Solubility and partitioning of noble gases in anorthite, diopside, forsterite, spinel, and synthetic basaltic melts: Implications for the origin and evolution of terrestrial planet atmospheres.

Persistent Link:
http://hdl.handle.net/10150/184935
Title:
Solubility and partitioning of noble gases in anorthite, diopside, forsterite, spinel, and synthetic basaltic melts: Implications for the origin and evolution of terrestrial planet atmospheres.
Author:
Broadhurst, Catherine Leigh.
Issue Date:
1989
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 noble gas abundances and isotopic ratios of the terrestrial planets differ from each other and from the average of chondritic meteorites. These different abundance patterns result from primordial heterogeneities or different degassing histories. Magmatic transport is the only degassing mechanism that can be demonstrated to occur on Venus, Earth, and Mars, and is presently the dominant form of volatile transport to a planet's free surface. An alternative technique was developed to determine the partitioning and solubility of noble gases in mineral/melt systems. Natural end member minerals and synthetic melts known to be in equilibrium were held in separate crucibles in a one bar flowing noble gas atmosphere. Experiments were run 7-18 days at 1300 or 1332°C, in 99.95% Ar or a Ne-Ar-Kr-Xe mix. Gas concentrations were measured by mass spectrometry. The solubility of noble gases in minerals was surprisingly high, and individual samples of a particular mineral composition are distinct in their behavior. The data is consistent with lattice vacancy defect siting. Noble gas solubility in the minerals increases with increasing atomic number; this may be related to polarizability. Noble gas solubilities in melts decrease with increasing atomic number. Solubility is directly proportional to melt molar volume; values overlap the lower end of the range defined for natural basalts. The lower solubilities are related to the higher MgO and CaO concentrations and lower degree of polymerization and Fe³⁺ concentration in synthetic vs. natural melts. Partition coefficient patterns show a clear trend of increasing compatibility with increasing noble gas atomic number, but many individual values are > 1. Calculations show that the terrestrial planet atmospheres cannot have formed from partial melting of a common chondritic source. When results are examined with isotopic constraints and MOR and hot-spot activities, there is no compelling evidence that the Earth is substantially outgassed of its primordial or even its radiogenic volatiles. If volcanic degassing was mostly responsible for the atmospheres, then initial volatile abundances were Mars < Earth < Venus. Alternatively, roughly equal abundances could have been modified by catastrophic processes.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Planets -- Atmospheres; Gases, Rare
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Drake, Micheal

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleSolubility and partitioning of noble gases in anorthite, diopside, forsterite, spinel, and synthetic basaltic melts: Implications for the origin and evolution of terrestrial planet atmospheres.en_US
dc.creatorBroadhurst, Catherine Leigh.en_US
dc.contributor.authorBroadhurst, Catherine Leigh.en_US
dc.date.issued1989en_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 noble gas abundances and isotopic ratios of the terrestrial planets differ from each other and from the average of chondritic meteorites. These different abundance patterns result from primordial heterogeneities or different degassing histories. Magmatic transport is the only degassing mechanism that can be demonstrated to occur on Venus, Earth, and Mars, and is presently the dominant form of volatile transport to a planet's free surface. An alternative technique was developed to determine the partitioning and solubility of noble gases in mineral/melt systems. Natural end member minerals and synthetic melts known to be in equilibrium were held in separate crucibles in a one bar flowing noble gas atmosphere. Experiments were run 7-18 days at 1300 or 1332°C, in 99.95% Ar or a Ne-Ar-Kr-Xe mix. Gas concentrations were measured by mass spectrometry. The solubility of noble gases in minerals was surprisingly high, and individual samples of a particular mineral composition are distinct in their behavior. The data is consistent with lattice vacancy defect siting. Noble gas solubility in the minerals increases with increasing atomic number; this may be related to polarizability. Noble gas solubilities in melts decrease with increasing atomic number. Solubility is directly proportional to melt molar volume; values overlap the lower end of the range defined for natural basalts. The lower solubilities are related to the higher MgO and CaO concentrations and lower degree of polymerization and Fe³⁺ concentration in synthetic vs. natural melts. Partition coefficient patterns show a clear trend of increasing compatibility with increasing noble gas atomic number, but many individual values are > 1. Calculations show that the terrestrial planet atmospheres cannot have formed from partial melting of a common chondritic source. When results are examined with isotopic constraints and MOR and hot-spot activities, there is no compelling evidence that the Earth is substantially outgassed of its primordial or even its radiogenic volatiles. If volcanic degassing was mostly responsible for the atmospheres, then initial volatile abundances were Mars < Earth < Venus. Alternatively, roughly equal abundances could have been modified by catastrophic processes.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPlanets -- Atmospheresen_US
dc.subjectGases, Rareen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDrake, Michealen_US
dc.identifier.proquest9014665en_US
dc.identifier.oclc703610149en_US
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