Fluid Carbon Research Articles

Late beryllium enrichment during dynamic growth of vesuvianite and scapolite from the Cuonadong Sn-W-Be skarn, Tibet

The genesis of beryllium (Be) mineralization associated with granitic tin (Sn)- tungsten (W) deposit has received little attention, especially the fluid Be concentration variation along with the developing of skarn. For revealing the less-known skarn Be enrichment characteristics, in-situ electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) along with element mapping were performed on the Be-bearing vesuvianite and scapolite grains from the Cuonadong Sn-W-Be skarn. As the main Be-bearing calc-silicate minerals, the vesuvianite (X19Y13Z18T0-5O68W10) and scapolite (M4T12O24A) incorporate Be element via occupying normally vacant T site and the Al-2(SiBe) substitution, respectively, and show outward increased Be content related to the varying solid-solution composition arising from the dynamic evolution of skarn. The homogeneous core enveloped by oscillatory mantle and rim under BSE or CL image and the increased liquid inclusion size towards the rim reflect both mineral’s staged growth under an elevated water–rock ratio. The increased Ca activity caused by enhanced interaction between fluid and Mn-containing carbonate may drive scapolite constituent change through (NaSi)-1(CaAl) substitution, creating more tetrahedral Al sites suitable for Be occupation and resulting in the increased Ca, CO32–, Be content and decreased Na content from core to rim. Precipitation of fluorite will lead to a reduce in hydrothermal Be solubility associated with a decreased fluorine activity, and favor Be to occupy the vacant T site by losing more hydrogen from the anion W site and finally form the Be-rich, Ca- and F-low vesuvianite rim. Significantly high Be, Sn, Mn and low Sr, LREE, U content at vesuvianite rim along with hydration alteration and mineralization suggest the onset of retrograde stage. Overall, the dynamic growth and epitaxially rising Be concentration of vesuvianite (∼97–1032 ppm) and scapolite (∼902–2928 ppm) recorded that the later pulsed fluid enriched Be as skarn developed, implying high grade Be mineralization tends to occur in the late magmatic-hydrothermal stage for F-rich peraluminous magmatic system.

Metamorphic evolution of the UHT granulites from Mandikota, Eastern Ghats Mobile Belt, India: Constraints from phase equilibria modelling, fluid inclusions and monazite U-Th-total Pb geochronology

The Eastern Ghats Mobile Belt (EGMB) had been subjected to extreme thermal metamorphic history at various sections of its terrane. One such terrane (Mandikota) located near the western part of the EGMB has been speculated based on asserted reaction textures, conventional geothermobarometry, geochronology, fluid inclusions, and pseudosection modelling. The present integrated study aims to understand the intricacies of the diversified and controversial tectono-metamorphic evolution of these polycyclic granulite terranes. The stable occurrence of sapphirine + quartz in contact is rare in its own and is a diagnostic feature of Ultra-High Temperature (UHT) metamorphism. Conventional geo-thermobarometeric tools applied, suggests an ordered series of reactions for the different stages of metamorphism experienced by the investigated granulites. Also, the P-T estimated by conventional methods lies in sound correlation with the peak P-T condition (in excess of 950 °C at nearly 9 kbar) attained in the constrained pseudosection model. The exhumation trajectory of the examined UHT terrane reflects P-T path responsible for the thrusting mechanism with isothermal decompression of 3 kbar followed by late-stage isobaric cooling. This study also presents the primary report for the systematic fluid inclusion study of the UHT granulites and its correlation with the evolved P-T trajectory. In addition, monazite dating using Electron Micro Probe Analysis (EPMA) is procured to assess the time frame in understanding the P-T-t evolution of the high-grade terrane. The geochronological study further revealed a new age (∼600 Ma) associated with the Visakhapatnam Domain which adheres to the Pan-African orogeny and marks the reworking phase of the widely reported the Grenvillian event in the EGMB province. As such, the results from the studied fluid inclusions displaying monophase inclusions of CO2-rich carbonic fluid, and its corroboration with the P-T pseudosection model interpreting the phase equilibrium conditions prevailing during the Neoproterozoic time (∼900 Ma).

