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Micro-Raman spectroscopic analysis allows us to estimate the internal pressure of small fluid inclusions. We applied this method to CO2-dominated fluid inclusions in mantle-derived xenoliths. The pressures estimated from the equilibration temperature and density of the fluid range from 0.96 to 1.04 GPa corresponding to depths of up to 30 km, which...
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... ing the composition to be pure CO 2 , which was con¢rmed by our micro-Raman measurements, an accurate density of CO 2 can be determined by cryogenic microthermometry. The homogeniza- tion temperature at which the CO 2 inclusion of biphase (liquid and vapor) becomes homogenized to a single phase on heating gives the absolute value of density (see Fig. 4 and Table 1). The temperatures ranging from 318.1 ‡C to 349.5 ‡C correspond to the density of CO 2 ranging from 1.03 to 1.14 g/cm 3 . ...
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... As an indicator of CO 2 density, the peak positions of Raman bands of CO 2 have attracted much attention for their usefulness [1][2][3][4][5]. Accurate detection of the peak positions is important for the densimetry because it is a method using the CO 2 density dependence of the wavenumber difference of two main Raman bands of CO 2 . ...
... It is noteworthy that the theoretical expression for the uncertainty of I by Hagiwara et al. [14] suggests that larger I is associated with larger uncertainty of I . However, Eqs. (3) and (4) show that larger I is associated with smaller σ ω . ...
... Improvement in σ is expected to contribute to the development of studies that use small changes in the CO 2 density of natural fluid inclusions (e.g., geobarometric estimation using the CO 2 density [1,2,4,5,35] and that investigate host mineral deformation [39,40]). However, correction with a linear function for the drift on cannot be applied simply for ascertaining the CO 2 density of a natural sample. ...
To evaluate the precision of the wavenumber difference between the two main Raman bands of ${{\rm CO}_2}$ C O 2 (designated as $\Delta$ Δ , an index of ${{\rm CO}_2}$ C O 2 density), we performed theoretical calculations for the uncertainties of the peak positions of the ${{\rm CO}_2}$ C O 2 Raman bands, and measured Raman spectra of ${{\rm CO}_2}$ C O 2 under the conditions used for the calculations. The $\Delta$ Δ precision improves with increased peak intensity, but the peak intensity–precision relation does not hold beyond an intensity threshold corresponding to the measurement time of 1–2 min. Correction for temporal variation of $\Delta$ Δ by fitting a linear function to the data distribution improved the $\Delta$ Δ precision to ${\pm} {0.0005}\;{{\rm cm}^{- 1}}$ ± 0.0005 c m − 1 at best, corresponding to ${{\rm CO}_2}$ C O 2 density precision as ${\pm} {0.00015}\;{{\rm g/cm}^3}$ ± 0.00015 g / c m 3 .
... Carbonic fluids play an important role in many geological processes, such as sedimentary (e.g., Lammers et al., 2015;Ritzi et al., 2016), metamorphic (e.g., Hollister and Burruss, 1976;Touret, 1977;Newton et al., 1980;Yardley and Valley, 1997;Cuney et al., 2007;Scheffer et al., 2017;Roedder, 1984;Andersen and Neumann, 2001;Yamamoto et al., 2002Yamamoto et al., , 2007Berkesi et al., 2009a;Alt et al., 2012), and volcanic and hydrothermal processes (e.g., Giggenbach, 1988Giggenbach, , 1996Charlou et al., 2002;Chiodini et al., 1998). The pressure-density-temperature-composition (P-V-T-x) evolution of carbonic fluid is one of the fundamental problems (Touret, 2016) in understanding the physiochemical conditions of the metamorphic path, hydrothermal activity, oil-gas accumulation, and ore deposit formation (e.g., Yamamoto et al., 2007;Chi et al., 2009;Klein and Fuzikawa, 2010;Huang et al., 2018Huang et al., , 2020. ...
