Geochemical Evolution of a High Arsenic, Alkaline Pit-Lake in the Mother Lode Gold District, California

Savage, Kaye S.; Ashley, Roger P.; Bird, Dennis K.

doi:10.2113/gsecongeo.104.8.1171

Cited by 18 publications

(7 citation statements)

References 39 publications

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“…Because of the CO 2 -free deionized water used in the column experiments as well as the relatively slow dissolution of CO 2 into water especially under ambient conditions with low partial pressure of CO 2 (P CO2 ≤ 10 -3.5 atm) (Liu and Dreybrodt, 1997), the rate of consumption of dissolved CO 2 in the pore water during calcite dissolution was faster than the rate at which it was replenished, resulting in a closed system type. The importance of dissolved CO 2 on the evolution of pH in an actual field setting (i.e., a mine pit lake in contact with altered rocks) was also pointed out by Savage et al (2009). In addition, lower pH in columns with longer water residence time could be attributed to higher concentration of dissolved O 2 in the pore water that could increase pyrite oxidation leading to the generation of more acidity in the rock-water system.…”

Section: Mineral Dissolution Pyrite Oxidation Precipitation and Ph mentioning

confidence: 90%

“…Also, several authors have studied the evolution of toxic elements including As and heavy metals from mine pit lakes that are in contact with hydrothermally altered rock (Davis and Ashenberg, 1989;Davis et al, 2006;Eary, 1998;Levy et al, 1997;Savage et al, 2009;Tempel et al, 2000), but studies regarding the leaching behavior and release mechanisms of As from excavated altered rocks and the parameters that control these mechanisms are still lacking in the 4 literature. Understanding of these release and speciation mechanisms is essential in the development of any engineered countermeasures that would minimize As mobilization from altered rocks.…”

Section: Introductionmentioning

confidence: 99%

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Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

Tabelin

Igarashi

Takahashi

2012

Applied Geochemistry

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This paper describes the mobilization and speciation of arsenic (As) found in hydrothermally altered rock under oxic column conditions. The altered rock sample was obtained from a tunnel project located in the Nakakoshi area of Hokkaido, Japan, whose geology is represented by slate, shale and sandstone. This area underwent silicification, pyritization and argillic alteration resulting in the As-enrichment of the rock.Results of the column experiments show that the infiltration rate, bulk density and rock bed thickness affected the duration of water residence, which in turn influenced the pH of the rock-water system. Coexisting ions most notably calcium (Ca 2+) at amounts greater than ca. 50 mg/L retarded the mobilization of As. Mobilization of As from the rock with time occurred in two stages: stage 1 (weeks 1 -20) with higher As leaching and stage 2 (weeks 20 -76) characterized by nearly constant As release. In addition, pore water As concentrations revealed that the columns developed into two regions: the top half where most of the leaching occurred and the bottom part dominated by adsorption. Thus, the mechanisms controlling the mobilization of As from the rock is a combination of one or more of the following processes: dissolution of soluble As-bearing fractions, pyrite oxidation and adsorption reactions. Arsenite (As [III]) was the dominant species in the effluent at the start of the experiment in columns with shorter water residence time and lower pH conditions (< 8). On the other hand, arsenate (As[V]) was the major inorganic species released from the rock at higher pH (8 -9.5) and when the system was close to equilibrium. Speciation of As with depth also indicated that As[III] disappeared around the bottom half of the columns, probably as a result of adsorption and/or oxidation. Arsenic speciation is partially controlled by the pH dependent adsorption of As species. The important adsorbent phases in the rock included Fe-Al oxides/oxyhydroxides, clay minerals and organic matter, which permitted the columns to attenuate additional As loadings including As [III]. Implications of these results on the design of a novel disposal method for these altered rocks include the enhancement of As adsorption through the addition of natural or artificial adsorbents and the utilization of a covering soil with low permeability to minimize rainwater infiltration into the rock.

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Section: Mineral Dissolution Pyrite Oxidation Precipitation and Ph mentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

Tabelin

Igarashi

Takahashi

2012

Applied Geochemistry

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“…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). …”

Section: Integrated Assessmentmentioning

confidence: 98%

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

Parra

Oyarzún

Maturana

et al. 2010

Environ Monit Assess

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This contribution analyzes water chemical data for the Choapa basin, North Central Chile, for the period 1980-2004. The parameters considered are As, Cu Fe, pH, EC, SO₄⁻², Cl⁻¹, and HCO[Formula: see text], from samples taken in nine monitoring stations throughout the basin. Results show rather moderate contents of As, Cu, and Fe, with the exception of the Cuncumén River and the Aucó creek, explained by the influence of the huge porphyry copper deposit of Los Pelambres and by the presence of mining operations, respectively. When compared against results obtained in previous researches at the neighboring Elqui river basin, which host the El Indio Au-Cu-As district, a much reduced grade of pollution is recognized for the Choapa basin. Considering the effect of acid rock drainage (ARD)-related Cu contents on the fine fraction of the sediments of both river basins, the differences recorded are even more striking. Although the Los Pelambres porphyry copper deposit, on the headwaters of the Choapa river basin, is between one and two orders of magnitude bigger than El Indio, stream water and sediments of the former exhibit significantly lower copper contents than those of the latter. A main factor which may explain these results is the smaller degree of H( + )-metasomatism on the host rocks of the Los Pelambres deposit, where mafic andesitic volcanic rocks presenting propylitic hydrothermal alteration are dominant. This fact contrast with the highly altered host rocks of El Indio district, where most of them have lost their potential to neutralize ARD.

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“…The drainage geochemistry of orogenic gold deposits has been studied at mines in the Mother Lode district of California (Savage et al, 2000(Savage et al, , 2009, Alaska (Goldfarb et al, 1997;Verplanck et al, 2008;Torrance et al, 2012) and New Zealand (Craw et al, 2004; http://dx.doi.org/10.1016/j.apgeochem.2014.11.015 0883-2927/Crown Copyright Ó 2014 Published by Elsevier Ltd. All rights reserved. Haffert and Craw, 2008;Druzbicka and Craw, 2013).…”

Section: Introductionmentioning

confidence: 99%

Arsenic mobility in mildly alkaline drainage from an orogenic lode gold deposit, Bralorne mine, British Columbia

Desbarats

Parsons

Percival

2015

Applied Geochemistry

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Geochemical Evolution of a High Arsenic, Alkaline Pit-Lake in the Mother Lode Gold District, California

Cited by 18 publications

References 39 publications

Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

Mobilization and speciation of arsenic from hydrothermally altered rock in laboratory column experiments under ambient conditions

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

Arsenic mobility in mildly alkaline drainage from an orogenic lode gold deposit, Bralorne mine, British Columbia

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