Mineral chemistry of clays associated with the Jhilmili intertrappean bed in the eastern Deccan volcanic province: Palaeoenvironmental inferences and KTB transition

Jhilmili intertrappean bed (～13 m thick) attains its significance with the recent discovery of brackish water ostrocod and planktonic foraminifera fossils (Keller et al. 2009; Khosala et al. 2009). Present XRD data revealed abundance of montmorillonite > montmorillonite/chlorite mixed layer > palygorskite in five physically distinct lithounits namely: (a) lower chocolate brown siltstone with green patches, followed by (b) brick red clayey siltstone, (c) greenish grey clay, (d) yellowish brown clay and (e) uppermost olive grey to dark brown silt layers in the successionrepresent higher weathering indices and annual precipitation, reflecting cyclic, but longer spells of weathering. Occurrence of M/C mixed layer with the smectite in Jhilmili area is suggestive of their derivation from the later, whilst montmorillonite to palygorskite transformation is ascribed to the drastic changes in the humid to arid climate, where former served as a source of Al and some of the Si and Mg ions for the later. Jhilmili and Anjar clays represent similar charge occupancies at different sites, but later contains relatively higher amount of palygorskite, formed in the arid environment. Majority of the trace elemental data plots for Jhilmili clays lie within the upper and lower limits of infra (Lametas)-/inter-trappeans clays. The continuous release of Cu throughout the succession (mainly in the palygorskite dominated clays) indicates oxidizing conditions. PAAS normalized REE data plots for these clays show progressive enrichment in the HREE contents in the lower part, but, upper part of the succession is marked by positive cerium anomaly, reflecting oxidizing conditions prevailed at the later stage of the succession. These conditions continued, but, were not conducive to HREE enrichment as evidenced by their depletion in the upper part of the succession. The Ce anomaly observed in the middle part of the succession is similar to that form by continental weathering of the basalt, ascribed to Ce precipitation in the oxic environment, thus suggestive of drastic changes in the oxidizing conditions. Thermodynamic data-sets for Jhilmili clays show I/S mixed layer and celadonite compositions, whereas, Jabalpur infra-/inter-trappean clays correspond to Mg smectites and celadonite end members, thus, representing compositional commonality with those of the other clays derived from the continental weathering of basalt protolith. Jhilmili smectites and smectite-chlorite mixtures show compositional similarity with the dioctahedral and trioctahedral smectites and the smectites formed at 250°C, having compositions between trioctahedral smectite and chlorite, thus, assigning high temperatures for their formation, where the heat required for the formation of these clays was possibly derived from the hydrothermal fluids, associated with the Deccan volcanism.     

Geochemistry of Proterozoic granitoids exposed between Dirang and Tawang, western Arunachal Himalaya, north-eastern India: petrogenetic and tectonic significance

Major and trace element geochemistry of Proterozoic granitoids from the Dirang and Galensiniak Formations, of Lesser and Higher Himalayas, respectively, emplaced in and around Dirang and Tawang regions of the western Arunachal Himalaya, is discussed. In general, these granitoids are massive as well as foliated in nature and are characterized by granitic mineralogical compositions. Porphyritic and hypidiomorphic textures are common in massive type, whereas others show porphyroblastic and foliated textures. Augen structure is also observed in a number of samples. Geochemical and normative compositions together with petrographic features classify them as peraluminous granitoids. Major and trace element geochemistry of most of these granitoids shows granitic nature, while few samples also show monzonitic characteristics. Observed geochemical characters, such as their peraluminous and alkali-calcic/calcic-alkalic nature, crudely defined geochemical patterns, different multi-element and rare-earth element patterns, together with low Mg# (Mg number) of these granitoids suggest their derivation from lower crustal material rather than a mantle source. Multi-element and rare-earth element patterns corroborate their genesis from different crustal melts. It is difficult to explain variations observed in granitoid rocks by partial melting alone; definitely different other processes like migration of melts, magma mixing, assimilation and fractional crystallization also played important role in the genesis of these granitoids. These melts were likely generated at low temperature (730–760 °C) and low pressure (2–5 GPa). The chemical compositions suggest that most of these Paleoproterozoic granitoids are emplaced within the syn-collisional tectonic setting, while few granitoid samples also indicate their volcanic-arc nature. Probably, later group of granitoids are slightly younger to the syn-collisional type.     

