Petrogenesis and Shock Metamorphism of Basaltic Lunar Meteorites Northwest Africa 4734 and 10597

Chen, J.; Jolliff, Bradley L.; Wang, A.; Korotev, R. L.; Wang, K.; Carpenter, P. K.; Chen, H.; Ling, Zongcheng; Fu, Xiaohui; Ni, Yingchun; Cao, Haijun; Huang, Yennun

doi:10.1029/2019je006084

Cited by 15 publications

(37 citation statements)

References 57 publications

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“…Some grains yielding three Raman peaks with the peak positions (~359,~673, and~998 cm −1 , Figure 2 and Table 1) similar to pyroxene, whereas peak widths greater than that of typical crystalline pyroxene, are likely to be tissintite, which was also found in another lunar meteorite (e.g., NWA 4734). [44] The En (100 × Mg/(Mg + Fe + Ca)) and Wo (100 × Ca/(Mg + Fe + Ca)) compositional distribution of pyroxenes in the quadrilateral was obtained using diagnostic Raman peak positions. [40,45] Olivine in NWA 4884 occurs as euhedral/subhedral phenocrysts (~100 μm) or tiny grains in fine-grained matrix.…”

Section: Major Mineralsmentioning

confidence: 99%

Raman and infrared spectroscopic perspectives of lunar meteorite Northwest Africa 4884

Cao

Chen

et al. 2019

J Raman Spectroscopy

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We conducted comprehensive Raman and Fourier transform infrared (FTIR) spectroscopic studies on the whole rock and lithic clasts of Northwest Africa (NWA) 4884 to constrain its igneous mineralogy and metamorphic characteristics. NWA 4884 is composed of mostly clinopyroxene (25.8 vol.%), pigeonite (16.6 vol.%), plagioclase (26.6 vol.%), maskelynite (8.1 vol.%), olivine (20.7 vol.%), minor tridymite (1.0 vol.%), quartz (0.2 vol.%), and ilmenite (0.5 vol.%). Lithic clasts contain mafic rocks including plutonic ultramafic cumulate, olivine gabbro, mare basalt, and feldspathic rocks including noritic anorthosite and impact melt breccia. Raman and FTIR spectroscopic analyses are combined to investigate the shock history of this breccia and revealed that NWA 4884 is highly shocked (17.9–48.1 GPa recorded in plagioclase). The combination of bulk composition and remote sensing data provides possible source regions of NWA 4884: the southern Lacus Veris (20.5°S, 84.5°W) within Orientale basin and the western mare unit (45.3°N, 151.3°E) of Campbell Crater. The pairing relationship among NWA 4884, Yamato 793274, Queen Alexandra Range 94281, and NWA 7611 is supported by their petrographic, mineral, and compositional similarities. Our work demonstrates the potential of Raman and FTIR spectroscopies to shed light on igneous petrology and the bombardment history of the Moon.

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Section: Major Mineralsmentioning

confidence: 99%

Raman and infrared spectroscopic perspectives of lunar meteorite Northwest Africa 4884

Cao

Chen

et al. 2019

J Raman Spectroscopy

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“…NWA 032 is launch paired with several unbrecciated mare basaltic meteorites-LAP 02205/ 02224/02226/02436/03632/04841 (hereafter LAPs), NWA 4734, and NWA 10597 (Zeigler et al 2005;Day and Taylor 2007;Hill et al 2009;Wang et al 2012;Chen et al 2019). In this section, we compare previous descriptions of shock in NWA 032 to our study.…”

Section: Revised Shock Conditions For Nwa 032 and Paired Basaltic Metmentioning

confidence: 75%

“…In these studies, partial transformation was confirmed by the observation of both optically isotropic and birefringent grains and also by texture, where crystalline igneous plagioclase is highly fractured in contrast to maskelynite which appears as smooth (unfractured) pseudomorphs after precursor plagioclase (Zeigler et al 2005). Plagioclase compositions are highly calcic, overlapping with that of NWA 032, in the range of An 78-90 Ab 10-18 Or 0-4 (NWA 4734;Chen et al 2019), An 78-89 Ab 10-17 Or 0-5 (NWA 10597;Chen et al 2019), and An 84-89 Ab 11-15 Or 0-1 (LAPs;Zeigler et al 2005). Partial amorphization of such calcic plagioclase requires shock pressures on the order of 22-27 GPa (Fig.…”

Section: Revised Shock Conditions For Nwa 032 and Paired Basaltic Metmentioning

confidence: 75%

“…NWA 032 is an unbrecciated sample of one of the lunar maria that was found in the Sahara Desert in 1999 (Fagan et al 2002). This meteorite is geochemically and petrographically distinct from samples returned by Apollo and Luna missions (Fagan et al 2002;Zeigler et al 2005;Borg et al 2009) but shares affinities in terms of bulk composition, mineralogy, and ages with the LaPaz Icefield meteorites (LAPs) 02205/02224/0226/02436/03632/04841, NWA 479, NWA 4734, and NWA 10597 (Fagan et al 2002;Zeigler et al 2005;Anand et al 2006;Day and Taylor 2007;Fernandes et al 2009;Hill et al 2009;Chen et al 2019). These affinities suggest source crater pairing and that these meteorites are separate samples of the same basalt flow.…”

