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Western Alaska Range Metallogeny and Tectonics

Completed
By Alaska Science Center January 1, 2017

There are many different types of mineral deposits present in the Western Alaska Range: plutonic gold, porphyry copper-gold (Pebble prospect), epithermal gold, tin-silver skarns, sedimentary barite, mafic hosted nickle-platinum-group elements, uranium-thorium rare earth elements, and even a diamond prospect.

Return to Geology

Scientific Issue and Relevance

There are many different types of mineral deposits present in the Western Alaska Range: plutonic gold, porphyry copper-gold (Pebble prospect), epithermal gold, tin-silver skarns, sedimentary barite, mafic hosted nickle-platinum-group elements, uranium-thorium rare earth elements, and even a diamond prospect. All of these have been the targets of recent exploration efforts, but their relationships to the regional magmatic belts and stratigraphy is not known. Improved understanding of Alaska's geologic framework will help to put these mineral deposits into a regional magmatic and tectonic framework, which is the best predictor of mineral occurrence and contribute to improved assessments of undiscovered resources. The Nation will have more accurate estimates of the national mineral endowment as improvements are made concerning the distribution of these deposits, their age, and genetic processes that define the localization of the mineralizing events.

Research Activities

The project objectives were to produce an improved model of the geologic framework underpinning the Western Alaska Range in south-central Alaska. Numerous ore deposits are present in this region, and most appear to be associated with magmatic events, but the ages and types of mineral deposits in relation to their host rocks needed to be identified. We conducted detailed geologic studies to delineate the magmatic, stratigraphic, and tectonic differences that distinguish this area from adjacent geologic terranes. Field mapping, geochronology, thermochronology, geochemical analyses, and geophysical data contributed to an improved understanding of the relationship between ore deposits and tectonic architecture that is critical to an assessment of the overall mineral potential of the area. Our main tasks are below.

  • Produce a new geologic map of the western Alaska Range.
  • Metallogeny of the western Alaska Range.
  • Petrogenesis of western Alaska Range igneous rocks.
  • Geophysical framework of the western Alaska Range.
  • Exhumation, erosion, and tectonics of the western Alaska Range.
  • Framework geology for mineral assessment.

Below are other science projects associated with this project.

link
Scientists wait for a helicopter pickup at a geologic mapping and sampling station high in the Neacola Mountains, Alaska

Metallogeny and Tectonics of the Lake Clark and Neacola Mountains Region, South-central Alaska

Alaska hosts a well-documented belt of ore deposits that lies roughly parallel to the Alaska Range, beginning at the Alaska Peninsula in the southwest, continuing up through the Fairbanks Mining District in the north, and curving back into the Tintina Gold Belt on its eastern end. Known mineral prospects and occurrences include porphyry copper, intrusion-related gold, volcanogenic massive sulfides...
By
Mineral Resources Program, Alaska Science Center
link

Metallogeny and Tectonics of the Lake Clark and Neacola Mountains Region, South-central Alaska

Alaska hosts a well-documented belt of ore deposits that lies roughly parallel to the Alaska Range, beginning at the Alaska Peninsula in the southwest, continuing up through the Fairbanks Mining District in the north, and curving back into the Tintina Gold Belt on its eastern end. Known mineral prospects and occurrences include porphyry copper, intrusion-related gold, volcanogenic massive sulfides...
Learn More

Below are data or web applications associated with this project.

Fission Track Data and Ages of Apatite and U-Pb Isotopic Data and Ages of Igneous and Detrital Zircon from Selected Rocks from the Lake Clark and Lake Iliamna Region of South-Central Alaska

This data set contains fission track data and associated ages of apatite from igneous and sedimentary rocks, U-Pb isotopic data and associated ages of zircon from a subset of the igneous rock samples, and U-Pb isotopic data and associated ages of detrital zircon from a subset of the sedimentary rock samples. All samples were collected from the region surrounding Lake Clark and Lake Iliamna in sout
By
Alaska Science Center

Whole Rock Major and Trace Element Chemistry for Igneous Rocks from Tyonek, Lime Hills, Talkeetna, McGrath, and Lake Clark Quadrangles, Western Alaska Range, Alaska

