刘欢, 李怀坤, 张健, 田辉, 常青松. 2023: 豫西地区汝阳群碎屑岩地球化学特征及其对沉积环境与构造背景的指示. 地质通报, 42(12): 2142-2155. DOI: 10.12097/j.issn.1671-2552.2023.12.010
    引用本文: 刘欢, 李怀坤, 张健, 田辉, 常青松. 2023: 豫西地区汝阳群碎屑岩地球化学特征及其对沉积环境与构造背景的指示. 地质通报, 42(12): 2142-2155. DOI: 10.12097/j.issn.1671-2552.2023.12.010
    LIU Huan, LI Huaikun, ZHANG Jian, TIAN Hui, CHANG Qingsong. 2023: Geochemical characteristics of clastic rocks from Ruyang Group, western He'nan Province, and its indication to depositional environment and tectonic setting. Geological Bulletin of China, 42(12): 2142-2155. DOI: 10.12097/j.issn.1671-2552.2023.12.010
    Citation: LIU Huan, LI Huaikun, ZHANG Jian, TIAN Hui, CHANG Qingsong. 2023: Geochemical characteristics of clastic rocks from Ruyang Group, western He'nan Province, and its indication to depositional environment and tectonic setting. Geological Bulletin of China, 42(12): 2142-2155. DOI: 10.12097/j.issn.1671-2552.2023.12.010

    豫西地区汝阳群碎屑岩地球化学特征及其对沉积环境与构造背景的指示

    Geochemical characteristics of clastic rocks from Ruyang Group, western He'nan Province, and its indication to depositional environment and tectonic setting

    • 摘要: 华北克拉通南缘豫西地区中元古代汝阳群备受关注,尤其在年代学和沉积学方面研究成果丰硕。从沉积地球化学角度入手,探讨汝阳群碎屑岩的物源属性和大地构造背景,恢复古沉积环境,为描述华北克拉通南缘中—新元古代地层的精细结构提供依据。主量、微量元素分析结果显示:①较白草坪组而言,云梦山组样品SiO2含量更高,Fe2O3、MgO、CaO和K2O含量较低,亲镁铁的过渡族元素和高场强元素明显亏损,暗示云梦山组样品具有较高的成分成熟度,而白草坪组成分成熟度有所降低。所有样品均表现为稀土元素右倾的配分模式,轻稀土元素富集,重稀土元素相对平坦,轻、重稀土元素分馏明显,中等程度的负Eu异常(δEu=0.60~0.85),弱负Ce异常(δCe=0.80~0.96),与大陆上地壳标准化曲线近于平行。②利用微量元素含量及比值(V/Cr、Ni/Co、U/ThSr/Ba、Th/U,Sr/Cu、Rb/Sr值及Ce、Eu异常)进行古环境重建,推测云梦山组和白草坪组为氧化条件下的陆相滨海—浅海相沉积环境,古气候经历了干旱—湿润—干旱的变化。③据主量、微量元素构造环境判别图解及稀土元素含量推断,云梦山组和白草坪组碎屑岩来自物源区稳定的被动大陆边缘,其中部分点的岛弧属性则由物源原岩继承而来,受原岩沉积时的构造环境影响。结合沉积和年代地层等成果,这套被动大陆边缘性质的滨海—浅海相碎屑沉积,可作为华北克拉通1.8~1.6 Ga的裂解记录,也是哥伦比亚超大陆早期裂解的地质响应。

       

      Abstract: The Mesoproterzoic Ruyang Group along the south margin of North China Craton(NCC) have been attracted much attention, resulting in an increasing number of achievements about chronology and sedimentology.In this paper, we trace the provenance of the clastic sedimentary rock of the Ruyang Group by geochemistry perspective, and reconstruct the palaeogeography and tectonic setting, which provide valuable details to describe the structure of the Meso-Neoproterozoic strata in the southern margin of NCC.The analytical results of major and trace elements contents of the Yunmengshan and Baicaoping Formations suggest that: ①Compared with Baicaoping Formation, Yunmengshan Formation shows higher SiO2 contents, lower Fe2O3, MgO, CaO and K2O contents, the obvious depletion of transition trace elements and high field strength elements, indicating relatively higher maturity.All samples show steep descending REE patterns with enriched LREE, flat HREE and obvious fractionation of LREE and HREE, moderately negative Eu anomalies(δEu=0.60~0.85) and weakly negative Ce abnormity(δCe=0.80~0.96), which are similar with those of upper continental crust.②According to trace element content and ratios (V/Cr, Ni/Co, U/Th Sr/Ba, Th/U Sr/Cu, Rb/Sr ratios and Ce, Eu anomaly) of the Yunmengshan and Baicaoping Formations, it is inferred that they are littoral and neritic deposit, and oxidation sedimentary environment, while the palaeoclimate experienced aridity-washy-aridity change.③The tectonic setting discrimination diagrams and the abundance of rare earth elements imply that the clastic rocks of the Yunmengshan and Baicaoping formations developed on passive continental margin.The island arc attribute of some points was inherited from the provenance protolith and influenced by the structure setting when the protolith was deposited.Combined with sedimentary and chronostratigraphic results, this series of passive continental margin littoral and neritic clastic deposits can serve as a record of North China Craton breakup from 1.8 to 1.6 Ga and a geological response to the initial breakup of the Columbia supercontinent.

       

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