Fluid evolution in quartz vein-hosted tungsten mineralization in Chhendapathar, Bankura District, West Bengal: Evidence from fluid inclusion study

Tungsten mineralization in Chhendapathar area is hosted by quartz veins that traverse mostly the metasediments in and around Jikhu Nala. Fluid inclusion microthermometric experiments reveal the presence of four distinct types of inclusions. These are: aqueous biphase, monophase carbonic, aqueouscarbonic and halite-bearing polyphase inclusions. Salinity-temperature variation points towards the presence of two fluids of contrasting salinities and both independently followed simple cooling paths without any indication of fluid mixing. The P-T of mineralization was calculated from the intersection of coexisting and coeval aqueous biphase, carbonic and halite-bearing inclusions. The deduced values range from 1.63kb/361°C to 2.30kb/385°C. However, the initial temperature must have been much higher as indicated from the high dissolution temperature (> 450°C) of halite. Transportation of tungsten in the high saline fluid was facilitated by cation-tungstate ion pairing, i.e., with the help of Na₂WO₄ and/or NaHWO₄ complexes. A rapid fall in solubility in such fluid with falling temperature (in the range of 300–400°C), and by occasional fluid-rock interaction triggered precipitation of wolframite.     

Subdivision and fragmentation of land holdings and their implication in desertification in the Thar Desert, India

Analysis of data at the household level in Khabra Kalan village in the Thar desert of India revealed that the land holding size is halved every 20–30 years due to subdivision of land holdings. The subdivision is caused by the equal sharing among sons at the time of inheritance based on the succession laws, and attributed to the increase in the village population. The shrinking land holdings resulted in a shortfall of food on small farms; 12% in cereals and 42% in pulses, promoted continuous cultivation and the increase of monoculture, and deteriorated the land productivity through its effect on the soil fertility and land management.     

Sequential sporadic-E layers at low latitudes in the Indian sector

A study of the formation and movement of sequential Sporadic-E layers observed during the night-time hours at two Indian low-latitude stations, SHAR(dip 10°N) and Waltair (dip 20°N) shows that the layer are formed around 19:00 h. IST at altitudes of ≈180 km. They descend to the normal E-region altitude of about 100 km in three to four hours and becomes blanketing type of Es before they disappear. However, the absence of these descending layers at an equatorial station, Trivandrum (dip 2°N) gives the experimental evidence for wind shear theory. The meridional neutral wind derived from the height variation of the F-layer showed significant poleward wind during the descent of these layers. Hence it is inferred that these layers are formed as a consequence of the convergence of plasma by the poleward wind and the equatorward propagating gravity waves (inferred from the height fluctuations of F-layer).     

Global Sensitivity Analysis Techniques for Probabilistic Ground Water Modeling

Global sensitivity analysis techniques are better suited for analyzing input-output relationships over the full range of parameter variations and model outcomes, as opposed to local sensitivity analysis carried out around a reference point. This article describes three such techniques: (1) stepwise rank regression analysis for building input-output models to identify key contributors to output variance, (2) mutual information (entropy) analysis for determining the strength of nonmonotonic patterns of input-output association, and (3) classification tree analysis for determining what variables or combinations are responsible for driving model output into extreme categories. These techniques are best applied in conjunction with Monte Carlo simulation-based probabilistic analyses. Two examples are presented to demonstrate the applicability of these methods. The usefulness of global sensitivity techniques is examined vis-a-vis local sensitivity analysis methods, and recommendations are provided for their applications in ground water modeling practice.     

An entropy-based investigation into the variability of precipitation

Employing the entropy concept spatial and temporal variability of precipitation time series were investigated for the State of Texas, USA. Marginal entropy was used to investigate the variability associated with monthly, seasonal and annual time series. Also, apportionment entropy and intensity entropy were used for investigating the intra-annual and decadal distributions of monthly and annual precipitation amounts and numbers of rainy days within a year and decade respectively. Finally, the Hurst exponent and the Mann–Kendall test were used to evaluate the long-term persistence and trend in the variability of precipitation. Distinct spatial patterns in annual series and different seasons were observed. The variability of precipitation amount as well as number of rainy days within a year increased from east to west of Texas. The results also indicated that highly disorderliness in the amount of precipitation and number of rainy days caused severe droughts during the 1950’s in whole of Texas.     

GPS Monitoring of the Tropical Storm Delta along the Canary Islands Track, November 28-29, 2005

In this article we analyze the variations of the Zenith Tropospheric Delay (ZTD) and its components, Zenith Hydrostatic Delay (ZHD) and Zenith Wet Delay (ZWD) recorded by the GPS reference stations in the area of the Canary Islands during the passing of the tropical storm Delta on November 28 and 29, 2005. During this event, we observed that all GPS stations experienced significant increases of the ZWD value of over 100 mm and a decrease in the ZHD values of about 30 mm. The increase of the normal ZWD values was detected several hours prior to the manifestation of the weather phenomena on the ground. We also noticed a connection between the maximum ZWD values observed and the temporal distribution of the rain. The observed variations of the tropospheric slant directional gradients correlate significantly with the variations in direction and intensity of the observed winds. The relation noted between the ZWD values and the tropospheric slant delay gradients with meteorological observables highlights the convenience of using existing or new GPS networks when studying weather phenomena such as severe cyclones.     

