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GEOREF RECORD

Environmental geochemistry at Red Mountain, an unmined volcanogenic massive sulphide deposit in the Bonnifield district, Alaska Range, east-central Alaska

Robert G. Eppinger, Paul H. Briggs, Cynthia Dusel-Bacon, Stuart A. Giles, Larry P. Gough, Jane M. Hammarstrom and Bernard E. Hubbard
Environmental geochemistry at Red Mountain, an unmined volcanogenic massive sulphide deposit in the Bonnifield district, Alaska Range, east-central Alaska
Geochemistry - Exploration, Environment, Analysis (August 2007) 7 (3): 207-223

Abstract

The unmined, pyrite-rich Red Mountain (Dry Creek) deposit displays a remarkable environmental footprint of natural acid generation, high metal and exceedingly high rare earth element (REE) concentrations in surface waters. The volcanogenic massive sulphide deposit exhibits well-constrained examples of acid-generating, metal-leaching, metal-precipitation and self-mitigation (via co-precipitation, dilution and neutralization) processes that occur in an undisturbed natural setting, a rare occurrence in North America. Oxidative dissolution of pyrite and associated secondary reactions under near-surface oxidizing conditions are the primary causes for the acid generation and metal leaching. The deposit is hosted in Devonian to Mississippian felsic metavolcanic rocks of the Mystic Creek Member of the Totatlanika Schist. Water samples with the lowest pH (many below 3.5), highest specific conductance (commonly >2500 mu S/cm) and highest major- and trace-element concentrations are from springs and streams within the quartz-sericite-pyrite alteration zone. Aluminum, Cd, Co, Cu, Fe, Mn, Ni, Pb, Y, Zn and, particularly, the REEs are found in high concentrations, ranging across four orders of magnitude. Waters collected upstream from the alteration zone have near-neutral pH, lower specific conductance (370 to 830 mu S/cm), lower metal concentrations and measurable alkalinities. Water samples collected downstream of the alteration zone have pH and metal concentrations intermediate between these two extremes. Stream sediments are anomalous in Zn, Pb, S, Fe, Cu, As, Co, Sb and Cd relative to local and regional background abundances. Red Mountain Creek and its tributaries do not, and probably never have, supported significant aquatic life.


ISSN: 1467-7873
EISSN: 2041-4943
Serial Title: Geochemistry - Exploration, Environment, Analysis
Serial Volume: 7
Serial Issue: 3
Title: Environmental geochemistry at Red Mountain, an unmined volcanogenic massive sulphide deposit in the Bonnifield district, Alaska Range, east-central Alaska
Affiliation: U. S. Geological Survey, Denver, CO, United States
Pages: 207-223
Published: 200708
Text Language: English
Publisher: Geological Society Publishing House, London, United Kingdom
References: 75
Accession Number: 2007-087710
Categories: HydrochemistryEnvironmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch map
N63°53'60" - N63°57'00", W147°25'60" - W147°18'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200739
Program Name: USGSOPNon-USGS publications with USGS authors
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