Section: Age and Petrogenesis Of Nwa 032mentioning

confidence: 99%

“…Likewise, the texture of NWA 4734 and NWA 10597 is subophitic, with mm-size feldspar laths partially enclosing pyroxene and olivine phenocrysts (Chen et al 2019). Plagioclase in NWA 4734 and NWA 10597 has been partially transformed to maskelynite, confirmed by both grains of optically isotropic and birefringent plagioclase in thin section, and by acquired Raman spectra which showed both broad humps near 513, 573, and 988 cm −1 (maskelynite) and sharp peaks at 485, 505, and 972 cm −1 (crystalline bytownite; Chen et al [2019] Supplementary data). Likewise, plagioclase in LAPs has been partially transformed to maskelynite (Zeigler et al 2005;Hill et al 2009).…”

Section: Revised Shock Conditions For Nwa 032 and Paired Basaltic Metmentioning

confidence: 99%

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A revised shock history for the youngest unbrecciated lunar basalt—Northwest Africa 032 and paired meteorites

Mijajlovic

Xue

Walton

2020

Meteorit & Planetary Scien

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Northwest Africa (NWA) 032 is an unbrecciated porphyritic basalt found in the Moroccan desert in 1999. Constituent igneous minerals-olivine, pyroxene, and plagioclase-exhibit shock deformation and transformation effects. NWA 032 is among the youngest radiometrically dated sample from the Moon, with concordant Sm-Nd and Rb-Sr ages of 2.947 AE 0.016 Ga and 2.931 AE 0.092, respectively, representing the timing of igneous crystallization. We present the first comprehensive study of shock metamorphism in NWA 032, with a focus on the structural state of fine-grained plagioclase feldspar, shock deformation in olivine and pyroxene, and the microtexture and mineralogy of shock melts. Micro-Raman spectroscopy, optical properties, and electron imaging confirm that plagioclase in this meteorite has been shock amorphized, which, for calcic plagioclase (An 80-90), requires shock pressures on the order of~25-27 GPa. Shock pressures in this range are accompanied by a postshock temperature increase <200°C. Shock deformation in olivine and pyroxene phenocrysts comprises undulose extinction to weak mosaicism, irregular fractures, polysynthetic mechanical twinning in pyroxene, and development of planar fractures in olivine. The shock effects in mafic minerals constrain the upper limit of shock in NWA 032 to have been <30 GPa. Shock melt in NWA 032 has quenched to glass of basaltic composition, representing localized in situ melting of igneous minerals by shearing along lithological boundaries to form shock veins and shock impedance contrasts to form isolated pockets of shock melt. These melts quench-crystallized olivine and pyroxene during the pressure release (<14 GPa). Using recent experimental data on shock amorphization of feldspars, coupled with constraints on the formation of metastable minerals associated with shock melt, we have revised the shock pressure experienced by paired meteorites NWA 10597, NWA 4734, and LaPaz Icefield 02205/02224/0226/02436/03632/04841. These largely unbrecciated, basaltic meteorites experienced an equilibration shock pressure on the order of 22-25 GPa, constrained by partial amorphization of precursor igneous bytownite. Our results are consistent with crater pairing and ejection in a single impact cratering event.

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Automatic Bulk Composition Analysis of Lunar Basalts: Novel Big-Data Algorithm for Energy-Dispersive X-ray Spectroscopy

Yuan

Huang

Chen

et al. 2023

ACS Earth Space Chem.

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The bulk composition of lunar basaltic meteorites and clasts provides crucial information for understanding their petrogenesis and thus lunar thermal evolution. Meanwhile, the basalt type of Chang’E-5 based on the bulk TiO2 contents remains debatable. Modal recombination based on mineral volume fraction, densities, and average compositions is currently the most popular method to determine the bulk composition of lunar samples. Yet, the latter two parameters can be biased markedly by ubiquitous compositional variations in pyroxene, olivine, and plagioclase. To rectify these issues and provide more accurate classifications, this study devises a novel big-data algorithm that analyzes maps of energy-dispersive X-ray spectroscopy (EDS) data of lunar basalts. The algorithm starts by labeling each point through a newly devised mineral classifier, then uses the mean of all points per mineral to represent average composition, and finally recalculates the true density per mineral to replace standard density. The accuracy of this mineral classifier is demonstrated by tests on a database of lunar minerals. The accuracy and precision of EDS mapping were verified by test analysis on certified reference minerals. Measurements on a lunar meteorite sample with a known composition, NWA 4734, are comparable to those measured using inductively coupled plasma optical emission spectrometry and confirm the reliability of the bulk composition algorithm. To demonstrate its utility for comprehensive understanding of petrographic features, the high-efficiency algorithm was applied to Chang’E-5 basalts. The results reveal that these basalts are characterized by low-Ti and low-Mg features, thus distinct from previous Apollo and Luna samples.

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Petrogenesis and Shock Metamorphism of Basaltic Lunar Meteorites Northwest Africa 4734 and 10597

Cited by 15 publications

References 57 publications

Raman and infrared spectroscopic perspectives of lunar meteorite Northwest Africa 4884

Raman and infrared spectroscopic perspectives of lunar meteorite Northwest Africa 4884

A revised shock history for the youngest unbrecciated lunar basalt—Northwest Africa 032 and paired meteorites

Automatic Bulk Composition Analysis of Lunar Basalts: Novel Big-Data Algorithm for Energy-Dispersive X-ray Spectroscopy

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