摘要
晚二叠世以来受印支造山运动及峨眉山玄武岩喷发事件的影响,上扬子西南缘地区沉积物源及沉积模式发生了重大改变,引发学术界热议。本文以上扬子西南待补地区下三叠统飞仙关组碎屑岩为例,从岩相学、岩石地球化学和碎屑锆石U-Pb年代学等方面对飞仙关组源岩属性、物源、沉积及构造环境进行约束。飞仙关组碎屑岩整体成熟度较低,岩石风化程度中等,源区曾经历过持续的构造抬升剥蚀,并于早三叠世扬子西南缘浅海-滨海相的氧化环境中沉积。其碎屑锆石U-Pb年龄主要集中在257±2.9 Ma,与晚二叠世峨眉山玄武岩主喷发时限一致,岩石地球化学特征表现出与峨眉山高钛玄武岩高度一致,指示飞仙关组主要物源区为近源的峨眉山大火成岩省,源岩主要为板内拉张环境形成的峨眉山高钛玄武岩,并在玄武质岩浆上涌过程中混染了少量扬子陆块古老结晶基底成分。此外,康滇古陆及扬子克拉通也提供了部分物源,主要为Rodinia超大陆汇聚及裂解背景下产生的岩浆岩。年代学证据显示,Rodinia超大陆汇聚及裂解事件在区内具有较好的沉积物源响应,为全球性Rodinia超大陆汇聚及裂解事件的时限约束提供了重要参考依据。
Since the late Permian, influenced by theIndosinian orogeny and the Emeishan basalt eruption, the sediment sources and sediment patterns have changed significantlyin the southwest margin of the upper Yangtze, which stimulated heated discussion in academia. Therefore, in this paper, considering the detrital rocks from the Lower Triassic Feixianguan Formation in the Daibu area of Southwest Upper Yangtzeas an example, constraints on thesource rock properties, material provenance, sedimentation and tectonic environment background usingpetrography, petrogeochemistry, and zircon U-Pb chronology are provided. The maturity of the detrital rocksfrom the Feixianguan Formation is low, and the weathering degree of the rocks ismedium, the source region has experienced continuous tectonic uplift and denudation, and deposition occurredin the oxidative sedimentary environment of the shallow-littoral faciesin the southwestern margin of the Yangtze in the Early Triassic. The U-Pb age of zircon in this paper is mainly concentrated at 257±2.9 Ma, which is consistent with the main eruption time of Emeishan basalt in Late Permian.The petrogeochemical characteristics of the detrital rocks are highly consistent withthe Emeishan high-Ti basalt, indicating that the mainsource area of the Feixianguan Formation is the near-source Emeishan igneous province, the source rock is mainly the Emeishan high-Ti basalt which formed in anintraplate extensional environment, and during the basaltic magma upwellinga small amount of ancient crystalline basement components of the Yangtze block were mixed in. Furthermore, the Kangdian ancient land and the Yangtze craton also provided part of the sediment sources, mainly the magmatic rocks which formed under the background of the Rodinia supercontinentconvergenceand breakup. Chronological evidence shows that the Rodinia supercontinent convergence and breakup events have a good response to the sediment sources in the study area, which provides an important reference basis for the timeconstraints of global Rodinia supercontinent convergence and breakup events.
作者
缪宇
田瑜峰
吴亮
吕晓春
李仕忠
宋文婷
MIAO Yu;TIAN Yufeng;WU Liang;LXiaochun;LI Shizhong;SONG Wenting(Kunming Natural Resources Comprehensive Investigation Center,China Geological Survey,Kunming,Yunnan 650001,China;Applied Geological Research Center,China Geological Survey,Cheng du,Sichuan610036,China;Technology and Business University,Kunming,Yunnan 650001,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2021年第12期3739-3757,共19页
Acta Geologica Sinica
基金
中国地质调查局项目(编号12120115041601)资助的成果。
关键词
上扬子西南缘
飞仙关组
锆石U-PB年龄
物源
构造环境
Southwest margin of upper Yangtze
Feixianguan Formation
detrital zircons
U-Pb age material provenance
tectonic environment
