Crustal Geophysics and Geochemistry Science Center

Modeling Near-Surface Processes in Mineral Systems

Task 5.3: Predictive Modeling and Field Applications using Trace Element Partitioning, Reaction Rate Data, and Microbial Studies

Task Objectives

Our objective in this task were to demonstrate the usefulness and application of our experimental results in studies of real-world situations involving mineral-environmental issues. This task focused on sulfide oxidation, acid mine drainage, and metal fluxes in geologically and climatically diverse natural settings.

Studies were carried out in transitional marine settings, in acid mine drainage systems, and in pit lakes. Overall objectives were to relate our experimental results to real natural setting.

Highlights & Key Findings

Combined onshore and offshore field studies in coastal areas of eastern Prince William Sound during June, 2003 and 2005, investigated the distribution and oxidation characteristics of sulfide-rich rock debris related to early 20th century mining activity.

These were the first studies of the environmental effects of oxidizing sulfides within intertidal environments of Prince William Sound. Our findings indicate that acidic water laden with potentially toxic metals are generated intertidal sulfide waste during tidal cycles. The acidic fluids are enriched in numerous metals including Fe, Al, Ba, Tl, Ag, Cd, Co, Ni, Mn, Mn, Pb, Zn, and Hg. The apparent extent of these acid waters and flux of metals is surprising given the buffering capacity of seawater. Elevated Hg in interstitial waters of the intertidal zone is also unexpected in that the massive-sulfide deposits have no known mercury minerals. Precipitates formed from these acidic fluids are enriched in a similar suite of metals plus As and W. Together, these sites represent an opportunity to learn more about sulfide oxidation, fluid flow, and contaminant distribution in this dynamic marine environment. The results have implications for past and future mining activities along coastal zones of the Pacific Northwest and the disposal of mine tailings in shallow marine settings.

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