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Mechanisms of explosive volcanism on Mercury: Implications from its global distribution and morphology
Author(s) -
Thomas Rebecca J.,
Rothery David A.,
Conway Susan J.,
Anand Mahesh
Publication year - 2014
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/2014je004692
Subject(s) - volcanism , impact crater , geology , pyroclastic rock , volcano , geochemistry , explosive eruption , mercury (programming language) , earth science , explosive material , petrology , tectonics , astrobiology , seismology , computer science , programming language , chemistry , physics , organic chemistry
Abstract The identification of widespread pyroclastic vents and deposits on Mercury has important implications for the planet's bulk volatile content and thermal evolution. However, the significance of pyroclastic volcanism for Mercury depends on the mechanisms by which the eruptions occurred. Using images acquired by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, we have identified 150 sites where endogenic pits are surrounded by a relatively bright and red diffuse‐edged spectral anomaly, a configuration previously used to identify sites of explosive volcanism. We find that these sites cluster at the margins of impact basins and along regional tectonic structural trends. Locally, pits and deposits are usually associated with zones of weakness within impact craters and/or with the surface expressions of individual thrust faults. Additionally, we use images and stereo‐derived topographic data to show that pyroclastic deposits are dispersed up to 130 km from their source vent and commonly have either no relief or low circumpit relief within a wider, thinner deposit. These eruptions were therefore likely driven by a relatively high concentration of volatiles, consistent with volatile concentration in a shallow magma chamber prior to eruption. The colocation of sites of explosive volcanism with near‐surface faults and crater‐related fractures is likely a result of such structures acting as conduits for volatile and/or magma release from shallow reservoirs, with volatile overpressure in these reservoirs a key trigger for eruption in at least some cases. Our findings suggest that widespread, long‐lived explosive volcanism on Mercury has been facilitated by the interplay between impact cratering, tectonic structures, and magmatic fractionation.