The H 2 O-NaCl-MgCl 2 ternary phase diagram with special application to fluid inclusion studies

Dubois, Michel; Marignac, C.

doi:10.2113/gsecongeo.92.1.114

Cited by 63 publications

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“…The part of the H 2 O-NaCl-MgCl 2 system with relatively low salinities can be modelled with purely empirical equations [10] and activity coefficients [6,7]:, the ice field, hydrohalite field and MgCl 2 ·12H 2 O field ( Figure 3). The halite field is only characterized by a limited amount of experimental data.…”

Section: H 2 O-nacl-mgcl 2 Systemmentioning

confidence: 99%

“…The variety of models may result in inconsistent salinity estimations, for example in the H 2 O-NaCl-MgCl 2 system, c.f. [6] and [10]. Significant differences also exist between purely empirical models of the same system, for example the H 2 O-NaClCaCl 2 system, c.f.…”

Section: Inconsistent Modelsmentioning

confidence: 99%

“…In addition, this ternary is modelled with purely empirical equations [13][14][15] that cover only part of the compositional variation. The H 2 O-NaCl-MgCl 2 system was only modelled for H 2 O-rich compositions [6,10] at temperatures below 25…”

Section: Introductionmentioning

confidence: 99%

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Unexpected phase assemblages in inclusions with ternary H2O-salt fluids at low temperatures

Bakker

Baumgärtner

2012

Open Geosciences

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Phase assemblages and temperatures of phase changes provide important information about the bulk properties of fluid inclusions, and are typically obtained by microthermometry. Inclusions are synthesized in natural quartz containing an aqueous fluid with a composition in the ternary systems of H 2 O-NaCl 2 -CaCl 2 , H 2 O-NaCl-MgCl 2 , and H 2 O-CaCl 2 -MgCl 2 . This study reveals that these fluid inclusions may behave highly unpredictably at low temperatures due to the formation of metastable phase assemblages. Eutectic temperatures cannot be detected in most of the fluid inclusions containing these ternary systems. Nucleation of a variety of solid ice and salt-hydrate phases in single fluid inclusions is often partly inhibited. Raman spectroscopy at low temperatures provides an important tool for interpreting and understanding microthermometric experiments, and visualizing stable and metastable phase assemblages. Final dissolution temperatures of ice, salt-hydrates, and salt must be treated with care, as they can only be interpreted by purely empirical or thermodynamic models at stable conditions. Keywords

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Section: H 2 O-nacl-mgcl 2 Systemmentioning

confidence: 99%

Section: Inconsistent Modelsmentioning

confidence: 99%

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Unexpected phase assemblages in inclusions with ternary H2O-salt fluids at low temperatures

Bakker

Baumgärtner

2012

Open Geosciences

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“…The low T fm measurements indicate the presence of cations other than Na (i.e., Ca, Fe, Mg; Borisenko 1977, Vanko et al 1988, Dubois & Marignac 1997. The mound data confirm that a complex, multicomponent system exists and, furthermore, they provide important information regard- ing the relative abundance of the components that could not be ascertained from the thermometric measurements.…”

Section: Comparison Of Decrepitate and Thermometric Datamentioning

confidence: 70%

“…More complicated compositions can, however, be determined by using the sequential freezing method (Haynes 1985, Goldstein & Reynolds 1994, in which hydrates (e.g., hydrohalite, gas clathrates) can be identified and their melting temperatures determined. In these cases, use of the appropriate ternary system will provide an estimate of the bulk composition of the system, as has been demonstrated for the system H 2 O-NaCl -CaCl 2 (Vanko et al 1988, Oakes et al 1990) and H 2 ONaCl-MgCl 2 (Dubois & Marignac 1997). However, the difficulty of discriminating between low-to moderatesalinity fluids dominated by NaCl or KCl, as well the difficulty in interpreting the phase changes in complex multicomponent systems, given the problems of metastability (e.g., Samson & Walker 2000), limits the potential use of eutectic measurements to infer fluid composition.…”

