Implications of REE incorporation and host sediment influence on the origin and growth processes of ferromanganese nodules from Central Indian Ocean Basin

This study presents new major, trace and REE data for thirty-five ferromanganese nodules recovered from areas representing three different sediment types (silic...     

Contrasting Episodes of Regional Granulite-Facies Metamorphism in Enclaves and Host Gneisses from the Aravalli Delhi Mobile Belt, NW India

The Aravalli–Delhi Mobile Belt in the northwestern partof India demonstrates how granulite enclaves and their hostgneisses can be utilized to unravel multistage metamorphic historiesof orogenic belts, using three suites of metamorphic rocks:(1) an enclave of pelitic migmatite gneiss–leptynite gneiss;(2) metamorphosed megacrystic granitoids, intrusive into theenclave; (3) host tonalite–trondhjemite–granodiorite(TTG) gneisses associated with an interlayered sequence of garnetiferousmetabasite and psammo-pelitic schist, locally migmatitic. Basedon integrated structural, petrographic, mineral compositional,geothermobarometric studies and P–T pseudosection modellingin the systems NCKFMASH and NCFMASH, we record three distincttectonothermal events: an older, medium-pressure granulite-faciesmetamorphic event (M₁) in the sillimanite stability field, whichis registered only in the enclave, a younger, kyanite-gradehigh-pressure granulite-facies event (M₂), common to all thethree litho-associations, and a terminal amphibolite-faciesmetamorphic overprint (M₃). The high-P granulite facies eventhas a clockwise P–T loop with a well-constrained prograde,peak (M₂, P 12–15 kbar, T 815°C) and retrograde (M_2R,6·1 kbar, T 625°C) metamorphic history. M₃ is recordedparticularly in late shear zones. When collated with availablegeochronological data, the metamorphic P–T conditionsprovide the first constraint of crustal thickening in this belt,leading to the amalgamation of two crustal blocks during a collisionalorogeny of possible Early Mesoproterozoic age. M₃ reactivationis inferred to be of Grenvillian age. KEY WORDS: Northwestern India; polycyclic granulite enclave; pseudosection; high-pressure metamorphism; P–T path     

http://www.sciencedirect.com/science/article/pii/S1674987114000899

The Rajahmundry Trap Basalts（RTB） are erupted through fault-controlled fissures in the Krishna-Godavari Basin（K-G Basin） of Godavari Triple Junction,occurring as a unique outcrop sandwiched between Cretaceous and Tertiary sediments along the east coast of India.Detailed geochemical studies have revealed that RTB are mid-Ti（1.74-1.92） to high-Ti（2.04-2.81） basalts with a distinct quartz tholeiitic parentage.MgO（6.2-13.12 wt.%）,Mg^#（29-50） and Zr（109-202 ppm） suggest that these basalts evolved by fractional crystallization during the ascent of the parent magma along deep-seated fractures.Moderate to high fractionation of HREE,as indicated by（Gd/Yb）N ratios（1.71-2.31） of RTB,suggest their generation through 3-5%melting of a Fe-rich mantle corresponding to the stability fields of spinel and garnet peridotite at depths of 60-100 km.Low K₂O/P₂O₅（0.26-1.26）,high TiO₂/P₂O₅（6.74-16.79）,La/Nb（0.89-1.45）,Nb/Th > 8（8.35-13）,negative anomalies at Rb reflect minimum contamination by granitic continental crust.（Nb/La）_PM ratios（0.66-1.1） of RTB are attributed to endogenic contamination resulted through recycling of subducted oceanic slab into the mantle.Pronounced Ba enrichment with relative depletion in Rb indicates assimilation of Infra- and Inter-trappean sediments of estuarine to shallow marine character.Geochemical compositions such as Al₂O₃/TiO₂（3.88-6.83）,medium to high TiO₂（1.74-2.81 wt.%）.positive Nb anomalies and LREE enrichment of these RTB attest to their mantle plume origin and indicate the generation of parent magma from a plume-related enriched mantle source with EM 1signature.Ba/Th（46-247）,Ba/La（3.96-28.51） and Th/Nb（0.08-0.13） ratios suggest that the source enrichment process was marked by recycling of subduction-processed oceanic crust and lithospheric components into the mantle.Zr/Hf（37-41） and Zr/Ba（0.51-3.24） indicate involvement of an asthenospheric mantle source.The Rajahmundry basalts show affinity towards FOZO（focal zone mantle） and PSCL（post-Archaean subcontinental lithosphere） which reflect mixing between asthenospheric and lithospheric mantle components in their source.Origin of RTB magma is attributed to plume-lithosphere interaction and the upward movement of melt is facilitated by intrabasinal deep-seated faults in the K-G Basin.     

