- 行业: Mining
- Number of terms: 33118
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- Company Profile:
The U.S. Bureau of Mines (USBM) was the primary United States Government agency conducting scientific research and disseminating information on the extraction, processing, use, and conservation of mineral resources.
Founded on May 16, 1910, through the Organic Act (Public Law 179), USBM's missions ...
A geophysical device for measuring or recording variations in terrestrial magnetism; a variable inductance provided with a scale.
Industry:Mining
A geophysical instrument similar to the gravimeter in that absolute values are not measured, but only the differences in vertical magnetic force between field stations and a selected base station.
Industry:Mining
A geophysical measuring device such as a magnetometer, plus the housing in which it is towed behind an aircraft.
Industry:Mining
A geophysical method employing the generation of electromagnetic waves at the Earth's surface; when the waves penetrate the Earth and impinge on a conducting formation or orebody, they induce currents in the conductors, which are the source of new waves radiated from the conductors and detected by instruments at the surface.
Industry:Mining
A geophysical prospecting instrument that is used to determine distortions in the gravitational field. It consists of a pair of masses suspended by a sensitive torsion fiber and so supported that they are displaced both horizontally and vertically from each other. A measurement is made of the rotation of the suspended system about the fiber; the rotation is caused by slight differences in the gravitational attraction on the two masses.
Industry:Mining
A geophysical prospecting instrument that is used to determine distortions in the gravitational field. It consists of a pair of masses suspended by a sensitive torsion fiber and so supported that they are displaced both horizontally and vertically from each other. A measurement is made of the rotation of the suspended system about the fiber; the rotation is caused by slight differences in the gravitational attraction on the two masses.
Industry:Mining
A geophysical prospecting method based on the fact that the speeds of transmission of shock waves through the Earth vary with the elastic constants and the densities of the rocks through which the waves pass. A seismic wave is initiated by firing an explosive 2820 charge (or by equivalent artificial sources) at a known point (the shot point); records are made of the travel times taken for selected seismic waves to arrive at sensitive recorders (geophones). There are two main subdivisions of seismic operations: the reflection method and the refraction method. The seismic method has been applied to a lesser extent to elucidate mining problems, partly due to its high cost. It has been used to investigate the base of drift deposits, and drift-filled channels have been successfully outlined.
Industry:Mining
A geophysical prospecting method that depends on the electrical or electrochemical properties of rocks. The resistivity, spontaneous-polarization, induced-polarization, and inductive-electromagnetic methods are the principal electrical methods.
Industry:Mining
A geophysical prospecting method that maps variations in the magnetic field of the Earth that are attributable to changes of structure or magnetic susceptibility in certain nearsurface rocks. Sedimentary rocks generally have a very small susceptibility compared with igneous or metamorphic rocks, and most magnetic surveys are designed to map structure on or within the basement, or to detect magnetic minerals directly. Most magnetic prospecting is now carried on with airborne instruments.
Industry:Mining
A geophysical prospecting method that measures irregularities or anomalies in gravity attraction produced by differences in the densities of rock formations, and interprets the results in terms of lithology and structure.
Industry:Mining