Petrographic Characteristics and Alteration Geochemistry of Granite-hosted Tungsten Mineralization at Degana, NW India

Abstract. Vein type tungsten mineralization at Degana is genetically and spatially associated with the Degana Granite. The deposit is characterized by pervasive wall rock alteration around the mineralized quartz veins. Laterally three different alteration zones, greisen, silicification and potassic zones, are marked based on the field features, mineral assemblages and geo-chemical characteristics. In the present paper, systematic mineralogical and chemical variation in these alteration zones is reported. Thick mono-mineralic (zinnwaldite) selvages around the veins characterize the deposit. Plagioclase and alkali feldspar are low in the greisen zones while K-feldspar shows more increase than plagioclase in the potassic zone. Quartz is uniformly high in all the alteration zones, but it shows an anomalous value in the silicification zone. Al₂O₃ concentration shows initial depletion in greisen zone with gradual increase away from the contact. MgO and FeO are higher in greisen zone than silicification and potassic zones. The potassic zone is characterized by the depletion of Na₂O and higher value of K₂O.
The common presence of topaz and fluorite as both primary and secondary minerals and fluorine-bearing micas suggest fluorine partitioning in substantial amount between granitic melt and coexisting aqueous fluid phase and higher HF activity during the evolution of hydrothermal fluid. The mutual relationship of the fluorine minerals (topaz and fluorite) in the different alteration zones suggests an increase in the Ca²⁺ activity and decrease of H+ activity during the fluid evolution from greisenization towards alkali-metasomatised granite and the fluid is assumed to change from low to high activity ratio of Ca²⁺/H+.     

Prediction of SST anomalies of east Pacific Ocean (Nino 3 region) using a statistical model

Summary  Average SST anomalies of OCT-DEC months for Nino-3 region are predicted using the following parameters – (i) April rain over Himachal Pradesh, (ii) Darwin pressure change (January–April), (iii) Southern Oscillation Index (Tahiti–Darwin) and (iv) SST anomalies of Nino-3 region in the month of May. Principal component analysis is used to orthogonalise the predictors before using them in the regression equation. The first two principal components, which explain nearly 73% of the variance, are used to fit a regression line. The period 1951–1985 is used as the calibration period for the model and the period 1986–1997 as the verification period for the forecast. The Brier score with respect to a reference forecast (persistence) for the independent period is found to be 0.82 which is indicative of good forecast skill. Received April 1, 1999 Revised January 17, 2000     

Further notes on the associated alpha-functions and related integrals in the theory of the light changes of eclipsing variables

With a view to furthering the theory of the light changes of eclipsing variables, developed before systematically by Z. Kopal, this paper presents a number of new (and computable) expressions for the associated alpha-function _n ⁰ ,(r₁,r₂,) (and also for its partial derivatives), where _n ⁰ ,(r₁,r₂,) represents the fractional loss of light suffered by an eclipse of a circular disc of fractional radiusr ₁ (and darkened at the limb to thenth degree) by an opaque disc of radiusr ₂, with their centres separated by a fractional (projected) distance , provided that the transparency of the occulting disc increases with the angle of foreshortening in the same manner as the limb-darkening of the eclipsed star (that is, when the transparency functiong(, ) of the second aperture is given by Equation (4) below). Many of the explicit expressions derived here are valid for any type of eclipse, occultation or transit, regardless of whetherr ₁>r ₂ orr ₁<r ₂. and for any degreen of the adopted law of limb-darkening. It is also pointed out how some of the results obtained in this paper are related to the various representations given earlier in the literature for the case =0.     

Dynamicity of the Himalayan landslide — A tectono-geotechnical appraisal of the 13<Superscript>th</Superscript> mile landslide,Sikkim

Understanding the causes of slope development with movement initiation of land sliding requires knowledge on dynamicity, displacement, strain concentration and factor of safety. The 13^th mile landslide on Gangtok-Nathula road of the Sikkim Himalaya has seriously affected the Indo-China trade route. To quantify the spatial movement pattern, strain analysis and identification of zones of safety were attempted which indicates that differential movement activity of the landslide zone is co-relatable with differential strain pattern with an overall imprint of the Himalaya collision tectonics.     

