Crystallization of Baddeleyite in Basaltic Rocks from Mars, and Comparisons with the Earth, Moon, and Vesta

Herd, Christopher D. K.; Moser, D. E.; Tait, K. T.; Darling, James; Shaulis, Barry; McCoy, T. J.

doi:10.1002/9781119227250.ch6

Cited by 9 publications

(28 citation statements)

References 96 publications

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“…(2010) reported generally micron‐sized baddeleyite grains enclosed in or adjacent to late‐stage ilmenite in LAR 06319, similar to observations made in Zagami dark mottled lithology (Herd et al. 2018) and in the less fractionated, baddeleyite‐poor basaltic shergottites examined in this study (NWA 11057, 11073, and 11255). This similarity, combined with the lower ferroan content in late‐stage phases in LAR 06319 compared to basaltic shergottites (Herd et al.…”

Section: Discussionsupporting

confidence: 86%

“…This similarity, combined with the lower ferroan content in late‐stage phases in LAR 06319 compared to basaltic shergottites (Herd et al. 2018), suggests a lower degree of fractional crystallization, which limits baddeleyite formation.…”

Section: Discussionmentioning

confidence: 91%

“…The association of baddeleyite with igneous silica in shergottites without the formation of zircon has been interpreted to reflect metastability in fractionated liquids without the pressure–temperature conditions necessary for zircon crystallization (Herd et al. 2018).…”

Section: Discussionmentioning

confidence: 99%

“…The survey by Herd et al. (2018) found that basaltic shergottites in general contain more abundant baddeleyite compared to olivine‐phyric and poikilitic (formerly termed “lherzolitic”) shergottites. Hence in this study, we focus on basaltic shergottites in order to optimize the sampling size of baddeleyite grains surveyed and to allow for more direct comparison between shergottite samples.…”

Section: Methodsmentioning

confidence: 99%

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Petrographic controls on baddeleyite occurrence in a suite of eight basaltic shergottites

Sheen

Herd

Hamilton

et al. 2021

Meteorit & Planetary Scien

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Baddeleyite (ZrO2) is a common late‐stage accessory mineral in basaltic shergottites and is a robust geochronometer for obtaining igneous crystallization ages via high‐precision in situ SIMS U‐Pb analysis. Amenability to SIMS U‐Pb dating depends in large part on the size and abundance of baddeleyite grains, which are generally surveyed using microbeam methods. We examine the petrography, mineralogy, geochemistry, and baddeleyite distribution in eight basaltic shergottites to identify factors that may be used to predict baddeleyite distribution in unknown samples of Mars. Results suggest that fractional crystallization controls baddeleyite occurrence in shergottites to the first order; samples with pyroxene major element compositions extending beyond the 1‐bar stability boundary generally have higher baddeleyite abundance compared with samples with pyroxene compositions terminating at or before the stability boundary. In samples which display two pyroxene composition trends (high‐Ca and low‐Ca), the largest baddeleyite grains tend to be associated with Fe‐Ti oxides; in samples where pyroxene composition forms a continuous trend extending beyond the 1‐bar stability boundary, the largest baddeleyite grains are typically associated with polymineralic late‐stage pockets. Bulk HFSE content and fO2 do not appear to directly influence baddeleyite distribution. Based on our findings, we propose that pyroxene composition is a useful proxy for assessing baddeleyite abundance and distribution in shergottites and may aid in determining a sample’s feasibility for U‐Pb geochronology prior to conducting detailed surveys for baddeleyite characterization.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Petrographic controls on baddeleyite occurrence in a suite of eight basaltic shergottites

Sheen

Herd

Hamilton

et al. 2021

Meteorit & Planetary Scien

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“…Such side effects are not induced by micro-drill extraction of target phases (e.g. Paquette et al, 2004), but the spatial resolution offered by such an approach is incapable of isolating exceptionally small (< 50 µm) domains, such as meteoritic micro-baddeleyite (Herd et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Highly accurate dating of micrometre-scale baddeleyite domains through combined focused ion beam extraction and U-Pb thermal ionisation mass spectrometry (FIB-TIMS)

White¹,

Tait²,

Kamo³

et al. 2019

Preprint

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Abstract. Baddeleyite is a powerful chronometer of mafic magmatic and meteorite impact processes. High precision and accuracy U-Pb ages can be measured from single grains by isotope dilution thermal ionisation mass spectrometry (ID-TIMS), but this requires destruction of the host rock for highly challenging grain isolation and dissolution. As a result, the technique is rarely applied to precious samples with very limited availability (such as lunar, Martian and asteroidal meteorites and returned samples) or samples containing small baddeleyite grains that cannot readily be isolated by conventional mineral separation techniques. Here, we use focused ion beam (FIB) techniques, utilising both Xe+ plasma and Ga+ ion sources, to liberate baddeleyite subdomains in-situ, allowing their extraction for ID-TIMS dating. We have analysed the U-Pb isotope systematics of domains ranging between 200 um and 10 um in length and 5 ug to 0.1 ug in mass. In total, seven domains of Phalaborwa baddeleyite extracted using a Xe+-pFIB yield a weighted mean 207 Pb/206 Pb age of 2060.1 ± 2.4 Ma (0.12 %; all uncertainties 2 sigma), within uncertainty of reference values. The smallest extracted domain (ca. 10 × 15 times; 10 um) yields an internal 207 Pb/206 Pb uncertainty of ±0.15 %. Comparable levels of precision are achieved using a Ga+-source FIB instrument (±0.20 %), though the slower cutting speed limits potential application to larger grains. While the U-Pb data are between 0.5 and 13.6 % discordant, the results generate a precise upper intercept age in U-Pb concordia space of 2061.1 × 7.4 Ma; (0.72 %). Importantly, the extent of discordance does not correlate with the ratio of material to ion-milled surface area, showing that the FIB extraction does not induce disturbance of U-Pb systematics even the smallest extracted domains. Instead, we confirm the natural U-Pb variation and discordance within the Phalaborwa baddeleyite population observed with other geochronological techniques. Our results demonstrate the FIB-TIMS technique to be a powerful tool for high-accuracy in-situ U-Pb dating, which makes a wide range of targets and processes newly accessible to geochronology.

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Dating martian mafic crust; microstructurally constrained baddeleyite geochronology of enriched shergottites Northwest Africa (NWA) 7257, NWA 8679 and Zagami

Staddon

Darling

Schwarz

et al. 2021

Geochimica et Cosmochimica Acta

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Crystallization of Baddeleyite in Basaltic Rocks from Mars, and Comparisons with the Earth, Moon, and Vesta

Cited by 9 publications

References 96 publications

Petrographic controls on baddeleyite occurrence in a suite of eight basaltic shergottites

Petrographic controls on baddeleyite occurrence in a suite of eight basaltic shergottites

Highly accurate dating of micrometre-scale baddeleyite domains through combined focused ion beam extraction and U-Pb thermal ionisation mass spectrometry (FIB-TIMS)

Dating martian mafic crust; microstructurally constrained baddeleyite geochronology of enriched shergottites Northwest Africa (NWA) 7257, NWA 8679 and Zagami

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