Evaluation of Geophysical Prospecting as an Aid to Ore Exploration in the Tri-State District
Results obtained in this investigation make it appear undesirable to do further geochemical, geothermal, or natural potential work. Further magnetic work should he only regional in character and then should be used only as guide in the interpretation of regional gravity anomalies, i. e., to determine whether such gravity anomalies are. shallow or deep-seated in character.
The indications given by the regional gravity survey that regional gravity maxima are present and are deep-seated (as indicated by coincidence with regional magnetic maxima) make it appear advisable to recommend further regional gravity investigations. The present regional gravity survey covered too small an area, regionally, to permit speculation as to the significance of such regional gravity highs. It might be possible, however, in the Mississippi Valley area, to separate potential zinc-lead producing areas from potentially nonproductive areas, by the presence or absence of deep-seated gravity maxima. Especially could this be done if it should prove possible to demonstrate that such gravity maxima indicate the presence of post-Paleozoic igneous intrusions. Such regional gravity work should be carried on in conjunction with regional magnetic work, so that it might be possible to separate shallow from deep-seated gravity anomalies. It would be advisable to drill several deep holes over that portion of the Quapaw-Hockerville area in which there is an indicated coincidence of gravity and magnetic maxima. Such drilling might reveal the causes of the observed anomalies.
Resistivity and gravity measurements can be used successfully to map structures reflected by variations in the elevation of the limestone surface. It is not possible geophysically to map structures within the limestone.
It has not been found possible, by resistivity measurements, to determine the presence of lead and zinc sulphides. It is possible, however, to use resistivity measurements in mapping certain structural and lithologic features associated at many places with ore mineralization, especially increased porosity of the limestone resulting from fracturing and brecciation. Such measurements, therefore, would permit the selection of ground which might have productive possibilities, although an area could riot definitely be classified as necessarily productive because of the presence of resistivity minima. The judicious use of resistivity methods, however, should serve greatly to minimize the amount of exploratory drilling required, by directing drilling to the most favorable prospecting areas. On the average, a saving of but one drill hole would pay for the cost of conducting detailed resistivity work over an area of 10 to 20 acres.
References
Bastin, E. S., et al., 1929, Contributions to a knowledge of the lead and zinc deposits of the Mississippi Valley region: Geol. Soc. America, Special Paper 24.
George, P. W., 1928, Experiments with the Eötvos torsion balance in the Tri-State zinc and lead district: Am. Inst. Min. and Met. Eng., Tech. Pub. 65.
Gish, H., and Rooney, W. J., 1925, Measurements of the resistivity of large volumes of undisturbed earth: Terr. Mag., vol. 30, pp. 161-188.
Grohskopf, J. G., and Reinoehl, C. O., 1933, Magnetic surveys: Missouri Bur. Mines, 57th Biennial Rep., Appendix IV, pp. 10-13.
Jakosky, J. J., 1940, Exploration Geophysics, Times-Mirror Press, Los Angeles, pp. 1-800.
Joyce, J. W., 1937, Manual on geophysical prospecting with the magnetometer: U. S. Bur. Mines. '
Pehrson, E. W., and Ransome, A. L., 1941, Zinc: U. S. Bur. Mines Minerals Yearbook, pp. 139-160.
Pehrson, E. W., and Ransome, A. L., 1941, Lead: U. S. Bur. Mines Minerals Yearbook, pp. 117-137.
Pierce, W. G., and Courtier, W. H., 1937, Geology and coal resources of the southeastern Kansas coal field: State Geol. Survey of Kansas, Bull. 24. [available online]
Weidman, Samuel, 1932, Miami-Picher zinc-lead district: Univ. Oklahoma Press, Norman.
Wenner, Frank, 1916, A method of measuring earth resistivity: U. S. Bur. Standard, Bull., vol. 12.
Kansas Geological Survey, Geology
Placed on web Oct. 29, 2018; originally published December, 1942.
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