The Simlipal complex in eastern India is an elliptical structure with diameter of ca. 50 km coinciding with an elliptical region of high gravity. It overlies the Archaean basement of the Singhbhum craton and has a ring structure characterized by complex series of concentric ridges with inward dipping slopes. Quartz clasts in melt-breccias from the complex display diagnostic shock metamorphic features such as two to three sets of decorated and annealed planar deformation features (PDFs), spall and concussion micro-fractures, and the presence of coesite. They also preserve microstructures suggestive of crystallographically-controlled melting/amorphization along two or three planar directions, and within concussion micro-fractures. The inferred shock pressures in excess of 40–60 GPa are possible only during bolide impact. The Simlipal structure is possibly the remnant of a large complex impact crater having an original diameter of at least 50 km. Although zircons from an impact melt rock furnish a concordia age of 3107±14 Ma, in the absence of any unambiguous shock metamorphic effects in them, it is difficult to assign the age to the impact event. Therefore, the age of the impact is currently unconstrained.

中文翻译：

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印度东部 Singhbhum Craton 太古宙 Simlipal 杂岩的冲击变质特征：大型撞击结构的可能残余

印度东部的 Simlipal 复合体是一个椭圆形结构，直径约为 50 公里，与一个椭圆形的高重力区重合。它位于 Singhbhum 克拉通的太古代基底之上，具有环形结构，其特征是一系列复杂的同心脊和向内倾斜的斜坡。熔融角砾岩中的石英碎屑来自复杂的显示诊断冲击变质特征，例如两到三组装饰和退火的平面变形特征 (PDF)、剥落和震荡微裂缝，以及柯石英的存在。它们还保留了暗示沿两个或三个平面方向以及在震荡微裂缝内的结晶控制熔化/非晶化的微观结构。推断的超过 40-60 GPa 的冲击压力只有在火体撞击期间才有可能。Simlipal 结构可能是一个原始直径至少为 50 公里的大型复杂撞击坑的遗迹。尽管来自撞击熔岩的锆石提供了 3107±14 Ma 的协和年龄，但在它们中没有任何明确的冲击变质效应的情况下，很难将年龄归因于撞击事件。因此，影响的年龄目前不受限制。