Characterisation of amphibolite-facies fluids of Variscan eclogites from the Orlica-Snieznik dome (Sudetes, SW Poland)

Klemd, Reiner; Bröckr, Michael; Schramm, Julian

doi:10.1016/0009-2541(94)00096-q

Cited by 49 publications

(24 citation statements)

References 19 publications

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“…P-T conditions are only well constrained for eclogites and granulites. For these rocks, estimated peak pressures lie in the coesite stability field with pressures in excess of 27 kbar at temperatures of 700-800°C (for eclogites) and 800-1,000°C (for granulites; Bakun-Czubarow 1991a, 1991bKlemd et al 1995;Bröcker and Klemd 1996;Kryza et al 1996;Klemd and Bröcker 1999). The peak-pressure conditions for the Gierałtów gneisses reached eclogite-facies conditions (Bröcker and Klemd 1996).…”

Section: Geological Backgroundmentioning

confidence: 95%

Geochemistry and Rb–Sr geochronology of a ductile shear zone in the Orlica-Śnieżnik dome (West Sudetes, Poland)

Lange

Bröcker

Mezger

et al. 2002

Int J Earth Sci (Geol Rundsch)

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Amphibolite-facies orthogneisses of the OrlicaŚnieżnik dome in the West Sudetes (Poland) show a local continuous transition from weakly deformed augen gneisses to finely laminated mylonites. Field evidence indicates that ductile shearing developed pre-or syntectonically to a migmatization event. Bulk-rock compositions of variably deformed samples yield no indications for deformation-and/or fluid-enhanced element mobility and redistribution. 87 Rb-86 Sr geochronology (biotite, phengite, whole rock) places time constraints on the deformation process and the post-orogenic cooling history. Phengiteand biotite-whole-rock pairs yield Rb-Sr ages of 340 to 334 Ma and 335 to 294 Ma, respectively, independent of the degree of deformation. The weighted mean of phengite-whole-rock pairs indicates an age of 337.4±2.3 Ma. Combining most of the biotite-whole-rock data yields a weighted mean age of 328.6±4.4 Ma. Because of their different closure temperatures for the Rb-Sr system, these differences are interpreted to date cooling after a thermal event. Direct dating of the deformation is not possible, but the cooling history record defines a minimum age for the development of ductile shearing and the last migmatization event. These time constraints provide evidence for the initiation of crustal collapse during or immediately following peak metamorphic conditions. The results of this study further document the importance of Variscan metamorphism in the Orlica-Śnieżnik dome.

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Section: Geological Backgroundmentioning

confidence: 95%

Geochemistry and Rb–Sr geochronology of a ductile shear zone in the Orlica-Śnieżnik dome (West Sudetes, Poland)

Lange

Bröcker

Mezger

et al. 2002

Int J Earth Sci (Geol Rundsch)

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“…Although this apparently reflect the trapping of fluids from a single fluid infiltration event, some inclusions in the sample display considerably lower T h (as low as −31.7°C ) compared to other inclusions, probably reflecting that these low T h inclusions underwent slight fluid leakage during decompression and/or later tectonic event, and formed high T h inclusions. However, we cannot neglect the possibility of volume increase to form low T h (i.e., high density) carbonic fluids that have been pointed out for fluid inclusions in eclogites by Klemd et al (1995). The T h of fluid inclusions in sample AB26 3 also exhibits a narrow distribution (+15 ± 5°C), with presence of rare low T h inclusions.…”

Section: Microthermometrymentioning

confidence: 91%

Fluid inclusions study of Abukuma metamorphic rocks from the Hanazono district, northeast Japan

Ohyama

Tsunogae

2007

Journal of Mineralogical and Petrological Sciences

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A systematic fluid inclusion study on pelitic and granitic gneisses of the Cretaceous Abukuma metamorphic rocks, exposed in the Hanazono district, northeast Japan, identified three categories of fluid inclusions: primary aqueous inclusions in porphyroblastic garnet, primary to pseudosecondary carbonic inclusions in quartz, and secondary aqueous inclusions in quartz. The primary aqueous inclusions in garnet exhibit melting and homogenization temperatures of −2.5 to −0.3 °C and +168.2 to +360.0 °C, respectively. The dominant primary to pseudosecondary fluid inclusions in undeformed quartz display melting temperatures of −64.2 to −56.6 °C, indicating a CO 2 rich composition with additional CH 4 and/or N 2 . The carbonic inclusions can be divided into high density (1.121 1.153 g/cm 3 ) and medium density (0.683 1.111 g/cm 3 ) types. The fluid densities of the latter inclusions, when translated into isochores, indicate entrapment of CO 2 at the peak P T conditions experienced by rocks in the study area (2.8 5.2 kbar at 770 850 °C). In contrast, the isochores of high density category in quartz and aqueous inclusions in garnet do not intersect the expected P T trajectory, yet are consistent with the prograde high pressure condition of the Abukuma metamorphic rocks in the Takanuki district (8 10 kbar at 700 750 °C). Isochores calculated for carbonic inclusions in granitic gneiss intersect the P T path at 2 3 kbar at 650 °C, suggesting that the fluids were captured during the retrograde stage. It is inferred that H 2 O was the dominant fluid species during the prograde stage, while CO 2 was more abundant during the peak to retrograde stages of the Abukuma metamorphic belt. The prograde H 2 O bearing fluid was probably derived from the break down of hydrous minerals. Although the origin of carbonic fluid is not known, the presence of CO 2 rich fluid during peak metamorphism probably lowers the H 2 O activity in the rocks. The isochores computed for secondary aqueous inclusions in quartz give very low P T conditions (300 °C and 1.7 3.5 kbar), suggesting that the fluids are of retrograde origin.

