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Tectonic and Metallogenic Evolution of the Yukon-Tanana Upland, Alaska Active

By Alaska Science Center May 22, 2018

The Yukon-Tanana upland in eastern interior Alaska is a geologically complex block containing deposits of base-metal, platinum-group-element, and gold-silver-copper mineralization. It also hosts numerous mineral systems that are known or suspected to contain critical minerals.

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Scientist examining outcrops of strongly deformed and metamorphosed rock, Divide Mountain, Yukon-Tanana, eastern Alaska
Sources/Usage: Public Domain.
USGS scientist examining outcrops of strongly deformed and metamorphosed rock along Divide Mountain in the Yukon-Tanana upland of eastern Alaska.(Credit: Jamey V. Jones III, USGS. Public domain.)

This multi-year study focuses on the geologic, metallogenic, and geophysical framework of the broader Yukon-Tanana upland in east-central Alaska. The project builds on a strong legacy of previous and recent USGS work in eastern Alaska and involves close collaboration with the Alaska Division of Geological and Geophysical Surveys (DGGS) and Canadian counterparts in the Yukon Geological Survey and Geological Survey of Canada. The area of interest extends from the western Tanacross and Eagle quadrangles to the Fairbanks area. The area includes two producing gold mines, multiple mineral districts, and numerous deposits and prospects that are the focus of active mineral resource exploration. All known or suspected mineral systems in the region have the potential for associated critical mineral enrichments. This project coordinates with systematic geological mapping and geophysical surveys conducted by DGGS under the USGS Earth Mapping Resource Initiative so that we fully capitalize on all available resources and thoroughly characterize the tectonic, magmatic, structural, geochemical, isotopic, and metallogenic evolution of one of Alaska’s important mineral belts.

 

Current Activities

Geologic Framework

Contact: James V. Jones III, jvjones@usgs.gov

Geologic framework studies involve regional geological mapping, bedrock exhumation and landscape evolution studies, and associated analytical work (for example, geochronology, thermochronology, petrology, geochemistry) across the entire Yukon-Tanana upland. Research includes igneous, metamorphic, structural, and thermochronologic studies. This work is integrated with geophysical and metallogenic tasks described below to provide comprehensive constraints on the tectonic evolution of the region and framework geological controls on its mineral endowment.

Scientist digging in tundra to find bedrock for geochemistry and geochronology sampling, Yukon-Tanana upland, eastern Alaska
Sources/Usage: Public Domain.
USGS scientist digging through tundra in hopes of finding bedrock to sample for geochemistry and geochronology, Yukon-Tanana upland, eastern Alaska.​​​​​​​(Credit: Jamey V. Jones III, USGS. Public domain.)

Metallogenic Framework

Contact: Douglas C. Kreiner, dkreiner@usgs.gov 

Metallogenic framework studies involve delineation of prospective mineral systems across the region and geological mapping of key mineral occurrences and deposits in the study area.  Comprehensive analytical methods (for example, geochronology, geochemistry, radiogenic and stable isotopes) are combined with geological observations to characterize mineralization and to relate it to the geological context and tectonic environment(s) in which it formed.

Exploration Geochemistry

Contact: Karen Kelley, kkelley@usgs.gov

Use of indicator mineral and hydrogeochemistry exploration techniques to explore for concealed or hidden mineral systems beneath the extensive alluvial/colluvial cover in the region. This research also involves placer gold fingerprinting studies to assess how distinct mineralogical, mineral chemistry, and geochemical signatures in sediment, placer gold (heavy mineral concentrates), and water reflect different deposit types in the upland.

 

Geophysical Framework

Contact: Ben Drenth, bdrenth@usgs.gov

Geophysical framework studies involve strategic planning of new, high-resolution airborne magnetic and radiometric surveys throughout the region together with synthesis and modeling of existing geophysical data. Processing, interpretation, and integration of new data with existing data compiled across the international border will inform geological and metallogenic mapping and modeling throughout the region.