Electro-chemical mineralization of recalcitrant indole by platinum-coated titanium electrode: multi-response optimization,mechanistic and sludge disposal study

Indole is a highly recalcitrant aromatic heterocyclic organic compound consisting of a five-membered nitrogen-containing pyrrole ring fused to a six-membered benzene ring. This study presents the results of the electro-chemical mineralization of indole in an aqueous solution using platinum-coated titanium (Pt/Ti) electrode. A central composite design was used to investigate the effect of four parameters namely initial pH (pH_o), current density (j), conductivity (k) and treatment time (t) at 5 levels. Multiple responses namely chemical oxygen demand (COD) removal (Y ₁) and specific energy consumption (Y ₂) were simultaneously maximized and minimized, respectively, by optimizing the parameters affecting the mineralization of indole by using the desirability function approach. At the operating conditions of pH 8.6, j = 161 A/m², k = 6.7 mS/cm and t = 150 min, 83.8% COD removal with specific energy consumption of 36.3 kWh/kg of COD removed was observed. Ultra performance liquid chromatography, UV–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry of the indole solution were performed at the optimum condition of the treatment so as to report a plausible mechanism of indole degradation. Field emission scanning electron microscopy analysis of electrodes before and after treatment was performed for determining the changes on anode surface during the treatment. Thermal analysis of the solid residue (scum) obtained was also performed for exploring its disposal prospects. Present study shows that electro-chemical oxidation can be used for mineralization of nitrogenous heterocyclic compounds such as indole.     

Relationship in metastasis of coal fire and land use/cover using thermal imagery and support vector machine classifier

The objective of the present study was to delineate temporal and spatial changes in the coal fire and land use/cover within Bastacolla area of Jharia coal field. Studying this variation helped to decipher interconnection among the dynamics of the coal fire and concomitant changes in land use/cover. The detection of coal fires during a span of 14 years along with transitioning land use/cover was cost-effective and enabled planning for management of coal resources and environment. Landsat series of satellite data of 2002, 2009, 2013, and 2016 were processed for generating land surface temperature profiles vis-a-vis classified land use/cover of the study area. A single cut-off temperature was derived for mapping of coal fires using land surface temperature profile from 2002 to 2016. The satellite images were classified using support vector machines, and for depicting land use/cover change, post-classification change detection was done. Classification accuracy obtained was excellent with kappa coefficient ranging from 0.897 for classified image of 2002 to 0.799 for classified image of 2016. Results revealed that coal fires had shifted to the central west part of the area. Furthermore, pockets of coal fire from northern and eastern part of the study area have diminished. OB dumps and coal quarry/coal dump may be attributed towards the spatial change in coal fire while; OB dumps showed connotation with the highest temperature zones. Ground verifications for temperature profiles and coal fires were carried out using thermal camera which enunciated good agreement with results.     

Calibration of AGRS System Using Transportable Pads in India: An Application to AGRS Data of Aravalli Basin,Banswada Block,South Rajasthan

Calibration of airborne gamma ray spectrometric system (AGRS) over standard radioactive sources of known elemental abundances is essential before carrying out airborne surveys. In India, fixed calibration pads were constructed in 1985. Since then calibration of AGRS system was carried out over the fixed pads. However the fixed pads are expensive to build and maintain. Also the large pads are subject to variations in radiation output due to variable moisture content and radon loss. Alternate approach is to construct transportable calibration pads which are discussed in this paper.Atomic Minerals Directorate for Exploration & Research (AMD) under Department of Atomic Energy has recently constructed five transportable calibration pads. Three pads i.e. K, U and Th have been spiked with the respective radioelements while keeping the minor radioelements to the least in order to obtain pure spectra. A composite pad has been constructed which contains all the three radioelements. This helps in cross verifying the obtained calibration results. A background pad has also been constructed which is helpful to obtain the background values during calibration.Analysis of the data acquired over the transportable pads with airborne gamma ray spectrometer (16.8 ltr) has been carried out and presented in this paper. A comparison with the data acquired over the fixed calibration pads is also included. There is a good agreement of results which suggests the use of transportable pads in future.