Simple Electrical Logging Technique for Base Metal Exploration

—It is well known that electrical logs of boreholes can play a signi|fi|cant role in base metal exploration in identifying mineralised zones, especially when there is core loss or the borehole diameter is small or if drilling is by percussion. However, electrical logging is not widely utilised because of the additional burden on finances and time.¶A simple electrical logging technique, based on a pole-pole (hole-to-surface) configuration with one borehole electrode and nearly akin to the single point method, for S.P., resistivity and I.P. parameters, is presented. It is shown that it has the resolution of the single point method and the penetration of a very long normal sonde which is helpful for detection. Besides these features, the main advantage of this technique is that it can be easily carried out using ground I.P. (time domain) equipment.¶The electrical logs obtained in different base metal belts in Rajasthan, India, employing this technique and using ground I.P. equipment in connection with mise-à-la-masse surveys, illustrate the above features. A comparison with logs recorded by means of multi-electrode drill hole I.P. equipment of Scintrex, Canada, substantiates the same.     

Airborne measurements of submicron aerosols across the coastline at Bhubaneswar during ICARB

Airborne measurements of the number concentration and size distribution of aerosols from 13 to 700 nm diameter have been made at four vertical levels across a coastline at Bhubaneswar (20°25′N, 85°83′E) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) programme conducted in March–April 2006. The measurements made during the constant-level flights at 0.5, 1, 2 and 3 km altitude levels extend ～100 km over land and ～150km over ocean. Aerosol number concentrations vary from 2200 to 4500 cm^?3 at 0.5 km level but are almost constant at ～ 6000 cm^?3 and ～ 800 cm^?3 at 2 and 3 km levels, respectively. At 1km level, aerosol number concentration shows a peak of 18,070 cm^?3 around the coastline. Most of the aerosol size distribution curves at 0.5 km and 1 km levels are monomodal with a maxima at 110nm diameter which shifts to 70 nm diameter at 2 and 3 km levels. However, at the peak at 1 km level, number concentration has a bimodal distribution with an additional maximum appearing in nucleation mode. It is proposed that this maxima in nucleation mode at 1 km level may be due to the formation and transport of new particles from coastal regions.     

Genesis of secondary Mn-oxide ores in the Úrkút deposit, Hungary

The Úrküt Basin of western Hungary is well known for its early Jurassic Mn-carbonate deposit that is related genetically to Jurassic black shale formation. This carbonate deposit has undergone multistage oxidation during the Cretaceous that produced secondary Mn-oxides. Among the geochemical characteristics that distinguish the host sedimentary rocks and Mn-carbonates from the Mn-oxides is an extreme enrichment in Sr (up to 1%) without an observable independent Sr-phase. This enrichment indicates a special process of formation. The ¹⁸O values of these Mn-oxide ores fall between 1.5 and 5.5%. (VSMOW) showing a slight bimodal distribution. This isotopic variability is interpreted as a product of superposing effects of the interaction of surficial and deep-seated magmatic fluids. The ¹⁸O_MnO2 values (from 1.5 to 5.5%.), the assumed ¹⁸O_water values and formation temperatures fit well with the MnO₂-water fractionation curve based on the data of Yeh et al. (1985) and Hoefs et al. (1987).     

Integrating intensity–duration-based rainfall threshold and antecedent rainfall-based probability estimate towards generating early warning for rainfall-induced landslides in parts of the Garhwal Himalaya,India

In order to generate early warning for landslides, it is necessary to address the spatial and temporal aspects of slope failure. The present study deals with the temporal dimension of slope failures taking into account the most widespread and frequent triggering factor, i.e. rainfall, along the National Highway-58 from Rishikesh to Mana in the Garhwal Himalaya, India. Using the post-processed three-hourly rainfall intensity and duration values from the Tropical Rainfall Measuring Mission-based Multi-satellite Precipitation Analysis and the time-tagged landslide records along this route, an intensity–duration (I–D)-based threshold has been derived as I?=?58.7D ^?1.12 for the rainfall-triggered landslides. The validation of the I–D threshold has shown 81.6 % accuracy for landslides which occurred in 2005 and 2006. From this result, it can be inferred that landslides in the study area can be initiated by continuous rainfall of over 12 h with about 4-mm/h intensity. Using the mean annual precipitation, a normalized intensity–duration relation of NI?=?0.0612D ^?1.17 has also been derived. In order to account for the influence of the antecedent rainfall in slope failure initiation, the daily, 3-day cumulative, and 15- and 30-day antecedent rainfall values associated with landslides had been subjected to binary logistic regression using landslide as the dichotomous dependent variable. The logistic regression retained the daily, 3-day cumulative and 30-day antecedent rainfall values as significant predictors influencing slope failure. This model has been validated through receiver operating characteristic curve analysis using a set of samples which had not been used in the model building; an accuracy of 95.1 % has been obtained. Cross-validation of I–D-based thresholding and antecedent rainfall-based probability estimation with slope failure initiation shows 81.9 % conformity between the two in correctly predicting slope stability. Using the I–D-based threshold and the antecedent rainfall-based regression model, early warning can be generated for moderate to high landslide-susceptible areas (which can be delineated using spatial integration of preconditioning factors). Temporal predictions where both the methods converge indicate higher chances of slope failures for areas predisposed to instability due to unfavourable geo-environmental and topographic parameters and qualify for enhanced slope failure warning. This method can be verified for further rainfall seasons and can also be refined progressively with finer resolutions (spatial and temporal) of rainfall intensity and multiple rain gauge stations covering a larger spatial extent.     

