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首页> 外文期刊>Arabian Journal for Science and Engineering >POSSIBLE ORIGIN OF THE OPHIOLITES OF EASTERN DESERT, EGYPT, FROM GEOCHEMICAL PERSPECTIVES
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POSSIBLE ORIGIN OF THE OPHIOLITES OF EASTERN DESERT, EGYPT, FROM GEOCHEMICAL PERSPECTIVES

机译：从地球化学的角度看，埃及东部沙漠蛇麻岩的可能起源

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摘要

Recent recognition of a number of ophiolites from the Precambrian basement of the central and southern subregions of the Eastern Desert region of Egypt is documented along with their field and geochemical perspectives. A synthesis is presented based on previously available chemical data on major and trace elements of 475 carefully filtered ophiolitic rock samples and their mineral constituents. The data has been partitioned into that for five units of rock-types spanning 93 samples of ultramafics (UM), 128 of metagabbros (MG), 20 of sheeted dykes (SHD), 206 of metavolcanics (MV), and 28 of metasediments (MS). Similarities in the values for lavas and sheeted dykes appear to be a manifestation of their cogenetic origin. Amongst the Eastern Desert ophiolites (EDO), those belonging to the harzburgite subtype are prevalent, although a few Iherzolite subtype ophiolites occur in the Central Eastern Desert (CED) subregion. Differentiation of the parental magmas led to the formation of volcanics at their latest stages, and resulted in the igneous rock series of subalkaline, mostly tholeiitic character. Distinctions between the ophiolites from CED and Southern Eastern Desert (SED) subregions are emphasized. Whole-rock geochemistry inclusive of REE variations indicate complex tectonic settings. Gerf ophiolite of SED revealed affinities to normal MORB type genesis. Protoliths of greywackes around ophiolites indicate the existence of both oceanic and continental island arcs. Mineral chemistry of clinopyroxenes, amphiboles, plagioclase feldspars, chromites, serpentines, and iron oxides are also used in comparisons with other known ophiolites of different ages. In many aspects, such as pyroxene chemistry, the implied geotectonic settings of the Eastern Desert ophiolites belong to a wider span of settings than the previously expressed back-arc basinal origin of all these ophiolites.
机译：最近对埃及东部沙漠地区中部和南部次区域的前寒武纪基底中的蛇绿岩的认识以及它们的油田和地球化学观点都得到了记录。根据先前获得的有关475种经过仔细过滤的脂岩岩石样品及其矿物成分的主要和微量元素的化学数据，提出了一种合成方法。数据已被划分为五个岩石类型的数据，分别覆盖93个超基性样品（UM），128个变质岩（MG），20个薄片状堤坝（SHD），206个变火山岩（MV）和28个变质沉积物（多发性硬化症）。熔岩和薄片状堤坝的价值相似似乎是它们共同成因的体现。在东部沙漠蛇绿岩（EDO）中，属于harzburgite亚型的蛇绿岩很普遍，尽管在东部东部中部（CED）的次区域中也存在一些Iherzolite亚蛇绿岩。母岩浆的分化导致火山在最晚阶段形成，并导致了碱性以下的火成岩系列，大部分为韧性特征。强调了CED和南部东部沙漠（SED）子区域的蛇绿岩的区别。包括稀土元素变化在内的整个岩石地球化学表明了复杂的构造环境。 SED的Gerf蛇绿岩显示出与正常MORB类型成因的亲和力。蛇绿岩周围的灰泥原石表明存在海洋弧和大陆弧。与其他已知的不同年龄的蛇绿岩相比，还使用了斜辉石，斜闪石，斜长石长石，亚铬酸盐，蛇纹石和氧化铁的矿物化学。在许多方面，例如辉石化学，东部沙漠蛇绿岩的隐含大地构造环境比所有这些蛇绿岩的先前弧后盆地盆地起源所处的环境范围更广。

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