Multiphase solid inclusions reveal the origin and fate of carbonate-silicate melts in metasomatised peridotite

Kotková, Jana; Čopjaková, Renata; Škoda, Radek

doi:10.1016/j.lithos.2021.106309

Cited by 6 publications

(27 citation statements)

References 68 publications

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“…Using thermodynamic modelling or thermobarometry, the maximum P-T conditions were estimated to be 11-25 kbar and 750-1200 °C for the felsic granulites, 16-25 kbar and 1050-1200 (Gayk et al 1995;Štípská and Powell 2005;Medaris et al 2006;Racek et al 2006Racek et al , 2008. The occurrence of microdiamond and coesite inclusions in the felsic granulites shows that at least some of these granulites underwent metamorphism under UHP conditions of 850-1100 °C and ~45 kbar (Kotková et al, 2021;Kotková et al, 2011;Perraki and Faryad, 2014). For garnet peridotites, peak metamorphic conditions of 20-60 kbar and 900-1400°C were estimated (Carswell 1991;Medaris et al 2005;Schmädicke et al 2010).…”

Section: Geological Settingmentioning

confidence: 99%

“…In mantle lithologies, Ba(-Cl)-rich micas and other Ba(-Cl)-rich phases are rare, but they are known from the matrix of garnet peridotite (Tumiati et al 2007). These phases specifically occur within multiphase solid inclusions, henceforth referred to as MSI, in garnet or spinel from (U)HP garnet pyroxenites, eclogites, peridotites, and chromitites (Zaccarini et al 2004;Faryad et al 2010;Borghini et al 2018Borghini et al , 2020Čopjaková and Kotková 2018;Naemura et al 2018;Kotková et al 2021).…”

Section: Introduction Occurrence and Origin Of Ba-(cl-) Bearing Micasmentioning

confidence: 99%

“…http://www.minsocam.org/ LILE and Cl-rich, sometimes potassic carbonatitic fluids or melts derived from a subducting crustal slab (Faryad et al 2013, Naemura et al 2018. Furthermore, the metasomatizing agent may be enriched in Mg, Fe, Al, and Cr derived from rocks in the mantle wedge (Tumiati et al 2007;Naemura et al 2009Naemura et al , 2018Borghini et al 2018Borghini et al , 2020Čopjaková and Kotková 2018;Kotková et al 2021).…”

Section: Introduction Occurrence and Origin Of Ba-(cl-) Bearing Micasmentioning

confidence: 99%

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Compositional trends in Ba-, Ti-, and Cl-rich micas from metasomatized mantle rocks of the Gföhl Unit, Bohemian Massif, Austria

Zelinková,

Racek,

Abart

2023

American Mineralogist

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Ba-, Ti-, and Cl-rich micas associated with other Ba-and/or Cl-rich minerals in the rock matrix or in garnet and clinopyroxene hosted multiphase solid inclusions (MSI) are observed in mantle-derived garnet pyroxenites. The micas show extremely high variability in chemical composition ranging between Ba-rich phlogopite, chloroferrokinoshitalite, and oxykinoshitalite. Elemental covariation trends in mineral chemical data reveal the principal substitution mechanisms responsible for the observed chemical variability. The substitution Ba 2+ Al 3+ ↔K 1+ Si 4+ associated with either OH 1-↔Cl 1or Ti 4+ 2O 2-↔Mg 2+ 2OH 1 links phlogopite to chloroferrokinoshitalite and oxykinoshitalite, respectively, whereas the substitution2Cl 1links chloroferrokinoshitalite to oxykinoshitalite. The preferred incorporation of Cl in Fe-rich mica and of Ti+O in Mg-rich mica indicates that XFe (Fe tot /Fe tot +Mg) exerts an important control on mica composition. The positive correlation of XFe with Cl led to the formation of possibly the most Clrich mica so far described classified as chloroferrokinoshitalite(XFe 0.88 , Ba 0.95 K 0.03 Fe 2.68 Mg 0.37 Al 1.91 Si 2.01 Cl 1.98 ) with 10.98 wt% Cl. Substantial substitution of OHby Cland This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America. The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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Section: Geological Settingmentioning

confidence: 99%

Section: Introduction Occurrence and Origin Of Ba-(cl-) Bearing Micasmentioning

confidence: 99%

Section: Introduction Occurrence and Origin Of Ba-(cl-) Bearing Micasmentioning

confidence: 99%

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Compositional trends in Ba-, Ti-, and Cl-rich micas from metasomatized mantle rocks of the Gföhl Unit, Bohemian Massif, Austria

Zelinková,

Racek,

Abart

2023

American Mineralogist

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“…Recently, Čopjaková and Kotková (2018) and Kotková et al (2021) have described the presence of MSI in garnets of subduction-related samples, represented by ultra-high pressure (UHP) peridotites of the Bohemian Massif. These peridotites equilibrated at peak pressures of c. 4 GPa (Medaris et al 2015), and are interpreted as part of the mantle lithospheric wedge during the Variscan subduction and collision of northern Gondwana underneath Laurasia (Medaris et al 2005(Medaris et al , 2015.…”

Section: Introductionmentioning

confidence: 99%

“…These peridotites equilibrated at peak pressures of c. 4 GPa (Medaris et al 2015), and are interpreted as part of the mantle lithospheric wedge during the Variscan subduction and collision of northern Gondwana underneath Laurasia (Medaris et al 2005(Medaris et al , 2015. Kotková et al (2021) have approached the composition of the trapped fluids from mass balance, using detailed (FEG-SEM BSE) twodimensional (2D) modal analysis of the MSI combined with EPMA analysis of their minerals. They conclude that the MSI represent carbonate-silicate liquids produced after: (i) partial UHP crystallization of an intruding parental carbonate-silicate melt that formed garnet pyroxenite veins in the host peridotites; and (ii) later migration through, and interaction of the residual liquid with the host peridotites, producing their metasomatism.…”

