Calcium-aluminum-rich inclusions with fractionation and unknown nuclear effects (FUN CAIs): I. Mineralogy, petrology, and oxygen isotopic compositions

1Alexander N. Krot,1Kazuhide Nagashima,1,2Gerald J. Wasserburg,1Gary R. Huss,2,3Dimitri Papanastassiou,5Andrew M. Davis,5Ian D. Hutcheon,6Martin Bizzarro
1Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
1The Lunatic Asylum, California Institute of Technology, MC 170-25, Pasadena, CA 91125, USA
1Jet Propulsion Laboratory, Mail Stop 183-335, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
1Glenn Seaborg Institute, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA
1Department of the Geophysical Sciences, Enrico Fermi Institute, and Chicago Center for Cosmochemistry, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637-1433, USA
1Centre for Star and Planet Formation, Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350, Denmark

We present a detailed characterization of the mineralogy, petrology, and oxygen isotopic compositions of twelve FUN CAIs, including C1 and EK1-4-1 from Allende (CV), that were previously shown to have large isotopic fractionation patterns for magnesium and oxygen, and large isotopic anomalies of several elements. The other samples show more modest patterns of isotopic fractionation and have smaller but significant isotopic anomalies. All FUN CAIs studied are coarse-grained igneous inclusions: Type B, forsterite-bearing Type B, compact Type A, and hibonite-rich. Some inclusions consist of two mineralogically distinct lithologies, forsterite-rich and forsterite-free/poor. All the CV FUN CAIs experienced postcrystallization open-system iron-alkali-halogen metasomatic alteration resulting in the formation of secondary minerals commonly observed in non-FUN CAIs from CV chondrites. The CR FUN CAI GG#3 shows no evidence for alteration. In all samples, clear evidence of oxygen isotopic fractionation was found. Most samples were initially 16O-rich. On a three-oxygen isotope diagram, various minerals in each FUN CAI (spinel, forsterite, hibonite, dmisteinbergite, most fassaite grains, and melilite (only in GG#3)), define mass-dependent fractionation lines with a similar slope of ∼0.5. The different inclusions have different Δ17O values ranging from ∼ −25‰ to ∼ −16‰. Melilite and plagioclase in the CV FUN CAIs have 16O-poor compositions (Δ17O ∼ −3‰) and plot near the intercept of the Allende CAI line and the terrestrial fractionation line. We infer that mass-dependent fractionation effects of oxygen isotopes in FUN CAI minerals are due to evaporation during melt crystallization. Differences in Δ17O values of mass-dependent fractionation lines defined by minerals in individual FUN CAIs are inferred to reflect differences in Δ17O values of their precursors. Differences in δ18O values of minerals defining the mass-dependent fractionation lines in several FUN CAIs are consistent with their inferred crystallization sequence, suggesting these minerals crystallized during melt evaporation. In other FUN CAIs, no clear correlation between δ18O values of individual minerals and their inferred crystallization sequence is observed, possibly indicating gas-melt back reaction and oxygen-isotope exchange in a 16O-rich gaseous reservoir. After oxygen-isotope fractionation, some FUN CAIs could have experienced partial melting and gas-melt oxygen-isotope exchange in a 16O-poor gaseous reservoir that resulted in crystallization of 16O-depleted fassaite, melilite and plagioclase. The final oxygen isotopic compositions of melilite and plagioclase in the CV FUN CAIs may have been established on the CV parent asteroid as a result of isotope exchange with a 16O-poor fluid during hydrothermal alteration.
We conclude that FUN CAIs are part of a general family of refractory inclusions showing various degrees of fractionation effects due to evaporative processes superimposed on sampling of isotopically heterogeneous material. These processes have been experienced both by FUN and non-FUN igneous CAIs. Generally, the inclusions identified as FUN show larger isotope fractionation effects than non-FUN CAIs. There is a wide spread in UN isotopic anomalies in a large number of CAIs not exhibiting large fractionation effects in oxygen, magnesium, and silicon. We consider the majority of igneous CAIs to be the result of several stages of thermal processing (evaporation, condensation, and melting) of aggregates of solid precursors composed of incompletely isotopically homogenized materials. The unknown nuclear effects in CAIs are common to both FUN and non-FUN CAIs, and are not a special characteristic of FUN inclusions but represent the spectrum of results from sampling a very heterogeneous medium in the accreting Solar System.

