Fluid Regime in Southern Norway: The Record of Fluid Inclusions

Touret, Jacques

doi:10.1007/978-94-009-5450-2_30

Cited by 103 publications

(67 citation statements)

References 24 publications

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“…This led to the proposal of fluid stratification in the earth's crust with the upper regions dominated by H 2 O and brine solutions with variable amounts of CH 4 and/or N 2 . The deeper portions on the other hand, are rich in CO 2 H 2 O fluids that merge into a dominantly CO 2 rich lower crust (Touret, 1985). The common occurrence of CO 2 rich inclusions in rocks that were generated in the deeper parts of the crust serves as a strong evidence for this model.…”

Section: Introductionmentioning

confidence: 92%

"Ultrahigh density" carbonic fluids in ultrahigh-temperature crustal metamorphism

Santosh

Tsunogae

Yoshikura

2004

Journal of Mineralogical and Petrological Sciences

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Ultrahigh temperature (UHT) granulites in Tonagh Island, Napier Complex, East Antarctica record peak metamorphic pressure temperature (P T) conditions of up to 9 kbar and 1100°C. Sapphirine, garnet, orthopyroxene and quartz in these rocks contain very high density fluid inclusions with melting temperatures close to that of pure CO 2 (−56.6°C) and homogenization temperatures down to −34.9°C translating into high CO 2 densities (up to 1.07 g/cm 3 ). The UHT granulites of Vizianagram in Eastern Ghats Belt, India which were subjected to extreme crustal metamorphism at >1000°C and 8 9 kbar also carry very high density (up to 1.15 g/cm 3 ) pure CO 2 inclusions in quartz adjacent to spinel rimmed by various coronas of sillimanite, orthopyroxene and garnet. Garnets in a granulite facies rock from Salem in southern India that equilibrated at peak P T conditions of 740 800°C and 9 11 kbar carry the highest density (1.17 g/cm 3 ) pure CO 2 yet reported from continental crust. This rock also contains very high density CO 2 inclusions in plagioclase and quartz. High density (0.998 g/cm 3 ) pure CO 2 rich fluid inclusions also occur abundantly within garnets from a mafic granulite in Ampitiya, central Highland Complex, Sri Lanka. The peak P T conditions of metamorphism of the mafic granulite are around 10.6 kbar and 985°C with subsequent rapid isothermal decompression along a clock wise path down to 5.5 kbar. In most of the cases above, the representative isochores for the CO 2 inclusions either penetrate through or pass very close to the P T windows defined from mineral phase equilibria indicating that the fluid inclusions were trapped at the time of peak or near post peak metamorphism. We thus recognize a group of "ultrahigh density" (UHD) CO 2 rich fluids that characterize UHT rocks and other granulites formed under extreme crustal metamorphism. These fluids contrast sharply with the lower density (generally <1.0 g/cm 3 ) CO 2 inclusions commonly reported from normal granulite facies rocks in various terrains. The presence of "synmetamorphic" UHD CO 2 within various minerals is consistent with the low water activities predicted by the mineral assemblages in these rocks. Although the source of the CO 2 is equivocal, mantle derived mafic magmas could have provided the heat and volatiles required for crustal metamorphism at extreme conditions displayed by these rocks.

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Section: Introductionmentioning

confidence: 92%

"Ultrahigh density" carbonic fluids in ultrahigh-temperature crustal metamorphism

Santosh

Tsunogae

Yoshikura

2004

Journal of Mineralogical and Petrological Sciences

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“…The CO 2 -rich fluid inclusions often found in high-grade rocks led Newton et al (1980) to suggest that dilution of H 2 O by CO 2 may explain reduced a H 2 O ; however, this is not consistent with petrologic observations (e.g., Lamb et al, 1987). Brine and vapor immiscibility may offer a better explanation (Touret, 1985;Newton et al, 1998;Newton and Manning, 2010) because the wetting properties of the CO 2 -rich vapor phase lead to preferential entrapment as fluid inclusions relative to the brine phase (Gibert et al, 1998). In addition, the brine component can generate significant metasomatism (see below), while the requirement of reduced a H 2 O is satisfied.…”

Section: Activity-composition Relations and Petrologic Consequences Omentioning

confidence: 83%

“…The presence of CO 2 in modest concentrations leads to phase separation in multicomponent saline fluids. The H 2 O-CO 2 component of this two-fluid system is well represented in fluid inclusions, but brines are not due to their wetting properties (e.g., Touret, 1985;Newton et al, 1998). Yet the brine component is likely responsible for much of the geochemical signature imparted by the fluid phase: mineral solubilities are dramatically higher in H 2 O-salt solutions, they are capable of shifting the oxidation state of the rock with which they interact, and they can cause large changes in REE geochemistry.…”

Section: Discussionmentioning

confidence: 99%

“…1). Touret (1985Touret ( , 1995 reported apparently primary crystallinesalt-bearing fluid inclusions in minerals from the highest grade, Rb-depleted granulite facies zone of the Bamble region, S. Norway. He inferred that granulite-facies metamorphism was accompanied by a near-saturated supercritical brine and an immiscible CO 2 -rich phase.…”

Section: Introductionmentioning

confidence: 99%

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Brines at high pressure and temperature: Thermodynamic, petrologic and geochemical effects

