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.     

An Overview of Dissolved and Suspended Matter Fluxes in the Loire River Basin: Natural and Anthropogenic Inputs

The spatial and temporal distributions of major elements were investigated in the surface waters and in associated suspended matter at two sites of the upper Loire basin (Orleans and Brehemont) between 1995 and 1998.According to geochemical and isotopic patterns, the dissolved load appears to result from a process of mixing rainwater inputs, weathering processes of carbonate and silicate bedrock, and agricultural and urban inputs. Natural inputs influence 60% of water chemical composition at both sites. Annual dissolved fluxes were estimated to be 1300 10³ t/y at Orleans and 1620 10³ t/y at Brehemont. Major elements are transported mainly in the dissolved fraction. After correcting for atmospheric and anthropogenic inputs, the silicate specific export rate was calculated to be 11 t/y/km² throughout the basin and the carbonate specific export rate to be from 47 t/y/km² at Orleans to 23 t/y/km² at Brehemont.The suspended load appears to result from at least two particle reservoirs: a silicate reservoir and a carbonate reservoir. The silicate reservoir has a detrital origin, mainly during periods of high flow, while the carbonate reservoir has a detrital origin during periods of high flow and an authigenic origin during periods of low flow. Of the total annual flow of suspended matter, this authigenic material represents 16% at Orleans, 25% at Brehemont and 37% in the fluvial part of the estuary. After correcting authigenic inputs, the specific export rate due to mechanical weathering was estimated to be 8 t/y/km² throughout the Loire basin.     

Biogeochemical investigation in south eastern Andhra Pradesh: the distribution of rare earths, thorium and uranium in plants and soils

The concentration of rare earth elements (REE), thorium and uranium were determined by inductively coupled plasma mass spectrometry (ICP−MS) in the plant species, Pterocarpus santalinus, P. marsupium and P. dalbergioides, and the soils on which they were growing. Higher concentrations of lanthanum (La), cerium (Ce) were observed in both plants and soils. Large amounts of thorium and uranium were found in the soil. In all tree species, the concentration of REEs were higher in the heartwood than the leaves. The heartwood of P. santalinus accumulated larger quantities of uranium (average concentration of 1.22 ppm) and thorium (mean value of 2.57 ppm) than the other two species. Received: 8 September 1999 · Accepted: 15 December 1999     

Problems of Siderite Formation and Iron Ore Epochs: Communication 1. Types of Siderite-Bearing Iron Ore Deposits

It is shown that siderite is unstable during sedimentation, diagenesis, and metamorphism of sedimentary and volcanosedimentary rocks. Regularities in the distribution of siderite in Precambrian jaspilites (iron formations), metasomatic ores of the Bakal type, continental–marine coaliferous formations, and oolitic iron ores are discussed. The genesis of the Precambrian iron formations and Riphean–Lower Paleozoic elisional–hydrothermal deposits is considered. The genetic relation of nodular siderites from coaliferous formations and oolitic iron ores with lowmoor coal-forming peat deposits is noted.     

Friedrichbeckeite, K (□0.5Na0.5)2 (Mg0.8Mn0.1Fe0.1)2 (Be0.6 Mg0.4)3 [Si12O30], a new milarite-type mineral from the Bellerberg volcano, Eifel area, Germany

