| 浙西下寒武统大陈岭组地震液化脉微量元素特征研究 |
| 点此下载全文 |
| 引用本文：严兆彬,裴军令,郭福生,胡珺珺,刘礼洁.2019.浙西下寒武统大陈岭组地震液化脉微量元素特征研究[J].地球学报,40(1):236-248. |
| DOI：10.3975/cagsb.2018.112002 |
| 摘要点击次数: 6698 |
| 全文下载次数: 5223 |
|
| 基金项目:国家自然科学基金项目(编号: 41672209) |
|
| 中文摘要:地震液化脉是地震作用引起的软沉积变形的重要构造之一, 前人对脉体形态学和动力学做了大量的研究工作, 但对其成因的微观地球化学行为研究较少。笔者采取开化裴岭脚剖面2期地震事件沉积的 3套地震液化脉层样品21块, 分别对其脉体和含脉体围岩做了微量元素分析。结果显示, 液化脉中Cs、Ba、Th、Zr、Hf、Cr、Rb、Nb等反映陆源性质元素明显高于含脉体围岩, 而Sr、Y、Ni反映海相沉积特征元素则表现为含脉体围岩高于脉体。通过对V、Mo富集度和微量元素特征参数Sr/Ba、Th/U等的综合研究, 发现液化脉体表现为氧化环境, 含脉体围岩为还原环境, 且脉体和围岩均具有淡水作用特点。研究认为, 早寒武世大陈岭期白云质灰岩沉积过程中有蚀源区陆源碎屑物的补入; 在地震突发振动力作用下, 富含水的软沉积层液化泄水, 因化学沉积物和碎屑沉积物性质的差异, 塑性碳酸盐沉积物随水部分流失, 使得单位体积内碳酸盐沉积含量低于围岩, 导致脉体中更富陆源物质; 地震事件沉积层属潮上带, 特别是地震液化泄水后期至成岩期, 含地震液化脉沉积层曾暴露地表, 受后期陆源物的再补给及大气降水淋滤蚀变作用影响, 表现为古气候和古盐度异常, 为浙西大陈岭组浅水沉积提供了地球化学的证据。 |
| 中文关键词:地震液化脉 微量元素 软沉积变形 寒武系 浙江西部 |
| |
| Trace Element Characteristics of Seismic Liquified Veins from the Lower Cambrian Dachenling Formation in Western Zhejiang Province |
|
|
| Abstract:Seismic liquified vein is one of the most important soft sediment deformation structures induced by seismic events. Previous researches have been crried out on morphology and dynamics of the veins, however, few studies on microscopic geochemical behavior of their genesises has been conducted. In this study, trace element analysis of veins and vein-hosting carbonate rocks was done on twenty-one samples from three beds of seismic veins from deposition of two seismic events along the Peilingjiao section. The experiment result shows that the values of Cs, Ba, Th, Zr, Hf, Cr, Rb and Nb of liquified veins are obviously higher than those of vein-hosting carbonate rocks, suggesting terrigenous origin. In contrast, the values of Sr, Y and Ni are more abundant in vein-hosting carbonate rocks, which indicates the features of marine sediments. Based on the research on enrichment of V, Mo and characteristic parameters of trace elements including Sr/Ba and Th/U ratios, liquified veins are interpreted to be of oxidizing environment, whereas vein-hosting carbonate rocks should imply reducing environment. In addition, the veins and vein-hosting carbonate are characterized by freshwater sedimentation. The result shows that there was complement of terrigenous material from erosion source areas during the deposition process of dolomitic limestone in the Early Cambrian. Under the sudden vibration force of earthquakes, the water-rich soft sedimentary rock layers were liquefied with water-escape. Because of properties differences between chemical and clastic sediments, the plastic carbonate sediments were partially lost with water, leading to the lower content of the carbonate sediments per unit area than the surrounding carbonate rocks and more terrigenous material in veins. Soft sedimentary beds are of supratidal sediments, which were exposed during the period from the late stage of liquefaction draining to diagenesis. The late terrigenous resupply and atmospheric precipitation leaching alteration effects led to abnormal paleoclimate and salinity of the soft sediments, which provided geochemical evidence for shallow water sedimentation of Dachenling Formation in western Zhejiang Province. |
| keywords:seismic liquified vein trace element soft-sediment deformation Cambrian western Zhejiang Province |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|
