Depositional history of Luna 24 drill core soil samples

Six soil samples from various depths of the Luna 24 drill core column have been analysed for their particle track records and light noble gas compositions. The observed particle track records indicate higher degree of maturity for the upper zone (～1 m) of this regolith column as compared to the soils in the lower zone (～0.4 m). The cosmogenic²¹Ne concentrations decrease rapidly with depth to 1 m, after which the concentrations level off or increase slightly. These data suggest a multi-stage depositional history for this drill core soil column consisting of: (1) rapid deposition of regolith material, (2) a cratering event about 400 m.y. B.P., leading to excavation to a depth of ～1 m from the present regolith surface, (3) a relatively rapid fill up of the crater with near-surface irradiated material, and (4) in-situ irradiation during the last about 250–300 m.y. Such a depositional sequence can also explain the observed lack of correlation between different surface exposure-correlated maturity indices in these drill core soil samples.     

Leaching behavior of lignite fly ash with shake and column tests

The maximum concentration of the majority of the trace metals in the leachates from shake and column test of lignite fly ash (LFA) was within the prescribed limits; however, total dissolved solids, total hardness, cations and anions (except K⁺), being above the prescribed limits, may lead to the increase in the hardness and salinity in the soil on the disposal of LFA. Present generation of huge amount of fly ash from thermal power plants (TPPs) is a big challenge concerning contamination of soil, crop produce and surface and ground water bodies due to the presence of some of the toxic trace metals in it. The leaching behavior of alkaline LFA (pH, 10.94), from TPP of Neyveli Lignite Corporation (NLC), India, was investigated by shake and column tests using water and sodium acetate buffer. The leaching of trace metals from LFA was governed by their concentrations, association with the ash particles, leaching duration and pH of the leachate (most influencing parameter). The leaching of metals followed the order: buffer column > aqueous column > aqueous shake > buffer shake test.     

An evaluation of the universal soil loss equation and field techniques for assessing soil erosion on a tropical alfisol in western Nigeria

Four techniques for soil erosion assessment were compared over two consecutive seasons for bare-fallow plots and a maize-cowpea sequence in 1985 at IITA, Ibadan, Nigeria. The techniques used were: tracer (aluminium paint), nails (16 and 25), the rill method, and the Universal Soil Loss Equation (USLE). Soil loss estimated by these techniques was compared with that determined using the runoff plot technique. There was significantly more soil loss (P < 0·01) in bare-fallow than in plots under maize (Zea mays) or cowpea (Vigna unguiculata). In the first season, soil loss from plots sown to maize was 40·2 Mg ha^?1 compared with 153·3 Mg ha^?1 from bare-fallow plots. In the second season, bare-fallow plots lost 87·5 Mg ha^?1 against 39·4 Mg ha^?1 lost from plots growing cowpea. The techniques used for assessing erosion had no influence on the magnitude of soil erosion and did not interfere with the processes of erosion. There was no significant difference (P < 0·05) between soil erosion determined by the nails and the runoff plot technique. Soil loss determined on six plots (three under maize, three bare-fallow) by the rill technique, at the end of the season, was significantly lower (P < 0·05) than that determined by the runoff plot technique. The soil loss estimated by the rill method was 143·2, 108·8 and 121·9 Mg ha^?1 for 11, 11, and 8 per cent slopes respectively, in comparison with 201·5, 162·0, and 166·4 Mg ha^?1 measured by the runoff plot method. Soil loss measured on three bare-fallow plots on 10 different dates by the rill technique was also significantly lower (P < 0·01) than that measured by the runoff plot. In the first season the USLE significantly underestimated soil loss. On 11, 11, and 8 per cent slopes, respectively, soil loss determined by the USLE was 77, 92, and 63 per cent of that measured by the runoff plot. However, in the second season there was no significant difference between soil loss determined by the USLE and that determined by the conventional runoff plot technique.     

Thermoluminescence dating of pottery from Sringaverapura—A Ramayana site

The first thermoluminescence (TL) dates of pottery from aRamayana associated site are reported. The TL dates for pre-NBPW Black-Slipped Ware levels are 730 and 765 B.C., while radiocarbon date takes the earliest Black Slipped Ware level (for which no TL dates are available) to 905 B.C. (uncorrected). For the OCW level, three TL dates are available which range from 1035 B.C. to 875 B.C. The early NBPW period believed to be associated with theRamayana episode will thus be post-750 B.C.     

