The Egyptian older and younger granitic rocks emplaced during pre- and post-collision stages of Neoproterozoic Pan-African orogeny, respectively, are widely distributed in the southern Sinai Peninsula, constituting 70% of the basement outcrops. The Wadi El-Akhder, southwestern Sinai, is a mountainous terrain exposing two granitoid suites, namely the Wadi El-Akhder Older Granites (AOG) and the Homra Younger Granites (HYG). The AOG (granodiorites with subordinate tonalite compositions) have geochemical characteristics of medium-K calc-alkaline, metaluminous to mildly peraluminous granitoids formed in an island-arc environment, which are conformable with well-known Egyptian older granitoids rocks, whereas the HYG display calc-alkaline to slightly alkaline nature, peraluminous syeno-, monzogranites and alkali feldspar granites matching well those of the Egyptian younger granites. With respect to the AOG granitoids, the HYG granites contain lower Al₂O₃, FeO^∗, MgO, MnO, CaO, TiO₂, Sr, Ba, and V, but higher Na₂O, K₂O, Nb, Zr, Th, and Rb. The AOG are generally characterized by enrichment in LILE and LREE and depletion in HFSE relative to N-MORB values (e.g., negative Nb and Ta anomalies). The geochemical features of the AOG follow assimilation-fractional crystallization (AFC) trends indicative of extensive crustal contamination of magma derived from a mantle source. The chemical characteristics of the AOG are remarkably similar to those of subduction-related granitoids from the Arabian-Nubian Shield (ANS). The compositional variations from monzogranites through syenogranites to alkali feldspar granite within HYG could not be explained by fractional crystallization solely. Correlating the whole-rock composition of the HYG to melts generated by experimental dehydration melting of meta-sedimentary and magmatic rocks reveals that they appear to be derived by extended melting of psammitic and pelitic metasediments, which is similar to the most of younger granitic suites in the ANS.

中文翻译：

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北阿拉伯-努比亚地盾碰撞前后花岗岩造山过程中地幔源和地壳源相互作用的约束：来自埃及西奈南部 Wadi El-Akhder 花岗岩的案例研究

新元古代泛非造山运动碰撞前后阶段分别形成的埃及较老和较年轻的花岗岩广泛分布于西奈半岛南部，占基底露头的70%。Wadi El-Akhder 位于西奈半岛西南部，是一个山地地形，露出两个花岗岩组，即 Wadi El-Akhder Older Granites (AOG) 和 Homra Younger Granites (HYG)。AOG（含钠闪长石成分的花岗闪长岩）具有在岛弧环境中形成的中 K 钙碱性、金属铝质至轻度过铝质花岗岩的地球化学特征，与众所周知的埃及古花岗岩相吻合，而 HYG 显示钙质-碱性至微碱性，过铝质syeno-，二长花岗岩和碱性长石花岗岩与埃及较年轻的花岗岩相匹配。相对于 AOG 花岗岩，HYG 花岗岩含有较低的 Al₂ O ₃、FeO ^∗、MgO、MnO、CaO、TiO ₂、Sr、Ba 和 V，但 Na ₂ O、K ₂更高O、Nb、Zr、Th 和 Rb。相对于 N-MORB 值（例如，负 Nb 和 Ta 异常），AOG 通常以 LILE 和 LREE 的富集和 HFSE 的耗尽为特征。AOG 的地球化学特征遵循同化-分馏结晶 (AFC) 趋势，表明源自地幔源的岩浆受到广泛的地壳污染。AOG 的化学特征与来自阿拉伯-努比亚地盾 (ANS) 的俯冲相关花岗岩的化学特征非常相似。HYG 内从二长花岗岩到正长花岗岩到碱性长石花岗岩的成分变化不能仅用分步结晶来解释。