• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 38
  • 2
  • 1
  • Tagged with
  • 42
  • 42
  • 18
  • 9
  • 8
  • 8
  • 6
  • 6
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 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

Some local aspects of the geology, mineragraphy and geochemistry associated with the Edwin shoot, W.A /

Watmuff, I.G. January 1970 (has links) (PDF)
Thesis (B.Sc.(Hons))--University of Adelaide, 1970.
2

Differentiation of silicic segregations in the Ferrar Dolerites, Antarctica a geochemical study.

Zavala, Karina. Unknown Date (has links)
Thesis (Ph.D.)--The Johns Hopkins University, 2006. / (UnM)AAI3213842. Adviser: George W. Fisher. Source: Dissertation Abstracts International, Volume: 67-04, Section: B, page: 1882.
3

Geochemical variations within the Roza Member, Wanapum Basalt, Columbia River Basalt Group: Implications for the magmatic processes affecting continental flood basalts

Martin, Barton Sawyer 01 January 1991 (has links)
Plagioclase phyric lavas of the Roza Member cover approximately 40,000 km$\sp2$ in Oregon and Washington. Field relationships in 85 stratigraphic sections and geochemical analysis of 765 samples indicate that the Roza Member consists of 1 to 4 flow units. Systematic variations in Cr, Nb, Zr, P$\sb2$O$\sb5$, and TiO$\sb2$ allow these flow units to be divided into 6 chemically distinct subtypes. Incompatible element abundances decrease while the Cr concentration and plagioclase phenocryst population increase upward through the Roza succession. Most other elements display only minor variations. Stratigraphic relations between the 6 Roza subtypes are complex. The areal distribution of each subtype reflects the interaction of the constructional topography of older Columbia River basalts, regional structure, geomorphology, and location and timing of activity along the 175-km long linear Roza vent system. The distribution of the chemically defined subtypes within the dikes and vents indicate that only short segments of the vent system were active at any given time. Calculations (assuming a conductive cooling regime--an assumption supported by primary intraflow features and cooling-joint measurements), indicate that decades elapsed between successive Roza eruptions. These temporal constraints are supported by a lack of saprolite horizons between Roza cooling units and an absence of large-scale geochemical variation due to magma reservoir processes, and are consistent with estimates of Columbia River basalt recharge rates. The earliest Wanapum eruptions (the Robinette Mountain and Dodge Basalts, Eckler Mountain Member) were distinctly more mafic than the subsequent "main" Wanapum Frenchman Springs-Roza-Priest Rapids sequence (e.g., Rob. Mtn.: Mg' $\approx$ 61, Nb $\approx$ 4ppm, Cr $\approx$ 137ppm; versus Roza: Mg' $\approx$ 39, Nb $\approx$ 15ppm, Cr $\approx$ 33ppm). The main Wanapum succession is enriched in both the large ion lithophile elements (K, Rb, Ba, Th) and radiogenic isotopes relative to the Eckler Mountain lavas. However, similar incompatible element rations for the Wanapum basalts imply lava derivation from comparable mantle sources. Major and trace element modelling suggest that coupling fractional crystallization of OL + PL + CPX + TiMT ($\approx$5:60:34:1) with periodic eruption of $\approx$10 volume percent of a steady state reservoir, minor ($\approx$3%) assimilation of crust similar to the Wallowa Batholith, and recharge by a Robinette Mountain-like parental magma can generate lavas compositionally similar to the Frenchman Springs-Roza-Priest Rapids sequence.
4

Contamination of massif anorthosite and Precambrian crustal evolution in central Labrador: A combined trace element and strontium, neodymium and lead isotopic study

