Thermodynamic analysis of HP-UHP fluid inclusions: The solute load and chemistry of metamorphic fluids

Maffeis, Andrea; Ferrando, Simona; Connolly, J. A. D.; Groppo, Chiara; Frezzotti, Maria Luce; Castelli, Daniele

doi:10.1016/j.gca.2021.08.044

Cited by 17 publications

(29 citation statements)

References 72 publications

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“…Frezzotti & Ferrando, 2015; Philippot & Selverstone, 1991). MSI are thought to represent a homogeneous solute‐rich supercritical aqueous fluid at entrapment (Ferrando et al, 2005; Frezzotti & Ferrando, 2007; Maffeis et al, 2021; Hermann et al, 2006; Zheng & Hermann, 2014). By contrast, MFI from this study comprise a ubiquitous and constant presence of fluids in the studied rock types (Tables 1 and 2).…”

Section: Discussionmentioning

confidence: 99%

“…Preservation of the original amount of H 2 O in inclusions formed at high P–T conditions is quite rare, together with the general process of selective H 2 O loss from fluid inclusions during exhumation (e.g. Frezzotti et al, 2012; Frezzotti & Ferrando, 2015; Hall & Sterner, 1993; Hidas et al, 2010; Maffeis et al, 2021). Various mechanisms of reequilibration (decrepitation, leakage by nanocracks/dislocations or diffusion) during post‐entrapment evolution of fluid inclusions may simultaneously operate and cannot be observed under optical microscopy (Bakker & Jansen, 1994; Bodnar, 2003; Roedder, 1984; Viti & Frezzotti, 2001; Yamamoto et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…All of these suggest that minerals in the studied MFI are the result of a post-entrapment reaction of the trapped fluid with the host garnet (step-daughter minerals). The possibility of different post-entrapment modifications, local fluid-host mineral interactions and re-equilibration producing stepdaughter crystals during exhumation processes has already been proposed for fluid inclusions in HP metamorphic rocks (Bodnar, 2003;Frezzotti & Ferrando, 2007;Maffeis et al, 2021;Philippot & Selverstone, 1991;Roedder, 1984;Scambelluri & Philippot, 2001;Touret, 1981Touret, , 2001.…”

Section: Origin Of Mfi and Fluid Compositionmentioning

confidence: 98%

“…However, oxygen fugacity and activity of carbon during trapping of the COH fluid along with post-trapping reequilibration and modifications may be potentially a Zheng (2019); contours of the mantle wedge (green for the lithospheric mantle and red-purple for HP tectonic mélange) during exhumation are drawn after Gerya (2019) dominant factor for causing variations on the ratio of residual CO 2 and CH 4 in the inclusions (Hall & Bodnar, 1990). Methane, despite being quite uncommon, together with N 2 and CO 2 has been also identified as a significant constituent of prograde and peak metamorphic fluids in eclogite and granulite facies rocks (Carvalho et al, 2019;Fu et al, 2003;Maffeis et al, 2021;Mukherjee & Sachan, 2009;Tao et al, 2018). Abiogenic production of methane corresponds to reduction of carbonates (as the most abundant carbon-bearing phase in subduction environment) in the slab at HP-HT conditions with water saturation (Tao et al, 2018).…”

Section: Fluid Regime At Hp Subduction Zone Conditionsmentioning

confidence: 99%

“…Philippot & Selverstone, 1991; Scambelluri & Philippot, 2001), (2) multiphase solid inclusions (MSI) representing remnants of supercritical fluids (e.g. Ferrando et al, 2005; Frezzotti & Ferrando, 2007; Maffeis et al, 2021; Ni et al, 2017) and (3) inclusions derived from hydrous melts (e.g. Korsakov & Hermann, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

Spránitz

Padrón‐Navarta

Szabó

et al. 2022

Journal Metamorphic Geology

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Primary multiphase fluid inclusions (MFI) were studied in one eclogite and two granulites from the Cabo Ortegal Complex (COC, NW Spain) by means of Raman imaging, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM‐EDS) and Focused Ion Beam ‐ Scanning Electron Microscopy (FIB)‐SEM. Complementary, secondary MFI in pyroxenites from COC were also investigated. MFI hosted in eclogite and granulites occur along growth zones or in 3D clusters in garnet porphyroblasts suggesting a primary origin at high‐pressure (HP) metamorphic conditions. The mineral assemblage of MFI is mainly composed of Fe‐Mg‐Ca‐carbonates and phyllosilicates ± graphite ± quartz ± corundum ± pyrite ± apatite ± rutile and a fluid phase composed of nitrogen ± methane ± carbon‐dioxide. The mineral proportions vary among the lithologies. Dominant carbonates and hydrous silicates are interpreted as step‐daughter minerals (crystals formed in the MFI after entrapment as a result of fluid–host interaction), whereas apatite, quartz and rutile are considered in part as accidentally trapped minerals since they also occur as crystal inclusions together with MFI in each rock type. Quartz and corundum occur together in MFI in ultramafic granulite and are regarded as step‐daughter minerals in this lithology. These observations suggest that the MFI are products of post‐entrapment reactions of a homogeneous COHN fluid system with the host mineral. Thermodynamic calculations in the CaFMAS‐COHN system confirmed that bulk composition of the MFI in eclogite is similar to the host garnet+COHN composition except for a potential lost of H2O. Carbonation and hydration reaction between the host (i.e. garnet or pyroxene) and the fluid inclusion results in the consumption of all CO2 and part of the H2O from the fluid phase producing Ca‐Fe‐Mg‐carbonates and hydrous step‐daughter minerals, mostly pyrophyllite and chlorite. Nitrogen content of the originally trapped COHN fluid in eclogite was estimated to have a maximum value of 10 mol% at peak HP conditions and 30–40 mol% at retrograde conditions that is within the range of the observed MFI in the residual fluid (13–68 mol%). Pseudosection modelling confirmed the stability of the phase assemblage in the MFI in a specific low‐pressure, low‐temperature stability field (between 300°C and 400°C at pressures < 1 GPa), caused by H2O‐ and CO2‐consuming reactions possibly in a single step. Our findings indicate that such processes in the exhuming HP units may play a role in global nitrogen and carbon cycling as well as potentially contributing to nitrogen and methane supply to subsurface–surface environments during devolatilization in the forearc regions of convergent plate margins.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Origin Of Mfi and Fluid Compositionmentioning

confidence: 98%

Section: Fluid Regime At Hp Subduction Zone Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