Using critical fluid carbon dioxide to optimize the enzymatic transesterification of soybean oil and ethyl ferulate to feruloyl soy glycerides

AbstractFeruloyl Soy Glyceride (FSG) is an all‐natural replacement for petroleum‐based ultraviolet absorbing ingredients currently used in sunscreens. It is produced by the Novozym® 435‐catalyzed transesterification of ethyl ferulate (EF) with triglycerides. By‐product fatty acid ethyl esters (FAEEs) are more soluble in CO2 than the EF and triglyceride starting materials. It was hypothesized that the preferential removal of the FAEEs over EF would drive the enzymatic reaction towards the desired FSG product. The effect of CO2 pressure and temperature on the solubilities of components of the FSG reaction mixture was studied to select optimized conditions for the enzymatic reaction and purification. Pressure–temperature conditions were then selected to use in a recycling system. The enzymatic products were analyzed for CO2 with and without recycling CO2. The solubilities of all components of the reaction mixture were proportional to CO2 density but the relative solubilities of individual components were not equal at all pressures and temperatures. At 60°C, the ratio of ethyl linoleate to EF was only 1.1 at 6.9 MPa but 3.1 at 13.8 MPa. The CO2 was recycled through the reactor at 13.8 MPa (removing more FAEE by‐products) and through the receiver at 6.0 MPa (removing less FAEEs). In the recycling treatment, the material left behind in the reactor had 99.6% FSG content. The use of the reduced pressure receiver in a recycling CO2 system effectively increased the amount of EF incorporated onto the soybean oil increasing the yield of the FSG product.

Investigation into the effects of foaming variables on the cellular structure and expansion ratio of foamed TPU using response surface methodology

Thermoplastic polyurethane elastomer (TPU) foams were prepared using the high-pressure autoclave with supercritical fluid carbon dioxide (SC-CO2). The effects of foaming variables (i.e. saturation temperature, saturation pressure, and depressurization rate) on cellular structure and expansion ratio were investigated. The model between expansion ratio and foaming variables was constructed using the Box-Behnken design (BBD) of response surface methodology (RSM), and analysis of variance (ANOVA) was conducted to evaluate the validity and significance of the model. Finally, the interactive effects of foaming variables on the expansion ratio were investigated, and the expansion ratios of maximum and center point from numerical model were verified by experiment. The result showed higher saturation pressure and depressurization rate resulted in the more uniform cellular structure and higher cell density, however the higher saturation temperature resulted in the bigger cell and nonuniform structure. The ranges of average cell diameter and cell density were 15.26–45.4 μm and 0.32 × 108 to 6.24 × 108 cells/cm3, respectively. The model obtained using BBD of RSM was valid to predict the expansion ratio in the design window. The saturation temperature was the most important factor influencing the expansion ratio. With the increase of saturation temperature, the expansion ratio always increases in the design window. The maximum expansion ratio from numerical optimization was 4.91, which was located at saturation temperature 190°C, saturation pressure 12.51 MPa, and depressurization rate 5 MPa/s, and the corresponding experiment value was 4.56. The error between them was 7.13%.

Ocean acidification stunts molluscan growth at CO2 seeps

Ocean acidification can severely affect bivalve molluscs, especially their shell calcification. Assessing the fate of this vulnerable group in a rapidly acidifying ocean is therefore a pressing challenge. Volcanic CO2 seeps are natural analogues of future ocean conditions that offer unique insights into the scope of marine bivalves to cope with acidification. Here, we used a 2-month reciprocal transplantation of the coastal mussel Septifer bilocularis collected from reference and elevated pCO2 habitats to explore how they calcify and grow at CO2 seeps on the Pacific coast of Japan. We found significant decreases in condition index (an indication of tissue energy reserves) and shell growth of mussels living under elevated pCO2 conditions. These negative responses in their physiological performance under acidified conditions were closely associated with changes in their food sources (shown by changes to the soft tissue δ13C and δ15N ratios) and changes in their calcifying fluid carbonate chemistry (based on shell carbonate isotopic and elemental signatures). The reduced shell growth rate during the transplantation experiment was further supported by shell δ13C records along their incremental growth layers, as well as their smaller shell size despite being of comparable ontogenetic ages (5–7 years old, based on shell δ18O records). Taken together, these findings demonstrate how ocean acidification at CO2 seeps affects mussel growth and reveal that lowered shell growth helps them survive stressful conditions.

