Geochemical investigations to explain iodine-overabundances in Antarctic meteorites

Heumann, Klaus G.; Gall, Martin G.; Weiß, Hans

doi:10.1016/0016-7037(87)90304-8

Cited by 56 publications

(34 citation statements)

References 21 publications

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“…However, these techniques based on N-TIMS of Cl -have high discrimination factor and large filament blank (Magenheim et al, 1994). Their high sensitivity is suitable for Cl qualification by isotope dilution mass spectrometry (Heumann et al, 1987; Shinonaga et al, 1994), but they are not precise enough (uncertainty: 2‰) for isotopic analysis of most geochemical samples. This study showed that TIMS of Cs 2 Cl + was sensitive and precise enough for some purpose.…”

Section: Comparison Of Mass Spectrometric Methodsmentioning

confidence: 99%

Precise measurement of chlorine stable isotopic ratios by thermal ionization mass spectrometry.

2001

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An improved method for chlorine isotopic analysis by thermal ionization mass spectrometry of Cs 2 Cl + has been investigated for precise measurement of 37 Cl/ 35 Cl isotopic ratios for small amount of samples. Chlorine in organic and inorganic samples was recovered as AgCl and converted to CsCl with metallic Mg and Cs-form ion exchange resin. The CsCl (containing 2 µg of Cl) was loaded on a Ta filament together with graphite powder. The 37 Cl/ 35 Cl ratio measurement was carried out using Cs 2 Cl + ions with multi Faraday cup (static mode) for 80-100 min each single run. Replicate analysis of ocean water and laboratory standard (CsCl reagent) yield the in-run precision of 0.1-0.2‰ (2σ m ) for 300-400 ratios and external precision of 0.1-0.2‰ (1σ SD ). This method has been tested on a variety of chemical reagents including metal chlorides, hydrochloric acid and chlorinated organic solvents. It was found that the artificial chlorine compound show large variations of 37 Cl/ 35 Cl ratio (total ranges from -5 to +3‰ relative to standard mean ocean chloride) depending upon manufacturing processes. We suggest that the high sensitivity and precision technique established in this work would allow us to detect small isotopic variations of chlorine in small amounts of natural samples such as terrestrial materials (minerals/rocks, sediments, groundwater, etc, as well as environmental materials), meteorites and other planetary materials.

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Section: Comparison Of Mass Spectrometric Methodsmentioning

confidence: 99%

Precise measurement of chlorine stable isotopic ratios by thermal ionization mass spectrometry.

2001

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“…There is a considerable body of data on F and Cl in rocks, minerals, melts and fluids (Böhkle & Irwin 1992, Carroll & Webster 1994, and references therein). However, data of Br and I in minerals, except for those in halides (e.g., Stoessell & Carpenter 1986, Raup & Hite 1996, are scarce because of analytical difficulties for these elements (e.g., Heumann et al 1987, Boneß et al 1991, Shinonaga et al 1994, O'Reilly & Griffin 2000.…”

Section: Introductionmentioning

confidence: 99%

Bromine in Scapolite-Group Minerals and Sodalite: XRF Microprobe Analysis, Exchange Experiments, and Application to Skarn Deposits

