Chemical, isotopic (O, He, U), and petrological characteristics of a slowly cooled enriched gabbroic shergottite, Northwest Africa 13134

Abstract

Copyright and License

© 2025 The Meteoritical Society.

Acknowledgement

Data Availability

Data that support the findings of this study are openly available at Zenodo: https://doi.org/10.5281/zenodo.14834532.

Supplemental Material

maps14345-sup-0001-Supinfo.pdf

Figure S1. Panels A and B are photographs of the 13.5 g piece of NWA 13134 acquired by JPL. Panel C is a 3D reconstruction of micro X-ray computed tomography data (Eckley et al., 2024), showing the positions of the two cuts made from the bulk sample. The polished thin sections from this study were made from slices of the corner separated from the first cut.

Figure S2. Reflected light microphotographs of polished thin sections of NWA 13134. Left: PTS-1A. Righ: PTS-1B. Both slices are embedded in epoxy and mounted on glass slides.

Figure S3. WDS and EBSD phase maps from PTS-1A. Ca Kα maps are shown in the top row and EBSD phase maps are shown in the bottom row. In the EBSD panels, blue is mapped to diopside and yellow is mapped to pigeonite structures. Left column: Area 1, middle column: Area 2, right column: Area 3. The three areas are shown in context of PTS-1A in Figure 2 in the main text. Some of the noise may reflect the ubiquitous exsolution lamellae present in all the pyroxenes studied.

Figure S4. Compositions of pyroxenes pairs analyzed on adjacent sides of Ca-zones overlain on the 1 atm pyroxene quadrilateral and isotherms copied from Lindsley and Andersen (1983). Lines connect pairs of low-Ca and high-Ca pyroxenes. The red squares are pyroxene components as defined by Lindsley and Andersen (1983); the blue squares are simple Wo, En, Fs components (e.g., Morimoto et al., 1988). The top-left inset shows a Ca WDS map of a pyroxene showing examples high-Ca (bright) and low-Ca (zones) where pyroxene pair data were collected. The very bright phase is merrillite. he top-left inset shows a backscattered electron image of exsolution lamellae at the rim of an augitic pyroxene; the arrows point to the corresponding analyses projected into the pyroxene quadrilateral.

Figure S5. WDS element maps of a pyroxene grain exposed perpendicular to [001] which has particularly coarse and wavy exsolution lamellae. It is the same pyroxene grain shown in the upper-left portion of Area 1 (i.e., Figures 2B and 3A–C in the main text). The grayscale images have been stretched to enhance contrast. Top row: Si, Ca, Fe, Mg. Bottom row: Ti, Na, Mn, Al. A glassy inclusion is present at the pyroxene center.

Figure S6. Left panel is a backscattered electron image showing maskelynite (msk), pyroxene (pyx), merrillite (mer), silica (SiO₂), and other minor phases. The red circles with lables indicate the locations of analyses in the microprobe traverse shown in the right panel. The right panel shows the CaO (red), Na₂O (blue) contents along the traverse (left y-axis) and the corresponding An# (green; An = Ca/[Ca+Na+K], molar; right y-axis). The x-axis is distance in microns from the pyroxene at the left-hand side of the traverse shown in the left panel.

Figure S7. (A) Backscattered electron image of a sulfide grain with wavy two-pyrrhotite intergrowths and fractures filled by Fe oxide. (B) Reflected light image of the same grain showing the position of the 532 nm Raman laser on the oxide phase. (C) The associated Raman spectrum is shown in black and is compared to reference spectra of magnetite (red) and goethite (blue) from the RRUFF database (https://rruff.info/). Sample IDs are shown in the legend. Note that the spectrum from NWA 13134 is a close match to magnetite. Spectra were collected using an inVia Raman Spectroment with a 532 nm laser and using Si as a reference material.

Figure S8. Bulk measurements of martian meteorite Mg# versus V/Sc (left panel) and Ge/Si (right panel). Mg# = Mg/[Mg+Fe*], molar where all Fe is FeO. These plots demonstrate the low Sc (14.8 ppm) and high Ge (7.3 ppm) contents of NWA 13134 relative to other published bulk rock measurements of martian meteorites. Literature data and classification scheme from Udry et al. (2020). NWA 13227 data is from Benaroya et al. (2024).

Figure S9. O isotope composition of NWA 13134 (red stars) and other martian meteorites (Ali et al., 2016). TFL is the Terrestrial Fractionation Line.

Figure S10. Bulk measurements of martian meteorite Mg# versus Ba/La (left) and Sr/Na (right). High values of these element ratios reflect contamination by terrestrial fluids. NWA 13134 plots within the relatively pristine field of shergottites. Note that the Nakhlites have high Sr/Na relative to shergottites, this likely reflects different source compositions rather than terrestrial weathering.

Figure S11. Compilation of literature measurements of pyroxenes in martian meteorites projected onto the pyroxene quadrilateral. The dashed grey curves shows the approximate boundary of the metastable pyroxene field at 1 atm, after Lindsley and Andersen (1983). In the top-left panel, the red stars are NWA 13134 (this study). For the shergottites, green = enriched, cyan = intermediate, and blue = depleted following the classification of Udry et al. (2020). Data sources: Smith and Herwig (1979), BSVP (1981), Stöffler et al. (1986), Treiman and Sutton (1992), McSween et al. (1996), McSween and Treiman (1998), Mikouchi et al. (1998), Mikouchi (1981), Barrat et al. (2002), Jambon et al. (2002), Goodrich et al. (2003), Warren et al. (2004), Papike et al. (2009), Usui et al. (2009), Peslier et al. (2010), Hu et al. (2011), Gross et al. (2013), Udry et al. (2016, 2018), Herd et al. (2017), Filiberto et al. (2018), Kizovski et al. (2019), Combs et al. (2019), Hewins et al. (2019), Wenzel et al. (2021), Wu et al. (2023), Benaroya et al. (2024), and this study (NWA 13134).

Figure S12. Backscattered electron image of a complex symplectite zone in merrillite. The orange dot-dashed line indicates the boundary between merrillite and apatite. On the merrillite side of the boundary is a two-phase Fe-oxidephosphate symplectite. This area of interest was chosen because it shows a melt inclusion within the apatite that was offset by a microfault, interpreted to have formed during (or prior to) ejection. This microfault also cross-cuts the symplectite, indicating that the symplectite textures in this sample were not formed during shock metamorphism.