Earth and Planetary Sciences ETDs

Publication Date

11-2-1979

Abstract

The physical properties (size, shape, mass, density, surface morphology), bulk chemical composition (by nondestructive instrumental neutron activation analysis), texture, and phase compositions (by electron microprobe analysis) have been determined for each of 141 individual chondrules separated from a total of 11 different H-, L-, and LL-group chondritic meteorites of Van Schmus-Wood petrologic types 3 and 4. In addition, physical properties have been determined for 75 other chondrules from the same chondrites. The chondrites studied are comparatively unaltered and unequilibrated and include Tieschitz (H3), Dhajala (H3, 4), Ochansk (H4), Weston (H4), Hallingeberg (L3), Saratov (L4), Tennasilm (L4), Chainpur (LL3), Semarkona (LL3), Hamlet (LL4), and Soko-Banja (LL4). The chemical and mineralogical data presented include bulk chondrule abundances of Na, Mg Al, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, La, Sm, Eu, Yb, Lu, Ir, and Au (with Ti, Hf, and Ta for a few) as well as complete, quantitative compositions of chondrule olivine, pyroxene, mesostasis, and Ni-Fe metal components. The following conclusions have been reached regarding the properties and possible origins of chondrules in unequilibrated H-, L-, and LL­chondrites: (1) The generalized size, shape, mass, density, and surface morphology distributions are individually, to a first approximation, the same in all three chondrite groups although subtle intergroup differences may merit further study. Size and mass distributions are approximately log-normal (peaks at ≤ 1 mm and ≤ 1 mg, respectively), narrowly constrained, and indicative of either unique formation or sorting. (2) Abundances of compound ( ≤ 4 percent) and cratered ( ≤ 10 percent) chondrules lead to a model-dependent inference that collisions occurred between plastic chondrules moving in random directions at an average relative speed of ≤ 104 cm/sec and occupying space at number densities of ≥ 1-100 m-3 while in plastic conditions which persisted for   ̴1-100 seconds. Nonporphyritic chondrules can be interpreted as having evolved at number densities significantly greater than those of porphyritic chondrules. (3) Chondrules are generally enriched in lithophile and depleted in siderophile elements relative to the Orgueil (C1) chondrite and are generally depleted in total Fe relative to Orgueil and to their respective host chondrites. (4) Porphyritic (  ̴85 percent) and nonporphyritic (  ̴15 percent) chondrules seem to constitute two distinctive groups with the porphyritic being generally enriched in refractory and siderophile elements relative to the nonporphyritic. (5) The metal components of "unequilibrated" chondrules appear to contain generally lower bulk Ni contents than those of their host chondrites although no such distinction is apparent for "equilibrated" chondrules. (6) Large compositional heterogeneities in chondrules can be only partly explained by formational fractionations and indicate significant heterogeneity in the precursor materials. (7). Chondrules probably formed by melting of preexisting solid materials rather than by direct condensation from the primitive solar nebula.

Degree Name

Earth and Planetary Sciences

Level of Degree

Doctoral

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Klaus Keil

Second Committee Member

Douglas Gridley Brookins

Third Committee Member

Albert Masakiyo Kudo

Fourth Committee Member

Rodney Charles Ewing

Fifth Committee Member

Wolfgang Eugene Elston

Project Sponsors

A research assistantship funded by National Aeronautics and Space Administration grants NAS 1-11855 and NGL 32-004-064, the SUNOCO, EXXON, ARCO, Cities Services Corporations, the Albuquerque Gem and Mineral Club, and a Research Grant-in-Aid from the UNM chapter of the Research Society of Sigma Xi

Language

English

Document Type

Dissertation

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Included in

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