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The Global ETD Search service is a free service for researchers
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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.
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Geology and structural history of the Butte district, Montana /Houston, Robert Andrew. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2002. / Includes maps in pocket. Typescript (photocopy). Includes bibliographical references (leaves 39-44). Also available online.
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Geology, geochemistry and stable isotope studies of a porphyry-style hydrothermal system, West Silverton district, San Juan Mountains, ColoradoRingrose, C. R. January 1982 (has links)
No description available.
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Petrography, Geochemistry and Geochronology of the Coe Hill Granite, Hastings County, OntarioAtkins, Thomas R. 04 1900 (has links)
<p> A detailed petrographic, geochemical and strontium isotope study of the rocks representing the variations observed across the Coe Hill granite, Grenville Province, southeastern Ontario provides the basis for the determination of the age and possible origin of this pluton. This study also provides insight into the relationships between similar granitoid plutons in the immediate vicinity.</p> <p> The Coe Hill granite is a medium to coarse grained hypidiomorphic to allotriomorphic, leucocratic quartz monzonite with subordinate isolated inclusions of dioritic and gabbroic gneiss. Variations upon this otherwise homogeneous granitoid occur in discordant aplite dykes, assimilating mafic xenoliths and along brecciated contact boundaries.</p> <p> Generally the rocks of this pluton are more basic than the average for similar granitoids in the area (12.4% vs. 6.0% mafics) as observed in both thin section and major element oxide diagrams. Besides this trend major element diagrams have uniform distributions. A Rb-Sr isochron was determined for the rocks of the pluton proper which gave an age representative of the emplacement of these rocks (t = 1063 ± 21 M.a.;
Ri = 0.7040 ± 5). Trace element Rb shows a value similar to the norm for granitoids yet is enriched in comparison to values acquired from similar granitoids in the area (144 ppm vs. 63 ppm).</p> <p> Through a synthesis of the available data, and that which was acquired from this study on the Coe Hill granite, a comparison with the available data on the Loon Lake quartz monzonite can be made. This comparison illustrates a great deal of strikingly similar trends which have been taken to represent a lower crustal, or upper mantle origin, cogenetic relationship between these two granitoids.</p> / Thesis / Bachelor of Science (BSc)
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A lithogeochemical study of northern Sweden and the Kiruna and Malmberget iron-apatite ore depositsLundh, Jon January 2014 (has links)
The iron apatite mineralizations of northern Sweden are mainly situated in supracrustal rocks and are thought to have formed during approximately the same time as the major plutonic suites in northern Sweden. In this thesis the Malmberget iron apatite ore deposit have been compared to the Kiruna iron apatite ore deposit to see whether the role of hydrothermal processes are different between the two ore districts. Also, since it has proven problematic to distinguish between the different mafic and ultramafic members of the major plutonic suites in northern Sweden (i.e. the Haparanda suite (1.94-1.85 Ga), the Perthite-monzonite suite (PMS) (1.87 Ga) and the Edefors suite (1.80-1.79 Ga)), a second goal is to trace the distribution and distinguish between these suites. Major elements, REE and trace elements have been studied along with polished sections from the ores and oxygen isotopes of magnetites from the ore districts to trace the ore formation process and separate between suites. All ore districts display a close similarity in geochemistry between host rocks and magnetites, especially regarding the REE pattern. Oxygen isotopes show that samples from the Kiruna district plot exclusively at positive δ18O-values with the majority of them at values < 1‰. Samples from the Malmberget district display δ18O-values either close to the igenous range or at slightly negative values. However, samples that display very low or negative δ18O-values show signs of either high temperature hydrothermal alteration, oxidation or crustal contamination. The δ18O composition along with textural observations from the polished sections and geochemistry, points towards a magmatic origin for these deposits. No apparent evidence has been found to support a primary ore formation by hydrothermal process in any of the districts studied. Regarding the suites, normalized spider plot patterns of REEs and trace elements served as a basis for subdivision into groups by similarities in key identification parameters. Several patterns are characterized by a pronounced Eu-trough while the middle- to HREEs display a rather flat trend, criteria that are related to rocks from the Haparanda suite, while samples with positive Eu-anomaly (Eu/Eu* > 1) and a nearly flat trend from La to Pr with a marked positive peak at Sr and generally less enriched in LILE, are consistent with the Edefors suite. Also, the Edefors suite generally display low concentrations of both Th and U but are somewhat enriched in Sr with relation to Pr. No distinct geochemical features could help to separate between the Haparanda and the PMS suites.
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Primary Sediment Production from Granitic Rocks in Southeastern ArizonaAcaba, Joseph Michael January 1992 (has links)
Isolated granitic rock bodies (granites, granodiorites, quartz monzonites) in the vicinity of Benson in southeastern Arizona were studied to trace the behavior of rock weathering. Thin sections of fresh granites were examined to characterize the original mineralogy which consisted mainly of quartz, feldspars, and micas. The weathering products show up on the granites as grus and soil profiles as well as down slope in the basin deposits. X -ray diffraction studies of the < 2 micrometers fraction of the weathering products proved illite, smectite, illite-smectite mixed layer, and kaolinite to be the dominant clays; quartz and feldspar also persisted into this size fraction. Silt sized material produced similar results. The quartz monzonite of Texas Canyon afforded a special study of the initial weathering stages of feldspars and micas. In the < 2 micrometers fraction obtained from granitic material placed in an ultra sonic bath, the feldspars weathered to a Na-montmorillinite while biotite weathered to vermiculite.
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A Re-Os Study of Sulfides from the Bagdad Porphyry Cu-Mo Deposit, Northern Arizona, USABarra-Pantoja, Luis Fernando January 2001 (has links)
Use of Re-Os systematics in sulfides from the Bagdad porphyry Cu-Mo deposit provide information on the timing of mineralization and the source of the ore -forming elements. Analyzed samples of pyrite, chalcopyrite and molybdenite mainly from the quartz monzonite and porphyritic quartz monzonite units are characterized by a moderate to strong potassic alteration (secondary biotite and K- feldspar). Rhenium concentrations in molybdenite are between 330 and 730 ppm. Two molybdenite samples from the quartz monzonite and porphyritic quartz monzonite provide a Re-Os isotope age of 71.7 ± 0.3 Ma. A third sample from a molybdenite vein in Precambrian rocks yields an age of 75.8 ± 0.4 Ma. These molybdenite ages support previous suggestions of two mineralization episodes in the Bagdad deposit. An early event at 76 Ma and a later episode at 72 Ma. Pyrite Os and Re concentrations range between 0.008-0.016 and 3.9-6.8 ppb, respectively. Chalcopyrite contains a wide range of Os (6 to 91 ppt) and Re (1.7 to 69 ppb) concentrations and variable ¹⁸⁷Os/¹⁸⁸Os ratios that range between 0.13 to 22.27. This variability in the chalcopyrite data may be attributed to different copper sources, one of them the Proterozoic volcanic massive sulfides in the district, or to alteration and remobilization of Re and Os. Analyses from two pyrite samples yield an eight point isochron with an age of 77 ± 15 Ma and an initial ¹⁸⁷Os/¹⁸⁸Os ratio of 2.12. This pyrite Re-Os isochron age is in good agreement with the molybdenite ages. We interpret the highly radiogenic initial 1870s/188Os as an indication that the source of Os and, by inference, the ore-forming elements for the Bagdad deposit, was mainly the crust. This conclusion agrees with previous Pb and Nd isotope studies and supports the notion that a significant part of the metals and magmas have a crustal source.
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