Section: Introductionmentioning

confidence: 99%

Experimental constraints on the nature of multiphase solid inclusions and their bearing on mantle wedge metasomatism, Bohemian Massif

Acosta-Vigil,

Kotková,

Čopjaková

et al. 2024

Contrib Mineral Petrol

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This study tests experimentally the hypothesis that calculated bulk compositions of multiphase solid inclusions present in minerals of ultrahigh pressure rocks, can be equated to the composition of the former trapped fluids. We investigated samples from the ultrahigh pressure garnet peridotites of the Bohemian Massif, spatially associated with ultrahigh pressure crustal rocks and representing a former subduction interface environment. Inclusions present in garnets, composed of amphibole + Ba-mica kinoshitalite + carbonates (dolomite + magnesite + norsethite), were taken to their entrapment conditions of c. 4.5 GPa and 1075 ºC. They (re)crystallized into a garnet fringe at the boundary between inclusion and host garnet, kinoshitalite ± olivine, carbonatite melt, and a hydrous fluid. Although the latter may have exsolved from the carbonatite melt upon quenching, microstructures suggest it was present at trapped conditions, and mass balance indicates that it corresponds to a Na-K-Cl-F-rich saline aqueous fluid (brine). Experiments demonstrate the stability of kinoshitalite at 4.5 GPa and 1075 ºC, and suggest that Ba-rich mica + carbonatite melt + brine coexisted at near-peak conditions. Barium is compatible in the carbonatite melt and mica with respect to the brine, with a partition coefficient between carbonatite melt and mica of ≈ 2.5–3. The garnet fringe formed from incongruent reaction of the former inclusion assemblage due to reversing the fluid(s)-host garnet reaction that occurred upon natural cooling/decompression. Loss of H2 or H2O from the inclusions due to volume diffusion through garnet and/or decrepitation, during geological timeframes upon decompression/cooling, may have prevented rehomogenization to a single homogeneous fluid. Our study shows that great care is needed in the interpretation of multiphase solid inclusions present in ultrahigh pressure rocks.

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Crystallisation of trapped carbonate–silicate melts terminating at the carbonated solidus ledge: a record of carbon immobilisation mechanism in the lithospheric mantle

Haifler,

Kotková,

Čopjaková

2024

Contrib Mineral Petrol

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Orogenic peridotites in the crystalline basement of the northwestern Bohemian Massif contain multiphase solid inclusions (MSI), which are interpreted to be crystallisation products of trapped former carbonate–silicate melts metasomatizing their host rocks. We applied conventional thermobarometry and forward thermodynamic modelling to constrain the P–T evolution ranging from the peak metamorphic conditions of the investigated harzburgite and lherzolite, through entrapment of the melts in the outer parts of garnets, to the (re)-equilibration of the MSI assemblages. The peak conditions of c. 1100 °C/4.5–5.5 GPa are recorded by garnet cores and large pyroxene porphyroclasts. The melt entrapment, during which garnet outer parts grew, was associated with influx of the metasomatizing liquids and probably took place during the early stage of the exhumation. Thermodynamic model of amphibole-free MSI assemblage comprising kinoshitalite/Ba-rich phlogopite (approximated by phlogopite in the model), dolomite, magnesite, clinopyroxene, orthopyroxene, garnet and chromite provided robust estimate of P and T of its (re)-equilibration, c. 900–1000 °C, 1.8–2.2 GPa. Furthermore, the lack of olivine reflects co-existence of COH fluid with high X(CO2) = CO2/(CO2 + H2O) ≥ 0.6. Models employing identical P–T–X(CO2) parameters successfully reproduced the other two amphibole-bearing assemblages observed. The modelled stability fields show perfect alignment with a characteristic isobaric segment of the solidus curve of carbonated peridotite. This co-incidence implies that the (re)-equilibration corresponds to the termination of the melt crystallisation once the near-isothermal exhumation path intersected the solidus. Decreased solubility of silicates at the carbonated peridotite “solidus ledge”, inferred from the published experimental data, as well as concentric textures of some MSI indicates sequential crystallisation from the early silicates to late dolomite. The carbonated “solidus ledge” is a relatively narrow boundary in the lithospheric mantle capable of an abrupt immobilisation of fluxing or transported carbonated melts. The investigated rocks are estimated to store approximately 0.02 kg C/m3 (or 6 ppm C) occurring as carbonates in the MSI.

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Multiphase solid inclusions reveal the origin and fate of carbonate-silicate melts in metasomatised peridotite

Cited by 6 publications

References 68 publications

Compositional trends in Ba-, Ti-, and Cl-rich micas from metasomatized mantle rocks of the Gföhl Unit, Bohemian Massif, Austria

Compositional trends in Ba-, Ti-, and Cl-rich micas from metasomatized mantle rocks of the Gföhl Unit, Bohemian Massif, Austria

Experimental constraints on the nature of multiphase solid inclusions and their bearing on mantle wedge metasomatism, Bohemian Massif

Crystallisation of trapped carbonate–silicate melts terminating at the carbonated solidus ledge: a record of carbon immobilisation mechanism in the lithospheric mantle

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