Pan¹,

Dong²

2003

The Canadian Mineralogist

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Application of an X-ray fluorescence (XRF) microprobe for the analysis of single grains (80 to 1,000 m in diameter) of Clrich minerals for Br has been evaluated for fluorapatite, chlorapatite, scapolite-group minerals (marialite and meonite) and sodalite. A calibration curve based on the Br contents in four international reference materials has been confirmed by measurements on Brbearing standard solutions and by agreement with the results of Cl-rich minerals from instrumental neutron-activation analyses. Absolute errors associated with individual XRF microprobe analyses (i.e., counting statistics alone) are less than 5%, and the calculated limit of detection in the analysis of single mineral grains is ~1 ppm Br. Matrix and grain-size effects are shown to be negligible. Experiments at 1 atmosphere and 800 to 1000°C yield the following distribution coefficients for Br-Cl exchanges between marialite or sodalite and hydrous NaCl-NaBr melts: K D marialite-melt = 0.97 ± 0.08 and K D sodalite-melt = 0.9 ± 0.1. Therefore, the Cl/Br values in marialite and sodalite closely reflect the halogen proportions of their coexisting melts or fluids. The diffusivity of Br in sodalite follows an Arrhenius relation: D Br = 6.5 ϫ 10 -7 exp(-270 ± 10kJ/mol/RT) m 2 /s, over the temperature range from 800 to 1000°C. D Br in marialite is 1.7 ± 0.3 ϫ 10 -19 m 2 /s at 800°C. The Cl/Br weight ratios of marialite in the Tieshan Fe skarn deposit, China, cluster around 650 ± 40, supporting an origin involving hydrothermal brines from associated evaporites. Scapolitegroup minerals in the exoskarns of the Nickel Plate Au skarn deposit, British Columbia, have Cl/Br from 560 to 570, higher than those (130 to 180) of their counterparts in the endoskarns and vuggy cavities. This variation is attributable to an increased involvement of magmatic water from distal to proximal zones. Similarly, scapolite-group minerals in the Grenville U-Th-Mo-REE pegmatite-skarn-vein deposits vary widely in Cl/Br, from 80 to 380, indicative of mixed sources of hydrothermal fluids. This study shows the potential of Br analysis of Cl-rich silicate minerals for constraining the sources and evolution of hydrothermal fluids.Keywords: XRF microprobe, Br, scapolite-group minerals, sodalite, exchange experiments, distribution coefficient, diffusion coefficient, skarn deposits. SOMMAIRENous évaluons l'application d'une microsonde à fluorescence X pour l'analyse de grains isolés (de 80 à 1,000 m de diamètre) pour le Br dans les minéraux porteurs de Cl comme la fluorapatite, la chlorapatite, les minéraux du groupe de la scapolite tels marialite et méionite, et sodalite. Le calibrage a été fait au moyen des teneurs en brome de quatre étalons internationaux, et a été confirmé avec des résultats obtenus pour des solutions standards contenant du Br et des minéraux riches en Cl analysés par activation neutronique instrumentale. Les erreurs absolues associées à une seule analyse par microsonde à fluorescence X, dues aux seules erreurs de comptage, sont inférieures à 5%, et le ...

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“…Meteorites spend most of their terrestrial lives below the surface of the ice sheet, where they are shielded from the extreme conditions, temperature fluctuations (Koeberl and Cassidy 1991), and contamination from sea-borne elements (Huemann et al 1987;Kallemeyn et al 1994) that may occur above the surface. On exposure, the internal temperature of the meteorite can rise sufficient to thaw capillary water that may percolate the samples (Schultz 1990).…”

Section: Influence Of the Antarctic Environmentmentioning

confidence: 99%

Molecular and isotopic indicators of alteration in CR chondrites

Pearson

Sephton

Gilmour

2006

Meteoritics &Amp; Planetary Science

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Molecular and isotopic indicators of alteration in CR chondritesRenazzo, Al Rais, and Y-790112 release qualitatively similar pyrolysis products, although there are some variations. Al Rais' macromolecular structure contains substantially higher relative abundances of alkylated and oxidized species and relatively lighter δ 15 N, suggesting that it has endured more extensive aqueous processing than the other CR chondrites. Renazzo appears relatively unprocessed, with a low degree of alkylation, a lack of detectable nitrogen-bearing components, and low methylnaphthalene ratio. EET 87770's low abundance of alkylated species suggests its macromolecular structure may be relatively condensed, with condensation potentially assisted by a period of mild thermal alteration.

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Geochemical investigations to explain iodine-overabundances in Antarctic meteorites

Cited by 56 publications

References 21 publications

Precise measurement of chlorine stable isotopic ratios by thermal ionization mass spectrometry.

Precise measurement of chlorine stable isotopic ratios by thermal ionization mass spectrometry.

Bromine in Scapolite-Group Minerals and Sodalite: XRF Microprobe Analysis, Exchange Experiments, and Application to Skarn Deposits

Molecular and isotopic indicators of alteration in CR chondrites

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