Abstract A new integrated stratigraphic, sedimentological and geochemical study was carried out on the Gabal El Urf deposits to clarify their facies architecture, sequence stratigraphic framework, and evolutionary stages. The Gabal El Urf in the Northeastern Desert of Egypt is a well-preserved example of the Neoproterozoic volcano-sedimentary deposits. It comprises inter- and syn-eruptive facies that were generated by diverse depositional processes including debris flows, sheet floods, lacustrine flood flows, and pyroclastic ash falls/density currents. These facies correspond to alluvial fan, aeolian -fluvial, lacustrine, and pyroclastic facies associations that are arranged in four depositional cycles. They reveal variations in accommodation to sediment supply (A/S) ratio. Unconformities and lithofacies assemblages define six stages of volcanism and sedimentation and three unconformity-bounded tectonic sequences that should be allied to tectonic subsidence and basin uplift. These sequences may be subdivided in Low-Accommodation Systems Tracts (LAST) having negative A/S (A/S ratio close to zero) and High-Accommodation Systems Tracts (HAST) with fluctuation in A/S ratio between zero and +1. Sequences 1 and 3 are characterized by clast-supported conglomerates and pyroclastics, overlain by fluvial sand bodies and debris flow deposits, respectively denoting a LAST (positive A/S ratio close to zero). Sequence 2 is marked by pyroclastic ash fall facies at the base, passing to lacustrine deposits that are interlayered with fan-delta conglomerates at the top, defining a HAST (A/S ratio >1). The defined sequences are superimposed by thick fissure-fed ignimbrites which are capped by a co-ignimbritic breccia lag deposits with concentrated pyroclastic fountains. Clastic petrofacies of the El Urf succession indicate an adjacent miscellaneous rock sources involving volcanic, plutonic, and metamorphic terrains during the chief sedimentation processes in rift-related paleotectonic regime. The low to moderate magnitude of the CIA and PIA together with low SiO2/Al2O3 ratio indicate sediment recycling and moderate weathering of the protolith near uplifted basin flank(s) under dominant semi-arid to arid conditions. The development of the El Urf basin is akin to the post-amalgamation Ediacaran volcano-sedimentary basins that are widely distributed in the northern part of the Arabo-Nubian Shield, and is a key tectono-stratigraphic marker for the Cryogenian-Ediacaran shift along a major unconformity surface.

中文翻译：

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新元古代同喷发和间喷发序列的地层和相结构：以埃及东北沙漠 Gabal El Urf 为例

摘要 对Gabal El Urf 矿床进行了新的地层学、沉积学和地球化学综合研究，以阐明其相结构、层序地层框架和演化阶段。埃及东北部沙漠中的 Gabal El Urf 是新元古代火山沉积物的一个保存完好的例子。它包括由不同沉积过程产生的相互和协同喷发相，包括泥石流、片状洪水、湖相洪水流和火山碎屑灰落/密度流。这些相对应于四个沉积旋回的冲积扇、风成-河流、湖相和火山碎屑相组合。它们揭示了住宿与沉积物供应 (A/S) 比率的变化。不整合面和岩相组合定义了火山作用和沉积的六个阶段以及三个与构造沉降和盆地抬升有关的不整合面构造序列。这些序列可以细分为具有负 A/S（A/S 比率接近零）的低便利系统区域 (LAST) 和 A/S 比率在 0 和 +1 之间波动的高便利系统区域 (HAST)。层序 1 和层序 3 以碎屑支撑的砾岩和火山碎屑岩为特征，上覆有河流砂体和碎屑流沉积物，分别表示 LAST（正 A/S 比接近于零）。层序 2 以底部的火山碎屑灰落相为标志，过渡到与顶部扇三角洲砾岩夹层的湖相沉积物，定义了 HAST（A/S 比 >1）。定义的序列由厚的裂隙馈送的火山灰岩叠加，这些火山灰岩被具有集中火山碎屑喷泉的共火灰岩角砾岩沉积物覆盖。El Urf 层序的碎屑岩相表明，在与裂谷相关的古构造体系中的主要沉积过程中，邻近的杂岩源涉及火山、深成岩和变质地形。CIA 和 PIA 的低到中等幅度以及低 SiO2/Al2O3 比率表明在主要的半干旱到干旱条件下，抬升盆地侧翼附近的原岩存在沉积物再循环和适度风化。El Urf 盆地的发展类似于广泛分布在阿拉伯-努比亚地盾北部的埃迪卡拉火山-沉积盆地的合并后的盆地，