We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Evidence for Extrusive Mg‐Suite Magmatism on the Moon? Fine‐Grained Magnesian Clasts in an Apollo 16 Impact Melt Breccia.
- Authors
Stadermann, Amanda C.; Barnes, Jessica J.; Erickson, Timmons M.; Prissel, Tabb C.; Michels, Zachary D.
- Abstract
The magnesian suite (Mg‐suite) of rocks record some of the earliest intrusive magmatism on the Moon. Studies of these Mg‐suite rocks find they are plutonic or hypabyssal, formed typically kilometers under the lunar surface. Several models exist to explain the formation and evolution of the Mg‐suite but distinguishing between hypotheses can be difficult given the limited sample availability. The global extent of Mg‐suite magmatism remains in debate and is key to constraining models of early secondary crust building. In this study, we present magnesian clasts within Apollo impact melt rock 68815. These clasts contain olivine, plagioclase, with minor amounts of Mg‐Al‐spinel and pyroxene similar to spinel troctolites of the Mg‐suite, but they lack plutonic textures. We provide evidence that some of the clasts may be of extrusive volcanic origin akin to terrestrial komatiites while others might represent crystalline impact melts. There exists a large breadth of evidence for Mg‐suite intrusives, whereas here, we present possible evidence of Mg‐rich volcanic counterparts. If valid, this would broaden the known diversity of lunar volcanism during the initial stages of secondary crust building. We anticipate this finding to provide a greater constraint onto models of Mg‐suite ascent and emplacement, which only currently consider intrusive magmatism, as well as renewed motivation to examine impact melt breccias for rare and understudied lithologies. Future trace element studies or radiometric dating could be used to further interrogate the connections of these clasts to the Mg‐suite. Plain Language Summary: Magnesium‐rich rocks found on the Moon are collectively termed the Mg‐suite and generally crystallized kilometers beneath the lunar surface. There are several competing models that explain how these rocks formed and evolved. Distinguishing between these models involves characterizing a wide variety of Mg‐rich lunar material. In this work, we present unique Mg‐rich rock fragments that contain the same minerals of similar composition as the Mg‐suite rocks but have textures that indicate they did not crystallize at depth under the surface. There are two general ways these rock fragments could have formed. First, the same Mg‐rich magmas that formed the Mg‐suite could have erupted onto the Moon's surface, creating a volcanic deposit. Second, an impact event could have struck the lunar surface and melted pre‐existing Mg‐suite rocks, which then cooled quickly on the lunar surface. We present evidence that some of these rock fragments could possibly be volcanic in origin, while others almost certainly formed via an impact. If some of the rock fragments are indeed volcanic, it would call for a reevaluation of Mg‐suite emplacement models because these models currently only consider rocks crystallized beneath the lunar surface. More work is needed to definitively identify these rock fragments as volcanic. Key Points: Fine‐grained lunar Mg‐rich clasts have been identified in Apollo impact melt breccia 68815Some of these clasts may be volcanic in origin, while others are likely crystalline impact meltThe finding of potential volcanic Mg‐suite clasts adds to the complexity and diversity of early lunar secondary crust building
- Subjects
BRECCIA; LUNAR surface; MAGMATISM; MOON; RADIOACTIVE dating; VOLCANIC ash, tuff, etc.
- Publication
Journal of Geophysical Research. Planets, 2023, Vol 128, Issue 8, p1
- ISSN
2169-9097
- Publication type
Article
- DOI
10.1029/2022JE007728