Abstract The Wadi Hawashiya, North Eastern Desert of Egypt, is a mountainous granitic terrain exposing two Ediacaran granitoid suites, namely the Hawashiya Older Granites (HOG) and the Hawashiya Younger Granites (HYG). The HOG comprise normal to high-K, calc-alkaline, metaluminous granitoids (mainly quartz diorites), while the HYG are strongly high-K, calc-alkaline, slighty peraluminous syeno- and monzogranites. Zr is strikingly high (av. 335 ppm) in the HOG and is notably depleted (av. 108 ppm) in the more evolved HYG. The HYG have very low Nb contents almost matching those of the HOG (Nb ~ 6 ppm), which is typical of I-type granites generated at arc-type settings. Although the REE patterns of the HOG and HYG are comparably LREE-enriched with moderately steep slopes, the patterns of the HYG have significant deep negative Eu anomalies of variable magnitudes, whereas those of the HOG usually exhibit very shallow negative and occasional positive Eu anomalies. The assessed apatite crystallization temperatures for both granitoid suites are higher than those estimated from the zircon and monazite thermometers indicating that apatite crystallized before zircon and monazite from the melt. HOG evolved by assimilation-fractional crystallization processes from mantle-derived magmas, which subsequently interacted with crustal sources during ascent and residence in higher crustal levels. 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. The HYG were emplaced (586–601 Ma) after the collision between the juvenile crust of the Arabian-Nubian Shield (ANS) and the older pre-Neoproterozoic continental blocks of Saharan Metacraton. The emplacement of HOG (622-611 Ma) had occured earlier (ca. 10 Ma) in a normal mature continental arc. The geochemical signatures and age data suggest that the terminal collision between East and West Gondwanaland in the northern tip of the ANS occurred before ~620 Ma, most likely at ~630 Ma, and transitioned to an extensional setting at ~600 Ma.

中文翻译：

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埃迪卡拉纪大陆弧和埃及东北沙漠 Wadi Hawashiya 碰撞后花岗岩的 U-Pb 锆石年代学和地球化学约束：对阿拉伯-努比亚地盾最北端约 600 Ma 地壳形成事件的洞察

摘要 埃及东北部沙漠的瓦迪哈瓦希亚是一个多山的花岗岩地形，暴露出两个埃迪卡拉纪花岗岩类，即哈瓦西亚老花岗岩（HOG）和哈瓦西亚新花岗岩（HYG）。HOG 包括正常至高 K、钙碱性、金属铝质花岗岩（主要是石英闪长岩），而 HYG 是强高 K、钙碱性、轻微过铝质正长花岗岩和二长花岗岩。Zr 在 HOG 中非常高（平均 335 ppm），并且在更进化的 HYG 中显着耗尽（平均 108 ppm）。HYG 的 Nb 含量非常低，几乎与 HOG 的 Nb 含量相匹配（Nb ~ 6 ppm），这是在弧型设置下生成的 I 型花岗岩的典型特征。尽管 HOG 和 HYG 的 REE 模式相对富含轻稀土，且坡度适中，HYG 的模式具有显着的深度变化的 Eu 负异常，而 HOG 的模式通常表现出非常浅的负 Eu 异常和偶尔的正 Eu 异常。评估的两种花岗岩组的磷灰石结晶温度高于从锆石和独居石温度计估计的温度，表明磷灰石先于锆石和独居石从熔体中结晶出来。HOG 通过来自地幔来源的岩浆的同化-分馏结晶过程演化而来，随后在上升和停留在较高地壳层的过程中与地壳源相互作用。将 HYG 的全岩成分与变质沉积岩和岩浆岩的实验脱水熔融产生的熔体相关联，表明它们似乎是由砂质和泥质变沉积物的扩展熔融产生的。HYG 是在阿拉伯-努比亚地盾 (ANS) 的幼年地壳与撒哈拉 Metacraton 的前新元古代大陆块发生碰撞后就位 (586-601 Ma)。在正常成熟大陆弧中，HOG（622-611 Ma）的就位发生较早（约 10 Ma）。地球化学特征和年龄数据表明，ANS 北端东西冈瓦纳大陆之间的最终碰撞发生在~620 Ma 之前，最有可能发生在~630 Ma，并在~600 Ma 过渡到伸展环境。HYG 是在阿拉伯-努比亚地盾 (ANS) 的幼年地壳与撒哈拉 Metacraton 的前新元古代大陆块发生碰撞后就位 (586-601 Ma)。在正常成熟大陆弧中，HOG（622-611 Ma）的就位发生较早（约 10 Ma）。地球化学特征和年龄数据表明，ANS 北端东西冈瓦纳大陆之间的最终碰撞发生在~620 Ma 之前，最有可能发生在~630 Ma，并在~600 Ma 过渡到伸展环境。HYG 是在阿拉伯-努比亚地盾 (ANS) 的幼年地壳与撒哈拉 Metacraton 的前新元古代大陆块发生碰撞后就位 (586-601 Ma)。在正常成熟大陆弧中，HOG（622-611 Ma）的就位发生较早（约 10 Ma）。地球化学特征和年龄数据表明，ANS 北端东西冈瓦纳大陆之间的最终碰撞发生在~620 Ma 之前，最有可能发生在~630 Ma，并在~600 Ma 过渡到伸展环境。