USGS researcher collecting samples in Kanuti, Alaska. The samples collected in this location were more resistant to weathering than the surrounding rock indicating a change in lithology.
Understanding PGE, Cr, Ni and Cu Potential in Ophiolitic Rocks in Alaska
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By Alaska Science Center
May 17, 2024
Ophiolites are sections of oceanic lithosphere that have been structurally emplaced onto continental crust. The ultramafic components of some ophiolites contain podiform chromitites, an important potential source of several strategic and critical minerals, including chromium and platinum group elements (PGE). Yet the tectonics and petrogenesis of several Alaskan ophiolites is poorly understood. This project endeavors to resolve the tectono-magmatic history of a suite of ophiolitic systems within Alaska, contributing towards an understanding of the primary conditions favorable for resource endowments.
Return to Geology
Alaska reflects a complex history of the accretion of disparate allochthonous terranes. Mafic-ultramafic complexes thought to represent variably complete sections of oceanic lithosphere, or ophiolites, are presumed to demarcate their paleo-boundaries. Several major ophiolite belts are recognized in interior/eastern Alaska, and occurrences of ore-grade PGEs are known from some, but not others. The origin, chronology, and tectonic context for most of these ophiolitic ore-magmatic systems remain poorly understood, as does the explanation for non-uniform PGE enrichments.
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With few exceptions, most studies and mapping of Alaskan ophiolites were undertaken in the mid/late-20th century, primarily at the reconnaissance-level, and did not employ modern geochemical and geochronological techniques. As with analytical methods, the concept of ophiolite systems has also advanced significantly in the last few decades. Not all ophiolites are created equal, and the conceptual framework now exists to interpret the nature and melting conditions of source mantle, spreading rate/geometry, paleo-proximity to plumes/trenches/arcs, and availability of fluids during the formation of preserved oceanic lithosphere. These factors control the degree and composition of critical minerals in the ophiolite systems. Reinterpreting the origins of the mafic-ultramafic rocks in a modern framework will aid in the evaluation of critical mineral potential of Alaska.
Sources/Usage: Public Domain. View Media Details
Initial efforts are focused on ophiolitic components of the Seventymile-Slide Mountain, Angayucham, Ruby, Livengood and Tozitna-Innoko terranes. Samples for this work were collected by legacy mapping and assessment efforts, as well as samples collected from fieldwork completed from 2013 to 2023. This project works to constrain the tectonic setting and petrogenesis of each system, contributing to a more comprehensive understanding of the mineral endowments in, and the assembly of, Alaska, including processes that localize and structurally translate its terrane components.
Tectonic and Metallogenic Evolution of the Yukon-Tanana Upland, Alaska
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.
Sample Collection, Kanuti, Alaska
USGS researcher collecting samples in Kanuti, Alaska. The samples collected in this location were more resistant to weathering than the surrounding rock indicating a change in lithology.
Recording observations on the outcrop of the Kanuti Ophiolite
USGS researcher making observations and recording information on the outcrop of the Kanuti Ophiolite in Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
USGS researcher making observations and recording information on the outcrop of the Kanuti Ophiolite in Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
Leave no stone unturned
USGS researcher collecting one more sample while waiting for the helicopter in Kanuti, Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
USGS researcher collecting one more sample while waiting for the helicopter in Kanuti, Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
Variation of weathering on rock surface
Variation of weathering and lichen growth on the rock surface reveals veins and segregated zones with different mineralogy.
Variation of weathering and lichen growth on the rock surface reveals veins and segregated zones with different mineralogy.
Ophiolites are sections of oceanic lithosphere that have been structurally emplaced onto continental crust. The ultramafic components of some ophiolites contain podiform chromitites, an important potential source of several strategic and critical minerals, including chromium and platinum group elements (PGE). Yet the tectonics and petrogenesis of several Alaskan ophiolites is poorly understood. This project endeavors to resolve the tectono-magmatic history of a suite of ophiolitic systems within Alaska, contributing towards an understanding of the primary conditions favorable for resource endowments.
Return to Geology
Alaska reflects a complex history of the accretion of disparate allochthonous terranes. Mafic-ultramafic complexes thought to represent variably complete sections of oceanic lithosphere, or ophiolites, are presumed to demarcate their paleo-boundaries. Several major ophiolite belts are recognized in interior/eastern Alaska, and occurrences of ore-grade PGEs are known from some, but not others. The origin, chronology, and tectonic context for most of these ophiolitic ore-magmatic systems remain poorly understood, as does the explanation for non-uniform PGE enrichments.
Sources/Usage: Public Domain. View Media Details
With few exceptions, most studies and mapping of Alaskan ophiolites were undertaken in the mid/late-20th century, primarily at the reconnaissance-level, and did not employ modern geochemical and geochronological techniques. As with analytical methods, the concept of ophiolite systems has also advanced significantly in the last few decades. Not all ophiolites are created equal, and the conceptual framework now exists to interpret the nature and melting conditions of source mantle, spreading rate/geometry, paleo-proximity to plumes/trenches/arcs, and availability of fluids during the formation of preserved oceanic lithosphere. These factors control the degree and composition of critical minerals in the ophiolite systems. Reinterpreting the origins of the mafic-ultramafic rocks in a modern framework will aid in the evaluation of critical mineral potential of Alaska.
Sources/Usage: Public Domain. View Media Details
Initial efforts are focused on ophiolitic components of the Seventymile-Slide Mountain, Angayucham, Ruby, Livengood and Tozitna-Innoko terranes. Samples for this work were collected by legacy mapping and assessment efforts, as well as samples collected from fieldwork completed from 2013 to 2023. This project works to constrain the tectonic setting and petrogenesis of each system, contributing to a more comprehensive understanding of the mineral endowments in, and the assembly of, Alaska, including processes that localize and structurally translate its terrane components.
Tectonic and Metallogenic Evolution of the Yukon-Tanana Upland, Alaska
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.
Sample Collection, Kanuti, Alaska
USGS researcher collecting samples in Kanuti, Alaska. The samples collected in this location were more resistant to weathering than the surrounding rock indicating a change in lithology.
USGS researcher collecting samples in Kanuti, Alaska. The samples collected in this location were more resistant to weathering than the surrounding rock indicating a change in lithology.
Recording observations on the outcrop of the Kanuti Ophiolite
USGS researcher making observations and recording information on the outcrop of the Kanuti Ophiolite in Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
USGS researcher making observations and recording information on the outcrop of the Kanuti Ophiolite in Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
Leave no stone unturned
USGS researcher collecting one more sample while waiting for the helicopter in Kanuti, Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
USGS researcher collecting one more sample while waiting for the helicopter in Kanuti, Alaska. The Kanuti ophiolite is a mafic-ultramafic thrust sheet of probable Jurassic age, formerly considered to be the upper part of the Yukon-Koyukuk ophiolite (Angayucham terrane).
Variation of weathering on rock surface
Variation of weathering and lichen growth on the rock surface reveals veins and segregated zones with different mineralogy.
Variation of weathering and lichen growth on the rock surface reveals veins and segregated zones with different mineralogy.