Direct evidence of ancient shock metamorphism at the site of the 1908 Tunguska event

作者：Vannucchi Paola^*; Morgan Jason P; Della Lunga Damiano; Andronicos Christopher L; Morgan W Jason

来源：Earth and Planetary Science Letters, 2015, 409: 168-174.

DOI：10.1016/j.epsl.2014.11.001

• shocked quartz
• shocked metamorphism
• Siberian traps
• 1908 Tunguska event
• Verneshot

Shock metamorphism is rarely found at the surface of the Earth. The most used structures to identify shock metamorphism are "true Planar Deformation Features" (PDFs) in quartz, now accepted as diagnostic indicators of a meteorite impact. Here we present several lines of evidence for shock metamorphism and PDFs developed in quartz occurring on samples centered on a circular geological structure on Mount Stojkovic (60 degrees 54'06 '' N; 101 degrees 55'40 '' E), which lies within southern surface exposures of the Siberian Traps. The shock event appears to have occurred during the eruption of the surface Siberian Traps basalts that cover this region. Curiously, Mount Stojkovic lies within similar to 3 km of the tree fall epicenter of the 1908 Tunguska event. Based on current estimates of the Phanerozoic impact distribution, there is at most a I in similar to 17000 chance that the 1908 bolide would randomly fall on the site of a previous impact structure capable of creating shocked quartz. Just as improbable would be an airbust event, incapable of creating a small crater, that could have produced shock metamorphism. Our preferred least implausible hypothesis is that the shock-metamorphism here was associated with a terrestrial event, a hyperexplosive volcanic gas eruption called 'Verneshot'.

• 出版日期2015-1-1