 

Completed Activities

Tectonic and Metallogenic Evolution of the Eastern Yukon-Tanana upland, Alaska

Alaska/Yukon Geophysical/Geological Reconciliation of the Pericratonic Yukon-Tanana Terrane

These two previous projects focused on the easternmost part of the Yukon-Tanana upland adjacent to the Alaska-Yukon border. This research involved integration of geological, metallogenic, and geophysical data in the Tanacross and Eagle quadrangles of eastern Alaska to address cross-border correlation of geologic units, litho-tectonic assemblages, and metallogenic domains.

Below are data or web applications associated with this project.

Filter Total Items: 15

Data for Uranium-Lead Geochronology, Carbon and Sulfur Stable Isotopes, and Raman Spectroscopy from Graphite Creek, Alaska

This data release supports the paper titled, "Insights into the metamorphic history and origin of flake graphite mineralization at the Graphite Creek graphite deposit, Seward Peninsula, Alaska, USA", published in the journal Mineralium Deposita. The data release includes zircon and titanite U-Pb-Thisotope and age data, monazite U-Pb-Th isotope, trace element and age data, carbon and sulfur stablei
By
Alaska Science Center

U-Pb Isotopic Data and Ages of Detrital Zircon from Selected Rocks from Southwestern Alaska and the Yukon-Tanana Upland and Environs of Eastern Interior Alaska and Eastern Yukon, Canada

This data set contains U-Pb isotopic data and associated ages of detrital zircon from sedimentary and metasedimentary rocks collected from southwestern Alaska and from the Yukon-Tanana upland and environs of eastern interior Alaska and western Yukon, Canada. The samples were collected as part of geological mapping and research conducted from 1996 to 2021 and funded by the Mineral Resources Program
By
Alaska Science Center

U-Pb Ages, Hafnium Isotope Ratios, and Trace Element Concentrations by Laser-Ablation Split Stream (LASS) Analysis of Igneous Zircons from the Western Alaska Range

This data set contains U-Pb isotopic data and ages, Hf isotope data, and trace element concentrations of zircon from igneous rocks collected from the western Alaska Range of south-central Alaska. The sample suite was collected as part of geological mapping and supporting geochemical and geochronological analysis conducted from 2011 to 2013. We also analyzed portions of remainders of previously col
By
Alaska Science Center

U-Pb Isotopic Data and Ages of Detrital Zircon from Selected Rocks from northern Yukon, Canada

This data set contains U-Pb isotopic data and associated ages of detrital zircon from sedimentary and metasedimentary rocks collected in northern Yukon, Canada. The samples were originally collected as part of geological mapping and research conducted by the Geological Survey of Canada. They were recovered from archived collections and sent to the U.S. Geological Survey for analysis of detrital zi
By
Alaska Science Center

Totatlanika River Terrace Luminescence Age Data Collected 2020-2022

This dataset comprises three tables containing infrared stimulated luminescence (IRSL) ages and related data from samples collected at seven terrace sites along the Totatlanika River in central Alaska in 2020 and 2021. The IRSL ages and data were generated from the samples at the Utah State University Luminescence Lab. The ages were determined to enable computation of rates of bedrock incision alo
By
Alaska Science Center

Whole Rock Major and Trace Element Chemistry for Igneous and Metamorphic Rocks from the Yukon-Tanana Upland, Alaska

This data set consists of one table containing whole-rock geochemistry data for 753 igneous and metamorphic rocks from the Yukon-Tanana upland of eastern interior Alaska, collected between 2013 and 2019. All materials were analyzed by ALS Global, between 2014 and 2020, by a range of different techniques, so multiple unique entries for a given element relate to different analytical methods or prepa
By
Alaska Science Center

Charley River Cosmogenic Isotope Data Collected 2019-2021

This data release comprises three tables containing cosmogenic beryllium-10 and aluminum-26 concentrations and related data from samples collected at four sites along the Charley River in central Alaska in 2019, prepared in 2020 at the University of Vermont (UVM), and measured at the Purdue Rare Isotope Measurement lab (PRIME) in 2021. The file "geology_siteLocations_Charley_bender_2022.csv" conta
By
Alaska Science Center

U-Pb zircon data for igneous units related to mineralization in the eastern Yukon-Tanana upland, eastern Alaska