Water-bearing CO2-rich and CH4-rich fluid inclusions are commonly found in various geological environments. Pressure-density-temperature-composition (P-V-T-x) reconstruction of geofluids from such fluid inclusions is fundamental for understanding fluid events related to hydrothermal, metamorphic, and ore-forming processes. Previous methods for P-V-T-x reconstruction of geofluids, such as microthermometry and Raman analysis, often ignore the small amount of water in CO2-rich and CH4-rich fluid inclusions, resulting in obvious errors in composition-density determination, and thus geofluid P-T reconstruction. In the present study, a novel method for P-V-T-x reconstruction of water-bearing binary CO2-rich and CH4-rich geofluids was proposed based on the measurement of the Raman peak positions of water in the vapor phase. Raman spectra of dissolved H2O in vapor-rich CO2/CH4-H2O fluid systems were collected at the P-T range of 10–120 MPa, 100–300 °C, i.e., 0.0091–0.894 of x (H2O) molar fraction, and quantitative models for composition-density calculation of CO2-rich and CH4-rich systems were developed. As the Raman peak positions of dissolved H2O in the CO2/CH4-rich phase are more sensitive in wave number to density changes than the peak positions in previous methods of the CO2 Fermi diad and Csingle bondH stretch mode of CH4 the composition–density calculation using the newly developed Raman calibration models was ten times higher in accuracy. As a demonstration, we determined the composition-density properties of the CO2-rich inclusions in quartz veins collected from the Cape Muroto, Shimanto belt, SW Japan; the P-T field constrained by fluid inclusion indicated the heating effect of the gabbro intrusion event.
... Fluid inclusions have important information for elucidating fluid circulation system in the Earth. Fluid density has been used to estimate the depth at which a host mineral including the fluid had existed (e.g., Roedder and Bodnar, 1980;Yamamoto et al., 2002). Combined information about the depths and isotopic compositions of fluids can inform whereabout and the origin of fluid circulating us in the Earth's interior. ...
We measured the Raman spectra of CO2 fluid at 30 MPa and room temperature (19.1–21.3°C). The spectra showed peaks attributed to the CO2 combining various isotopes such as ¹²C¹⁶O2, ¹³C¹⁶O2, and ¹²C¹⁶O¹⁸O. The relative ratio of ¹²C¹⁶O2 to ¹²C¹⁶O¹⁸O peaks represents the oxygen isotope ratio of CO2. To evaluate the precision of the peak ratios, we measured the CO2 Raman spectra at different exposure times. We examined the standard deviation (1 σ) of the peak intensity ratios and area ones for 20 measurements at each exposure time. The standard deviations of the intensity ratios and area ones were 2.7 and 3.1%, respectively, at a maximum exposure time of 494 s, conversion to peak intensity of ¹²C¹⁶O2 yields about 2,000,000 counts. The uncertainties are 2.5–3 times greater than expected from the noise of a CCD camera and photon statistics. The oxygen isotope ratios (δ¹⁸O) of natural samples have a range of variation of about 16.6%. Compared to that value, the precision we obtained from this study is very small. Raman spectroscopy can be combined with microscopy to analyze areas as small as approx. 1 µm in diameter. Therefore, oxygen isotope measurement using Raman spectroscopy has potential for application to natural samples as a new method for small CO2 fluids such as fluid inclusions.
... Although the two-pyroxene geobarometer of Mercier et al. (1984) and the geobarometer based on the pressure dependence of Ca partition between olivine and clinopyroxene (Köhler and Brey 1990) have been used so far, limitations of accuracy and precision mean they should be used with caution (Laurora et al. 2001;Yamamoto et al. 2014). For that reason, we used a form of geobarometry based on the density of CO 2 fluid inclusions, first proposed by Roedder (1965) and improved and updated by subsequent studies (Miller and Richter 1982;Roedder 1983;Rosso and Bodnar 1995;Seitz et al. 1996;Andersen and Neumann 2001;Yamamoto et al. 2002Yamamoto et al. , 2007Hagiwara et al. 2020Hagiwara et al. , 2021. Since fluid inclusions in a mineral constituting a mantle xenolith should have existed in the mantle before being entrapped by magma, they can be used as a geobarometric probe for the host xenolith if the internal pressure of the fluid inclusions was in equilibrium with surrounding mantle. ...
