿床学， 2025， 博士

【摘要】 太古宙-元古宙时期壳幔相互作用的性质发生变化,例如地幔温度从热俯冲到冷俯冲的转变、地幔交代程度与规模增加。太古宙晚期-元古宙早期是地球热动力学体制的关键转折期,虽然全球在2.5 Ga后构造活动停滞,但是“静寂期”（2.45-2.20 Ga）的岩浆作用和初生物质添加并未停止,仍然存在大洋一侧或小型闭合洋盆内的俯冲构造过程。这些认识还未从壳幔作用,构造-岩浆演化角度进一步验证。华北克拉通南缘广泛分布中太古代晚期,新太古代晚期,古元古代早期的岩浆岩,类型丰富,在岩石成因和构造环境方面又有所差异,因此是开展早期陆壳演化研究和对比的理想场所。但目前对这些岩浆作用是“幕式”发生,还是小频率持续脉冲发生以及它们的属性、时空分布和成因还缺乏了解。本论文选择华北克拉通南缘登封和熊耳山地区为研究对象,综合利用全岩和单矿物主微量元素,以及磷灰石Sr-Nd、锆石Hf-O同位素体系,通过详细的岩石学、元素-同位素地球化学和年代学研究,深入探讨华北克拉通南缘多期岩浆作用,及对早期陆壳构造演化的指示。本文取得了以下认识:（1）首次发现熊耳山地区中太古代2.83 Ga英云闪长岩-奥长花岗岩-花岗闪长岩岩石组合（TTG）性质岩浆作用。通过熊耳山地区锆石Hf-O和全岩Nd同位素数据显示其源于新生地壳并具有地幔来源特征,元素地球化学特征表明其形成于弧岩浆环境,结合区域同期鲁山地区,小秦岭地区TTG岩石的特征,以及同期全球主要克拉通洋壳初始俯冲作用的中太古代岩石,为进一步证实全球俯冲构造体制在约2.8 Ga开始提供了可靠的证据;（2）针对登封地区的2.55-2.48 Ga基性岩与2.63-2.50 Ga的长英质岩石,开展系统性岩石类型研究。基于登封地区基性岩的地球化学特征,揭示新太古代晚期区域内基性岩具有弧玄武岩和弧后盆地玄武岩的构造演化特征。长英质岩浆作用表明TTG片麻岩源于俯冲洋壳部分熔融,变闪长岩起源于受俯冲流体交代的亏损地幔,而富钾花岗质岩石由英云闪长岩与沉积岩混合熔融形成。活动大陆边缘的构造背景对太古宙地壳成熟及花岗岩类岩石多样化起到了关键作用;（3）基于熊耳山地区广泛发育新太古代晚期-古元古代早期岩浆事件,本文新发现熊耳山西部地区存在构造-岩浆的“静寂期”（Tectono-Magmatic Lull,简称TML）前期2.51-2.43 Ga的奥长花岗岩和2.7 Ga捕获锆石,结合熊耳山地区TML期间发生的岩浆活动,解析了新太古代晚期-古元古代早期地壳的形成演化规律,明确其形成于汇聚板块边界的高角度俯冲构造背景,且可能受到地幔物质上涌引起的伸展作用的叠加影响。本文论证了大氧化事件对TML期间前后三类TTG岩石的氧同位素和氧逸度变化有一个先升高再降低的过程。本文对熊耳山地区2.2-2.1 Ga含低δ¹⁸O同位素的赞岐岩类岩石、镁铁质基性岩和壳源花岗岩开展了多种元素地球化学指标及Sr-Nd,Hf-O同位素特征研究,表明这些岩浆岩来自大陆弧系统,并与俯冲作用有关,为TML后的岩浆演化提供了新认识。综上所述,本研究通过对华北克拉通南缘登封地区,熊耳山地区各类岩浆的岩石成因及构造演化研究,以中太古代晚期,TML期间及其前后岩浆岩所记录的深部动力学过程为切入点,解析其成因及内在演化联系,揭示了它们的构造-热事件期次和地球化学性质,揭示了地质构造、岩浆活动与壳幔作用之间的复杂关系,探究了它们所反映的地球动力学背景,阐明了太古宙-元古宙壳幔作用机制的变化,为研究太古宙-元古宙壳幔动力学体制提供了新的制约。图82幅,表14个,参考文献335篇更多还原

【Abstract】 During the Archean to Proterozoic eons,the nature of crust–mantle interactions underwent significant changes,such as the transition from hot to cold subduction and the increasing scale and intensity of mantle metasomatism.The Late Archean to Early Proterozoic represents a critical turning point in Earth’s thermodynamic regime.Although global tectonic activity appeared to stagnate after 2.5 Ga,magmatic activity and the addition of juvenile material during the Tectono-Magmatic Lull（TML）（2.45–2.20 Ga）did not cease.Subduction-related tectonic processes still occurred on the oceanic side or within small,closed ocean basins.However,these processes have not yet been fully verified from the perspectives of crust–mantle interactions and tectono-magmatic evolution.The southern margin of the North China Craton（NCC）hosts widespread magmatic rocks from the Late Mesoarchean,Late Neoarchean,and Early Paleoproterozoic.These rocks display a diverse range of types and differences in petrogenesis and tectonic setting,making this region an ideal site for studying and comparing early continental crustal evolution.Yet,it remains unclear whether these magmatic events occurred in episodic"pulses"or as low-frequency continuous intrusions,and their properties,spatiotemporal distribution,and origins are still not well understood.This study focuses on the Dengfeng and Xiong’ershan areas along the southern margin of the NCC.By integrating whole-rock and single-mineral major and trace element analyses,along with apatite Sr–Nd and zircon Hf–O isotopic systems,this study conducts detailed petrological,geochemical,and geochronological research to investigate multiple phases of magmatism in the region.The key findings are as