Absence Of Minerals Research Articles

Study of xanthate decomposition in aqueous solutions

Xanthate is one of the commonly used collectors in froth flotation beneficiation of sulfide ores. It decomposes and generates toxic compounds such as carbon disulfide (CS2) which is a concern in the mining industry. A vast body of literature exists for studies on xanthate/mineral interactions, but xanthate decomposition under various conditions (e.g., in solutions or flotation pulps) is not fully understood. We have undertaken detailed studies to fill this knowledge gap, and this paper shows our study of the xanthate decomposition in aqueous solutions in the absence of minerals. This condition has not been appropriately examined by past researchers, while decomposition under this condition is used as control to other complicated ones (e.g., in flotation pulps). A GC–MS based method was developed to directly measure the decomposition products in the gas phase. Decomposition kinetics was then established based on the generation of CS2. Decomposition followed the first order kinetics, and the rate constant for Sodium iso-Butyl Xanthate (SIBX) at neutral pH level was determined to be 9.3×10−4h−1 at 25°C, 1.7×10−2h−1 at 50°C and 1.3×10−1h−1 at 70°C. The effect of pH on decomposition behavior was examined in the pH range of 1.5–12.5. We determined experimentally a maximum in the extent of decomposition as a function of pH, which was predicted theoretically in literature. A mechanism involving multiple reactions that occurred in parallel or sequentially along with the decomposition was proposed to explain the observed change of xanthate decomposition over the entire pH range. These results offer valuable insights and can serve as the basis to mitigate the detrimental effects of xanthate decomposition in plant operations, for example, by modifying plant parameters to reduce xanthate decomposition without sacrificing its performance.

Mechanically Activated Chemical Conversion of Gaseous Hydrocarbons

Propane-butane gaseous mixtures were subjected to mechanical treatment in centrifugal ball mill in the absence or presence of some mineral particles. It was found that the composition of gas mixture was changed significantly depending on duration of the mechanical coercion and solid or porous nature of mineral additives. The mechanical treatment of light hydrocarbons in the presence of quartz particles at the temperatures not exceeding 100 °C resulted at long last in complete conversion of initial organic compounds to methane, hydrogen and small amounts of carbon. The same alterations of gas composition were lesser profound when the mechanical treatment was carried out in the absence of minerals or in the presence of porous silica gel or aluminum oxide. It have been shown that direct transformation of mechanic energy to intramolecular energy of hydrocarbons is more responsible for their destruction during the process considered rather than catalytic properties of the minerals. The removal of heavier hydrocarbons from natural or casing-head petroleum gas by means of MA treatment permits to facilitate further gas transportation and to improve essentially its heat-physical properties, namely, to decrease gas average molecular mass and specific gravity and to increase its caloricity and Wobbe number' values.

Effect of tillage and crop (cereal versus legume) on greenhouse gas emissions and Global Warming Potential in a non-irrigated Mediterranean field