From 2017-2019, framework metallogenic studies were completed in the eastern Yukon-Tanana upland in eastern Alaska. Numerous previously undated plutons known or suspected to contain components of porphyry, epithermal, and intrusion-related gold systems and associated deposit types were sampled for age and zircon trace element determinations between the Black Mountain area and the Yukon border, nor
By
Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center

Zircon Trace Element Data for Igneous Units Related to Mineralization in the Eastern Yukon-Tanana Upland and nearby areas, Eastern Alaska

From 2017-2019, framework metallogenic studies were completed in the eastern Yukon-Tanana upland in eastern Alaska. Numerous previously undated plutons known or suspected to contain components of porphyry, epithermal, and intrusion-related gold systems and associated deposit types were sampled for age and zircon trace element determinations between the Black Mountain area and the Yukon border, nor
By
Alaska Science Center

Re-Os Geochronologic Data for Porphyry Deposits in the Yukon-Tanana Upland, Eastern Alaska

Rhenium-osmium (Re-Os) geochronology of molybdenite provides a tool to directly date mineralizing events in hydrothermal systems. In the Yukon-Tanana upland of eastern Alaska, numerous molybdenite-bearing porphyry occurrences are recognized. The deposits are related to middle and Late Cretaceous granitoids (Kreiner and others, 2019; 2020). Some of the porphyry districts have multiple superimposed
By
Alaska Science Center

Fodar Orthomosaic and Digital Elevation Model of the Totatlanika River Corridor (Alaska, USA) Acquired August 2021

This dataset provides a digital elevation model derived from airborne fodar data acquired in 2021 on August 31 over the Totatlanika River in central Alaska. The term fodar is a portmanteau of foto and lidar, coined by Matt Nolan, which describes a method of quantifying the color and elevation of Earth surfaces via airborne small-format digital camera photography.
By
Alaska Science Center

Field Data Collected 2018 to Document Human-induced Gorge Incision at The Kink (Fortymile River, Alaska)

This dataset comprises four tables containing channel survey cross section data, field observations including channel width and bank material, measured surface water velocity, and alluvial grain size data collected along the North Fork Fortymile River near a man-made meander cutoff called The Kink. The data release also contains eight field photos used to obtain grain size distribution; four photo
By
Alaska Science Center

Below are publications associated with this project.

Results of automated scanning electron microscope (SEM) analyses of rock and stream sediment samples from the Taurus porphyry copper deposit area, Tanacross quadrangle, eastern Alaska

Numerous porphyry copper-molybdenum-gold and epithermal deposits define a belt that extends from Eastern Alaska to western Yukon, Canada. An orientation study conducted near the Taurus porphyry deposit was designed to test methods that require minimal sample collection, preparation, and analytical time to determine the viability of indicator mineral studies as a reconnaissance exploration method.
Authors
Karen D. Kelley, Katharina Pfaff, Garth E. Graham
By
Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center

Thermotectonic history of the Kluane Ranges and evolution of the eastern Denali Fault Zone in southwestern Yukon, Canada

Exhumation and landscape evolution along strike‐slip fault systems reflect tectonic processes that accommodate and partition deformation in orogenic settings. We present 17 new apatite (U‐Th)/He (He), zircon He, apatite fission‐track (FT), and zircon FT dates from the eastern Denali fault zone (EDFZ) that bounds the Kluane Ranges in Yukon, Canada. The dates elucidate patterns of deformation along

Authors
Robert G. McDermott, Alexis K. Ault, Jonathan S. Caine, Stuart N. Thomson
By
Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Mendenhall Research Fellowship Program

Alaska and Yukon magnetic compilation, residual total magnetic field

This map is a compilation of aeromagnetic surveys over Yukon and eastern Alaska. Aeromagnetic surveys measure the total intensity of the earth's magnetic field. The field was measured by a magnetometer aboard an aircraft flown in parallel lines spaced at 200 m to 10000 m across the map area. The magnetic field reflects magnetic properties of bedrock and provides qualitative and quantitative inform
Authors
W. Miles, Richard W. Saltus, N. Hayward, D. Oneschuk
By
Mineral Resources Program, Geology, Minerals, Energy, and Geophysics Science Center, Geology, Geophysics, and Geochemistry Science Center