The lithospheric mantle, formed at the mid-ocean ridge as a residue of crustal production, comprises theoretically depleted peridotite, but more fertile components (e.g., lherzolite and pyroxenite) have been reported, creating an enigmatic picture of the lithosphere. The oceanic lithosphere has also been found to be locally modified by intraplate magmatism as proposed from geochemistry of mantle xenolith. Petit-spot xenoliths are particularly notable as direct evidence of old lithospheric mantle and expected to retain essential information about oceanic lithosphere prior to its subduction. In this study, we report on the lithological structure of Pacific lithosphere aged at 160 Ma, just subducting into Mariana Trench, based on petrology and chemistry of ultramafic xenoliths from a petit-spot knoll and then, we suggest the occurrence of petit-spot melt infiltration resulting in mantle metasomatism and formation of pyroxene-rich vein.
Our petit-spot ultramafic xenoliths can be divided into three main types: a depleted peridotite as a residue of crust production, an enriched peridotite, and fertile pyroxenites as the product of melt-rock interactions prior to entrapment. Geothermobarometry also suggests that the depleted peridotite was derived from the uppermost lithospheric mantle, whereas the enriched peridotite and Al-augite pyroxenites were obtained from deeper layers of the lithosphere. Moreover, thermal gradient of the lithosphere estimated from these data is considerably hotter than pristine geotherm estimated on the basis of plate age. Hence, we could illustrate that the oldest portion of the Pacific lithosphere (160 Ma), which was not observed before, was locally fertilized and heated by prior multiple petit-spot magmatic events, and pyroxene-rich metasomatic veins penetrated from the base to the middle/upper lithosphere. Such local lithospheric fertilization is plausible at the plate-bending field, and the nature of Pacific Plate subducting into Mariana Trench may be partly different from what has been assumed so far.
... It proposed that 544 localization of plastic deformation occurs in rheologically weaker zones during mantle upwelling 545 decompression under a dislocation creep regime. Because olivine is the softest phase of upper 546 mantle rocks (Nicolas et al. 1971;Carter 1976;Yamamoto et al. 2002Yamamoto et al. , 2008Karato 2008), the 547 solid state flow is more intense in dunite in comparison with peridotite, thus, the redistribution of 548 mineral phases in dunite is more efficient. 549 ...
The paper describes disseminated tabular, podiform massive, and transitional chromitite deposits from a mantle section of the Kraka ophiolite massif, South Urals, Russia. The chromitite is hosted by dunite with no correlation between their size and quality and the size of the dunite bodies. Thick dunite bodies mostly host disseminated fine-grained banded chromitite; massive ores are composed of coarse-grained chromitite typically with a thin dunite envelope. The chromitite and host ultramafic rocks exhibit plastic deformation of silicates and chromite, which is expressed in microstructural features, preferred orientation of rock-forming olivine, and folding of the chromitite bodies. The ultramafic rocks are also characterized by deformation-induced textures leading to the formation of the small-size chromite grains on structural defects of plastically deformed rock-forming olivine and orthopyroxene. The formation of dunite bodies and associated chromitite is related to the localization of deformation of rising mantle flows under decompression conditions. Dunite was the most rheologically weak zone exhibiting a focused solid state flow and effective separation of mineral phases (olivine and chromite). The higher amount of the latter in dunite is a result of deformation-induced breakdown of enstatite and removal of trace elements from olivine. The structural features of massive chromitite aggregates indicate that they are a product of concentration and aggregation of grains under the influence of tectonic stresses at high temperatures and pressures, similar to pressure sintering.
... The Raman spectra of the CO 2 -rich fluid inclusions in rutile display two main peaks at 1279 cm −1 (ν − ) and 1385 cm −1 (ν + ). The difference between these wave numbers has been shown to be a function of density and pressure (Wang et al., 2011;Yamamoto et al., 2002). The calculated densities are 1.23 g/cm 3 using the equation of Yamamoto et al. (2002) and 1.03 g/cm 3 after Wang et al. (2011). ...