Crop rotation with legumes and conservation tillage systems are advisable practices in rainfed Mediterranean agro-ecosystems, since, in these areas, soils are broadly characterized by low organic matter contents and low fertility. These management practices can substantially modify the dynamics of soil greenhouse gas (GHG) emissions, carbon sequestration and carbon dioxide (CO2) emissions derived from system inputs and farm operations. In this context, a field experiment was conducted under Mediterranean conditions to evaluate the effect of three long-term tillage systems (no tillage (NT), minimum tillage (MT) and conventional tillage (CT)) and two crops (vetch (V, Vicia sativa L.) versus barley (B, Hordeum vulgare L.)) on nitrous oxide (N2O), methane (CH4) and CO2 emissions during one year. Crop yields, soil mineral nitrogen concentrations, dissolved organic carbon and GHG fluxes were measured during the growing season. Soil organic carbon was measured in spring 2012 (18 years after the beginning of a long-term tillage experiment) and together with input and fuel consumption by farm machinery was used to compare the Global Warming Potential (GWP) of the different crop and tillage treatments. Cumulative fluxes of N2O ranged between 0.16 (B-MT) and 0.29 (V-MT) kgN2O-Nha−1yr−1, resulting in a lower impact on Net GWP than in previous studies. A significant ‘tillage×crop’ interaction was observed in cumulative N2O emissions (V resulted in higher N2O losses than barley in CT and MT, whereas similar fluxes were observed under NT), which was influenced by soil water-filled pore space, dissolved organic carbon content and denitrification losses, in spite of the presumable predominance of nitrification. Neither tillage nor crop influenced CH4 or CO2 emissions. Yield-scaled N2O emissions (YSNE) were low (<4gN2O-NkgabovegroundNuptake−1) and significantly higher in B than in V. The most sustainable crop and tillage treatments in terms of GWP were non-fertilized-V and NT, due to higher carbon sequestration and lower fuel consumption under NT and the absence of mineral N fertilizers in V. These crop and tillage treatments could be considered good management strategies in rainfed Mediterranean agro-ecosystems since they provide the best balance between soil emissions, YSNE and Net GWP.

Geology of El Domo deposit in central Ecuador: a VMS formed on top of an accreted margin

El Domo is a Cu-Au-Zn-Ag volcanogenic massive sulfide deposit (VMS) within the Paleocene–Eocene submarine arc rocks of the Macuchi Formation in central Ecuador. The mineralization includes massive and semi-massive sulfides located at the interface between a submarine rhyodacite dome complex and overlying mafic volcanic and volcaniclastic rocks, including chaotic and unsorted debris flow deposits. Whole rock geochemical analyses show that the felsic rocks belong to a calc–alkaline sequence, whereas the mafic assemblages have a tholeiitic affinity, reflecting a magmatic association typically found in many VMS districts. This geochemical change temporally coincides with the formation of the massive sulfides. New zircon Hf isotopic data collected from a hanging wall rhyodacite suggest that the presence of an over-thickened crust of oceanic plateau affinity may have influenced the composition of the magmatic rocks. The timing of massive sulfide formation is constrained by an 40Ar/39Ar age of 41.49 ± 0.37 Ma (2σ) from the volcaniclastic sequence which hosts the massive sulfides and a U/Pb zircon age date of 42.13 ± 0.54 Ma (2σ) from the footwall rhyodacite; both ages are interpreted to provide minimum and maximum ages for mineralization. The massive sulfides are zoned and contain variable proportions of pyrite, sphalerite, and chalcopyrite. Minor accumulations of galena, bornite, tennantite, stromeyerite, and proustite are also present; the latter two minerals are the major carriers of silver whereas gold typically occurs as minute-free grains or in solid solution with silver. Ore minerals are intergrown with variable proportions of chlorite, barite, quartz, anhydrite, and smectite. The footwall rhyodacite hosts an irregular stringer zone which is rich in pyrite and gypsum and is characterized by intense quartz-sericite-pyrite alteration. The hanging wall volcaniclastic lithologies exhibit pervasive but vertically limited (8–10 m) silicification, chloritization, and argillization. Both felsic and mafic glass-rich rocks located near the contact between rhyodacites and mafic volcaniclastic rocks are replaced by massive to disseminated mineralization, likely controlled by their originally reactive and porous nature. Replacement appears to have taken place at very shallow depths, 10–20 m below the seafloor, as shown by: (1) the presence of massive sulfide clasts within the uppermost volcaniclastic horizons and (2) the absence of mineralization and alteration in the overlying debris flows. No evidence of exhalation on the seafloor has been found, and replacement below the sea floor was probably an efficient mechanism for preserving the VMS within such a highly dynamic volcanic system. Regionally, mineralization occurred within an extensional submarine arc setting whereby massive sulfides were preferentially controlled by the reactivation of NNE-SSW crustal-scale strike slip faults created during an earlier plate collision. Local stress regimes resulted in the formation of pull-apart basins within a regional transpressive setting and provided conduits for magmatic and hydrothermal discharge. The onset of volcanism and local extension coincided with an increase in the oblique convergence of the Farallon and the South American Plate.

