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Introduction
Purpose of the Investigation
Early in 1941 the University of Kansas Engineering Experiment Station and the State Geological Survey of Kansas were invited, by several governmental agencies, to investigate the feasibility of using geophysical methods as a guide to ore prospecting in the Tri-State zinc and lead mining district of Kansas, Oklahoma, and Missouri. The increased demand for zinc and lead in the production of war materials made it appear desirable to attempt to develop some geophysical method or combination of methods which would, be more rapid and less expensive than the present method of exploration by churn drilling now commonly employed in the Tri-State district.
Arrangements were completed between the State Geological Survey and the University Engineering Experiment Station. These organizations then approached the Tri-State Zinc and Lead Ore Producers' Association to ascertain whether the operators in the district thought it advisable to investigate the potentialities of geophysical prospecting in that area. The project was looked upon with such favor by the Ore Producers' Association that the Association offered to underwrite half the cost of the project. A subsequent grant was obtained from the Kansas Industrial Development Commission for the spectrographic analysis.
The purpose of the geophysical investigation, therefore, was to determine some geophysical technique or combination of techniques which could be utilized for ore prospecting in the Tri-State district. In order to simplify the initial experimental work all of the geophysical investigations were made over areas where, as the result of intensive drilling, the geologic conditions and mode of ore occurrence were already known. In each area there was an attempt to correlate the various geophysical anomalies with known geologic conditions. No attempt was made to prospect areas which had not been explored by drilling.
During the course of the investigation, the following types of geophysical surveys were conducted: electrical resistivity, geothermal, geochemical, gravity, natural earth potential, and magnetic. Seismic work was contemplated, originally, as a part of the project. The difficulty and expense of applying seismic methods to these areas, however, as compared with the results that theoretically might be expected, made it appear advisable to defer this work until a later date.
Acknowledgments
Few geophysical projects can be successful without the full cooperation of the ore producers and operators. From the beginning of the project, all of the producers and operators in the Tri-State district gave most generously of their advice and assistance; and to their help is due, in no small measure, the relatively rapid completion of the project. Mr. Evan Just, Secretary of the Tri-State Zinc and Lead Ore Producers' Association, helped the writers continuously throughout the duration of the project. Mr. George M. Fowler gave the writers ready access to the tremendous fund of geologic data which he has developed during his many years of geologic study in the Tri-State district.
It would be impossible to mention separately each of the companies and their engineers who have freely given their advice and use of their established facilities. The Eagle-Picher Mining and Smelting Company gave assistance on numerous occasions; for this assistance, the writers wish to thank Mr. George W. Potter, Mr. D. C. MacKallor, Mr. R. K. Stroup, and Mr. E. W. McMullen. Thanks are also due to Federal Mining and Smelting Company—especially to Mr. Chester Scott, Mr. L. G. Johnson, and Mr. I. V. Korts. The help of Mr. John Inman and Mr. W. F. Netzeband of the American Zinc, Lead, and Smelting Company is likewise acknowledged.
We wish to acknowledge the courtesy of International Geophysics, Inc., of Los Angeles, in releasing for work on this project their past Chief Engineer, Mr. C. H. Wilson.
The gravity surveys published as a part of this report were conducted by the Mott-Smith Corporation, Houston, Texas. The kindness of the Mott-Smith Corporation in running the gravity work on a research basis is greatly appreciated. In this connection, we wish to thank Mr. E. V. McCollum, of the Mott-Smith Corporation, who arranged for his company to do this work. We also take pleasure in acknowledging the help of Mr. Julian Hawes, who ably supervised the gravity field work for the Mott-Smith Corporation.
The spectroscopic analyses were made in the Department of Physics, Kansas State College, by permission of President F. D. Farrell and Dr. A. B. Cardwell, Chairman of the Department of Physics. This work was done under the able supervision of Professor J. Howard McMillen, the Department of Physics, Kansas State College. An industrial fellowship of the University of Kansas, which was awarded by the Kansas Industrial Development Commission to Mr. Maurice Wallace, gave financial assistance for spectroscopic studies.
We wish especially to acknowledge the able assistance of the technical crew, including Mr. Maurice Wallace, assisting with geologic studies and with the geochemical and geothermal surveys; Mr. Arthur Bowsher, assisting with resistivity and natural potential surveys; and Mr. Stuart Bunn, surveyor.
Previous Geophysical Investigations in the Tri-State Area
All previous geophysical investigations in the Tri-State-area have been either of very short duration or regional rather than detailed in character.
The Missouri Bureau of Mines and Geology (cf. Grohskopf and Reinoehl, 1933, pp. 10-13), in connection with magnetic surveys throughout the state, made a magnetic survey of that portion of the Tri-State area included in the state of Missouri. In that work readings were taken at section corners and the data plotted on a contour interval of 100 gammas. In the area surveyed, there was a range of magnetic intensity of 1,311 gammas. They state that, in a general way, "the areas occupied by the faults" were magnetically low and that ore bodies are generally associated either in or on the flanks of magnetic lows. They believe that the magnetic highs are related to high points on the pre-Cambrian surface. However, since the configuration of the pre-Cambrian surface is not known, such a relationship cannot be established. Study of the published map does not reveal any marked correlation between magnetic anomalies and either structure or mineralization.