Detrital zircon geochronology of quartzose metasedimentary rocks from parautochthonous North America, east-central Alaska

We report eight new U-Pb detrital zircon ages for quartzose metasedimentary rocks from four lithotectonic units of parautochthonous North America in east-central Alaska: the Healy schist, Keevy Peak Formation, and Sheep Creek Member of the Totatlanika Schist in the northern Alaska Range, and the Butte assemblage in the northwestern Yukon-Tanana Upland. Excepting 1 of 3 samples from the Healy schis
Authors
Cynthia Dusel-Bacon, Christopher S. Holm-Denoma, James V. Jones, John N. Aleinikoff, James K. Mortensen
By
Energy and Minerals Mission Area, Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Apatite fission-track evidence for regional exhumation in the subtropical Eocene, block faulting, and localized fluid flow in east-central Alaska

The origin and antiquity of the subdued topography of the Yukon–Tanana Upland (YTU), the physiographic province between the Denali and Tintina faults, are unresolved questions in the geologic history of interior Alaska and adjacent Yukon. We present apatite fission-track (AFT) results for 33 samples from the 2300 km2 western Fortymile district in the YTU in Alaska and propose an exhumation model t
Authors
Cynthia Dusel-Bacon, Charles R. Bacon, Paul B. O'Sullivan, Warren C. Day
By
Energy and Minerals Mission Area, Mineral Resources Program, Volcano Hazards Program, Volcano Science Center, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Mesozoic magmatism and timing of epigenetic Pb-Zn-Ag mineralization in the western Fortymile mining district, east-central Alaska: Zircon U-Pb geochronology, whole-rock geochemistry, and Pb isotopes

The Mesozoic magmatic history of the North American margin records the evolution from a more segmented assemblage of parautochthonous and allochthonous terranes to the more cohesive northern Cordilleran orogenic belt. We characterize the setting of magmatism, tectonism, and epigenetic mineralization in the western Fortymile mining district, east-central Alaska, where parautochthonous and allochtho
Authors
Cynthia Dusel-Bacon, J.N. Aleinkoff, W. C. Day, J.K. Mortensen
By
Energy and Minerals Mission Area, Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center

The Late Cretaceous Middle Fork caldera, its resurgent intrusion, and enduring landscape stability in east-central Alaska

Dissected caldera structures expose thick intracaldera tuff and, uncommonly, cogenetic shallow plutons, while remnants of correlative outflow tuffs deposited on the pre-eruption ground surface record elements of ancient landscapes. The Middle Fork caldera encompasses a 10 km × 20 km area of rhyolite welded tuff and granite porphyry in east-central Alaska, ∼100 km west of the Yukon border. Intracal
Authors
Charles R. Bacon, Cynthia Dusel-Bacon, John N. Aleinikoff, John F. Slack
By
Natural Hazards Mission Area, Volcano Hazards Program, Geology, Energy & Minerals Science Center, Volcano Science Center, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Tackling “boundary faults” across the Alaska-Yukon border: a report from the field

One day in late May, a team of geologists from two countries and four different organizations got together in a remote corner of the Yukon Territory to try to rectify a mapping discrepancy called a “boundary fault.”
Authors
Rick Saltus
By
Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Geochemistry, petrography, and zircon U-Pb geochronology of Paleozoic metaigneous rocks in the Mount Veta area of east-central Alaska: implications for the evolution of the westernmost part of the Yukon-Tanana terrane

We report the results of new mapping, whole-rock major, minor, and trace-element geochemistry, and petrography for metaigneous rocks from the Mount Veta area in the westernmost part of the allochthonous Yukon–Tanana terrane (YTT) in east-central Alaska. These rocks include tonalitic mylonite gneiss and mafic metaigneous rocks from the Chicken metamorphic complex and the Nasina and Fortymile River
Authors
Cynthia Dusel-Bacon, Warren C. Day, John N. Aleinikoff
By
Energy and Minerals Mission Area, Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Geological Survey of Canada
Yukon Geological Survey

The University of British Columbia