• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 146
  • 125
  • 44
  • 24
  • 9
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 418
  • 90
  • 85
  • 66
  • 48
  • 47
  • 44
  • 39
  • 35
  • 28
  • 26
  • 24
  • 23
  • 22
  • 21
  • 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

Jura-triassic magmatism and porphyry Au-Cu mineralization at the Pine Deposit, Toodoggone District, North-central British Columbia

Dickinson, Jenni Michelle 05 1900 (has links)
The Pine, Fin, and Mex porphyry Au-Cu ± Mo systems are all located within a 10 km² area in the Toodoggone district, along the eastern margin of the Stikine terrane in British Columbia. Multiple episodes of porphyry-style mineralization are associated with these three magmatic centres. The Fin monzogranite is the oldest dated pluton in the district, with a U-Pb zircon emplacement age of 217.8 ± 0.6 Ma. A cross-cutting main-stage quartz-pyrite-chalcopyrite ± molybdenite ± sphalerite vein gives an older Re-Os molybdenite mineralization age of 221.0 ± 1.4 Ma. Hence the vein probably cross-cuts a slightly older, undated magmatic phase. Lead isotope values for sulphide minerals from main-stage veins indicate that magmatic-derived fluids interacted with country rocks and possibly other fluids. The Pine quartz monzonite (U-Pb zircon emplacement age of 197.6 ± 0.5 Ma) intrudes, alters, and locally mineralizes Toodoggone Formation Duncan Member andesite tuff (U-Pb zircon age of 200.9 ± 0.4 Ma). High-grade (0.57 g/t Au and 0.15% Cu) mineralization occurs in main-stage quartz-magnetite chalcopyrite-pyrite veins and disseminated throughout the potassic alteration zone in the Pine quartz monzonite stock. Late-stage anhydrite-pyrite ± specular hematite ± chalcopyrite, quartz-pyrite ± chalcopyrite, and pyrite ± chalcopyrite veins and related phyllic alteration cross-cut earlier veins. Propylitic alteration occurs distal to the potassic core of Pine in the Fin monzogranite and Duncan Member andesite. Limited fluid inclusion data, in combination with S and Pb isotope values for veins and host rocks, suggest that the main-stage fluid was magmatic-derived and deposited metals at 430 to 550 °C and depths of about 5.5 km. Late-stage fluids were also probably derived from the Pine quartz monzonite but interacted with Takla Group country rock prior to metal deposition. Metals were deposited at temperatures of 330 to 430 °C and depths of about 5.0 to 5.5 km. The final mineralization phase of the Pine porphyry system is temporally constrained by the emplacement of weakly mineralized syenite dykes (U-Pb zircon age of 193.8 ± 0.5 Ma). The final stage of magmatism in the Pine-Fin-Mex area is defined by the emplacement of rhyolite dykes (U-Pb zircon age of 193.6±0.4 Ma).
2

Jura-triassic magmatism and porphyry Au-Cu mineralization at the Pine Deposit, Toodoggone District, North-central British Columbia

Dickinson, Jenni Michelle 05 1900 (has links)
The Pine, Fin, and Mex porphyry Au-Cu ± Mo systems are all located within a 10 km² area in the Toodoggone district, along the eastern margin of the Stikine terrane in British Columbia. Multiple episodes of porphyry-style mineralization are associated with these three magmatic centres. The Fin monzogranite is the oldest dated pluton in the district, with a U-Pb zircon emplacement age of 217.8 ± 0.6 Ma. A cross-cutting main-stage quartz-pyrite-chalcopyrite ± molybdenite ± sphalerite vein gives an older Re-Os molybdenite mineralization age of 221.0 ± 1.4 Ma. Hence the vein probably cross-cuts a slightly older, undated magmatic phase. Lead isotope values for sulphide minerals from main-stage veins indicate that magmatic-derived fluids interacted with country rocks and possibly other fluids. The Pine quartz monzonite (U-Pb zircon emplacement age of 197.6 ± 0.5 Ma) intrudes, alters, and locally mineralizes Toodoggone Formation Duncan Member andesite tuff (U-Pb zircon age of 200.9 ± 0.4 Ma). High-grade (0.57 g/t Au and 0.15% Cu) mineralization occurs in main-stage quartz-magnetite chalcopyrite-pyrite veins and disseminated throughout the potassic alteration zone in the Pine quartz monzonite stock. Late-stage anhydrite-pyrite ± specular hematite ± chalcopyrite, quartz-pyrite ± chalcopyrite, and pyrite ± chalcopyrite veins and related phyllic alteration cross-cut earlier veins. Propylitic alteration occurs distal to the potassic core of Pine in the Fin monzogranite and Duncan Member andesite. Limited fluid inclusion data, in combination with S and Pb isotope values for veins and host rocks, suggest that the main-stage fluid was magmatic-derived and deposited metals at 430 to 550 °C and depths of about 5.5 km. Late-stage fluids were also probably derived from the Pine quartz monzonite but interacted with Takla Group country rock prior to metal deposition. Metals were deposited at temperatures of 330 to 430 °C and depths of about 5.0 to 5.5 km. The final mineralization phase of the Pine porphyry system is temporally constrained by the emplacement of weakly mineralized syenite dykes (U-Pb zircon age of 193.8 ± 0.5 Ma). The final stage of magmatism in the Pine-Fin-Mex area is defined by the emplacement of rhyolite dykes (U-Pb zircon age of 193.6±0.4 Ma).
3