follows:（1）For the first time,a tonalite–trondhjemite–granodiorite（TTG）suite composed of trondhjemite,alkali feldspar granite,and granodiorite dated to 2.83 Ga was discovered in the Xiong’ershan area.Zircon Hf–O isotopes and whole-rock Nd isotopes indicate that these rocks originated from juvenile crust with a mantle signature.Their geochemical characteristics suggest a magmatic arc environment.When considered alongside coeval TTG rocks in the Lushan and Xiaoqinling areas,as well as other Archean rocks formed during initial oceanic crust subduction in major global cratons,these findings provide evidence supporting the onset of global subduction tectonics around 2.8 Ga.（2）A systematic study was conducted on mafic rocks（2.55–2.48 Ga）and felsic rocks（2.63–2.50 Ga）in the Dengfeng area.The geochemical features of the mafic rocks reveal an evolution from arc basalt to back-arc basin basalt during the Late Neoarchean.The TTG gneisses are shown to be derived from partial melting of subducted oceanic crust,the metamorphosed diorites from depleted mantle metasomatized by subduction fluids,and the K-rich granitic rocks from the hybrid melting of trondhjemite and sedimentary rocks.The tectonic setting of an active continental margin played a critical role in crustal maturation and granite diversification during the Archean.（3）Based on the widespread Late Neoarchean to Early Paleoproterozoic magmatic events in the Xiong’ershan area,new findings include a 2.51–2.43 Ga crystallization age for alkali feldspar granite in the western part of the region and the presence of inherited 2.7 Ga zircons.Combined with other magmatic events during the TML period,this study reveals the evolutionary processes of the crust during this interval.It identifies a high-angle subduction setting along a convergent plate boundary and suggests the superimposed effects of mantle upwelling and extension.The study also demonstrates that the Great Oxidation Event was associated with changes in oxygen isotopes and oxygen fugacity in three types of TTG rocks before and after the TML period—initially increasing and then decreasing.Based on low-δ¹⁸O isotopes in sanukitoid rocks,mafic cumulates,and granites（2.2–2.1 Ga）in the Xiong’ershan area,along with geochemical and isotopic evidence（Sr–Nd,Hf–O）,the results indicate these magmas were derived from a continental arc system and related to subduction processes,offering new insights into post-TML magmatic evolution.In conclusion,this study investigates the petrogenesis and tectonic evolution of various magmatic rocks in the Dengfeng and Xiong’ershan areas on the southern margin of the NCC.By focusing on deep geodynamic processes recorded in Late Mesoarchean and TML-period magmatism,this research deciphers the genetic and evolutionary relationships of these rocks,revealing their tectono-thermal sequences and geochemical properties.It highlights the complex interactions among tectonic structures,magmatic activity,and crust–mantle processes,explores the geodynamic context they reflect,and clarifies the changing mechanisms of crust–mantle interactions from the Archean to Proterozoic.This study provides new constraints on the geodynamic regime of the Archean–Proterozoic transition.更多还原