Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland
Provenance of altered carbon phases and impact history of the Stac Fada Member, NW Scotland
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DOI：
10.1111/maps.14035
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发表时间：
2023-07
影响因子：
2.2
通讯作者：
A. Goodwin;R. Tartèse;R. Garwood;R. Jerrett;K. Joy
中科院分区：
文献类型：
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作者：
A. Goodwin;R. Tartèse;R. Garwood;R. Jerrett;K. Joy
Stac Fada段（Stoer群）是苏格兰西北海岸沿着保存并间歇出露的~1.2 Ga熔融富集的撞击角砾岩。使用X射线衍射和微拉曼光谱的组合，我们确定潜在的柯石英是空间上与微米级金刚石，以及无序的碳相。将撞击角砾岩中无序碳相的石墨G带与下层单元的样品进行比较，表明Stoer群中的大部分碳最终来自下层刘易斯基底。斯塔克法达成员内的无序碳相已被修改的温和加热内的热喷出物毯，而不是冲击压力。我们还报告了在Stac Fada成员中发现的撞击钻石的第一个证据。这些钻石的平均拉曼位移为1328.5 cm−1，存在于直接位于Stac Fada段接触面下的砂岩中的冲击角砾岩和冲击片麻岩碎屑中，以及该单元中捕获的砂岩筏中。这些研究结果有影响的沉积时间的Stac Fada成员，这必须发生后，弹道弹射的刘易斯基底碎屑在影响事件。
The Stac Fada Member (Stoer Group) is a ~1.2 Ga melt‐rich impact breccia preserved and intermittently exposed along the NW coast of Scotland. Using a combination of x‐ray diffraction and micro‐Raman spectroscopy, we identify potential coesite that is spatially associated with micron‐sized diamonds, as well as disordered carbon phases. Comparing the graphite G‐band of disordered carbon phases in the impact breccia to samples from underlying units indicates that most of the carbon in the Stoer Group was ultimately derived from the underlying Lewisian basement. Disordered carbon phases within the Stac Fada Member have been modified by mild heating within a hot ejecta blanket rather than shock pressure. We also report the first evidence for impact diamonds discovered within the Stac Fada Member. These diamonds have an average Raman shift of 1328.5 cm−1 and are present within both the impact breccia and the shocked gneiss clasts that are present in sandstones directly underlying the Stac Fada Member contact, and within sandstone rafts entrapped in the unit. These findings have implications for the timing of deposition of the Stac Fada Member, which must have occurred after ballistic ejection of Lewisian basement clasts during the impact event.