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“…Local fluid production and/or buffering was suggested with only short-distance fluid transport. Analogous features were described from eclogites of the Orlica-Sniezik dome, Poland (Klemd et al 1995), even though fluid inclusions consisting of brine and CO 2 ±N 2 ±CH 4 inclusions were reset during uplift at amphibolite facies conditions and immiscibility at eclogite facies was therefore not explicitly proven. Andersen et al (1993) reported CO 2 -N 2 fluid inclusions occurring with conjugate brines (30 wt% NaCl) from eclogite of the Norwegian Caledonides representing immiscible fluids at peak metamorphic conditions.…”

mentioning

confidence: 87%

Fluid Immiscibility in Metamorphic Rocks

Heinrich

2007

Reviews in Mineralogy and Geochemistry

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INTRODUCTIONEvidence of fluid immiscibility in metamorphic rocks comes, in the best of all worlds, from fluid inclusion observations. In fact, fluid immiscibility should be anticipated over the full range of metamorphic conditions provided that appropriate bulk fluid compositions are present. In a review paper on "Metamorphic fluids: the evidence from fluid inclusions" Crawford and Hollister (1986) summarized: "The role of fluid immiscibility in metamorphism was only recognized after serious study of fluid inclusions in metamorphic rocks was underway in the late 1970s and has yet to attract the attention of more than a handful of petrologists studying metamorphic rocks." Since then, tremendous progress has been made. A huge amount of fluid inclusion studies have convincingly shown that immiscible fluids can be present in rocks of all bulk compositions and at all P-T conditions. Thermodynamic databases of minerals, solid solutions and fluid mixtures along with the development of Gibbs free energy minimization programs now allow for detailed prediction of the evolution of phase assemblages and mineral compositions in P-T space. Significant progress has also been made in understanding reaction kinetics, diffusional and convective mass transport and the interpretation of fluid-rock interaction during metamorphism. Given the vast fluid inclusion evidence of immiscibility it would appear, however, that phase petrology and mass transport in any specific rock where fluids are involved are not correctly interpreted if possible or proven immiscibility is not considered. Relatively few studies directly link mineral reactions with immiscible fluids. Therefore, this review aims at working out the effects of fluid immiscibility on the progress of metamorphic reactions and fluid transport over a wide range of conditions.Questions arise directly from the fluid inclusion record in metamorphic rocks. This chapter, however, is organized the other way round. At first it summarizes phase relations of fluid systems pertinent to metamorphic rocks obtained by laboratory experiments and thermodynamic calculations. It then addresses how calculated mineral 2 reactions are affected by immiscible fluid systems, and how immiscible fluids are produced and evolved when metamorphic mineral reactions proceed. The impure limestone plus H 2 O-CO 2 -salt system is theoretically explored, for which by far the most information is available and which may stand for other fluid-rock systems. A section on the physical behavior of immiscible fluids follows, again mainly based on experimental results. The second part of the paper reviews numerous field examples of contact, regional, and subduction related metamorphic rocks where fluid immiscibility played a significant role during petrogenesis and mass transport. Late events in metamorphic rocks such as formation of hydrothermal systems, late vein formation, ore deposits, etc. where fluid immiscibility and fluid segregation is of paramount importance are not explicitly addressed here. Instead, the review ...

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Characterisation of amphibolite-facies fluids of Variscan eclogites from the Orlica-Snieznik dome (Sudetes, SW Poland)

Cited by 49 publications

References 19 publications

Geochemistry and Rb–Sr geochronology of a ductile shear zone in the Orlica-Śnieżnik dome (West Sudetes, Poland)

Geochemistry and Rb–Sr geochronology of a ductile shear zone in the Orlica-Śnieżnik dome (West Sudetes, Poland)

Fluid inclusions study of Abukuma metamorphic rocks from the Hanazono district, northeast Japan

Fluid Immiscibility in Metamorphic Rocks

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