Abstract
Clay-mineral alteration in a carbonaceous shale bed seems to be related to hydrothermal zinc-lead depositions in the Upper Mississippi Valley district in southwestern Wisconsin, northwestern Illinois, and northeastern Iowa. A 3-in. thick, dark-brown, carbonaceous shale at the base of the Quimbys Mill Member of the Platteville Formation can be traced accurately in the Thompson-Temperly mine near New Diggings, Wis., through the ore bodies into alteration aureoles around the ore bodies and out into areas barren of mineralization or apparent alteration.
X-ray diffraction studies indicate a progressive alteration of the clay-mineral and, in part, nonclay-mineral components of the shale from unaltered rock into ore-zone rock. Illite of md polymorph in unaltered rock is altered to 1 m and 2 m illite in the altered rock, and 2 m illite polymorph increases markedly within the ore bodies. Accompanying this alteration, calcite decreases and dolomite and microcline increase in amount toward the ore zone; quartz remains unchanged. The conclusion that the alteration was effected by low-temperature and low-pressure environment over a geologically long period of ore deposition is supported by fluid-inclusion studies of the associated ore minerals, which indicate a maximum temperature of 120°C to 130°C, and the known stability of synthesized 1 m and 2 m mica polymorphs at 200°C and 15,000 psi water pressure.
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References
Anderson, C. A. (1950) Alteration and metallization in the Bagdad porphyry copper deposit, Ariz.: Econ. Geology, v.45, pp.609–628.
Bailey, S. W., and Cameron, E. N. (1951) Temperatures of mineral formation in bottom-run lead-zinc deposits of the Upper Mississippi Valley, as indicated by liquid inclusions: Econ. Geology, v.46, No. 6, pp.626–651.
Brown, G., editor (1961) The X-ray identification and crystal structures of clay Minerals: Mineralogical Society, London, 544 pp.
Heyl, A. V., Agnew, A. F., Lyons, E. J., and Behre, C. H., Jr. (1959) The geology of the Upper Mississippi Valley zinc-lead district: U.S. Geol. Survey Prof. Paper 309, 310 pp.
Kerr, P. F. (1951) Alteration features at Silver Bell, Arizona: Geol. Soc. America Bull., v.62, pp.451–480.
Lovering, T. S. (1949) Rock alteration as a guide to ore—East Tintic district, Utah: Econ. Geology, Mon. 1, 65 pp.
Ostrom, M. E. (1961) Separation of clay minerals from carbonate rocks by using acid: Jour. Sed. Petrology, v.31, No. 1, pp.123–129.
Sales, R. H., and Meyer, C. (1948) Wall rock alteration at Butte, Mont.: Am. Inst. Mining and Metall. Engineers, Tech. Pub. No. 2400, 25 pp.
Schwartz, G. M. (1953) Geology of the San Manuel copper deposit, Arizona: U.S. Geol. Survey Prof. Paper 256, 65 pp.
Tooker, E. W. (1963) Altered wall rocks in the central part of the Front Range mineral belt, Gilpin and Clear Creek Counties, Colorado: U.S. Geol. Survey Prof. Paper 439, 102 pp.
Yoder, H. S., and Eugster, H. P. (1955) Synthetic and natural muscovites: Geochim. et Cosmochim. Acta, v.8, pp.225–280.
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Heyl, A.V., Hosterman, J.W. & Brock, M.R. Clay-Mineral Alteration in the Upper Mississippi Valley Zinc-Lead District. Clays Clay Miner. 12, 445–453 (1963). https://doi.org/10.1346/CCMN.1963.0120139
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DOI: https://doi.org/10.1346/CCMN.1963.0120139