Clay authigenesis in carbonate-rich sediments and its impact on carbonate diagenesis

The Mg (δ26Mg), Ca (δ44Ca), and Sr (87Sr/86Sr) isotopic compositions of pore fluids, bulk carbonates, planktonic foraminiferal tests, and bulk clays from ODP Site 762 Hole B are presented, as are pore fluid and bulk carbonate δ26Mg and 87Sr/86Sr from ODP Site 806 Hole B and pore fluid δ26Mg from ODP Site 807 Hole A. The primary objective of the study is to elucidate the major processes controlling marine pore fluid δ26Mg, specifically the effects of calcite recrystallization and authigenic clay precipitation in sedimentary sections with relatively high carbonate contents. Such studies are critical for evaluating the potential of pore fluids in carbonate section to drive diagenetic alteration, which can compromise applications of geochemical proxies to the past. Pore fluid δ26Mg values at all three sites range from −0.83 to −0.13‰ and exhibit a systematic increase with depth. Bulk carbonate δ26Mg generally decrease with depth, ranging from −3.60 to −5.27‰, at Sites 762 and 806, while mixed species foraminiferal tests (∼250–500 μm) from Site 762 range between −5.08 and −4.36‰. Residual siliciclastics at depths of ∼105 to 145 mbsf at Site 762 have δ26Mg values (−0.09 to 0.27‰) that are markedly higher than carbonate and pore fluid δ26Mg values. Simple 1-D reactive transport modeling suggests that the general increase in pore fluid δ26Mg with depth, accompanied by a decrease in carbonate δ26Mg, is a result of calcite recrystallization (assuming an isotopic fractionation factor of ∼0.9955). However, subtle but significant deviations from the carbonate recrystallization-only scenario suggest that another process impacts δ26Mg at all three sites. Scanning electron microscope images document clay particles embedded in nannofossils and foraminiferal tests at Site 762, which suggest that clay authigenesis is active in carbonate sediments and could affect pore fluid δ26Mg. The formation of secondary clays preferentially sequesters isotopically heavy Mg (αclay-Mg2+≈1.0005), driving pore fluid δ26Mg to lower values. An increase in carbonate δ26Mg within the clay-rich layer at Site 762 and an increase in bulk carbonate Na/Ca supports the hypothesis that clay authigenesis also impacts the preservation of proxy archives. Multi-component reactive transport modeling suggests that authigenic rates of ∼1·10−13 mol/m3/s (∼3.15 µmol/m3/a; assuming that the authigenic clay is sepiolite) can generate deviations from the carbonate recrystallization-only case by several tenths of a permil, indicating that carbonate sediment-associated clay authigenesis (CSCA) may be more relevant in deep-sea carbonate sections than has been previously considered.

Effects of crystal rotation on the carbon transport in the top-seeded solution growth of SiC single crystal

To achieve a high and uniform growth rate for the solution growth of silicon carbide (SiC), the fluid flow and carbon transport in the solution should be well estimated and controlled. The application of crystal rotation is effective in controlling the flow pattern and carbon transport in the SiC growth system. In this paper, the effects of crystal rotation on the solution flow, carbon concentration and growth rate for growing SiC crystals were numerically investigated by using a global heat and mass transfer model. The results indicated that crystal rotation strongly enhances the convection in the solution and makes the upward flow proceed deeper, resulting in the distribution of radial temperature along the growth interface turning from convex to concave towards the solution with the increase in the crystal rotation rate. Consequently, the carbon transport in the solution is strengthened, leading to an increase in the maximum value of the growth rate with a higher crystal rotation rate. However, the radial uniformity of the crystal growth rate along the growth interface becomes poor due to the hot solution moving upward to the center of the seed crystal with the increase in the crystal rotation rate. In the present study, it is found that the intensity of the forced convection vortex generated by an intermediate crystal rotation rate is beneficial to obtain a uniform distribution of growth rate and a relatively high growth rate.

