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GEOREF RECORD

Geophysical interpretation of U, Th, and rare earth element mineralization of the Bokan Mountain peralkaline granite complex, Prince of Wales Island, southeast Alaska

Anne E. McCafferty, Douglas B. Stoeser and Bradley S. Van Gosen
Geophysical interpretation of U, Th, and rare earth element mineralization of the Bokan Mountain peralkaline granite complex, Prince of Wales Island, southeast Alaska (in Interpretation and integration of gravity and magnetic data, Ran Zhang (prefacer), Rao Yalamanchili (prefacer) and Alan Aitken (prefacer))
Interpretation (Tulsa) (November 2014) 2 (4): SJ47-SJ63

Abstract

A prospectivity map for rare earth element (REE) mineralization at the Bokan Mountain peralkaline granite complex, Prince of Wales Island, southeastern Alaska, was calculated from high-resolution airborne gamma-ray data. The map displays areas with similar radioelement concentrations as those over the Dotson REE-vein-dike system, which is characterized by moderately high %K, eU, and eTh (%K, percent potassium; eU, equivalent parts per million uranium; and eTh, equivalent parts per million thorium). Gamma-ray concentrations of rocks that share a similar range as those over the Dotson zone are inferred to locate high concentrations of REE-bearing minerals. An approximately 1300-m-long prospective tract corresponds to shallowly exposed locations of the Dotson zone. Prospective areas of REE mineralization also occur in continuous swaths along the outer edge of the pluton, over known but undeveloped REE occurrences, and within discrete regions in the older Paleozoic country rocks. Detailed mineralogical examinations of samples from the Dotson zone provide a means to understand the possible causes of the airborne Th and U anomalies and their relation to REE minerals. Thorium is sited primarily in thorite. Uranium also occurs in thorite and in a complex suite of + or -Ti+ or -Nb+ or -Y oxide minerals, which include fergusonite, polycrase, and aeschynite. These oxides, along with Y-silicates, are the chief heavy REE (HREE)-bearing minerals. Hence, the eU anomalies, in particular, may indicate other occurrences of similar HREE-enrichment. Uranium and Th chemistry along the Dotson zone showed elevated U and total REEs east of the Camp Creek fault, which suggested the potential for increased HREEs based on their association with U-oxide minerals. A uranium prospectivity map, based on signatures present over the Ross-Adams mine area, was characterized by extremely high radioelement values. Known uranium deposits were identified in the U-prospectivity map, but the largest tract occurs over a radioelement-rich granite phase within the pluton that is likely not related to mineralization. Neither mineralization type displays a well-defined airborne magnetic signature.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 2
Serial Issue: 4
Title: Geophysical interpretation of U, Th, and rare earth element mineralization of the Bokan Mountain peralkaline granite complex, Prince of Wales Island, southeast Alaska
Title: Interpretation and integration of gravity and magnetic data
Author(s): McCafferty, Anne E.Stoeser, Douglas B.Van Gosen, Bradley S.
Author(s): Zhang, Ranprefacer
Author(s): Yalamanchili, Raoprefacer
Author(s): Aitken, Alanprefacer
Affiliation: U. S. Geological Survey, Denver, CO, United States
Affiliation: BHP Billiton, London, United Kingdom
Pages: SJ47-SJ63
Published: 20141101
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 82
Accession Number: 2015-007669
Categories: Economic geology, geology of ore depositsApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
N54°40'00" - N56°19'60", W133°30'00" - W132°00'00"
Secondary Affiliation: CGG GravMag Solutions, USA, United StatesUniversity of Western Australia, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201504
Program Name: USGSOPNon-USGS publications with USGS authors
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