Distribution of trace elements and Pb isotopes in stream sediments of the Tri-State mining district (Oklahoma, Kansas, and Missouri), USA

Abstract

Mississippi Valley-Type (MVT) lead-zinc deposits, which account for 24% of the global resources of Pb and Zn, are found throughout the world with the largest deposits occurring in North America. The Tri-State Mining district, located at the intersection of Oklahoma, Kansas, and Missouri, was one of the most productive Pb and Zn districts during the turn of the 20th century.The current geochemical study of ore samples from the Tri-State district and of stream-sediment samples collected from selected sites from the lower Arkansas River drainage basin (the Neosho River, Tar Creek, and Spring River) show that the effect of past mining activity and leaded gasoline on Pb concentrations in the river sediment can be readily documented. Lead isotopic ratios of leachates of stream sediments from the Tar Creek area collected downstream from Picher, OK, correlate well with those of ore samples from the Tri-State Mining District, suggesting that most of the Pb adsorbed onto the stream sediments was sourced by the ores. Lead isotope measurements of leachates delimit the extent of high Pb concentrations in the Tar Creek region caused by mineralization and mining at Picher, OK. The effects of mining are noticed to a lesser extent in the Spring and Neosho rivers, with increasing distance from Picher. The influence of the leaded gasoline is more pronounced with increasing distance from the superfund site, contributing between around 52% and 68% extractable Pb to the stream sediments 14 km from the Picher mining area. This discovery can have major implications in how to evaluate the risk to human and animal health, as well as guide remediation efforts in this region.Leachates from stream-sediment samples collected from the Spring and Neosho rivers show lower Pb isotopic ratios than the Tar Creek leachates and plot outside the field defined by ore samples from the Tri-State Mining District. They fall along an array defined by a binary mixture of Pb from the leaded gasoline and the Pb sourced from the Tri-State mining district, indicative of two distinct Pb sources.There is a gradual decrease in the Zn, Pb, As, and other heavy-metal concentrations in the stream sediment leachates with distance from the mines. The Zn concentration reaches a maximum of 1592 ppm in the Picher area, more than 29 times the average natural background levels in the Tri-State region (41 ppm). About 24 km downstream from Picher, the Zn concentrations decrease substantially to values lower than both, normal crustal abundance and background levels. Similarly, the Pb concentration is highest in the Picher area (326 ppm), about 14 times the natural background levels in the Tri-State region (16 ppm), and it drops to much lower values downstream. Even though the highest Cu and As concentrations are seen in the Picher area (10 ppm and 1.44 ppm, respectively), they are lower compared to the natural background levels for the region (11 ppm and 6 ppm, respectively).