This data release contains whole rock major and trace element data for 69 igneous rock samples collected from the Western Alaska Range between 2011 and 2012. The Series field relates to chronological units discussed in Jones et al. (2021, Geosphere) and Todd et al. (2022 IN PREP). Descriptions are from original collector notebooks and are provided here for informational purposes only.
By
Alaska Science Center

U-Pb Isotopic Data and Ages of Detrital Zircon Grains and Graptolite Fossil Data from Selected Rocks from the Western Alaska Range, Livengood area, and Seward Peninsula, Alaska - 2018

This data set contains two data sets. One data set is of U-Pb isotopic data and associated ages of detrital zircon grains from 16 sedimentary and metasedimentary rocks from the western Alaska Range, Livengood area and Seward Peninsula, Alaska. Two samples were collected from the York Mountains area of the Seward Peninsula of western Alaska. Three samples were collected from the Livengood quadrangl
By
Alaska Science Center

Below are publications associated with this project.

Cretaceous to Oligocene magmatic and tectonic evolution of the western Alaska Range: Insights from U-Pb and 40Ar/39Ar geochronology

New U-Pb and 40Ar/39Ar ages integrated with geologic mapping and observations across the western Alaska Range constrain the distribution and tectonic setting of Cretaceous to Oligocene magmatism along an evolving accretionary plate margin in south-central Alaska. These rocks were emplaced across basement domains that include Neoproterozoic to Jurassic carbonate and siliciclastic strata of the Fare
Authors
James V. Jones, Erin Todd, Stephen E. Box, Peter J. Haeussler, Christopher Holm-Denoma, Susan M. Karl, Garth E. Graham, Dwight Bradley, Andrew R.C. Kylander-Clark, Richard M. Friedman, Paul W. Layer
By
Alaska Science Center, Geology, Geophysics, and Geochemistry Science Center

The Mystic subterrane (partly) demystified: New data from the Farewell terrane and adjacent rocks, interior Alaska

The youngest part of the Farewell terrane in interior Alaska (USA) is the enigmatic Devonian–Cretaceous Mystic subterrane. New U-Pb detrital zircon, fossil, geochemical, neodymium isotopic, and petrographic data illuminate the origin of the rocks of this subterrane. The Devonian–Permian Sheep Creek Formation yielded youngest detrital zircons of Devonian age, major detrital zircon age probability p
Authors
Julie A. Dumoulin, James V. Jones, Stephen E. Box, Dwight Bradley, Robert A. Ayuso, Paul B. O'Sullivan
By
Alaska Science Center

Late Oligocene to present contractional structure in and around the Susitna basin, Alaska—Geophysical evidence and geological implications

The Cenozoic Susitna basin lies within an enigmatic lowland surrounded by the Central Alaska Range, Western Alaska Range (including the Tordrillo Mountains), and Talkeetna Mountains in south-central Alaska. Some previous interpretations show normal faults as the defining structures of the basin (e.g., Kirschner, 1994). However, analysis of new and existing geophysical data shows predominantly (Lat
Authors
Richard W. Saltus, Richard G. Stanley, Peter J. Haeussler, James V. Jones, Christopher J. Potter, Kristen A. Lewis
By
Groundwater and Streamflow Information Program, Alaska Science Center

Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

Cenozoic growth of the Alaska Range created the highest topography in North America, but the space-time pattern and drivers of exhumation are poorly constrained. We analyzed U/Pb and fission-track double dates of detrital zircon and apatite grains from 12 catchments that span a 450 km length of the Alaska Range to illuminate the timing and extent of exhumation during different periods. U/Pb ages i
Authors
Richard O. Lease, Peter J. Haeussler, Paul O'Sullivan
By
Groundwater and Streamflow Information Program, Alaska Science Center

Targeting Cu–Au and Mo resources using multi-media exploration geochemistry: An example from Tyonek Quadrangle, Alaska Range, Alaska

Regional stream and pond sediment, panned concentrate, and water sampling at and around known mineral occurrences in the Tyonek quadrangle, Alaska Range, Alaska were undertaken to determine geochemical signatures in the different media. For sediment samples, two different size fractions (− 80 mesh and − 230 mesh) were analyzed. Elevated concentrations (mostly ~ 2 × median) of elements such as As,
Authors
Garth E. Graham, Ryan D. Taylor, Gregory K. Lee, Dick Tripp
By
Geology, Geophysics, and Geochemistry Science Center