Hamilton, Michael Andrew 01 January 1993 (has links)
Nain craton tonalites show overall similarities to Uivak gneisses of northern Labrador, but are K$\sb2$O-poor and have variable LIL element contents--ascribed to variable degrees of Late Archean migmatization. Orthogneisses from the southern part of the Nain Province and from the Rae Province in the area studied show the greatest signs of LIL element depletion. Few mafic igneous rocks of Archean or Early Proterozoic age in this area appear to represent primary liquids. Many of these rocks are compositionally alkali basalts, high-Mg tholeiites, basaltic komatiites, or contain appreciable cumulus olivine. Most have nearly chondritic elemental ratios, although a few are more akin to those in modern-day MORB. Fine-grained metasedimentary rocks have geochemical signatures appropriate for their being derived from the quartzofeldspathic orthogneisses. Nd, Sr and Pb isotopic data were obtained on samples of troctolites, norites, anorthosites and plagioclase megacrysts from across the entire central portion of the exposed NPS. Primitive initial Nd and Sr isotopic ratios are preserved in olivine-bearing plutons and in a plagioclase megacryst from the western side of the massif. Significant variation in initial $\varepsilon\sb{\rm Nd}$ occurs across the NPS, from about $-$4 to $-$7 for magmas emplaced into the Rae Province (west), decreasing to $-$8 to $-$15 for magmas intrusive into Nain craton (east) and underscores the role of pre-existing lithosphere in controlling massif anorthosite isotopic compositional variation. This is strongly supported by preliminary Pb isotopic data. Mixing models between an estimated parent magma derived from a depleted source and specific samples of crust from country rock contacts reproduce the observed data, but require 30-60% contamination. A uniform level of most primitive (least contaminated) isotopic anorthosites from the western section and troctolites implies a 'ceiling' of $\varepsilon\sb{\rm Nd} \sim-$3, $\varepsilon\sb{\rm Sr} \sim$ +5 at 1.3 Ga. A model is proposed involving enrichment of a previously depleted lithospheric source at a minimum of 2.0 Ga, which is then inherited by the parental magmas to the anorthosite suite at 1.3 Ga. Magmas then assimilate either Archean or Proterozoic lower crust (depending on location). Calculated assimilation proportions are thereby reduced by approximately 15%. (Abstract shortened by UMI.)
5

Geochemistry of greater than 3900 Ma detrital zircons from Jack Hills, Western Australia

Cavosie, Aaron J. Unknown Date (has links)
Thesis (Ph. D.)--University of Wisconsin - Madison, 2005. / (UnM)AAI3186163. Source: Dissertation Abstracts International, Volume: 66-08, Section: B, page: 4128. Supervisor: John W. Valley.
6

Partial melting of eclogite, Tromso, Norway

Stevenson, James Alexander. Unknown Date (has links)
Thesis (Ph.D.)--Yale University, 2006. / (UMI)AAI3243705. Adviser: Mark Thomas Brandon. Source: Dissertation Abstracts International, Volume: 67-12, Section: B, page: 6968.
7

Late Pliocene-Quaternary history of the northwestern Indian Ocean : an organic geochemistry perspective /

Muzuka, Alfred Nzibavuga Nyarubakula. January 1990 (has links)
Thesis (M.Sc.) -- Memorial University of Newfoundland. / Typescript. Bibliography: leaves 70-84. Also available online.
8

Geology and geochemistry of Juniper Ridge, Horsehead Mountain and Burns Butte : implications for the petrogenesis of silicic magma on the High Lava Plains, southeastern Oregon /

MacLean, James W. January 1994 (has links)
Thesis (M.S.)--Oregon State University, 1994. / Two folded plates in pocket. Typescript (photocopy). Includes bibliographical references (leaves 117-124). Also available on the World Wide Web.
9

Geology, geochemistry, and mineralization of the Liberty Bell Gold Mine area, Alaska /

Yesilyurt, Süleyman. January 1993 (has links)
Thesis (M.S.)--Oregon State University, 1994. / Includes mounted photographs. One folded plate in pocket. Typescript (photocopy). Includes bibliographical references (leaves 181-185). Also available on the World Wide Web.
10

Sequence stratigraphy and chemostratigraphy of the Lower Cambrian Sekwi Formation, Northwest Territories, Canada

Dilliard, Kelly Ann. January 2006 (has links) (PDF)
Thesis (Ph. D.)--Washington State University, May 2006. / Includes bibliographical references (p. 139-155).

Page generated in 0.1102 seconds