Validity of the Apatite/Merrillite Relationship in Evaluating the Water Content in the Martian Mantle: Implications from Shergottite Northwest Africa (NWA) 2975

Słaby, Ewa; Förster, Hans‐Jürgen; Wirth, Richard; Wudarska, Alicja; Birski, Łukasz; Moszumańska, Izabela

doi:10.3390/geosciences7040099

Cited by 8 publications

(10 citation statements)

References 64 publications

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“…Originating in the secondary processes, apatite (population III) is Cl-free fluorapatite (Figure 6h). Similar parallel-oriented stacks of fluorapatite in cracks were found in the shergottites of NWA 2975 [63]. This indicates the lack of Cl in the last crystallization stage and can be considered a strong argument for the crystallization of secondary fluorapatite because of the exsolution and degassing of Cl-rich fluids [63].…”

Section: Population Iii: Fluorapatitesupporting

confidence: 59%

Apatite from NWA 10153 and NWA 10645—The Key to Deciphering Magmatic and Fluid Evolution History in Nakhlites

et al. 2019

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Apatites from Martian nakhlites NWA 10153 and NWA 10645 were used to obtain insight into their crystallization environment and the subsequent postcrystallization evolution path. The research results acquired using multi-tool analyses show distinctive transformation processes that were not fully completed. The crystallization history of three apatite generations (OH-bearing, Cl-rich fluorapatite as well as OH-poor, F-rich chlorapatite and fluorapatite) were reconstructed using transmission electron microscopy and geochemical analyses. Magmatic OH-bearing, Cl-rich fluorapatite changed its primary composition and evolved toward OH-poor, F-rich chlorapatite because of its interaction with fluids. Degassing of restitic magma causes fluorapatite crystallization, which shows a strong structural affinity for the last episode of system evolution. In addition to the three apatite generations, a fourth amorphous phase of calcium phosphate has been identified with Raman spectroscopy. This amorphous phase may be considered a transition phase between magmatic and hydrothermal phases. It may give insight into the dissolution process of magmatic phosphates, help in processing reconstruction, and allow to decipher mineral interactions with hydrothermal fluids.

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Section: Population Iii: Fluorapatitesupporting

confidence: 59%

Apatite from NWA 10153 and NWA 10645—The Key to Deciphering Magmatic and Fluid Evolution History in Nakhlites

et al. 2019

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“…In summary, while we show that merrillite crystals in NWA 6963 formed magmatically, metasomatism of merrillite might have formed associated Cl-apatite regions within merrillite (Słaby et al, 2017). We observe no tell-tale whitlockite peak in our merrillite spectra, thus, should further hydrothermal alteration have affected merrillite grains in NWA 6963, this was limited to the formation of Cl-apatite and no extensive, fluidinduced hydrothermal alteration affected most of the merrillite (Shearer et al, 2015) or shock-induced dehydrogenation from whitlockite to merrillite removed any other signs of hydrous alteration of merrillite (Adcock et al, 2017).…”

Section: Formationmentioning

confidence: 61%

“…Hence, a shock event could have erased any sign of whitlockite, and merrillite in shergottites could originally indeed have been whitlockite that formed either directly from the magma or from hydrous alteration of magmatic merrillite. Selin et al (2014) assumed that groundmass apatite in NWA 6963 crystallized from the melt; however, Słaby et al (2017) suggested a late metasomatic event to explain apatite, in particular in Cl-apatite regions associated with merrillite grains in enriched shergottite NWA 2975. It cannot be excluded that such an event could have altered magmatic merrillite into Cl-apatite also in NWA 6963.…”

Section: Formationmentioning

confidence: 99%

“…Merrillite in shergottites formed late during crystallization and occurs in various grain sizes from 10 to some few hundreds of μm (Shearer et al., 2015). It is often found in a textural relationship to apatite and it has been suggested that these associated apatites might be either a product of merrillite alteration, of magmatic origin, or both (Shearer et al., 2015; Słaby et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

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Young magmatism and Si‐rich melts on Mars as documented in the enriched gabbroic shergottite NWA 6963

