Rights statement: An edited version of this paper was published by AGU. Copyright 2020 American Geophysical Union. Qiao, L., Head, J. W., Wilson, L., & Ling, Z. ( 2020). The Cauchy 5 Small, Low‐Volume Lunar Shield Volcano: Evidence for Volatile Exsolution‐Eruption Patterns and Type 1/Type 2 Hybrid Irregular Mare Patch (IMP) Formation. Journal of Geophysical Research: Planets, 125, e2019JE006171. https://doi.org/10.1029/2019JE006171
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TY - JOUR
T1 - The Cauchy 5 Small, Low-Volume Lunar Shield Volcano
T2 - Evidence for Volatile Exsolution-Eruption Patterns and Type 1/Type 2 Hybrid Irregular Mare Patch Formation
AU - Qiao, L.
AU - Head, J.W.
AU - Wilson, L.
AU - Ling, Z.
N1 - An edited version of this paper was published by AGU. Copyright 2020 American Geophysical Union. Qiao, L., Head, J. W., Wilson, L., & Ling, Z. ( 2020). The Cauchy 5 Small, Low‐Volume Lunar Shield Volcano: Evidence for Volatile Exsolution‐Eruption Patterns and Type 1/Type 2 Hybrid Irregular Mare Patch (IMP) Formation. Journal of Geophysical Research: Planets, 125, e2019JE006171. https://doi.org/10.1029/2019JE006171
PY - 2020/2/29
Y1 - 2020/2/29
N2 - The lunar shield volcano Cauchy 5, sitting at the low diameter‐height‐volume end of the population, is the only known example containing two different types of Irregular Mare Patches (IMPs) in very close association: (1) the pit crater interior Type 1 IMP composed of bleb‐like mounds surrounded by a hummocky and blocky floor unit and (2) Type 2 IMPs, small, often optically immature pits less than ~5 m deep, located on the generally block‐deficient shield flanks. A four‐phase lunar magma ascent/eruption model predicts that during a relatively brief eruption, low magma rise rates maximize volatile exsolution in lava filling the pit crater. Bubble‐rich magmas overtop the pit crater and form extremely vesicular flows on the shield flanks. Exposure of the flanking flows to vacuum produces a fragmental layer of exploded glassy bubble walls. Subsequent second boiling upon cooling of the flanking flow interiors releases additional volatiles which migrate and collect, forming magmatic foams and gas pockets. As magma rise rates slow, trapped gas and magmatic foam build up below the cooling pit crater floor. Magmatic foams are extruded to form Type 1 IMP deposits. Type 2 IMPs on the flanks are interpreted to be due primarily to subsequent impacts causing collapse of the flow surface layer into the extremely vesicle‐ and void‐rich flow interior. Anomalously young pit crater floor/shield flank crater retention ages compared with surrounding maria ages may be due to effects of Cauchy 5 substrate characteristics (extreme micro‐ and macroporosity, foamy nature, and glassy auto‐regolith) on superposed crater formation and retention.
AB - The lunar shield volcano Cauchy 5, sitting at the low diameter‐height‐volume end of the population, is the only known example containing two different types of Irregular Mare Patches (IMPs) in very close association: (1) the pit crater interior Type 1 IMP composed of bleb‐like mounds surrounded by a hummocky and blocky floor unit and (2) Type 2 IMPs, small, often optically immature pits less than ~5 m deep, located on the generally block‐deficient shield flanks. A four‐phase lunar magma ascent/eruption model predicts that during a relatively brief eruption, low magma rise rates maximize volatile exsolution in lava filling the pit crater. Bubble‐rich magmas overtop the pit crater and form extremely vesicular flows on the shield flanks. Exposure of the flanking flows to vacuum produces a fragmental layer of exploded glassy bubble walls. Subsequent second boiling upon cooling of the flanking flow interiors releases additional volatiles which migrate and collect, forming magmatic foams and gas pockets. As magma rise rates slow, trapped gas and magmatic foam build up below the cooling pit crater floor. Magmatic foams are extruded to form Type 1 IMP deposits. Type 2 IMPs on the flanks are interpreted to be due primarily to subsequent impacts causing collapse of the flow surface layer into the extremely vesicle‐ and void‐rich flow interior. Anomalously young pit crater floor/shield flank crater retention ages compared with surrounding maria ages may be due to effects of Cauchy 5 substrate characteristics (extreme micro‐ and macroporosity, foamy nature, and glassy auto‐regolith) on superposed crater formation and retention.
KW - Cauchy 5
KW - lunar/Moon
KW - irregular mare patches
KW - magmatic foam
KW - mare volcanism
KW - small shield volcano
U2 - 10.1029/2019JE006171
DO - 10.1029/2019JE006171
M3 - Journal article
VL - 125
JO - Journal of Geophysical Research: Planets
JF - Journal of Geophysical Research: Planets
SN - 2169-9100
IS - 2
M1 - e2019JE006171
ER -