Geophysical exploration techniques for metals

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  • Geophysical exploration techniques for metals
    • Gravity surveys
      • Gravimeters mounted on planes, helicopters or land vehicles for regional surveys
      • Positive gravity anomaly
        • High density mafic / ultramafic intrusion maybe containing ore deposits
        • Presence of dense, metallic ore minerals
      • Negative gravity anomaly
        • Low density silicic intrusion, maybe with hydrothermal mineral veins around it
    • Magnetic surveys
      • Can be done airbourne for regional surveys and land-based for detailed surveys
      • Two types of survey
        • Transect survey, measures along a straight line
        • Map survey, values plotted on a map, lines plotted by equal magnetic field strength
      • Minerals rich in iron produce positive anomalies
        • Maybe due to a mafic / ultramafic intrusion, possibly containing ore deposits from gravity settling
        • Presence of magnetite
    • Electrical resistivity survey
      • Two electrodes placed in the ground and an electric current is passed between them
      • If the rock is a good conductor it will have a low resistance
      • This method is used for gold exploration


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