Mineral paragenesis and trace element distribution in the Tri-State zinc-lead district Missouri, Kansas, Oklahoma

A review of the literature pertaining to the mineral paragenesis and trace element distribution in the Tri-State zinc-lead district of Missouri, Kansas, and Oklahoma revealed inconsistencies in observation and in interpretation and divergent hypotheses regarding the origin of the ores. In an attempt to reconcile the data collected by many investigators over nearly three-quarters of a century, the writer observed working faces in 37 mines, collected over 2,000 specimens for binocular examination and prepared and studied 110 polished surfaces and 60 thin sections of the ores and associated rocks utilizing mineralographic, petrographic, and x-ray techniques. This detailed study resulted in the determination of a general paragenetic sequence of the minerals in Tri-State ore involving 7 periods of mineralization, each characterized by its own mineral suite and sequence, and each separated from the next by a period of tectonic activity, a period of solution, a hiatus of deposition or by a return to the crystallization of earlier formed minerals. Local deviations from the general paragenetic sequence have been noted, but the recurrence of crystallization of several minerals has been found to be more frequent than previously believed. Chalcopyrite and pyrite were found to have been deposited during 8 intervals, sphalerite and marcasite during 6, and galena and quartz during 5. Fifty-one minerals have been described from Tri-State ores, three for the first time in this thesis. Four mineral relationships previously believed to be absent in Tri-State ores have been observed and described. No significant variations in paragenetic sequence were detected either with respect to areal or stratigraphic distribution, contrary to the opinions of some who have worked in the district, but in accord with the results of previous studies of trace element distribution. Previous trace element analyses have been made of rocks, ores, soil and vegetation in the Tri-State district. Since these analyses failed to reveal any significant variation in trace element distribution, the present investigation involved spectrographic analyses of the single minerals: dolomite, galena, and sphalerite, especially selected for their freedom from included impurities as revealed under a stereoscopic microscope. Of the many elements detected spectroscopically, only silver in galena and cadmium, gallium, germanium, and indium in sphalerite were considered worthy of detailed study. In galena, silver was found to vary from 0.2 to 1.6 p.p.m. In sphalerite, cadmium varied from 4,000 to 7,000 p.p.m. gallium from 15 to 480 p.p.m. germanium from 25 to 380 p.p.m. and indium from 10 to 30 p.p.m. While such variations are large, they are wholly unrelated to areal, stratigraphic or paragenetic position, and substantiate the conclusion based on paragenetic studies that the ore-forming solutions in the Tri-State district were remarkably uniform and not significantly different from the ground water circulating in the district today. Indeed, the sulfide minerals which constitute the ores of the district are still being formed today --pages iii-iv