Reference
Krot AN, Nagashima K,Wasserburg GJ, Huss GR, Papanastassiou D, Davis AM, Hutcheon ID, Bizzarro M (2014)
Calcium-aluminum-rich inclusions with fractionation and unknown nuclear effects (FUN CAIs): I. Mineralogy, petrology, and oxygen isotopic compositions. Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2014.09.027]

Copyright Elsevier

Chemistry and petrology of Fe–Ni beads from different types of cosmic spherules: Implication for precursors

1N.G. Rudraswami,1M. Shyam Prasad,2E.V.S.S.K. Babu,2T. Vijaya Kumar
1National Institute of Oceanography (Council of Scientific and Industrial Research), Dona Paula, Goa 403 004, India
2National Geophysical Research Institute, (Council of Scientific and Industrial Research), Hyderabad 500 007, India

Fe–Ni beads are observed to occur in all three (Stony, Glass, Iron) types of cosmic spherules collected from deep sea sediments of the Indian Ocean. Fe–Ni beads in cosmic spherules can provide insights for understanding metal segregation mechanisms and their refractory metal element (RME: Re, Os, W, Ir, Ru, Mo, Pt, Rh including Pd) compositions can help ascertain their precursor meteorites. We measured RME compositions of 55 Fe–Ni beads using LA-ICP-MS in all three basic types of cosmic spherules selected after examining ∼2000 cosmic spherules. The RMEs of Fe–Ni beads provide unique information on formation and differentiation during atmospheric entry. The variability in the concentration of the RMEs depends on the initial mass of the cosmic spherules, volatility, temperature attained and efficiency in metal segregation during entry. The CI chondrite and Os normalized RME compositions of the beads display a pattern that is close to CI chondritic composition. The presence of Pd, a non-refractory metal having condensation temperature similar to Fe, in Fe–Ni beads of all types of cosmic spherules indicates that the heating undergone was below its vaporization temperature. Not all parent bodies lead to the formation of beads, the precursor needs to exceed a certain minimum size and temperature to facilitate the metal to get segregated into beads. The minimum size of a parent particle that could enclose a Fe–Ni bead is estimated to have a size ∼1 mm. This places constraints on the sizes of materials that are ablated during entry, and the accompanying mass loss during entry. Our study further points out that all the three basic types of cosmic spherules have a chondritic origin based on their RME distribution patterns. Only metal-rich carbonaceous chondrites contain the required quantities of metal for the formation of Fe-Ni beads during atmospheric entry and during this process the RMEs are also efficiently segregated into these beads.

Reference
Rudraswami NG, Prasad MS, Babu EVSSK, Kumar TV (2014) Chemistry and petrology of Fe–Ni beads from different types of cosmic spherules: Implication for precursors. Geochimica et Cosmoschimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2014.09.029]

Copyright Elsevier

The distribution of Mg-spinel across the Moon and constraints on crustal origin

1Carle M. Pieters,1Kerri Donaldson Hanna,1Leah Cheek,1Deepak Dhingra,1Tabb Prissel,1Colin Jackson,1Daniel Moriarty,1Stephen Parman,2Lawrence A. Taylor

1Department of Geological Sciences, Brown University, Providence, Rhode Island 02912 U.S.A.
2Planetary Geosciences Institute, University of Tennessee, Knoxville, Tennessee 37996 U.S.A.

A robust assessment is made of the distribution and (spatially resolved) geologic context for the newly identified rock type on the Moon, a Mg-spinel-bearing anorthosite (pink-spinel anorthosite, PSA). Essential criteria for confirmed detection of Mg-spinel using spectroscopic techniques are presented and these criteria are applied to recent data from the Moon Mineralogy Mapper. Altogether, 23 regions containing confirmed exposures of the new Mg-spinel rock type are identified. All exposures are in highly feldspathic terrain and are small—a few hundred meters—but distinct and verifiable, most resulting from multiple measurements. Each confirmed detection is classified according to geologic context along with other lithologies identified in the same locale. Confirmed locations include areas along the inner rings of four mascon basins, knobs within central peaks of a few craters, and dispersed exposures within the terraced walls of several large craters. Unexpected detections of Mg-spinel are also found at a few areas of hypothesized non-mare volcanism. The small Mg-spinel exposures are shown to be global in distribution, but generally associated with areas of thin crust. Confirmation of Mg-spinel exposures as part of the inner ring of four mascon basins indicates this PSA rock type is principally of lower crust origin and predates the basin-forming era.

