机构地区:[1]云南大学地球科学学院,昆明650500 [2]河南省地质调查院,郑州450001
出 处:《沉积学报》2025年第2期423-438,共16页Acta Sedimentologica Sinica
基 金:国家重点研发计划(2020YFA0714803);云南省科技厅基础研究专项(202101AU070132);云南大学“双一流”建设项目(C176220100135)。
摘 要:【目的】中元古界熊耳群大古石组是华北克拉通南缘变质结晶基底上最早的沉积岩盖层,研究其沉积环境和沉积过程对反演熊耳群早期沉积环境和构造背景,以及哥伦比亚超大陆裂解过程具有重要意义。然而,目前对大古石组仍缺少系统性研究,在沉积物源和古气候特征方面尤为薄弱。【方法】对豫西北济源小沟背地区熊耳群大古石组进行了主量、微量元素地球化学分析,并探讨了大古石组的物源特征、沉积环境和构造背景。【结果】主量元素分析结果显示,该组细粒碎屑岩离物源区较近,自下而上成分成熟度逐渐降低。其沉积物母岩主要来自长英质岩石和基性岩,自下而上逐渐由花岗岩向长英质火山岩,再到中、基性岩过渡,上段中古老沉积物成分逐渐增加。沉积期间整体为温暖湿润的气候环境,并存在多次气候波动。微量和稀土元素分析结果表明,大古石组下段形成于相对稳定的构造背景,而中、上段形成于较活跃的构造背景。【结论】沉积期间物源、气候及构造环境的变化是地壳活化及与之相关的构造—热作用所致。地幔柱导致地壳上升并逐渐活化,华北克拉通南缘逐渐转入活跃构造背景,大古石组沉积区位于地壳整体抬升的局部凹陷区。熊耳群早期火山活动在局部地区逐渐发育,并给大古石组提供了部分物源。该研究为华北克拉通南缘中元古代早期的构造—沉积演化提供了新证据。[Objective]The Dagushi Formation of the Mesoproterozoic Xiong’er Group is the earliest sedimentary unit overlying the metamorphic crystalline basement at the southern margin of the North China Craton.Studies of the depositional environment and formation processes are highly significant for an understanding of the breakup of the Columbia supercontinent and the sedimentary environment and tectonic setting of the early Xiong’er Group.However,systematic research on the sediment provenance and paleoenvironment of the Dagushi Formation is still lacking.[Methods]The provenance,sedimentary environment and tectonic setting of the Dagushi Formation were studied by analysis of major-and trace elements in the Dagushi Formation of the Xiong’er Group,Xiaogoubei area,Jiyuan,Henan Province[.Results]For the major elements,the results show that the fine-grained clastic rocks of the Dagushi Formation are close to their source,with the compositional maturity gradually decreasing upwards from the bottom.From bottom to top,the sediments are mainly erosional products of a mixture of mafic and felsic rocks,gradually changing from granites to felsic volcanic rocks,then to intermediate rocks.The composition of the ancient sediments in the upper member gradually increases.The Dagushi Formation was deposited in a warm,humid climate,with evidence of several climate fluctuations during that time.Analysis of trace elements and REE show that the lower Dagushi Formation was formed in a relatively stable tectonic setting,and that the middle and upper segments were formed in an active tectonic setting.[Conclusions]Together with the evidence from previous studies,we conclude that the transition of sediment source,climate and tectonic environment during the deposition of the Dagushi Formation of the Xiong’er Group was associated with crust activation and associated tectono-thermal events.A mantle plume uplifted and activated the crust,gradually developing the southern margin of the North China Craton into an active tectonic setting.The depos
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