P. S. Millegan, 1998. "General Philosophy 6: A Different Approach (Mining and Environmental)", Geologic Applications of Gravity and Magnetics: Case Histories, Richard I. Gibson, Patrick S. Millegan
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Although gravity and magnetic surveys for hydrocarbon exploration typically are designed with relatively wide data spacings, to define relatively deep-seated features, environmental and mining projects are concerned with information from much nearer the surface. One of the biggest differences in these two kinds of surveys is, therefore, line or data spacing, which is much closer for shallow-target work. Ground magnetometry commonly is used instead of airborne magnetics, so that the sensor can be closer to the small target anomalies.
Magnetic data still find their greatest application in mapping buried metallic objects such as waste drums, but excellent magnetic surveys have been used archaeologically to define tepee rings, hearths, and other structures. Similar approaches may contribute to understanding soil and channel distribution in aquifers and other environmentally interesting situations. An important use has been finding abandoned steel-cased well bores, which have serious impact on subsurface fluid flow. Gravity data can help locate buried void spaces and can assist in the delineation of subsurface features such as channels. A high-tech superconducting gravity meter can discern between a “filled” aquifer and a mostly empty one.
Mining studies are concerned with mineral distributions, and their distinctive gravity and magnetic signatures can assist with such interpretation. Traditionally, mining applications (especially using magnetics) have ranged from frontier exploration to ore-body delineation. Tectonic studies also bear on miningexploration problems, and for diamond exploration, kimberlite pipes are often almost directly detectable by their characteristic