July, 2019 || Volume 23 No.4
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Estimating subsurface petro-physical properties from raw and conditioned seismic reflection data: A comparative studyPrabodh Kumar Kushwaha1*, S.P. Maurya2, N.P. Singh2 and Piyush Rai1
1Department of Mining Engineering, Indian Institute of Technology (BHU), Varanasi-221005, India
2Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi-221005, India
*Corresponding author: prabodhkk.rs.min15@itbhu.ac.inABSTRACT
The data conditioning plays an important role in simultaneous seismic inversion process as in some cases, it improves the resolution of the inverted results, while in other cases, it degrades the solution dramatically. Therefore, it needs to be studied carefully. The objective of the present study is to quantify the advantages of performing pre-stack data conditioning, prior to estimation of subsurface petro-physical parameters. In present study, a very simple and straight forward method of testing the effects of data conditioning on simultaneous inversion, have been chosen and inversion is performed over the original processed gathers, as well as the conditioned gathers to measure the difference in intermediate steps of the workflow. In this regard, initially, one trace is inverted and compared with original curve from well log to test the algorithm. The correlation between the two is estimated to be 0.82 for raw gather and 0.87 for conditioned gather. Further, the entire seismic volume is inverted for impedance, density and lamé parameters in inter well region, thereafter, and the cross plots between inverted section are computed. The results of the analysis indicate that the reservoir is devoid of hydrocarbon. The analysis depict that the inversion of conditioned data produces a result, which is of more valuable to an interpreter as compared to the inversion of raw gather.
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Efficacy of the gravity and magnetic methods in mapping the subsurface features in the NE part of Madhya Pradesh (India)R. Kumar* and A.K. Singh
Geological Survey of India, Central Region, Nagpur-440006, Maharashtra, India
*Corresponding author: rajan.08.ism@gmail.comABSTRACT
This study brings out the efficacy of the gravity and magnetic methods in delineating the subsurface features, such as fault/ tectonic contact and basin boundaries in parts of Singrauli and Sidhi districts of Madhya Pradesh (India). The Bouguer gravity and magnetic anomaly map, which was subjected to several filtering and processing techniques, clearly reflected the inferred structural features, which in turn correlate well with the geological features trending in E-W and NE-SW direction. Magnetic anomaly of higher amplitudes in the northwestern part, coincides with the presence of metabasalt, biotite schist and BIF, whereas in the northeastern part, it is due to the concentration of the magnetite grains in biotite schist and phyllite. The regional gravity low observed in central, northeastern and southwestern parts of the area is ascribed to sedimentary rocks belonging Gondwana formation. The residual gravity map shows several local gravity anomalies with amplitude and direction. Similarly, the residual magnetic anomalies reveal various shapes with the direction of extensions and orientations. The inferred boundary/ contact zone (F1-F1' and F3-F3' like Amsi-Jiawan (F5- and Jamui-Markundi (F6- , are clearly brought out in the Total Horizontal Derivative (THDR ) and Tilt derivative (TDR) maps of gravity data. The THDR of the magnetic data shows magnetic maxima over the Mahakoshal formation and also at various scattered locations in the northeastern and central parts of the map. The TDR of the magnetic data depicts anomalies close to zero magnetic values that coincide with edges or boundaries of the inferred faults like Amsi-Jiawan (F5- and Jamui-Markundi (F6- . The majority of Euler solutions fall at the contact between two litho-units faults/ contacts, with varying depth of 0.5 to 2.5km
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The growth of magnetization minerals with a rise in temperature
Victor V. Onufrienok
Krasnoyarsk Agrarian University, E. Stasova Street, 44. Krasnoyarsk, Russian Federation
VOnufriynok@yandex.ru
ABSTRACT
Magnetic properties of iron sulfides in a metastable phase state were investigated. During heating of iron sulfides of the composition Fe0.901S up to ~150°C, a magnetization increase was observed. It was shown that the observed effect is not the - transition and that it results from the redistribution of vacancies of iron ions in basal planes of the crystal structure of the NiAs type. A theoretical model was proposed which explains qualitatively this effect.
