The Vredefort impact structure, South Africa, is comparable to the Sudbury impact structure, Canada, in size, age, and target rock composition. Both impact structures feature impact melt dikes. The melt sheet of the Sudbury impact (Sudbury Igneous Complex; SIC) is genetically linked to the Sudbury offset dikes in the underlying target rock. At Vredefort, the melt sheet was eroded so that only the granophyre dikes retain compositional melt sheet characteristics. XRF analyses of 43 samples from four granophyre dikes are similar to previous studies, but identify an anomalous mafic phase within one of the dikes. The results from the Vredefort granophyre dikes are compared to the Sudbury offset dikes and shown to follow similar geochemical trends, controlled by crystallization of feldspar and pyroxene. The mafic granophyre phase is compositionally remarkably similar to the offset dike compositions. The program Rhyolite‐MELTS was used to test possible melt sheet compositions. Modeling results are broadly consistent with the overall chemical and mineral composition of the dikes. Modeling is consistent with offset dikes being derived from the basal mafic layer of the SIC, and the granophyre dikes being derived from alkali‐depleted bulk continental crust. For all modeled compositions, crystallization primarily occurred at temperatures between 1150°C and 1000°C. The emplacement of the felsic granophyre dikes from a homogenized crustal melt suggests emplacement within tens of years after the impact event. The presence of the mafic phase in one of the granophyre dikes is explained by its emplacement following some differentiation of the Vredefort melt sheet.

中文翻译：

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模拟地面撞击盆地撞击熔体的地球化学演化：Vredefort花岗岩堤和Sudbury补偿堤

南非的Vredefort撞击结构的尺寸，年龄和目标岩石成分与加拿大的萨德伯里撞击结构相当。两种冲击结构均具有冲击熔堤。萨德伯里冲撞的熔岩层（萨德伯里火成岩复合体； SIC）与下层目标岩石中的萨德伯里偏移堤防遗传相关。在Vredefort，熔体片受到侵蚀，因此只有粒状堤坝保留了熔体片的成分特征。X射线荧光光谱分析法对来自四个食肉动物堤防的43份样品进行的分析与以前的研究相似，但在其中一个堤防中发现了异常的镁铁质相。将Vredefort花岗岩堤坝的结果与Sudbury偏移堤坝进行了比较，结果显示遵循相似的地球化学趋势，受长石和辉石的结晶控制。镁铁质粒晶相在成分上与胶印堤坝成分非常相似。Rhyolite-MELTS程序用于测试可能的熔片组成。建模结果与堤防的总体化学和矿物成分基本一致。建模与从SIC的基性镁铁质层中得到的偏移堤防是一致的，并且从贫碱的大块大陆壳中得到的是花岗石堤防。对于所有建模的组合物，结晶主要发生在1150°C至1000°C之间的温度下。从均质的地壳熔体中的长丝质食草堤的位置表明，在撞击事件发生后的几十年内就发生了位置。