Fluid inclusion salinity

Ward, W. B., A. Cox, M. H. Kwong, W. J. Meyers J. L. Banner, 1993. Upper Devonian seawater samples encased in calcite cements single-phase fluid-inclusion salinities and cement compositions, Devonian reef complexes. Canning Basin, Western Australia. AAPG 1993 Annual Meeting Program 197-198. 

Marutani and Takenouchi (1978) clarified the variations in homogenization temperature and salinity of inclusion fluids in quartz from stockwork siliceous orebodies at the Kosaka mine (Fig. 1.35 Urabe, 1978). They showed that the temperature decreases stratigraphically upwards from stockwork ore zone (280-320°C) to bedded ore zone (260-310°C). Pisutha-Arnond and Ohmoto (1983) carried out fluid inclusion studies of the stockwork siliceous ores from five Kuroko deposits (Kosaka, Fukazawa, Furutobe, Shakanai, and Matsumine) and revealed that black ore minerals (sphalerite, galena, barite) and yellow ore minerals (chalcopyrite, quartz) formed at 200-330°C and 330 50°C, respectively, and salinities of the ore fluids remained fairly constant at about 3.5-6 equivalent wt% NaCl. They analyzed fluids extracted from sulfides and quartz Na = 0.60 0.16 (mol/kg H2O), K = 0.08 0.05, Ca = 0.06 0.05, Mg = 0.013 0.008, Cl = 0.82 0.32, C (as CO2) = 0.20 0.15 and less than 6 ppm each for Cu, Pb, Zn and Fe. 

ES in ore fluids is generally in a range of 10 -10 mol/kg H2O based on ES in present-day geothermal waters and fluid inclusion analytical data (Shikazono, 1972a). /ci- is represented as a function of ionic strength and temperature. Ionic strength is related to salinity which can be approximated as Cl concentration. Cl concentration can be estimated from fluid inclusion study. 

D and 5 0 data on fluid inclusions and minerals, 8 C of carbonates, salinity of inclusion fluids together with the kind of host rocks indicate that the interaction of meteoric water and evolved seawater with volcanic and sedimentary rocks are important causes for the formation of ore fluids responsible for the base-metal vein-type deposits. High salinity-hydrothermal solution tends to leach hard cations (base metals, Fe, Mn) from the country rocks. Boiling may be also the cause of high salinity of base-metal ore fluids. However, this alone cannot cause very high salinity. Probably the other processes such as ion filtration by clay minerals and dissolution of halite have to be considered, but no detailed studies on these processes have been carried out. 

Figure 1.128. Plots of homogenization temperature against salinity of fluid inclusions from the Ohe (Mn-Pb-Zn), Toyoha (Pb-Zn-Mn), and Fujigatani-Kiwada (W) deposits (Shibue, 1991).

Salinity (NaCl equivalent concentration) of inclusion fluids is 1-6 wt%, 1-14.5 wt% and 0-3 wt% for Kuroko deposits, base metal vein-type deposits, and Au-Ag vein-type deposits, respectively. These data clearly demonstrate that the salinity of inclusion fluids for the base metal-rich deposits (base metal vein-type deposits, Kuroko deposits) is higher than that of the Au-Ag vein-type deposits, while homogenization temperatures of fluid inclusion for these three types of ore deposits do not show a wide... 

Shikazono and Shimizu (1987) calculated EAu/EAg of ore fluids using fluid inclusion data (salinity, temperature), pH, mn2S and mK.+. The procedure for estimating EAu/EAg by them is given below. 

Shikazono and Shimizu (1987) concluded that Ag contents of gold precipitated from low-salinity fluids is higher than that prediction and the relationship between NAg of gold and salinity of fluid inclusions estimated from freezing temperature data. Therefore, another interpretation is that NAg of gold from shale-hosted deposits is lower than that from sandstone-hosted deposits, because shale is expected to be richer in Cl mainly due to adsorption by clay minerals included in shale than sandstone. 

Geological, mineralogical and geochemical features of these deposit types (distribution, age, associated volcanism, host and country rocks, fluid inclusions, opaque, gangue and hydrothermal alteration minerals, chemical features of ore fluids (temperature, salinity, pH, chemical composition, gaseous fugacity, isotopic compositions (O, D, S, Sr/ Sr, Pb), rare earth elements)) were summarized. 

