新疆东天山图拉尔根大型铜镍矿床硫化物珠滴构造的特征及其对通道式成矿的指示

东天山图拉尔根岩浆铜镍硫化物矿床中产出一种不常见的硫化物珠滴状构造。这些硫化物珠滴粒度在5~20mm左右,是由磁黄铁矿、镍黄铁矿、黄铜矿等硫化物矿物组成的斑杂状硫化物集合体。野外观察发现硫化物珠滴具有各种几何形态,产出在稀疏浸染状硫化物和无矿化的辉石岩之间的部位。对图拉尔根杂岩体中发育的24个硫化物珠滴的统计结果显示,平缓厚层状矿化部位的硫化物珠滴呈水平方向拉长,陡倾薄层状矿化部位的硫化物珠滴呈陡倾拉长,珠滴的拉长方向和矿体的延伸方向一致。这表明在含矿母岩浆上升就位到中上地壳的过程中,硫化物珠滴受到熔浆流动的控制,因而其形态可以很好地指示通道式成矿硫化物熔体运动的方向。 硫化物珠滴的矿相学和电子探针数据表明其具有向地性特征,即磁黄铁矿和镍黄铁矿先结晶,沉淀在下部; 珠滴上部为后结晶的黄铜矿和其它富铜硫化物。这种元素分布可能对贯入块状硫化物矿石同样适用。碲化物和铋化物在硫化物珠滴中的含量明显高于其在早结晶的浸染状硫化物中的含量,表明富Te和Bi等元素及挥发份的熔体是在岩浆演化后期开始富集结晶的。     

Interaction study of clay-bearing amphibolite–crude oil–saline water: Molecular level implications for enhanced oil recovery during low saline water flooding

Low saline water flooding (LSWF) had proved to be an efficient method for enhanced oil recovery in clay-bearing hydrocarbon reservoirs, but the interaction mechanisms among in-situ rocks – fluids and injection fluids within the reservoir – are not yet known properly. Understanding the molecular level interaction among these components is critical for designing and field scale implementation of LSWF in clay-bearing crystalline reservoir rocks, which is very limited in the existing literature. A weathered amphibolite rock and one dead crude oil from the Bakrol field (Cambay basin, India) have been used in this study. The presence of clay minerals in the weathered amphibolite rock was observed using a polarising microscope and characterised by the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques. The crude oil and its fractionated SARA components have been extensively studied by spectroscopic techniques for their characterisation. The interaction study among the rock powder, hydrocarbon crude oil and saline water has been performed in the present work for gaining better insight for designing the injection fluid for LSWF. The weathered amphibolite rock powder was mixed with the dead crude oil and kept for 30 days in room temperature (T) and pressure (P) for proper interaction. The XRD, FTIR and cation exchange capacity results clearly demonstrated the incorporation of crude oil components in the interlayer surfaces of clay minerals. The oil removal efficiency, from the oil-treated rock powder of three saline water samples having NaCl concentration of 3000, 5000 and 8000 ppm, was investigated using the UV–Vis and fluorescence spectroscopies. The low saline NaCl water is capable of removing the maximum amount of polar components from the oil-treated rock powder. These molecular level insights are valuable for designing effective injection fluid for enhancing the oil recovery from the clay-rich crystalline reservoir rock.     

Summer monsoon circulation and precipitation over the tropical Indian Ocean during ENSO in the NCEP climate forecast system

