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Geochemistry and mineralogy of the Dotson Zone HREE deposit in the Bokan Mountain peralkaline igneous complex, southeastern Alaska, USA

December 1, 2017

The Bokan Mountain igneous complex (BMIC) is a typical example of a peralkaline intrusive system that has evolved to the point of developing late stage HFSE- and REE-rich silicic pegmatites and dikes. The Dotson Zone comprises a series of felsic dikes that extend from the southeast margin of the composite pluton and may represent an important resource of critical HREEs. Petrographically, the primary igneous mineral assemblage is altered by late-igneous and hydrothermal fluids resulting in redistribution and enrichment of REEs. An area of flexure in the southeastern end of the Dotson Zone was the primary locus of enrichment as shown by the pervasive alteration and consistently high REE+Y values. We favor a model in which the dikes were emplaced concurrently with the marginal intrusions, and then altered during emplacement of the inner, main intrusion in a relatively rapid series of overlapping intrusive and late magmatic fluid-high temperature hydrothermal events as the complex cooled. A much later sodic intrusive event focused on the BMIC may have resulted in additional silica-Na-Zr-rich alteration in proximity to the pluton.

Citation Information

Publication Year 2017
Title Geochemistry and mineralogy of the Dotson Zone HREE deposit in the Bokan Mountain peralkaline igneous complex, southeastern Alaska, USA
DOI
Authors Cliff D. Taylor, Heather A. Lowers, David Adams, R. James Robinson
Publication Type Conference Paper
Publication Subtype Conference Paper
Series Title
Series Number
Index ID 70193352
Record Source USGS Publications Warehouse
USGS Organization Central Mineral and Environmental Resources Science Center