Timing of ore-related magmatism in the western Alaska Range, southwestern Alaska

This report presents isotopic age data from mineralized granitic plutons in an area of the Alaska Range located approximately 200 kilometers to the west-northwest of Anchorage in southwestern Alaska. Uranium-lead isotopic data and trace element concentrations of zircons were determined for 12 samples encompassing eight plutonic bodies ranging in age from approximately 76 to 57.4 millions of years
Authors
Ryan D. Taylor, Garth E. Graham, Eric D. Anderson, David Selby
By
Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center

Proterozoic geochronological links between the Farewell, Kilbuck, and Arctic Alaska terranes

New U-Pb igneous and detrital zircon ages reveal that despite being separated by younger orogens, three of Alaska’s terranes that contain Precambrian rocks—Farewell, Kilbuck, and Arctic Alaska—are related. The Farewell and Kilbuck terranes can be linked by felsic magmatism at ca. 850 Ma and by abundant detrital zircons in the Farewell that overlap the ca. 2010–2085 Ma age range of granitoids in th
Authors
Dwight Bradley, William C. McClelland, Richard M. Friedman, Paul B. O'Sullivan, Paul Layer, Marti L. Miller, Julie A. Dumoulin, Alison B. Till, J. Grant Abbott, Dan B. Bradley, Joseph L. Wooden
By
Groundwater and Streamflow Information Program, Alaska Science Center

Detrital zircon geochronology of Cretaceous and Paleogene strata across the south-central Alaskan convergent margin

Ages of detrital zircons are reported from ten samples of Lower Cretaceous to Paleogene metasandstones and sandstones from the Chugach Mountains, Talkeetna Mountains, and western Alaska Range of south-central Alaska. Zircon ages are also reported from three igneous clasts from two conglomerates. The results bear on the regional geology, stratigraphy, tectonics, and mineral resource potential of th
Authors
Dwight Bradley, Peter J. Haeussler, Paul O'Sullivan, Rich Friedman, Alison Till, Dan Bradley, Jeff Trop
By
Ecosystems Mission Area, Alaska Science Center

There are many different types of mineral deposits present in the Western Alaska Range: plutonic gold, porphyry copper-gold (Pebble prospect), epithermal gold, tin-silver skarns, sedimentary barite, mafic hosted nickle-platinum-group elements, uranium-thorium rare earth elements, and even a diamond prospect.

Return to Geology

Scientific Issue and Relevance

There are many different types of mineral deposits present in the Western Alaska Range: plutonic gold, porphyry copper-gold (Pebble prospect), epithermal gold, tin-silver skarns, sedimentary barite, mafic hosted nickle-platinum-group elements, uranium-thorium rare earth elements, and even a diamond prospect. All of these have been the targets of recent exploration efforts, but their relationships to the regional magmatic belts and stratigraphy is not known. Improved understanding of Alaska's geologic framework will help to put these mineral deposits into a regional magmatic and tectonic framework, which is the best predictor of mineral occurrence and contribute to improved assessments of undiscovered resources. The Nation will have more accurate estimates of the national mineral endowment as improvements are made concerning the distribution of these deposits, their age, and genetic processes that define the localization of the mineralizing events.

Research Activities

The project objectives were to produce an improved model of the geologic framework underpinning the Western Alaska Range in south-central Alaska. Numerous ore deposits are present in this region, and most appear to be associated with magmatic events, but the ages and types of mineral deposits in relation to their host rocks needed to be identified. We conducted detailed geologic studies to delineate the magmatic, stratigraphic, and tectonic differences that distinguish this area from adjacent geologic terranes. Field mapping, geochronology, thermochronology, geochemical analyses, and geophysical data contributed to an improved understanding of the relationship between ore deposits and tectonic architecture that is critical to an assessment of the overall mineral potential of the area. Our main tasks are below.

  • Produce a new geologic map of the western Alaska Range.
  • Metallogeny of the western Alaska Range.
  • Petrogenesis of western Alaska Range igneous rocks.
  • Geophysical framework of the western Alaska Range.
  • Exhumation, erosion, and tectonics of the western Alaska Range.
  • Framework geology for mineral assessment.

