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Geology and evolutionary stages of the Late Precambrian Hammamat sediments at Gebel Um Tawat, North Eastern Desert, Egypt
Arabian Journal of Geosciences Pub Date : 2020-06-04 , DOI: 10.1007/s12517-020-05323-9
Asmaa Adel Khalifa , Hossam Anwer Khamis , Mohamed Mohamed El-Sayed , Mahmoud Hany Shalaby

The Um Tawat Late Precambrian immature molasse-type Hammamat sedimentary rocks, located in the Northern part of the Eastern Desert of Egypt, were deposited at the late stage evolution of the Pan-African Orogeny. The Um Tawat molasse sediments are mainly derived from Dokhan volcanics and rest unconformably on these volcanics. They are intruded by the younger granites of Sala’at El-Belih granites and Gebel Gattar batholith. Hammamat sediments consist of repeated cycles of conglomerates, sandstones, siltstones, and minor mudstones deposited in an inter-mountainous basin by braided stream and alluvial fan regime constituting a stratigraphic section of about 500 m thick. Petrographically, the conglomerates are of polymictic type. Sandstone could be termed arkosic greywacke and shows ripple marks and in some places cross bedding. Siltstone is characterized by clear lamination and graded bedding. Mudstone is characterized by very fine grains of silt and clay size particles. The evolutionary stages of the study area is divided into five stages: (1) compressional regime resulted in the formation of the metavolcanics and metagabbro-diorite complex; (2) tension and relaxation crustal regime and uplift of the old basement forming G. Dokhan; (3) relaxation period, weathering, and erosion processes of the Dokhan volcanics formed the Hammamat molasse-type sediments; (4) tensional regime or weak rift-like processes led to the eruption of the younger granites and (5) regional compressional deformation subjected to the Hammamat sediments. This phase form G. Um Tawat and forming one regional open anticline fold whose fold axis is trending N47°E–S47°W and plunges 5° toward SW.



中文翻译:

埃及东北沙漠,Gebel Um Tawat的晚前寒武纪哈马马特沉积物的地质和演化阶段

位于埃及东部沙漠北部的Um Tawat前寒武纪晚期不成熟蜜糖型哈马马特沉积岩沉积于泛非造山运动的晚期。Um Tawat糖蜜的沉积物主要来自Dokhan火山岩,并不一致地分布在这些火山岩上。它们被年轻的Sala'at El-Belih花岗岩和Gebel Gattar岩床侵入。哈马马特沉积物由砾岩,砂岩,粉砂岩和次要泥岩的反复循环组成,这些堆积物通过辫状流和冲积扇状沉积在山间盆地中,构成约500 m厚的地层。岩相学上,该团块是多聚型的。砂岩可以被称为arkosic greywacke,具有波纹痕迹,在某些地方还可以横穿被褥。粉砂岩的特征是清晰的层压和分级的床上用品。泥岩的特征是非常细的淤泥和粘土颗粒。研究区的演化阶段分为五个阶段:(1)压缩机制导致了超火山岩和变辉闪闪-闪长岩复合体的形成;(2)形成地壳G. Dokhan的旧地基底的张力和松弛地壳状态和隆升;(3)Dokhan火山岩的弛豫期,风化作用和侵蚀过程形成了Hammamat糖蜜型沉积物。(4)张力状态或较弱的裂谷状过程导致了年轻花岗岩的喷发和(5)受到哈马马特沉积物的区域压缩变形。该相形成了塔姆瓦特河(G. Um Tawat),并形成了一个区域性开放背斜褶皱,其褶皱轴呈北纬47°至东经47°W,向西南倾斜5°。

更新日期:2020-06-04
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