Exploration Geophysics

Abstract

Geophysics is a science that studies the structure and dynamics of the Earth by making measurements of its gravitational, magnetic, electrical and electromagnetic fields, radioactivity and the passage of elastic waves. It studies phenomena such as earthquakes and volcanoes, the movement of continents, and the formation of mountains and ocean basins. Geophysical measurements are used to determine the distribution of various physical properties within the Earth, such as bulk density, magnetization, magnetic susceptibility, electrical conductivity and elastic moduli. In turn, these properties are used to deduce the distribution of different types of rocks and minerals within the Earth, and information about their state, for example their temperature, strength or fluid content. Exploration geophysics applies geophysical methods to search systematically for valuable resources contained in the Earth's crust such as precious and base metals, industrial minerals, and coal, oil, and gas. This article reviews the principles of the main geophysical methods, and the acquisition, processing and interpretation of data. The application of geophysics to various phases of exploration is illustrated by three case studies—first, the use of teleseismics and magnetotellurics to identify regions that could host diamondiferous kimberlite pipes; second, the use of aeromagnetic surveys to find stratiform copper-silver deposits buried beneath desert sands; and third, the use of reflection seismics to image the geological structure of a layered igneous complex containing chromite and platinum group elements ores.