Lidar observation of aerosol stratification in the lower troposphere over Pune during pre-monsoon season of 2006

Lidar observations of aerosol vertical distributions in the lower troposphere along with observations of horizontal and vertical winds from collocated UHF radar (Wind Profiler) over a tropical Indian station, Pune during the pre-monsoon season (March–May) of 2006 as part of an ISRO-GBP national campaign (ICARB) have been examined. Lidar vertical profiles showed high aerosol concentrations in the surface layers and a subsequent gradual decrease with height. Results showed the presence of an elevated stratified aerosol layer around 2000–3500m height which persisted throughout the months of March and April. Observed strong vertical gradients in both horizontal and vertical winds in the lower troposphere seem to be a possible cause for the formation of elevated aerosol layers. Further, high daytime temperatures accompanied by dry conditions at the surface help to enhance the aerosol loading in the lower layers over this location.     

Assessment of heavy metal pollution in surface water

A total of 96 surface water samples collected from river Ganga in West Bengal during 2004–05 was analyzed for pH, EC, Fe, Mn, Zn, Cu, Cd, Cr, Pb and Ni. The pH was found in the alkaline range (7.21–8.32), while conductance was obtained in the range of 0.225–0.615 mmhos/cm. Fe, Mn, Zn, Ni, Cr and Pb were detected in more than 92% of the samples in the range of 0.025–5.49, 0.025–2.72, 0.012–0.370, 0.012–0.375, 0.001–0.044 and 0.001–0.250 mg/L, respectively, whereas Cd and Cu were detected only in 20 and 36 samples (0.001–0.003 and 0.003–0.032 mg/L). Overall seasonal variation was significant for Fe, Mn, Cd and Cr. The maximum mean concentration of Fe (1.520 mg/L) was observed in summer, Mn (0.423 mg/L) in monsoon but Cd (0.003 mg/L) and Cr (0.020 mg/L) exhibited their maximum during the winter season. Fe, Mn and Cd concentration also varied with the change of sampling locations. The highest mean concentrations (mg/L) of Fe (1.485), Zn (0.085) and Cu (0.006) were observed at Palta, those for Mn (0.420) and Ni (0.054) at Berhampore, whereas the maximum of Pb (0.024 mg/L) and Cr (0.018 mg/L) was obtained at the downstream station, Uluberia. All in all, the dominance of various heavy metals in the surface water of the river Ganga followed the sequence: Fe > Mn > Ni > Cr > Pb > Zn > Cu > Cd. A significant positive correlation was exhibited for conductivity with Cd and Cr of water but Mn exhibited a negative correlation with conductivity.     

On the tidally driven circulation in the South China Sea: modeling and analysis

The South China Sea is a large marginal sea surrounded by land masses and island chains, and characterized by complex bathymetry and irregular coastlines. An unstructured-grid SUNTANS model is employed to perform depth-averaged simulations of the circulation in the South China Sea. The model is tidally forced at the open ocean boundaries using the eight main tidal constituents as derived from the OSU Tidal Prediction Software. The model simulations are performed for the year 2005 using a time step of 60 s. The model reproduces the spring-neap and diurnal and semidiurnal variability in the observed data. Skill assessment of the model is performed by comparing model-predicted surface elevations with observations. For stations located in the central region of the South China Sea, the root mean squared errors (RMSE) are less than 10 % and the Pearson’s correlation coefficient (r) is as high as 0.9. The simulations show that the quality of the model prediction is dependent on the horizontal grid resolution, coastline accuracy, and boundary locations. The maximum RMSE errors and minimum correlation coefficients occur at Kaohsiung (located in northern South China Sea off Taiwan coast) and Tioman (located in southern South China Sea off Malaysia coast). This may be explained with spectral analysis of sea level residuals and winds, which reveal dynamics at Kaohsiung and Tioman are strongly influenced by the seasonal monsoon winds. Our model demonstrates the importance of tidally driven circulation in the central region of the South China Sea.     