Oxygen isotopes of the Japanese stalagmites as global and local paleoclimate proxies

AbstractStalagmite oxygen isotopes (δ18O) have been used to reconstruct terrestrial paleoclimates during the late Pleistocene and Holocene. However, the interpretation of the δ18O is not straightforward when determining the factor controlling δ18O; temperature or water δ18O. In addition, the water δ18O changes with rainfall intensity (amount effect), rainfall seasonality, and some other factors. Here, we first review the hydrochemical processes and behaviors of the oxygen isotopes and the other proxies in a cave system, which are fundamental for interpretating the paleoclimatic signals. We then introduce the oxygen isotope records of Japanese caves. Some of the Japanese stalagmites demonstrated a δ18O profile that represented a similar pattern to the Chinese stalagmite records, but had relatively small δ18O amplitudes, which can be explained mainly by temperature changes rather than the amount effect. This demands a reversal of the relationship between climate and rainwater δ18O across the Japanese Islands. Using δ18O data for rainwater samples from four sites in Japan (in Niigata, Fukuoka, Gifu and Mie Prefectures), we presents the results of model calculations to verify how the rainfall intensity and the seasonality relate with the δ18O of rainwater. A significant correlation coefficient was observed in Niigata, where the rainfall δ18O decreases with an increase in the annual amount of rainfall, and with a decrease in the winter rainfall. Similar trends were observed in Fukuoka, whereas while the results of Gifu and Mie exhibited no significant trends. Temperature change was would be the main factor controlling the stalagmite δ18O at the latter two sites. For a better understanding of the stalagmite δ18O records, the measurement of fluid inclusions and carbonate clumped isotopes can be used to evaluate the effect of temperature on the stalagmite δ18O, as well as to reconstruct the water δ18O. We predict that the 17O excess in stalagmites reconstructs the seasonal shift in the vapor sources.

Granitic‐melt and carbonic‐fluid inclusions in diopside megacrysts from ankaramitic basalt dikes at Kamisano, Yamanashi prefecture, northeastern Japan

AbstractLarge phenocrysts, known as megacrysts, are focal points for research due to their ability to encapsulate large inclusions suitable for precise chemical analyses. Ankaramite, a distinctive type of undifferentiated volcanic rock, stands out due to its high MgO and CaO contents and the presence of abundant Ca‐rich clinopyroxene (diopside) and less common Mg‐rich olivine phenocrysts. In this study, granitic melt inclusions together with carbonic fluid inclusions were identified within diopside megacrysts of ankaramitic basalt dikes in the Kamisano region, Yamanashi Prefecture, Japan. The identified melt inclusions are completely crystallized and primarily composed of quartz, alkali feldspar, and plagioclase, with smaller amounts of pargasite, augite, apatite, and sulfides. Small amounts of residual glass were also occasionally observed in the inclusions. The average chemical composition of these granitic melts within the inclusions corresponds to that of calc‐alkaline granodiorite and the melts are characterized by low water content (0.38 wt%) and high concentrations of sulfur (7000 ppm), copper, and iron. The findings suggested that the composition of granitic melt inclusions may provide insights into the characteristics of near‐surface hydrothermal metal ore deposits. The diopside megacrysts also contain CO2H2O fluid inclusions, which are completely crystallized and mainly comprised of calcite and chlorite, along with small amounts of quartz. The crystals are interpreted to have formed by the reaction of original CO2H2O fluids and host diopside. The diopside megacrysts are estimated to have started crystallization from tholeiitic basalt at a depth of ~30 km in the lower crust, and trapped fluids and granitic melts as inclusions at a shallower depth when the tholeiitic magma ascended.

Origin of Early to Middle Triassic ultrapotassic syenites in South China: A record of block amalgamation in East Asia

