Soil Loss Mapping for Sustainable Development and Management of Land Resources in Warora Tehsil of Chandrapur District of Maharashtra: An Integrated Approach Using Remote Sensing and GIS

The study area is characterized by low and fluctuating rainfall pattern, thin soil cover, predominantly rain-fed farming with low productivity coupled with intensive mining activities, urbanization, deforestation, wastelands and unwise utilization of natural resources causing human induced environmental degradation and ecological imbalances, that warrant sustainable development and optimum management of land resources. Spatial information related to existing geology, land use/land cover, physiography, slope and soils has been derived through remote sensing, collateral data and field survey and used as inputs in a widely used erosion model (Universal Soil Loss Equation) in India to compute soil loss (t/ha/yr) in GIS. The study area has been delineated into very slight (<5 t/ha/yr), slight (5–10 t/ha/yr), moderate (10–15 t/ha/yr), moderately severe (15–20 t/ha/yr), severe (20–40 t/ha/yr) and very severe (>40 t/ha/yr) soil erosion classes. The study indicate that 45.4 thousand ha. (13.7% of TGA) is under moderate, moderately severe, severe and very severe soil erosion categories. The physiographic unit wise analysis of soil loss in different landscapes have indicated the sensitive areas, that has helped to prioritize development and management plans for soil and water conservation measures and suitable interventions like afforestation, agro-forestry, agri-horticulture, silvipasture systems which will result in the improvement of productivity of these lands, protect the environment from further degradation and for the ecological sustenance.     

Variation in U-238 and Th-232 enrichment in U-mineralized zone and geological controls on their spatial distribution,Singhbhum Shear Zone of India

The determination of the natural radioactivity has been carried out, by means of gamma-ray spectrometry, in exposed rock samples collected from various geological formations across the Singhbhum Shear Zone of India. The spatial variation in the concentration of primordial radionuclides reflects, in general, the geochemical variance among the analyzed rocks and affirms the earlier views on genesis of uranium mineralization. This study further speculates new possibilities of thorium depletion during shearing and metamorphism. All the obtained U-values were more than the worldwide average U-concentration (which is about 40 Bq/kg). Interestingly, U-concentration in mica schists from Singhbhum group of rocks and in slates and argillaceous quartzites from Iron Ore group of rocks was five to seven times higher than the global values. In contrast, the granites in study area showed comparatively lower U-concentration. The overall results suggest the control of complex metamorphism and shearing on U-distribution in the terrane. The contribution of ²³⁸U, ²³²Th and ⁴⁰K to the total radiation dose in the study area was found to be significant ranging from 110 to 310 nGy/h in comparison with the lower global, as well as Indian average values.     

Hydrogeochemical processes,mixing and isotope tracing in hard rock aquifers and surface waters from the Subarnarekha River Basin, (east Singhbhum District,Jharkhand State,India)

Geochemical observations, including major ion and trace element analysis, and isotopic tracing have been carried out in the Subarnarekha River system (northeastern India) during a surface-water- and groundwater-monitoring program aimed at evaluating impacts of mining. The aquifer is of fracture type. Groundwater flow conditions and pollutant transfer were observed through a network of 69 wells. δ¹⁸O and δ²H results suggest that transfer from rainfall towards groundwater storage through soils and the unsaturated zone is fast, without any major transformation like evaporation. The scatter of ⁸⁷Sr/⁸⁶Sr signatures in surface water and groundwater are explained by three end-members. One is compatible with rainwater inputs. The most mineralised end-member represents anthropogenic inputs (agricultural practices and ore processing). The third end-member, characterised by a high ⁸⁷Sr/⁸⁶Sr signature, is believed to be controlled by natural geochemical processes, although affected by human activities (e.g. drainage of mine waste). Potential flow paths, investigated north of the area, reveal that all groundwater types seem to evolve more in pockets than along a flow path. The limited extent of transfer and the predominance of natural phenomena help to explain the moderate level of groundwater contamination and the characteristics of surface water contamination by mining and the metallurgy industry.     

Modelling spatial anisotropy of gold concentration data using GIS-based interpolated maps and variogram analysis: Implications for structural control of mineralization

Linear trends of anomalously high gold values in the Florida Canyon gold deposit, Nevada have been identified using a combination of contour maps of gold (Au) concentration developed with a geographic information system (GIS) and variogram maps created using a geostatistical analysis package. These linear trends are interpreted to represent major fault zones that exerted a prinicipal control on gold mineralization and therefore imparted a spatial anisotropy to gold concentrations.     

