Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska
The Lower Jurassic (ca. 177 Ma) Bokan Mountain granitic complex, located on southern Prince of Wales Island, southernmost Alaska hosts a high-grade uranium-thorium deposit with past production. The complex is a circular body (~3 km in diameter) which intruded Paleozoic granitoids as well as metasedi...
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ftmdpi:oai:mdpi.com:/2075-163X/13/8/1032/ 2023-08-20T04:09:23+02:00 Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska Jaroslav Dostal agris 2023-07-31 application/pdf https://doi.org/10.3390/min13081032 EN eng Multidisciplinary Digital Publishing Institute Mineral Deposits https://dx.doi.org/10.3390/min13081032 https://creativecommons.org/licenses/by/4.0/ Minerals; Volume 13; Issue 8; Pages: 1032 peralkaline granite Alaska uranium thorium rare earth elements deposit Bokan Mountain Text 2023 ftmdpi https://doi.org/10.3390/min13081032 2023-08-01T11:06:13Z The Lower Jurassic (ca. 177 Ma) Bokan Mountain granitic complex, located on southern Prince of Wales Island, southernmost Alaska hosts a high-grade uranium-thorium deposit with past production. The complex is a circular body (~3 km in diameter) which intruded Paleozoic granitoids as well as metasedimentary and metavolcanic rocks of the Alexander Terrane of the North American Cordillera. This shallow seated intrusion, which is composed of fractionated peralkaline granites, is a zoned body with a dominant core of arfvedsonite granite and a rim of aegirine granite. All the rock-forming minerals typically record a two-stage growth history and aegirine and arfvedsonite were the last major phases to crystallize from the magma. Both arfvedsonite and aegirine granites have overlapping compositions. The rocks have high contents of rare earth elements, Th, U and high field strength elements (Zr, Nb, Hf and Ta) and low contents of Sr, Ba, Eu and Ti, typical of peralkaline granites. The complex hosts structurally controlled rare metal mineralization, which is associated with the late-stage of magma evolution and hydrothermal fluids. Fluorine complexing played a role during the transportation of rare metals in hydrothermal fluids. The U-Th deposit, which occurs at the margin of the aegirine granite zone, includes structurally controlled shear zone-hosted lenses and irregularly shaped pipe-like orebodies. U-Th mineralization is associated with desilicified and albitized granitic rocks and includes mainly uranothorite and uraninite. These minerals mostly form small ovoids in veinlets typically 0.1 to 1 mm wide. The mine produced about 77,000 t of ore at a grade of ~0.76% U3O8 and 3% of ThO2. The parent magma of the pluton was likely derived from a metasomatized lithospheric source (mantle or lower crust), which was enriched by subduction related processes during Paleozoic time. Text Prince of Wales Island Alaska MDPI Open Access Publishing Prince of Wales Island ENVELOPE(-99.001,-99.001,72.668,72.668) Minerals 13 8 1032 |
institution |
Open Polar |
collection |
MDPI Open Access Publishing |
op_collection_id |
ftmdpi |
language |
English |
topic |
peralkaline granite Alaska uranium thorium rare earth elements deposit Bokan Mountain |
spellingShingle |
peralkaline granite Alaska uranium thorium rare earth elements deposit Bokan Mountain Jaroslav Dostal Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska |
topic_facet |
peralkaline granite Alaska uranium thorium rare earth elements deposit Bokan Mountain |
description |
The Lower Jurassic (ca. 177 Ma) Bokan Mountain granitic complex, located on southern Prince of Wales Island, southernmost Alaska hosts a high-grade uranium-thorium deposit with past production. The complex is a circular body (~3 km in diameter) which intruded Paleozoic granitoids as well as metasedimentary and metavolcanic rocks of the Alexander Terrane of the North American Cordillera. This shallow seated intrusion, which is composed of fractionated peralkaline granites, is a zoned body with a dominant core of arfvedsonite granite and a rim of aegirine granite. All the rock-forming minerals typically record a two-stage growth history and aegirine and arfvedsonite were the last major phases to crystallize from the magma. Both arfvedsonite and aegirine granites have overlapping compositions. The rocks have high contents of rare earth elements, Th, U and high field strength elements (Zr, Nb, Hf and Ta) and low contents of Sr, Ba, Eu and Ti, typical of peralkaline granites. The complex hosts structurally controlled rare metal mineralization, which is associated with the late-stage of magma evolution and hydrothermal fluids. Fluorine complexing played a role during the transportation of rare metals in hydrothermal fluids. The U-Th deposit, which occurs at the margin of the aegirine granite zone, includes structurally controlled shear zone-hosted lenses and irregularly shaped pipe-like orebodies. U-Th mineralization is associated with desilicified and albitized granitic rocks and includes mainly uranothorite and uraninite. These minerals mostly form small ovoids in veinlets typically 0.1 to 1 mm wide. The mine produced about 77,000 t of ore at a grade of ~0.76% U3O8 and 3% of ThO2. The parent magma of the pluton was likely derived from a metasomatized lithospheric source (mantle or lower crust), which was enriched by subduction related processes during Paleozoic time. |
format |
Text |
author |
Jaroslav Dostal |
author_facet |
Jaroslav Dostal |
author_sort |
Jaroslav Dostal |
title |
Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska |
title_short |
Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska |
title_full |
Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska |
title_fullStr |
Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska |
title_full_unstemmed |
Jurassic Uranium-Thorium Deposit of Peralkaline Granitic Rocks, Bokan Mountain, Prince of Wales Island, Southeastern Alaska |
title_sort |
jurassic uranium-thorium deposit of peralkaline granitic rocks, bokan mountain, prince of wales island, southeastern alaska |
publisher |
Multidisciplinary Digital Publishing Institute |
publishDate |
2023 |
url |
https://doi.org/10.3390/min13081032 |
op_coverage |
agris |
long_lat |
ENVELOPE(-99.001,-99.001,72.668,72.668) |
geographic |
Prince of Wales Island |
geographic_facet |
Prince of Wales Island |
genre |
Prince of Wales Island Alaska |
genre_facet |
Prince of Wales Island Alaska |
op_source |
Minerals; Volume 13; Issue 8; Pages: 1032 |
op_relation |
Mineral Deposits https://dx.doi.org/10.3390/min13081032 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3390/min13081032 |
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Minerals |
container_volume |
13 |
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8 |
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1032 |
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