| 湘中南中奥陶统烟溪组黑色岩系地球化学特征及成因分析 |
| 投稿时间：2024-07-12 修订日期：2024-09-16 |
| 关键词:black rock series sedimentary environment origin mechanism Yanxi Formation central-southern Hunan |
| 基金项目:(编号2023JJ30239,2023JJ30231)和湖南省教育厅资助科研项目(编号23B0467)联合资助。收稿日期：2024-07-12；改回日期：2024-XX-XX；网络首发日期：2024-XX-XX第一作者蒋立阳,男,2004年生。勘查技术与工程专业。E-mail：2902547286@qq.com。通信作者余烨,男,1983年生。博士,副教授,主要从事沉积学与页岩气勘探研究。E-mail：yuye1983@163.com。 |
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| 摘要: |
| Geochemical characteristics and petrogenesis analysis of black rock series of Middle Ordovician Yanxi Formation in central-southern Hunan |
| The source, sedimentary environment and genetic mechanism of 20 black rock series samples from 7 profiles which are from Middle Ordovician Yanxi Formation in central-southern Hunan were comprehensively analyzed in order to clarify the genetic model of the differences from north to south based on profile observation, thin section identification, mineral composition and geochemical analysis. The results are as follows. The black rock series of the Yanxi Formation presents microcrystalline and powder crystal structure which are typical for marine siliceous rocks. A large number of graptolite fossils are developed in the northern region of the study area while a large number of radiolarian fossils are developed in the central and southern regions. The distribution pattern of rare earth elements is basically similar to that of the PAAS, characterized by relatively enriched LREE, relatively gentle HREE, positive Ce anomalies, and obvious negative Eu anomalies. The total amount of rare earth elements in the black rock series ranges from 6.06×10-6 to 290.44×10-6, with higher rare earth elements in the northern region and lower rare earth elements in the central and southern regions. The black rock series of the Yanxi Formation which are simultaneously controlled by hydrothermal silicon-rich fluids and the inputs of terrestrial detrital silicon are mainly composed of biogenic silicon. Particularly, hydrothermal silicon-rich fluids have a greater impact on the formation of black rock series in the central and southern regions, while terrestrial detrital silicon inputs have a greater impact on the formation of black rock series in the northern regions. In general, the black rock series of the Yanxi Formation are mainly formed in an oxygen-deficient environment with water retention and the anaerobic reduction degree is slightly higher in the central and southern regions than that in the northern regions. It can be learned that the precipitation of SiO2 in hydrothermal silicon-rich fluids and the development of benthic organisms such as radiolarians promoted the construction of black rock series in the continental margin and deep sea basin of the central and southern regions. At the same time, the terrestrial detrital silicon, fine-grained material, and Planktonic organisms such as graptolites helped the construction of black rock series on the northern continental margin. |
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