|Geophysical surveys are mainly employed in modern uranium exploration programme for investigation of concealed uranium deposits. It is the integral part of multi-disciplinary uranium exploration programme of the organization. Geophysical techniques are particularly utilised in understanding sub surface geology, delineating subsurface structures, locating the alteration zones and the association of metallic minerals sulphides, graphite and carbonaceous phyllites having bearing on ore localization.Geophysical surveys have been effectively utilised in establishing continuity of uranium mineralization in parts of Singhbhum Shear Zone (SSZ), Jharkhand; Aravalli and Delhi fold belts Rohil-Ghateshwar and Mawata-Jahaj area, Sikar district, Rajasthan; Umra area, Udaipur district, Rajasthan; Arbail area, North Kanara district, Karnataka; and in Bhima Basin, Gulbarga district, Karnataka. The various equipments and softwares available with the Group are given below:
|Geophysical survey using CG-5 Gravity meter and GEM Magnetometer
Field equipment: Gravity meter (Sodin make) and CG-5 Autograv gravity meter (Scintrex make); Advanced total field proton precession magnetometer with GPS facility (GEM Systems); Resistivity/Induced Polarization (IP) (IRIS & IPV-8 Phoenix make); Multi-function (electrical & electromagnetic methods) transmitter-receiver system (Phoenix make); Transient Electromagnetic (TEM) (EM-37 system-Geonics and terraTEM system-Monex Geoscope); Very Low Frequency (VLF) system (Scintrex make); Slingram-horizontal loop EM system (Scintrex make); Controlled Source Audio-magnetotelluric EM system (Phoenix make); Seismic (DMT, Germany) and Multi-para-logging (Geovista, UK).
Vibsist-50 Seismic source
Ancillary instruments: Hand held Global Positioning System (GARMIN); Differential Global Positioning System (SOKKIA, Spectra Precession make); Theodolite (Nikon and Wild make), Total Station (Pentax) and Transreceivers (Motorola & ICOM make).
Laboratory equipments: Instruments to measure physical properties of rocks in the laboratory are: Magnetic Susceptibility meter (Terraplus KT-10); Conductivity meter (Terraplus KT-10) and Density meter (Walker & Steel balance, Indian make) and precision electronic balance (Precica)
In-house developed software: MAGPROS: Developed using FORTRAN for gravity and magnetic data processing; GMNIV: Inversion software for gravity and magnetic 2D data to obtain source parameters and EXPFIT: A DOS based software written in FORTRAN for interpretation of secondary IP effects.
Software purchased: GEOSOFT-Oasis Montaj, Geosoft, Canada (for gravity and magnetic data mapping and processing of gridded data and modelling of the profile data with GMSYS); RES2DINV4, Interprex, USA (for processing of 2D resistivity and IP data); EM VISION, ENCOM, Australia (for interpretation of TEM data for obtaining layered earth information); IX1D v3, USA (this software performs forward and inverse modelling in terms of layered earth with resistivity for TEM sounding method); Maxwell-EMIT, Australia (this software performs forward and inverse modelling, presentation and visualisation of TEM data) and VISTA (seismic data processing).
Five decades of Geophysical Exploration Activity in AMD: Ground Geophysical surveys:
Uranium exploration mainly relies on radiometric techniques as uranium is a radioactive mineral emitting radiation for direct detection. However, as uranium deposits occurring near the surface have more or less been discovered, presently the emphasis has shifted to deeper resources with the help of indirect geophysical techniques. During the last five decades, AMD has been actively involved in geophysical survey in geologically favourable terrains in different parts of the country for exploration of uranium. More than 3,000 sq km area has been covered so far by various types of geophysical techniques.
Chargeability and Resistivity Image of Jahaj area, Rajashtan