590 



UNITED STATES MINERAL RESOURCES 



MISSISSIPPI VALLEY- AND ALPINE-TYPE LEAD, ZINC, AND 

 FLUORSPAR DEPOSITS AND RELATED DEPOSITS 



The Mississippi Valley-type districts contain epi- 

 genetic, low-temperature, hydrothermal deposits of 

 galena, sphalerite, and pyrite, and locally fluorite, 

 barite, chalcopyrite, calcite, and cobalt minerals. 

 These deposits have been productive in lead, zinc, 

 fluorite, and barite, and some have produced copper, 

 silver, cobalt, and nickel as byproducts. The lead in 

 the galena is of the radiogenic Joplin type ( J-type) . 

 Brown (1970) has prepared an excellent summary 

 of the geology and characteristics of the Mississippi 

 Valley-type and related deposits. At present, about 

 2 million ounces of silver per year is produced from 

 the southeast Missouri district, which makes it one 

 of the major silver-producing districts in the United 

 States. Most of the silver is recovered from sphaler- 

 ite, from some of the chalcopyrite, and from a silver- 

 lean galena. Silver is not recovered from other sul- 

 fides, such as pyrite, although locally they contain 

 some silver. 



Silver is present in small amounts in both sphaler- 

 ite and galena in the Upper Mississippi Valley dis- 

 trict. Analyses of 29 sphalerite samples range from 

 0.03 to 10 oz of silver per ton and average 0.7 oz 

 per ton (Bradbury, 1961; Hall and Heyl, 1968). 

 Analyses of 33 samples of galena range from 0.05 

 to 3 oz of silver per ton and average 0.58 of an 

 ounce per ton. 



Silver is recovered from some of the galena con- 

 centrates in the Illinois-Kentucky district, where 

 silver in galena ranges from 15 ounces per ton of 

 concentrates in Illinois to about 5 ounces per ton in 

 western Kentucky (Hall and Heyl, 1968). In many 

 veins, fluorite ores were mined, and galena and 

 sphalerite-rich ores remain. Only traces of silver 

 are known in the rest of the Mississippi Valley-type 

 districts, but in many of them almost nothing is 

 known of the silver content of minerals. 



The Appalachian Valley zinc deposits contain 

 little lead. Where galena is present, it contains 

 some silver in the range of 1-2 ounces per ton ; the 

 lead in it is not notably radiogenic. Silver has been 

 recovered from the deposits in the Embreeville, 

 Tenn., and Austinville, Va., districts. 



In many respects the lead-zinc deposits of the Alps 

 in eastern France, Austria, northern Italy, and 

 Yugoslavia resemble the Appalachian Valley zinc 

 deposits except that in the Alps the galena is much 

 more abundant than sphalerite. In all of these coun- 

 tries some silver in the galena is recovered as a 

 byproduct, but the deposits are not notably rich in 

 silver. The lead isotopes in the galena are notably 

 radiogenic in thorium lead (B-type). 



Ore deposits in the Metaline district of northeast- 

 ern Washington occur as large, irregular replace- 

 ment bodies in the Middle Cambrian Metaline Lime- 

 stone. Sphalerite and galena are the ore minerals; 

 chief gangue minerals are jasperoid, dolomite, coarse 

 calcite, and pyrite. Practically all the zinc and lead 

 has been mined from an irregular zone near the top 

 of the Metaline Limestone known as the "Josephine 

 horizon" that is characterized by widespread brec- 

 ciatioh. Other zinciferous zones are known in the 

 Metaline Limestone but have not been exploited. 

 Production from the district for the last few years 

 has been at the rate of about 200,000 tons annually 

 with a grade of 2.31 percent zinc, 0.85 percent lead, 

 and 0.036 of an ounce of silver per ton. Total pro- 

 duction of silver through 1969 amounts to 657,109 

 ounces. The potential resources of the "Josephine 

 horizon" may be as much as 1.2 million tons of 

 lead, 3.4 million tons of zinc, and 5.3 million ounces 

 of silver (Weissenborn, 1966). 



Somewhat similar deposits are found immediately 

 to the west in Stevens County, Wash. As at Metaline, 

 the deposits form replacement bodies in the Middle 

 Cambrian Metaline Limestone; zinc predominates 

 over lead ; and the silver content of the replacement 

 deposits is low but the total silver production is 

 substantial — incomplete data suggest that it 

 amounts to about 600,000 ounces. 



COPPER DEPOSITS IN SANDSTONES AND SHALES 



Blankets or lenses of disseminated copper ores, 

 in places with associated silver, and less commonly 

 with lead, zinc, cobalt, vanadium, and uranium, are 

 found throughout the world in marine and con- 

 tinental shallow-water sandstones and shales. Most 

 of these deposits have no apparent association with 

 igneous rocks. The silver is mostly in chalcocite, 

 djurleite, argentite, bornite, and chalcopyrite, and 

 their oxidation products, but some is native silver. 

 Some of the deposits are very large, such as the 

 upper Precambrian stratiform blanket deposits in 

 shale near White Pine, Mich., and the Permian 

 carbonaceous copper shales of Mansf eld (Germany) , 

 Poland, and the U.S.S.R. Copper shales in Poland 

 contain 80-750 ppm silver. Copper shales near Kom- 

 berg. West Germany, contain about 1.5 percent 

 copper and 10 ppm silver. Copper shales at White 

 Pine contain more silver than those at Kornberg. 

 The resources of White Pine are very large; more 

 than a million ounces of silver per year is currently 

 produced as a byproduct of the White Pine deposits, 

 in addition to the silver needed to produce the White 

 Pine silver-bearing Lake-brand copper, which con- 

 tains 12 ounces or more of silver per ton. A much 



