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Natural versus anthropogenic dispersion of metals to the environment in the Wulik River area, western Brooks Range, Northern Alaska

Karen D. Kelley and Travis Hudson
Natural versus anthropogenic dispersion of metals to the environment in the Wulik River area, western Brooks Range, Northern Alaska
Geochemistry - Exploration, Environment, Analysis (February 2007) 7 (1): 87-96

Abstract

Zinc-lead-silver mineral deposits in the Wulik River region, Alaska, contain an enormous accumulation of Zn. In addition to the giant deposits at Red Dog, at least nine other deposits are known. Natural weathering of these deposits has dispersed metals over a wide region over a long period of time (c. 10 000 years) through transport by stream and groundwater, stream sediments, formation of soils, and perhaps wind-blown atmospheric deposition from weathering of naturally enriched Pb-Zn surface deposits. Anthropogenic input also contributes metals to the environment. Mining of the Red Dog deposit, which began in 1989, produces fine-grained galena and sphalerite concentrates that are transported from the mine site by truck to a storage port facility. Wind-blown dispersion of concentrate dust along the road and around the port facility has been a source of local metal-rich surficial materials. Geochemical and mineralogical characteristics provide a means of distinguishing the natural versus anthropogenic metal sources. Soils over deposits have patterns of increasing metal contents with depth and proximity to the metal-bearing source, whereas ore concentrate dust is localized at the surface. The acidity produced by weathering of the sulphide deposits creates an environment in which elements such as Se and Mo are stable whereas Ca is not. Consequently, high Mo (up to 29 ppm) and Se (up to 17 ppm) and low Ca (<0.4%) concentrations characterize surficial materials near natural deposits. Acidic conditions also yield high Pb-Zn ratios (up to 70) because sphalerite is preferentially dissolved and Zn is mobilized during chemical weathering. In natural materials, secondary jarosite and anglesite are developed, and minor galena is etched and rounded due to a history of chemical and mechanical weathering. In contrast, dust-bearing samples have Pb/Zn ratios that are 0.4 or less, Ca contents are higher (0.2 to 3.6%), and Mo (<10 ppm) and Se (not detected) concentrations are low. Furthermore, galena and sphalerite grains are angular and secondary minerals are lacking.


ISSN: 1467-7873
EISSN: 2041-4943
Serial Title: Geochemistry - Exploration, Environment, Analysis
Serial Volume: 7
Serial Issue: 1
Title: Natural versus anthropogenic dispersion of metals to the environment in the Wulik River area, western Brooks Range, Northern Alaska
Affiliation: U. S. Geological Survey, Denver, CO, United States
Pages: 87-96
Published: 200702
Text Language: English
Publisher: Geological Society Publishing House, London, United Kingdom
References: 41
Accession Number: 2007-010855
Categories: Environmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch map
N67°49'60" - N68°10'00", W163°30'00" - W163°00'00"
Secondary Affiliation: Applied Geology, USA, United States
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: 200707
Program Name: USGSOPNon-USGS publications with USGS authors
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