Jura-triassic magmatism and porphyry Au-Cu mineralization at the Pine Deposit, Toodoggone District, North-central British Columbia

Dickinson, Jenni Michelle 05 1900 (has links)
The Pine, Fin, and Mex porphyry Au-Cu ± Mo systems are all located within a 10 km² area in the Toodoggone district, along the eastern margin of the Stikine terrane in British Columbia. Multiple episodes of porphyry-style mineralization are associated with these three magmatic centres. The Fin monzogranite is the oldest dated pluton in the district, with a U-Pb zircon emplacement age of 217.8 ± 0.6 Ma. A cross-cutting main-stage quartz-pyrite-chalcopyrite ± molybdenite ± sphalerite vein gives an older Re-Os molybdenite mineralization age of 221.0 ± 1.4 Ma. Hence the vein probably cross-cuts a slightly older, undated magmatic phase. Lead isotope values for sulphide minerals from main-stage veins indicate that magmatic-derived fluids interacted with country rocks and possibly other fluids. The Pine quartz monzonite (U-Pb zircon emplacement age of 197.6 ± 0.5 Ma) intrudes, alters, and locally mineralizes Toodoggone Formation Duncan Member andesite tuff (U-Pb zircon age of 200.9 ± 0.4 Ma). High-grade (0.57 g/t Au and 0.15% Cu) mineralization occurs in main-stage quartz-magnetite chalcopyrite-pyrite veins and disseminated throughout the potassic alteration zone in the Pine quartz monzonite stock. Late-stage anhydrite-pyrite ± specular hematite ± chalcopyrite, quartz-pyrite ± chalcopyrite, and pyrite ± chalcopyrite veins and related phyllic alteration cross-cut earlier veins. Propylitic alteration occurs distal to the potassic core of Pine in the Fin monzogranite and Duncan Member andesite. Limited fluid inclusion data, in combination with S and Pb isotope values for veins and host rocks, suggest that the main-stage fluid was magmatic-derived and deposited metals at 430 to 550 °C and depths of about 5.5 km. Late-stage fluids were also probably derived from the Pine quartz monzonite but interacted with Takla Group country rock prior to metal deposition. Metals were deposited at temperatures of 330 to 430 °C and depths of about 5.0 to 5.5 km. The final mineralization phase of the Pine porphyry system is temporally constrained by the emplacement of weakly mineralized syenite dykes (U-Pb zircon age of 193.8 ± 0.5 Ma). The final stage of magmatism in the Pine-Fin-Mex area is defined by the emplacement of rhyolite dykes (U-Pb zircon age of 193.6±0.4 Ma). / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
4

Investigations into new methods for the destruction of CF←4 and C←2F←6

Lott, Robert Martin Terence January 1997 (has links)
No description available.
5

The role of farmyard manure in improving maize production in the sub-humid highlands of Central Kenya

Kihanda, Francis Muchoki January 1996 (has links)
No description available.
6

The role of microstructural and fluid processes in the genesis of gold-bearing shear zones : Fazenda Maria Preta mine, Rio Itapicuru greenstone belt, Bahia, Brazil