Below are other science projects associated with this project.

link
Scientists wait for a helicopter pickup at a geologic mapping and sampling station high in the Neacola Mountains, Alaska

Metallogeny and Tectonics of the Lake Clark and Neacola Mountains Region, South-central Alaska

Alaska hosts a well-documented belt of ore deposits that lies roughly parallel to the Alaska Range, beginning at the Alaska Peninsula in the southwest, continuing up through the Fairbanks Mining District in the north, and curving back into the Tintina Gold Belt on its eastern end. Known mineral prospects and occurrences include porphyry copper, intrusion-related gold, volcanogenic massive sulfides...
By
Mineral Resources Program, Alaska Science Center
link

Metallogeny and Tectonics of the Lake Clark and Neacola Mountains Region, South-central Alaska

Alaska hosts a well-documented belt of ore deposits that lies roughly parallel to the Alaska Range, beginning at the Alaska Peninsula in the southwest, continuing up through the Fairbanks Mining District in the north, and curving back into the Tintina Gold Belt on its eastern end. Known mineral prospects and occurrences include porphyry copper, intrusion-related gold, volcanogenic massive sulfides...
Learn More

Below are data or web applications associated with this project.

Fission Track Data and Ages of Apatite and U-Pb Isotopic Data and Ages of Igneous and Detrital Zircon from Selected Rocks from the Lake Clark and Lake Iliamna Region of South-Central Alaska

This data set contains fission track data and associated ages of apatite from igneous and sedimentary rocks, U-Pb isotopic data and associated ages of zircon from a subset of the igneous rock samples, and U-Pb isotopic data and associated ages of detrital zircon from a subset of the sedimentary rock samples. All samples were collected from the region surrounding Lake Clark and Lake Iliamna in sout
By
Alaska Science Center

Whole Rock Major and Trace Element Chemistry for Igneous Rocks from Tyonek, Lime Hills, Talkeetna, McGrath, and Lake Clark Quadrangles, Western Alaska Range, Alaska

This data release contains whole rock major and trace element data for 69 igneous rock samples collected from the Western Alaska Range between 2011 and 2012. The Series field relates to chronological units discussed in Jones et al. (2021, Geosphere) and Todd et al. (2022 IN PREP). Descriptions are from original collector notebooks and are provided here for informational purposes only.
By
Alaska Science Center

U-Pb Isotopic Data and Ages of Detrital Zircon Grains and Graptolite Fossil Data from Selected Rocks from the Western Alaska Range, Livengood area, and Seward Peninsula, Alaska - 2018

This data set contains two data sets. One data set is of U-Pb isotopic data and associated ages of detrital zircon grains from 16 sedimentary and metasedimentary rocks from the western Alaska Range, Livengood area and Seward Peninsula, Alaska. Two samples were collected from the York Mountains area of the Seward Peninsula of western Alaska. Three samples were collected from the Livengood quadrangl
By
Alaska Science Center

Below are publications associated with this project.

Cretaceous to Oligocene magmatic and tectonic evolution of the western Alaska Range: Insights from U-Pb and 40Ar/39Ar geochronology

New U-Pb and 40Ar/39Ar ages integrated with geologic mapping and observations across the western Alaska Range constrain the distribution and tectonic setting of Cretaceous to Oligocene magmatism along an evolving accretionary plate margin in south-central Alaska. These rocks were emplaced across basement domains that include Neoproterozoic to Jurassic carbonate and siliciclastic strata of the Fare
Authors
James V. Jones, Erin Todd, Stephen E. Box, Peter J. Haeussler, Christopher Holm-Denoma, Susan M. Karl, Garth E. Graham, Dwight Bradley, Andrew R.C. Kylander-Clark, Richard M. Friedman, Paul W. Layer
By
Alaska Science Center, Geology, Geophysics, and Geochemistry Science Center

The Mystic subterrane (partly) demystified: New data from the Farewell terrane and adjacent rocks, interior Alaska

The youngest part of the Farewell terrane in interior Alaska (USA) is the enigmatic Devonian–Cretaceous Mystic subterrane. New U-Pb detrital zircon, fossil, geochemical, neodymium isotopic, and petrographic data illuminate the origin of the rocks of this subterrane. The Devonian–Permian Sheep Creek Formation yielded youngest detrital zircons of Devonian age, major detrital zircon age probability p
Authors
Julie A. Dumoulin, James V. Jones, Stephen E. Box, Dwight Bradley, Robert A. Ayuso, Paul B. O'Sullivan
By
Alaska Science Center

