scholarly journals EVALUATING MINE-WASTE SEEPAGE WATER AND SOLUTE SOURCES USING STABLE ISOTOPES AND INVERSE GEOCHEMICAL MODELING

2018 ◽  
Author(s):  
Connor P. Newman ◽  
◽  
Jeff Mann
Keyword(s):  
Stable Isotopes ◽  
Mine Waste ◽  
Geochemical Modeling ◽  
Seepage Water ◽  
Inverse Geochemical Modeling

scholarly journals Geochemical Controls on Uranium Release from Neutral-pH Rock Drainage Produced by Weathering of Granite, Gneiss, and Schist

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1104
Author(s):  
Elliott K. Skierszkan ◽  
John W. Dockrey ◽  
K. Ulrich Mayer ◽  
Viorica F. Bondici ◽  
Joyce M. McBeth ◽  
...  
Keyword(s):  
Calcium Release ◽  
Solid Phase ◽  
Mine Waste ◽  
Geochemical Modeling ◽  
Uranium Content ◽  
Sulfide Mineral ◽  
Waste Rock ◽  
Neutral Ph ◽  
Sequencing Experiment ◽  
Aqueous Complexes

We investigated geochemical processes controlling uranium release in neutral-pH (pH ≥ 6) rock drainage (NRD) at a prospective gold deposit hosted in granite, schist, and gneiss. Although uranium is not an economic target at this deposit, it is present in the host rock at a median abundance of 3.7 µg/g, i.e., above the average uranium content of the Earth’s crust. Field bin and column waste-rock weathering experiments using gneiss and schist mine waste rock produced circumneutral-pH (7.6 to 8.4) and high-alkalinity (41 to 499 mg/L as CaCO3) drainage, while granite produced drainage with lower pH (pH 4.7 to >8) and lower alkalinity (<10 to 210 mg/L as CaCO3). In all instances, U release was associated with calcium release and formation of weakly sorbing calcium-carbonato-uranyl aqueous complexes. This process accounted for the higher release of uranium from carbonate-bearing gneiss and schist than from granite despite the latter’s higher solid-phase uranium content. In addition, unweathered carbonate-bearing rocks having a higher sulfide-mineral content released more uranium than their oxidized counterparts because sulfuric acid produced during sulfide-mineral oxidation promoted dissolution of carbonate minerals, release of calcium, and formation of calcium-carbonato-uranyl aqueous complexes. Substantial uranium attenuation occurred during a sequencing experiment involving application of uranium-rich gneiss drainage into columns containing Fe-oxide rich schist. Geochemical modeling indicated that uranium attenuation in the sequencing experiment could be explained through surface complexation and that this process is highly sensitive to dissolved calcium concentrations and pCO2 under NRD conditions.

scholarly journals The origin of the Moon’s Earth-like tungsten isotopic composition from dynamical and geochemical modeling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Rebecca A. Fischer ◽  
Nicholas G. Zube ◽  
Francis Nimmo
Keyword(s):  
Stable Isotopes ◽  
Isotopic Composition ◽  
Geochemical Modeling ◽  
Joint Probability ◽  
The Moon ◽  
Canonical Models ◽  
Giant Impact ◽  
The Earth ◽  
Isotopic Evolution ◽  
Low Probability

AbstractThe Earth and Moon have identical or very similar isotopic compositions for many elements, including tungsten. However, canonical models of the Moon-forming impact predict that the Moon should be made mostly of material from the impactor, Theia. Here we evaluate the probability of the Moon inheriting its Earth-like tungsten isotopes from Theia in the canonical giant impact scenario, using 242 N-body models of planetary accretion and tracking tungsten isotopic evolution, and find that this probability is <1.6–4.7%. Mixing in up to 30% terrestrial materials increases this probability, but it remains <10%. Achieving similarity in stable isotopes is also a low-probability outcome, and is controlled by different mechanisms than tungsten. The Moon’s stable isotopes and tungsten isotopic composition are anticorrelated due to redox effects, lowering the joint probability to significantly less than 0.08–0.4%. We therefore conclude that alternate explanations for the Moon’s isotopic composition are likely more plausible.

Long Term Zinc Contamination and Transport at the Abandoned Ore Chimney Mine

2020 ◽  
Author(s):  
Colleen Harper ◽  
Carling Ruth Walsh ◽  
Carrie Fong ◽  
Paul Gammon ◽  
Richard T Amos
Keyword(s):  
Natural Attenuation ◽  
Mine Drainage ◽  
Mine Waste ◽  
Geochemical Modeling ◽  
Waste Rock ◽  
Ph Buffering ◽  
Mine Waste Rock ◽  
Site Water ◽  
Waste Rock Piles ◽  
Co Precipitation

Mine waste-rock piles can release low quality drainage that is harmful to the surrounding environment. Many studies have investigated recently placed waste rock, but fewer have examined geochemical processes within, and downgradient of, old waste rock, even though these processes may be expected to persist for many decades. The Ore Chimney property was the site of gold exploration activities that produced a small waste-rock pile; it was abandoned in 1934. Elevated concentrations of Zn are restricted to within 50 m of the waste rock, and pH remains neutral across the site. Water and sediment analyses and geochemical modeling indicate that several processes are involved in pH buffering and contaminant control. Water samples taken at the edge of the waste rock were not acidic, indicating that mechanisms within the waste rock, including carbonate buffering and preferential oxidation of sphalerite over pyrite, are preventing Acid Mine Drainage (AMD). Natural attenuation mechanisms are operating within wetlands at Ore Chimney with the most likely controls for Zn transport in ground and surface water being carbonate mineral precipitation, co-precipitation with Fe and Mn oxides and oxyhydroxide minerals and Al sulphate minerals, and adsorption onto calcite and organic matter. This investigation shows that, after long time frames, natural attenuation mechanisms may act to effectively immobilize metal contaminants.

scholarly journals Hydrochemical Formation Mechanisms and Quality Assessment of Groundwater with Improved TOPSIS Method in Pengyang County Northwest China

2011 ◽  
Vol 8 (3) ◽  
pp. 1164-1173 ◽  
Author(s):  
Li Peiyue ◽  
Qian Hui ◽  
Wu Jianhua
Keyword(s):  
Quality Assessment ◽  
Cation Exchange ◽  
Geochemical Modeling ◽  
Northwest China ◽  
Human Consumption ◽  
Formation Mechanisms ◽  
Topsis Method ◽  
Entropy Weight ◽  
Sodium Montmorillonite ◽  
Inverse Geochemical Modeling

Inverse geochemical modeling was used in this paper to quantitatively study the formation mechanisms of groundwater in Pengyang County, China. An improved TOPSIS method based on entropy weight was used to perform groundwater quality assessment in this area. The assessment results show that the groundwater in the study area is fit for human consumption and the high concentrations of some elements can be attributed to the strong water-rock interactions. The inverse geochemical modeling reveals that the dominant reactions in different parts of the study area are different. In the south part of the study area, the precipitation of sodium montmorillonite, calcite and the dissolution of gypsum, fluorite, halite, albite and dolomite as well as CO2dissolution and cation exchange are the major water-rock interactions, while in the north part, the leading reactions are the precipitation of gypsum, dolomite, sodium montmorillonite, fluorite, the dissolution of calcite and albite and the CO2emission and cation exchange are also important. All these reactions are influenced by the initial aquatic environment and hydrodynamic conditions of the flow path.

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