bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting mineral weathering rates at field scale for mine water risk assessment
Authors: Banwart Steven A. , Evans Katherine A. , Croxford Stephanie 
Published: April 2008

Abstract
A general challenge to the environmental management of mine sites is the relatively high costs of site investigation and the associated development of conceptual site models and parameterization of reactive transport models. A particular problem is the inability to predict at field scale the rates of processes that give rise to long-term dissolved contamination due to active sulphide mineral weathering. Mineral weathering rates determined from laboratory and field observations generally do not agree, often exhibiting a discrepancy of two-three orders of magnitude.
Recent work on mine waste deposits has demonstrated that this discrepancy can be explained by considering a small number of bulk physical and chemical properties of mine rock at field sites. The apparent decrease in mass-normalized rates between bench-scale batch reactors and pilot-scale column reactors is predicted by accounting for differences in temperature, where lower temperatures in the column reactors reduced reaction rates due to activation energy effects. The columns also contain a significantly greater mass fraction of larger particles that have lower specific surface area and, thus, exhibit lower weathering rates.
The further apparent decrease in rates between the column reactors and field scale is predicted by additionally accounting for the spatial variability of sulphide-bearing rock at the site, which gives rise to only localized weathering. Localized zones of sulphide weathering are also associated with locally active weathering of silicate minerals due to lower pH. Hydrological factors are also important due to preferential flow within the field site, whereby a fraction of dissolved weathering products are retained within immobile water and do not reach the effluent stream, where ion mass flows resulting from weathering reactions are determined. These results suggest that application of compiled laboratory data to prediction of weathering rates at mine sites may be feasible. This is potentially valuable for application to Tier 1 risk assessment of mine sites, where reliable prediction of weathering rates from tabulated laboratory data would provide significant information to support the generally sparse datasets that are available, particularly for orphan mine sites.
The importance of pyritic roof strata in aquatic pollutant release from abandoned mines in a major, oolitic, berthierine-chamosite-siderite iron ore field, Cleveland, UK
Authors: Younger Paul L. 
Published: April 2008

Abstract

The Cleveland Ironstone Field (NE England) is a major sedimentary iron orefield in which the principal ore minerals are iron silicates (berthierine, chamosite) and carbonates (siderite). The siderite in this area is known to be rich in Mg and Mn in solid solution with Fe. Although this ore assemblage would not normally be expected to give rise to acid mine drainage phenomena, a number of discrete ferruginous mine water discharges (totalling some 6.5 million litres (Ml) day
−1
) have been identified flowing from abandoned underground mine workings and old spoil heaps in the ore field. Some of these discharges are extremely acidic (pH ≥ 3.3), with total Fe reaching 1220 mg l
−1
. At the point of first emergence to the surface, most of the discharges are so highly charged with dissolved CO
2
that they effervesce. Upon degassing, one of the discharges precipitates a ferroan calcite deposit, which is most unusual as a mine water discharge precipitate. All the other discharges precipitate more usual ferrihydrite and goethite ‘ochres’. The geochemistry of these waters supports the view that oxidation of pyrite in the roof strata initiates dissolution of siderite in the old workings, releasing CO
2
, Fe and Mg to solution. This chain of reactions results in these waters having SO
2−
4
as their major anion (from pyrite weathering) with Mg as the major cation (except where Fe exceeds Mg in concentration). Two of the near-coastal discharges have Na as the major cation, and elevated Cl concentrations, suggesting a sea-water component. However, SO
4
/Cl ratios suggest that sea water can account for no more than 20% of these waters. Most of the Cleveland mine waters have significant environmental impacts, ranging from ecological damage to receiving water courses to flooding problems caused by the clogging of surface sewers with mine water precipitates. A range of remedial measures are proposed.
Arsenic removal by oxidizing bacteria in a heavily arsenic-contaminated acid mine drainage system (Carnoulès, France)
Authors: Leblanc Marc , Casiot Corinne , Elbaz-Poulichet Françoise , Personné Christian 
Published: April 2008

