The relationship of regional structural geology to the ore deposits in the southeastern Missouri mining district

The lead deposits in the Southeastern Missouri mining district have been examined by numerous geologists and mining engineers since the original discovery about 1720. A list of the men who have reported on them includes some of the outstanding students of ore deposits. The regional geology in the mining district either was unknown or only vaguely known when most of the early examinations were made, and the discussions of the structural geology are restricted in scope owing to the lack of detailed information. The reports based on these examinations, although excellent for their time, are incomplete in view of the information now available. The major portion of the area was not mapped geologically until long after most of the reports appeared in prints hence, basic geologic data were not available to the earlier authors. The latest report of near district-wide scope was published in 1908 when detailed areal geology was available in only three quadrangles. Later stratigraphic information necessitated a revision of the areal geology in two of the three quadrangles, and they have been remapped since 1943. Maps of detailed areal geology are available now in all of the 20 quadrangles included in the mining district. Thirteen of them are mapped completely, and the other seven are mapped partially. The information gained from the geologic mapping has led to an understanding of the stratigraphy which is fundamental for a determination of the structures. Exploration and development work in the past half century has enhanced the knowledge of stratigraphy and structure. The information accumulated particularly over the past 30 years restricts the usefulness of earlier reports. These reports are valuable chiefly for their description of properties now mined out, abandoned, or otherwise inaccessible, and for their historical reviews. Discussions of the structural geology in the mining district have been neglected in the published literature. This neglect is understandable in view of the paucity of information available to the authors. The neglect may be due, in part, to the controversy about the source of the mineralizing solutions which deposited the lead ores. This controversy focused the attention of many investigators upon mineralogy and paragenesis, and the zoning of the minerals to the exclusion of district-wide structural relations of the ore deposits. An earlier report was not feasible before the last decade because of the lack of sufficient information about the district-wide stratigraphy and structural geology --Introductory Statement, pages 1, 3