--> Abstract: The Bokan Mountain U-Ree Deposit, Prince of Wales Island, Alaska, by H. J. Keyser, C. G. Hanson, and J. Dostal; #90088 (2009)

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The Bokan Mountain U-Ree Deposit, Prince of Wales Island, Alaska

H. J. Keyser1, C. G. Hanson2, and J. Dostal3
1Precision GeoSurveys Inc., Vancouver, Canada, [email protected]
2Landmark Alaska Limited Partnership, Ketchikan, AK, [email protected]
3Ucore Uranium Inc., Halifax, Canada, [email protected]

The Bokan Mountain Uranium and Rare Earth Element (REE) deposit is located on southern Prince of Wales Island, approximately 60 km southwest of Ketchikan, Alaska. Bokan Mountain produced 1.3 million pounds of uranium between 1957 and 1971 and is the only uranium mine in Alaska. Ucore Uranium Inc. is currently exploring the property, with 46 drill holes totaling over 3,000 meters completed in 2007 and 2008.

Although most of the early investigations at Bokan Mountain focused on uranium as nuclear fuel, the potential for REE’s is now being addressed for various high technology and energy applications. Both U and REE mineralization are spatially and genetically associated with the Bokan Intrusive Complex, a circular, Jurassic-aged, peralkaline granite. Multiple phases of sodic granites, porphyries, and pegmatites have been grouped into two main concentric zones: an inner core of riebeckite granite porphyry and an outer ring of aegirine granite porphyry. More than 30 mineral occurrences are related to differentiation and metal enrichment during late stages of magma crystallization.

Uranium mineralization is controlled by northwest-trending structures within the outer aegerine granites. The primary uranium minerals are uranothorite and uraninite associated with quartz, hematite, calcite, fluorite, pyrite, galena, chlorite, and REE. Grades in excess of 1% U3O8 are not uncommon.

Light and heavy REE mineralization (+/- U, Y, Zr, and Nb) is hosted by north and northwest-trending pegmatitic and aplitic dikes peripheral to the Bokan Intrusive Complex. These dikes range in width from several meters to a few centimeters, commonly in parallel stockwork systems, and are evidence of the highly fractionated nature of late-stage fluids/melts. Although most of the REE mineralization is outside the Bokan complex, it is clearly associated with the intrusion. The dominant REE and Y minerals are xenotime, allanite, bastnaesite, and monazite.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009