Abstract

In the Carnoulès Pb-Zn mining site (Gard, France), abandoned 40 years ago, acidic waters (pH 3) with an extremely high As content (80–350 mgl
−1
) emerge from the base of a tailings stock containing As-rich pyrite (2–4% As). From the acidic spring, the oxidation — reduction potential (Eh) and O
2
parameters strongly increase within a few metres and a Fe-As-rich (up to 22% As) material precipitates and covers the bed of the acidic creek. Consequently, there is a sharp decrease in arsenic concentration of the acidic waters downflow (<10 mgl
−1
As) and of the Fe-rich precipitates (down to 2% As). Seasonal variations in dissolved arsenic concentrations of the spring waters are important. Furthermore, the Fe-As-rich stream sediments that were stored, during drought periods, are reworked and transported downflow during rainy periods. The annual fluxes of total arsenic comprise between 2 and 6 t; the lifetime of the As-releasing system is that of several centuries.

Fe and As speciation measurements have been carried out. Fe(II) and As(III) dominate all along the acidic stream. Fe(III) is rapidly precipitated. The removal of total dissolved arsenic mostly corresponds to a decrease in dissolved As(III) and results in the formation of As-rich ferric precipitates. A further decrease in arsenic concentration in water can be attributed to adsorption mechanisms on ferric hydroxides.

In the Fe-As-rich products, the most common bacteria are long rod-shaped phenotypes of the genus
Thiobacillus ferooxidans
. Laboratory experiments have been carried out to investigate the potential catalytic role of these acidophilic oxidizing bacteria on the removal of arsenic: in the biotic systems, 60–80% As were removed in a few days against 5% for abiotic systems.
Fingerprinting mine water in the eastern sector of the South Wales Coalfield
Authors: Brown M. M. E. , Jones A. L. , Leighfield K. G. , Cox S. J. 
Published: April 2008

Abstract
Coal has been mined in the South Wales Coalfield for centuries. Substantial dewatering operations have attended these activities, particularly with the advent of steam and electric pumps that facilitated deeper mining operations. However, underground coal mining in South Wales has been in decline since 1913. The closure of the last deep mine in the eastern part of the coalfield in 1992 entailed a cessation of pumping over a large geographical area, with a resultant recovery of the groundwater. A consequence of this recovery is that emissions of mine water are occurring at the surface.
Surface water emissions of known provenance from the Upper Coal Measures were sampled in 2000 and characterized in terms of their major ion composition. Also, known emissions of mine water within the catchments of the Rivers Ebbw, Ebbw Fach, Rhymney and Taff Bargoed were sampled, and the major ion data plotted on trilinear Piper diagrams. The results indicate that two distinctive hydrochemical facies could be identified from these plots. By combining knowledge of the underground mine workings and lithology, and by comparison with the Upper Coal Measures ‘fingerprint’, it is possible to divide the mine water emissions into those sourced from the Upper and Middle and Lower Coal Measures, and at times to infer a degree of mixing between the two.
The conclusion is that in the eastern valleys of the South Wales Coalfield, the Upper Coal Measures water has a calcium-sulphate facies and the Middle and Lower Coal Measures water has a sodium-sulphate to sodium-bicarbonate facies. This information can be added to the available knowledge to aid in assessing the nature and the progress of groundwater recovery within the coalfield.
This paper refers to preliminary work that has been carried out in the South Wales Coalfield to attempt to ‘fingerprint’ mine water emissions to identify their underground source. This, in turn, provides valuable information on the hydrogeological regime and, coupled with the geological and mining setting, may further assist in identifying underground flow paths. This information helps to fill in some of the ‘knowledge gaps’ and provide a tool for use in the prediction of future surface mine water emissions and in the formulation of treatment-mitigation strategies. The current work uses observations and interpretations of the hydrochemistry of the coal Measures to develop a robust and simple to use method of characterizing and classifying mine water emissions within the South Wales Coalfield. It is anticipated that a similar interpretive process could be applied to mine water emissions in other coalfields, although it should be stressed that this cannot be considered as a ‘stand alone’ process and that the initial characterization of the mine water needs to be carried out with reference to the geological and mining setting for any particular area under consideration.
Alkaline mine drainage from metal sulphide and coal mines: examples from Svalbard and Siberia
Authors: Banks David , Parnachev Valery P. , Frengstad Bjørn , Holden Wayne , Vedernikov Anatoly A. , Karnachuk Olga V. 
Published: April 2008

