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Genesis and controls on mineralization at the Hammer Zone silver showing, Mount Mye Trend, hosted by the Anvil Batholith, South-Central Yukon

  • Author / Creator
    Rogers, Michael A
  • When Silver Range resources acquired the Keg property in 2010, one of the prospects included was the Hammer Zone. Ensuing mapping and surface sampling found the Hammer Zone to be a small, bonanza-grade, epithermal silver system contained entirely within the Anvil Batholith. Initial petrographic observations described silver as being hosted by galena in rhodochrosite veins. However this study disagrees with galena as the primary host to silver, and suggests the majority of silver is hosted by freibergite found as crystalline inclusions in sphalerite and alongside galena. Geochemical studies classify the Anvil Suite granite, primary lithology of the Anvil Batholith, as an ilmenite series, calc-alkaline, peraluminous, S-type granitoid forming from low degrees of partial melt, possibly in a post-collisional setting. Previous studies on the age of the Anvil Suite granite found it to be 106.6±1.0Ma. In addition previous studies also found alteration associated with the Hammer Zone to be around 100.6±1.1Ma, at least 3.8 million years younger. This study believes a difference in ages that great means the Anvil Suite granite is not the causal heat source for the Hammer Zone mineralization. The Hammer Zone mineralization comprises four phases, identified by the gangue mineral hosting the sulfide mineralization. Calcite veining and associated sulfide mineralization including silver bearing minerals, dyscrasite, pyrargyrite, stephanite and acanthite constitute the first phase. The next phase involves quartz veining and minor amounts of sulfide mineralization; no silver is present in this paragenetic phase. Large rhodochrosite veins and an uptick in the amount of sulfides present including, sphalerite, galena, arsenopyrite and most importantly silver-bearing freibergite constitute the third phase of veining. The final phase of veining is composed of chlorite and minor quartz veining alongside hematite staining of the host rock Anvil Suite granite. Stable isotope analysis of the carbonate paragenetic phases revealed that the initial fluid responsible for mineralization is meteoric water. The analysis also outlined the influence of a second source of fluid or stable isotope reservoir. In the calcite phase of mineralization there are two major influences, the sedimentary rocks hosting the Anvil Batholith and magmatic fluid. The quartz and rhodochrosite phases shows a dominant influence of only one other stable isotope reservoir, magmatic fluid. Analysis of carbon and oxygen isotopes in the carbonate phases also highlighted a change in depositional mechanism from boiling in the calcite phase to mixing in the quartz and rhodochrosite phases. All the conclusions drawn from studying stable isotopes are supported by fluid inclusions. Mineral chemistry analysis using electron microprobe analysis and laser ablation inductively coupled plasma mass spectrometry discovered that in addition to influential fluids, the fluid chemistry changed considerably through the paragenetic phases. During deposition of the calcite phase, the fluid was reducing and low in sulfur. During the quartz and rhodochrosite ore stages there was a dramatic change in fluid chemistry to high sulfur, oxidizing fluid. Through these changes in fluid chemistry and proportions of source fluids this study hypothesizes that the Hammer Zone moved from deposition akin to a low sulfidation system to closer to a high sulfidation system.

  • Subjects / Keywords
  • Graduation date
    2017-11:Fall 2017
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3DR2PP3M
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Department of Earth and Atmospheric Sciences
  • Supervisor / co-supervisor and their department(s)
    • Sarah Gleeson (Department of Earth and Atmospheric Sciences)
  • Examining committee members and their departments
    • Stephen Johnston (Department of Earth and Atmospheric Sciences)
    • Jeremy Richards (Department of Earth and Atmospheric Sciences)