Arid
DOI10.1016/j.epsl.2015.10.013
A comprehensive study of noble gases and nitrogen in "Hypatia", a diamond-rich pebble from SW Egypt
Avice, Guillaume1; Meier, Matthias M. M.1,2; Marty, Bernard1; Wieler, Rainer2; Kramers, Jan D.3; Langenhorst, Falko4; Cartigny, Pierre5; Maden, Colin2; Zimmermann, Laurent1; Andreoli, Marco A. G.6
通讯作者Avice, Guillaume
来源期刊EARTH AND PLANETARY SCIENCE LETTERS
ISSN0012-821X
EISSN1385-013X
出版年2015
卷号432页码:243-253
英文摘要

This is a follow-up study of a work by Kramers et al. (2013) on a very unusual diamond-rich rock fragment found in the area of south west Egypt in the south-western side of the Libyan Desert Glass strewn field. This pebble, called Hypatia, is composed of almost pure carbon. Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) results reveal that Hypatia is mainly made of defect-rich diamond containing lonsdaleite and multiple deformation bands. These characteristics are compatible with an impact origin on Earth and/or in space. We also analyzed concentrations and isotopic compositions of all five noble gases and nitrogen in several similar to mg sized Hypatia samples. These data confirm the conclusion by Kramers et al. (2013) that Hypatia is extra-terrestrial. The sample is relatively rich in trapped noble gases with an isotopic composition being close to the Q component found in many types of meteorites. Ar-40/Ar-36 ratios in individual steps are as low as 0.4 +/- 0.3. Cosmic-ray produced "cosmogenic" Ne-21 is present in concentrations corresponding to a nominal cosmic-ray exposure (CRE) age of roughly 0.1 Myr if produced in a typical meter-sized meteoroid. Such an atypically low nominal CRE age suggests high shielding in a considerably larger body. In addition to the Xe-Q composition, an excess of radiogenic Xe-129 (from the decay of short-lived radioactive I-129) is observed (Xe-129/Xe-132 = 1.18+/-0.03). Two isotopically distinct N components are present, an isotopically heavy component (delta N-15 similar to +20 parts per thousand) released at low temperatures and a major isotopically light component (delta N-15 similar to-110 parts per thousand) at higher temperatures. This disequilibrium in N suggests that the diamonds in Hypatia were formed in space rather than upon impact on Earth (delta N-15(atm) = 0 parts per thousand). All our data are broadly consistent with concentrations and isotopic compositions of noble gases in at least three different types of carbon-rich meteoritic materials: carbon-rich veins in ureilites, graphite in acapulcoites/lodranites and graphite nodules in iron meteorites. However, Hypatia does not seem to be directly related to any of these materials, but may have sampled a similar cosmochemical reservoir. Our study does not confirm the presence of exotic noble gases (e.g. G component) that led Kramers et al. (2013) to propose that Hypatia is a remnant of a comet nucleus that impacted the Earth. (C) 2015 Elsevier B.V. All rights reserved.


英文关键词meteorites noble gases nitrogen phase Q graphite
类型Article
语种英语
国家France ; Switzerland ; South Africa ; Germany
收录类别SCI-E
WOS记录号WOS:000366345200023
WOS关键词COSMOGENIC NUCLIDES ; ISOTOPIC ABUNDANCES ; IRON METEORITE ; ORGANIC-MATTER ; PHASE-Q ; IMPACT ; COMPONENTS ; GENESIS ; PURIFICATION ; CHONDRITES
WOS类目Geochemistry & Geophysics
WOS研究方向Geochemistry & Geophysics
资源类型期刊论文
条目标识符http://119.78.100.177/qdio/handle/2XILL650/186699
作者单位1.Univ Lorraine, CNRS, CRPG, UMR 7358, F-54501 Vandoeuvre Les Nancy, France;
2.Swiss Fed Inst Technol, Dept Earth Sci, CH-8092 Zurich, Switzerland;
3.Univ Johannesburg, Dept Geol, Johannesburg, South Africa;
4.Univ Jena, Inst Geowissensch, D-07745 Jena, Germany;
5.Univ Paris Diderot, Equipe Geochim Isotopes Stables, Inst Phys Globe Paris, Sorbonne Paris Cite,UMR CNRS 7154, F-75005 Paris, France;
6.Univ Witwatersrand, Sch Geosci, ZA-2050 Johannesburg, South Africa
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GB/T 7714
Avice, Guillaume,Meier, Matthias M. M.,Marty, Bernard,et al. A comprehensive study of noble gases and nitrogen in "Hypatia", a diamond-rich pebble from SW Egypt[J],2015,432:243-253.
APA Avice, Guillaume.,Meier, Matthias M. M..,Marty, Bernard.,Wieler, Rainer.,Kramers, Jan D..,...&Andreoli, Marco A. G..(2015).A comprehensive study of noble gases and nitrogen in "Hypatia", a diamond-rich pebble from SW Egypt.EARTH AND PLANETARY SCIENCE LETTERS,432,243-253.
MLA Avice, Guillaume,et al."A comprehensive study of noble gases and nitrogen in "Hypatia", a diamond-rich pebble from SW Egypt".EARTH AND PLANETARY SCIENCE LETTERS 432(2015):243-253.
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