Internally consistent calibrations for geothermobarometry of high-grade Mg-Al rich rocks in the system MgO-Al2O3-SiO2 and their application to sapphirine-spinel granulites of Eastern Ghats, India and Enderby Land, Antarctica

Sixty-three internally consistent geothermobarometers for mineral equilibria involving sapphirine (2:2:1 and 7:9:3), pyrope, cordierite, enstatite, Mg-tschermak orthopyroxene, quartz, spinel and sillimanite have been calibrated in the MAS system. The updated thermodynamic data of these minerals are consistent, within limits of error, with highP-T experiments on several mineral equilibria and calorimetric data. TheP-T conditions of the granulite facies metamorphism, spanning a range of 700 to more than 1000°C and 4 to more than 10 kbar, can be estimated simultaneously from these geothermobarometers andP-T-t trajectories can be deduced from the reaction coronas well preserved in these rocks because of the refractory nature of aluminous phases. The geothermobarometers have been applied to sapphirine-spinel granulites of Eastern Ghats and Enderby Land. TheP-T conditions of metamorphism (a-prograde/thermal peak and b-retrograde isothermal/isobaric decompression/cooling) estimated for these granulites are: (1) Eastern Ghats (Visakhapatnam): Paderu- (a) 900°C/8.3kbar, (b-1) 900°C/6.8kbar and (b-2) 740°C/5.4 kbar; Anantgiri- (a) prograde anticlockwise 930°C/6.2 kbar and (b) 870°C/6.8 kbar, 820°C/6.1 kbar; Anakapalle- (b) 845°C/8.5-6.2 kbar; and Araku- (b) 840°C/6.2 kbar to 795°C/5.9 kbar. Enderby Land (Napier complex): Spot height 945, Tula Mts.- (a) 970°C/9.1 ± 0.6 kbar, isobaric cooling (b) 885°C/ 7.75 kbar, isothermal decompression (b) 880°C/6.85 kbar; Mt. Hardy, Tula Mts.- (b) 885°C/6.75 kbar; Mt. Riiser-Larsen, Amundsen bay- (a) 1000°C/7.0 kbar prograde anticlockwise; Mt. Sones- (b) 920°C/ 6.8 kbar; Forefinger Point, SW Enderby Land- (b) 840°C/6.7 kbar, 810°C/6.5 kbar and 775°C/5.0 kbar. The estimatedP-T andP-T-t are mostly consistent with those inferred from the granulites of these areas.     

Modeling of the strong ground motion of 25th April 2015 Nepal earthquake using modified semi-empirical technique

On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420–515 km. Modified semi-empirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 × 10²⁵ dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model .The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE–SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results.     

Zircon and sphene as fission track geochronometer and geothermometer: A reappraisal

The data published earlier on zircon and sphene fission track ages and annealing are discussed in the light of different etching conditions used for age determination and annealing experiments in order to explain the age discordances of some zircon and sphene pairs, as well as numerous closing temperatures obtained for individual minerals. Using the new set of simple etching conditions, zircon (KOH melt) and sphene (HF+HCl), the annealing experiments indicate that tracks in sphene are annealed more easily than in zircon. The closing temperature of zircon and sphene have been calculated at 300° and 250° C respectively. The study reveals that both the fission track age and the closing temperature of a mineral can vary considerably if different etchants are used. For different etching conditions the closing temperatures (T) of sphene have the following order: ^T NaOH> ^T HF+HCl+HNO₃+H₂O> ^THF+HCl>^THCl. An alternative method can be used to obtain thermal histories of rocks by selectively applying various etchants on the same mineral.     

Comparative physical properties of weathered impregnated and unimpregnated marble

Chemical weathering of marbles has greatly increased during the past decades. The gaseous pollutants generated mainly by combustion of automobile, domestic, and industrial fuels have contributed significantly towards this increase. The weathering affects marble gradationally from outside inwards, producing three distinct zones. The success of a technique developed to provide cohesion to reduced and dislodged calcite crystals in the zone of weathering, by impregnation with resins which even permeate the inter-crystalline boundaries in the non-weathered region, is tested. As these weathered layers are quite thin and easily destructible, direct measurement of compressive strength is impossible. This property is, therefore, determined indirectly via Shore scleroscope hardness and specific gravity.

The impregnation increased the strength of the weathered zone up to 59% and of the unweathered region up to 24%. Corresponding values for permeability and capillarity, relative to untreated specimens, change inversely to strength changes as the pores receive relatively larger amounts of resin in the outer weathered region than in the unweathered region in depth. This phenomenon is substantiated by scanning electron microscopy (S.E.M.).