Update on Peritoneal Dialysis: Core Curriculum 2016

Update on Peritoneal Dialysis: Core Curriculum 2016

Effect of substrate quality on the N uptake routes of soil microorganisms in different soil depths

A few studies have indicated that substrate quality is an important factor affecting the N uptake route of soil microorganisms, but less is known about the effect of soil depth on the N uptake route under different nutrient conditions. Objectives were to investigate (i) the effects of corn residues with different C to N ratios in the presence and absence of mineral N and (ii) the effects of soil depth on the N uptake route of soil microorganisms. An incubation experiment with surface soils (0–5cm, C/N=10) and subsoils (30–40cm, C/N=9) from three German loess sites was carried out for 21 days at 20°C and 60% of their water-holding capacity. The following treatments were used: no addition (control), addition of corn residues with a C/N ratio of 20, 40, and 40+(NH4)2SO4. To distinguish between the N uptake routes, the mineralization rate of amino acids was determined using 15N-labeled amino acids. In the control surface soil and subsoil the direct uptake of organic N was favored with no significant (p<0.05) differences between depths despite significantly higher microbial activity, protease activity, gross N mineralization rate and availability of inorganic N in the surface soil, suggesting that N availability relative to C was similar at both depths. Substrate additions resulted in significantly increased protease activities at both depths after 3–7 days. Addition of corn residue with a high C/N ratio resulted in an increased direct uptake (97% and 94% in the surface soil and subsoil, respectively), compared with addition of corn residue with a low C/N ratio or addition of corn residue and inorganic N (79 to 91% direct uptake). This suggests that the enzyme system involved in the direct uptake was slightly repressed under conditions of sufficient mineralizable N (C/N of 20) or increased concentrations of NH4+. Substrate additions resulted in an initial significantly higher increase in the direct uptake in the surface soil than in the subsoil.

Effect of substrate quality on the N uptake routes of soil microorganisms in an incubation experiment

Microorganisms may either directly take up organic N or use the mobilization-immobilization-turnover (MIT) route to satisfy their N demand. However, there is only little information available about the factors controlling these two different uptake routes. The objective was to investigate the effects of substrate quality of corn with different C to N ratios in the presence and absence of mineral N on the N uptake route of soil microorganisms. Soil from the Static Fertilization Experiment Bad Lauchstädt was incubated at 20 °C and 60% of its water-holding capacity. The following treatments were used: no addition (control (C to N ratio = 13), treatment I), addition of corn residues with a C to N ratio of 40 (II), 20 (III), and 40 & (NH4)2SO4 (IV). We studied the utilization of added amino acids in order to distinguish between the N uptake routes. The mineralization rate of amino acids increased in the order “addition of corn residues with a wide C to N ratio” (4% of added amino acids) < “corn residues with a small C to N ratio” (27%) < “corn residues with a wide C to N ratio & (NH4)2SO4” and “control treatment” (31% and 32%, respectively) after 21 days of incubation. This means that, under the assumption that all the amino acids were utilized and that no remineralization of consumed amino acids occurred, 96% (treatment II), 73% (III), 69 (IV), and 68% (I) of the added amino acids were taken up directly. These results indicate that the direct route is especially important for substrates with wide C to N ratios in the absence of mineral N (thus for conditions of high C availability). The proportion of added amino acids mineralized increased with time in all treatments, suggesting that the MIT route became more important over time. Overall, the results show that the composition of the residue and the presence or absence of mineral N had a marked effect on the N uptake route of soil microorganisms.

