^1,2Yuan Li, ²Rajdeep Dasgupta, ²Kyusei Tsuno, ³Brian Monteleone, ³Nobumichi Shimizu
Nature Geoscience (in Press) Link to Article [doi:10.1038/ngeo2801]
¹Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
²Department of Earth Science, Rice University, 6100 Main Street, MS 126, Houston, Texas 77005, USA
³Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA

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¹Giorgio S. Senesi, ²Gioacchino Tempesta, ³Paola Manzari, ²Giovanna Agrosì
Geostandards and Geoanalytical Research (in Press) Link to Article [DOI: 10.1111/ggr.12126]
¹Istituto di Nanotecnologia (NANOTEC) – PLASMI Lab, CNR, Bari, Italy
²Dipartimento di Scienze della Terra e Geoambientali (DiSTeGeo), University of Bari, Bari, Italy
³Istituto Nazionale di Astrofisica, Istituto di Astrofisica e Planetologia Spaziali (INAF-IAPS), Roma, Italy
Published by arrangement with John Wiley & Sons

An innovative approach of double pulse laser-induced breakdown spectroscopy (DP-LIBS) coupled with optical microscopy was applied to the characterisation and quantitative analysis of the Agoudal iron meteorite in bulk sample and in petrographic thin section. Qualitative analysis identified the elements Ca, Co, Fe, Ga, Li and Ni in the thin section and the whole meteorite. Two different methods, calibration-free LIBS and one-point calibration LIBS, were used as complementary methodologies for quantitative LIBS analysis. The elemental composition data obtained by LIBS were in good agreement with the compositional analyses obtained by traditional methods generally applied for the analysis of meteorites, such as ICP-MS and EDS-SEM. Besides the recognised advantages of LIBS over traditional techniques, including versatility, minimal destructivity, lack of waste production, low operating costs, rapidity of analysis, availability of transportable or portable systems, etc., additional advantages of this technique in the analysis of meteorites are precision and accuracy, sensitivity to low atomic number elements such as Li and the capacity to detect and quantify Co contents that cannot be obtained by EDS-SEM.

^1,2Laurette Piani, ²Yves Marrocchi, ³Guy Libourel, ²Laurent Tissandier
Geochimica et Cosmochimica Acta (in Press) Link to Article [http://dx.doi.org/10.1016/j.gca.2016.09.010]
¹Department of Natural History Sciences, Faculty of Science, Hokkaido University, Sapporo, 060-0810, Japan
²CRPG, UMR 7358, CNRS – Université de Lorraine, 54500 Vandoeuvre-lès-Nancy, France
³Laboratoire Lagrange, UMR7293, Université de la Côte d’Azur, CNRS, Observatoire de la Côte d’Azur,F-06304 Nice Cedex 4, France
Copyright Elsevier

The nature and distribution of sulfides within 17 porphyritic chondrules of the Sahara 97096 EH3 enstatite chondrite have been studied by backscattered electron microscopy and electron microprobe in order to investigate the role of gas-melt interactions in the chondrule sulfide formation.

Troilite (FeS) is systematically present and is the most abundant sulfide within the EH3 chondrite chondrules. It is found either poikilitically enclosed in low-Ca pyroxenes or scattered within the glassy mesostasis. Oldhamite (CaS) and niningerite [(Mg,Fe,Mn)S] are present in ≈ 60% of the chondrules studied. While oldhamite is preferentially present in the mesostasis, niningerite associated with silica is generally observed in contact with troilite and low-Ca pyroxene. The Sahara 97096 chondrule mesostases contain high abundances of alkali and volatile elements (average Na2O = 8.7 wt.%, K2O = 0.8 wt.%, Cl = 7000 ppm and S = 3700 ppm) as well as silica (average SiO2 = 63.1 wt.%).

Our data suggest that most of the sulfides found in EH3 chondrite chondrules are magmatic minerals that formed after the dissolution of S from a volatile-rich gaseous environment into the molten chondrules. Troilite formation occurred via sulfur solubility within Fe-poor chondrule melts followed by sulfide saturation, which causes an immiscible iron sulfide liquid to separate from the silicate melt. The FeS saturation started at the same time as or prior to the crystallization of low-Ca pyroxene during the high temperature chondrule forming event(s). Protracted gas-melt interactions under high partial pressures of S and SiO led to the formation of niningerite-silica associations via destabilization of the previously formed FeS and low-Ca pyroxene. We also propose that formation of the oldhamite occurred via the sulfide saturation of Fe-poor chondrule melts at moderate S concentration due to the high degree of polymerization and the high Na-content of the chondrule melts, which allowed the activity of CaO in the melt to be enhanced. Gas-melt interactions thus appear to be a key process that may control the mineralogy of chondrules in the different classes of chondrite.