Abstract
Not all water from coal or metal mines is acidic. Circum-neutral or alkaline mine drainage may be due to: (i) a low content of sulphide minerals; (ii) the presence of monosulphides rather than pyrite or marcasite; (iii) a large pyrite grain-size limiting oxidation rate; (iv) neutralization of acid by carbonate or basic silicate minerals; (v) engineering factors (introduction of lime dust for explosion prevention; cement or rock flour during construction works); (vi) neutralization of acid by naturally highly alkaline groundwaters; (vii) circulating water not coming into effective contact with sulphide minerals; and (viii) oxygen not coming into direct contact with sulphide minerals or influent water being highly reducing.
Assessment, prediction and management of long-term post-closure water quality: a case study — Hlobane Colliery, South Africa
Authors: Hattingh R. P. , Pulles W. , Krantz R. , Pretorius C. , Swart S. 
Published: April 2008

Abstract
Hlobane Colliery, located in the Vryheid Coalfields of South Africa, is to close down its operations after more than a century of mining activities. This paper presents a review of the assessments that were undertaken in order to determine the long-term water quality risks after mine closure and evaluate the effects of various water management actions thereon. An integrated assessment approach was adopted that incorporated hydrological, hydrogeological, mineralogical and geochemical assessment, and modelling techniques to predict the volumes and qualities of water discharging from various points on the mine for the base case situation where no water management options were implemented. Various water management options were identified that are primarily aimed at preventing the contamination of clean water, and the effects of these strategies were predicted and compared with the base case situation in order to provide a rational basis for the selection of the most appropriate strategies.
Formation and evolution of Archaean cratons: insights from southern Africa
Authors: James D. E. , Fouch M. J. 
Published: April 2008

Abstract

Archaean cratons are the stable remnants of Earth’s early continental lithosphere, and their structure, composition and survival over geological time make them unique features of the Earth’s surface. The Kaapvaal Project of southern Africa was organized around a broadly diverse scientific collaboration to investigate fundamental questions of craton formation and mantle differentiation in the early Earth. The principal aim of the project was to characterize the physical and chemical nature of the crust and mantle of the cratons of southern Africa in geological detail, and to use the 3D seismic and geochemical images of crustal and mantle heterogeneity to reconstruct the assembly history of the cratons. Seismic results confirm that the structure of crust and tectospheric mantle of the cratons differs significantly from that of post-Archaean terranes. Three-dimensional body-wave tomographic images reveal that high-velocity mantle roots extend to depths of at least 200 km, and locally to depths of 250–300 km beneath cratonic terranes. No low-velocity channel has been identified beneath the cratonic root. The Kaapvaal Craton was modified approximately 2.05 Ga by the Bushveld magmatic event, and the mantle beneath the Bushveld Province is characterized by relatively low seismic velocities. The crust beneath undisturbed Archaean craton is relatively thin (
c.
35–40 km), unlayered and characterized by a strong velocity contrast across a sharp Moho, whereas post-Archaean terranes and Archaean regions disrupted by large-scale Proterozoic magmatic or tectonic events are characterized by thicker crust, complex Moho structure and higher seismic velocities in the lower crust. A review of Re-Os depletion model age determinations confirms that the mantle root beneath the cratons is Archaean in age. The data show also that there is no apparent age progression with depth in the mantle keel, indicating that its thickness has not increased over geological time. Both laboratory experiments and geochemical results from eclogite xenoliths suggest that subduction processes played a central role in the formation of Archaean crust, the melt depletion of Archaean mantle and the assembly of early continental lithosphere. Co-ordinated geochronological studies of crustal and mantle xenoliths have revealed that both crust and mantle have experienced a multi-stage history. The lower crust in particular retains a comprehensive record of the tectonothermal evolution of the lithosphere. Analysis of lower-crustal xenoliths has shown that much of the deep craton experienced a dynamic and proteracted history of tectonothermal activity that is temporally associated with events seen in the surface record. Cratonization thus occurred not as a discrete event, but in stages, with final stabilization postdating crustal formation.
The development of lithospheric keels beneath the earliest continents: time constraints using PGE and Re-Os isotope systematics
Authors: Pearson D. G. , Irvine G. J. , Carlson R. W. , Kopylova M. G. , Ionov D. A. 
Published: April 2008