Fertilização com dejetos suínos: influência nas características bromatológicas da Brachiaria decumbens e alterações no solo

O objetivo deste trabalho foi avaliar as características bromatológicas de uma pastagem de Brachiaria decumbens fertilizada com dejetos suínos, bem como avaliar as alterações que a utilização desse dejeto causa em alguns atributos químicos do solo. O delineamento foi em blocos casualizados, com seis tratamentos: T1: ausência de adubação mineral e orgânica (tratamento- -controle); T2 apenas com adubação mineral; T3, T4 e T5 com diferentes doses de dejetos líquidos de suínos (respectivamente ao equivalente a 60; 120 e 180 m3 por hectare), e T6 tratamento organomineral (120 m3por hectare) de dejetos líquidos de suínos, com adição de fertilizante mineral). Observou-se que houve incremento em produtividade de massa seca (MS). O uso de dejetos de suínos resultou em aumento significativo nos valores de proteína bruta das plantas de Brachiaria decumbens, não tendo a mesma eficiência para os valores de fibra em detergente neutro (FDN), fibra em detergente ácido (FDA) e lignina. A aplicação de dejetos suínos aumentou os teores de N, P, Ca e Mg nas plantas de Brachiaria decumbens. Não foram constatadas alterações quando comparados os valores de pH e matéria orgânica do solo. Os dejetos líquidos de suínos podem ser utilizados para fornecer macronutrientes para as forrageiras, desde que com aplicação controlada.

Effects of organic matter addition on phosphorus availability to flooded and nonflooded rice in a P‐deficient tropical soil: a greenhouse study

AbstractAddition of organic matter (OM) to flooded soils stimulates reductive dissolution of Fe(III) minerals, thereby mobilizing associated phosphate (P). Hence, OM management has the potential to overcome P deficiency. This study assessed if OM applications increases soil or mineral fertilizer P availability to rice under anaerobic (flooded) condition and if that effect is different relative to that in aerobic (nonflooded) soils. Rice was grown in P‐deficient soil treated with combinations of addition of mineral P (0, 26 mg P/kg), OM (0, ~9 g OM/kg as rice straw + cattle manure) and water treatments (flooded vs nonflooded) in a factorial pot experiment. The OM was either freshly added just before flooding or incubated moist in soil for 6 months prior to flooding; blanket N and K was added in all treatments. Fresh addition of OM promoted reductive dissolution of Fe(III) minerals in flooded soils, whereas no such effect was found when OM had been incubated for 6 months before flooding. Yield and shoot P uptake largely increased with mineral P addition in all soils, whereas OM addition increased yield and P uptake only in flooded soils following fresh OM addition. The combination of mineral P and OM gave the largest yield and P uptake. Addition of OM just prior to soil flooding increased P uptake but was insufficient to overcome P deficiency in the absence of mineral P. Larger applications of OM are unlikely to be more successful in flooded soils due to side effects, such as Fe toxicity.

Osteogenic cell cultures cannot utilize exogenous sources of synthetic polyphosphate for mineralization.

Phosphate is critical for mineralization and deficiencies in the regulation of free phosphate lead to disease. Inorganic polyphosphates (polyPs) may represent a physiological source of phosphate because they can be hydrolyzed by biological phosphatases. To investigate whether exogenous polyP could be utilized for mineral formation, mineralization was evaluated in two osteogenic cell lines, Saos-2 and MC3T3, expressing different levels of tissue non-specific alkaline phosphatase (tnALP). The role of tnALP was further explored by lentiviral-mediated overexpression in MC3T3 cells. When cells were cultured in the presence of three different phosphate sources, there was a strong mineralization response with β-glycerophosphate (βGP) and orthophosphate (Pi) but none of the cultures sustained mineralization in the presence of polyP (neither chain length 17-Pi nor 42-Pi). Even in the presence of mineralizing levels of phosphate, low concentrations of polyP (50 μM) were sufficient to inhibit mineral formation. Energy-dispersive X-ray spectroscopy confirmed the presence of apatite-like mineral deposits in MC3T3 cultures supplemented with βGP, but not in those with polyP. While von Kossa staining was consistent with the presence or absence of mineral, an unusual Alizarin staining was obtained in polyP-treated MC3T3 cultures. This staining pattern combined with low Ca:P ratios suggests the persistence of Ca-polyP complexes, even with high residual ALP activity. In conclusion, under standard culture conditions, exogenous polyP does not promote mineral deposition. This is not due to a lack of active ALP, and unless conditions that favor significant processing of polyP are achieved, its mineral inhibitory capacity predominates.

