TY - JOUR
T1 - On the eruptive origins of lunar localized pyroclastic deposits
AU - Keske, Amber L.
AU - Clarke, Amanda B.
AU - Robinson, Mark S.
N1 - Funding Information:
This work was supported by the NASA LRO project (grant number NNG07EK00C) and the NSF GRFP (grant number DGE-1311230). We extend our deepest thanks to Megan Henriksen, Madeleine Manheim, and the rest of the LROC SOCETSET team for making it possible to produce the high-quality DTMs used in this work. We would also like to thank the LROC team as a whole for efforts toward providing the data products used in this work and for scientific feedback during its progress. Finally, we thank the anonymous reviewers and editor whose comments have strengthened this manuscript.
Funding Information:
This work was supported by the NASA LRO project (grant number NNG07EK00C ) and the NSF GRFP (grant number DGE-1311230 ). We extend our deepest thanks to Megan Henriksen, Madeleine Manheim, and the rest of the LROC SOCETSET team for making it possible to produce the high-quality DTMs used in this work. We would also like to thank the LROC team as a whole for efforts toward providing the data products used in this work and for scientific feedback during its progress. Finally, we thank the anonymous reviewers and editor whose comments have strengthened this manuscript.
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - Localized pyroclastic deposits (LPDs) are low-albedo accumulates of pyroclastic material with distinct positive topographic signatures that are found dominantly along highland-mare boundaries. Previous workers hypothesized that LPDs represent products of a lunar equivalent of Vulcanian-style eruptions, based in part on the observation that some of the deposits in Alphonsus Crater have large vent volumes in comparison with their deposit volumes, indicating a low proportion of juvenile material in the deposits. The objective of this study is to better understand eruption mechanisms by determining how the proportion of juvenile material, as calculated using deposit and vent volumes, varies among LPDs in Alphonsus Crater and elsewhere on the Moon using contemporary data and methods. Deposit and vent volumes for 23 LPDs from eleven sites were calculated by differencing current and modeled pre-eruption surfaces using digital terrain models (DTMs) derived from Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). Results show that LPDs have a wide range of juvenile proportions, many of which are more juvenile-rich than previously thought. Additionally, there is a positive relationship between juvenile material proportion and deposit volume and thickness, and a positive relationship between juvenile volume and dispersal area. LPDs also bear a broad range of thinning profiles which span a range of multiple eruption types on Earth. These findings, along with previous studies employing spectroscopic analysis of these deposits, indicate there is greater diversity among LPDs in composition and morphometry than previously understood, and that previously published simplified Vulcanian models may apply only to the deposits containing the least amount of juvenile material, with all others perhaps requiring a combination of multiple eruptive mechanisms. Furthermore, dynamic model results suggest that the most widespread lunar deposits in this study were formed by magma containing 2000–5000 ppm of dissolved volatiles, consistent with recent estimates via melt inclusion analysis, but contrary to long-held ideas that the Moon was largely degassed during its formation.
AB - Localized pyroclastic deposits (LPDs) are low-albedo accumulates of pyroclastic material with distinct positive topographic signatures that are found dominantly along highland-mare boundaries. Previous workers hypothesized that LPDs represent products of a lunar equivalent of Vulcanian-style eruptions, based in part on the observation that some of the deposits in Alphonsus Crater have large vent volumes in comparison with their deposit volumes, indicating a low proportion of juvenile material in the deposits. The objective of this study is to better understand eruption mechanisms by determining how the proportion of juvenile material, as calculated using deposit and vent volumes, varies among LPDs in Alphonsus Crater and elsewhere on the Moon using contemporary data and methods. Deposit and vent volumes for 23 LPDs from eleven sites were calculated by differencing current and modeled pre-eruption surfaces using digital terrain models (DTMs) derived from Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). Results show that LPDs have a wide range of juvenile proportions, many of which are more juvenile-rich than previously thought. Additionally, there is a positive relationship between juvenile material proportion and deposit volume and thickness, and a positive relationship between juvenile volume and dispersal area. LPDs also bear a broad range of thinning profiles which span a range of multiple eruption types on Earth. These findings, along with previous studies employing spectroscopic analysis of these deposits, indicate there is greater diversity among LPDs in composition and morphometry than previously understood, and that previously published simplified Vulcanian models may apply only to the deposits containing the least amount of juvenile material, with all others perhaps requiring a combination of multiple eruptive mechanisms. Furthermore, dynamic model results suggest that the most widespread lunar deposits in this study were formed by magma containing 2000–5000 ppm of dissolved volatiles, consistent with recent estimates via melt inclusion analysis, but contrary to long-held ideas that the Moon was largely degassed during its formation.
KW - Moon
KW - Moon, surface
KW - basaltic volcanism
KW - explosive volcanism
KW - lunar volatiles
KW - volcanism
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U2 - 10.1016/j.epsl.2020.116426
DO - 10.1016/j.epsl.2020.116426
M3 - Article
AN - SCOPUS:85088644420
SN - 0012-821X
VL - 547
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
M1 - 116426
ER -