This study investigates the El Niño Southern Oscillation (ENSO) teleconnections to tropical Indian Ocean (TIO) and their relationship with the Indian summer monsoon in the coupled general circulation model climate forecast system (CFS). The model shows good skill in simulating the impact of El Niño over the Indian Oceanic rim during its decay phase (the summer following peak phase of El Niño). Summer surface circulation patterns during the developing phase of El Niño are more influenced by local Sea Surface Temperature (SST) anomalies in the model unlike in observations. Eastern TIO cooling similar to that of Indian Ocean Dipole (IOD) is a dominant model feature in summer. This anomalous SST pattern therefore is attributed to the tendency of the model to simulate more frequent IOD events. On the other hand, in the model baroclinic response to the diabatic heating anomalies induced by the El Niño related warm SSTs is weak, resulting in reduced zonal extension of the Rossby wave response. This is mostly due to weak eastern Pacific summer time SST anomalies in the model during the developing phase of El Niño as compared to observations. Both eastern TIO cooling and weak SST warming in El Niño region combined together undermine the ENSO teleconnections to the TIO and south Asia regions. The model is able to capture the spatial patterns of SST, circulation and precipitation well during the decay phase of El Niño over the Indo-western Pacific including the typical spring asymmetric mode and summer basin-wide warming in TIO. The model simulated El Niño decay one or two seasons later, resulting long persistent warm SST and circulation anomalies mainly over the southwest TIO. In response to the late decay of El Niño, Ekman pumping shows two maxima over the southern TIO. In conjunction with this unrealistic Ekman pumping, westward propagating Rossby waves display two peaks, which play key role in the long-persistence of the TIO warming in the model (for more than a season after summer). This study strongly supports the need of simulating the correct onset and decay phases of El Niño/La Niña for capturing the realistic ENSO teleconnections. These results have strong implications for the forecasting of Indian summer monsoon as this model is currently being adopted as an operational model in India.     

“They want to live in the Tremé, but they want it for their ways of living”: gentrification and neighborhood practice in Tremé, New Orleans

In this study, I deploy an ethnographic approach to analyze the detrimental effects of gentrification on longstanding residents in New Orleans’ Tremé neighborhood. I focus on conflicts between long-established residents and gentrifiers over the use of neighborhood space on a day-to-day basis as a means for examining the consequent changes in neighborhood life. As their neighborhood gentrifies, long-term residents of Tremé must contend with greater policing, the erosion of place-based knowledge, practices, and cultural traditions, the loss of social networks, and the closure of vital neighborhood institutions. These changes in neighborhood life provide a starting point from which to begin to understand the broader effects (beyond displacement) that longstanding residents experience as a result of gentrification.     

Rare earth elements distribution in fluorites and carbonate sediments of the east-alpine mid-triassic sequences in the Nördliche Kalkalpen

Controversial genetical interpretations on the fluorite occurrences in the leadzinc deposits of the Nördliche Kalkalpen led to the present study. The distribution of the rare-earth elements (REE) in the fluorspar-carbonate assemblages and the fluorspar separates have been determined non-destructively by means of instrumental neutron activation analysis using high resolution γ-spectrometry. A geochemical model describing the distribution of the REE in the two mineral phases of CaCO₃ and CaF₂ formed syngenetically under marine conditions has been built up in order to elucidate the observed REE abundances in the carbonates and their fluorspar separates. The low and comparable concentrations of REE, the similarity in their relative distribution patterns in carbonate-fluorspar assemblages as compared to those in carbonate sediments observed by other authors and the sedimentary characterization via the Tb/Ca-Tb/La relation criterion revealed by the present study unequivocally suggest a synsedimentary nature of the fluorspar. In addition, the study showed that a diagenetic recrystallization results in a further fractionation of Tb and La with a preferential improverishment in La. Such a phenomenon opens a possible geochemical criterion for the identification of different generations of fluorspars.     

A laboratory study of high chromium alloy wear in phosphate grinding mill

Grinding mills are commonly used in the Florida phosphate industry to reduce particle size. The corrosion of metallic grinding media and mill liner is a very serious problem, particularly under acidic conditions as encountered in the Florida phosphate fertilizer industry. A statistical Box–Behnken Design (BBD) of experiments was performed to evaluate the effects of individual operating variables and their interactions on the wear rate of high chromium alloy during phosphate grinding. The variables examined in this study included grinding time, solution pH, rotation speed, mill crop load, and solids percentage. The wear tests were conducted using a specially designed grinding mill whose electrochemical potential can be controlled. The most significant variables and optimum conditions were identified from statistical analysis of the experimental results using response surface methodology (RSM). It has been shown that solution pH had the most significant effect on the wear rate. The optimum process parameters for minimum wear rate were solution pH at 8.7, rotation speed at 61 rpm, solid percentage at 65% and crop load at 58%.     