Section: Introductionmentioning

confidence: 98%

Analysis of Evaporate Mounds as a Complement to Fluid-Inclusion Thermometric Data: Case Studies From Granitic Environments in Nova Scotia and Peru

Kontak¹

2004

The Canadian Mineralogist

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The bulk composition of fluid inclusions is generally determined by using the temperature of ice melting (i.e., freezing-point depression of H 2 O-NaCl) and relating this to the ice-melting curve in the two-component system H 2 O-NaCl. In reality, natural systems are more complex. Therefore, the bulk composition is referred to as equivalent wt.% NaCl to account for the presence of other, generally undetermined, cations (e.g., K, Ca, Fe, Mn, Mg). Inferences of a more complex chemical composition are generally made on the basis of the depression of the eutectic temperature for the H 2 O-NaCl system (-21.2°C), the other common solutes being CaCl 2 , MgCl 2 , and FeCl 2 . Such an approach is qualitative at best, and the inherent problem of metastability invites caution. An alternative, relatively simple and cost-effective method among the many analytical methods available, is to artificially decrepitate fluid inclusions and analyze the resulting evaporate mounds with an electron microprobe equipped with an imaging system. To illustrate the potential of the method, three granitic environments, in Nova Scotia and in Peru, were chosen, two mineralized (Sn, Cu, Zn) and one barren (tourmaline pegmatite). Standard fluid-inclusion thermometric data have been integrated with compositions determined from evaporate mounds in the same suite of samples. The following points emerge: (1) the inclusions are invariably multi-component, being dominated by Na-K-Ca, but in consistently different proportion that reflect protracted fluid:rock interaction and mixing of reservoirs; (2) the low first-melting temperatures (i.e., <-50°C) do not unequivocally indicate the presence of CaCl 2 in solution; (3) high concentrations of Fe and Mn are common within the mineralized systems examined, in addition to lesser amounts of Sr, Ba, P and Zn, and (4) the two methods complement each other, together providing a much more comprehensive account of the nature of the fluid and its evolution in space and time.Keywords: fluid inclusions, evaporate mounds, granites, pegmatites, tin mineralization. Nova Scotia, Peru. SOMMAIRELa composition globale de la phase fluide piégée dans les cristaux est généralement établie au moyen de la température de fusion de la glace, c'est-à-dire, l'abaissement du point de congélation de l'eutectique du système H 2 O-NaCl, mis en relation avec la courbe décrivant la fusion de la phase solide dans le système binaire H 2 O-NaCl. En fait, les systèmes naturels sont plus complexes. Pour cette raison, la composition globale du fluide est exprimée en termes d'équivalents de NaCl afin de rendre compte d'autres cations, non déterminés, par exemple K, Ca, Fe, Mn, Mg. Des conclusions à propos de la composition chimique plus complexe sont généralement faites pour rendre compte de l'abaissement de l'eutectique en dessous de -21.2°C, sa valeur dans le système H 2 O-NaCl. Les autres solutés courants sont CaCl 2 , MgCl 2 , et FeCl 2 . Une telle approche est définitivement qualitative, et le problème de métastabilité mérite une att...

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North African Mississippi Valley‐Type Deposit and Its Link with the Alpine Chain Evolution

BOUABDELLAH

2023

Metallic Resources 2

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The H 2 O-NaCl-MgCl 2 ternary phase diagram with special application to fluid inclusion studies

Cited by 63 publications

References 0 publications

Unexpected phase assemblages in inclusions with ternary H2O-salt fluids at low temperatures

Unexpected phase assemblages in inclusions with ternary H2O-salt fluids at low temperatures

Analysis of Evaporate Mounds as a Complement to Fluid-Inclusion Thermometric Data: Case Studies From Granitic Environments in Nova Scotia and Peru

North African Mississippi Valley‐Type Deposit and Its Link with the Alpine Chain Evolution

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