Clinical Aspects of Hypophosphatasia: An Update

Hypophosphatasia (HPP) is a heterogeneous rare inborn error of bone and mineral metabolism caused by mutations in the ALPL gene encoding the isoenzyme, tissue-nonspecific alkaline phosphatase (TNAP). These mutations result in a decreased level of TNAP activity and increased levels of its substrates, including inorganic pyrophosphate, pyridoxal-5′-phosphate and phosphoethanolamine. Clinical presentations are highly variable, ranging from stillbirth and absence of mineralization in severe disease to mild dental problems or osteopenia in adulthood. Further clinical symptoms include defective bone mineralization with bone deformities, recurrent fractures, chronic non-bacterial osteomyelitis, craniosynostosis, neonatal seizures, nephrocalcinosis, muscular hypotonia, failure to thrive and dental abnormalities with premature exfoliation of teeth and caries. Prognosis is very poor in severe perinatal forms with most patients dying from pulmonary complications of their skeletal disease but patients with mild phenotypes (adult form or Odonto-HPP) usually do not have a limitation in their life expectancy. Although TNAP is a ubiquitous enzyme, mostly known for its crucial role during mineralization of bone and teeth, its exact biological role in different human organs is still unclear, and the pathophysiology of symptoms due to TNAP deficiency in HPP are not understood in detail. Since inflammation and tissue destruction of the musculoskeletal system may occur in HPP, TNAP may also play an important role in controlling inflammatory processes. Recent investigations provide evidence that TNAP is also essentially involved in the development of the central nervous system and might contribute to multiple functions of the human brain. HPP can be diagnosed on clinical, biochemical and radiological criteria, and genetic testing confirms the diagnosis and is useful for genetic counseling. Since clinical symptoms are highly variable, patients should be followed up by a multidisciplinary team having experience in HPP treatment. Up to now, no curative treatment of HPP is available. Therefore, symptomatic treatment in particular with regard to pain, seizures and other metabolic phenomena is most important. However, recently, enzyme replacement therapy with a bone-targeted recombinant human TNAP molecule has been reported to improve bone mineralization, respiratory function and physical activity in severely affected infants with HPP, and further clinical trials are ongoing. Hopefully, this and other new therapeutic strategies may improve the prognosis and quality of life of patients with HPP and may contribute to our understanding of bone metabolism in general.

Objective based geochemical anomaly detection—Application of discriminant function analysis in anomaly delineation in the Kuh Panj porphyry Cu mineralization (Iran)

A common objective method for anomaly detection in geochemical exploration is target delineation by discriminant function analysis. Discriminant analysis (DA) is a multivariate statistical technique that classifies each observation into a specific group based on observed predictor variables and predefined groups. In the present study a new approach is considered for geochemical anomaly identification employing DA and “real” pre-defined “anomaly” and “background” data set. The anomalous and background samples are identified based on presence or absence of mineralization in depth; so, this method is introduced as “objective approach”. In order to classify surface geochemical samples into anomaly and background, assays of core drillings in the Kuh Panj porphyry Cu mineralization are used. They are classed as anomaly if the presence of mineralization is proven and are labeled as background if the absence of mineralization is confirmed in cores. Stepwise Linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA) are utilized to achieve discrimination functions. For the test data used to generate the models, both LDA and QDA methods have led to perfect classification however cross validation has shown 84% and 74% total correct classification for LDA and QDA respectively. Outcomes of this research have demonstrated that LDA can effectively be employed as an objective method for geochemical anomaly identification if available information from geology and geochemistry of target area are employed and utilized. It is also shown that the definition of anomalism in geochemical exploration can be improved remarkably by this approach.

