Abstract The Gebel Abu Hamamid area forms the middle part of Shadli Metavolcanics Belt of the South Eastern Desert, which hosts the largest volcanogenic massive sulfide deposits in Egypt. The host-rock succession belongs to the Younger Hamamid Metavolcanics (YHM) group, consisting of mafic and felsic lavas with variable volcaniclastics. Although several studies have attempted to clarify the crustal evolution of the Neoproterozoic basement rocks of the South Eastern Desert, researchers have yet to develop a deep understanding of the petrogenesis, tectonic setting, and ages of these host rocks. In the current study, we newly report whole-rock geochemistry, mineral chemistry, and in-situ U–Pb zircon dating from basaltic to rhyolitic rocks of the YHM group to describe their magmatic evolution. Results indicate that the mafic rocks are characterized by tholeiitic affinity and arc-like geochemical signatures with significantly enriched large-ion lithophile elements and depleted high field strength elements. The parental magma was likely generated by partial melting (~10–15%) of a spinel-lherzolite source mantle that was metasomatized by fluids from a former subduction event, followed by magma ascent under low pressure and low oxygen fugacity conditions. The felsic lavas (~695 Ma) are characterized by subduction-related geochemical characteristics with significant enrichments in Zr, Hf, and Sm. They formed from lithosphere-derived magma enriched by melts from the ancient subducted slab, and later experienced an assimilation-fractional crystallization (AFC) process. The YHM group was formed under extensional geodynamic conditions (back-arc basin setting). The zircon grains display hydrothermal overgrowth at the rims, most likely due to regional metamorphic and hydrothermal changes. This characteristic is likely the effect of hydrothermal fluids associated with the Jurassic-Cretaceous tectonothermal event in the South Eastern Desert.

中文翻译：

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埃及东部沙漠中拥有最大火山成因块状硫化物矿床的新元古代哈马米德变质火山的年代学和地球化学：对岩石成因和构造演化的影响

摘要 Gebel Abu Hamamid 地区位于东南沙漠的 Shadli Metavolcanics 带的中部，该带拥有埃及最大的火山成因块状硫化物矿床。主岩序列属于新哈马米德变质火山 (YHM) 组，由具有可变火山碎屑的镁铁质和长英质熔岩组成。尽管已有多项研究试图阐明东南沙漠新元古代基底岩的地壳演化，但研究人员尚未对这些寄主岩的成因、构造环境和年龄有深入的了解。在目前的研究中，我们新报告了 YHM 组从玄武岩到流纹岩的全岩地球化学、矿物化学和原位 U-Pb 锆石，以描述它们的岩浆演化。结果表明，基性岩具有拉斑亲和性和弧状地球化学特征，大离子亲石元素显着富集，高场强元素贫乏。母体岩浆可能是由尖晶石-二辉石源地幔的部分熔融（~10-15%）产生的，该地幔被前一次俯冲事件的流体交代，然后在低压和低氧逸度条件下岩浆上升。长英质熔岩（~695 Ma）具有与俯冲相关的地球化学特征，其中 Zr、Hf 和 Sm 显着富集。它们由岩石圈衍生的岩浆形成，该岩浆富含古代俯冲板片的熔体，后来经历了同化-分馏结晶 (AFC) 过程。YHM 群是在伸展地球动力学条件下（弧后盆地环境）形成的。锆石颗粒在边缘显示热液过度生长，最有可能是由于区域变质和热液变化。这种特征很可能是与东南沙漠侏罗纪-白垩纪构造热事件相关的热液流体的影响。