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We have analyzed the chemical composition and boron isotope composition of tourmaline from tourmalinites, granite and a quartz-tourmaline
vein from the Deri ore zone and from a pegmatitic band in the Rampura-Agucha ore body. These two Proterozoic massive sulfide
deposits occur in the Aravalli-Delhi orogenic belt, Rajasthan, northwest India. Tourmaline from stratiform tourmalinites closely
associated with the massive sulfides in the Deri deposit have preserved their original chemical compositions despite regional
and thermal metamorphism in the area. These tourmalines have low Fe/(Fe + Mg) ratios (0.19–0.30; mean 0.26) that suggest formation
close to the sediment-sea water interface. The δ11B values (−15.5 and −16.4‰) are compatible with boron derived from leaching of argillaceous sediments and/or felsic volcanics
underlying the original massive sulfide deposit during its formation. Boron isotope compositions measured in tourmaline from
a post-ore granite and quartz-tourmaline vein in the Deri deposit indicate that boron in these tourmalines was derived from
the tourmalinites produced during ore formation. The boron isotope systematics of a coarse brown tourmaline crystal from a
pegmatitic band on the hanging wall contact of the Rampura-Agucha deposit indicate that 45 ± 25% of the boron within the original
tourmaline was lost during upper amphibolite facies regional metamorphism.
Received: 3 April 1996 / Accepted: 11 April 1996 相似文献
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Geophysical and geomorphological approach for locating groundwater potential zones in Sukinda chromite mining area 总被引：2，自引：2，他引：0
Ratnakar Dhakate D. K. Chowdhary V. V. S. Gurunadha Rao R. K. Tiwary Amlendu Sinha 《Environmental Earth Sciences》2012,66(8):2311-2325
The impact of mining causes deterioration of environment and decline of groundwater level in the adjoining mining areas, which influences groundwater source for domestic and agriculture purposes. This necessitated locating and exploiting of new groundwater source. A fast, cost-effective and economical way of locating and exploration is to study and analyze remote sensing data. Interpreted remote sensing data were used to select sites for carrying out surface geophysical investigations. Various geomorphologic units were demarcated, and the lineaments were identified by interpretation of false color composite satellite imageries. The potential for occurrence of groundwater in the Sukinda Valley was classified as very good, good, moderate and poor by interpreting the images. Sub-surface geophysical investigations, namely vertical electrical soundings, were carried out to delineate and demarcate potential water-bearing zones. Integrated studies of interpretation of geomorphologic, lineaments and geophysical data (aquifer thickness) were used to prepare groundwater potential map. The studies reveal that the groundwater potential of shallow aquifers is due to geomorphologic features, and the potential of deeper aquifers is determined by lineaments and degree of weathering. 相似文献
4.
Alok Ranjan Tiwary Shibu K. Mathew A. Raja Bayanna P. Venkatakrishnan Rahul Yadav 《Solar physics》2017,292(4):49
The Multi-Application Solar Telescope (MAST) is a 50 cm off-axis Gregorian telescope that has recently become operational at the Udaipur Solar Observatory (USO). An imaging spectropolarimeter is being developed as one of the back-end instruments of MAST to gain a better understanding of the evolution and dynamics of solar magnetic and velocity fields. This system consists of a narrow-band filter and a polarimeter. The polarimeter includes a linear polarizer and two sets of liquid crystal variable retarders (LCVRs). The instrument is intended for simultaneous observations in the spectral lines 6173 Å and 8542 Å, which are formed in the photosphere and chromosphere, respectively. In this article, we present results from the characterization of the LCVRs for the spectral lines of interest and the response matrix of the polarimeter. We also present preliminary observations of an active region obtained using the spectropolarimeter. For verification purposes, we compare the Stokes observations of the active region obtained from the Helioseismic Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) with that of MAST observations in the spectral line 6173 Å. We find good agreement between the two observations, considering the fact that MAST observations are limited by seeing. 相似文献
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Textural identification of basaltic rock mass using image processing and neural network 总被引：3，自引：0，他引：3
Naresh Singh T. N. Singh Avyaktanand Tiwary Kripa M. Sarkar 《Computational Geosciences》2010,14(2):301-310
A new approach to identify the texture based on image processing of thin sections of different basalt rock samples is proposed
here. This methodology uses RGB or grayscale image of thin section of rock sample as an input and extracts 27 numerical parameters.
A multilayer perceptron neural network takes as input these parameters and provides, as output, the estimated class of texture
of rock. For this purpose, we have use 300 different thin sections and extract 27 parameters from each one to train the neural
network, which identifies the texture of input image according to previously defined classification. To test the methodology,
90 images (30 in each section) from different thin sections of different areas are used. This methodology has shown 92.22%
accuracy to automatically identify the textures of basaltic rock using digitized image of thin sections of 140 rock samples.
Therefore, present technique is further promising in geosciences and can be used to identify the texture of rock fast and
accurate. 相似文献
6.