Adsorption Kinetic Modeling of Safranin onto Rice Husk Biomatrix Using Pseudo‐first‐ and Pseudo‐second‐order Kinetic Models: Comparison of Linear and Non‐linear Methods

Batch kinetic studies were carried out for the removal of safranin from aqueous solution using a biomatrix prepared from rice husk. The adsorption kinetic data were modeled using the pseudo‐first‐order and pseudo‐second‐order kinetic equations. The linear and non‐linear forms of these two widely used kinetic models were compared in this study. In order to determine the best‐fitting equation, the coefficient of determination (r²), the sum of the squares of the errors (SSE), sum of the absolute errors (SAE), average relative error (ARE), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), and the Chi‐squared test (χ²) were used as error analysis methods. Results showed that the non‐linear forms of pseudo‐first‐order and pseudo‐second‐order models were more suitable than the linear forms for fitting the experimental data. Non‐linear method is thus more appropriate for estimating the kinetic parameters and should primarily be used to describe adsorption kinetics.     

An approach for GIS-based statistical landslide susceptibility zonation—with a case study in the Himalayas

Landslide susceptibility zonation (LSZ) is necessary for disaster management and planning development activities in mountainous regions. A number of methods, viz. landslide distribution, qualitative, statistical and distribution-free analyses have been used for the LSZ studies and they are again briefly reviewed here. In this work, two methods, the Information Value (InfoVal) and the Landslide Nominal Susceptibility Factor (LNSF) methods that are based on bivariate statistical analysis have been applied for LSZ mapping in a part of the Himalayas. Relevant thematic maps representing various factors (e.g., slope, aspect, relative relief, lithology, buffer zones along thrusts, faults and lineaments, drainage density and landcover) that are related to landslide activity, have been generated using remote sensing and GIS techniques. The LSZ derived from the LNSF method, has been compared with that produced from the InfoVal method and the result shows a more realistic LSZ map from the LNSF method which appears to conform to the heterogeneity of the terrain.     

Mineralogical study of gabbro-anorthosite from Dumka, Chhotanagpur Gneissic Complex, Eastern Indian Shield

The Chhotanagpur Gneissic Complex (CGC), bearing imprints of widespread high grade metamorphic and magmatic history since Palaeoproterozoic, represents an integral crustal segment of Eastern Indian Shield. The gabbroanorthosite intrusives constitute a part of mafic-ultramafic magmatism in the CGC. The study area around Dumka (24°16?? to 24°20??N: 87°13?? to 87°22??E) predominantly comprises of granite gneiss and charnockitic country rocks within which gabbro-anorthosite intrusions occur as lenses. Field relations and structural studies reveal that the country rocks of Dumka have suffered three phases of deformation represented by F₁, F₂ and F₃ folds. The gabbro-anorthosite intrusives maintain a sharp contact with the host rocks, deformed and metamorphosed. Relict igneous layering or primary igneous foliation (S_ig) is recorded where metamorphic overprint is minimal. Mineral phases of gabbro-anorthosite rocks suggest that clinopyroxene compositions from gabrro correspond to diopside and clinoferrosilite, while those from anorthosite are clinoferrosilite. Amphiboles from the gabbro-anorthosite rocks are calcic, and range from ferroan pargasite in gabbro to ferroan pargasitic hornblende in anorthosite. Plagioclase from gabbro and anorthosite belong to bytownite and andesine respectively. Chemical composition of garnet in gabbro is almandine. Thermobarometric estimates for Dumka gabbroanorthosites correspond to 511°C to 915°C and 5.0?C7.5 kb pressure, comparable to that estimated for Bengal Anorthosite (593?C795°C, 4.1?C7.3 kb). Fractionation trend of plagioclase substantiates a single parental magma in the evolution of Dumka gabbro-anorthosite intrusives.     

Tropospheric ozone profiles near equator and meteorological parameters

This is a study of ozone profile shapes in the 800 to 100 millibar range obtained with balloonsonde data over Trivandrum (8.5° N) during 1975–76 and possible associations of these shapes to some meteorological parameters.Whereas monotonic ozone profiles were noted with clear weather conditions, those associated with cloud cover show three basic anomalous features. Some bulges of increased values are observed in the range of 800 to 500 mb. In the 500–100 mb range, short range or localized cloud cover or passing weather disturbances are associated with fluctuation patterns in the ozone profile and an average depleted value of ozone. The fluctuations are also associated with changing wind speed and direction at these heights.Possible causative mechanisms are discussed. Lightning associated with thundestorm, producing additional CO and NO are sought to interpret the bulges at lower heights. The decrease in values as well as the fluctuation patterns are suggested as due to possible incursion of water vapour from troposphere to stratosphere in the tropical region and dynamical effects associated with it.