Operated by The Doe Run Company, the Viburnum Trend (Trend) is the most recently discovered Southeast Missouri Lead subdistrict and is currently the only active MVT deposit in Missouri. It has been the world’s largest producer of lead since 1907 (excluding 1962), and is the fourth leading zinc producer in the US. The geology, mineralization, and mining style of the Trend is the focus of this guide. Its galena-dominant nature, as well as high concentrations of copper, cobalt, and nickel, makes it unique among other Mississippi Valley Type deposits.

Operated by The Doe Run Company, the Viburnum Trend (Trend) is the most recently discovered Southeast Missouri Lead subdistrict and is currently the only active MVT deposit in Missouri. It has been the world’s largest producer of lead since 1907 (excluding 1962), and is the fourth leading zinc producer in the US. The geology, mineralization, and mining style of the Trend is the focus of this guide. Its galena-dominant nature, as well as high concentrations of copper, cobalt, and nickel, makes it unique among other Mississippi Valley Type deposits.

Abstract The Doe Run Co.'s Casteel Mine is located in the Ozark Region of southeast Missouri just west of the community of Bixby (Fig. 1). Number 35 shaft which was begun in 1981 provides access to the mine that was dedicated posthumously to Larry W. Casteel (1915-1985), a former Division Manager and Vice President of Mining for st. Joe Minerals Corp. on November 8, 1985. St. Joseph Lead Co. discovered the ore deposit in 1957 and St. Joe Minerals Corp. (a subsidiary of the Fluor Corp.) brought the mine into production in 1985. On November 1, 1986 the Casteel Mine became part of The Doe Run Co., a partnership of Fluor Corp. and Homestake Corp.

Abstract The Magmont-West mine area is located in southeastern Missouri approximately 90 miles southwest of St. Louis along the western edge of the Viburnum Trend or New Lead Belt. During a Precambrian copper-iron exploration program which was begun in 1956 by American Zinc Company, lead-zinc mineralization was encountered in the Upper Cambrian Bonneterre Formation. Subsequent to a 1973 evaluation, which showed that the Precambrian copper-iron mineralization delineated in the West Dome area was uneconomical, emphasis was shifted to exploring for Pb-Zn mineralization in the Bonneterre Formation in the southeastern and south-central portion of the project area.

Abstract In the years since the first production from the Viburnum Trend in 1960, consolidation of mining companies and properties has occurred (Fig. 1). Today, two companies control the Viburnum Trend. The Doe Run Company operates six mines: #29, #28, Casteel, Buick, Brushy Creek, and Fletcher. ASARCO operates two mines; West Fork and Sweetwater. These are all underground, room and pillar mines accessed by vertical shafts. Doe Run also operates three mills, one primary lead smelter at Herculaneum, Missouri., and a secondary lead smelter at the site of the former Buick primary smelter. ASARCO has two mills and a primary lead smelter at Glover, Missouri. Through years of mining different parts of the same huge ore deposit, several of the mines have merged together. Today the Magmont Mine is joined on the north by the Casteel Mine and connects with the Buick Mine on the south. These connected mine workings have a combined north/south length of over 8 miles. This length will continue to increase as the Casteel Mine advances to the north and the Buick Mine advances to the south. The Buick Mine and Brushy Creek Mine are steadily mining toward each other, and the West Fork and Fletcher Mines are connected. A major portion of the southern part of the Trend is acquired land of the Mark Twain National Forest. The mineral rights are administered by the Bureau of Land Management. Property is obtained through a process of permit and subsequent lease. Rentals and royalties are paid to the U.S. Government, with royalties based on 5% of the net smelter return.

