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dc.contributor.advisorMonecke, Thomas
dc.contributor.authorZeeck, Lauren R.
dc.date.accessioned2018-10-22T16:35:11Z
dc.date.accessioned2022-02-03T13:15:09Z
dc.date.available2018-10-22T16:35:11Z
dc.date.available2022-02-03T13:15:09Z
dc.date.issued2018
dc.identifierZeeck_mines_0052N_11619.pdf
dc.identifierT 8610
dc.identifier.urihttps://hdl.handle.net/11124/172575
dc.descriptionIncludes bibliographical references.
dc.description2018 Fall.
dc.description.abstractThe Miocene low-sulfidation epithermal Hokuryu and Omui deposits of the Omu camp in northeastern Hokkaido, Japan, are small past-producers of high-grade Au and Ag ores. The quartz textures and distribution of ore minerals within vein samples were studied to identify the processes that resulted in the bonanza-grade precious metal enrichment in these deposits. Correlative microscopy involving optical microscopy, cathodoluminescence microscopy, and scanning electron microscopy was employed. The research shows that vein quartz exhibits a wide range of textures that represent primary growth patterns. In addition, textures indicative of recrystallization of silica precursor phases and replacement of other vein minerals were recognized. In the high-grade vein samples, which are crustiform or brecciated in hand specimen, ore minerals almost exclusively occur within distinct dark gray to black quartz bands. These bands alternate with barren, white to light gray quartz suggesting that ore deposition was episodic. The bands hosting the ore are colloform and composed of mosaic quartz. High-magnification microscopy reveals the presence of densely packed relic microspheres providing evidence that the mosaic quartz formed through recrystallization of a non-crystalline silica precursor phase. The ore minerals occur interstitially to the densely packed microspheres indicating that ore deposition was contemporaneous to the agglomeration of the microspheres. These colloform bands with relic microsphere textures are interpreted to have formed through rapid silica and ore mineral deposition within the veins at high temperatures, presumably involving temporary flashing of the hydrothermal system. Limited fluid inclusion data suggests that silica deposition occurred at a temperature of over 245-250°C implying that flashing occurred to a depth of over 400 m below the paleosurface. The ore-hosting colloform bands composed of agglomerated microspheres are texturally distinct from barren, colloform bands containing fibrous chalcedonic quartz bands formed at lower temperatures. The findings of this study are consistent with models linking the high-grade precious metal enrichment in low-sulfidation epithermal veins to episodic flashing of the hydrothermal system and have significant implications to the design of exploration strategies for bonanza-grade low sulfidation epithermal vein deposits.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2018 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subjectflashing
dc.subjectOmu
dc.subjectsilica
dc.subjectHokkaido
dc.subjectepithermal
dc.subjectquartz textures
dc.titleRole of flashing in the formation of high-grade, low-sulfidation epithermal deposits: a case study from the Omu Camp in Hokkaido, Japan, The
dc.typeText
dc.contributor.committeememberPfaff, Katharina
dc.contributor.committeememberReynolds, T. James
dc.contributor.committeememberHennigh, Quinton
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplineGeology and Geological Engineering
thesis.degree.grantorColorado School of Mines


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