CONTENTS OF OCTOBER 2013, Vol.XXXIV   No.4

 

Gravity Modelling of Mahanadi Basin with Special Reference to Hydrocarbon Exploration.

Vasanthi and K. Mallick

 

An Integrated Geophysical Approach for Uranium Exploration in Parts of North Delhi Fold Belt - A Case Study from Guman Singh Ki Dhani - Narsinghpuri Area, Sikar District, Rajasthan.

Subhash Ram, B.Shankaraiah, R.Srinivas, J.K Dash, L. K. Nanda and A. K Chaturvedi

 

Integrated Geoscientific studies for Naturally Occurring Fullerene in the Pullampeta Shales, Mangampeta Baryte Field,Cuddapah Basin, India.

Y. Sreedhar Murthy, S.V.S.Sarma and S. Neelakantam

 

Geophysical Prospecting for Exploration of Gold, PGE and Ferrous Metals in the South-Eastern Fringe of Singhbhum Craton, Keonjar District, Orissa.

Bidhan Sarkar, Debangshu Banerjee, K.N.Prasad, Dinesh Gupta

 

Application of Geophysical Methods as an Aid to Shear Controlled Uranium Mineralization along Pakni-Asnapara-Darhaura Tract,Surguja District, Chhattisgarh.

M. Narsimha Chary, Viney Kumar, B. Shankaraiah and J.K. Dash

 

 

 

Gravity Modelling of Mahanadi Basin with Special Reference to Hydrocarbon Exploration

Vasanthi and K. Mallick
CSIR-National Geophysical Research Institute, Hyderabad

 

Abstract

   The Cauvery, Krishna-Godavari (K-G), Mahanadi and Bengal Basins are four major basins on the east coast of India. Of these four, Cauvery and K-G Basins have both on-land and off-shore hydrocarbon deposits. As regards Mahanadi Basin, it has rich coal deposits, but continued efforts by Oil India Ltd to find hydrocarbon in the deltaic region in the depth ranges upto 3000 m have not been fruitful. However, a recent discovery of an offshore gas field 50 km from the mouth of the river Mahanadi has revived the interest among the petroleum geologists and geophysicists. This gas find has motivated us to reinterpret the Bouguer gravity anomalies. The new depth estimates for the sediment thickness by modeling the residual gravity anomaly show it to be much more than earlier calculations, thereby the prospects of the hydrocarbon deposits appear brighter. The deepest region corresponding to the Cuttack gravity low is of the order of 5150 m in contrast to ~3000 m inferred by an earlier study by deep seismic sounding (DSS).

 

 

 

An Integrated Geophysical Approach for Uranium Exploration in Parts of North Delhi Fold Belt – A Case Study from Guman Singh Ki Dhani – Narsinghpuri Area, Sikar District, Rajasthan

 

Subhash Ram*, B.Shankaraiah*, R.Srinivas***, J.K Dash*,
L. K. Nanda** and A. K Chaturvedi***


Atomic Minerals Directorate for Exploration and Research,
Department of Atomic Energy
*Nagpur-440 001, **Jaipur-302 027 and ***Hyderabad - 500 016
E-mail: subhashramgeo@gmail.com

 


Abstract

   Detailed geophysical surveys employing Gravity, Magnetic and Induced polarization (IP) methods was adopted for the exploration of uranium in the soil covered region of Guman Singh ki Dhani – Narsinghpuri area to trace the north-eastern extension of the mineralised zone established earlier in Kerpura-Salwari area, Sikar district, Rajasthan. The study area falls in the southern part of the Khetri sub-basin which forms a part of Delhi Supergroup of Meso-Proterozoic age. Here, the uranium mineralization is essentially fracture controlled, occurs in sheared and brecciated rocks along the axial plane of a NE-SW trending plunging fold of Ajabgarh Group.

 

   Qualitative analysis of both gravity and magnetic data acquired over an area of 6 sq km revealed three well-defined zones (zone-I, zone-II and zone-III) attributed to lithological variations with distinct contrast in physical property. Application of signal enhancement techniques including upward continuation, derivatives and RTP provides valuable information about the nature of anomalies both at shallow and deeper levels of the sub-surface. The tilt derivative method in particular when applied to gravity data brought out clearly an arcuate-shaped gravity low most likely a fracture zone supplemented by low order resistivity. This fracture zone is bounded by two faults as inferred from the upward continued RTP map. Moderate chargeability recorded over zone-III indicates massive sulphide dissemination/graphite and low resistivity inferred to be the most favourable locale for uranium mineralization. Subsequent bore holes drilled in the based on the interpreted geophysical results have intercepted significant bands of uranium in the study.

 

 

 

Integrated Geoscientific studies for Naturally Occurring Fullerene in the Pullampeta Shales, Mangampeta Baryte Field,Cuddapah Basin, India.