Reference
Pieters CM, Donaldson Hanna K, Cheek L, Dhingra D, Prissel T, Jackson C, Moriarty D, Parman S, Taylor LA (2014)
The distribution of Mg-spinel across the Moon and constraints on crustal origin. American Mineralogist, October 99, 1893-1910
Link to Article [doi:10.2138/am-2014-4776]

Copyright: The Mineralogical Society of America

Reflectance spectroscopy of plagioclase-dominated mineral mixtures: Implications for characterizing lunar anorthosites remotely

1Leah C. Cheek, 2Carle M. Pieters
1Department of Astronomy, University of Maryland, College Park, Maryland 20742, U.S.A.
2Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, Rhode Island 02906, U.S.A.

Anorthositic rocks dominate the Moon’s upper crust. As remnants of the lunar magma ocean (LMO), small variations in the mineralogy of these rocks may hold key information about the homogeneity of LMO composition and solidification processes. Orbital near-infrared (NIR) sensors are sensitive to mineralogy, but technologic advances have only recently enabled detection of the plagioclase component in crustal rocks based on an absorption band centered near 1250 nm. Anorthosites occupy a unique mineralogic range that is well suited for NIR studies: the highly transparent component, plagioclase, is present in high abundances while the spectrally dominant mafic or oxide minerals are present in only minor abundance. As a result, spectra of anorthosites are more likely than many other rock types to contain visually discernable signatures from more than one mineral component, facilitating their identification and characterization in NIR data.
In support of new NIR measurements for the Moon, we present laboratory spectral analyses of well-controlled plagioclase-dominated mineral mixtures. We focus on the spectral effects of varying mafic and oxide composition and abundance in mixtures with a common plagioclase end-member. The results demonstrate that plagioclase can be a significant contributor to reflectance spectra when strongly absorbing minerals are present in low abundance. We show that the contribution of plagioclase is more pronounced in mixtures with pyroxenes and certain spinels, but more easily masked in mixtures containing small amounts of olivine. Differences in minor mineral composition are clearly expressed in bulk spectra. Modeling of mixtures using a Hapke nonlinear approach accurately estimates mineral abundances in laboratory spectra to within 5 vol% for mixtures with ≥90 vol% plagioclase. Together, these results imply that not only should orbital NIR data sets be able to discern the presence of plagioclase in anorthositic crustal exposures, but also that detailed information about anorthosite mineral assemblages can be reliably accessed in reflectance spectra.

Reference
Cheek LC, Pieters CM (2014) Reflectance spectroscopy of plagioclase-dominated mineral mixtures: Implications for characterizing lunar anorthosites remotely. American Mineralogist, October 99, 1871-1892
Link to Article [doi:10.2138/am-2014-4785]

Copyright: The Mineralogical Society of America

Phosphate-halogen metasomatism of lunar granulite 79215: Impact-induced fractionation of volatiles and incompatible elements

1Allan H. Treiman,2Jeremy W. Boyce,3Juliane Gross,2Yunbin Guan,2John M. Eiler,2Edward M. Stolper
1Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058-1113, U.S.A.
2Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Boulevard, Pasadena, California 91125, U.S.A.
3Department of Earth and Planetary Sciences, American Museum of Natural History, Central Park West at 79th Street, New York, New York 10024, U.S.A.

