Alunite

The CAS registry Hsts 5,037 aluminum-containing compounds exclusive of alloys and intermetaUics. Some of these are Hsted in Table 1. Except for nepheline and alunite in the USSR and Poland, bauxite is the raw material for all manufactured aluminum compounds. The term bauxite is used for ores that contain economically recoverable quantities of the aluminum hydroxide mineral gibbsite or the oxide—hydroxide forms boehmite and diaspore. 

AI2O2 TSO 9H20, which is stmcturaUy related to alunite [12588-67-9] K2Alg(SO (OH) 2 (1 )-... 

Potassium alum is manufactured by treating bauxite with sulfuric acid and then potassium sulfate. Alternatively, aluminum sulfate is reacted with potassium sulfate, or the mineral alum stone, alunite, can be calciaed and leached with sulfuric acid. Alunite is a basic potassium aluminum sulfate... 

Alaunerde,/. alumina, alaunerdehaltig, a. aluminiferous. Alaun-erdesulfat, n. sulfate of alumina (aluminum sulfate), -erz, n. alunite. -fass, n. (L ol/ier) alum vat. -fels, m. alunite. -festig-keit,/. Paper) alum resistance, alaun-ftirmig, a. aluminiform. -gar, a. dressed with aluQi, alumed, tawed. 

Alaun-schiefer, m., -schiefererz, n. alum slate, alum shale. -seife, /. aluminous soap, -sieden, n. alum boiling, alum making, -sieder, m. alum boiler, -siederei, /. alum works, -stein, -spat, m. alum stone, alunite. alaunt, p.a. alumed. 

Most of epithermal precious-metal vein-type deposits in Japan can be classed as adularia-sericite-type, and low sulfidation-type. Very few hot spring-type deposits (quartz-alunite-type, high sulfidation-type) are found in the Japanese Islands. A summary of various characteristic features of adularia-sericite type (low sulfidation-type) is given mainly in section 1.4. 

Superimposed alterations are common in the Kuroko mine area (Inoue and Utada, 1991). For example, K-feldspar, kaolinite, alunite, pyrophyllite and diaspora alterations cut chlorite alteration, indicating that they formed later than chlorite alteration (Inoue and Utada, 1991). Inoue and Utada (1991) thought, based on detailed descriptions of the hydrothermal alterations in the Kamikita mine area. North Honshu, that hydrothermal alterations in this district started from 13 Ma and ended at 3-4 Ma. 

Advanced arigillic alteration is found at the upper horizon than the sites of potassic and intermediate argillic alterations where the Au-Ag mineralization occurs (e.g., Seigoshi, Yatani, Kushikino, Hishikari). This type of alteration takes blanket-form in upper part and vein-form in lower part (Iwao, 1962 Shikazono, 1985a). The conspicuous zonation from upper to lower horizon is known at the Ugusu silica deposit, namely, silica zone, alunite zone, kaolinite zone and montmorillonite zone (Iwao, 1949, 1958, 1962). 

The fluid inclusions can be divided into two types vapor- and liquid-rich fluid inclusions. The filling degree of fluid inclusions from some samples from the silicified and alunite zones is variable and homogenization temperatures vary widely. This indicates... 

If alunite, K-mica and kaolinite (which are common minerals in the advanced argillic alteration) are in equilibrium, the concentration of H2SO4 can be estimated based on the experimental work by Hemley et al. (1969) the concentration of H2SO4 at 200°C and 300°C is 0.002 and 0.012 M, respectively. This may suggest that it is difficult to form such a high concentration of sulfate ion only by oxidation of H2S. 

This type of mixing could reasonably explain the occurrence of acidic alteration minerals such as kaolinite and alunite in the low-sulfidation epithermal gold vein district (e.g., Seta in northeast Hokkaido, Hishikari in southern Kyushu) (Yajima et al., 1997)... 

The deposits are characterized by conspicuous alteration zoning from the centre (orebody) to margin (Tokunaga, 1955 Doi, 1972 Urashima et al., 1981, 1987). They are siliceous zone, alunite zone, kaolinite zone, sericite zone and montmorillonite zone. 

Figure 1.196. /oj-pH ranges for hot-spring-type deposits and low sulfidation-type deposits. Temperature = 250°C, ES = 0.01 mol/kg H2O, ionic strength = 1. Ka kaolinite, Al alunite, SI liquid sulfur, Kf K-feldspar, Hm hematite, Mt magnetite, Py pyrite, Po pyrrhotite. Bn bomite, Cp chalcopyrite. 

Aoki, M., Comsti, E.C., Florin, B.L. and Matsuhisa, Y. (1993) Evolution of the hydrothermal system with special reference to the geochemistry of alunite solid-solution. Baguio Report of Research and Development Cooperation 1717 Project, 8741, 42-63. 

Berger, B.R. (1983b) Epithermal gold, quartz-alunite type. In Cox, D.P. (ed.), GEOMINAS Mineral Resource Assessment of Columbia — Ore Deposit Models, U.S. Geological Survey, Open-File Report, 83, v. 23, 40-41. 

Iwao, S. (1949) The alunite deposits in Japan (app. silica deposit of the Ugusu Mine). Geol. Surv. Japan, Rept. No. 130 (in Japanese with English abst.). 

Iwao, S. (1962) Silica and alunite deposits of the Ugusu mine a geochemical consideration on an extinct geothermal area in Japan. Japan. J. Geol. Geogr., 33, 131-144. 

Polyak VJ, McIntosh WC, Provencio P, Giiven N (1998) Age and Origin of Carlsbad Caverns and related caves from " °Ar/ Ar of alunite. Science 279 1919-1922 Porcelli D, Swanzenski PW (2003)The behavior of U- and Th- series nuclides in groundwater. Rev Mineral Geochem 52 317-361... 

The model calculated in this manner predicts that two minerals, alunite [KA13(0H)6(S04)2] and anhydrite (CaSC>4), are supersaturated in the fluid at 175 °C, although neither mineral is observed in the district. This result is not surprising, given that the fluid s salinity exceeds the correlation limit for the activity coefficient model (Chapter 8). The observed composition in this case (Table 22.1), furthermore, actually represents the average of fluids from many inclusions and hence a mixture of hydrothermal fluids present over a range of time. As noted in Chapter 6, mixtures of fluids tend to be supersaturated, even if the individual fluids are not. 

To avoid starting with a supersaturated initial fluid, we use alunite to constrain the SO4 content to the limiting case, and anhydrite to similarly set the calcium concentration. The resulting SO4 concentration will fall near the lower end of the range shown in Table 22.1, and the calcium content will lie slightly above the reported value. 

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