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Petrology of the basaltic achondrite meteorites

Citation

Duke, Michael B. (1963) Petrology of the basaltic achondrite meteorites. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:04242012-095648459

Abstract

Mineralogical and textural evidence indicates that the basaltic achondrites originated in one or more magmatic episodes in a variety of cooling environments that resulted in textures ranging from gabbroic to diabasic. Chemical compositional and mineralogical variations are consistent with a common origin for the basaltic achondrites by magmatic differentiation. The characteristics of the mineralogical, major element and trace element variations are similar to those of the Skaergaard intrusion, but the basaltic achondrite magmas started from different compositions and crystallized under much lower partial pressures of oxygen(in the stability field of metallic iron) than did the magmas of the Skaergaard intrusion. The differentiation trends shown by the basaltic achondrites indicate that the starting material had calcic plagioclase and was depleted in alkalis with respect to chondritic meteorites, in which the plagioclase is sodic.

Brecciation is a conspicuous feature of most basaltic achondrites, which can be most satisfactorily subgrouped on the basis of breccia type as brecciated eucrites (monomict breccias), eucrites (unbrecciated), and howardites (polymict breccias). Petrographic evidence suggests that some textural metamorphism and brecciation were produced by shock effects that accompanied impact events on the surface of the parent body. The abundances of basaltic achondrite falls are consistent with a surface-sampling mechanism such as meteorite impact ejection. A preponderance of near-surface samples and the distinct differences between the basaltic achondrites and chondrites suggest that the moon is the probable parent body of the basaltic achondrites.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Geology
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Silver, Leon T.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1963
Record Number:CaltechTHESIS:04242012-095648459
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:04242012-095648459
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6962
Collection:CaltechTHESIS
Deposited By: John Wade
Deposited On:24 Apr 2012 17:49
Last Modified:26 Dec 2012 04:42

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