¹Tian-Ran Trina Du,^1,2Ai-Cheng Zhang,¹Jia-Ni Chen,³Yuan-Yun Wen
American Mineralogist 109, 24–34 Link to Article[http://www.minsocam.org/MSA/AmMin/TOC/2024/Abstracts/AM109P0024.pdf]
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
²CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
³Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 266071, China
Copyright: The Mineralogical Society of America

Shock lithification of regolith breccias is a ubiquitous process on the surfaces of airless planetary
bodies and may induce thermal effects, including melting on regolith breccia minerals. However, potential thermal effects on lithic and mineral clasts in regolith breccias have seldom been quantitatively
constrained. Here, we report two types of micro-textures of armalcolite [(Mg,Fe2+)Ti2O5] in an Mg-suite
lithic clast from lunar regolith breccia meteorite Northwest Africa 8182. One type of armalcolite contains
oriented fine-grained ilmenite grains; the other occurs as an aggregate of ilmenite, rutile, spinel, and
loveringite. We propose that the two types of micro-textures formed through subsolidus breakdown
of armalcolite by different processes. The formation of ilmenite inclusions in armalcolite is related to
slow cooling after the solidification of its source rock, whereas the ilmenite-rutile-spinel-loveringite
aggregates probably formed during the shock lithification event of NWA 8182. The results indicate
that the temperature at the margin of lithic clasts could be raised up to at least 600 °C during strong
shock lithification of lunar regolith and has profound thermal effects on the mineralogical and isotopic
behaviors of lithic and mineral fragments in lunar regolith breccias.