High-resolution structural insights into bone: a solid-state NMR relaxation study utilizing paramagnetic doping.

The hierarchical heterogeneous architecture of bone imposes significant challenges to structural and dynamic studies conducted by traditional biophysical techniques. High-resolution solid-state nuclear magnetic resonance (SSNMR) spectroscopy is capable of providing detailed atomic-level structural insights into such traditionally challenging materials. However, the relatively long data-collection time necessary to achieve a reliable signal-to-noise ratio (S/N) remains a major limitation for the widespread application of SSNMR on bone and related biomaterials. In this study, we attempt to overcome this limitation by employing the paramagnetic relaxation properties of copper(II) ions to shorten the (1)H intrinsic spin-lattice (T(1)) relaxation times measured in natural-abundance (13)C cross-polarization (CP) magic-angle-spinning (MAS) NMR experiments on bone tissues for the purpose of accelerating the data acquisition time in SSNMR. To this end, high-resolution solid-state (13)C CPMAS experiments were conducted on type I collagen (bovine tendon), bovine cortical bone, and demineralized bovine cortical bone, each in powdered form, to measure the (1)H T(1) values in the absence and in the presence of 30 mM Cu(II)(NH(4))(2)EDTA. Our results show that the (1)H T(1) values were successfully reduced by a factor of 2.2, 2.9, and 3.2 for bovine cortical bone, type I collagen, and demineralized bone, respectively, without reducing the spectral resolution and thus enabling faster data acquisition. In addition, paramagnetic quenching of particular (13)C NMR resonances on exposure to Cu(2+) ions in the absence of mineral was also observed, potentially suggesting the relative proximity of three main amino acids in the protein backbone (glycine, proline, and alanine) to the bone mineral surface.

Heterogeneous and homogeneous reactions of pyrolysis vapors from pine wood

AbstractTo maximize oil yields in the fast pyrolysis of biomass it is generally accepted that vapors need to be rapidly quenched. The influence of the heterogeneous and homogeneous vapor‐phase reactions on yields and oil composition were studied using a fluidized‐bed reactor. Even high concentrations of mineral low char (till 55 vol %) appeared not to be catalytically active. However, the presence of minerals, either in biomass or added, does influence the yields, especially by the occurrence of vapor‐phase charring/polymerization reactions. Contradictory, in the absence of minerals, homogeneous vapor‐phase cracking reactions were dominant over polymerization/charring reactions (400–550°C, 1–15 s). With increasing vapor residence time, the oil yield reached an asymptotic value, which decreased with temperature. At a vapor temperature of 400°C no decrease in oil yield was observed, but dedicated analysis showed that homogeneous vapor to vapor reactions had occurred. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Average tin contents in the plants of the Southern Russian Far East

All test sites for biogeochemical exploration were located in the zone of coniferous and broadleaved forests (4), which allowed the comparison of tin absorption by plants in the areas localized in the same landscape-climatic conditions of the Southern Rus� sian Far East. Plants for biogeochemical prospecting were sampled using conventional technique (5) along the profile grid from 10 x 20 to 20 x 40 m depending on the thickness of ore veins and deposits. In each sam� pling point (conditional quadrant 5 x 5 m), organs and parts of all plants were taken separately if possible: leaves (needles), branches, wood, and bark for trees; leaves, branches, trunk, and roots for shrubs; and the aboveground parts for grass and moss. Samples were airdried state and burned to a white ash in the labora� tory conditions in muffle furnace at temperature of 450°С. The tin content in sample ash was determined by atomic absorption and emission spectral analyses with sensitivity of 0.0001 wt % for tin and error of 5.0%. Obtained analytical results (figure) showed that elevated tin contents were found in ashes of plants from the areas containing tin mineralization, while the same plant species beyond the ore bodies (at the flanks of mineralization) have background tin contents (0.001 wt %). In the barren test areas (the complete absence of mineralization), the tin content in the plant

