• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 61
  • 12
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 96
  • 19
  • 16
  • 15
  • 14
  • 12
  • 12
  • 12
  • 11
  • 11
  • 9
  • 8
  • 7
  • 7
  • 7
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Elemental abundances in meteoritic chondrules

Osborn, Thomas Ward, III 28 September 1971 (has links)
High-precision instrumental neutron activation analysis has been used to determine Al, Na, Mn, Sc, Cr, Fe, Co, and Ni in a suite of more than 500 chondrules from 26 distinct meteorites. These meteorite specimens represent the H, L, LL and C chemical classes and most of the petrologic types. In addition radiochemical activation analysis has been used to determine K, Rb and Cs in a suite of chondrules from the LL chemical class. To a limited extent trace element data on individual chondrules were correlated with petrographic observations on the same chondrules. I. In general it was found that the siderophilic elements Fe, Co, Ni and Ir are depleted in chondrules compared to the whole chondrite. The lithophilic elements Na, Mn, Sc, Cr and Al are generally enriched in chondrules compared to the whole chondrite. In contrast to the other lithophilic elements, Rb and Cs are generally depleted in the chondrules. Both major and trace elements may exhibit multimodal population distributions for the chondrules sets. II. Petrographic observations of the same chondrules for which trace element contents were determined by INAA suggest that the trace element distribution may be consistent with the mineral assemblages except for a positive Ir-Al and Al-Sc correlations which occur in many chondrule sets. Correlations between chondrule mass and Al, Na, Sc, Co, Lr and Cu contents were observed for certain chondrule sets. III. Chondrules from the H and LL groups appear to exhibit consistent compositional variations in going from low petrographic grades to high petrographic grades. The variations are observed most readily for an increasing Al-Na correlation coefficients and decreasing Mn-Na correlation coefficients with increasing petrologic types. A decrease in the dispersion of Mn and Na was also observed with increasing petrologic types. Na contents in the chondrules increase as a function of petrologic type. These observations are interpreted as indications of increasing equilibration of the chondrules with their matrices. IV. It appears that there are slight chemical differences between the Vigarano and Ornans subgroups as defined by Van Schmus (1969). This work supports the conclusions of Van Schmus and Wood (1967) and Van Schmus (1969) that the C2 and C3 groups are not generally related to one another by thermal equilibration processes while Karoonda may be a product of thermal equilibration of material similar to the Ornans subgroup. V. The Ni/Co ratio was found to be variable within chondrules from the same meteorite; for example, the range in Ochansk chondrules is from 10 to 60. VI. Theories concerning the origin of chondrules are discussed in the context of the elemental abundances and correlations observed in this study. a. Some chondrules may be produced by volcanism or impact on a homogeneous magma but they are not believed to be the main mechanism of production due to the chondrule inhomogeneity and the Al-Sc and Al-Ir correlations. b. The constrained equilibrium theory appears to be inconsistent with the positive Al-Ir and Al-Sc correlations and with the mass element correlations observed for Cu, Al, Sc and Ir. c. Some chondrules may have been produced by impact onto solid rock but this mechanism does not appear to be able to produce the necessary chemical fractionation observed in some chondrules. d. The chemical data is consistent with the remelting of preexisting dust in the solar nebula. The remelting appears to have occurred during terminal stages of the metal silicate fractionation or by a preferential melting of silicate material. The chondrules produced in any one event were apparently mixed with chondrules from other events and finally incorporated into the parent body. Additional chondrules may have been produced by impact during the terminal stages of accretion. The chemical evidence then suggests that some of the chondrules equilibrated with the matrix material of their parent body. / Graduation date: 1972
2

The meteorites of Ohio /

Kalinowski, Donald David. January 1972 (has links)
Thesis (M.S.)--Ohio State University. / Bibliography: leaves 65-68. Available online via OhioLINK's ETD Center
3

The Chemistry and mineralogy of the meteorites of South Australia and adjacent regions /

Fitzgerald, Michael John. January 1979 (has links) (PDF)
Thesis (Ph.D.) -- University of Adelaide, Dept. of Geology, 1980.
4

EXPERIMENTAL PARTITIONING OF SIDEROPHILE ELEMENTS IN THE SYSTEMS IRON - NICKEL - SULFUR - PHOSPHORUS AND FORSTERITE - ANORTHITE - DIOPSIDE

Malvin, Daniel Joshua, 1959- January 1987 (has links)
Partition coefficients in the Fe-Ni-S-P system measured utilizing "static" equilibration experiments cannot be reconciled with the results of "dynamic" experiments which mimic fractional crystallization. New tests of the "static" experiments demonstrate that they yield reliable equilibrium Ni, P and Ge partition coefficients. Partition coefficients in the Fe-Ni-S-P system are well matched by interpolation between the Fe-Ni-S and Fe-Ni-P subsystems. The crystal/liquid partitioning of Ga and Ge has been measured experimentally between forsterite, diopside, anorthite and spinel and melts in the forsterite-diopside-anorthite system. The coefficients for the exchange of Ga and Al and the exchange of Ge and Si between minerals and melts are within a factor of two of unity. Application of these results to the interpretation of natural basaltic samples demonstrates that Ga/Al and Ge/Si ratios can be used to discriminate between different mantle source regions.
5

The Chemistry and mineralogy of the meteorites of South Australia and adjacent regions

Fitzgerald, Michael John January 1979 (has links)
323 p. : ill., photos., tables, 5 journal reprints in end pocket ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology, 1980
6

The Chemistry and mineralogy of the meteorites of South Australia and adjacent regions

Fitzgerald, Michael John January 1979 (has links)
323 p. : ill., photos., tables, 5 journal reprints in end pocket ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology, 1980
7

An integrated mineralogical, petrologic and isotopic study of ureilites

Smith, Caroline Louise January 2002 (has links)
No description available.
8

The major meteor streams

Almond, M. January 1953 (has links)
No description available.
9

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

WACKER, JOHN FREDERICK. January 1982 (has links)
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.
10

Geochemical investigations of ordinary chondrites, shergottites, and Hawaiian basalts /

Reynolds, Valerie Slater, January 2005 (has links) (PDF)
Thesis (Ph. D.) -- University of Tennessee, Knoxville, 2005. / Vita. Includes bibliographical references (p. 57-76). Also available via World Wide Web.

Page generated in 0.0662 seconds