TY - JOUR
T1 - Protracted volcanism after large impacts
T2 - Evidence from the Sudbury impact basin
AU - Ubide, Teresa
AU - Guyett, Paul C.
AU - Kenny, Gavin G.
AU - O'Sullivan, Edel M.
AU - Ames, Doreen E.
AU - Petrus, Joseph A.
AU - Riggs, Nancy
AU - Kamber, Balz S.
N1 - Funding Information:
This research was funded by Science Foundation Ireland grant SFI/12/ERC/E2499. The data used are available in the figures, supporting information files, and cited references. We thank Lindsay Hall (Canadian Institute for Mining, Metallurgy and Petroleum) for her help in the field and Rodney Allen (Luleå University of Technology, Sweden) for insightful discussions on vitric clast morphologies. We are grateful to Editor D. Baratoux, an anonymous Associate Editor, reviewers G.R. Osinski and C. Hamann, and two anonymous reviewers for insightful comments on a previous version of the manuscript. Special thanks to Claire Kamber for her help with the maps and illustrations.
Publisher Copyright:
©2017. American Geophysical Union. All Rights Reserved.
PY - 2017/4/1
Y1 - 2017/4/1
N2 - Morphological studies of large impact structures on Mercury, Venus, Mars, and the Moon suggest that volcanism within impact craters may not be confined to the shock melting of target rocks. This possibility prompted reinvestigation of the 1.85 Ga subaqueous Sudbury impact structure, specifically its 1.5 km thick immediate basin fill (Onaping Formation). Historically, breccias of this formation were debated in the context of an endogenic versus an impact-fallback origin. New field, petrographic, and in situ geochemical data document an array of igneous features, including vitric shards, bombs, sheet-like intrusions, and peperites, preserved in exquisite textural detail. The geochemistry of vitric materials is affected by alteration, as expected for subaqueous magmatic products. Earlier studies proposed an overall andesitic chemistry for all magmatic products, sourced from the underlying impact melt sheet. The new data, however, suggest progressive involvement of an additional, more magnesian, and volatile-rich magma source with time. We propose a new working model in which only the lower part of the Onaping Formation was derived by explosive “melt-fuel-coolant interaction” when seawater flooded onto the impact melt sheet in the basin floor. By contrast, we suggest that the upper 1000 m were deposited during protracted submarine volcanism and sedimentary reworking. Magma was initially sourced from the impact melt sheet and up stratigraphy, from reservoirs at greater depth. It follows that volcanic deposits in large impact basins may be related to magmatism caused by the impact but not directly associated with the impact-generated melt sheet.
AB - Morphological studies of large impact structures on Mercury, Venus, Mars, and the Moon suggest that volcanism within impact craters may not be confined to the shock melting of target rocks. This possibility prompted reinvestigation of the 1.85 Ga subaqueous Sudbury impact structure, specifically its 1.5 km thick immediate basin fill (Onaping Formation). Historically, breccias of this formation were debated in the context of an endogenic versus an impact-fallback origin. New field, petrographic, and in situ geochemical data document an array of igneous features, including vitric shards, bombs, sheet-like intrusions, and peperites, preserved in exquisite textural detail. The geochemistry of vitric materials is affected by alteration, as expected for subaqueous magmatic products. Earlier studies proposed an overall andesitic chemistry for all magmatic products, sourced from the underlying impact melt sheet. The new data, however, suggest progressive involvement of an additional, more magnesian, and volatile-rich magma source with time. We propose a new working model in which only the lower part of the Onaping Formation was derived by explosive “melt-fuel-coolant interaction” when seawater flooded onto the impact melt sheet in the basin floor. By contrast, we suggest that the upper 1000 m were deposited during protracted submarine volcanism and sedimentary reworking. Magma was initially sourced from the impact melt sheet and up stratigraphy, from reservoirs at greater depth. It follows that volcanic deposits in large impact basins may be related to magmatism caused by the impact but not directly associated with the impact-generated melt sheet.
KW - Explosive volcanism
KW - Impact basin
KW - Subaqueous volcanism
KW - Sudbury structure
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U2 - 10.1002/2016JE005085
DO - 10.1002/2016JE005085
M3 - Article
AN - SCOPUS:85018636894
SN - 2169-9097
VL - 122
SP - 701
EP - 728
JO - Journal of Geophysical Research: Planets
JF - Journal of Geophysical Research: Planets
IS - 4
ER -