MINERALOGICAL AND PETROLOGICAL ANALYSIS OF LUNAR MARE GABBRO METEORITE SWAYYAH 001. E. Shi1,2, P. K. Carpenter1, B. L. Jolliff1, J. Chen2, A. Wang1, J. H. Tepper3, A. J. Irving4, D. C. Burney5, and C. R. Neal5; 1Department of Earth & Planetary Sciences and McDonnell Center for the Space Sciences, Washington Uni-versity in St. Louis, MO, 63130; School of Space Science and Physics, Institute of Space Sciences, Shandong Univer-sity, Weihai, Shandong, 264209, China. 3Dept. of Geology, University of Puget Sound, Tacoma, WA, USA; 4Dept. of Earth & Space Sciences, University of Washington, Seattle, WA, USA; 5Dept. of Civil & Environmental Engineering & Earth Sciences, University of Notre Dame, IN, USA. (erbinshi@wustl.edu)

Introduction: Swayyah 001 is a new gabbroic lunar

meteorite found in 2018 in the Western Sahara [1]. In this abstract we report on the mineralogy, mineral chem-istry, and bulk composition of this important new mem-ber of the lunar mare meteorites [2-5].

Methods: Swayyah 001 was characterized by elec-tron-probe microanalysis (EPMA) and Raman spectros-copy (532 nm laser) at Washington University in St. Louis (WUSTL), and ICP-OES major element analysis at the University of Puget Sound, and ICP-MS trace el-ement analysis at Notre Dame. X-ray compositional mapping (Fig. 1), backscattered-electron (BSE) imag-ing (Fig. 2) and spot analysis was done using the JEOL JXA-8200 electron microprobe at WUSTL.

Mineralogy and Petrography: The compositional maps reveal a relatively coarse grained (average grain size: 1.5 mm) equigranular gabbro with relatively mag-nesian and ferroan subregions. The texture includes shock effects such as fracturing, micro-fault offsets along fractures, and veins of impact melt. The mineral-ogy of Swayyah 001 includes pyroxene, plagioclase, ol-ivine, minor ilmenite, and accessory troilite, chromite, ulvöspinel, silica polymorphs, tranquillityite, baddeley-ite, and phosphates apatite and merrillite. The major el-ement composition of Swayyah 001 from ICP-OES measurement is compared with the average composition of impact-melt glass veins from EPMA analyses (Table 1). Trace element data also show a REE pattern similar to those of low-Ti lunar mare basalts.

Mineral compositions: Pyroxenes in Swayyah 001 include pigeonite and augite, and exhibit zoning trends with minimal Fe-enrichment (T1b, T2b) and pro-nounced enrichment (T1-4) extending to Fe-rich ferro-augite and ferropigeonite for the two subregions (Fig. 1 and 3). Raman analysis also indicates chemical zoning as a shift to long wavenumbers of the major Raman peaks from the Mg-rich core to Fe rich rim. These re-sults reflect the common trend of Fe-enrichment in the crystallization sequence. Olivine in Swayyah 001 ex-hibits compositional zoning from approximately Fo55 cores to Fo20 rims (Fig. 3) and seen as green to blue color variation in Fig. 1. Five pyroxene compositional groups are indicated by Raman spectra, corresponding to the main compositional clusters in the pyroxene quadrilateral plot (Fig. 3).

The minor elements Ti and Cr, which commonly substitute in pyroxene, provide another proxy for the chemical evolution during crystallization [2]. The vari-ation in pyroxene Ti content as a function of Mg#

Figure 1. RGB X-ray composite of Swayyah 001. Al in red, Mg in green, and Fe in blue. Pyx = pyroxene, Plg = plagioclase, Olv = olivine, Ilm = ilmenite.

Figure 2. BSE image of Swayyah 001 thin section.

Figure 3. Compositions of pyroxene (top) and olivine (be-low) within Swayyah 001 from spot and line traverse EPMA. Dashed arrows indicate core to rim trends.

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(molar Mg/[Mg+Fe]×100) is shown in Fig. 4, where in-creasing Ti before ilmenite saturation is followed by de-clining Ti afterwards. Cr contents in pyroxenes follow a trend of decreasing Cr with decreasing Mg# as Cr is preferentially removed from the melt by early crystal-lizing chromite and pyroxene (Fig. 5).

Both plagioclase (An74-92) and K-feldspar are present (Fig. 6, left). Plagioclase conversion to maskelynite is confirmed by petrographic and Raman analysis (Fig. 7, right). Plagioclase and maskelynite grains are zoned from Ca and Mg-rich cores to Na, K, and Fe-rich rims.

Accessory Minerals: Minor and accessory minerals

in Swayyah 001 include tridymite, silica, glass, ilmen-ite, chromite, ulvöspinel, Fe sulfide, (K,Ba)-feldspar, apatite, merrillite, tranquillityite, baddeleyite, barite, hematite, and calcite, as identified by microprobe or Ra-man examination (Fig. 7). Merrillite is enclosed in K, Si-rich glass and REE peaks were identified by energy-dispersive spectrometry. Apatite was identified by Ra-man analysis with the main peak at 961 cm-1 and water and hydroxyl peaks at 3278.7 and 3488 cm-1 (Fig. 7), respectively.

Table 1. Bulk composition (majors and REE) and im-pact-melt vein average composition in Swayyah 001.

Conclusions:Swayyah 001 adds to a small group of

important unbrecciated lunar mare gabbro meteorites, and exhibits variable Fe-enrichment in mapped subre-gions. We show complementary aspects of EPMA, Ra-man, and bulk chemical analysis to identify the petro-logical evolution during solidification.

Acknowledgments: EBS and JC thank the China Scholarship Council for support for joint-training Ph.D. study at WUSTL. ES, BLJ, PKC, and AW acknowledge support from the McDonnell Center for the Space Sci-ences and Washington University for support of the col-laboration with scientists from Shandong University.

References: [1] Meteoritical Bulletin 108. [2] Va-lencia S. N. et al. (2019) Meteorit. Planet. Sci. 54, 2083-2115. [3] Fagan T. J. et al. (2003) Meteorit. Planet. Sci. 38, 529-554. [4] Jolliff B. L. et al. (2003) Geochim Cos-mochim Acta 67, 4857-4879. [4] Bunch T. E. et al. (2006) LPSXXVII, #1375. [5] North S. N. et al. (2013) LPSXLIV, #3013.

Figure 7. BSE image of a mesostasis region in Swayyah 001 (left). Pyx = pyroxene, Plg = plagioclase, Olv = olivine, Kfs = K-feldspar, Ilm = ilmenite, Gls/mer = glass/ merrillite, Fay = fayalite, Tro = troilite; Raman spectra of minerals identified in Swayyah 001 thin section (right).

Figure 4. Ti contents in Swayyah 001 pyroxene (left: all analyzed grains; right: core to rim traverse), Ilm = Ilmenite.

Figure 5. Cr contents in Swayyah 001 pyroxene (left: all analyzed grains; right: core to rim traverse).

Figure 6. Compositional ternary of plagioclase and maskelynite in Swayyah 001(left); Ternary plot of the Fe-Ti-Cr oxide mineral compositions in Swayyah 001(right).

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