Alkaline intrusions such as ultrapotassic syenites are typically formed in extensional tectonic settings including continental rift, post-orogenic and post-collisional regimes. Here we present two early Mesozoic ultrapotassic syenite plutons (Tieshan and Yangfang) in South China that were formed in a continent collisional setting. LA-ICP-MS zircon UPb chronological, major and trace elemental, and SrNd isotopic data of these syenites are used to explore their origin and to further constrain the geodynamics of early Mesozoic magmatism in South China. Our new data indicate that the Tieshan and Yangfang plutons were formed in Early Triassic (249 Ma) and Middle Triassic (240 Ma), respectively. The Tieshan and Yangfang syenites have SiO2 contents of 50.84–56.95 wt% and 59.13–68.34 wt%, respectively, both are enriched in alkalis with very high K2O (5.60–9.68 wt%) and K2O/Na2O (1.8–15.7) and in LILE (Ba = 2464–8813 ppm; Sr = 652–3499 ppm), REE (498–1355 ppm) and HFSE (Zr = 264–766 ppm). They show enriched SrNd isotopic compositions with 87Sr/86Sr (t) and εNd (t) of 0.7096–0.7102 and − 5.2 to −6.5, respectively for Tieshan and of 0.7112–0.7119 and − 8.8 to −9.7, respectively for Yangfang. Geochemical data suggest that the studied ultrapotassic syenites were derived by partial melting of ancient subduction-modified lithospheric mantle including slab-derived melt hybridization and slab-derived carbonate fluid metasomatism, with the source depth of 60–90 km for Tieshan and at least 90 km for Yangfang. We further suggest that their origins are related to the transtension of the regional NE–trending strike-slip faults caused by continental collisions during the early Mesozoic amalgamation in East Asia.

Novel numerical simulation of drug solubility in supercritical CO2 using machine learning technique: Lenalidomide case study

In pharmaceutical industry, finding promising ways to enhance the solubility of disparate types of drugs is an important challenge for the orally administered drug delivery system. Disparate techniques based on drug characteristics, nature of dosage form and properties of excipients have recently been under extensive evaluation all over the world to improve the solubility of poorly water-soluble drugs. Among them, supercritical fluid carbon dioxide (SC-CO 2 ) has received paramount attentions due to having considerable advantages like cost-effectiveness and low flammability. Lenalidomide belongs is an orally administered anti-cancer agent, which has recently received indication for the treatment of adult patients with different bone marrow-related malignancies such as multiple myeloma, mantle cell lymphoma and follicular lymphoma. Predicting the optimized value of Lenalidomide inside the SC-CO 2 in a wide range of pressure and temperature via developing mathematical models based on artificial intelligence (AI) is the main objective of this paper. In this study, three different machine learning based models are selected to predict and optimized the drug solubility. The available data includes 28 rows of data with two inputs including temperature and pressure and two outputs including density and solubility. Selected models are Kernel Ridge Regression (KRR), least angle regression (LAR), and Multilayer Perceptron (MLP). After optimizing models and comparing the results, the MLP was selected as the primary model of this research. The models illustrated R-squared scores of 0.999 and 0.994 for density and solubility. The maximum errors are also 2.92 and 6.44 × 10 -2 for these outputs, which shows the accuracy and significant generality of the model.

Far-field brittle deformation record in the eastern Paris Basin (France)

AbstractJurassic carbonate strata in the eastern Paris Basin exhibit several generations of faults, tension gashes and stylolites. Although their relative chronology can sometimes be determined according to cross-cutting relationships, the duration of major deformation phases and their influence on fluid flow and carbonate cementation are still uncertain. This contribution aims to clarify the timing of brittle deformation and associated calcite cementation. Tension gashes filled by calcite in Jurassic carbonates were sampled in outcrops and boreholes and dated through U–Pb geochronology. Almost all the sampled fractures were cemented during the Cenozoic period. Continuous deformation spread from c. 50 to 30 Ma. Tension gashes oriented N10° to N20° dated at 48–43 Ma show the main Pyrenean contractional stage. A second set of calcites were dated at c. 35–33 Ma and document a Late Eocene – Oligocene extension. A transition from the compressional to the extensional regime is expressed by tension gashes dated between 43 and 35 Ma. Finally, tension gashes oriented N150° to N175°, dated between 32 and 18 Ma, may result from the propagation of the horizontal stress generated by the Alpine orogen or by late Pyrenean deformation. Clumped isotope thermometry on five samples revealed both low crystallization temperatures (from 27 to 53 °C) and the meteoric origin of calcite-precipitating fluids. Our research therefore documents a continuous fracturing from Ypresian to Rupelian times, and less expressed brittle deformation during the Miocene period.