Surface winds in The Arabian Sea from MSMR — an Empirical approach

Multi-channel Scanning Microwave Radiometer (MSMR) onboard 1RS P4 (Oceansat I) measured Brightness Temperature data of the different bands are found sensitive to the surface and the overlying atmosphere to different degrees. A judicious combination of multi-channel data can provide such oceanic/atmospheric parameters as surface wind speed, sea surface temperature, water vapour in the marine atmosphere, etc. This paper highlights results obtained in relation to surface wind speed. Co-location and concurrence of several ocean data buoys in the Arabian Sea with MSMR observations allowed empirical construction of D-matrix coefficients for surface wind speed. With both MSMR and the Arabian Sea buoys functioning for the period of one and a half year (June, 1999 to December, 2000) without interruptions provided a large database. All channels are found to exhibit moderate sensitivity to surface wind speed. MSMR data in the immediate vicinity (within 150 km) of the buoy locations and within a time window of one hour were used. A multi-channel linear equation for surface wind speed was subsequently derived. The equation was subjected to tests with independent data set for the period January - June 2001 over the Arabian Sea and found to be moderately accurate. The empirical equation is expected to be useful for regional applications over the Arabian Sea and over regions closer to west coasts, which might have been flagged out in the operational geophysical data stream. An interesting subset of data revealed the wind signatures of the May 2001 cyclone in the Arabian Sea.     

Clusters of Galaxies and the Cosmic Web with Square Kilometre Array

The intra-cluster and inter-galactic media that pervade the large scale structure of the Universe are known to be magnetized at sub-micro Gauss to micro Gauss levels and to contain cosmic rays. The acceleration of cosmic rays and their evolution along with that of magnetic fields in these media is still not well understood. Diffuse radio sources of synchrotron origin associated with the Intra-Cluster Medium (ICM) such as radio halos, relics and mini-halos are direct probes of the underlying mechanisms of cosmic ray acceleration. Observations with radio telescopes such as the Giant Metrewave Radio Telescope, the Very Large Array and the Westerbork Synthesis Radio Telescope have led to the discoveries of about 80 such sources and allowed detailed studies in the frequency range 0.15–1.4 GHz of a few. These studies have revealed scaling relations between the thermal and non-thermal properties of clusters and favour the role of shocks in the formation of radio relics and of turbulent re-acceleration in the formation of radio halos and mini-halos. The radio halos are known to occur in merging clusters and mini-halos are detected in about half of the cool-core clusters. Due to the limitations of current radio telescopes, low mass galaxy clusters and galaxy groups remain unexplored as they are expected to contain much weaker radio sources. Distinguishing between the primary and the secondary models of cosmic ray acceleration mechanisms requires spectral measurements over a wide range of radio frequencies and with high sensitivity. Simulations have also predicted weak diffuse radio sources associated with filaments connecting galaxy clusters. The Square Kilometre Array (SKA) is a next generation radio telescope that will operate in the frequency range of 0.05–20 GHz with unprecedented sensitivities and resolutions. The expected detection limits of SKA will reveal a few hundred to thousand new radio halos, relics and mini-halos providing the first large and comprehensive samples for their study. The wide frequency coverage along with sensitivity to extended structures will be able to constrain the cosmic ray acceleration mechanisms. The higher frequency (>5 GHz) observations will be able to use the Sunyaev–Zel’dovich effect to probe the ICM pressure in addition to tracers such as lobes of head–tail radio sources. The SKA also opens prospects to detect the ‘off-state’ or the lowest level of radio emission from the ICM predicted by the hadronic models and the turbulent re-acceleration models.     

Iodine in karst-type phosphorites from the Lahn region,Germany

The concentration of iodine in 31 Tertiary continental phosphorites from the Lahn region in Germany ranges from about 0.01% to 0.18%, the mean value of 0.044% being quite compatible with that of typical commercial-grade iodine deposits. Microscopic and X-ray diffractometric studies manifested three main mineral phases in these phosphorites viz. francolite, clay minerals (kaolinite, illite), and ferric oxides (goethite, hematite). These mineral phases were investigated for iodine distribution, mode of its fixation and possible source. Sample heating at 600°C evinced no appreciable organic matter in the sample and further showed that the iodine was non-volatile in character. Regression analysis revealed a good correlation between I and Al (Ti), practically no correlation with Fe and negative correlation with P₂O₅. It was thus deduced that the iodine content is inorganic in nature and bound principally and probably internally to Al-bearing minerals. An iodine content of about 150 ppm is believed to be associated with the apatite phase of the phosphorite.Devonian volcanic rocks are assumed to be the ultimate source of both phosphorus and iodine. Those elements were released during a Tertiary weathering period, their accumulation being controlled by chemical environment and karst topography of a Devonian reef limestone.