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Abstract
Cretaceous-Paleocene porphyry Cu(±Mo±Au) occurrences are scattered throughout the Yukon-Tanana upland in eastern Alaska. Known occurrences in eastern Alaska are poorly characterized, despite a resurgence in exploration. Porphyry deposits in the upland are emplaced into structurally complex metamorphic rocks representing a variety of tectonic environments, resulting in diverse alteration and mineralization assemblages. New mapping, drill core logging, petrography, geochemistry, geochronology, and structural analysis allow improved characterization of the parameters of porphyry systems and identify key linkages to regional tectonic and magmatic events. New sericite 40Ar/39Ar and zircon U/Pb dates constrain porphyry systems to the Late Cretaceous-earliest Paleocene (ca. 71-63 Ma). Zircon Hf-isotope ratios and Ce and Eu concentrations indicate that Late Cretaceous-Paleocene intrusions emplaced into basement dominated by Triassic and Jurassic plutons are more isotopically juvenile, reflecting more oxidized conditions. In contrast, those emplaced into basement dominated by mid-Cretaceous plutons are more reduced crustal geochemical-affinity. Diversity in mineral assemblages in contrasting systems may reflect emplacement into crustal domains of varying compositions and oxidation states. Those formed within a domain containing more-oxidized Triassic and Jurassic plutons are molybdenite-rich and apparently lack gold. In contrast, systems formed within domains dominated by more reduced mid-Cretaceous plutons contain lower-sulfidation state mineral assemblages with reported gold.
Study Area
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | Links between tectonics, magmatism, and mineralization in the formation of Late Cretaceous porphyry systems in the Yukon-Tanana upland, eastern Alaska, USA |
| Year Published | 2019 |
| Language | English |
| Publisher | Society for Geology Applied to Mineral Deposits (SGA) |
| Contributing office(s) | Alaska Science Center Geology Minerals |
| Description | 4 p. |
| Larger Work Type | Book |
| Larger Work Subtype | Conference publication |
| Larger Work Title | Proceedings of the 15th biennial meeting for geology applied to mineral deposits |
| First page | 939 |
| Last page | 942 |
| Conference Title | 15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits 27 |
| Conference Location | Glasgow, Scotland |
| Conference Date | Aug 27-30, 2019 |
| Country | Canada, United States |
| State | Alaska, Yukon |
| Other Geospatial | Yukon-Tanana upland |
| Google Analytic Metrics | Metrics page |