Abstract The bornite ores in the Viburnum Trend, Southeast Missouri Lead District, have received little scientific attention because of their small volumes and spotty occurrence. These ores, however, are important in providing significant information on the chemical compositions of the earliest ore-forming fluids in the ore district and they mark the focus for early fluid ingress into the Viburnum Trend. Their interesting and complex mineralogy attests to significant variations in the ore fluids through time. Their ore textures vary significantly from one locality to another, indicating that the ore-forming process differed areally at the time of their deposition. The positions of the rare lenses and pods of bornite ores are interpreted to indicate early point sources for the introduction of ore fluid in the district. The early fluids in the Viburnum Trend were ones that dominantly deposited copper sulfide minerals. They also carried significant amounts of cobalt, nickel, and especially arsenic. The replacement of early-deposited gersdorffite by the subsequently deposited copper-arsenic minerals, enargite and tennantite, shows that the chemical character of the fluids that deposited the bornite ores changed through time. Later fluids that affected the bornite pods resulted in the replacement of bornite and chalcopyrite by digenite, anilite, djurleite, and chalcocite. It is significant that bornite ores from different mines exhibit markedly different ore textures. The ores from the Fletcher mine exhibit exsolution-like textures that are interpreted to have formed by exsolution of chalcopyrite from a higher temperature bornite solid solution during cooling. Bornite ores from the Brushy Creek mine exhibit intricate colloform textures in which bornite and chalcopyrite have been rapidly and repetitively deposited., Bornite ores from the Sweetwater mine show replacement textures in which bornite clearly has replaced earlier deposited chalcopyrite. Recendy studied bornite ores from the Casteel mine exhibit a granular intergrowth of the bornite grains. These variations in ore textures appear to reflect differences in the mode of deposition and the rate of crystallization of these ores from place to place. The bornite ores have formed early in the history of deposition of the sulfide minerals in the Viburnum Trend, as shown by the fact that bornite, chalcopyrite and the other minerals forming this association have been enveloped and partly replaced by main stage cuboctahedral galena. Recent ICP analysis of 26 specimens of bornite ores has shown that, in addition to major amounts of Cu and Fe, they contain significant minor to trace amounts of some elements. Specifically, they contain as much as 1.2% Ni, 1.5% As, 0.1% Mo, 1400 ppm Co, and 173 ppm Ag. Trace amounts of Sb and Bi are present in some specimens. Ni, As, Co, and Mo contents are greatest in Fletcher bornite ores, significant in Sweetwater bornite, and less in Brushy Creek and Casteel bornite. Silver concentrations average 64 ppm in the bornite ores and are slightly less than the average for the lead-zinc ores. Chalcopyrite ores associated with the bornite ores have similar trace element signatures, and differ from typical Viburnum Trend chalcopyrite-rich ores that contain less silver. The bornite ores are interpreted to mark the positions of the early plumbing system(s) in the Viburnum Trend. They appear to indicate multiple point sources for the influx of the early ore fluids prior to the more pervasive introduction of the ore fluids into the ore district during subsequent periods of lead-zinc(-copper) ore deposition.

ABSTRACT We used geologic mapping, tephrochronology, and 40 Ar/ 39 Ar dating to describe evidence of a ca. 3.5 Ma pluvial lake in Eureka Valley, eastern California, that we informally name herein Lake Andrei. We identified six different tuffs in the Eureka Valley drainage basin, including two previously undescribed tuffs: the 3.509 ± 0.009 Ma tuff of Hanging Rock Canyon and the 3.506 ± 0.010 Ma tuff of Last Chance (informal names). We focused on four Pliocene stratigraphic sequences. Three sequences are composed of fluvial sandstone and conglomerate, with basalt flows in two of these sequences. The fourth sequence, located ~1.5 km south of the Death Valley/Big Pine Road along the western piedmont of the Last Chance Range, included green, fine-grained, gypsiferous lacustrine deposits interbedded with the 3.506 Ma tuff of Last Chance that we interpret as evidence of a pluvial lake. Pluvial Lake Andrei is similar in age to pluvial lakes in Searles Valley, Amargosa Valley, Fish Lake Valley, and Death Valley of the western Great Basin. We interpret these simultaneous lakes in the region as indirect evidence of a significant glacial climate in western North America during marine isotope stages Mammoth/Gilbert 5 to Mammoth 2 (MIS MG5/M2) and a persistent Pacific jet stream south of 37°N.