The Sedimentary Record of Meteorite Impacts
Impact melting in sedimentary target rocks: An assessment
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Published:January 01, 2007
Despite being present in the target sequence of ∼70% of the world's known impact structures, the response of sedimentary rocks to hypervelocity impact remains poorly understood. Of particular significance is the relative importance and role of impact melting versus decomposition in carbonate and sulfate lithologies. In this work, we review experimental evidence and phase equilibria and synthesize these data with observations from studies of naturally shocked rocks from several terrestrial impact sites. Shock experiments on carbonates and sulfates currently provide contrasting and ambiguous results. Studies of naturally shocked materials indicate that impact melting is much more common in sedimentary rocks than previously thought. This is in agreement with the phase relations for calcite. A summary of the criteria for the recognition of impact melts derived from sedimentary rocks is presented, and it is hoped that this will stimulate further studies of impact structures in sedimentary target rocks. This assessment leads us to conclude that impact melting is common during hypervelocity impact into both crystalline and sedimentary rocks. However, the products are texturally and chemically distinct, which has led to much confusion in the past, particularly in terms of the recognition of impact melts derived from sedimentary rocks.
- calcite
- calcium carbonate
- carbonate rocks
- carbonates
- chemically precipitated rocks
- clastic rocks
- evaporites
- experimental studies
- glass materials
- hypervelocity impacts
- immiscibility
- impact craters
- impact features
- impact melts
- impacts
- melts
- metamorphism
- phase equilibria
- quenching
- sedimentary rocks
- shock metamorphism
- spherules
- sulfates
- textures
- target rocks