Petrology of impactites from El’gygytgyn crater: Breccias in ICDP-drill core 1C, glassy impact melt rocks and spherules

El'gygytgyn is a 18 km diameter, 3.6 Ma old impact crater in NE Siberia. International Continental Scientific Drilling Program--El'gygytgyn hole 1C was drilled on the frozen crater lake, 2.3 km from the crater center to a final depth of 517 m below the lake floor. Petrographic and geochemical analyses of 26 drill core samples, three impact melt rocks from the surface, and seven glass spherules from surface deposits outside the crater are used to characterize the impactite inventory at El'gygytgyn. The bottom 98 m of hole 1C intersected monomict brecciated, unshocked, rhyolitic ignimbrite with minor intercalations of polymict breccia and mafic inclusions. These lithologies are overlain by 89 m of polymict breccia whose components occasionally exhibit scarce, low-degree shock metamorphic features. This unit is succeeded by 10 m of suevite that contains about 1 vol% glassy impact melt shards