Erratum to “Tungsten isotopes in eucrites revisited and the initial Hf/Hf of the solar system based on iron meteorite data” [Earth Planet. Sci. Lett. 219 (2004) 201-207]     

Ghylaine Quitté  Jean-Louis Birck 《Earth and Planetary Science Letters》2004,222(1):331

  相似文献   

60Fe–60Ni systematics in the eucrite parent body: A case study of Bouvante and Juvinas     

Ghylaine Quitté  Christopher Latkoczy  Maria Schönbächler  Alex N. Halliday  Detlef Günther 《Geochimica et cosmochimica acta》2011,75(23):7698-7706

Eucrites are basaltic meteorites that cooled rapidly but are in many instances thermally metamorphosed and impact brecciated. The exact timing of these events remains unclear. In this study, Ni isotopic compositions and Fe/Ni elemental ratios are presented for two non-cumulate eucrites, Bouvante and Juvinas, including mineral separates from the latter. The samples are characterized by variable, well-resolved ⁶⁰Ni-excesses consistent with the former presence of live ⁶⁰Fe (t_1/2 = 2.62 Ma) at the time of eucrite crystallization. A significant fraction of Ni with a terrestrial-like composition appears to be surface correlated. This Ni may be the product of terrestrial contamination or was introduced by a chondritic impactor during brecciation. Altogether, the data provide evidence for a complex and probably multi-stage history of Fe and/or Ni redistribution, which impedes the interpretation of the chronological data.  相似文献   

Stony-iron meteorites: History of the metal phase according to tungsten isotopes     

Ghylaine Quitté  Jean-Louis Birck 《Geochimica et cosmochimica acta》2005,69(5):1321-1332

The global composition of the early solar system is thought to be roughly chondritic in terms of refractory components, and this means that metal and silicate should be present together in early planetesimals. To fully understand the metal-silicate differentiation process within the eucrite parent body (EPB), it is important to try and identify the metal reservoir that is complementary to the silicate part. The isotope 182 of tungsten (W), a siderophile element, is partly formed from the decay of ¹⁸²Hf, and W isotopes are useful for examining metal-silicate segregation. The W isotopic composition expected for the metal that is complementary to eucrites falls in the range of iron meteorites. However, mesosiderites seem to be genetically linked to eucrites based on petrologic and oxygen isotopic similarities. Therefore, we undertook the analysis of the metal phase of these stony-irons. Here we present tungsten isotopic data for mesosiderite and pallasite metal to characterize their parent body (bodies) and to assess possible relationships with eucrites.All stony-iron metals are depleted in radiogenic tungsten by −1.3 to −4.2 ε units, relative to the terrestrial standard, while chondrites, for comparison, are depleted by −1.9 ε units. In addition to W isotopic heterogeneity from one stony-iron to another, there is also W isotopic heterogeneity within individual meteorites. A formation model is tentatively proposed, where we show that mesosiderites, pallasites, and eucrites could possibly come from the same parent body. Several hypotheses are discussed to explain the isotopic heterogeneity: the production of cosmogenic tungsten, the in situ decay of hafnium present in inclusions, and tungsten diffusion processes after metal-silicate mixing during the cooling of the meteorites. The two latter hypotheses provide the best explanation of our data.  相似文献   

High Precision Hf-W Isotopic Measurements in Meteoritic Material Using Negative Thermal Ionisation Mass Spectrometry (NTIMS)   总被引：1，自引：0，他引：1  

Ghylaine Quitté  Jean-Louis Birck  Françoise Capmas  Claude J. Allègre 《Geostandards and Geoanalytical Research》2002,26(2):149-160

This paper presents a two-stage anion-exchange procedure for tungsten extraction, an improved mass spectrometric procedure for tungsten analysis and a simplified chemical separation and TIMS procedure for the determination of Hf concentrations. The chemical separation of tungsten is based on its complexing properties with HF and H₂O₂. The blank level for a sample size of 300 mg is about 80 pg for tungsten. The procedure is designed for the high sensitivity of negative thermal ionisation mass spectrometry (NTIMS) provided by the use of Mg oxide as an emitter on Ir filaments. Tungsten can be readily measured with a high precision in various meteoritical material and especially in small W-poor silicate fractions. Samples containing as little as a few ng g^-1 tungsten can be analysed reliably with this method.  相似文献   

Osmium,tungsten, and chromium isotopes in sediments and in Ni‐rich spinel at the K‐T boundary: Signature of a chondritic impactor     

Ghylaine Quitt  Eric Robin  Sylvain Levasseur  Franoise Capmas  Robert Rocchia  Jean‐Louis Birck  Claude Jean AllGre 《Meteoritics & planetary science》2007,42(9):1567-1580

Abstract— It is now established that a large extraterrestrial object hit the Earth at the end of the Cretaceous period, about 65 Ma ago. We have investigated Re‐Os, Hf‐W, and Mn‐Cr isotope systems in sediments from the Cretaceous and the Paleogene in order to characterize the type of impactor. Within the Cretaceous‐Tertiary (K‐T) boundary layer, extraterrestrial material is mixed with terrestrial material, causing a dilution of the extraterrestrial isotope signature that is difficult to quantify. A phase essentially composed of Ni‐rich spinel, formed in the atmosphere mainly from melted projectile material, is likely to contain the extraterrestrial isotopic signature of the impactor. We show that the analysis of spinel is indeed the best approach to determine the initial isotope composition of the impactor, and that W and Cr isotopes confirm that the projectile was a carbonaceous chondrite.  相似文献