Characterization and significance of shocked quartz from the Woodleigh mpact structure, Western Australia
Characterization and significance of shocked quartz from the Woodleigh mpact structure, Western Australia
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西澳大利亚伍德利撞击构造中冲击石英的特征和意义
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发表时间：
2003
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影响因子：
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通讯作者：
A. Bevan
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作者：
R. Hough;Martin R Lee;A. Bevan
摘要-我们重新检查了西澳大利亚州埋藏的伍德利结构，该结构被推断为一个多环、直径120公里的撞击坑，因为所提出的大小和可能与中生代前大规模灭绝事件之一的同步性引起了争议。我们对从Woodleigh-1井中钻入构造中央隆起的一些岩芯样品进行了详细的岩石学和矿物学研究。在Woodleigh-1岩芯中，由花岗岩和片麻岩组成的结晶元古代基岩在离散的矿脉中含有少量角砾岩，并揭示了整个岩心范围内发生冲击变质作用的明显证据。实验室刻蚀石英的成像显示，大量的颗粒含有冲击变形片层。用透射电子显微镜对这些片层进行了显微组织和结晶学分析，结果表明，这些片层为平面形变特征(PDF)，随后经过了热处理和水辅助再结晶。现有的地质、岩石学和矿物学证据表明，伍德利是一个直径接近60公里而不是120公里的被侵蚀的撞击坑。未来的钻探项目应该更好地限制侵蚀程度，并可能揭示任何保存下来的撞击岩性。
Abstract— We re‐examined the buried Woodleigh structure in Western Australia, which has been inferred to be a multi‐ringed, 120 km diameter impact crater, because the proposed size and possible synchronicity with one of the pre‐Mesozoic mass extinction events has attracted controversy. We undertook a detailed study of the petrology and mineralogy of a number of samples of core from the Woodleigh‐1 borehole that was drilled into the central uplift of the structure. Crystalline Proterozoic basement rocks comprising granites and gneisses in the Woodleigh‐1 core contain minor brecciation in discrete veins and reveal clear evidence of shock metamorphism over the full extent of the core. Imaging of laboratory‐etched quartz showed that a large number of grains contain shock deformation lamellae. Microstructural and crystallographic analysis of these lamellae by TEM showed that they are planar deformation features (PDFs) that have subsequently undergone annealing and water assisted recrystallization. The available geological, petrographic, and mineralogical evidence suggest that Woodleigh is an eroded impact crater that is nearer to 60 km than 120 km in diameter. Future drilling projects should better constrain the level of erosion, and may reveal any preserved impact lithologies.