Friedrichbeckeite is a new milarite-type mineral. It was found in a single silicate-rich xenolith from a quarry at the Bellerberg volcano near Ettringen, eastern Eifel volcanic area, Germany. It forms thin tabular crystals flattened on {0001}, with a maximum diameter of 0.6 mm and a maximum thickness of 0.1 mm. It is associated with quartz, tridymite, augite, sanidine, magnesiohornblende, enstatite, pyrope, fluorapatite, hematite, braunite and roedderite. Friedrichbeckeite is light yellow, with white to light cream streak and vitreous lustre. It is brittle with irregular fracture and no cleavage, Mohs hardness of 6, calculated density is 2.686 gcm^?3. Optically, it is uniaxial positive with n_ω = 1.552(2) and n_ε = 1.561(2) at 589.3 nm and a distinct pleochroism from yellow (//ω) to light blue (//ε). Electron microprobe analyses yielded (wt.%): Na₂O 2.73, K₂O 4.16, BeO 4.67, MgO 11.24, MnO 2.05, FeO 1.76, Al₂O₃ 0.15, SiO₂ 73.51, (Σ CaO, TiO₂ = 0.06) sum 100.33 (BeO determined by LA-ICP-MS). The empirical formula based on Si = 12 is K_0.87 Na_0.86 (Mg_1.57Mn_0.28Fe_0.24)_Σ2.09 (Be_1.83?Mg_1.17)_Σ3.00 [Si₁₂O₃₀], and the simplified formula can be given as K (□_0.5Na_0.5)₂ (Mg_0.8Mn_0.1Fe_0.1)₂ (Be_0.6?Mg_0.4)₃ [Si₁₂O₃₀]. Friedrichbeckeite is hexagonal, space-group P6/mcc, with a = 9.970(1), c = 14.130(3) Å, V = 1216.4(3) ų, and Z = 2. The strongest lines in the X-ray powder diffraction pattern are (d in Å / I _obs / hkl): 3.180 / 100 / 121, 2.885 / 70 / 114, 4.993 / 30 / 110, 4.081 / 30 / 112, 3.690 / 30 / 022. A single-crystal structure refinement (R1 = 3.62 %) confirmed that the structure is isotypic with milarite and related ^[12] C ^[9] B ₂ ^[6] A ₂ ^[4] T2₃ [^[4] T1₁₂O₃₀] compounds. The C-site is dominated by potassium, the B-site is almost half occupied by sodium, and the A-site is dominated by Mg. The site-scattering at the T2-site can be refined to a Be/(Be?+?Mg) value close to 0.61; the T1-site is occupied by Si. Micro-Raman spectroscopy reveals an increasing splitting of scattering bands around 550 cm^?1 for friedrichbeckeite. The mineral can be classified as an unbranched ring silicate or as a beryllo-magnesiosilicate. With respect to the end-member formula K (□0.5Na0.5)₂ Mg₂ Be₃ [Si₁₂O₃₀] friedrichbeckeite represents the Mg-dominant analogue of almarudite, milarite or oftedalite. The mineral and its paragenesis were formed during pyrometamorphic modifications of the silicate-rich xenoliths enclosed in Quaternary leucite-tephritic lava of the Bellerberg volcano. Holotype material of friedrichbeckeite has been deposited at the mineral collection of the Naturhistorisches Museum Wien, Austria. The mineral is named friedrichbeckeite in honour of the Austrian mineralogist and petrographer Friedrich Johann Karl Becke (1855–1931).     

Heavy metal concentrations in soils and plants in the vicinity of Arufu lead-zinc mine,Middle Benue Trough,Nigeria

This study focused on the influence of base metal mining on heavy metal levels in soils and plants in the vicinity of Arufu lead-zinc mine, Nigeria. Soil samples (0-15 cm depth) and plant samples were collected from cul-tivated farmlands in and around the mine, the unmineralized site and a nearby forest (the control site). The samples were analyzed for heavy metals (Fe, Zn, Mn, Cu, Pb, Cr and Cd) by Atomic Absorption Spectrophotometry (AAS). The physical properties of soils (pH and LOI) were also measured. Results showed that soils from cultivated farm-lands have neutral pH values (6.5-7.5), and low organic matter contents (10%). Levels of Zn, Pb and Cd in culti-vated soils were higher than the concentrations obtained from the control site. These heavy metals are most probably sourced from mining and agricultural activities in the study area. Heavy metal concentrations measured in plant parts decreased in the order of rice leavescassava tuberspeelings. In the same plant species, metal levels decreased in the order of ZnFeMnCuPbCrCd. Most heavy metals were found in plant parts at average concentrations normally observed in plants grown in uncontaminated soil, however, elevated concentrations of Pb and Cd were found in a few cassava samples close to the mine dump. A stepwise linear regression analysis identified soil metal contents, pH and LOI as some of the factors influencing soil-plant metal uptake.     

