| 黔中隆起北缘五峰-龙马溪组页岩元素地球化学特征及其地质意义 |
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| 引用本文： | 李琪琪,蓝宝锋,李刚权,徐尚,刘婷,苟启洋,王雨轩.黔中隆起北缘五峰-龙马溪组页岩元素地球化学特征及其地质意义[J].地球科学,2021,46(9):3172-3188. |
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| 作者姓名： | 李琪琪 蓝宝锋 李刚权 徐尚 刘婷 苟启洋 王雨轩 |
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| 作者单位： | 1.中国地质大学构造与油气资源教育部重点实验室, 湖北武汉 430074 |
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| 基金项目： | 国家自然科学基金重大项目41690134国家自然科学基金青年基金41702155国家科技重大专项2016ZX05034002-003 |
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| 摘 要： | 为探讨黔中隆起北缘五峰—龙马溪组富有机质页岩的沉积环境和物源区背景，对区内两口井的样品进行了有机碳含量、微量元素和稀土元素地球化学测试和分析.结果表明，研究区五峰—龙马溪组页岩在沉积时以贫氧—厌氧环境为主，富氧环境也偶尔存在，且龙马溪组沉积水体还原程度比五峰组高.LaN/YbN值的变化反映沉积速率为:龙马溪组下部 < 五峰组 < 观音桥段，表明五峰—龙马溪组页岩沉积时存在沉积速率先变快后变缓的过程.Mo/TOC值显示五峰组页岩沉积时盆地滞留程度较强，进入志留纪相对减弱，盆地滞留程度对有机质富集的正向影响可能不大，海平面升降造成的氧化还原条件以及生产力条件的变化或许控制了有机质的富集.微量和稀土元素组合及比值特征，反映研究区五峰—龙马溪组沉积时的原始物质来自上地壳，五峰组沉积时存在混合物源，而龙马溪组沉积时物源相对单一，总体上源岩以长英质（花岗岩）为主.源区构造背景以主动大陆边缘为主，受到一定热液活动的影响，同时也表现出一定的大陆岛弧构造背景的特征.
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| 关 键 词： | 微量元素 稀土元素 古环境 物源 五峰—龙马溪组 地球化学 |
| 收稿时间： | 2020-06-27 |
Element Geochemical Characteristics and Their Geological Significance of Wufeng-Longmaxi Formation Shales in North Margin of the Central Guizhou Uplift |
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| Li Qiqi,Lan Baofeng,Li Gangquan,Xu Shang,Liu Ting,Gou Qiyang,Wang Yuxuan.Element Geochemical Characteristics and Their Geological Significance of Wufeng-Longmaxi Formation Shales in North Margin of the Central Guizhou Uplift[J].Earth Science-Journal of China University of Geosciences,2021,46(9):3172-3188. |
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| Authors: | Li Qiqi Lan Baofeng Li Gangquan Xu Shang Liu Ting Gou Qiyang Wang Yuxuan |
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| Abstract: | In order to discuss depositional setting and its tectonic background of the Wufeng-Longmaxi Formation organic-rich shales in the northern margin of the central Guizhou uplift, the TOC content, trace elements and rare earth elements of the samples from two wells in the area were tested. The results show that the Wufeng-Longmaxi Formation shales in the study area was mainly deposited in poor oxygen-anaerobic environment, and the oxygen-rich environment also exists occasionally, and the reduction degree of sedimentary water in Longmaxi Formation is higher than that in Wufeng Formation. The sedimentation rate reflected by the changes of LaN/YbN value is as follows: the lower part of the Longmaxi Formation < the Wufeng Formation < the Guanyinqiao section, which reflects the process that the sedimentation rate of the Wufeng-Longmaxi Formation shale becomes faster at first and then slows down. The Mo/TOC values show that the water mass restriction degree of the basin is strong during the sedimentation of the Wufeng Formation shale, and relatively weakened in the Silurian, the restriction degree has little positive effect on the enrichment of organic matter, while the changes of redox conditions and productivity factors caused by sea level rise and fall control the enrichment of organic matter. The characteristics of the trace elements and rare earth elements reflect that the provenance of the Wufeng-Longmaxi Formation shales comes from the upper crust, there is mixed provenance in Wufeng Formation, and the provenance of Longmaxi Formation is relatively simple, generally speaking, the source rocks are mainly feldspathic-quartz (granite). The tectonic setting was mainly passive continental margin, due to the effect of certain hydrothermal input, it also exhibits certain characteristics of continental island arc tectonic background. |
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