Mg-chlorite

Quartz is abundant in siliceous ore, barite ore and tetsusekiei ore. Minor amounts of Mg-minerals (talc, Mg-chlorite) occur in sekko ore. Chlorite occurs in. sekko ore and it contains high amounts of Mg (Fig. 1.18). 

Mg5Al2Si30io(OH)8 + KAlSi308 + 5CaC03 + 5C02 (Mg-chlorite) (K-feldspar) (calcite)... 

Chlorite is abundant in Cu-Pb-Zn-rich deposits but is scarce in Au-Ag-rich deposits. Fe chlorite is the most common and Fe-Mg chlorite is subordinate (Shirozu, 1969). Almost all of the chlorite is classified as orthochlorite which can be regarded as part of the clinochlore-daphnite solid solution series. In general, chlorite is intimately associated with sulfide minerals such as sphalerite, galena, pyrite, chalcopyrite, and pyrrhotite. A 7 A septechlorite was reported from the Toyoha Pb-Zn deposits (Sawai, 1980). Interstratified chlorite-smectite and vermiculite-saponite are rather common minerals in Au-Ag deposits (e.g., Yoneda and Watanabe, 1981), but they have not yet been reported from other deposits. 

If Fe-Mg chlorite is assumed to be in equilibrium with a fluid phase and pyrite, the ratio of Fe + to Mg + in the fluids may be related to factors such as pH, /oj, temperature and total dissolved sulfur concentration (ES). This relationship can be derived from the following chemical reactions ... 

The variations in Fe and Mg contents of the 14 A Fe-chlorite-14 A Mg-chlorite solid solution are considered here. However, structural formulae for chlorite are not as simple as those considered here. As mentioned by Walshe and Solomon (1981), Stoesell (1984), Cathelineau and Nieva (1985) and Walshe (1986), chlorite solid solution may be represented by six components, and accurate thermochemical data on each end-member component at the hydrothermal conditions of concern are necessary to provide a far more rigorous calculation of the equilibrium between chlorite and hydrothermal solution. However, the above argument demonstrates that the composition of chlorite is a highly useful indicator of physicochemical conditions of hydrothermal solution and extent of water-rock interaction. 

Shirozu, H., Sakasegawa, T., Katsumoto, N. and Ozaki, M. (1975) Mg-chlorite and interstratified Mg-chlorite/saponite associated with Kuroko deposits. Clay ScL, 4, 305-321. 

Fig. 2.9. Relation between the Mg + and Cl concentrations of geothermal waters. The solid line indicates albite-K-feldspar-muscovite-quartz-Mg-chlorite-solution equilibrium at 250°C. For symbols used see caption to Fig. 2.2 (Shikazono, 1978a).

Shikazono (1978) theoretically derived that the concentrations of alkali and alkali earth elements in chloride-rich hydrothermal solution are nearly in equilibrium with hydrothermal alteration minerals such as albite, K-feldspar, K-mica, quartz, calcite, wairakite, and Mg-chlorite. If we use 500 mmol/kg H2O as the average Cl concentration of hydrothermal solution from the back-arc basin, which is in equilibrium with... 

Let us now imagine a process of hydrothermal alteration of arkose sandstones composed of Mg-chlorite, K-feldspar, K-mica, and quartz. Because precipitating Si02 during alteration is amorphous, we will assume the presence of amorphous silica instead of quartz, and we will consider MgO as the generic oxide / and K2O as the generic oxide j. 

Lastly, the equilibrium between Mg-chlorite and K-feldspar is depicted by Mg5Al2Si30io(OH)g + 2K + 8H++ 3Si02 <=> 2 KAlSi30g+ 5Mg ++ 8H2O. 

Let us now consider Mg-chlorite-muscovite and Mg-chlorite-K-feldspar equilibria. Because they depend on the activity of both Mg and in solution, besides H, the slope of the univariant curve is dictated by the stoichiometric coefficients of ions in reaction for reaction 8.256, the slope is and the intercept... 

Shi and Xie (1999) indicated that an acute oral LD50 value (a dose expected to result in death of 50% of the dosed animals) for stable chlorine dioxide was >10,000 mg/kg in mice. In rats, acute oral LD50 values for sodium chlorite (NaC102) ranged from 105 to 177 mg/kg (equivalent to 79-133 mg chlorite/kg) (Musil et al. 1964 Setaetal. 1991 Sperling 1959). 

Altered sperm morphology has been associated with oral exposure of rats to sodium chlorite at doses as low as 9 mg chlorite/kg/day for 66-76 days of exposure (Carlton and Smith 1985 Carlton et al. 1987). However, available data do not indicate that the endocrine pathway might be involved in this effect. 

ATSDR has derived an intermediate-duration oral MRL of 0.1 mg/kg/day for chlorite based on a NOAEL of 2.9 mg chlorite/kg/day and a LOAEL of 5.7 mg chlorite/kg/day for neurodevelopmental effects (lowered auditory startle amplitude) in rat pups that had been exposed throughout gestation and lactation via their mothers (Gill et al. 2000 same study as CMA 1996). The NOAEL of 2.9 mg chlorite/kg/day was divided by an uncertainty factor of 30 (10 for interspecies extrapolation and 3 to account for sensitive populations). 

MgO—K2O—Al2O2—SiO2—H2O system. In the stabUity-field diagram for the MgO—K2O—AI2O3— SiO2 H2O system (Fig. 15), it may be noted that all of the compositions of groundwater from the drift aquifers fall within the kaolinite stability field. However, compositions of groundwater from the bedrock aquifers also plot in the illite and Mg-chlorite fields. One possible interpretation of the distribution of these points is that a continuous spec-... 

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