Geochemistry and Stable Isotopes of the Flooded Underground Mine Workings of Butte, Montana

Abstract

Over a century of mining and smelting of the world-class porphyry lode ore deposit at Butte, Montana, has resulted in extensive environmental damage. In addition to its being the location of one of the world's largest and most acidic mining pit lakes, Butte is host to over 16,000 km of flooded underground mine workings. Of the more than 60 mine shafts that have historically operated in Butte, approximately one dozen are presently accessible for groundwater sampling. The geochemistry of the mine shaft waters is zoned and roughly coincides with a district-wide zonation in hydrothermal alteration and mineralization. Mine waters in the so-called "Central zone" of intense phyllic and advanced argillic alteration have lower pH and very high concentrations of As, Fe, Mn, and Zn, but very low concentrations of dissolved Cu. The scarcity of Cu is attributed to cementation onto scrap iron left in the mines, and/or to replacement of preexisting sulfide minerals below the water table in a manner analogous to supergene enrichment processes. At the other extreme, mine waters in the "Peripheral zone" of weakest alteration have near-neutral pH, low metal concentrations, and contain dissolved sulfide (H2S, HS -). These waters are close to equilibrium with calcite, siderite, crystalline or amorphous MnCO3, and mackinawite (poorly crystalline FeS). A suite of deep groundwater monitoring wells completed †

Natural factors and mining activity bearings on the water quality of the Choapa basin, North Central Chile: insights on the role of mafic volcanic rocks in the buffering of the acid drainage process

“…However, this buffer property is destroyed by advanced hydrothermal alteration, as occurs in the El Indio district. This principle has been recently illustrated by the case of the development of an alkaline-rich lake in pyrite-rich rocks, but affected by Na metasomatism, in the Mother Lode Gold District in California (Savage et al 2009), and by the fact that the higher rate of ARD generation in the Butte-Montana District is related to the zone of advanced argillic alteration (Gammons et al 2009). …”

Sources, migration and transformation of antimony contamination in the water environment of Xikuangshan, China: Evidence from geochemical and stable isotope (S, Sr) signatures

“…Sulfur ( 34 S) and strontium ( 87 Sr) isotopes have been widely used in coal and multi-metal mining processes to investigate environmental contamination problems in water, soil and air (de Caritat et al, 2005;Dogramaci and Herczeg, 2002;Gammons et al, 2013;Gammons et al, 2010;Gammons et al, 2009). Sulfate has a wide range of stable isotope compositions in natural waters.…”

Influence of Copper Recovery on the Water Quality of the Acidic Berkeley Pit Lake, Montana, U.S.A.

“…The Berkeley Pit lake (Figure A), located in the city of Butte, Montana, U.S.A., is one of the largest accumulations of toxic mine water in the world. The lake formed after mining of a large, open-pit porphyry Cu deposit ceased. , The geochemistry and limnology of the Berkeley Pit lake have been summarized by numerous authors − although its characteristics are somewhat of a moving target given the complex history of filling and management. , The lake is approximately 235 m deep and contains an estimated 1.65 × 10 11 liters (as of May, 2014) of highly acidic (pH 2.6 ± 0.2) metal-rich water. The lake has no surface outlet, and continues to fill at a rate of roughly 1.9 × 10 7 L/day.…”