The North American Exploration Company of Houston made a brief torsion balance survey in 1926 (George, 1928). The areas surveyed included the Duenweg lease, the Federal Brewster, and the Federal Jarrett leases. In the Duenweg area, 61 stations were read over an area of 17 acres. A marked gravity maximum and a marked minimum were found, but the ore zone (at a depth of 130 feet) corresponded to neither the maximum nor to the minimum. The gravity maximum coincided with an area in which the limestone was closest to and the chert farthest from the surface. The gravity minimum corresponded to a zone where the chert was nearer to the surface. The gravity of the limestone in this case was, therefore, apparently greater than the gravity of the fractured chert plus the ore minerals. On the Federal Brewster lease there was an ore zone 15 to 20 feet thick at a depth of about 215 feet. The gravity minimum appears to correspond to areas of brecciated chert. It appears that the openings in the chert have more than counteracted the added gravity of the ore minerals with the result that the solid limestone has a higher gravity than the limestone which has been silicified, brecciated, and mineralized. The survey thus made possible a distinction, in this area, only between unaltered limestone and the silicified, brecciated limestone. On an area west of Picher, 106 stations were read on a 120-acre tract. Gravity minima correlated only with zones of brecciated chert. On the Federal Jarrett lease, 118 stations were read on a 130-acre tract over an ore zone at a depth of 300 feet. Ore was found in zones of gravity minima corresponding to zones of brecciated chert. The survey appears to indicate that gravity minima appear in those areas in which there is a large amount of chert at relatively shallow depth. The torsion balance work thus appears to be of value only in distinguishing silicified, fractured limestone from unaltered limestone. George concludes that gravity work would be of value only where: (1) there are no dumps or caves, (2) there are no mine workings, (3) there are no sandstones of great enough thickness to give gravity minima.
Several gravity-meter traverses were run for the Eagle-Picher Mining and Smelting Company in October, 1939, with stations at 100-foot intervals. The traverses were as follows: (A) a line 100 feet north and parallel to the south line of the SW sec. 14, T. 34 S., R. 23 E., Cherokee county, Kansas; (B) a line 100 feet east and parallel to the west line of the SE SW sec. 34, T. 34 S., R. 23 E., Cherokee county, Kansas, and (C) a line 4;50 feet south and parallel to the north line of the NW NW SW sec. 7, T. 35 S., R. 24 E., Cherokee county, Kansas. Line A shows a gravity range of from -2.0 to +0.2 milligals, but there is no apparent correlation between gravity and mineralization. Line B shows a gradual decrease in gravity intensity going from north to south, but there is no mineralization in the area. Line C shows several marked anomalies, but there are no geologic data available for correlation. A line over the Pelican ore body shows a range of from -1.1 to +0.8 milligals, with a low over the center of the ore-body.
In 1928 a one-week inductive radio-frequency electromagnetic survey was made by the Radiore Company, Los Angeles, to determine the location and direction of trend of conductive horizons. Several such conductors were mapped in each area. The following areas were studied: (A) SE SW and NW SE sec. 36, T. 29 N., R. 22 E., Ottawa county, Oklahoma; (B) SE NW sec. 22, T. 33 S., R. 25 E., Cherokee county, Kansas; and (C) SE NW and NE NW sec. 22, T, 44 N., R. 17 W., Moniteau county, Missouri. Drilling on the Missouri area has indicated that the conductors represented chiefly shallow underground water courses, the water being highly mineralized. There was no correlation, apparently, between the trend of the shallow conductors and the ore zones.
In 1940, F. C. Farnham, of the Missouri School of Mines, made a one-week resistivity survey across the Miami Trough at several places in Ottawa county, Oklahoma, as follows: (A) Along the south line of the NE sec. 12, T. 28 N., R. 22 E.; (B) along the south line of the SE sec. 12, T. 28 N., R. 22 E.; (C) along part of the south line of the N2 sec. 13, T. 28 N., R. 22 E.; and (D) along part of the south line of the N2 sec. 23, T. 28 N., R. 22 E. Readings were made at hundred-foot intervals. Farnham states the following (unpublished manuscript, courtesy Eagle-Picher Mining and Smelting Co.):
The low resistivity areas have been selected as the most favorable areas in which to drill because of the fact that they are probably due to a thickening of the shale over the limestone; and, since there probably is some correlation between slumpage of the limestone and the fractured zone in which the mineralization occurs, it appears that a thickening of the shale over the limestone may be used as a guide to follow in drilling. The resistivity measurements did not give data which is actually interpretable in terms of actual depth to the shale limestone contact, but did give consistent results which may be interpretable in terms of the direction of thickening of the shale.
In 1929-1930 the Schlumberger Well Surveying Corporation made resistivity surveys for the American Zinc, Lead and Smelting Company in the area around Aurora, Missouri. The only results of this work seen by us were structure contour maps drawn at the shale limestone contact or on the surface of unweathered limestone where no shale cover is present. The shale varies from 0 to 150 feet in thickness; and, in the places where the contact is shallow; later drilling has shown that the shale-limestone contact depth determinations, in most cases, were accurate to within 10 feet. As far as is known, no correlations were made between resistivity and mineralization.
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Kansas Geological Survey, Geology
Placed on web Oct. 29, 2018; originally published December, 1942.
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