Prediction of solubility of some dihydropyridine derivative drugs in supercritical fluid carbon dioxide by RBFNN

Prediction of solubility of some dihydropyridine derivative drugs in supercritical fluid carbon dioxide by RBFNN

Mineralization and magmatic origin of the 2.1 Ga Zhaoanzhuang magnetite-apatite deposit, North China Craton: Constraints on the formation of the Paleoproterozoic iron oxide-apatite deposits

Iron oxide-apatite (IOA) deposits provide large amounts of iron for steel industry worldwide, but their origins are still in dispute. Although IOA deposits were commonly genetically related to intermediate-mafic igneous rocks, the occurrences of IOA deposits in ultramafic rocks are scarce. The Zhaoanzhuang iron deposit in the North China Craton is characterized by comprising abundant low-Ti magnetite, apatite and ultramafic minerals (e.g., olivine, orthopyroxene), but its origin has long been controversial. These ultramafic minerals mainly occur as aggregates surrounded by magnetite in the iron ores and display typical cumulate textures and high Fo values, indicative of magmatic origin. The δ56Fe and δ18O values of magnetite from the ores range from 0.22 ± 0.03‰ to 0.32± 0.03‰ and from 2.6‰ to 4.5‰, respectively, akin to those in magmatic rocks and IOA deposits but distinct from those of metamorphic BIFs. Both types of apatite occurring in the ultramafic aggregates and the iron ores contain 2.07 to 2.69 wt% F, less than 0.65 wt% Cl, up to 7900 ppm rare earth elements (REE) and greatly variable Sr-Nd isotopic compositions, reflecting that both types are of magmatic-hydrothermal origin. The crust-like εNd(t) values (-7.1 to −5.2) of all apatite grains record reset of their Sm-Nd system, which is resulted from the involvement of carbonate fluids based on their similar REE patterns. In situ Sm-Nd isotope analyses of apatite from the ultramafic aggregates and the iron ores have yielded similar Sm-Nd isochron ages at 2100 ± 81 Ma (MSWD = 0.84) and 2096 ± 240 Ma (MSWD = 0.85), respectively, which can constrain the minimum age for the Fe mineralization. Combined with sedimentary age of the strata, the ore-forming age of the deposit was 2.3–2.1 Ga. The negative εNd(t) values of the ultramafic aggregates (-1.2 to −1.0), the iron ores (-1.8 to −1.5) and magnetite (-1.6 to −0.8) from the ores indicate that the ore-forming magma has a slightly enriched signature. Combined with linear relationship between their εNd(t) values and MgO contents, an involved mantle-derived ultramafic magma is most likely to be contaminated by the crustal material during ascending. Therefore, the Zhaoanzhuang deposit is a good Paleoproterozoic case of the rare IOA deposits associated with ultramafic magmas.

Ultrahigh-density carbonic fluids in ultrahigh-temperature metagabbros from the Palghat-Cauvery Suture Zone, Southern India: Phase equilibria modelling and fluid inclusion study

Fluid inclusions trapped in high-grade metamorphic minerals offer direct evidence for the nature and role of fluids involved in lower crustal processes. Here, we report extremely high-density (~1.155 g/cm 3 ) carbonic fluid inclusions preserved within garnet grains in metagabbros from the central segment of the Palghat-Cauvery Suture Zone (PCSZ) in southern India. The metagabbros are composed of coarse-grained garnet, clinopyroxene, orthopyroxene, plagioclase, quartz, and retrograde calcic amphibole. Garnet occurs either as porphyroblastic grains formed during prograde to peak stage, or as fine-grained aggregates around plagioclase possibly formed by post-peak decompressional (near-isobaric) cooling. The peak and retrograde P–T conditions have been estimated as ~940 °C/~11.5 kbar and ~ 840–850 °C/~9.3–10.2 kbar, respectively, based on phase equilibria modelling using pseudosection computation. Fluid inclusions occur as primary and secondary phases within the porphyroblastic garnet and matrix plagioclase. The melting temperatures of these fluid inclusions are in the range of −57.4 to −56.6 °C, indicating nearly pure CO 2 composition. The lowest homogenization temperature from the primary inclusions in garnet (−50.1 °C) translates to extremely high density of 1.155 g/cm 3 . The calculated isochores for the inclusions (~11.3 kbar at 950 °C) are broadly consistent with the peak P–T conditions, suggesting that the fluids are trapped near the peak metamorphic stage under a dry condition. The preservation of ultrahigh-density carbonic inclusions is probably due to isochore-parallel decompressional cooling after the peak metamorphism. The secondary inclusions show slightly lower densities of 1.014–1.053 g/cm 3 (in garnet) and 0.955–0.976 g/cm 3 (in plagioclase), the isochores of which suggest a lower-pressure range of 4.8–5.8 kbar at 800 °C. The high-density pure CO 2 fluids reported in this study as well as in previous studies from the PCSZ, and the isochoric evolution provide robust evidence for the presence of supercritical carbonic fluids in the lower continental crust. • Extremely high-density (~1.155 g/cm 3 ) carbonic fluid inclusions in metagabbros. • Peak and retrograde conditions of ~940 °C/~11.5 kbar and ~ 840–850 °C/~9.3–10.2 kbar. • Garnet aggregates around plagioclase formed by post-peak near-isobaric cooling. • Isochore-parallel decompressional cooling after the peak metamorphism. • Ultrahigh-density fluids are preserved due to isochoric exhumation path.