Abstract

Continued studies of xenolith suites found in kimberlites on and around the Kaapvaal Craton, together with those from newly discovered localities on other cratons, are providing new insights into the generation and evolution of the Earth’s oldest continents. Comparison of modal abundance data with melt depletion models, together with trace element and isotope systematics in Kaapvaal low-temperature peridotites, suggest that much or all of the diopside and garnet in these rocks may have formed significantly after initial melt depletion. The Re-Os isotope system has been instrumental in providing an improved understanding of the timing of the formation of cratonic lithospheric keels. New studies that focus on carefully selected whole-rock peridotites and use combined platinum group element (PGE) and Re-Os isotope analysis provide better constraints on the significance of Re-Os model ages. The large database of Re-Os isotope analyses for peridotites for the Kaapvaal Craton indicate formation of significant amounts of lithospheric mantle in Neoarchaean time, associated with voluminous mafic magmatism. Formation of lithospheric mantle in Neoarchean time (3.0–2.5 Ga) follows the cessation of major crustal differentiation events at
c
. 3.1 Ga and marks the onset of craton stabilization. Some lithospheric mantle was produced in Palaeo- to Mesoarchaean time (3.8–3.0 Ga) in southern Africa, which preserved ancient crustal fragments. Large-scale preservation of Archaean continental masses was effective only after the formation of substantial, buoyant, rigid, deep lithospheric keels and their stabilization in Neoarchean time. Formation of lithospheric mantle beneath the surrounding Proterozoic crustal regions occurred in Mesoproterozoic time, with lower degrees of mantle melting than associated with the cratonic peridotites. This circum-cratonic mantle is of similar age to the oldest overlying crust and has been coupled to the margins of the craton since its formation. Major magmatic events, some coincident with the formation of circumcratonic mantle, added new lithosphere to the Kaapvaal mantle root but failed to destroy it. The mechanically strong, buoyant lithospheric keels beneath cratons protect their crust from subduction and recycling over 3 Ga time periods.
Seismic evidence for a mantle source for mid-Proterozoic anorthosites and implications for models of crustal growth
Authors: Musacchio Gemma , Mooney Walter D. 
Published: April 2008

Abstract

Voluminous anorthosite intrusions are common in mid-Proterozoic crust. Historically, two end-member models have been proposed for the origin of these anorthosites. In the first model anorthosites derive from fractionation of a mantle source leaving a residue of metagabbro in the lower crust; in the second model anorthosites are the product of partial melting of the lower crust with residual pyroxene and high-grade minerals (i.e. a pyroxenitic and/or metapelitic lower crust). Although a general consensus has developed that the first model provides the best fit to petrological and geochemical constraints, the sparse evidence for mafic and ultramafic counterparts to the anorthosites leaves the issue still unresolved. We use the absolute P-wave velocity and the ratio between P- and S-wave velocities (
V
P
/
V
S
) to infer the composition of the lower crust beneath the Marcy Anorthosite (New York State, USA). Seismic refraction data reveal a lower crust 20 km thick, where
V
P
and V
P
/V
S
range from top to bottom between 7.0 km s
−1
and 7.2 ± 0.1 and 1.84 km s
−1
and 1.81 ± 0.02, respectively. Laboratory measurements on rock samples indicate that these seismic properties are typical of plagioclase-rich rocks. Magmatic underplating of basaltic melts is a mechanism to form plagioclase-rich bulk composition for the Grenville crust. At the bottom of the lower crust, increase of P-wave velocity, slight decrease of
V
P
/
V
S
ratios and the presence of a low-reflective seismic Moho are additional observations supporting crustmantle interactions related to magmatic underplating. High P-wave velocity (8.6 km s
−1
) in the upper mantle may indicate that the ultramafic portion (e.g. pyroxenites) of the underplated magma has become eclogite. High average P-wave velocity (6.7 km s
−1
) and
V
P
/
V
S
(1.81), and the exceptional abundance of anorthosites-norites-troctolites among the rocks exposed at the surface, indicate that the Grenville Proterozoic crust may have a unique plagioclase-rich bulk composition. We suggest magmatic underplating, occurring either over a wide time span or with separate syn- and post-collisional magmatic pulses, as being a major crust-forming mechanism operating in mid-Proterozoic time.
Neoarchaean tectonic evolution of the Zimbabwe Craton
Authors: Jelsma Hielke A. , Dirks Paul H. G. M. 
Published: April 2008