... The difference between these wave numbers has been shown to be a function of density and pressure (Wang et al., 2011;Yamamoto et al., 2002). The calculated densities are 1.23 g/cm 3 using the equation of Yamamoto et al. (2002) and 1.03 g/cm 3 after Wang et al. (2011). These values correspond well with the previously reported CO 2 densities for CO 2 ± CH 4 ± N 2 ± H 2 O liq fluid inclusions in kyanite, garnet, zircon, and quartz from UHP Kokchetav rocks (e.g. ...
... The internal pressure values estimated by the CO 2 PT phase diagram for the range of temperatures from 830 to 920°C are 0.7-1.2 GPa (Yamamoto et al., 2002). Numerous experimental studies suggested a supercritical CO 2 fluid (COH fluid) as being a favorable environment for diamond nucleation (e.g. ...
This study highlights the usefulness of rutile when applied for reconstruction of the metamorphic evolution of ultrahigh-pressure rocks containing diamond. Within the diamondiferous kyanite gneiss (Kokchetav massif, Northern Kazakhstan), rutile shows three distinct textural positions: (i) rounded/irregular-shaped grains in the rock matrix; (ii) monomineralic inclusions in garnet, kyanite, quartz, and zircon; and (iii) grains in polyphase inclusions within garnet and kyanite porphyroblasts. High Nb (1990–3197 ppm) and relatively low Cr (404–703 ppm) concentrations in rutile indicate its metapelitic derivation. The Zr content in rutile varies from 480 to 798 ppm and the average temperature estimates yielded by the Zr-in-rutile geothermometer for 5 GPa are 880 °C. Rutile-hosted Zn-rich (up to 1.74 wt% ZnO) staurolite is interpreted as a record of the prograde metamorphic stage formed as a result of gahnite+pyrophyllite+diaspore breakdown at 0.3–0.8 GPa, 400–450 °C. Inclusions of diamond±CO2 ± carbonate±garnet in rutile originated near the peak of metamorphism (~5 GPa and ~ 880 °C). U-Pb ID-TIMS dating of a representative rutile separate yielded a concordant age of 519 ± 1.6 Ma that is younger than the previously estimated U-Pb crystallization ages of the peak metamorphic assemblages of the Kokchetav massif (528 ± 3 Ma). The obtained age represents the timing of cooling to the closure temperature for Pb diffusion in rutile (Tc; 420–640 °C). The cooling of the rocks from the peak temperatures to Tc occurred with the rates of 27–51 °C/Ma, whereas the exhumation rates (from 880 °C and 5 GPa to 420–640 °C and 0.5–1 GPa) were 1.3–1.5 cm/year. The peak temperature estimates as well as rapid cooling and exhumation rates reported here are in agreement with published data on zircon from similar diamondiferous Kokchetav gneisses. This work demonstrates that rutile provides a beneficial tool in studies dealing with reconstruction of the metamorphic evolution of diamondiferous rocks.
... In contrast, an 1800 grooves/mm grating (spectral resolution of approximately ±0.5 cm − 1 ) was used to determine the Fermi diad spacing between the v 1 and v 2 Raman peaks of CO 2 . The spacing between v 1 and v 2 CO 2 peaks was used to determine the density of CO 2 in the fluid inclusion vapor phases (e.g., Rosso and Bodnar, 1995;Yamamoto et al., 2002;Yamamoto and Kagi, 2006;Fall et al., 2011;Wang et al., 2011). Elemental silicon was used as a frequency calibration standard. ...
