Introduction: On line etching is very useful to analyse noble gas components such as 'Q' or the solar wind [1, 2]. A bulk meteorite sample, however, has never been analysed by on line etching in order to characterise its complete noble gas inventory

Baur, H.

Busemann, H.

Wieler, R.

English

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Open Research OnlineThe Open University’s repository of research publicationsand other research outputsOn line etching of bulk EH5 St. Mark’s – Radiogenicand subsolar noble gasesConference or Workshop ItemHow to cite:Busemann, H.; Baur, H. and Wieler, R. (2002). On line etching of bulk EH5 St. Mark’s – Radiogenic andsubsolar noble gases. In: 65th Annual Meteoritical Society Meeting, 21-26 Jul 2002, Los Angeles, California, USA.For guidance on citations see FAQs.c© [not recorded]Version: [not recorded]Link(s) to article on publisher’s website:http://www.lpi.usra.edu/meetings/metsoc2002/pdf/5166.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukON LINE ETCHING OF BULK EH5 ST. MARK’S - RADIOGENIC AND SUBSOLAR NOBLE GASES.  H. Buse-mann1, H. Baur2, and R. Wieler2, 1Physics Institute, University of Bern, Switzerland 2Isotope Geology, ETH Zürich, Switzerland.  Introduction:  On line etching is very useful to analyse noble gas components such as “Q” or the solar wind [1, 2]. A bulk meteor-ite sample, however, has never been analysed by on line etching in order to characterise its complete noble gas inventory. Experiment:  The aim of this ongoing study is to analyse noble gases in a bulk sample of the EH5 chondrite St. Mark’s by on line etching (conc. HF) and to compare the results with data for an acid-resistant residue of this meteorite [3]. The surprising discovery that phase Q contains - besides Q-gas - significant amounts of the subso-lar component (5-7% of the total [4]) allows us to determine the subsolar isotopic (He-Ar) and elemental (He-Xe) composition. The subsolar Kr and Xe isotopic composition, however, is not well de-fined [5]. This experiment should provide such data. Furthermore, if the subsolar gas in the silicates should turn out to be identical to that in phase Q, this would suggest that both carriers trapped subsolar gas from a common fractionated reservoir (e.g. the early active Sun) rather than an originally solar composition [e.g. 6]. 0 1x10-62x10-63x10-64x10-65x10-601x10-112x10-113x10-11regression: r=0.9979Fig. 1 : Radiogenic 129Xe and 40Ar in the first etch steps of bulk EH5 St. Mark'sstep 3: 16h HF vapstep 1: 1h HF vapstep 2: 10hcooled HF vapstep 4: 20h HF vapstep 5:25h HF vap  129Xeexcess [cm3/g]40Arexcess [cm3/g] Results: The first steps (<6% of the expected subsolar gas) show large excesses of radiogenic (rad) 40Ar in addition to terrestrial and little subsolar gas. This agrees with the observation for EH4 Abee that the K-rich minerals in EH4 Abee do not contain trapped Ar [7]. Surprisingly, 40Arrad and 129Xerad correlate perfectly (Fig. 1). the 40Ar/36Ar and 129Xe/132Xe ratios exceed 3000 and 5, respectively. Neon is a mixture of cosmogenic Ne and trapped Ne with  20Ne/22Ne = 10.13±0.08 which suggests the presence of little subsolar Ne. Re-sults of further steps will be discussed at the meeting. One carrier for 40Arrad and 129Xerad:  The K-bearing minerals and the carrier of (inherited?) 129Xerad are more easily soluble than enstatite, the carrier of subsolar gas. The correlated excesses suggest that 40Arrad and 129Xerad reside in a single mineral, e.g. in metal sul-fides such as the HF-soluble K-rich djerfisherite, which has been observed in St. Mark’s [8], or their alteration products. The etching conditions (HF vapor) might help to identify the host mineral of 129Xerad in equilibrated E chondrites which would allow to date them by I-Xe and K-Ar. References:  [1] Busemann H. et al. (2000) Meteorit. Planet. Sci., 35, 949–973. [2] Heber V. S. et al. (2001) AIP Conf. Proc., 598, 387-392. [3] Busemann H. et al. (2002) LPS, XXXIII, #1462 (CD-ROM). [4] Patzer A. et al. (2001) Meteorit. Planet. Sci., 36,  947–961. [5] Ott U. (2002) Rev. Min. Geochem., 46. [6] Okasaki R. et al. (2001), Nature, 412, 795-798. [7] Bogard D. D. et al. (1983) EPSL, 62, 132-146. [8] Fuchs L. H. (1966) Science, 153, 166-167. 65th Annual Meteoritical Society Meeting (2002) 5166.pdf

On line etching of bulk EH5 St. Mark's – Radiogenic and subsolar noble gases

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On line etching of bulk EH5 St. Mark's – Radiogenic and subsolar noble gases

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