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. 

Oquartz results for the two deposits are very similar regardless of vein types with averages of +15.7 0.6 %o (la, n=11) for Dufferin and +15.2 0.9 %o (la, n=15) for The Ovens. In addition, there is limited spread in the data for each area despite different vein types having been analyzed. Thus, although veins are classified based on structural type and appearance (e.g., laminated vs. non-laminated, saddle vs. limb, stratabound vs. discordant), the S Oquartz values are the same. In addition, fluid inclusions are similar in quartz from the two areas, with low-salinity (i.e., <6-8 wt% NaCb equiv.) aqueous-carbonic (Xco2 = 0.1-0.3) types dominant. 

Abstract world class unconformity-related U deposits occur in the Proterozoic McArthur Basin (Northern Territory, Australia) and Athabasca Basin (Saskatchewan, Canada). Widespread pre-to post-ore silicifications in the vicinity of the deposits, allow proper observation of paragenetically well-characterized fluid inclusions. We used a combination of microthermometry, Raman microspectroscopy and Laser Induced Breakdown Spectroscopy (LIBS), to establish the physical-chemical characteristics of the main fluids having circulated at the time of U mineralization. The deduced salinities, cation ratios (Na/Ca, Na/Mg) and P-T conditions, led to the detailed characterization of a NaCI-rich brine, a CaCl2-rich brine and a low-salinity fluid, and to the identification of mixing processes that appear to be key factors for U mineralization. 

B) The brines are produced by leaching of saline fluid inclusions in crystalline rocks or by intense water/rock interactions (Frape and Fritz 1987)... 

Knauth LP, Beeunas MA (1986) Isotope geochemistry of fluid inclusions in Permian hahte with implications for the isotopic history of ocean water and the origin of saline formation waters. Geochim Cosmochim Acta 50 419 33... 

Clifford 2000). Many metallic ore and evaporite minerals contain methane, though not in hydrate form. For instance, the Red Dog zinc ores mentioned above contain methane inclusions in association with saline inclusions. In many instances, microscopic methane and carbon-dioxide-rich fluid inclusions form clathrates within their tiny hydrous envelopes. Some salt deposits are so enriched in high-pressure free gas inclusions and/or gas hydrates that mining, crushing under boot, or other means of physical disturbance causes popping or even explosive decrepitation. 

De Vivo, B., Torok, K., Ayuso, R. A., Lima, A., and Lirer, L. (1995). Fluid inclusion evidence for magmatic silicate/saline/C02 immiscibility and geochemistry of alkaline xenoliths from Ventotene island (Italy). Geochim. Cosmochim. Acta 59, 2941—2953. 

Scambelluri M., Piccardo G. B., Philippot P., Robbiano A., and Negretti L. (1997) High salinity fluid inclusions formed from recycled seawater in deeply subducted alpine serpentinite. Earth Planet. Sci. Lett. 148, 485 -499. 

Schmidt C. and Bodnar R. J. (2000) Synthetic fluid inclusions XVI. PVTX properties in the system H20-NaCl-C02 at elevated temperatures, pressures, and salinities. Geochim. Cosmochim. Acta 64, 3853-3869. 

Experimental work on the solubility of CH4 (e.g., Haas, 1978 Price, 1979) permits estimation of the solubility of CH4 over much of the range of pressures, temperatures, and salinities characteristic of sedimentary basins (Kharaka et al., 1988 Spycher and Reed, 1988). High concentrations of CH4 have been found in the two-phase fluid inclusions in sedimentary ore deposits and in diagenetic mineral overgrowths, and corrections... 

Banks D. A., Gleeson S. A., and Green R. (2000) Determination of the origin of salinity in granite-related fluids evidence from chloride isotopes in fluid inclusions. J. Geochem. Explor. 69-70, 309-312. 

The sources of the saline fluids are argued by some to be water-rock interaction based on the presence of abundant chloride in mineral phases, fluid inclusions, and the incorporation of water into minerals as ways to increase sahnity. The strong similarity of fluids and mineral chemistry, especially for parameters such as strontium isotopes, is cited as evidence for the water-rock model of origin. 

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