Late Oligocene to present contractional structure in and around the Susitna basin, Alaska—Geophysical evidence and geological implications

The Cenozoic Susitna basin lies within an enigmatic lowland surrounded by the Central Alaska Range, Western Alaska Range (including the Tordrillo Mountains), and Talkeetna Mountains in south-central Alaska. Some previous interpretations show normal faults as the defining structures of the basin (e.g., Kirschner, 1994). However, analysis of new and existing geophysical data shows predominantly (Lat
Authors
Richard W. Saltus, Richard G. Stanley, Peter J. Haeussler, James V. Jones, Christopher J. Potter, Kristen A. Lewis
By
Groundwater and Streamflow Information Program, Alaska Science Center

Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

Cenozoic growth of the Alaska Range created the highest topography in North America, but the space-time pattern and drivers of exhumation are poorly constrained. We analyzed U/Pb and fission-track double dates of detrital zircon and apatite grains from 12 catchments that span a 450 km length of the Alaska Range to illuminate the timing and extent of exhumation during different periods. U/Pb ages i
Authors
Richard O. Lease, Peter J. Haeussler, Paul O'Sullivan
By
Groundwater and Streamflow Information Program, Alaska Science Center

Targeting Cu–Au and Mo resources using multi-media exploration geochemistry: An example from Tyonek Quadrangle, Alaska Range, Alaska

Regional stream and pond sediment, panned concentrate, and water sampling at and around known mineral occurrences in the Tyonek quadrangle, Alaska Range, Alaska were undertaken to determine geochemical signatures in the different media. For sediment samples, two different size fractions (− 80 mesh and − 230 mesh) were analyzed. Elevated concentrations (mostly ~ 2 × median) of elements such as As,
Authors
Garth E. Graham, Ryan D. Taylor, Gregory K. Lee, Dick Tripp
By
Geology, Geophysics, and Geochemistry Science Center

Timing of ore-related magmatism in the western Alaska Range, southwestern Alaska

This report presents isotopic age data from mineralized granitic plutons in an area of the Alaska Range located approximately 200 kilometers to the west-northwest of Anchorage in southwestern Alaska. Uranium-lead isotopic data and trace element concentrations of zircons were determined for 12 samples encompassing eight plutonic bodies ranging in age from approximately 76 to 57.4 millions of years
Authors
Ryan D. Taylor, Garth E. Graham, Eric D. Anderson, David Selby
By
Mineral Resources Program, Geology, Geophysics, and Geochemistry Science Center

Proterozoic geochronological links between the Farewell, Kilbuck, and Arctic Alaska terranes

New U-Pb igneous and detrital zircon ages reveal that despite being separated by younger orogens, three of Alaska’s terranes that contain Precambrian rocks—Farewell, Kilbuck, and Arctic Alaska—are related. The Farewell and Kilbuck terranes can be linked by felsic magmatism at ca. 850 Ma and by abundant detrital zircons in the Farewell that overlap the ca. 2010–2085 Ma age range of granitoids in th
Authors
Dwight Bradley, William C. McClelland, Richard M. Friedman, Paul B. O'Sullivan, Paul Layer, Marti L. Miller, Julie A. Dumoulin, Alison B. Till, J. Grant Abbott, Dan B. Bradley, Joseph L. Wooden
By
Groundwater and Streamflow Information Program, Alaska Science Center

Detrital zircon geochronology of Cretaceous and Paleogene strata across the south-central Alaskan convergent margin

Ages of detrital zircons are reported from ten samples of Lower Cretaceous to Paleogene metasandstones and sandstones from the Chugach Mountains, Talkeetna Mountains, and western Alaska Range of south-central Alaska. Zircon ages are also reported from three igneous clasts from two conglomerates. The results bear on the regional geology, stratigraphy, tectonics, and mineral resource potential of th
Authors
Dwight Bradley, Peter J. Haeussler, Paul O'Sullivan, Rich Friedman, Alison Till, Dan Bradley, Jeff Trop
By
Ecosystems Mission Area, Alaska Science Center