In the last decade, it has been recognized that the Moon contains significant proportions of volatile elements (H, F, Cl), and that they are transported through the lunar crust and across its surface. Here, we document a significant segment of that volatile cycle in lunar granulite breccia 79215: impact-induced remobilization of volatiles, and vapor-phase transport with extreme elemental fractionation. 79215 contains ~1% volume of fluorapatite, Ca5(PO4)3(F,Cl,OH), in crystals to 1 mm long, which is reflected in its analyzed abundances of F, Cl, and P. The apatite has a molar F/Cl ratio of ~10, and contains only 25 ppm OH and low abundances of the rare earth elements (REE). The chlorine in the apatite is isotopically heavy, at δ37Cl = +32.7 ± 1.6‰. Hydrogen in the apatite is heavy at δD = +1060 ± 180‰; much of that D came from spallogenic nuclear reactions, and the original δD was lower, between +350‰ and +700‰. Unlike other P-rich lunar rocks (e.g., 65015), 79215 lacks abundant K and REE, and other igneous incompatible elements characteristic of the lunar KREEP component. Here, we show that the P and halogens in 79215 were added to an otherwise “normal” granulite by vapor-phase metasomatism, similar to rock alteration by fumarolic exhalations as observed on Earth. The ultimate source of the P and halogens was most likely KREEP, it being the richest reservoir of P on the Moon, and 79215 having H and Cl isotopic compositions consistent with KREEP. A KREEP-rich rock was heated and devolatilized by an impact event. This vapor was fractionated by interaction with solid phases, including merrillite (a volatile-free phosphate mineral), a Fe-Ti oxide, and a Zr-bearing phase. These solids removed REE, Th, Zr, Hf, etc., from the vapor, and allowed the vapor to transport primarily P, F, and Cl, with lesser proportions of Ba and U into 79215. Vapor-deposited crystals of apatite (to 30 μm) are known in some lunar regolith samples, but lunar vapor has not (before this) been implicated in significant mass transfer. It seems unlikely, however, that phosphate-halogen metasomatism is related to the high-Th/Sm abundance ratios of this and other lunar magnesian granulites. The metasomatism of 79215 emphasizes the importance of impact heating in the lunar volatile cycle, both in mobilizing volatile components into vapor and in generating strong elemental fractionations.

Reference
Treiman AH, Boyce JW, Gross J, Guan Y, Eiler JM, Stolper EM (2014) Phosphate-halogen metasomatism of lunar granulite 79215: Impact-induced fractionation of volatiles and incompatible elements. American Mineralogist October 99, 1860-1870
Link to Article [doi:10.2138/am-2014-4822]

Copyright: The Mineralogical Society of America

Spinel-rich lithologies in the lunar highland crust: Linking lunar samples with crystallization experiments and remote sensing

1,3Juliane Gross,2Peter J. Isaacson,3Allan H. Treiman,4Loan Le,3Julia K. Gorman
1Department of Earth and Planetary Sciences, American Museum of Natural History, Central Park West at 79th Street, New York, New York 10024, U.S.A.
2Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology (SOEST), 1680 East-West Road, Post 508B, Honolulu, Hawaii 96822, U.S.A.
3Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, U.S.A.
4Jacobs Technology, JETS, NASA Johnson Space Center Engineering, Technology and Science, 2101 NASA Parkway, Code KR111, Houston, Texas 77058, U.S.A.

Mg-Al spinel is rare in lunar rocks (Apollo and meteorite collections), and occurs mostly in troctolites and troctolitic cataclastites. Recently, a new lunar lithology, rich in spinel and plagioclase, and lacking abundant olivine and pyroxene, was recognized in visible to near-infrared (VNIR) reflectance spectra by the Moon Mineralogy Mapper (M3) instrument on the Chandrayaan-1 spacecraft at the Moscoviense basin. These outcrop-scale areas are inferred to contain 20–30% Mg-Al spinel. Possible explanations for the petrogenesis of spinel-bearing and spinel-rich lithology(s) range from low-pressure near-surface crystallization to a deep-seated origin in the lower lunar crust or upper mantle. Here, we describe 1-bar crystallization experiments conducted on rock compositions rich in olivine and plagioclase that crystallize spinel. This would be equivalent to impact-melting, which is moderately common among lunar plutonic rocks and granulites. To explore possible precursor materials and the maximum amount of spinel that could be crystallized, a lunar troctolitic composition similar to Apollo pink spinel troctolite 65785, and a composition similar to ALHA81005 as analog to the source region of this meteorite have been chosen. The crystallization experiments on the composition of AHLA 81005 did not yield any spinel; experiments on the composition similar to Apollo 65785 crystallized a maximum of ~8 wt% spinel, much less than the suggested 20–30% spinel of the new lithology detected by M3. However, our VNIR spectral reflectance analyses of the experimental run products indicate that the spinel composition of the experimental run products not only appears to be similar to the composition of the spinel lithology detected by M3 (characteristics of the spinel absorption), but also that the modal abundances of coexisting phases (e.g., mafic glass) influence the spectral reflectance properties. Thus, the spinel-rich deposits detected by M3 might not be as spinel-rich as previously thought and could contain as little as 4–5 wt% spinel. However, the effect of space weathering on spinel is unknown and could significantly weaken its 2 μm absorptions. If this occurs, weathered lunar rocks could contain more spinel than a comparison with our unweathered experimental charges would suggest.