Integrated models,scenarios and dynamics of climate,land use and common birds

Reconciling food, fiber and energy production with biodiversity conservation is among the greatest challenges of the century, especially in the face of climate change. Model-based scenarios linking climate, land use and biodiversity can be exceptionally useful tools for decision support in this context. We present a modeling framework that links climate projections, private land use decisions including farming, forest and urban uses and the abundances of common birds as an indicator of biodiversity. Our major innovation is to simultaneously integrate the direct impacts of climate change and land use on biodiversity as well as indirect impacts mediated by climate change effects on land use, all at very fine spatial resolution. In addition, our framework can be used to evaluate incentive-based conservation policies in terms of land use and biodiversity over several decades. The results for our case study in France indicate that the projected effects of climate change dominate the effects of land use on bird abundances. As a conservation policy, implementing a spatially uniform payment for pastures has a positive effect in relatively few locations and only on the least vulnerable bird species.     

High Temperature Mylonitization of Quartzofeldspathic Gneisses: Example from the Schirmacher Hills, East Antarctica

In the Schirmacher Hills, most of the ductile shearing took place under high to medium grade amphibolite facies metamorphism. The microstructure of the mylonites shows characteristic features of high temperature deformation and thus gives us an idea of deformation mechanisms of the constituent minerals at great crustal depth. The variation in microstructure of the sheared rock is partly due to heterogeneity of the intensity of strain from domain to domain, producing protomylonites, orthomylonites and ultramylonites. However, a large part of the microstructural variation has resulted from syn- to post-tectonic recrystallization and grain growth of constituent minerals. Both quartz and feldspar have deformed by crystal plastic processes with dominant grain boundary migration. The present aspect ratio of the feldspar grains is a result of various degrees of dynamic recrystallization along the grain boundary. The ratio varies between 1.5 and 2. Presence of exsolution lamellae in perthites and formation of myrmekite at the strained grains of K-feldspar suggest diffusion assisted dislocation creep. These mylonites are characterized by the presence of weakly strained or unstrained long quartz ribbons. The development of quartz ribbons with the absence of significant strain suggests grain recovery and grain growth during high temperature mylonitization. The growth of quartz ribbons took place by coalescing neighbouring grains both along and across the ribbon length. At the ultramylonite stage the fine-grained matrix of quartz and feldspar mostly accommodates the bulk strain.     

Genesis of wollastonite- and grandite-rich skarns in a suite of marble-calc-silicate rocks from Sittampundi, Tamil Nadu: constraints on the P–T–fluid regime in parts of the Pan-African mobile belt of South India

The Pan-African tectonothermal activities in areas near Sittampundi, south India, are characterized by metamorphic changes in an interlayered sequence of migmatitic metapelites, marble and calc-silicate rocks. This rock sequence underwent multiple episodes of folding, and was intruded by granite batholiths during and subsequent to these folding events. The marble and the calc-silicate rocks develop a variety of skarns, which on the basis of mineralogy; can be divided into the following types: Type I: wollastonite?+?clinopyroxene (mg#?=?71–73)?+?grandite (16–21 mol% Adr)?+?quartz?±?calcite, Type II: grandite (25–29 mol% Adr )?+?clinopyroxene (mg#?=?70)?+?calcite?+?quartz, and Type III: grandite (36–38 mol% Adr)?+?clinopyroxene (mg#?=?55–65)?+?epidote?+?scapolite?+?calcite?+?quartz. Type I skarn is 2–10 cm thick, and is dominated by wollastonite (>70 vol%) and commonly occurs as boudinaged layers parallel to the regional foliation Sn₁ related to the Fn₁ folds. Locally, thin discontinuous lenses and stringers of this skarn develop along the axial planes of Fn₂ folds. The Type II skarn, on the other hand, is devoid of wollastonite, rich in grandite garnet (40–70 vol%) and developed preferentially at the interface of clinopyroxene-rich calc-silicates layers and host marble during the later folding event. Reaction textures and the phase compositional data suggest the following reactions in the skarns: 1. calcite?+?SiO₂?→?wollastonite?+?V, 2. calcite?+?clinopyroxene?+?O₂?→?grandite?+?SiO₂?+?V, 3. scapolite?+?calcite?+?quartz?+?clinopyroxene?+?O₂?→?grandite?+?V and 4. epidote?+?calcite?+?quartz?+?clinopyroxene?+?O₂?→?grandite?+?V Textural relations and composition of phases demonstrate that (a) silica metasomatism of the host marble by infiltration of aqueous fluids (X_CO2?<?0.15) led to production of large volumes of wollastonite in the wollastonite-rich skarn whereas mobility of FeO, SiO₂ and CaO across the interface of marble and calc-silicate and infiltration of aqueous fluids (X_CO2?<?0.35) were instrumental for the formation of grandite skarns. Composition of minerals in type II skarn indicates that Al₂O₃ was introduced in the host marble by the infiltrating fluid. Interpretation of mineral assemblages observed in the interlayered metapelites and the calcareous rocks in pseudosections, isothermal P-X_CO2 and isobaric T-X_CO2 diagrams tightly bracket the “peak” metamorphic conditions at c.9?±?1 kbar and 750°?±?30°C. Subsequent to ‘peak’ metamorphic conditions, the rocks were exhumed on a steeply decompressive P–T path. The estimated ‘peak’ P–T estimates are inconsistent with the “extreme” metamorphic conditions (>11 kbar and >950°C) inferred for the Pan-African tectonothermal events from the neighboring areas. Field and petrological attributes of these skarn rocks are consistent with the infiltration of aqueous fluid predominantly during the Fn₁ folding event at or close to the ‘peak’ metamorphic conditions. Petrological features indicate that the buffering capacity of the rocks was lost during the formation of type I and II skarns. However, the host rock could buffer the composition of the permeated fluids during the formation of type III skarn. Aqueous fluids derived from prograde metamorphism of the metapelites seem to be the likely source for the metasomatic fluids that led to the formation of the skarn rocks.     