Spránitz

Padrón‐Navarta

Szabó

et al. 2022

Journal Metamorphic Geology

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3D Raman mapping combined with FIB‐SEM on multiphase fluid inclusions: A tool to unravel complex phase assemblages

Aradi

Spránitz

Myovela

et al. 2023

J Raman Spectroscopy

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In this study, we performed high resolution 3D Raman mapping on primary multiphase fluid inclusions from a granulite and an eclogite of the Cabo Ortegal Complex (NW Spain), the latter representing a former subduction zone environment. Several microns‐sized inclusions are great targets to test the advantages and limitations of 3D Raman mapping. We show how optical and Raman scattering properties of the phases inside the inclusions can affect the veracity of both 2D and 3D Raman maps. As an independent control, 3D Raman models were compared with focused ion beam‐scanning electron microscopy submicron‐scale slicing of three previously 3D Raman mapped inclusions, allowing us to optimize Raman spectroscopy data evaluation and provide volume proportion calculations. We found that a non‐optimized evaluation procedure might result in even an order of magnitude over‐ or underestimation of phase volume properties. We propose that correcting the Raman maps even with empirically determined Raman cross sections of the phases inside the inclusions can vastly improve the quality of the maps. The results provide valuable input data for thermodynamic modeling and draw implications for fluid/rock interactions.

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Multiphase-solid fluid inclusions in HP-LT eclogite facies rock (Zavkhan Terrane, Western Mongolia): evidence for the evolution from saline to hypersaline fluids during metamorphism in subduction zone

Bayarbold,

Okamoto,

Uno

et al. 2023

Contrib Mineral Petrol

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Fluid inclusions in high- and ultrahigh-pressure metamorphic rocks provide direct information on the composition of the fluids that evolved during metamorphism and fluid-rock interactions in deep subduction zones. We investigate the fluid inclusions in the Khungui eclogite of the Zavkhan Terrane, Central Asian Orogenic Belt. Fluid inclusions are observed in garnet and quartz in the eclogite samples that underwent metamorphism during subduction. The primary fluid inclusions in quartz are composed of liquid and vapor with high salinities (15.7–16.4 wt.% NaCl eq.), whereas the secondary fluid inclusions in quartz are classified as: relatively high salinity (Type I:12.5–16.3 wt.% NaCl eq.) and low salinity (Type II:6.7–10.6 wt.% NaCl eq.). The garnet shows compositional zoning from Ca-poor cores to Ca-rich rims, and the rims that grew during the eclogite-stage metamorphism (2.1–2.2 GPa at 580–610 °C) preferentially contain numerous primary fluid inclusions. The primary fluid inclusions in garnet are commonly bi-phases (liquid and vapor); however, some are multiphase-solid fluid inclusions composed of fluids (liquid and vapor) and combinations of several minerals (halite, quartz, apatite, calcite, biotite, chlorite, and actinolite). Bi-phase fluid inclusions preferentially occur in the inner parts of the Ca-rich garnet rim, whereas multiphase-solid fluid inclusions occur along the margins of the Ca-rich rim. We hypothesize that the multiphase-solid fluid inclusions are formed via interactions between trapped fluids, trapped minerals, and the host garnet during exhumation. By combination of FIB–SEM and synchrotron X-ray CT analyses, the detailed occurrences, volumes, and compositions of the solid phases in the fluid inclusion was analyzed. We then conduct mass balance analysis to reconstruct accurate fluid compositions using data from the FIB–SEM and synchrotron X-ray CT images of the multiphase-solid fluid inclusion. The results of these analyses reveal that (1) fluid changed from an H2O-dominated saline fluid (13–16 wt. % NaCl eq.) at the prograde to the earlier eclogite stage to H2O–CO2-dominated hypersaline fluid at later eclogite stage (~ 32 wt. % NaCl eq., 7.3 wt. % CO2 and ~ 19 molal dissolved cations); (2) a variety of mineral assemblages in multiphase-solid fluid inclusions are produced by post-entrapment reactions between the trapped hypersaline fluid, trapped minerals and the fluid host mineral. The evolution of fluids from saline to hypersaline during the eclogite facies stage is probably caused by the formation of hydrous minerals (i.e., barroisite) under a near-closed system.

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Thermodynamic analysis of HP-UHP fluid inclusions: The solute load and chemistry of metamorphic fluids

Cited by 17 publications

References 72 publications

Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

Abiotic passive nitrogen and methane enrichment during exhumation of subducted rocks: Primary multiphase fluid inclusions in high‐pressure rocks from the Cabo Ortegal Complex, NW Spain

3D Raman mapping combined with FIB‐SEM on multiphase fluid inclusions: A tool to unravel complex phase assemblages

Multiphase-solid fluid inclusions in HP-LT eclogite facies rock (Zavkhan Terrane, Western Mongolia): evidence for the evolution from saline to hypersaline fluids during metamorphism in subduction zone

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