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Multivariate Statistical Approach for Evaluating Groundwater Quality in Sathyavedu Area, Chittoor District (Andhra Pradesh, India)G. Veeraswamy1*, E. Balaji1, A. Nagaraju1, and Brijesh Kumar Yadav2
1Department of Geology, Sri Venkateswara University, Tirupati, Andhra Pradesh,
2Department of Hydrology, IIT Roorkee, Roorkee 247667 (Uttarakhand),
*Corresponding author: veeraswamygolla33@gmail.com
ABSTRACT
The aim of the present study is to identify the geochemical processes and source of contaminants in Sathyavedu area using statistical methods such as factor analysis (both Q and R-modes) and hierarchical cluster analysis. A total of 39 groundwater samples were collected and analyzed for various physicochemical parameters. R-mode analysis refers to the correlation between the variables whereas; Qmode refers to the linkage between the numbers of samples. Factor analysis has given nine factors and among all, the first five factors, was considered as they explain the possible sources of variance in the data sets, which were mainly attributed to the weathering process, rock-water interaction and the dissolution of sulphates and chlorides due to fertilizers and agricultural activities. Whereas, cluster analysis in R-Mode has 5 classes which are attributed to silicate weathering, overall impact of rock-water interaction and dissolution of chlorides and sulphates. The Gibb's diagram shows that all the samples fall in the rock-water interaction area. Hydrochemical facies (piper) indicates that about 90% of the samples belong to mixed CaMg-Cl and the remaining 10% belongs to in Ca-Cl facies type. The normalized bivariate plot shows that the groundwater is influenced by the silicate weathering processes
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Petrogenesis of A-type granite plutons of Gilkapadu and Ramreddipalem, area, Nellore Schist Belt, Eastern Dharwar Craton, IndiaTushar M. Meshram1*, Rajani Dharme2, Sumit K. Mitra3 and V.V. Sesha Sai2
1Petrology Division, Geological Survey of India, Central Region, Nagpur-440006 India
2 Geological Survey of India, Maharashtra, Central Region, Nagpur-440006 India
3 Director (Rtd.), Geological Survey of India, Southern Region, Hyderabad-India
*Corresponding author: tusharmeshram1984@gmail.comABSTRACT
We present the field, petrographic and geochemical characters of two thorite bearing A-type granite plutons that occur as detached bodies around Gilkapadu and Ramreddipalem (GR) in the southern part of the Neoarchean Nellore Schist Belt (NSB) of Eastern Dharwar Craton (India). These granites are oval to sub-oval in shape, leucocratic to mesocratic in nature and deformed along the margins. Interestingly, both the granites are thorite bearing and are outcropped along NE-SW trend and exhibit discordant relationship with the host Mesoproterozoic Rapur granite exposed SE of Ramreddipalem.
Petrographically, the GR granite consists essentially of K-feldspar, quartz and plagioclase with minor biotite. Zircon, epidote, apatite, titanite, monazite and opaques, constitute the accessory minerals. Textural studies indicate the presence of quartz-alkali feldspar intergrowths and micrographic textures. Mineral chemistry by EPMA studies helped in concluding the presence of uraninite and thorite. Major oxide analysis, indicate an average high SiO2 (70.83 wt %) and Na2O+K2O content (8.42 wt %) and low CaO (1.46 wt %) and MgO (0.74 wt %). Relative enrichment of Ba (430-1499 ppm), Zr (118-541 ppm) Y (25-150 ppm) and HREE is observed as compare to Sr content (19 ppm to 119 ppm). LREEs are relatively enriched when compared to HREE and has negative Eu anomaly. In Zr+Nb+Ce+Y vs major oxide and 10000 Al*Ga/Al vs trace element plots, the samples fall in A-type field, while in the trace element tectonic discrimination diagram, these granite exhibit within-plate granite (WPG) characters. In contrast to this, the granite plots in A2-type field of Y-Nb-Ce diagram, which is an indication that it is derived by differentiation of a continental tholeiite, with variable degrees of crustal interaction, or by direct melting of a crustal source.
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Long term (1984-2013) winter temperature variability and cold wave analysis over Varanasi CityPriyanshu Gupta1, Sunita Verma1*, R. Bhatla2, Swagata Payra3, and Pramod Kumar Yadava1
1Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi-221005, Uttar Pradesh, India.