Disseminated Au deposits hosted in metasedimentary rocks present unique exploration challenges because the Au is generally very fine-grained or refractory, and not vein-hosted. Exploration programs in such settings rely on extensive lithogeochemical surveys, lesser structural analysis, and little emphasis on ore-fluid geochemistry. The Moose River anticline (MRA) in the Lower Paleozoic Meguma terrane (Nova Scotia, Canada) hosts several high-tonnage (~10–20 Mt), low-grade (≤1–4 g/t Au) Au deposits comprised of disseminated ± quartz vein-hosted mineralization in metamudstones. Here, the Touquoy deposit is used to evaluate a new approach to geochemical exploration by examining if the volatile chemistry of host rocks preserves a signature related to Au mineralization, using a gas chromatographic (GC) technique that analyzes bulk volatiles released from crushed rock. Since GC is a bulk analytical technique, (i.e., multiple generations of fluid inclusion volatiles yielding a mixed analytical volume), the volatile composition of fluid inclusions were also investigated using laser Raman microspectroscopy to reconcile bulk analyses with the composition and abundance of different inclusion types. Inclusions in quartz pressure shadows associated with porphyroblasts host N2 ± CH4-dominant vapor phases and represent wall rock-equilibrated fluids. In comparison, fluid inclusion vapor phases in quartz veinlets crosscutting the metamudstones are more complex in composition and show a continuum between CO2-dominant and N2 ± CH4-dominant compositions; the former is interpreted as the fluid responsible for Au mineralization in the Meguma terrane (e.g., H2O-CO2 ± CH4 ± N2 fluids). GC shows statistically significant differences between the bulk volatiles released from crushed metamudstones from the Touquoy deposit (n = 21) and barren (n = 24) settings. Whereas the former commonly contain detectable CO2 (50% of samples; LOQ(CO2) ~ 10⁻¹⁰ mol/g), only ~4% of metamudstones from barren settings along the MRA contain CO2, yielding a t-test p-value of 0.0103 between the two sample populations. Whereas the more frequent detection of CO2 in mineralized samples is related to increasing carbonate alteration proximal to Au mineralization, no correlation is observed between bulk CO2 abundance and Au grade. Additionally, anomalous differences in abundances of released C3 (t-test p-value = 0.043) and C4 (t-test p-value = 0.03) hydrocarbons (HC) are recognized between the two populations (LOQ(HC) ca. 10⁻¹³ to 10⁻¹² mol/g), with Touquoy metamudstones having higher Σ(C3)/CH4 and Σ(C4)/CH4 ratios compared to barren equivalents. The compositional differences suggest that more aqueous‑carbonic fluids infiltrated metamudstone units where locally favorable physical and/or chemical conditions are present, resulting in increased Au endowment. The relative increase in fluid flux, and thus Au grade, resulted in more trapped CO2 (i.e., resulting from more trapped inclusions and/or greater CO2 fluid component) and modification to hydrocarbon signatures through homologation and/or degradation reactions. Rigorous sample preparation ensures these compositional differences are related to paleofluids and not contamination.
Tentatively, the results suggest that bulk analysis of volatiles released from fluid inclusions in metamudstones may be a useful vectoring tool for disseminated Au mineralization in Meguma-type gold systems and similar environments (e.g., Carlin-type). This technique may be appropriately scaled to complement exploration drilling programs and may be more sensitive in determining ore proximity than often ambiguous pathfinder elements.
... The density of the fluid inclusions (ρ) was estimated from their peak positions. To ascertain the density of CO 2 -rich fluid inclusion, several groups have improved Raman CO 2 densimeters and have demonstrated the density dependence of distance of Fermi diad splits (Δ = ν F. D. (Fig. S1) (Rosso and Bodnar, 1995;Yamamoto et al., 2002;Kawakami et al., 2003;Yamamoto and Kagi, 2006;Song et al., 2009;Fall et al., 2011;Wang et al., 2011;Lamadrid et al., 2017;Yuan et al., 2017;Wang et al., 2019;Hagiwara et al., 2020;Le et al., 2020;Sublett et al., 2020). ...
Raman spectroscopy for fluid, melt, and mineral inclusions provides direct insight into the physicochemical conditions of the environment surrounding the host mineral at the time of trapping. However, the obtained Raman spectral characteristics such as peak position are modified because of local temperature enhancement of the inclusions by the excitation laser, which might engender systematic errors and incorrect conclusions if the effect is not corrected. Despite the potentially non-negligible effects of laser heating, the laser heating coefficient (B) (°C/mW) of inclusions has remained unsolved. For this study, we found B from experiments and heat transport simulation to evaluate how various parameters such as experimental conditions, mineral properties, and inclusion geometry affect B of inclusions. To assess the parameters influencing laser heating, we measured B of a total of 19 CO2-rich fluid inclusions hosted in olivine, orthopyroxene, clinopyroxene, spinel, and quartz. Our results revealed that the measured B of fluid inclusions in spinel is highest (approx. 6 °C/mW) and that of quartz is lowest (approx. 1 × 10−2 °C/mW), consistent with earlier inferences. Our simulation results show that the absorption coefficient of the host mineral is correlated linearly with B. It is the most influential parameter when the absorption coefficient of the host mineral (αh) is larger than that of an inclusion (αinc). Furthermore, although our results indicate that both the inclusion size and depth have little effect on B if αh > αinc, the thickness and radius of the host mineral slightly influence B. These results suggest that the choice of inclusion size and depth to be analyzed in a given sample do not cause any systematic error in the Raman data because of laser heating, but the host radius and thickness, which can be adjusted to some degree at the time of sample preparation, can cause systematic errors between samples.
