Spectroscopic and Geochemical Characterization of Lunar Breccia NWA 11421: Insights into the Lunar Crust–Mantle Composition and Implication for Moon Exploration

 

: FPA hyperspectral mineral mapping of micro-regions across the NWA 11421 lunar meteorite D- and S-faces. For each region analyzed (S1, D1, D2, D3), cluster maps derived from μ-FTIR FPA data highlight compositional variability, with color scales indicating dominant mineralogical components and emphasizing the heterogeneous nature of the sample (reproduced from Alberini et al., 2026, Remote Sensing, © 2026 The Authors, CC BY).

 

Introduction

Lunar meteorites are a valuable source of information for understanding the Moon’s geology because they originate from different areas across the lunar surface. In contrast, the samples from the Apollo/Luna missions are restricted to precise locations on the visible side and do not necessarily represent the overall composition of the lunar surface [1][2]. Therefore, the meteorites provide a more global perspective on lunar mineralogical diversity and offer key insights into its overall composition and evolution [1][2][3][4]. NWA 11421 is a lunar meteorite discovered in Morocco in 2017 (total mass ~ 912 g), classified as a feldspathic breccia [5]. Petrographically, it consists of angular to subrounded whitish clasts up to 1 cm in size set into a greyish vitreous groundmass. Dominant mineral phases reported in the Meteoritical Bulletin include low-Ca pyroxene, high-Ca pyroxene, olivine and calcic plagioclase. Minor phases include chromite, ilmenite, fayalite, pyrrhotite, FeNi metal and barite [5]. Of particular significance is the discovery, within NWA 11421, of a dunite clast measuring approximately 1 cm, interpreted as the first fragment of lunar mantle material identified to date [6]. Indeed, the discovered dunite clast exhibits a homogeneous mineral composition, suggesting internal chemical equilibrium and derivation from a deep-seated, mantle-derived source, offering a unique window into the lunar interior beyond the crustal materials typically sampled [6]. This study aims to refine the characterization and broaden the statistical dataset of these samples, enhancing our understanding of feldspathic lunar meteorites and assessing the possible presence of dunitic clasts indicative of a mantle-derived origin.

 

Methods

A comprehensive suite of non-destructive analytical techniques was used. At the INAF–Astrophysical Observatory of Arcetri, bulk Visible and Near/Mid-Infrared reflectance spectroscopy was performed using Diffuse Reflectance Infrared Fourier Transform (DRIFT) collected by a Bruker VERTEX 70v FTIR interferometer, equipped with a Harrick Praying Mantis™ accessory. This configuration provided overall spectral information representative of the entire sample. For microscale assessments, the same VERTEX 70v system was interfaced with a HYPERION 1000 μ-FTIR microscope equipped with a 64×64 pixel Focal-Plane Array (FPA) detector (~ 2 μm spatial resolution) performing cluster analyses. Complementary chemical mapping was carried out at the IBeA research group of the University of the Basque Country (EHU), using μ-EDXRF, which provided high resolution elemental distribution maps (particularly useful for identifying compositional zoning and supporting spectral interpretations), and Raman imaging employed as a supportive technique to confirm mineral textures and phase associations, reinforcing the identifications derived from FTIR and X-ray fluorescence analyses.

 

Results

NWA 11421 results confirm a dominant anorthositic composition, consistent with its classification as a feldspathic breccia, with significant contributions from forsteritic olivine and low-Ca pyroxenes (pigeonite and ferrosilite) (Figure 1) [7]. At bulk and meso-scale, olivine-bearing anorthositic domains define troctolitic compositions, while LCP-rich regions are spatially anti-correlated with the feldspathic matrix, reflecting the polymict nature of the breccia. Micro-scale observations reveal discrete mafic domains embedded within the anorthositic matrix, indicating that lithological heterogeneity is preserved down to the micron scale. Bright mineral inclusions are assigned to plagioclase glass. Near-infrared pyroxene band positions fall within the orthopyroxene field, confirming the dominance of LCPs and suggesting relatively mafic and primitive components. This interpretation is supported by the Christiansen Feature (CF) position, which is shifted toward the pyroxene-rich region of the silicate ternary diagram compared to typical Apollo highland samples. Moreover, CF values are consistent with those measured by the Diviner Lunar Radiometer Experiment in lunar crater-ejecta terrains, establishing a direct link between laboratory measurements and orbital remote sensing observations. These results demonstrate the effectiveness of a multi-scale, non-destructive spectroscopic approach in bridging laboratory analyses and orbital datasets, providing a robust framework to refine the interpretation of lunar mineralogical maps and to support future exploration strategies.

 

References:

[1] Korotev R. L. (2005) Chem. Erde, 65, 297–346.

[2] Joy K. H. and Arai T. (2013) Astron. Geophys., 54, 4.28–4.32.

[3] Joy K. H. et al. (2016) Earth Moon Planets, 118, 133–158.

[4] Warren P. H. (2005) Meteorit. Planet. Sci., 40, 477–506.

[5] The Meteoritical Bulletin, No. 106. https://www.lpi.usra.edu/meteor/docs/mb106.pdf

[6] Treiman A. H. and Semprich J. (2023) Am. Mineral., 108, 2182–2192.

[7] Alberini A. et al. (2026) Remote Sens., 18, 576.

 

Acknowledgements: This research was funded by the Space It Up project funded by the Italian Space Agency, ASI, and the Ministry of University and Research, MUR, under contract n. 2024-5-E.0-CUP n. I53D24000060005. F.A., J.A., and J.M.M. acknowledge the support of the PAMMAT project funded by the Spanish Agency for Research, Contract No. PID2022-142750OB-I00, funded by the Spanish Agency for Research AEI (through the Spanish Ministry of Science and Innovation, MCIN, and the European Regional Development Fund, FEDER, MCIN/AEI/10.13039/501100011033/FEDER, UE).