Semeadura direta na produção do milho em agricultura de sequeiro na região Nordeste do Brasil

Quando implantado de modo eficiente, a semeadura direta beneficia o solo e as culturas. No Brasil, a maioria dos estudos com plantio direto concentra-se no Sul e no Centro-Oeste, carecendo de informações sobre esse sistema de manejo do solo no ambiente da região Nordeste. O objetivo deste trabalho foi avaliar a influência da semeadura direta na produtividade do milho em agricultura de sequeiro na região Nordeste do Brasil, em um experimento conduzido em Alagoinha-PB durante sete anos. As culturas do milho (Zea mays) e do guandu (Cajanus cajan) foram implantadas em três sistemas de manejo: milho em cultivo convencional (CC), milho em semeadura direta (SD), milho em semeadura direta com guandu intercalar (SG), na presença e ausência de adubação com N, P e K. As amostras de solo foram coletadas no início e no final do experimento, sendo determinados a densidade do solo e de partículas, a porosidade total, o diâmetro médio ponderado de agregados secos e úmidos e o índice de estabilidade de agregados. Também foram quantificadas a percentagem de cobertura do solo e a produtividade de grãos de milho. A porosidade do solo e a estabilidade de agregados foram menores após o período avaliado. A cobertura do solo aumentou significativamente, chegando a cobrir 96 % da área nos sistemas SD e SG, no início do desenvolvimento da cultura. A adubação e os sistemas SD e SG influenciaram positivamente na produtividade do milho. A precipitação pluvial foi o fator que causou maior variabilidade nos resultados ao longo do estudo.

Microbially induced flotation of alumina, silica/calcite from haematite

Selective separation of haematite from alumina and silica/calcite was achieved through microbiologically induced flotation and flocculation in presence of Bacillus subtilis. Bacterial metabolites containing extracellular proteins were characterized from mineral-grown bacterial cell free extract. Bacteria can adhere to mineral surfaces and influence subsequent flotation of the minerals. Cells and metabolic products of bacteria were used in flotation, flocculation and adsorption studies on oxide minerals. Bacteria functions as a stronger depressant for haematite. Selective affinity of the bacterial cells towards the mineral surface was observed through adsorption studies. Bacterial byproduct like extracellular protein (EP) was isolated from bacteria. The protein profile of the EP of bacterial cells grown in presence and absence of minerals (haematite, corundum, quartz and calcite) was also studied. The role of such proteins in selective mineral separation was demonstrated through microbially induced selective flotation. This study has demonstrated the utility and amenability of microbially induced mineral beneficiation through the use of bacterially generated metabolic products and mineral-grown bacterial cells.

Fluid sources and metallogenesis in the Blackbird Co-Cu-Au-Bi-Y-REE district, Idaho, U.S.A.: insights from major-element and boron isotopic compositions of tourmaline