Lindner

Hezel

Gerdes

et al. 2022

Meteorit & Planetary Scien

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Enriched shergottites contain interstitial Si‐rich mesostasis; however, it is unclear whether such mesostasis is formed by impact or magmatic processes. We use laser ablation multicollector inductively coupled plasma mass spectrometry U–Pb measurements of minerals within the interstitial Si‐rich mesostasis and of merrillite within the coarse‐grained groundmass of Martian‐enriched gabbroic shergottite Northwest Africa (NWA) 6963. The date derived of tranquillityite, Cl‐apatite, baddeleyite, and feldspar from the Si‐rich mesostasis is 172.4 ± 6.1 Ma, and the derived merrillite date is 178.3 ± 10.6 Ma. We conclude, based on textural observation, that merrillite is a late magmatic phase in NWA 6963, that it was not produced by shock, and that its U–Pb‐system was not reset by shock. The indistinguishable dates of the gabbroic merrillite and the minerals within the Si‐rich mesostasis in NWA 6963 indicate that the Si‐rich mesostasis represents a late‐stage differentiated melt produced in the final phase of the magmatic history of the gabbroic rock and not a shock melt. This can likely be transferred to similar Si‐rich mesostases in other enriched shergottites and opens the possibility for investigations of Si‐rich mesostasis in enriched shergottites to access their magmatic evolution. Our results also provide a crystallization age of 174 ± 6 Ma (weighted average) for NWA 6963.

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“…Shock deformation microstructures in apatite described previously include planar fractures (PFs) (Cavosie and Centeno 2014; Sløby et al. 2017; McGregor et al. 2018; see discussion in Montalvo et al.…”

Section: Introductionmentioning

confidence: 99%

High‐resolution microstructural and compositional analyses of shock deformed apatite from the peak ring of the Chicxulub impact crater

Scientists

2020

Meteorit & Planetary Scien

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The mineral apatite, Ca 5 (PO 4) 3 (F,Cl,OH), is a ubiquitous accessory mineral, with its volatile content and isotopic compositions used to interpret the evolution of H 2 O on planetary bodies. During hypervelocity impact, extreme pressures shock target rocks resulting in deformation of minerals; however, relatively few microstructural studies of apatite have been undertaken. Given its widespread distribution in the solar system, it is important to understand how apatite responds to progressive shock metamorphism. Here, we present detailed microstructural analyses of shock deformation in~560 apatite grains throughout~550 m of shocked granitoid rock from the peak ring of the Chicxulub impact structure, Mexico. A combination of high-resolution backscattered electron (BSE) imaging, electron backscatter diffraction mapping, transmission Kikuchi diffraction mapping, and transmission electron microscopy is used to characterize deformation within apatite grains. Systematic, crystallographically controlled deformation bands are present within apatite, consistent with tilt boundaries that contain the (axis) and result from slip in <10 10> (direction) on f1 120g (plane) during shock deformation. Deformation bands contain complex subgrain domains, isolated dislocations, and low-angle boundaries of~1°to 2°. Planar fractures within apatite form conjugate sets that are oriented within either { 2110g, {2 1 10g, { 1 120g, or 11 20 È É. Complementary electron microprobe analyses (EPMA) of a subset of recrystallized and partially recrystallized apatite grains show that there is an apparent change in MgO content in shock-recrystallized apatite compositions. This study shows that the response of apatite to shock deformation can be highly variable, and that application of a combined microstructural and chemical analysis workflow can reveal complex deformation histories in apatite grains, some of which result in changes to crystal structure and composition, which are important for understanding the genesis of apatite in both terrestrial and extraterrestrial environments.

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Validity of the Apatite/Merrillite Relationship in Evaluating the Water Content in the Martian Mantle: Implications from Shergottite Northwest Africa (NWA) 2975

Cited by 8 publications

References 64 publications

Apatite from NWA 10153 and NWA 10645—The Key to Deciphering Magmatic and Fluid Evolution History in Nakhlites

Apatite from NWA 10153 and NWA 10645—The Key to Deciphering Magmatic and Fluid Evolution History in Nakhlites

Young magmatism and Si‐rich melts on Mars as documented in the enriched gabbroic shergottite NWA 6963

High‐resolution microstructural and compositional analyses of shock deformed apatite from the peak ring of the Chicxulub impact crater

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