Evidence for extensive hydrothermal events in the genesis of the Mississippi Valley-type (MVT) deposits of eastern Kansas and the tri-state zinc-lead mining district of Kansas, Missouri, and Oklahoma.

摘要

The Tri-State mining district of Kansas, Missouri, and Oklahoma produced a total of 23 million tons of zinc and 4 million tons of lead concentrates during 100 years of mining before production ceased in 1968. The Mississippi Valley-type minerals in eastern Kansas distal to the main ore district occur in younger Pennsylvanian rocks 180 meters above the Mississippian strata which host the mining district deposits. This study employs techniques from the fields of geology and history to determine whether or not the minerals throughout the study area are genetically related by regional hydrothermal events. Geological methods include fieldwork, petrography, fluid inclusion microthermometry, x-ray diffraction, laser ablation inductively coupled plasma mass spectrometry, strontium isotopes analyses, and thorium-lead isotopic dating. Historical sources include early accounts of the region, newspaper articles, and interviews with residents.; Thorium-lead isotopic dating of ore-stage calcite from the Jumbo mine provides an absolute age of 251 {dollar}pm{dollar} 11 ma. for the Tri-State hydrothermal events. The date also likely applies to a period of migration of petroleum, because the calcite contains primary inclusions of oil. Lead and Strontium isotopic studies indicate that the ore fluid which mineralized the Jumbo mine was homogeneous and virtually identical to fluid which formed galena in the Tri-State district.; Temperatures of homogenization for primary fluid inclusions hosted by sphalerite are 65-136{dollar}spcirc{dollar}C, and salinities are 10-24.8 weight percent equivalent sodium chloride for the study region. Samples of sphalerite collected throughout the region have similar color banding and zones of oil inclusions but could not be correlated. Some of the sphalerite has dissolution surfaces that truncate hydrocarbon zones. Elemental abundances are similar in some color bands, but also show gradational relationships with distance from the main district for cadmium, gallium, and germanium. Mineralization that took place in distal eastern Kansas is genetically related to the Tri-State ores by widespread hydrothermal events that affected an area of at least 20,000 square kilometers. Wallrock alteration adjacent to sphalerite-bearing tubes in Pennsylvanian limestone and circle-type deposits mark migration channels for the hydrothermal fluids.