Reference
Gross J, Isaacson PJ, Treiman AH, Le L, Gorman JK (2014) Spinel-rich lithologies in the lunar highland crust: Linking lunar samples with crystallization experiments and remote sensing. American Mineralogist, October 99, 1849-1859
Link to Article [doi:10.2138/am-2014-4780]

Copyright: The Mineralogical Society of America

VNIR spectral variability of the igneous stratified Stillwater Complex: A tool to map lunar highlands

1Cristian Carli,2Giovanni Serventi,2Maria Sgavetti
1Istituto di Astrofisica e Planetologia Spaziali-INAF Roma, Via fosso del cavaliere 100, 00133, Rome, Italy
2Dipartimento di Fisica e Scienze della Terra, Macedonio Meloni, Università degli studi di Parma, via Usberti 157/A, 43100, Parma, Italy

Lunar highlands are plagioclase-rich terrains produced by crystal floating in a Magma Ocean system. Lunar samples revealed the presence of anorthositic (plagioclase > 90%) samples from the Highlands, associated to more mafic rocks. Recently, remote sensing data permit mapping those terrains with high spatial and spectral resolution allowing detection of plagioclase and mafic crystal field (C.F.) absorptions.
In this paper we have studied bidirectional spectral characteristics in the visible near-infrared (VNIR) of rocks from the Stillwater Complex, a cumulitic igneous stratified complex, with composition varying from mafic to sialic (e.g., pyroxenite, anorthosite). We investigated both slabs and powders of these rocks to give indication of the spectral variability of rock analogs of lunar crust, from a mineralogical point of view. Samples have been spectrally separated in four main groups considering the different C.F. absorption association, reflectance and spectral shape for both slab and powder spectra. More spectral details can be obtained from the analysis of powder spectra than from the slab spectra.
The composition of rocks can be addressed by studying spectral parameters, such as the position and the intensity of the absorption (e.g., band center and band depth). The analysis of our plagioclase-pyroxene-bearing samples indicates that mafic composition can be clearly obtained for samples characterized by one pyroxene phase, even for few amounts of pyroxene, from powder spectra. On the other hand, slab spectra show clear pyroxene absorptions only for rocks with mafic abundance at least >20%. The intensity of the mafic absorptions of these samples shows a linear trend with respect to the abundance of pyroxenes (orthopyroxene + clinopyroxene, for samples with ferrosilite amount less than ca. 25%). Considering all pyroxene-bearing samples, the band depth of slab spectra are linearly related to the volumetric distribution of ferrous iron in pyroxenes.

Reference
Carli C, Serventi G, Sgavetti M (2014) VNIR spectral variability of the igneous stratified Stillwater Complex: A tool to map lunar highlands. American Mineralogist October 99 1834-1848
Link to Article [doi:10.2138/am-2014-4808]

Copyright: The Mineralogical Society of America

Visible-infrared spectral properties of iron-bearing aluminate spinel under lunar-like redox conditions

1Colin R.M. Jackson et al. (>10)*
1Geological Sciences, Brown University, 324 Brook Street, Providence, Rhode Island 02912, U.S.A.
*Find the extensive, full author and affiliation list on the publishers website

Remote sensing observations have identified aluminate spinel, in the absence of measureable olivine and pyroxene, as a globally distributed component of the lunar crust. Earlier remote sensing observations and returned samples did not indicate the presence of this component, leaving its geologic significance unclear. Here, we report visible to mid-infrared (V-IR) reflectance (300–25 000 nm) and Mössbauer spectra of aluminate spinels, synthesized at lunar-like oxygen fugacity (fO2), that vary systematically in Fe abundance. Reflectance spectra of particulate (6 Fe#. Although the 2000 and 2800 nm bands are assigned to Fe2+IV electronic transitions, spectra of aluminate spinels with excess Al2O3 demonstrate that the strengths of the 1000 nm bands are related to the abundance of Fe2+VI. The abundance of Fe2+VI depends on bulk Fe content as well as factors that control the degree of structural order-disorder, such as cooling rate. Consequently the strength of the 1000 nm bands are useful for constraining the Fe content and cooling rate of remotely sensed spinel. Controlling for cooling rate, particle size, and fO2, we conclude that spinels with >12 Fe# (