Our results demonstrate that, even with laser power of 10 mW, which is typical for inclusion analysis, the inclusion temperature rises to tens or hundreds of degrees during the analysis, depending especially on the host mineral geometry and optical properties. Therefore, correction of the heating effects will be necessary to obtain reliable data from Raman spectroscopic analysis of inclusions. This paper presents some correction methods for non-negligible effects of laser heating.
... Other limitations of microthermometry also appear when analyzing FIs of small size (<~5 μm), of low density, and of even more complex composition without any observable phase transition (Rosso and Bodnar, 1995;Burke, 2001;Yamamoto et al., 2002;Kawakami et al., 2003;Yamamoto et al., 2007;Song et al., 2009). ...
The P-V-X properties of two-component fluid inclusions (FIs) are generally determined from microthermometry data using appropriate thermodynamic models (i.e., VX diagrams) and/or equations of state (EoS). However, some limitations can hamper the applicability of this technique such as the small size, low density or complex composition of the analyzed FI. Raman spectroscopy is known as the best-suited alternative method to microthermometry for the investigation of natural FIs because it can provide simultaneously non-destructive qualitative and possible quantitative analyses after specific calibrations. The present work aims to provide calibration data to directly determine the P-V-X properties of binary or ternary mixtures of CH4, CO2, and N2. The variation of spectral features as a function of composition and pressure (or density) was investigated by using Raman spectroscopy coupled with an improved High-Pressure Optical Cell (HPOC) system and a customized heating-cooling stage. From our experimental data, the relative Raman scattering cross-section (RRSCS) of CH4 (νCH4∗) was demonstrated to be constant at 7.73 ± 0.16 over the investigated range of pressure (5–600 bars) and for any composition. This parameter can thus be used for the determination of composition with an uncertainty of ~0.5 mol%. Several calibration equations were calculated for different PX domains, linking the Fermi diad splitting of CO2 (Δ) or the relative variation of the CH4 peak position (νCH4∗) to the pressure (or density) and composition of CO2-CH4, CH4-N2, and CO2-N2-CH4 mixtures at 22 and 32 °C. The pressure and density of the fluids can henceforth be directly measured from Raman spectra with an uncertainty of ~20 bars and ~0.01 g·cm⁻³, respectively. Our calibration equations were then validated on natural FIs by comparing the results obtained from Raman and microthermometry. We also interpreted the variation of the peak position of CH4 based on the change of intermolecular interaction. Finally, we discussed the applicability of the obtained calibration data into another laboratory by comparing it with the data of pure CO2 and CH4 published in literature. A small shift between calibration curves implies a systematic error which is perhaps due to the difference in the configuration or the day-to-day deviation of the instruments. Therefore, standards of well-known P-V-X properties should be regularly measured to prevent and to correct any variation or shifting of the instrumental responses.
... Based on the fluid-inclusion geobarometry and two-pyroxene geothermometry, pressure and temperatures recorded in peridotite xenoliths from a region (Ennokentiev) of Far Eastern Russia were found as 0.89-1.12 GPa and 912-1022 • C, respectively (Kobayashi et al., 2012;Yamamoto et al., 2002;2012). Assuming that the P-T information is representative of the geotherm in Far Eastern Russia, the equilibrium temperatures of Sv-1 (952 ± 56 • C, Yamamoto et al., 2009a) and Sv1-36 (931 ± 29 • C, Yamamoto, 2001) correspond to 0.96-1.05 ...
