New data on mineralogy and metallogeny of scarns in the Pitkyaranta ore region

A wide application of modern precision research techniques to the studies of Pitkyaranta ores allowed us to find increased contents of indium (to 0.33%), silver (447 g/t), gold (0.2–0.4 g/t), and palladium (0.2 g/t). A series of rare minerals previously not found here was also discovered. Among ore minerals, these are roquesite, zavartskite, electrum, stutzite, altaite, bismite, glaucodot, cervelleite, hedleyite, pavonite, cannonite, plantnerite, lindkvistite, ashoverite, etc. The discovery of roquesite and electrum is the most important in terms of metallogeny. Roquesite (indium sulfide) is found in Karelia for the first time. The highest indium contents in direct correlation to those of zinc are characteristic for polymetallic ores of the Pitkyaranta ore fields with sphalerite as the concentrating mineral (to 0.5% of In). The predicted zinc resources are evaluated to ∼2.5 million t for the Pitkyaranta group of ore deposits, and to 400 000 t for the Hopunvaara region. Respectively, the resources of indium amount to ∼2400 t (total) and 600 t for the Hopunvaara region.     

The effect of anatase, rutile and sodium titanate on the dissolution of boehmite and gibbsite at 90 °C

Industrial plants that refine bauxite to alumina using the high temperature process have always held the belief that anatase was detrimental to the extraction of boehmite while rutile was not. This study shows that this effect is real and that it is observable at temperatures as low as 90 °C. The extraction of gibbsite is shown to be unaffected which leads us to believe that the kinetics of both the Ti-bearing mineral and the Al-bearing mineral is important in this phenomenon. In addition, it is shown that not only is the presence of anatase an issue in boehmite extraction but so too is the presence of sodium titanate. Rutile was found to have the least impact of the three mineral phases.     

Electron microscopy studies of akermanites (Ca1−xSrx)2CoSi2O7 with modulated structure

Single crystals of akermanite (Ca_1–x Sr _x )₂Co-Si₂O₇ solid solution were grown in nitrogen by the floating zone method using a lamp-image furnace. The grown crystals were 6 mm in diameter by 50 mm in length. Microprobe analyses indicate uniform strontium content x except in the initially crystallized part. Synthetic crystals with x from 0.0 to 0.3 give, at room temperature, satellite reflections and circular diffuse scatterings in the electron diffraction pattern, which are related to an incommensurate phase and microdomains, respectively. With increasing Sr content the wavelength of a modulation increases and the intensity of satellites decreases, but the intensity of circular diffuse scattering increases up to x=0.15 and then decreases until eventually the satellites and the circular diffuse scatterings disappear at x = 0.3. The circular diffuse scattering is explained by the cluster model for the transition state, proposed by De Ridder et al. (1976).     

Preparation and characterization of biosorbents and copper sequestration from simulated wastewater

This paper reports the potential of chemically treated wood chips to remove copper (II) ions from aqueous solution a function of pH, adsorbent dose, initial copper (II) concentration and contact time by batch technique. The wood chips were treated with (a) boiling, (b) formaldehyde and (c) concentrated sulphuric acid and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive analysis X-ray. pH 5.0 was optimum with 86.1, 88.5 and 93.9 % copper (II) removal by boiled, formaldehyde-treated and concentrated sulphuric acid-treated wood chips, respectively, for dilute solutions at 20 g L^?1 adsorbent dose. The experimental data were analysed using Freundlich, Langmuir, Dubinin–Radushkevich and Temkin isotherm models. It was found that Freundlich and Langmuir models fitted better the equilibrium adsorption data and the adsorption process followed pseudo-second-order reaction kinetics. The results showed that the copper (II) is considerably adsorbed on wood chips and it could be an economical option for the removal of copper from aqueous systems.     

Rigid Unit Modes in disordered nepheline: a study of a displacive incommensurate phase transition

 Calculations of the Rigid Unit Modes (RUMs) allowed in the nepheline structure are used to explain the diffuse scattering previously seen in electron diffraction experiments. The RUM calculations also show that the modulation wavelength for incommensurate nephelines is essentially determined by the framework topology. X-ray diffraction is used to measure the intensity of the diffuse scattering as a function of temperature. The diffuse intensity increases sharply at 308 K. This effect is interpreted as being due to the softening of a phonon mode, indicating a phase transition. Measurements of this phase transition below the transition temperature are made using hard mode infrared spectroscopy. Received: 17 February 1999 / Revised, accepted. 15 October 1999     