Manning

Aranovich

2014

Precambrian Research

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a b s t r a c tA number of observations point to the participation of brines in high-grade metamorphic processes. These include findings of alkali and alkaline-earth halides as daughter crystals in fluid inclusions, appreciable concentrations of Cl measured in amphiboles, biotite, scapolite and apatite, and direct observations on high-temperature halides present in the intergranular space in high-grade rocks. This paper reviews some thermodynamic, petrologic and geochemical effects of these brines. Thermodynamic mixing properties of concentrated water-salt fluids at high pressure (P) and temperature (T) differ greatly from those of water-non-polar gas mixtures: the former are characterized by a large negative deviation from ideal solutions, while the latter exhibit positive deviation from ideality. The contrasting behavior has three major petrologic implications. First, compared to mixtures of water and non-polar gases, brines more strongly increase the melting temperature of quartzofeldspathic rocks and more strongly decrease dehydration temperature of water-bearing minerals. This allows a wide P-T window in which subsolidus deep-crustal metasomatism may take place at relatively low H 2 O activity (a H 2 O ) via migrating fluids. In addition, above 2-3 kbar, brine-saturated solidi for simple granite melting show positive dP/dT at constant H 2 O mole fraction (X H 2 O ), favoring ascent of fluid-saturated liquids. Finally, a large miscibility gap exists in H 2 O-CO 2 -salt ternaries at lower crustal conditions, which may concentrate salts in a separate phase and help explain the common observation of CO 2 -rich inclusions in high-grade minerals. We discuss three geochemical consequences of high-grade brines. We report new experimental data on melting of a model granitoid liquid (69 wt% NaAlSi 3 O 8 , 31 wt% SiO 2 ) at 2 kbar in the presence of aqueous NaCl solutions ranging in concentration from a salt mole fraction (X NaCl ) of 0.1-0.3. The results show that Na preferentially partitions into the silicate liquid, enriching the coexisting fluid in HCl. This hydrolysis effect, known previously for granite melts equilibrated with dilute solutions, therefore also extends to more saline brines. Mineral solubilities depend strongly on salt concentration in the coexisting fluid. Below 5 kbar at 700• C, quartz initially salts in with addition of NaCl to H 2 O, reaches a maximum, and then declines; however, it salts out at all X NaCl at higher P. At granulite-facies P-T conditions, the solubilities of other oxide and silicate minerals (corundum, wollastonite, grossular) salt in and then either reach a plateau or salt out slightly at high X NaCl . In contrast, the solubility of Ca-salt minerals increases exponentially with rising X NaCl . The solubility patterns reflect variations in complexing and H 2 O activity in the brine. Partitioning of REE between rock forming minerals and brines, and between felsic melts and brines, differs strongly from that between minerals, melts and water (±non-polar gas). Brines extract REE f...

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“…Several attempts have been made to infer the nature of synmetamorphic fluids, including thermodyna mic calculations of mineral assemblages and geochemical and isotopic studies of high -grade metamorphic rocks. Among these, detailed investigation of fluid inclusions trapped in various metamorphic minerals provides potential tools in obtaining direct information on the nature and composition of fluids at various stages of metamorphic processes (e.g., Touret, 1985Touret, , 2001Touret, , 2009To-uret et al, 2011;Zheng et al, 2011). The importance of fluids in accretion -collision belts has been investigated in various studies, including geophysical evidence that attest to the presence of fluids and fluid -rock interaction processes (e.g., Naganjaneyulu et al, 2011;Naidu et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Carbonic fluid inclusions in amphibolite-facies pelitic schists from Bodonch area, western Mongolian Altai

Zorigtkhuu

Tsunogae

Dash

2012

Journal of Mineralogical and Petrological Sciences

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We report first fluid inclusion data on amphibolite -facies pelitic schists from Bodonch area of western Mongolian Altai in the Central Asian Orogenic Belt. Three categories of fluid inclusions have been observed in quartz: dominant primary and secondary inclusions, and least dominant pseudosecondary inclusions. The melting temperatures of all the categories of inclusions lie in the narrow range of −57.5 °C to −56.6 °C, close to the triple point of pure CO 2 . Homogenization of fluids occurs into liquid phase at temperature between −33.3 °C to +19.4 °C, which convert into densities in the range of 0.78 g/cm 3 to 1.09 g/cm 3. The estimated CO 2 isochores for primary and pseudosecondary high -density inclusions is broadly consistent with the peak metamorphic condition of the studied area (6.3 -7.3 kbar at 655 °C). The results of this study, together with the primary and pseudosecondary nature of the inclusions, indicate CO 2 was the dominant fluid component during the peak amphibolitefacies metamorphism of the study area. The examined quartz grains are texturally associated with biotite, kyanite and staurolite, which are regarded as high -grade minerals formed during prograde to peak metamorphism. Therefore quartz probably formed by high -grade metamorphism and the primary fluid inclusions trapped in the minerals probably preserve fluids at around peak metamorphism.

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Fluid Regime in Southern Norway: The Record of Fluid Inclusions

Cited by 103 publications

References 24 publications

"Ultrahigh density" carbonic fluids in ultrahigh-temperature crustal metamorphism

"Ultrahigh density" carbonic fluids in ultrahigh-temperature crustal metamorphism

Brines at high pressure and temperature: Thermodynamic, petrologic and geochemical effects

Carbonic fluid inclusions in amphibolite-facies pelitic schists from Bodonch area, western Mongolian Altai

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