 

Y. Sreedhar Murthy*, S.V.S.Sarma** and S. Neelakantam***
*Professor of Geophysics (Retd.), Osmania University, Hyderabad
**Scientist (Retd.), National Geophysical Research Institute, Hyderabad
*** Dy. Director General (Retd.),Geological Survey of India, Hyderabad

 

Abstract

   Under an integrated geoscientific programme for fullerenes, systematic rock sampling as well as geophysical studies have been carried out in the Mangampeta barytes mine area of Cuddapah basin A.P. A total of 1050 rock samples were collected from the mine sections at different depth levels and also from the mine dumps. The rock samples were subjected to analysis using different analytical methods like Mass Spectrometry, X-Ray diffraction, High Pressure Liquid Chromotography (HPLC), at different laboratories in U.S and India. The results of analysis clearly pointed out to the presence of fullerene in all the rock samples indicating a wide spread occurrence of fullerene in tuffs of Mangampeta barytes mine. Geophysical measurements using electrical and induced polarization methods were also carried out in the fullerene occurrence area for the purpose of subsurface imaging. A well defined NW-SE trending linear zone of high electrical conductivity and polarizability cutting across the mine area is delineated. This is interpreted to be representing a deep fracture zone presumably related to the volcanic activity believed to be responsible for the localization of barytes.

 

   It is suggested that the volcanic activity, supposed to have been responsible for the origin of barytes, played a significant role in creating suitable thermal conditions and environment conducive to transformation of the existing hydrocarbon material in the black shales/tuffs into higher order allotropes of carbon representing the family of fullerenes.


 

 

Geophysical Prospecting for Exploration of Gold, PGE and Ferrous Metals in the South-Eastern Fringe of Singhbhum Craton, Keonjar District, Orissa.

 

Bidhan Sarkar, Debangshu Banerjee*, K.N.Prasad**,
Dinesh Gupta

Geological Survey of India, SRO, Bandlaguda, Hyderabad-500068
* GSI, M & CSD, **GSI, ERO, Salt Lake, Kolkata

 

Abstract

   Geophysical exploration was carried out by employing Gravity-Magnetic (GM) and Resistivity- cum- IP survey in the area bounded by (Lat. 21° 04/ to 21° 08/ N; and Long. 86° 00/ to 86° 08/ E) in the Keonjhar district of Orissa falling in parts of toposheet No. 73K/4 for the prospecting of Gold, Platinum Group of Elements (PGE) and Ferrous metals. The results of the above survey are presented in this paper.

 

   The GM survey has very clearly brought out the subsurface geology of the area in general and disposition of the high density ultramafic body in particular which are concealed under lateritic cover. The survey further has identified several structural features including faults which have significant implications as far as mineralization is concerned. Some of these geophysical lineaments/faults bear good correlation with lineaments interpreted from land sat imagery. Anomalous values for gold, platinum (Pt), palladium (Pd) have been recorded from geochemical sample collected near the intersection of such lineaments.

 

   The Resistivity- cum- IP anomalies were also successful in demarcating the area over the concealed ultramafic bodies which is significant from the sulphide mineralization point of view at depth. Subsequently, boreholes drilled over such anomaly zones intersected ultramafic bodies wherein enclaves of meta-chert with minor sulphides were intersected, below which rock showed evidence of major shearing. Based on the results of geochemical analysis association of gold and PGE has been established. Therefore, results of these geophysical surveys have played an important role in assessing the area for gold, PGE and ferrous metals.


 

 

Application of Geophysical Methods as an Aid to Shear Controlled Uranium Mineralization along Pakni-Asnapara-Darhaura Tract,Surguja District, Chhattisgarh

 

M. Narsimha Chary, Viney Kumar, B. Shankaraiah and J.K. Dash
Atomic Minerals Directorate for Exploration and Research,Department of Atomic Energy, Nagpur-440001
E-mail: vijay.sankoju@gmail.com

 

Abstract

 

   Geophysical methods have been extensively used for delineation of structural features such as shear zones, faults and fractures which often control and host economic mineralization. Multiple parallel and sub-parallel shear zones hosting vein type uranium mineralization occur in Surguja shear zone comprising basement gneissic complex as inliers in Gondwana sedimentary rocks. The geophysical signatures of one such shear zone near Pakni-Asnapara-Darhoura are investigated employing magnetic and induced polarization methods. Interpretation of magnetic data has revealed a broad ‘magnetic low’ trending in ENE-WSW direction and is attributed to intense shearing and fracturing in the host rock. Within this low zone, basic bodies responsible for remobilization of uranium due to the high geothermal gradient are identified. Disposition of these basic bodies has indicated the presence of NNW-SSE trending faults and continues towards north. Induced polarization data have indicated that the mineralized zones which are characterized by high chargeability and low resistivity anomalies follows the trend of the shear zone.


 

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