Reference
Jackson CRM et al. (2014) Visible-infrared spectral properties of iron-bearing aluminate spinel under lunar-like redox conditions. American Mineralogist October 99, 1893-1910
Link to Article [doi:10.2138/am-2014-4793]

Copyright: The Mineralogical Society of America

The Uranium Isotopic Composition of the Earth and the Solar System

1Alexander Goldmann,2,3Gregory Brennecka,4Janine Noordmann,1Stefan Weyer,2Meenakshi Wadhwa
1Leibniz Universität Hannover, Institut für Mineralogie, Callinstr. 3, 30167 Hannover, Germany
2Arizona State University, School of Earth & Space Exploration, Tempe, AZ 85287, USA
3Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
4Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany

Recent high-precision mass spectrometric studies of the uranium isotopic composition of terrestrial and meteoritic materials have shown significant variation in the 238U/235U ratio, which was previously assumed to be invariant (=137.88). In this study, we have investigated 27 bulk meteorite samples from different meteorite groups and types, including carbonaceous (CM1 and CV3), enstatite (EH4) and ordinary (H-, L-, and LL-) chondrites, as well as a variety of achondrites (angrites, eucrites, and ungrouped) to constrain the distribution of U isotopic heterogeneities and to determine the average 238U/235U for the Solar System.
The investigated bulk meteorites show a range in 238U/235U between 137.711 and 137.891 (1.3 ‰) with the largest variations among ordinary chondrites (OCs). However, the U isotope compositions of 20 of the 27 meteorites analyzed here overlap within analytical uncertainties with the narrow range defined by terrestrial basalts (137.778 – 137.803), which are likely the best representatives for the U isotope composition of the bulk silicate Earth. Furthermore, the average 238U/235U of all investigated meteorite groups overlaps with that of terrestrial basalts (137.795 ± 0.013). The bulk meteorite samples studied here do not show a negative correlation of 238U/235U with Nd/U or Th/U (used as proxies for the Cm/U ratio), as would be expected if radiogenic 235U was generated by the decay of extant 247Cm in the early Solar System. Rather, ordinary chondrites show a positive correlation of 238U/235U with Nd/U and with 1/U.
The following conclusions can be drawn from this study: (1) The Solar System has a broadly homogeneous U isotope composition, and bulk samples of only a limited number of meteorites display detectable U isotope variations; (2) Bulk planetary differentiation has no significant effect on the 238U/235U ratio since the Earth, achondrites, and chondrites have indistinguishable U isotope compositions in average. (3) The cause of U isotopic variation in Solar System materials remains enigmatic; however, both the decay of 247Cm and isotope fractionation are likely responsible for the U isotopic variations observed in CAIs and ordinary chondrites, respectively.
The average 238U/235U of the investigated meteorite groups (including data compiled from the literature) and terrestrial basalts is 137.794 ± 0.027 (at a 95% student’s t confidence level, including all propagated uncertainties) and represents the best estimate for the U isotope composition of the Earth and the Solar System. This value may be used for U-Pb and Pb-Pb dating of Solar System materials, provided the precise U isotope composition of the sample is unknown. Compared to Pb-Pb ages that were determined with the previously assumed value for 238U/235U (137.88), this new value results in an age adjustment of -0.9 Ma.

Reference
Goldmann A, Brennecka G, Noordman J, Weyer S, Wadhwa M (2014) The Uranium Isotopic Composition of the Earth and the Solar System. Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2014.09.008]

Copyright Elsevier

Analysis of ripple or flow-like features in NWA 3118 CV3 meteorite

1,2Kereszturi Akos, 2Ormandi Szivia, 2Jozsa Sandor, 3Szabo Mate, 3Toth Maria
1Research Center for Astronomy and Earth Sciences, Konkoly Astronomical Institute, H-1121 Budapest, Konkoly Thege Miklos 15-17., Hungary
2Eotvos Lorand University, Faculty of Sciences, H-1117 Budapest, Pazmany Peter 1/C, Hungary
3Research Center for Astronomy and Earth Sciences, Institute of Geological and Geochemical Research, H-1112 Budapest, Budaorsi 45., Hungary

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Reference
Akos K, Szivi O, Jozsa Sandor J, Szabo Mate S, Maria T(2014) Analysis of ripple or flow-like features in NWA 3118 CV3 Meteorite. Planetary and Space Science (in Press)
Link to Article [DOI: 10.1016/j.pss.2014.09.011]