Modelo cinético hidrodinámico para el estudio de la formación de depósitos de CaCO3 en tuberías

Calcium carbonate deposition inside of pipes is a widespread problem in aqueous fluid transport systems, where calcium and carbonate ions are dissolved. The present study describes the physical and chemical phenomena of mass transport of the chemical species, from the bulk solution to the pipe walls, inside a straight circular pipe. The mass transfer coefficient is estimated using correlations for developing laminar flow. The controlling mechanism is assigned using the Damköhler number and the model simulation results are analyzed for three scenarios: when mass transfer controls the deposition, by mixed control or by the deposition kinetics. If mass transfer is the controlling mechanism, the deposit was concentrated at the pipe entrance, while with kinetic control, it forms further downstream. This study found that most important factor influencing the deposition process is the bulk and superficial pH values.

Atomistic growth model with edge diffusion for chiral carbon nanotubes

We carried out exact finite-size analysis and numerical simulation within a kinetic 5-vertex model to study the growth dynamics of chiral carbon nanotubes. The model comprises carbon atoms deposition and migration at the nanotube edge considered as Markov processes and a generalized Glauber dynamics is assumed. The physical parameters considered are the supersaturation of the carbon fluid phase, the synthesis temperature and the nanotube chirality which is known to be fixed by the nucleated cap. In the model, we are interested by the elongation of the nucleus in a tube. We calculated the growth rate and edge defect densities . The growth modes of the tube have been singled out in the model parameters’ space. It has been found that spiral growth by pre-existing steps displacements is present beyond 1D-nucleation and continuous growth. In particular we obtained that in suitable physical conditions, the growth rate increases proportionally with the chiral angle θ of the nanotube up to a critical value θ c which depends on values of model parameters. • Mapping of a chiral SWCNT growth onto a kinetic 5-vertex model. • Deposition and diffusion of carbon atoms at the SWCNT edge are considered. • Exact calculations and Monte Carlo simulation methods are used. • Growth rates and defects densities are calculated and growth modes of the CNT edge specified. • The elongation rate and the SWCNT chirality are linearly correlated in some model parameters ranges.

Impact of High Methane Flux on the Properties of Pore Fluid and Methane-Derived Authigenic Carbonate in the ARAON Mounds, Chukchi Sea

