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Introduction Pyroxene and Olivine EPMA Chemistry Mineralogy And 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 University in St. Louis, MO, 63130; 2School of Space Science and Physics, Institute of Space Sciences, Shandong University, 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. [email protected] Introduction Mineralogy and Petrography Swayyah 001 Bulk Chemistry ➢ Swayyah 001 is a lunar mare gabbroic meteorite found in Table 1. Bulk composition, REE contents, EPMA impact-melt vein. 2018 in the Southern Morocco [1]. ➢ Swayyah 001 is one of a relatively small group of unbrecciated (monomict) lunar mare gabbro meteorites. Pyroxene and Olivine EPMA Chemistry b Pyroxene Traverses Raman Spectroscopy: Accessory Minerals Figure 1. BSE image (a) and RGB X-ray composite (b) of Swayyah 001. Swayyah 001 Characteristics c ➢ Coarse grained equigranular gabbro (avg 1.5 mm grain size) Olivine Chemistry Two subregions differing in degree of Fe enrichment; strong pyroxene and olivine compositional zoning. ➢ Mineralogy: Pyroxene, plagioclase, olivine, minor ilmenite. Figure 2. Pyroxene and Olivine Chemistry Accessory: troilite, chromite, ulvöspinel, silica polymorphs, Figure 5. Mesostasis BSE and Accessory Raman Spectra (a) Pyroxene BSE with line traverse T2 from Fe-enriched subregion. tranquillityite, baddeleyite, apatite and merrillite. (Left) BSE of mesostasis region in Swayyah 001; (Right) Raman spectra of (b) Pyroxene quadrilateral with pyx core-rim line traverses. ➢ REE Distribution: similar to low-Ti lunar mare basalt & gabbro. minerals identified in Swayyah 001 thin section. (c) Olivine compositional range Fo55 – Fo20 core to rim. ➢ Shock effects: fracturing, micro-fault offsets, impact-melt veins. ➢ Accessory minerals: tridymite, silica, glass, ilmenite, chromite, ➢ Pyroxene zoning trends: minimal (T1b, T2b) and pronounced ulvöspinel, Fe sulfides, (K, Ba)-feldspar, apatite, merrillite, tranquillityite, (T1-4) Fe-enrichment extending to Fe-rich ferroaugite and Pyroxene Minor Element Zoning Trends and baddeleyite. Single Zoning Profile ferropigeonite for the two subregions. Zoning reflects the common All Data ➢ Alteration minerals: barite, hematite, and calcite. trend at low fO of Fe-enrichment in the crystallization sequence. ➢ Merrillite: in K, Si-rich glass. REE identified by EDS. 2 -1 These trends compare well with lunar meteorite NWA 773 clan [2-5]. ➢ Apatite: Raman main peak at 961 cm , water and hydroxyl peaks at 3278.7 and 3488 cm-1, respectively. Plagioclase and Spinel Chemistry Conclusions Swayyah 001 adds to a small group of important unbrecciated lunar mare gabbro meteorites. It exhibits variable Fe-enrichment in mapped subregions which reflect evolved trapped melt and corresponding zoning of pyroxene and olivine. EPMA, Raman, and bulk chemical analysis reveal the petrological evolution during solidification. Methods ➢ Electron-probe microanalysis (EPMA), X-ray compositional mapping, backscattered-electron (BSE) imaging, and spot analysis and Raman spectroscopy (532 nm laser) at Washington University in St. Louis; ➢ ICP-OES major element analysis at the University of Puget Sound; Figure 3. Plagioclase and Spinel Chemistry ➢ ICP-MS trace element analysis at Notre Dame. (a)Plagioclase and maskelynite compositions in Ab-Or-An ternary; References: [1] Meteoritical Bulletin 108. [2] Valencia S. N. et al. (2019) Meteorit. (b) Spinel compositions in (Fe, Mg, Mn)--Ti-Cr, Al ternary. Figure 4. Pyroxene Minor Element Zoning Trends Planet. Sci. 54, 2083- 2115. [3] Fagan T. J. et al. (2003) Meteorit. Planet. Sci. 38, 529- ➢ Plagioclase (An74-92) zoned from Ca-rich cores to Na, K-rich rims 554. [4] Jolliff B. L. et al. (2003) Geochim Cosmochim Acta 67, 4857-4879. [4] Bunch (Mg/Fe also decreases core to rim in plagioclase). (a and c) Pyroxene Ti and Cr contents (a and c: all analyzed crystals; b T. E. et al. (2006) LPSXXVII, #1375. [5] North S. N. et al. (2013) LPSXLIV, #3013. [6] Plagioclase conversion to maskelynite: confirmed by petrography and d : core to rim traverse), Ilm = Ilmenite. Papike, J. J. (Ed.). (2018). Planetary materials Vol. 36, 5-192-5-194. and Raman analysis. ➢ Inflection point in Ti vs. Fe/[Mg+Fe] interpreted as ilmenite Acknowledgments: EBS and JC thank the China Scholarship Council for support for joint-training Ph.D. study at WUSTL. EBS, BLJ, PKC, and AW acknowledge ➢ K-feldspar present in mesostasis. saturation during crystallization [2]. support from the McDonnell Center for the Space Sciences and Washington ➢ Spinel: compositional evolution from aluminous chromite to ➢ Decreasing trend in Cr vs. Fe/[Mg+Fe] interpreted as Cr removal by University for support of the collaboration with scientists from Shandong chromian ulvöspinel, and then toward ulvöspinel endmember. early crystallizing chromite and pyroxene [2]. University..
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