Abstract

An overview is presented of the field relations, age data and geochemical characteristics of the Neoarchaean granites and greenstones of the Zimbabwe Craton, southern Africa. A major tectono-magmatic event at
c.
2.7 Ga produced two distinct greenstone successions. One succession is reminiscent of rift- or back-arc environments and is associated with an old continental fragment. A second succession is indicative of arc magmatism and is associated with juvenile crust. Both were affected by a major accretionary event that, in an apparent sense, swept across the craton between 2.68 and 2.60 Ga. During this 80 Ma time period, concomitant late volcanism, regional deformation, the development of syntectonic sedimentary successions in foreland-type basins, and late syntectonic plutonism took place in selected shear-zone-bounded tectonic domains over limited periods of time (<10–20 Ma). Deformation led to isostatically stable, 30–40 km thick continental crust, without significant exhumation of high-pressure rocks, suggesting that lithospheric shortening was accommodated independently in a rheologically strong upper and weak lower crust. Deformation was followed by pan-cratonic crustal melting and strike-slip shear motions, and led to stabilization of the crust at 2575 Ma, heralded by the emplacement of the Great Dyke.
Carbon dioxide cycling through the mantle and implications for the climate of ancient Earth
Authors: Zahnle Kevin , Sleep Norman H. 
Published: April 2008

Abstract

The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO
2
and climate. Feedback is provided by the temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO
2
. The oceanic cycle is linked to the mantle via subduction of carbonatized basalts and degassing of CO
2
at the mid-ocean ridges. Feedback is provided by the dependence of carbonatization on the amount of dissolved carbonate in sea water. Unlike the continental cycle, the oceanic cycle has no thermostat. Hence surface temperatures can become very low if CO
2
is the only greenhouse gas apart from water. Currently the continental cycle is more important, but early in Earth’s history the oceanic cycle was probably dominant. We argue that CO
2
greenhouses thick enough to defeat the faint early Sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of Proterozoic and Archaean time. We echo current fashion and favour biogenic methane as the chief supplement to CO
2
. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO
2
levels still further in Hadean time. Despite its name, the Hadean Eon might have been the coldest era in the history of the Earth.
Global modelling of continent formation and destruction through geological time and implications for CO
2
drawdown in the Archaean Eon
Authors: Kramers Jan D. 
Published: April 2008

Abstract

The possible drawdown of a massive CO
2
atmosphere in early Earth history is discussed using two working hypotheses: first, that this removal of CO
2
from the atmosphere occurred mainly via silicate weathering; second, that crust-to-mantle recycling rates found from forward modelling of crust-mantle history can be used to estimate rates of this ancient silicate weathering. Previous U-Th-Pb and Sm-Nd forward modelling efforts are reviewed, from which it was concluded that an insignificant amount of continental crust existed at 4.4 Ga, i.e. so-called ‘no-growth models’ for the continental crust appear untenable. New modelling carried out is based on a crustal growth curve starting with zero mass at 4.2 Ga and reaching 75% of the present crust mass by 2 Ga. It concerns variations in crust-to-mantle recycling rates through geological time. Best fits to isotope data are obtained if it is assumed that erosion rates (mass removal per unit surface) were approximately constant from early Archaean time to the present. From the results it can be estimated that drawdown of a massive CO
2
atmosphere by silicate weathering could have been completed by the end of Archaean time at the earliest, and about 1.5 Ga ago at the latest.