2Depatment of Geophysics, Banaras Hindu University, Varanasi-221005, Uttar Pradesh, India.
3Department of Physics, Birla Institute of Technology Mesra, Jaipur Campus, Jaipur-302017, Rajasthan, India
*Corresponding author: verma.sunita@gmail.comABSTRACT
Cold wave frequency (CWF), minimum temperature trend and their anomalies for the winter season (December-February) over Varanasi (India), have been studied for the period 1984-2013. Conventional and robust statistical methods have been applied to analyze the winter temperature trends. The maximum and minimum value of mean minimum temperature ranges from 8.39C/year and 11.26C/year in 1997 and 2009 respectively. Minimum temperature anomalies in winter season show 15 warmer and 15 colder conditions for the study period. The result indicates a systematic decrease in cold wave percentage from earlier (1984-1993) to last two decades (1994-2003 and 2004 to 2013) 52.1%, 26.1%, and 21.7%, respectively. The temperature analysis depicts that over Varanasi, average minimum temperature shows increasing trends with a change of + 0.039 during 30 years period. The cold waves are however marked by decreasing trend with 58.3% frequency change from earlier to recent decade and have become less frequent which may be due to the rapid growth of urbanization, industrialization and heavy pollution loads. But in contrary, a special occasion happened on 8th and 9th January 2013, which shows a long lasting with stronger intensity severe cold wave compared to last 30 years, which may be due to long spelled strong western disturbance. The cumulative wind speed and wind direction analysis shows that wind blows most commonly from the western side with an average wind speed of 1.98 knots for the period 1991 to 2013 over Varanasi
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Accuracy assessment of land use/land cover classification in parts of Kadapa district (Andhra Pradesh, India), using remote sensing and GISM. Rajasekhar, G. Sudarsana Raju*, R. Siddi Raju, M. Ramachandra and B. Pradeep Kumar
Dept. of Geology, Yogi Vemana University, Kadapa, Andhra Pradesh, India-516005.
*Corresponding author: gsraju05@gmail.comABSTRACT
This study assesses land use/land cover (LULC) with Accuracy Assessment (AA) in Chennur mandal of the Kadapa district (Andhra Pradesh), using satellite images and socio-economic data. Spatial and temporal elements of LULC were measured using Landsat 8 OLI/TIS images, following a supervised classification algorithm technique in ERDAS Imagine software. Accuracy of the Landsat-derived LULC maps are about 84%. The study indicated that considerable evolution of built-up areas and barren/waste lands in the study area of the Kadapa district resulted in significant decrease in the area of water bodies, agricultural land and the forest cover. The built-up land growth has been large due to rising population growth. Fast urban development through infilling of low-lying zones and clearing of forest regions affected the environment, as well as its economic development. The major LULC groups include agricultural land (55.28%), water bodies (5.45%), and built-up land (6.65%), forest (2.61%) and wastelands (30.01%). The present study can be used by decision makers to develop economically sustainable plan for the protection of environment
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Petrography of the quartz feldspar porphyry dyke from Patagundemgollapalle (Kadiri Mandal, Anantapur District), Andhra Pradesh, IndiaR. Maheswara rao, S. Srinivasa Gowd*, and G. Harish Vijay
Department of Geology, Yogi Vemana University, YSR Kadapa-516006, Andhra Pradesh
*Corresponding author: ssgowd@gmail.comABSTRACT
Quartz Feldspar Porphyry (QFP) occurs as a dyke body intruding into the granitoid country, located near Namala Gudi temple, on the way to Kadiri from Pulivendula. It runs for about 6-8 km in the NNE-SSW direction. It has phenocrysts of quartz and feldspars in a fine grained matrix of the same material. Due to the higher incidence of K-feldspar, the rock has more pink color. At Namalagudi area, this shows extensive brittle deformation. All along the strike, the features remain same, but not the brittle deformation. The quartz appears to have two populations, viz., phenocrysts the average size is 5 mm (maximum 7 mm) with the ground mass containing grains of less than 0.1mm. The larger grains appear to have nucleation for the growth of the crystal and commonly contain melt inclusions and secondary fluid inclusions