We investigated the pore fluid and methane-derived authigenic carbonate (MDAC) chemistry from the ARAON Mounds in the Chukchi Sea to reveal how methane (CH4) seepage impacts their compositional and isotopic properties. During the ARA07C and ARA09C Expeditions, many in situ gas hydrates (GHs) and MDACs were found near the seafloor. The fluid chemistry has been considerably modified in association with the high CH4 flux and its related byproducts (GHs and MDACs). Compared to Site ARA09C-St 08 (reference site), which displays a linear SO42- downcore profile, the other sites (e.g., ARA07C-St 13, ARA07C-St 14, ARA09C-St 04, ARA09C-St 07, and ARA09C-St 12) that are found byproducts exhibit concave-up and/or kink type SO42- profiles. The physical properties and fluid pathways in sediment columns have been altered by these byproducts, which prevents the steady state condition of the dissolved species through them. Consequently, chemical zones are separated between bearing and non-bearing byproducts intervals under non-steady state condition from the seafloor to the sulfate-methane transition (SMT). GH dissociation also significantly impacts pore fluid properties (e.g., low Cl-, enriched δD and δ18O). The upward CH4 with depleted δ13C from the thermogenic origin affects the chemical signatures of MDACs. The enriched δ18O fluid from GH dissociation also influences the properties of MDACs. Thus, in the ARAON Mounds, the chemistry of the fluid and MDAC has significantly changed, most likely responding to the CH4 flux and GH dissociation through geological time. Overall, our findings will improve the understanding and prediction of the pore fluid and MDAC chemistry in the Arctic Ocean related to CH4 seepage by global climate change.

Effects of elevated pCO2 and temperature on the calcification rate, survival, extrapallial fluid chemistry, and respiration of the Atlantic Sea scallop Placopecten magellanicus

AbstractAnthropogenic CO2‐emission is causing ocean warming and acidification. Understanding how basic physiological processes of marine organisms respond to these stressors is important for predicting their responses to future global change. We examined the effects of elevated pCO2 and temperature (pCO2 = 344–2199 ppm; temperature = 6°C, 9°C, and 12°C) on the calcification rate, extrapallial fluid (EPF) carbonate chemistry, respiration, and survivorship of Atlantic sea scallops (Placopecten magellanicus) in a fully crossed 143‐d experiment. Rates of calcification and respiration were inhibited by elevated pCO2, and mortality occurred when elevated pCO2 was accompanied by high‐temperature stress. Declines in growth and survivorship were likely caused by external shell dissolution, thermal stress, and hypercapnic reduction of metabolism under elevated pCO2. Concentrations of dissolved inorganic carbon (DIC) and total alkalinity in the EPF increased above seawater concentrations in response to elevated pCO2. EPF pH declined, but did not decline as much as seawater pH, indicating that scallops regulate EPF pH to support calcification. The combination of EPF pH regulation and DIC elevation yielded an increase in EPF [] under elevated pCO2 treatments. The combination of low respiration rates, high EPF [], and low calcification rates under elevated pCO2 suggests that the impaired calcification arises more from hypercapnic inhibition of metabolic activity and external shell dissolution than from chemically unfavorable conditions in the EPF. These results demonstrate the importance of EPF chemistry for bivalve biomineralization, but show that regulation efforts are insufficient to fully offset the deleterious effects of elevated pCO2 on scallop performance.

Fault analysis of a salt minibasin offshore Espírito Santo, SE Brazil: Implications for fluid flow, carbon and energy storage in regions dominated by salt tectonics

High-quality 3D seismic reflection and well data are used to investigate the distribution, evolution history and significance of tectonic faulting in a salt minibasin offshore Espírito Santo, SE Brazil. Displacement-length (Dmax-L) plots, displacement-depth (D-Z) plots and structural maps are compiled to understand the growth history of distinct fault families. Interpreted structures include crestal, corridor, listric and keystone faults. Their geometry, orientation and relative distribution reveal important differences. In detail, listric faults were formed in the investigated salt withdrawal basin following a NW to WNW strike, and show multiple bright spots and pockmarks around them. The strata into which listric faults sole out have similar seismic, lithological and petrophysical characters to known Cenomanian to Turonian source rocks, which comprise shales and marls with high gamma-ray values. Low-amplitude to transparent seismic facies further indicate the presence of ductile, highly likely organic-rich shales and marls. As a result, three evolutionary stages can be identified: a) Stage 1 is characterised by the formation of NW- or WNW-striking listric faults, keystone faults and the onset of reactive diapirism; b) Stages 2 and 3 record active diapirism due to a relative increase in sediment loading, documenting the formation of many crestal, corridor and keystone faults. Importantly, normalised leakage factor analyses reveal keystone faults to be the most favourable pathways to fluid migrating in the investigated salt minibasin. Conversely, listric faults are likely to form barriers and baffles to fluid in their lower parts.