Chemical alteration and REE mobilization in meteorites from hot and cold deserts

Crozaz, G.; Floss, C.; Wadhwa, M.

doi:10.1016/j.gca.2003.08.008

Cited by 185 publications

(198 citation statements)

References 56 publications

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“…While the uranium isotope compositions of the leachate and residue of the second whole-rock fraction of NWA 6291 agree with each other within the uncertainties, the leachate appears to have a slightly but systematically higher 238 U∕ 235 U ratio, most likely due to the addition of isotopically heavy terrestrial U contamination. This work underscores the need to remove terrestrial contamination from meteoritic materials, particularly those collected from hot deserts that tend to be more heavily altered by terrestrial weathering (19). The 238 U∕ 235 U ratio of the NWA 6291 residual material after the 0.5 M HNO 3 acid leach is indistinguishable from that of a separate NWA 6291 whole-rock (which was washed with only a mild acid, 0.05 M HCl, prior to digestion).…”

Section: Discussionmentioning

confidence: 87%

Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System

Brennecka

Wadhwa

2012

Proc. Natl. Acad. Sci. U.S.A.

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156

114

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Events occurring within the first 10 million years of the Solar System's approximately 4.5 billion-year history, such as formation of the first solids, accretion, and differentiation of protoplanetary bodies, have determined the evolutionary course of our Solar System and the planetary bodies within it. The application of high-resolution chronometers based on short-lived radionuclides is critical to our understanding of the temporal sequence of these critical events. However, to map the relative ages from such chronometers onto the absolute time scale, they must be "anchored" to absolute ages of appropriate meteoritic materials using the high-precision lead-lead (Pb-Pb) chronometer. Previously reported Pb-Pb dates of the basaltic angrite meteorites, some of which have been used extensively as time anchors, assumed a constant 238 U∕ 235 U ratio (¼137.88). In this work, we report measurements of 238 U∕ 235 U ratios in several angrites that are distinct from the previously assumed value, resulting in corrections to the Pb-Pb ages of ≥1 million years. There is no resolvable variation in the 238 U∕ 235 U ratio among the angrite bulk samples or mineral separates, suggesting homogeneity in the U isotopic composition of the angrite parent body. Based on these measurements, we recalculated the Pb-Pb age for the commonly used anchor, the D'Orbigny angrite, to be 4563.37 AE 0.25 Ma. An adjustment to the Pb-Pb age of a time anchor (such as D'Orbigny) requires a corresponding correction to the "model ages" of all materials dated using that anchor and a shortlived chronometer. This, in turn, has consequences for accurately defining the absolute timeline of early Solar System events.anchor | geochronology T he time from the formation of the first solids in the Solar System to the accretion and differentiation of protoplanetary embryos is less than approximately 10 million years (Ma) (ref. 1 and references therein), and these events have determined the evolutionary course of our Solar System and the planetary bodies within it. Knowledge of the precise timing of events during this period is critical to a broader understanding of how star systems and planetary bodies form and evolve. As such, precise and accurate geochronology, allowing the resolution of events occurring within this critical approximately 10 Ma interval, is required to understand this earliest sequence of events in the Solar System. A very limited number of chronometers can provide the sub-Ma precision necessary to resolve early Solar System events. These include the long-lived lead-lead (Pb-Pb) chronometer, and the short-lived chronometers such as 26 Al-26 Mg (t 1∕2 approx. 0.72 Ma), 53 Mn-53 Cr (t 1∕2 approx. 3.7 Ma), and 182 Hf-182 W (t 1∕2 approx. 9 Ma). The Pb-Pb chronometer is based on two radioactive isotopes of uranium, utilizing the distinct decay schemes of 235 U → 207 Pb (t 1∕2 approx. 704 Ma) and 238 U → 206 Pb (t 1∕2 approx. 4.47 Ga) to calculate an absolute age of the sample. The short-lived or extinct radionuclide chronometers have parent isotopes ...

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Section: Discussionmentioning

confidence: 87%

Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System

Brennecka

Wadhwa

2012

Proc. Natl. Acad. Sci. U.S.A.

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156

114

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“…There is no petrographic evidence for terrestrial weathering of LAP 02205 such as calcite, clay deposits or oxidized mineral rims (Anand et al, 2006;Day et al, 2006). This observation is substantiated by the absence of Ce anomalies in individual mineral phases (Anand et al, 2006), which may result from terrestrial weathering in the Antarctic environment (Crozaz et al, 2003). For detailed petrographic descriptions of the LAP stones see Anand et al (2006), Day et al (2006), Joy et al (2006), Righter et al (2005) and Zeigler et al (2005).…”

Section: Petrology and Geochemistry Of Lap 02205mentioning

confidence: 91%

A Rb–Sr and Sm–Nd isotope geochronology and trace element study of lunar meteorite LaPaz Icefield 02205

Rankenburg

Brandon

Norman

2007

Geochimica et Cosmochimica Acta

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“…It has been previously noted that meteorites from hot and cold deserts are susceptible to terrestrial weathering (Crozaz and Wadhwa 2001;Crozaz et al 2003). Secondary minerals, such as calcite and gypsum, fill pores and fractures within meteorites during prolonged exposure time in deserts.…”

Section: Bulk Compositionmentioning

confidence: 99%

Petrography, mineralogy, and geochemistry of lunar meteorite Sayh al Uhaymir 300

Hsu

Zhang

Bartoschewitz³

et al. 2008

Meteorit & Planetary Scien

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Chemical alteration and REE mobilization in meteorites from hot and cold deserts

Cited by 185 publications

References 56 publications

Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System

Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System

A Rb–Sr and Sm–Nd isotope geochronology and trace element study of lunar meteorite LaPaz Icefield 02205

Petrography, mineralogy, and geochemistry of lunar meteorite Sayh al Uhaymir 300

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