Geology and gold mineralization of the Nyac district, southwest Alaska
dc.contributor.author | Wenz, Zachary John | |
dc.date.accessioned | 2015-09-23T01:03:42Z | |
dc.date.available | 2015-09-23T01:03:42Z | |
dc.date.issued | 2004-08 | |
dc.identifier.uri | http://hdl.handle.net/11122/6023 | |
dc.description | Thesis (M.S.) University of Alaska Fairbanks, 2004 | en_US |
dc.description.abstract | The Nyac district, southwest Alaska, contains multiple felsic to mafic plutons and dikes intruding the volcano-sedimentary package of the Nyac terrane. Dated plutons and dikes in the Nyac terrane record Early Cretaceous ages; other plutons in southwest Alaska are Late Cretaceous and Tertiary. The Nyac district contains high-temperature and low-temperature gold mineralization. The age of high-temperature mineralization is concordant with plutonism and the low-T mineralization is younger, possibly Tertiary. The high-temperature mineralization occurs in the Bonanza Pluton and associated grey granodiorite porphyry dikes. Bonanza Pluton mineralization consists of gold-bearing quartz veins with pyrite-chalcopyrite-magnetite-bismuthinite-molybdenite. Fluid inclusions from mineralized quartz veins record trapping temperatures up to 560⁰ C and salinities up to 60 wt% NaCl. Mineralization in the grey granodiorite porphyry dikes consists of gold-bearing quartz veins with tellurobismuthite-tetradymite-chalcopyrite. Fluid inclusions from mineralized quartz veins record trapping temperatures up to 370⁰ C, salinities up to 5 wt% NaCl, and CO₂ concentrations up to 80 vol%. Both types display sericite-chlorite-albite alteration, and the Bonanza Pluton also displays potassic alteration. The low-temperature mineralization occurs at the Bonanza Creek Color Anomaly and along high-angle faults. This type contains anomalous Au and Hg. The alteration assemblage is sericite-kaolinite, indicating low temperature (<240⁰ C) and acidic fluids. | en_US |
dc.description.tableofcontents | Introduction -- Geology and geophysics -- Gold mineralization -- Geochronology -- Mineralization model -- Conclusions -- References -- Appendices. | en_US |
dc.language.iso | en_US | en_US |
dc.title | Geology and gold mineralization of the Nyac district, southwest Alaska | en_US |
dc.type | Thesis | en_US |
dc.identifier.department | Department of Geology and Geophysics | |
refterms.dateFOA | 2020-03-20T01:50:38Z |
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