Basin-scale transmissivity and storativity estimation using hydraulic tomography

While tomographic inversion has been successfully applied to laboratory- and field-scale tests, here we address the new issue of scale that arises when extending the method to a basin. Specifically, we apply the hydraulic tomography (HT) concept to jointly interpret four multiwell aquifer tests in a synthetic basin to illustrate the superiority of this approach to a more traditional Theis analysis of the same tests. Transmissivity and storativity are estimated for each element of a regional numerical model using the geostatistically based sequential successive linear estimator (SSLE) inverse solution method. We find that HT inversion is an effective strategy for incorporating data from potentially disparate aquifer tests into a basin-wide aquifer property estimate. The robustness of the SSLE algorithm is investigated by considering the effects of noisy observations, changing the variance of the true aquifer parameters, and supplying incorrect initial and boundary conditions to the inverse model. Ground water flow velocities and total confined storage are used as metrics to compare true and estimated parameter fields; they quantify the effectiveness of HT and SSLE compared to a Theis solution methodology. We discuss alternative software that can be used for implementing tomography inversion.     

The potential contribution of wildlife sanctuary to forest conservation: A case study from binsar wildlife sanctuary

Forest vegetation of a protected area(Binsar Wildlife Sanctuary) in Kumaun region(west Himalaya) was analysed for structure,composition and representativeness across three different altitudinal belts,lower(1,600-1,800 m a.s.l.),middle(1,900-2,100 m a.s.l.) and upper(2,200-2,400 m a.s.l.) during 2009-2011 using standard phytosociological methods.Four aspects(east,west,north and south) in each altitudinal belt were chosen for sampling to depict maximum representation of vegetation in the sanctuary.Population structure and regeneration behaviour was analysed seasonally for two years to show the establishment and growth of tree species.A total of 147 plant species were recorded from the entire region of which 27 tree species were selected for detailed study.Highest number was recorded at upper(18 species),and lowest at lower altitudinal belt(15 species).The relative proportion of species richness showed higher contribution of tree layer at each altitudinal belt.The population structure,based on the number of individuals,revealed a greater proportion of seedling layer at each altitudinal belt.The relative proportion of seedlings increases significantly along altitudinal belts(p<0.05) while opposite trends were observed in sapling and tree layers.The density of sapling and seedling species varied non-significantly across seasons(p>0.05).The density values decreased in summer and increased during rainy season.As far as the regeneration status is concerned,middle and upper altitudinal belts showed maximum number of species with fair regeneration as compared to lower altitudinal belt.Overall density diameter distribution of tree species showed highest species density and richness in the smallest girth class and decreased in the succeeding girth classes.This study suggests that patterns of regeneration behaviour would determine future structural and compositional changes in the forest communities.It is suggested that the compositional changes vis-à-vis role of ‘New’ and ‘Not regenerating’ species need priority attention while initiating conservation activities in the sanctuary.This study calls for exploring other less explored Wildlife Sanctuaries in the Himalaya and across the world,to achieve overall biodiversity status in these protected areas and thus to justify their role in conserving biodiversity in the region.     

Assessment of expected damage on buildings subjected to Lorca earthquake through an energy-based seismic index method and nonlinear dynamic response analyses

The city of Lorca (Spain) was hit on May 11th, 2011, by two consecutive earthquakes of magnitudes 4.6 and 5.2 M \(_\mathrm{w}\) , causing casualties and important damage in buildings. Many of the damaged structures were reinforced concrete frames with wide beams. This study quantifies the expected level of damage on this structural type in the case of the Lorca earthquake by means of a seismic index \(I_{v}\) that compares the energy input by the earthquake with the energy absorption/dissipation capacity of the structure. The prototype frames investigated represent structures designed in two time periods (1994–2002 and 2003–2008), in which the applicable codes were different. The influence of the masonry infill walls and the proneness of the frames to concentrate damage in a given story were further investigated through nonlinear dynamic response analyses. It is found that (1) the seismic index method predicts levels of damage that range from moderate/severe to complete collapse; this prediction is consistent with the observed damage; (2) the presence of masonry infill walls makes the structure very prone to damage concentration and reduces the overall seismic capacity of the building; and (3) a proper hierarchy of strength between beams and columns that guarantees the formation of a strong column-weak beam mechanism (as prescribed by seismic codes), as well as the adoption of counter-measures to avoid the negative interaction between non-structural infill walls and the main frame, would have reduced the level of damage from \(I_{v}\) \(\,=\,\) 1 (collapse) to about \(I_{v}\) \(\,=\,\) 0.5 (moderate/severe damage).