Flotation of calcareous Mussorie phosphate ore

Separation of Mussorie rock phosphate (P₂O₅ = 20%) from Uttar Pradesh, India, containing pyrite, calcite and other carbonaceous impurities by flotation has been successfully attempted to upgrade the phosphate values. Based on Hallimond cell flotation results of single and synthetic mineral mixtures of calcite and apatite using oleic acid and potassium phosphate, conditions were obtained for the separation of calcite from apatite which is considered to be the most difficult step in the beneficiation of calcareous phosphates. Further studies using 250 g of the mineral (?60 +150 and ?150 mesh fractions, deslimed) in laboratory size Fagergren subaeration machine employed a stagewise flotation viz. carbonaceous materials using terpineol, pyrite using potassium-ethyl xanthate and calcite using oleic acid respectively. Separation was, however, found to be unsatisfactory in the absence of a depressant.Among starch, hydrofluosilicic acid and dipotassium hydrogen phosphate, which were tried as depressants for apatite in the final flotation stage, dipotassium hydrogen phosphate proved to be superior to others. However, the tests with the above fractions did not yield the required grade. This was possibly due to insufficient liberation of the phosphate mineral from the ore body and different experimental conditions due to scale up operations. Experiments conducted using ?200 mesh deslimed fractions has yielded an acceptable grade of 27.6% P₂O₅ with a recovery of about 60%. The results have been explained in terms of the specific adsorption characteristics of phosphate ions on apatite and the liberation size of the mineral.     

Fluxes of organic carbon in Manukau Harbour, New Zealand

We collated information on the sources and sinks of organic carbon in Manukau Harbour, a shallow temperate estuary. Two contrasting inner harbor regions were considered; the northern region, which is urbanized and receives a major load of sewage wastewater, and the southern region, where allochthonous inputs are dominated by the runoff from small rural streams. Although high levels of dissolved nitrogen in the wastewater supported phytoplankton blooms in the northern region, total primary production there was similar to that in the southern region (ca. 300 g C m^?2yr^?1). By contrast, high concentrations of organic carbon in the wastewater resulted in an additional input to the northern region of 120 g C m^?2 yr^?1. Loads from runoff and streams to both regions were low. At 350 g C m^?2 yr^?1, total respiration in the northern region exceeded total production, so the region was slightly heterotrophic. Respiration was lower in the southern region (270 g C m^?2 yr^?1), which was net autotrophic. Some carbon was exported from each region to the outer harbour (50–80 g C m^?2 yr^?1). Dissolved oxygen levels in the northern region were somewhat depleted at times; and the high numbers of microzooplankton indicated consumption was enhanced there. Apart from a relatively small area of organic enrichment close to the wastewater discharge, benthic consumers in the harbor appeared to be limited by physical disturbance (by wind-waves) rather than by food availability. Improved wastewater treatment is expected to substantially reduce the allochthonous input to the northern region, with the total input of carbon in the future being only slightly higher than that to the southern region.     

Preliminary magnetic susceptibility characteristics of the Bharati promontory (Grovness Peninsula), Larsemann Hills,Prydz Bay region,East Antarctica

The coastal tract of the Prydz Bay region in the East Antarctica exposes Archean to Late Proterozoic magmatic and medium- to high grade (amphibolite — granulite facies) metamorphic rocks. The para- and ortho gneisses from the Bharati promontory (Grovness Peninsula) forming a part of the Larsemann Hills in the southern segment of Prydz Bay were investigated for magnetic characterization. In this small peninsula the upper amphibolite facies gneisses occur as NE-trending bands. The para-gneisses show a range of mineral assemblages (± cordierite ± sillimanite ±garnet) while ortho-gneiss mineralogy includes quartz, feldspar, biotite, garnet. All the lithological units in Bharati promontory contain ubiquitous magnetite, however, with wide variation in the volume proportions. This has resulted in a wide range in magnetic susceptibility (10^?4 to 10^?2 SI). Magnetic foliations show a correspondence with the general trend of lithounits (050° NE) and define a resulting geometry of mainly D₁ and D₂ foliations. The magnetic lineations show a preferred orientation with moderate easterly plunge (mean vector 093/36). The findings have implications for the magnetic field survey because such fabrics would impart a strong horizontal component of induced magnetization.     

Stability of a stationary Rossby wave embedded in barotropic monsoon zonal flow

Barotropic stability of a stationary Rossby wave of wavelength 30° longitude superposed on the uniform monsoon zonal flow has been examined. The wave is unstable to perturbations and the growth rate depends on the meridional scale. These perturbations grow by drawing on the kinetic energy of the stationary Rossby wave.     

SPI-based evaluation of drought events in Xinjiang, China

Daily precipitation data for 1957?C2009 from 53 stations in the Xinjiang, China, are analyzed, based on the Standardized Precipitation Index (SPI) with the aim to investigate spatio-temporal patterns of droughts. The Mann?CKendall trend test is used to detect the trends in the SPI values of monthly drought series, drought severity and drought duration. The frequencies of moderate, severe and extreme droughts are higher in the North Xinjiang, while mild droughts occur more often in the South Xinjiang. A decreasing frequency of droughts in the North Xinjiang is found in winter, but a drying tendency is detected in the western parts of the North Xinjiang during spring, summer and autumn, which may be harmful for agriculture. The South Xinjiang seems to be getting wetter in summer, while the south parts of the South Xinjiang seem to be getting drier in spring. The middle of the East Xinjiang is identified to be in a slightly dry tendency. The drought severity is decreasing and drought duration is getting shorter in the North Xinjiang, while both of them increase in the southern parts of the South Xinjiang. In addition, droughts in the middle parts of the East Xinjiang are intensifying.