Undergraduate Thesis Or Project
 

Analysis of Au-Te-bearing ores of the Jewett Mine, Josephine County, Oregon_Final.pdf

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  • The Jewett Mine is a hard rock mine located on the southern flank of Mount Baldy, approximately 1.6 km from Grants Pass in Josephine County, Oregon on the Grants Pass mining district. The Jewett Group contains 7 separate claims totaling approximately 1.42 km² and consists of several workings including an open pit and approximately 300 m of underground workings following a series of thin hydrothermal quartz-calcite breccia veins containing free gold and tellurides. Ar⁴⁰/Ar³⁹ ratios in muscovite from samples of the mineralized vein collected from the Jewett Mine indicate that mineralization occurred 153.67 ± 0.46 Ma, using the Argon Lab at Oregon State University. EMPA and SEM analysis show that Au and two types of tellurides, tetradymite (Bi₂Te₂S) and tellurobismuthite (Bi₂Te₃), are present within the quartz veins. Observations and analysis suggest that this deposit is the result of low temperature (<300°C) Au-Te-bearing hydrothermal fluids forced into country rock through areas of weakness, such as faults and fractures that was either enriched in metals via fractionation of a nearby magmatic body or by assimilation from the host rock (or both). Previous thought was that the fluids were derived from the neighboring Grants Pass Pluton, a quartz diorite intrusion from the Early Cretaceous (139 Ma ± 2) located just northwest of the claim. While observations support most of this genetic model, the age of mineralization suggest that the fluids were derived from a different, older source, such as the 154 Ma Jacksonville Pluton approximately 30 km to the east or perhaps was the result of heat and pressure caused by the accretion of the Western Klamath terrane (155-145 Ma) to the west and northwest of the Grants Pass Pluton. Further mapping and dating of nearby mineralized zones and geologic units is needed in order to investigate the heat source issue.
  • Keywords: Klamath Mountains, Jewett Mine
  • Keywords: Klamath Mountains, Jewett Mine
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file details Analysis_of_Au-Te-bearing_ores_of_the_Jewett_Mine__Josephine_County__Oregon_Final.pdf 2017-07-21 Public Download