The Nuweibi albite granite (NAG) is a postcollisional intrusion emplaced as a high-level magmatic cupola into metamorphic and syntectonic calc-alkaline country rocks. It consists of two cogenetic intrusive bodies: the western, nonporphyritic, albite granite was emplaced deeper than the eastern, fine-grained, porphyritic, albite granite. In places the nonporphyritic phase crosscuts the earlier porphyritic phase, but the occurrence of gradational contacts between the phases implies a near coincidence in time, with the nonporphyritic phase emplaced before crystallization of the porphyritic phase was complete. The steeply dipping slope of the western contact of the Nuweibi pluton against country rocks, in contrast to the gently dipping contacts above the eastern and northeastern parts, indicates the probable location of the cupola apex in the eastern part of the pluton. The NAG intrusion is highly evolved meta- to peraluminous leucocratic rare-metal albite granite. The NAG intrusion is chemically zoned, with upward increases of Al2O3, Na2O, Sr, Ga, and Ta concentrations, alongside upward decreases in SiO2, K2O, Rb, Nb, Zn, Zr, Th, Sn, and rare earth element concentrations. These trends are interrupted by a compositional gap with discontinuities in evolutionary trends of both compatible and incompatible elements, suggesting multiple pulses of intrusion. The NAG was generated via partial melting of a juvenile crust that had undergone extensive fractional crystallization combined with late-magmatic fluid overprint. Accumulation of residual volatile-rich melt and exsolved fluids in the apical part of the magmatic cupola produced stockscheider pegmatite, greisen, and quartz veins that cut the peripheries of the NAG pluton. Metasomatic activity by late- to postmagmatic fluids drove changes in the bulk composition of the cupola, removing K and driving the alkali feldspars toward pure albite.

中文翻译：

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努比亚地盾晚期埃迪卡拉纪稀有金属钠长石花岗岩的地球化学和岩石成因：以埃及东部沙漠努韦比入侵为例

努韦比钠长石花岗岩 (NAG) 是一种碰撞后侵入体，它作为高级岩浆冲天炉进入变质和同构造钙碱性围岩。它由两个共生侵入体组成：西部的非斑状钠长石花岗岩比东部的细粒斑状钠长石花岗岩更深。在某些地方，非斑状相与较早的斑状相交叉，但这些相之间出现渐变接触意味着时间上几乎重合，非斑状相在斑状相结晶完成之前就位。与东部和东北部上方的缓倾接触形成对比，努韦比岩体西部接触围岩的陡倾坡，表示岩体东部冲天炉顶点的可能位置。NAG 侵入体是高度演化的准铝至过铝白光稀有金属钠长石花岗岩。NAG 侵入是化学分区的，Al2O3、Na2O、Sr、Ga 和 Ta 浓度向上增加，同时 SiO2、K2O、Rb、Nb、Zn、Zr、Th、Sn 和稀土元素浓度向上减少。这些趋势被组成差距打断，兼容和不兼容元素的进化趋势不连续，表明存在多次入侵脉冲。NAG 是通过幼年地壳的部分熔融产生的，该地壳经历了广泛的分步结晶和晚期岩浆流体叠加。岩浆冲天炉顶部残留的富含挥发分的熔体和溶出流体的积累产生了切割 NAG 岩体外围的 Stockcheider 伟晶岩、greisen 和石英脉。晚期至后岩浆流体的交代活动推动了冲天炉整体成分的变化，去除了钾并将碱性长石推向纯钠长石。