The Neogene/Quaternary boundary in India: A review

The Neogene/Quaternary boundary has been variously defined in different continents. A global review of the problem shows that only the Olduvai event on the palaeomagnetic timescale may provide an universally acceptable isochronous datum for delineating this boundary. The N/Q boundary in the Siwaliks, Kashmir and the Andamans in India is defined in the light of recent research.     

Assessments of Potential Spatial‐temporal Variations in Phosphorus Distribution and Fractionation in River Bed Sediments

Sediment characteristics influence the distribution and bioavailability of phosphorus (P) in river sediments. In this study, we analyzed different P fractions in the sediments of the Bronx River, New York City, NY, using sequential extraction. The results showed that the average P pool rank order was HCl?P > NaOH?P > NaHCO₃?P > residue?P, and their relative proportions were 3.7: 2.0: 1.4: 1 in sediments collected in 2006, while HCl?P > NaOH?P > residue?P > NaHCO₃?P, with their relative proportions of 27.8:6.2:2.7:1 in the sediments obtained in 2007. The strong correlation between microbial P and organic P (OP), along with the changes in microbial P over time indicate that most of the OP in the river bed sediments is potentially bioavailable. The sediment transport, deposition, assimilation, the exchange of P between sediments and water columns, the land use changes, raw sewer discharge, gas spill, construction, fertilizer application, etc., as well as the hydro‐climatic changes could result in the spatial and temporal variations in P bioavailability in the river bed sediments. The estimations of P pools and their bioavailability in river bed sediments could help determine the spatial and temporal variations in P transport and impacts of land use on water quality, in turn, help regulate P in the river's watershed.     

New class of regular and well behaved exact solutions in general relativity

We present a new class of spherically symmetric regular and well behaved solutions of the general relativistic field equations in isotropic coordinates. These solutions describe perfect fluid balls with positively finite central pressure and positively finite central density; their ratio is less than one and causality condition is obeyed at the centre. The solutions of this class, the outmarch of pressure, density pressure-density ratio and the ratio of sound speed to light is monotonically decreasing. Keeping in view of well behaved nature in terms of central red shift and surface red shift and by assuming the surface density ρ _b =2×10¹⁴ g/cm³, we constructed a Neutral star model for k=2, resulting into maximum mass ≈6.36M _Θ, linear dimension ≈48.08 km, surface red shift ≈1.132 and central red shift ≈17.1314.     

Neodymian goyazite in the bauxite deposit of Vlasenica,Yugoslavia

Summary Electron probe analysis of a bauxite sample with the highest content of the rare earth elements from the Nazda bauxite deposit in the Vlasenica bauxite-bearing area, revealed the presence of neodymian goyazite, a mineral of the crandallite group. Its composition lies between goyazite, florencite and crandallite, and can be described asCn ₂₄Fc₃₃Gz₄₃. The first analyses of this mineral in bauxites are presented and the genesis is discussed.

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Nd-haltiger Goyazit im Bauxitlager von Vlasenica, Jugoslawien

Zusammenfassung Ein Mineral der Crandallitgruppe, Neodym-Goyazit, wurde mittels Mikrosondenanalysen aus dem mit höchsten Gehalten an Seltenen Erden gekennzeichneten Nazda Bauxitlager im Vlasenica Bauxitgebiet identifiziert. Die Zusammensetzung liegt zwischen Goyazit, Florencit und Crandallit und kann mitCn ₂₄Fc₃₃Gz₄₃ angegeben werden. Ein Überblick über die ersten Analysen dieses Minerals von Bauxitlagerstätten und seinen Ursprung wird hiermit gegeben.

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With 3 Figures