Thesis (Ph. D.)--University of Pennsylvania, 1910. / "Reprinted from the Transactions of the Wagner Free Institute of Science of Philadelphia, vol. VII, February, 1910." Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 129-139).

Thesis--Wisconsin. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 172-175).

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 147-159).

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

<p> The Dolphin deposit is an intrusion-related gold deposit (IRGD) located approximately 30 km north of Fairbanks, Alaska. The deposit is in--and adjacent to--a composite mid-Cretaceous pluton intruding amphibolite facies metamorphic rocks. NI43-101 compliant gold resource estimations for the deposit utilizing a 0.3 g/t cut-off, is 61.5 Million tonnes (Mt) at 0.69 g/t indicated (1.36 million oz = Moz) and 71.5 Mt at 0.69 g/t inferred (1.58 Moz). </p><p> Due to extensive hydrothermal alteration of the intrusion, identifying lithology in hand sample and thin section, as well as by standard compositional techniques (SiO₂ vs. Na₂O + K₂O), has proven problematic. By plotting wt% TiO₂ vs. P₂O₅ obtained from XRF analysis and four-acid digest ICP-MS data, two distinct population clusters appear. By comparison with least-altered intrusive rock analyses from the Fairbanks district, the igneous units can be identified as granite and tonalite. Because there is no gradational transition through an intermediate granodiorite unit, they were most likely derived from two separate magmatic bodies rather than <i>in-situ</i> fractionation from a single parent. Tonalite is concentrated along the northern and eastern margins of the stock with granite composing the rest of the body. Tonalite xenoliths in granite and granite dikes intruding tonalite prove that tonalite is the older unit. </p><p> Investigations of hydrothermal alteration (based on chemical analyses, X-ray diffraction, and thin section examination) show albitic and advanced argillic (kaolinite-quartz) alteration are the dominant styles with sericite common throughout. Advanced argillic is a low temperature (&lt;300&deg;C) low pH alteration style that has not been previously identified in intrusion related gold deposits (IRGDs) in interior Alaska. Albitic alteration resulted from higher temperature, more neutral pH fluids. </p><p> Gold investigations show that gold occurs as coarse-grained Au&deg;, aurostibite, and maldonite in quartz + sulfide veins; fine-grained Au&deg; in the oxide zone; and in many forms in disseminated sulfide. These forms include Au&deg; inclusions in pyrite and arsenopyrite, solid-solution Au within compositionally zoned arsenopyrite, and as Au&deg; nanoparticles in pyrite and arsenopyrite. Using UAF&rsquo;s JEOL JXA-8530F microprobe, I found that solid-solution gold occurs only in arsenopyrite with strong compositional zoning. These have low As cores; gold-bearing mantles with moderate % As; and high As rims. In contrast, compositionally homogenous arsenopyrite does not contain solid-solution gold. Pyrite is commonly arsenian and carries dissolved gold (if any) near detection limits. Gold mineralization has not been tied to any lithology or alteration style; however, gold does seem to correlate with abrupt changes in alteration, especially between sericite + albite and kaolinite + sericite alteration and gold-bearing, zoned arsenopyrites are associated with advanced argillic alteration.</p><p>

Introduction: The object of mineral exploration is to locate economic deposits with minimum expenditure in time and money . In order to achieve this goal it is essential to select the most favourable environment and to design the search procedures for the environment in question. Duricrusts are a striking feature of tropical and subtropical landscapes where they occur as extensive, resistant horizons which form a surface or near-surface caprock and are best seen in incised landscapes. Since they cover many potentially rich mineral , provinces of the world, it is important to question what effect they have on mineral exploration. Duricrusts are defined as specific soil types formed by near-surface processes associated with weathering . In spite of the sheer aerial extent of soils over the landsurfaces of the earth, Levinson (1974) expressed surprise at how little exploration geologists know about this surficial environment . Weathering and pedogenetic processes therefore, require discussion in this text. However, in order to adhere to the scope of this dissertation only a brief description of the factors and characteristics of soil formation are given in the first chapter. In the second part, duricrusts are differentiated on the basis of composition into laterite, silcrete and calcrete. Beginning with a concise description of both natural and experimental investigations concerned with mineral decomposition and neomineralisation during weathering, the morphological, physical and chemical characters of each type are described. Environmental factors are then discussed in an attempt to identify specific duricrust types in terms of climate, geographic location, age and formation process . Once duricrust structure and texture are related to topography, specific types may be used to assess the significance of suspected markers in the landscape and permit identification of individual weathering surfaces on which mineralisation may give rise to gossans of widely different physical and chemical characteristics. The interpretation of photogeological, geochemical and geophysical data acquired during mineral exploration in duricrust terrains is problematical and some of the limitations to these search procedures are discussed in the final .chapter

<p> The May Lake interpluton screen is a 4 km long, &sim;0.5 km wide swath of metamorphic rock cropping out between plutons of the &sim;103 Ma Yosemite Valley Intrusive Suite and the &sim;93-85 Ma Tuolumne Intrusive Suite in Yosemite National Park, California. Metasomatic alteration and recrystallization due to contact metamorphism and fluid infiltration resulted from the emplacement of the Cretaceous plutons. Mineral assemblages are consistent with metamorphism to hornblende-hornfels and amphibolite facies. The presence of sillimanite-bearing metapelite and more Mg-rich clinopyroxene in calc-silicate assemblages of the northeast section of the screen than the southwest suggest higher grade metamorphism was experienced to the northeast. Pseudosection diagrams created from whole rock chemical analyses of three metapelite rocks also indicate higher temperatures in the northeastern section of the screen with minimum temperatures estimated from &sim;540-617&deg;C. Based on petrographic analysis of andalusite- and sillimanite-bearing metapelite, it is likely that the screen experienced two stages of contact metamorphism: relatively lower temperature metamorphism during intrusion of the Yosemite Valley Intrusive Suite followed by relatively higher temperature contact metamorphism during intrusion of the more mafic Tuolumne Intrusive Suite. Stable isotope data suggest that rock permeability and preexisting structures were the strongest factors controlling fluid infiltration through the contact aureole.</p><p>

Abstract not available.

The mineralogy, petrology and petrogenesis of a representative suite of late Archean syenitic intrusions emplaced along the Porcupine-Destor fault zone near Matheson, Ontario in the southern Abitibi greenstone belt are studied using a combined approach involving field work, petrography, mineral chemistry and, major and trace element geochemistry. Members of the Matheson suite are from east to west: Iris, Garrison, Emens, Ludgate and Pangea intrusions. The Iris, Emens, Ludgate and Pangea intrusions are mostly composed of syenitic rocks with compositions ranging from alkali-feldspar quartz-syenite to melasyenite. Textures range from equigranular to porphyritic. Iris and Pangea intrusions also contain related mafic rocks. The Garrison intrusion is composed of hornblende quartz-monzonite. All intrusions but one have hypersolvus feldspar assemblages; the exception being Garrison intrusion, which displays a subsolvus feldspar assemblage. The occurrence of late aegirine-augite, magnesioriebeckite and widespread albite replacement, especially in rocks from Ludgate and Iris intrusions, indicates that late or post-magmatic sodium-rich fluids variably affected the rocks. Two magmatic series were identified based on silica-saturation properties and alkali-contents. (Abstract shortened by UMI.)