The Formation and Alteration of the Renazzo-Like Carbonaceous Chondrites

Hdl Handle:
http://hdl.handle.net/10150/223379
Title:
The Formation and Alteration of the Renazzo-Like Carbonaceous Chondrites
Author:
Schrader, Devin Lee
Issue Date:
2012
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.
Embargo:
Release after 30-Oct-2012
Abstract:
This study investigates the pre-accretionary formation conditions of individual minerals within chondrules and whole-rock parent asteroid processes from the Renazzo-like carbonaceous (CR) chondrites. It presents a comprehensive work on the whole-rock O-isotope composition, sulfide-bearing opaque minerals, and type-II chondrules within the CR chondrites. Whole-rock O-isotope composition and minerals present in type-II chondrules are found to be related to the degree of parent asteroid aqueous alteration. Primary minerals within chondrules, formed prior to accretion of the CR chondrite parent asteroid, are used to constrain both the environment and the conditions present during chondrule formation.Chondrule formation, as recorded by chondrules in the CR chondrites, took place under dust- and ice-rich conditions relative to solar values. Type-II (FeO-rich) chondrules contain FeO-poor fragments compositionally similar to type-I (FeO-poor) chondrules; the formation of type-II chondrules may have occurred after the formation of type-I chondrules. The dust and ice abundances present during type-II chondrule formation were higher than those of type-I chondrules, although both populations probably exchanged with the same ¹⁶O-poor gas reservoir. Both the oxygen fugacity (fo₂) and sulfur fugacity (fs₂) appear to have increased from type-I to type-II chondrule formation, and between individual type-II chondrules. The increase in fo₂ and fs₂ may be due to the dissipation of H2 in the early Solar System. Gas-solid oxidation/sulfidation of Fe,Ni metal is recorded in both type-I and type-II chondrules. This corrosion occurred either during chondrule cooling after formation, or during chondrule reheating events, and suggests that S was present in the gas phase. After chondrule formation the CR chondrite parent asteroid accreted ¹⁶O-poor ice and experienced variable degrees of aqueous alteration, possibly due to heterogeneity in accreted ice or ammonia abundances and/or differing depth within the asteroid. Individual regions of the asteroid experienced different degrees of brecciation, perhaps a result of impacts, which fragmented chondrules and mixed together material that experienced different degrees of aqueous alteration. This process resulted in the heterogeneous nature of the CR chondrites.These observations constrain the formation conditions of a minor body, the CR chondrite parent asteroid, a remnant from the earliest stages of planet formation.
Type:
text; Electronic Dissertation
Keywords:
gas-solid reaction; oxygen isotope; Renazzo-like carbonaceous chondrite; sulfide; Planetary Sciences; aqueous; chondrule
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Planetary Sciences
Degree Grantor:
University of Arizona
Advisor:
Lauretta, Dante S.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleThe Formation and Alteration of the Renazzo-Like Carbonaceous Chondritesen_US
dc.creatorSchrader, Devin Leeen_US
dc.contributor.authorSchrader, Devin Leeen_US
dc.date.issued2012-
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.releaseRelease after 30-Oct-2012en_US
dc.description.abstractThis study investigates the pre-accretionary formation conditions of individual minerals within chondrules and whole-rock parent asteroid processes from the Renazzo-like carbonaceous (CR) chondrites. It presents a comprehensive work on the whole-rock O-isotope composition, sulfide-bearing opaque minerals, and type-II chondrules within the CR chondrites. Whole-rock O-isotope composition and minerals present in type-II chondrules are found to be related to the degree of parent asteroid aqueous alteration. Primary minerals within chondrules, formed prior to accretion of the CR chondrite parent asteroid, are used to constrain both the environment and the conditions present during chondrule formation.Chondrule formation, as recorded by chondrules in the CR chondrites, took place under dust- and ice-rich conditions relative to solar values. Type-II (FeO-rich) chondrules contain FeO-poor fragments compositionally similar to type-I (FeO-poor) chondrules; the formation of type-II chondrules may have occurred after the formation of type-I chondrules. The dust and ice abundances present during type-II chondrule formation were higher than those of type-I chondrules, although both populations probably exchanged with the same ¹⁶O-poor gas reservoir. Both the oxygen fugacity (fo₂) and sulfur fugacity (fs₂) appear to have increased from type-I to type-II chondrule formation, and between individual type-II chondrules. The increase in fo₂ and fs₂ may be due to the dissipation of H2 in the early Solar System. Gas-solid oxidation/sulfidation of Fe,Ni metal is recorded in both type-I and type-II chondrules. This corrosion occurred either during chondrule cooling after formation, or during chondrule reheating events, and suggests that S was present in the gas phase. After chondrule formation the CR chondrite parent asteroid accreted ¹⁶O-poor ice and experienced variable degrees of aqueous alteration, possibly due to heterogeneity in accreted ice or ammonia abundances and/or differing depth within the asteroid. Individual regions of the asteroid experienced different degrees of brecciation, perhaps a result of impacts, which fragmented chondrules and mixed together material that experienced different degrees of aqueous alteration. This process resulted in the heterogeneous nature of the CR chondrites.These observations constrain the formation conditions of a minor body, the CR chondrite parent asteroid, a remnant from the earliest stages of planet formation.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectgas-solid reactionen_US
dc.subjectoxygen isotopeen_US
dc.subjectRenazzo-like carbonaceous chondriteen_US
dc.subjectsulfideen_US
dc.subjectPlanetary Sciencesen_US
dc.subjectaqueousen_US
dc.subjectchondruleen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorLauretta, Dante S.en_US
dc.contributor.committeememberConnolly, Harold C. Jr.en_US
dc.contributor.committeememberSwindle, Timothy D.en_US
dc.contributor.committeememberGreenberg, Richard J.en_US
dc.contributor.committeememberShirley, Yancy L.en_US
dc.contributor.committeememberHubbard, William B.en_US
dc.contributor.committeememberLauretta, Dante S.en_US
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