First Find of Ga-Bearing Minerals in Ores of Ural Massive Sulfide Deposits

Gallium-containing chlorite, mica, and magnetite (up to 14, 13, and 5–7 wt % of Ga) along with Ga hydroxides (oxyhydroxides?) were found for the first time in massive sulfide deposit in the Urals. The minerals identified within the cement of chalcopyrite–sphalerite breccias of the Shemur copper–zinc–massive sulfide deposit (Northern Urals) are associated with Ga-enriched sphalerite, chalcopyrite, and, less commonly, pyrite (33–364, 67–363, and 4–230 g/t, respectively).     

Paleoproterozoic anorogenic granitoids of the Zheltav sialic massif (Southern Kazakhstan): Structural position and geochronology

The basement of the Zheltav sialic massif (Southern Kazakhstan) is composed of different metamorphic rocks united into the Anrakhai Complex. In the southeastern part of the massif, these rocks form a large antiform with the core represented by amphibole and clinopyroxene gneissic granite varieties. By their chemical composition, dominant amphibole (hastingsite) gneissic granites correspond to subalkaline granites, while their petroand geochemical properties make them close to A-type granites. The U–Pb geochronological study of accessory zircons yielded an age of 1841 ± 6 Ma, which corresponds to the crystallization age of melts parental for protoliths of amphibole gneissic granites of the Zheltav Massif. Thus, the structural–geological and geochronological data make it possible to define the Paleoproterozoic (Staterian) stage of anorogenic magmatism in the Precambrian history of the Zheltav Massif. The combined Sm–Nd isotopic—geochronological data and age estimates obtained for detrital zircons indicate the significant role of the Paleoproterozoic tectono-magmatic stage in the formation of the Precambrian continental crust of sialic massifs in Kazakhstan and northern Tien Shan.     

Simultaneous transport of water and solutes under transient unsaturated flow conditions — A case study

The imbalance between incoming and outgoing salt causes salinization of soils and sub-soils that result in increasing the salinity of stream-flows and agriculture land. This salinization is a serious environmental hazard particularly in semi-arid and arid lands. In order to estimate the magnitude of the hazard posed by salinity, it is important to understand and identify the processes that control salt movement from the soil surface through the root zone to the ground water and stream flows. In the present study, Malaprabha sub-basin (up to dam site) has been selected which has two distinct climatic zones, sub-humid (upstream of Khanapur) and semi-arid region (downstream of Khanapur). In the upstream, both surface and ground waters are used for irrigation, whereas in the downstream mostly groundwater is used. Both soils and ground waters are more saline in downstream parts of the study area. In this study we characterized the soil salinity and groundwater quality in both areas. An attempt is also made to model the distribution of potassium concentration in the soil profile in response to varying irrigation conditions using the SWIM (Soil-Water Infiltration and Movement) model. Fair agreement was obtained between predicted and measured results indicating the applicability of the model.     

Paleozoic granitoid magmatism of the eastern part of the Central Asian Fold Belt and formation of large ore deposits

Evidence on the Paleozoic granitoids of the eastern part of the Central Asian Fold Belt (CAFB) was analyzed. A tectonic chart of orogenic belts was compiled. Sketch maps were constructed for the geodynamic settings of the formation of Paleozoic granitoids and the extensiveness of their occurrence. Two types of deep controlling structures were distinguished: zones of lithospheric faults and plumes, including the newly recognized Jiamusi-Bureya plume. It was sown that the distribution of large and superlarge Paleozoic ore deposits is related to these structures, primarily to plumes. Sites promising for large and superlarge deposits related to the Paleozoic granitoid magmatism were determined in the Russian Far East.