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Vera M.,University of Duisburg - Essen | Schippers A.,Bundesanstalt fur Geowissenschaften und Rohstoffe BGR | Sand W.,University of Duisburg - Essen
Applied Microbiology and Biotechnology | Year: 2013

Bioleaching of metal sulfides is performed by a diverse group of microorganisms. The dissolution chemistry of metal sulfides follows two pathways, which are determined by the mineralogy and the acid solubility of the metal sulfides: the thiosulfate and the polysulfide pathways. Bacterial cells can effect this metal sulfide dissolution via iron(II) ion and sulfur compound oxidation. Thereby, iron(III) ions and protons, the metal sulfide-attacking agents, are available. Cells can be active either in planktonic state or in forming biofilms on the mineral surface; however, the latter is much more efficient in terms of bioleaching kinetics. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron(III) ions, each complexed by two uronic acid residues. The resulting positive charge allows an electrostatic attachment to the negatively charged pyrite. Thus, the first function of complexed iron(III) ions is the mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron(III) ions in non-contact leaching. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a redox chain forming a supercomplex spanning the periplasmic space and connecting both outer and inner membranes. In this review, we summarize some recent discoveries relevant to leaching bacteria which contribute to a better understanding of these fascinating microorganisms. These include surface science, biochemistry of iron and sulfur metabolism, anaerobic metabolism, and biofilm formation. The study of microbial interactions among multispecies leaching consortia, including cell-to-cell communication mechanisms, must be considered in order to reveal more insights into the biology of bioleaching microorganisms and their potential biotechnological use. © Springer-Verlag Berlin Heidelberg 2013. Source

Houben G.J.,Bundesanstalt fur Geowissenschaften und Rohstoffe BGR | Weihe U.,Oldenburgisch Ostfriesischer Wasserverband OOWV
Ground Water | Year: 2010

The spatial distribution of iron incrustations around an abandoned water well after 38 years of use was studied by analyzing the iron content of soil samples from 12 core borings. Three of these were performed inside the gravel pack, the rest at different distances in the adjacent aquifer. Incrustations had preferentially accumulated at the bottom of the screen coinciding with a zone of higher aquifer permeability. As expected, all cores from the annulus show buildup of iron oxides but the ones outside also showed elevated iron content up to 4 m away from the screen. Such distant incrustations are very difficult to remove, by mechanical or chemical methods. The common procedure of removing tubing and annulus material to install a new well at the same location could therefore give the replacement well a hydraulic disadvantage as the incrustations in the aquifer remain in place. © 2009 National Ground Water Association. Source

Franke D.,Bundesanstalt fur Geowissenschaften und Rohstoffe BGR
Marine and Petroleum Geology | Year: 2013

Traditionally active rifts are thought to evolve in response to thermal upwelling of the asthenosphere, whereas passive rifts develop in response to lithospheric extension driven by far-field stresses. Depending on the volumes of extension-related magmatism two end-member passive margin types, either volcanic or magma-poor are defined. Volcanic rifted margins evolve by extension accompanied by extensive extrusive magmatism over short time periods during breakup, manifested in reflection seismic data as seaward dipping reflectors. These margins are commonly related to mantle plumes; however, in the past years this has been questioned. Magma-poor rifted margins in contrast show wide domains of extended crust with wide-ranging extensional features as rotated faults blocks and detachment surfaces near the base of the continental crust, but limited magmatism that in addition seems to be systematically delayed to post-breakup.In this study three unique rifted margins are presented: The Laptev Sea margin in the Arctic Ocean, where the active Arctic mid-oceanic ridge meets continental lithosphere at a high angle, the South China Sea that may represent an intermediary form of continental extension between the end member extremes, and the southernmost South Atlantic with well expressed conjugate volcanic rifted margins, which are traditionally interpreted as result of a mantle plume, the Tristan da Cunha hot-spot.The accurate timing of the events when continental rifting initiated and stopped, and when subsequent sea-floor spreading began is crucial to refine models of margin development. Therefore, a detailed description of rift-onset and breakup unconformities is presented for the three continental margins that evolved in the Early Cretaceous, the Paleocene and the -Oligocene, respectively. The investigation reveals that a major controlling mode of deep, hot-spot related mantle processes on the rift evolution and rift-related magmatism cannot be observed. Instead, it is suggested that passive margin evolution is controlled by several lithosphere-scale processes and parameters, including the mode of rift propagation and propagation barriers. © 2012 Elsevier Ltd. Source

