Barite and Anhydrite

A narrow band with a main shoulder at 302 nm with a very short decay time of Ri 25 ns, and another with shoulders at 330 and 360 nm with a longer decay of 75 ns (Fig. 4.31c,d) in time-resolved spectra have spectral-kinetic 

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Isotopic compositions of minerals and fluid inclusions can be used to estimate those of Kuroko ore fluids. Estimated isotopic compositions of Kuroko ore fluids are given in Table 1.10. All these data indicate that the isotopic compositions lie between seawater value and igneous value. For instance, Sr/ Sr of ore fluids responsible for barite and anhydrite precipitations is 0.7069-0.7087, and 0.7082-0.7087, respectively which are between present-day. seawater value (0.7091) and igneous value (0.704-0.705). From these data, Shikazono et al. (1983), Farrell and Holland (1983) and Kusakabe and Chiba (1983) thought that barite and anhydrite precipitated by the mixing of hydrothermal solution with low Sr/ Sr and seawater with high Sr/ Sr. 

Farrell, C.W., Holland, H.D. and Petersen, U. (1978) The isotopic composition of strontium in barites and anhydrites from Kuroko deposits. Mining Geology, 28, 281-291. 

Kusakabe, M. and Chiba, H. (1983) Oxygen and sulfur isotopic composition of barite and anhydrite Irom the Fukazawa deposit, Japan. Econ. Geol. Mon. 5, 292-301. 

Sulfates (barite and anhydrite) precipitate due to the mixing of discharging hydrothermal solution with cold seawater above the seafloor at an early stage of hydrothermal activity. Ca and Ba in hydrothermal solution react with SO in cold seawater, leading to the precipitations of anhydrite and barite. It is observed that anhydrite precipitated earlier than barite. This may depend on the initial Ca and Ba concentrations of end member hydrothermal solutions, temperature and degree of mixing of hydrothermal solutions and... 

Barite and anhydrite occur in the massive pyritic ores. Barite occurs frequently in the sphalerite-rich layers of the massive ores in the Chihara deposit (Kanehira, 1959). 

Luminescence of in synthetic alkaline earth sulfates is well known (Folk-erts et al. 1995). In this study, CaS04 Pb shows an emission band with a maximum at 235 nm at 300 K, while the excitation maximum is at 220 nm. The decay curve of the emission is single exponential with a decay time of 570 ps at 4.2 K. The emission spectrum of BaS04 Pb demonstrates a broad band peaking at 340 nm with an excitation maximum at 220 nm, while in SrS04 Pb the luminescence band has a maximum at 380 nm. hi natural barite and anhydrite samples we detected several narrow UV bands, which may be connected with Pb emission, but for confident conclusion additional study is needed. In any case, Pb participation in natural sulfates liuninescence has to be taken into consideration. 

Carbonates and Sulfates Carbonates include limestone, cal-cite, marble, marls, chalk, dolomite, and magnesite the most important sulfates are barite, celestite, anhydrite, and gypsum these are used as fillers in paint, paper, and rubber. (Gypsum and anhydrite are discussed below as part of the cement, lime, and gypsum industries.)... 

Estimated total amount of barite and sekko (gypsum + anhydrite) (Shikazono, 1983)... 

Kuroko deposits are characterized by large amounts of sulfate minerals (barite, anhydrite, and gypsum). Estimated total amount of barite and sekko (gypsum + anhydrite) from individual deposit is shown in Table 1.4. Sr contents of gypsum, anhydrite and barite... 

After Sakai s pioneering work, Watanabe and Sakai (1983) and Kusakabe and Chiba (1983) analyzed large amounts of barite, gypsum and anhydrite for 8 4s and 8 0 and confirmed the conclusion drawn by Sakai et al. (1970) (Fig. 1.43). 

Figure 1.46. REE patterns of the altered volcanogenic rocks and Kuroko ores. Data sources Shikazono (1999a). (A) Hydrothermally altered dacite and anhydrite underlying the Kuroko ores. (B) Barite, Kuroko ore and ferruginous chert. (C) Hydrothermally altered basalt overlying the Kuroko ores (Shikazono, 1999a).

At the time of its injection into seawater, most of the particulate material in the plumes is composed of metal sulfides, anhydrite, barite, and quartz. As the plumes... 

At 77 K the relative intensity of the band at 605 nm with an even longer decay time of 25 ms is much stronger. Such bands are usually connected with Mn +, but Mn " " in barite has different luminescence. Mn " in anhydrite CaS04 is characterized by a narrow band peaking at 505 nm. Thus such a band in barite may be connected with Ca impurity and anhydrite type local structure. 

Other dissolved components originate by reaction of the fluid with the sedimentary phases, K-feldspar, calcite, dolomite, anhydrite, celestite, barite and fluorite. Significant quantities of Pb, Zn and Fe have been mobilized as well. 

Shikazono et al. (2012) used precipitation kinetics-fluid flow model to explain the mode of occurrences of barite, quartz and anhydrite in Kuroko deposits (submarine hydrothermal polymetallic sulfide-sulfate massive deposits in Japan). 

The common foulants group includes calcite, barite, witherite, and anhydrite saturation levels. 

Dominant gangue minerals in Kuroko deposits are quartz, barite, anhydrite, gypsum, chlorite, sericite, and sericite/smectite. Morphology of quartz changes from euhedral in the centre to the irregular in the margin of the deposits (Urabe, 1978). No amorphous silica and cristobalite have been found. 

Strontium isotopes. Strontium isotopic compositions ( Sr/ Sr) of anhydrite, gypsum and barite from Kuroko deposits are summarized in Fig. 1.45 (Farrell et al., 1978 Honma and Shuto, 1979 Farrell and Holland, 1983 Yoneda et al., 1993 Yoneda and Shirahata, 1995). Sr/ Sr values of anhydrite and gypsum are slightly lower than that of seawater, suggesting that most of the strontium was derived from seawater, but a small amount of... 

Strontium was from igneous rocks. Sr/ Sr ratios of barite are in a range from 0.706 to 0.708, suggesting smaller contribution of seawater strontium than anhydrite and gypsum. 

Amorphous silica and barite precipitate simultaneously from white smoker in midoceanic ridge hydrothermal system (Edmond et al., 1979). It is inferred that amorphous silica precipitates in the chimney at a later stage than sulfides and sulfates (anhydrite and barite) which constitute chimneys from which black smoker is emerging. 

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