Phosphate minerals as a recorder of P-T-fluid regimes of metamorphic belts: example from the Palaeoproterozoic Singhbhum Shear Zone of the East Indian shield

The Arcuate Singhbhum Shear Zone (SSZ) forms an integral part and occurs at the southern fringe of the Palaeoproterozoic North Singhbhum Fold Belt (NSFB) of the East Indian Shield. Repeated folding, ductile shearing, and accompanying hydrothermal activities in the SSZ during the late Palaeoproterozoic (ca. 1.66–1.60 Ga) orogeny resulted in a highly tectonized ensemble of rocks including a suite of peraluminous kyanite-rich quartzite (KQR). Near Kanyaluka village, the KQR shows millimetre- to decimetre-thick alternation of kyanite- and quartz-rich bands. The banded rock is intensely sheared and is cross-cut by weakly deformed to undeformed kyanite-quartz veins. In many places, kyanite-rich bands show sea-green coloured pods rich in lazulite. Textural studies reveal that deformed kyanite and quartz grains are sequentially replaced by augelite and lazulite (X_Mg > 0.97) at the terminal phase of shearing in the SSZ. Modelling of observed textures and mineral compositions with the C-Space program shows the following augelite- and lazulite-forming reactions:

1. 1.829Kyanite + 0.998P + 1.5H₂O + 0.001Ca = 1Augelite + 1.666Al + 0.001 Mg + 1.822SiO₂ + 0.002Fe + 0.0002Na

2. 1.778Kyanite + 0.667Augelite + 1.294P + 1.011 Mg + 0.011Fe + 0.0001Na = 1Lazulite + 2.833Al + 1.78SiO₂ + 0.001 Ca

Stoichiometry of the balanced chemical reactions suggests that a significant amount of P, Mg, and H₂O were added to, and Al and SiO₂ were subtracted from, the host kyanite-rich rock to produce augelite and lazulite. Experimental studies in the system Al₂O₃-SiO₂-FeO-MgO-P₂O₅-H₂O and the results of quantitative geothermobarometry suggest that lazulite and augelite were formed in a narrow temperature (440 ± 40°C) and pressure (~6.3 ± 1 kbar) range. Ductile shearing along the SSZ channelized the P- and Mg-rich fluids that metasomatized the kyanite-rich bands and veins to produce lazulite. The inferred P-T conditions can be explained by burial of the studied rock under an ~25 km-thick thrust sheet of NSFB during the Palaeoproterozoic orogenesis.     

A paradoxical situation in determining relative competence from wavelength/arclength ratios within buckle folded multilayers

By measuring the ratio of wavelength to arclength of folds in closely associated disharmonically folded competent layers, it is possible to determine which layer has undergone a greater layer-parallel strain and has a smaller competence. This method may lead to a paradoxical situation. For example when foliated quartzite and mica schist layers are folded together, the mica schist laminae show a much larger buckle shortening than the quartzite layers. On the other hand, the geometry of folds in quartzite indicates that quartzite was more competent than the mica schist. The structure can be explained by different modes of buckling, general buckling in quartzite layers and internal buckling in strongly anisotropic mica schists.