Mahanjane E.S.,Instituto Nacional Of Petroleo Inp | Franke D.,Bundesanstalt fur Geowissenschaften und Rohstoffe BGR
Tectonophysics | Year: 2014

We interpret two-dimensional seismic reflection data from the Rovuma Delta basin deep-water fold-and-thrust belts. Two major arcuate complexes with different architecture and extent are identified. While in the northern Palma arcuate complex a multitude of steep, east-dipping thrust-related fold anticlines formed above a single main detachment, in the southern Mocimboa arcuate complex multiple detachments resulted in the formation of thrust duplexes. In between the two arcuate domains, only few thrust-related fold anticlines developed.Our interpretation of the Rovuma basin is a linked system of up-dip extension and down-dip compression that is mainly driven by gravity tectonics. Sediment loading and a hinterland uplift due to the development of the East African Rift System since the Oligocene is proposed as origin of the delta.It is shown that the main, seaward-dipping detachment in Early Cenozoic strata is likely under-compacted and overpressured shale. Conversely, shale diapirism is questionable since the shape and location of such structures in the fold-and-thrust-belts appear simply indicating steeply dipping imbricated folds, rooted by a near vertical thrust.We suggest that mainly a different rheology and thickness and thus efficiency of the shale detachment across the delta resulted in different morphologies and geometries of the deep-water fold-and-thrust-belts. © 2013 Elsevier B.V. Source

Reimann C.,Geological Survey of Norway | Matschullat J.,TU Bergakademie Freiberg | Birke M.,Bundesanstalt fur Geowissenschaften und Rohstoffe BGR | Salminen R.,Geological Survey of Finland
Applied Geochemistry | Year: 2010

The distribution of Sb in a variety of sample materials, including soils, plants and surface water, was studied at different scales, from continental to local, combining published data sets with the aim of delineating the impact and relative importance of geogenic vs. anthropogenic Sb sources. Geochemical mapping demonstrates that variation is high at all scales - from the detailed scale with sample densities of many sites per km2 to the continental-scale with densities of 1 site per 5000 km2. Different processes govern the Sb distribution at different scales. A high sample density of several samples per km2 is needed to reliably detect mineralisation or contamination in soil samples. Median concentrations are so low for Sb in most sample materials (below 1 mg/kg in rocks and soils, below 0.1 mg/kg in plants, below 0.1 μg/L in surface water) that contamination is easier to detect than for many other elements. Distribution patterns on the sub-continental to continental-scale are, however, still dominated by natural variation. Given that the geochemical background is characterised by a high variation at all scales, it appears impossible to establish a reliable single value for "good soil quality" or a "natural background concentration" for Sb for any sizeable area, e.g., for Europe. For such a differentiation, geochemical maps at a variety of scales are needed. Different sample materials can reflect different geochemical sources and processes, even when collected from the same survey area. Weathering (soil formation) leads to an increased Sb concentration in soils compared to rocks. Organic soils are highly enriched (factor 5-10 compared to mineral soils) in Sb. Soils and stream sediments return comparable median Sb concentrations. Plants are usually well protected against Sb uptake. There exist, however, plant species that can accumulate Sb to values of more than 1000 mg/kg. Antimony concentrations in the marine environment are not sufficiently well-documented. High Sb concentrations, related to hydrothermal and volcanic processes may have been previously underestimated. © 2009 Elsevier Ltd. All rights reserved. Source

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