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FUN with PANURGE: High mass resolution ion microprobe measurements of Mg in Allende inclusions

Huneke, J. C. and Armstrong, J. T. and Wasserburg, G. J. (1983) FUN with PANURGE: High mass resolution ion microprobe measurements of Mg in Allende inclusions. Geochimica et Cosmochimica Acta, 47 (9). pp. 1635-1650. ISSN 0016-7037. doi:10.1016/0016-7037(83)90190-4.

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The performance characteristics of PANURGE, a modified CAMECA IMS3F ion microprobe, have been studied at a mass resolving power of 5000 for the purpose of determining isotopic ratios at a precision level approaching that of counting statistics using beam switching. The techniques used for this type of measurement are described. Using this approach, the isotopic composition of Mg and Si and the atomic ratio of Al/Mg in minerals from the Allende inclusion WA and the Allende FUN inclusion Cl have been measured with the ion microprobe at high mass resolving power. Enrichments in ^(26)Mg of up to 260%. have been found. Mg and Al/Mg measurements on cogenetic spinel inclusions and host plagioclase crystals yield Mg-Al isochrons in excellent agreement with precise mineral isochrons determined by thermal emission mass spectrometry. The measurements confirm the presence of substantial excess (^(26)Mg in WA ^(26)Mg^*/^(27)Al = 5 X 10^(-5)) and its near absence in Cl (^(26)Mg^*/^(27)Al < 4 X 10^(-6)). In WA plagioclase, data for which ^(27)Al/^(24)Mg = 300 to 1000 define a linear array with ^(26)Mg^*/^(27)Al = 3 X 10^5 and with initial ^(26)Mg/^(24)Mg composition 30%. greater than in high Mg phases. This suggests a metamorphic reequilibration of Mg in Allende plagioclase at least 0.6 my after WA formation. There were no variations in detected ^(26)Mg^*/^(27)Al in WA plagioclase associated with concentration of ^(26)Mg^∗ into isolated clusters. We have confirmed by ion probe measurements that the Mg composition in Allende Cl is highly fractionated and is uniform among pyroxene, melilite, plagioclase, spinel crystals and spinel included in melilite and plagioclase crystals. Likewise, the Si composition is mass fractionated and is the same in pyroxene, melilite and plagioclase.

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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 1983 Pergamon Press Ltd. Received March 10, 1983; accepted in revised form June 17, 1983. The authors appreciate the careful efforts of G. Lugmair and E. Zinner in their reviews of this manuscript. We thank D. A. Papanastassiou for many helpful discussions and E. M. Stolper for graciously making his laboratory available to us for the preparation of isotopic standard glasses. The authors would like to thank Joseph Ting and Steven Knapp for substantial contributions to the electronic systems that are intrinsic to PANURGE.* The collaborative efforts of CAMECA staff, and in particular Michel Lepareur, are gratefully acknowledged. We appreciate the efforts by F. Rabelais for providing us with one of his inventions. An early message which indicated some support for this work is warranted as well as acknowledgement of subsequent support from the National Aeronautics and Space Administration Grant No. NGL 05-002-188: "8/24/71-Message from Gil at the Teletype office, from Anthony Calio: Purchase of ion microprobe for use at the California Institute of Technology is acceptable provisional on basis that MSC will periodically evaluate use to assure utilization is in the best interest to NASA. Also stipulate that funding will not exceed $250,000 including all ancillary equipment. MSC Grants Officer has been instructed to modify Grant NGL 05-002-188 accordingly. The guy at the Teletype Office is not sure of the $250,000." Division of Geology and Planetary Sciences Contribution Number 3768 (416).
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NASANGL 05-002-188
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Caltech Division of Geological and Planetary Sciences3768
Lunatic Asylum Lab416
Issue or Number:9
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Official Citation:J.C Huneke, J.T Armstrong, G.J Wasserburg, FUN with PANURGE: High mass resolution ion microprobe measurements of Mg in Allende inclusions, Geochimica et Cosmochimica Acta, Volume 47, Issue 9, September 1983, Pages 1635-1650, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42110
Deposited On:29 Oct 2013 20:12
Last Modified:10 Nov 2021 16:17

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