Occurrence and implications of secondary olivine veinlets in lunar highland breccia Northwest Africa 11273

Abstract

Lunar breccias preserve the records of geologic processes on the Moon. In this study, we report the occurrence, petrography, mineralogy, and geologic significance of the observed secondary olivine veinlets in lunar feldspathic breccia meteorite Northwest Africa (NWA) 11273. Bulk-rock composition measurements show that this meteorite is geochemically similar to other lunar highland meteorites. In NWA 11273, five clasts are observed to host veinlets that are dominated by interconnecting olivine mineral grains. The host clasts are mainly composed of mafic minerals (i.e., pyroxene and olivine) and probably sourced from a basaltic lithology. The studied olivine veinlets (~5 to 30 lm in width) are distributed within the mafic mineral host, but do not extend into the adjacent plagioclase. Chemically, these olivine veinlets are Fe-richer (Fo 41.4-51.9), compared with other olivine grains (Fo 54.3-83.1) in lithic clasts and matrix of NWA 11273. By analogy with the secondary olivine veinlets observed in meteorites from asteroid Vesta (howardite-eucrite-diogenite group samples) and lunar mare samples, our study suggests that the newly observed olivine veinlets in NWA 11273 are likely formed by secondary deposition from a lunar fluid, rather than by crystallization from a high-temperature silicate melt. Such fluid could be sulfur-and phosphorous-poor and likely had an endogenic origin on the Moon. The new occurrence of secondary olivine veinlets in breccia NWA 11273 reveals that the fluid mobility and deposition could be a previously underappreciated geological process on the Moon.

How do secondary iron enrichments form within basaltic eucrites? An experimental approach

“…2018; Zeng et al. 2020) implying that such metasomatic effects were common in nominally anhydrous bodies such as Vesta and the Moon. However, thermal metamorphism on Vesta might have erased those metasomatic features which may have formed in restricted areas on the parent body.…”

Experimentally Induced Thermal Fatigue on Lunar and Eucrite Meteorites—Influence of the Mineralogy on Rock Breakdown

“…The easier comminution of feldspar relative to for example, pyroxene or olivine has also been proven to be more effective with respect to impact experiments (Cintala & Hoerz, 1992;Hörz et al, 1984Hörz et al, , 2020. This, however, may only be applied to the regions where rocks similar to lunar anorthositic breccias are available, likely the highlands outside the South Pole-Aitken basin (Zeng et al, 2020). Hörz et al (2020) reported on the influence of micrometeorite impacts on the alteration of lunar surface rocks.…”

New Evidence for 4.32 Ga Ancient Silicic Volcanism on the Moon

“…NWA 10447 is a regolith breccia meteorite consolidated from the surface materials on the Moon. By comparing this meteorite's composition with the global gamma ray spectroscopy geochemical data, the possible ejection regions of the lunar meteorite have been constrained (e.g., Calzada‐ Diaz et al, 2015; Gross & Joy, 2016; Joy et al., 2010; Zeng et al., 2018; Zeng, Li, et al., 2020). In this study, we used this geochemical data (i.e., FeO = 15.15 ± 1 wt%, TiO 2 = ± 1 wt%, and Th = 0.79 ± 1 ppm; Korotev and Irving, 2021; Table ) as input parameters to locate regolith samples that are compositionally similar to NWA 10447 (see Text for details).…”