COMPOSITION OF NOBLE GASES IN THE ABEE METEORITE, AND THE ORIGIN OF THE ENSTATITE CHONDRITES.

Persistent Link:
http://hdl.handle.net/10150/184938
Title:
COMPOSITION OF NOBLE GASES IN THE ABEE METEORITE, AND THE ORIGIN OF THE ENSTATITE CHONDRITES.
Author:
WACKER, JOHN FREDERICK.
Issue Date:
1982
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The Abee enstatite chondrite breccia was studied using two methods: measurement of noble gases, and, analyses of the clast size-distribution and the overall texture of Abee. These studies were made in order to understand the formation of the Abee breccia and the formation of the enstatite chondrites. Noble gases were measured as a part of the consortium effort. Noble gases were measured in 17 samples from 10 regions within Abee. Radiogenic ages are 4.5 aeons. Cosmic ray exposure ages average 8 Myr. No evidence for pre-irradiation was found except for a chondrule which may have been neutron pre-irradiated. Abee has at least 2 iodine bearing minerals, both of which are silicate minerals. This suggests that iodine had refractory behavior in the E-chondrites. Two trapped components were found: one having planetary-type elemental and isotopic composition (termed "Kenna-type"), the second with a high argon to xenon ratio (termed "argon-rich") but isotopically similar to the first. Both components appear to be carried in silicate phases, probably enstatite. The Kenna-type component may be carried by small inclusions within silicate minerals. The argon-rich component may have originated from solar wind implantation before accretion of the E-chondrite parent body requiring an inner solar system origin or by noble gas trapping during high temperature mineral condensation requiring high nebular pressures. The clast size-distribution of Abee and 2 other meteorites from the Antarctic meteorite collection (BTNA 78004, ALHA 78113) were measured. The 3 meteorites appear to have formed during single, low energy impacts and that Abee was part of an ejecta blanket which mixed with surrounding regolith. From the textural study, a formation model for the Abee breccia is discussed. The breccia formed during a single impact. Clast metal rims were vapor deposited and partially metamorphosed during impact-generated heating. Greater heating formed dark and metal inclusions. Maximum temperatures were less than 1200 C and heating was brief. Later, the material was disturbed but not brecciated. Abee did not reside on an asteroidal regolith surface for a significant period of time due to the lack of pre-irradiation. This model suggests that the E-chondrite groups formed by metamorphic heating and metal to silicate fractionation on a single parent body.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Meteorites -- History.; Meteoritic hypothesis.; Chondrites (Meteorites)
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Planetary Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Wilkening, Laurel

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleCOMPOSITION OF NOBLE GASES IN THE ABEE METEORITE, AND THE ORIGIN OF THE ENSTATITE CHONDRITES.en_US
dc.creatorWACKER, JOHN FREDERICK.en_US
dc.contributor.authorWACKER, JOHN FREDERICK.en_US
dc.date.issued1982en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe Abee enstatite chondrite breccia was studied using two methods: measurement of noble gases, and, analyses of the clast size-distribution and the overall texture of Abee. These studies were made in order to understand the formation of the Abee breccia and the formation of the enstatite chondrites. Noble gases were measured as a part of the consortium effort. Noble gases were measured in 17 samples from 10 regions within Abee. Radiogenic ages are 4.5 aeons. Cosmic ray exposure ages average 8 Myr. No evidence for pre-irradiation was found except for a chondrule which may have been neutron pre-irradiated. Abee has at least 2 iodine bearing minerals, both of which are silicate minerals. This suggests that iodine had refractory behavior in the E-chondrites. Two trapped components were found: one having planetary-type elemental and isotopic composition (termed "Kenna-type"), the second with a high argon to xenon ratio (termed "argon-rich") but isotopically similar to the first. Both components appear to be carried in silicate phases, probably enstatite. The Kenna-type component may be carried by small inclusions within silicate minerals. The argon-rich component may have originated from solar wind implantation before accretion of the E-chondrite parent body requiring an inner solar system origin or by noble gas trapping during high temperature mineral condensation requiring high nebular pressures. The clast size-distribution of Abee and 2 other meteorites from the Antarctic meteorite collection (BTNA 78004, ALHA 78113) were measured. The 3 meteorites appear to have formed during single, low energy impacts and that Abee was part of an ejecta blanket which mixed with surrounding regolith. From the textural study, a formation model for the Abee breccia is discussed. The breccia formed during a single impact. Clast metal rims were vapor deposited and partially metamorphosed during impact-generated heating. Greater heating formed dark and metal inclusions. Maximum temperatures were less than 1200 C and heating was brief. Later, the material was disturbed but not brecciated. Abee did not reside on an asteroidal regolith surface for a significant period of time due to the lack of pre-irradiation. This model suggests that the E-chondrite groups formed by metamorphic heating and metal to silicate fractionation on a single parent body.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectMeteorites -- History.en_US
dc.subjectMeteoritic hypothesis.en_US
dc.subjectChondrites (Meteorites)en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorWilkening, Laurelen_US
dc.identifier.proquest8303395en_US
dc.identifier.oclc683257738en_US
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