Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes
Modeling the geochemical evolution of impact melts in terrestrial impact basins: Vredefort granophyre dikes and Sudbury offset dikes
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模拟陆地冲击盆地冲击熔体的地球化学演化：Vredefort 花岗岩脉和 Sudbury 偏置岩脉
DOI：
10.1111/maps.13582
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发表时间：
2020
影响因子：
2.2
通讯作者：
Riller
中科院分区：
文献类型：
--
作者：
Kovaleva;Riller
南非的Vredefort撞击构造在大小、年龄和目标岩石成分方面与加拿大的Sudbury撞击构造相当。这两种冲击结构的特点是冲击熔体堤坝。萨德伯里撞击（萨德伯里火成杂岩; SIC）的熔体片在遗传上与下面的目标岩石中的萨德伯里偏移岩脉有关。在Vredefort，熔融片被侵蚀，只有花岗斑岩脉保留组成熔融片的特点。XRF分析43个样品从四个花岗斑岩脉是类似于以前的研究，但确定一个异常的基性岩相内的一个脉。从Vredefort花岗斑岩脉的结果进行了比较，萨德伯里偏移脉，并遵循类似的地球化学趋势，控制长石和辉石的结晶。基性花岗斑岩相的成分非常相似的偏移岩墙组成。使用程序Rhyolite-MELTS来测试可能的熔体片材组合物。模拟结果与岩脉的整体化学和矿物组成基本一致。建模与源自SIC基底镁铁质层的偏移脉岩和源自碱耗尽大块大陆地壳的花岗斑岩脉岩一致。对于所有模拟的组合物，结晶主要发生在1150°C和1000°C之间的温度下。长英质花岗斑岩脉的侵位来自均质化的地壳熔体，表明侵位发生在撞击事件后的几十年内。镁铁质相的存在下的花岗斑岩脉的解释是它的侵位后的Vredefort熔体片的一些分化。
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.
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影响因子：
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作者：
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DOI：
--
发表时间：
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期刊：
影响因子：
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