Tourmaline is a widespread mineral in the Mesoproterozoic Blackbird Co–Cu–Au–Bi–Y–REE district, Idaho, where it occurs in both mineralized zones and wallrocks. We report here major-element and B-isotope compositions of tourmaline from stratabound sulfide deposits and their metasedimentary wallrocks, from mineralized and barren pipes of tourmaline breccia, from late barren quartz veins, and from Mesoproterozoic granite. The tourmalines are aluminous, intermediate in the schorl–dravite series, with Fe/(Fe + Mg) values of 0.30 to 0.85, and 10 to 50% X -site vacancies. Compositional zoning is prominent only in tourmaline from breccias and quartz veins; crystal rims are enriched in Mg, Ca and Ti, and depleted in Fe and Al relative to cores. The chemical composition of tourmaline does not correlate with the presence or absence of mineralization. The δ 11 B values fall into two groups. Isotopically light tourmaline (−21.7 to −7.6‰) occurs in unmineralized samples from wallrocks, late quartz veins and Mesoproterozoic granite, whereas heavy tourmaline (−6.9 to +3.2‰) is spatially associated with mineralization (stratabound and breccia-hosted), and is also found in barren breccia. At an inferred temperature of 300°C, boron in the hydrothermal fluid associated with mineralization had δ 11 B values of −3 to +7‰. The high end of this range indicates a marine source of the boron. A likely scenario involves leaching of boron principally from marine carbonate beds or B-bearing evaporites in Mesoproterozoic strata of the region. The δ 11 B values of the isotopically light tourmaline in the sulfide deposits are attributed to recrystallization during Cretaceous metamorphism, superimposed on a light boron component derived from footwall siliciclastic sediments ( e.g. , marine clays) during Mesoproterozoic mineralization, and possibly a minor component of light boron from a magmatic–hydrothermal fluid. The metal association of Bi–Be–Y–REE in the Blackbird ores suggests some magmatic input, but involvement of granite-derived fluids cannot be conclusively established from the present database.

Phoronid phylogenetics (Brachiopoda; Phoronata): evidence from morphological cladistics, small and large subunit rDNA sequences, and mitochondrialcox1

A matrix of 24 morphodevelopmental characters and an alignment of small subunit (SSU) and large subunit (LSU) rDNA nuclear and cox1 mitochondrial gene sequences (∼4500 sites) were compiled from up to 12 phoronids including most named taxa, but probably constituting only a portion of worldwide diversity. Morphological data were analysed by weighted parsimony; sequence data by maximum and Bayesian likelihood, both with Phoronis ovalis as the local outgroup. Morphological and sequence-based phylogenies were similar, but not fully congruent. Phoronid rDNAs were almost free from mutational saturation, but cox1 showed strong saturation unless distant outgroups and P. ovalis were omitted, suggesting that many phoronid divergences are old (≥100 Myr). rDNA divergence between named phoronid taxa is generally substantial, but Phoronopsis harmeri (from Vladivostock) and Phoronopsis viridis (from California) are genetically close enough to be conspecific. In another alignment, of 24 taxa, phoronid rDNAs were combined with data from brachiopods and distant (molluscan) outgroups. The relative ages of divergence between phoronids and their brachiopod sister-groups, of the split between the P. ovalis and non-ovalis lineages, and of other phoronid splits, were estimated from this alignment with a Bayesian lognormal uncorrelated molecular clock model. Although confidence limits (95% highest probability density) are wide, the results are compatible with an Early Cambrian split between phoronids and brachiopods and with the Upper Devonian latest age suggested for the P. ovalis/non-ovalis split by the putative phoronid ichnofossil, Talpina. Most other ingroup splits appear to be ∼50–200 Myr old. Inclusion of phoronids with brachiopods in the crown clade pan-Brachiopoda suggests that a distinctive metamorphosis and absence of mineralization are ancestral phoronid apomorphies. Worldwide diversity and possible associations between character-states and life-history attributes deserve comprehensive further study.

Sulfide Mineral Induced Oxidative Stress as a Limiting Factor in Tank Bioleaching Performance

In tank bioleaching, decreasing particle size of milled concentrates has been shown to improve leaching performance owing to increased mineral surface area and mechanical activation effects of fine mineral particles. However, evidence suggests a critical lower limit of particle size distribution exists below which the performance of the thermophilic iron and sulfur oxidizer Sulfolobus metallicus is compromised and complete culture death may result. This paper proposes an explanation for these observations at fine fractions through identifying a relationship between mineral composition of six sulfide concentrates, their extent of milling and the generation of the reactive oxygen species (ROS) hydrogen peroxide (H2O2) and hydroxyl radicals (•OH) in slurries. The effect of oxidative stress induced in the absence of minerals on growth and bioleaching performance of S. metallicus is studied.