Xavier, Roberto Perez January 1991 (has links)
No description available.
7

Characterization of two human hypertrophic chrondrocyte-like cell lines and the effects of 1,25(OH)←2D←3, dexamethasone on their functions

Cao, Xuesong January 1998 (has links)
No description available.
8

Deposition and diagenesis of Waulsortian carbonates from Tynagh, Co. Galway, Ireland : Their relationship with base metal mineralization

Akhurst, M. C. January 1988 (has links)
No description available.
9

Factors influencing the mineralization of organic nitrogen, phosphorus and sulphur in soils

Agbede, Olusola Omosofe January 1984 (has links)
Part I of this thesis is a critical review of the literature on the contents, availability and factors that individually and/or severally influence mineralization of organic N, P and S in soils. The review also pinpointed the importance of mineralized portions of these plant nutrients in tropical rainforest farming systems. After establishing the efficiency of the useof bicarbonate anion exchange resin as an extractant for available P and S in soils, the method was employed throughout the remainder of this investigation to assay plant available P and S in ten Nigerian and three Scottish soils either before, during, or after the incubation and greenhouse studies. In order to identify those factors that most strongly influence mineralization of organic N, P and S in soils, the following facts were revealed through several incubation experiments with both Scottish and Nigerian soils. (i) There was higher microbial activity and hence higher production of mineral N, extractable P and S at the soil moisture content of 60 than 40% WHC. (ii) Drying and rewetting cycles positively affected NH4-N, P and S extractability but had no effect on NO3-N production. (iii) Increased soil C:N ratios had a complex effect on microbial activities and nutrient availabilities. At a ratio of 25, (a) there was complete immobilization of soil N with subsequent slow remineralization even after 96 days, (b) there was immobilization of P or decrease in resin extractable P, (c) there was increase in resin extractable S probably due to (d) lower pH levels that resulted from glucose additions, (e) there were always substantial increases in exchangeable Al, Fe and Mn following the addition of glucose, and this might have contributed to the decreases in resin extractable P observed. (iv) Nitrification was increased following the addition of NH4-N to a soil with high initial N content but had a depressing effect where the initial N content was low. (v) Added P stimulated the production of both NH4-N and NO3-N. (vi) Liming decreased accumulation of NH4-N, extractable Al, Fe and Mn but resulted in higher rates of nitrification, and increased resin extractable P and S. (vii) Partial sterilization of soil with toluene resulted in the accumulation of mineral-N entirely as NH4-N, an indication that toluene was effective as a nitrification inhibitor. Greenhouse studies using the Stanford and DeMent seedling short-term nutrient absorption technique showed positive effects of soil incubation, liming, N and P additions on the availability and offtake of N and S, the magnitude of which depended very much on soil type. However, P offtake was decreased by soil incubation prior to cropping. Similarly, the increase in resin extractable P due to liming observed during incubation studies did not manifest during the nutrient absorption studies. In general, there are significant interactions between factors affecting mineralization of N, P and S and therefore their effects cannot be evaluated in isolation of one another. The nitrification process is much more sensitive to adverse soil conditions than ammonification, and NO3-N production can be supressed by increased soil acidity, soil active S and the heavy metallic cations. Al which complexes rapidly with P in soil, follows the trends in pH changes that occur upon liming, application of acid nutrient fertilizers, and increased soil C:N ratio through glucose additions. The flush in active Al as pH falls may account for decrease in available P observed upon increase C:N ratio rather than microbial P-immobilization. It appears that soil pH and C:N ratio are the two factors most strongly influencing availability of N, P and S in soils. The effects of other factors on mineralization depend on the extent to which they themselves directly or indirectly affect soil pH and C:N ratio. In acid tropical rainforest soils which usually receive heavy annual precipitation, the accumulation of mineral-N as NH4-N. may be beneficial in preventing N losses through leaching. On the other hand, leaching losses of SO4-S in these soils may result in S-deficiencies. Hence, there should be well-researched liming and fertilizer programmes in order to enhance the availability of both added and mineralized N, P and S.
10

Effects manufacturing method on surface mineralization of bioactive glasses

Pirayesh, Hamidreza Unknown Date
No description available.

Page generated in 0.1289 seconds