Assessment and prediction of contaminant migration in ground water from chromite waste dump 总被引：3，自引：0，他引：3
Sukinda chromite valley is one of the largest chromite deposits of the country and produces nearly 8% of chromite ore. It
greatly contributes towards the economic development but at the same time deteriorates the natural environment. It is generally
excavated by opencast mining method. In the Sukinda mining area, around 7.6 million tons of solid waste have been generated
in the form of rejected minerals, overburden material/waste rock and sub-grade ore that may be resulting in environmental
degradation, mainly causing lowering in the water table vis-à-vis deterioration in surface and ground water quality. The study
conducted in and around one of the chromite mine of the valley reveals that the concentration of hexavalent chromium is found
in the water samples of ground and surface water, mine effluents and seepage water. Hexavalent Chromium (Cr+6) have been found varying between 0.02 mg/l and 0.12 mg/l in mine effluents and 0.03–0.8 mg/l in shallow hand pumps and 0.05
and 1.22 mg/l in quarry seepage. The concentration of Cr+6 in Damsal nalah, the main surface water source in the area, is found varying between 0.03 mg/l and 0.14 mg/l and a increasing
trend, which is in the downstream of mining activities, has been observed. Leachate study clearly shows that the soil lying
in the vicinity of mine waste dump shows highest concentration of Cr+6. Contaminant migration in ground water depends upon various geohydrological conditions of the area. The study shows that
aquifer resistivity varies between 15 Ωm to 150 Ωm and aquifer depth varies from 4 m to 26 m below ground level. The ground
water flow and mass transport models were constructed with the help of geo-hydrological and geophysical informations using
Visual Modflow software. Contaminant migration and path lines for 20 years have been predicted in two layers model of ground
water. The study provided an insight into the likely migration of contaminant in ground water due to leaching from overburden
dump of chromite ore and will be helpful in making strategic planning for limiting the contaminant migration in the ground
water regime in and around the mining areas. 相似文献
7.
Dawn A. Zemo Kirk T. O'Reilly Rachel E. Mohler Asheesh K. Tiwary Renae I. Magaw Karen A. Synowiec 《Ground Water Monitoring & Remediation》2013,33(4):44-56
Polar metabolites resulting from petroleum biodegradation are measured in groundwater samples as TPHd unless a silica gel cleanup (SGC) is used on the sample extract to isolate hydrocarbons. Even though the metabolites can be the vast majority of the dissolved organics present in groundwater, SGC has been inconsistently applied because of regulatory concern about the nature and toxicity of the metabolites. A two‐step approach was used to identify polar compounds that were measured as TPHd in groundwater extracts at five sites with biodegrading fuel sources. First, gas chromatography with mass spectrometry (GC‐MS) was used to identify and quantify 57 individual target polar metabolites. Only one of these compounds—dodecanoic acid, which has low potential human toxicity—was detected. Second, nontargeted analysis was used to identify as many polar metabolites as possible using both GC‐MS and GC×GC‐MS. The nontargeted analysis revealed that the mixture of polar metabolites identified in groundwater source areas at these five sites is composed of approximately equal average percentages of organic acids, alcohols and ketones, with few phenols and aldehydes. The mixture identified in downgradient areas at these five sites is dominated by acids, with fewer alcohols, far fewer ketones, and very few aldehydes and phenols. A ranking system consistent with systems used by USEPA and the United Nations was developed for evaluating the potential chronic oral toxicity to humans of the different classes of identified polar metabolites. The vast majority of the identified polar metabolites have a “Low” toxicity profile, and the mixture of identified polar metabolites present in groundwater extracts at these five sites is unlikely to present a significant risk to human health. 相似文献
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Shibu K. Mathew Ankala Raja Bayanna Alok Ranjan Tiwary Ramya Bireddy Parameswaran Venkatakrishnan 《Solar physics》2017,292(8):106
The Multi-Application Solar Telescope is a 50 cm off-axis Gregorian telescope recently installed at the Udaipur Solar Observatory, India. In order to obtain near-simultaneous observations at photospheric and chromospheric heights, an imager optimized for two or more wavelengths is being integrated with the telescope. Two voltage-tuneable lithium-niobate Fabry–Perot etalons along with a set of interference blocking filters have been used for developing the imager. Both of the etalons are used in tandem for photospheric observations in Fe i 6173 Å and chromospheric observation in H\(\alpha\) 6563 Å spectral lines, whereas only one of the etalons is used for the chromospheric Ca II line at 8542 Å. The imager is also being used for spectropolarimetric observations. We discuss the characterization of the etalons at the above wavelengths, detail the integration of the imager with the telescope, and present a few sets of observations taken with the imager set-up. 相似文献
9.
Inversion codes are the most useful tools to infer the physical properties of the solar atmosphere from the interpretation of Stokes profiles. In this paper, we present the details of a new Stokes Profile INversion code (SPIN) developed specifically to invert the spectro-polarimetric data of the Multi-Application Solar Telescope (MAST) at Udaipur Solar Observatory. The SPIN code has adopted Milne–Eddington approximations to solve the polarized radiative transfer equation (RTE) and for the purpose of fitting a modified Levenberg–Marquardt algorithm has been employed. We describe the details and utilization of the SPIN code to invert the spectro-polarimetric data. We also present the details of tests performed to validate the inversion code by comparing the results from the other widely used inversion codes (VFISV and SIR). The inverted results of the SPIN code after its application to Hinode/SP data have been compared with the inverted results from other inversion codes. 相似文献
10.
T. B. Pradeep Kumar Akhileshwar Tiwary Sohail Fahmi 《Journal of the Geological Society of India》2009,73(2):220-228
Mineralisation of uraninite and brannerite occurs in the albitised metasedimentary and intrusive igneous rocks of Kerpura-Tiwari-ka-bas
area in Sikar district, Rajasthan. Samples collected from well dumps contain 0.016 to 1.52% U3O8 with very low ThO2. The host rocks show wide variation in chemical composition due to varying degree of alkali metasomatism, associated alteration
and composition of protoliths. The spatial distribution of uranium in groundwater as well as rock samples from well dumps
indicates localisation of the uranium mineralisation along NNE-SSW and NWSE directions in Kerpura block. Petrographic and
lithogeochemical studies point towards close genetic relationship between alkali metasomatism and uranium mineralisation.
The mineralisation seems to be due to mobilisation of uranium and other LILEs by metasomatising fluids and their deposition
along shear zones at a later stage, which may not be spatially related to zones of intense albitisation. 相似文献
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