Hydrogen isotope fractionation between OH-bearing minerals and water☆
Abstract
Hydrogen isotope fractionation factors between hydroxyl-bearing minerals and water were determined at temperatures ranging between 400 and 850°C. The hydrogen isotope exchange rates for the mineral-water pairs examined were very slow. In most cases it was necessary to use an interpolation method for the determination of the hydrogen isotope equilibrium fractionation factor, αe.
For the temperature range of 450–850°C the hydrogen isotope fractionation factors for the mica-water and amphibole-water systems are simply expressed as a function of temperature and the molar fractions of the six-fold coordinated cations in the crystal, regardless of mineral species, as follows: 103 In αe(mineral-water) = − 22.4 (106T−2) + 28.2 + (2XAl − 4XMg − 68XFe), where X is the molar fraction of the cations. As the equation indicates, for any specific composition of the OH-bearing minerals, the change of αe with temperature, over the temperature range investigated, is the same for all minerals studied. Thus for any specified values of XAl, XMg, and XFe for these minerals, the relationship between αe and T is 103 In αe = αT−2 + k. Consequently, hydrogen isotope fractionation among coexisting minerals is temperature independent and cannot be used as a hydrogen isotope geothermometer.
Some exceptions to the above general observations exist for minerals such as boehmite and kaolinite. In these minerals hydrogen bonding modifies the equilibrium hydrogen isotopic fractionation between mineral and water.
References (9)
- H Craig
Standard for reporting concentrations of deuterium and oxygen
Science
(1961) - I Friedman et al.
The deuterium content of water in some volcanic glasses
Geochim. Cosmochim. Acta
(1958) - J.D Godfrey
The deuterium content of hydrous minerals from the east-central Sierra Nevada and Yosemite National Park
Geochim. Cosmochim. Acta
(1962) - D.A Northrop et al.
Oxygen isotope fractionation in systems containing dolomite
J. Geol.
(1966)
Cited by (604)
Genesis of the Shaquanzi Zn–Pb deposit in the Eastern Tianshan, NW China: Constraints from geology, fluid inclusion and isotope geochemistry
2024, Ore Geology ReviewsThe Shaquanzi Zn–Pb deposit, located in the Central Tianshan Terrane, is mainly hosted by siliceous slates and carbonaceous marbles of the Mesoproterozoic Kawabulake Group, and its mineralization / alteration can be divided into skarn period (I: early skarn stage, II: late skarn stage), quartz-sulfide period (III: early sulfide stage, IV: late sulfide stage and V: quartz-calcite stage) and supergene period (VI: supergene alteration stage). The W-type fluid inclusions (FIs) were identified in the garnet, chlorite, quartz, and calcite in skarn and quartz-sulfide periods. Detailed fluid inclusion study shows temperature of fluids decreased from Stage I (510–520 °C) through, Stage III (481–507 °C), Stage IV (248–417 °C, peak at 280–400 °C) to Stage V (148–260 °C, peak at 200–220 °C), with salinities of 20.8–22.2 wt% NaCl eqv., 19.8–29.1 wt% NaCl eqv., 10.6–27.8 wt% NaCl eqv. (peaks at 20–23 wt%), and 21.6–29.9 wt% NaCl eqv. (peak at 23–27 wt%), respectively, indicating that the ore-forming fluids consisted of a high-medium salinity and Na-Mg-Fe-Ca-rich fluid system, and may have evolved from high-medium temperature to medium temperature. The H–O isotopic compositions varied from Stage III (δ18OH2O = 7.7 ‰–9.0 ‰ and δDH2O = − 105 ‰ to − 91 ‰) through Stage IV (δ18OH2O = 2.6 ‰ to 4.3 ‰ and δDH2O = − 114 ‰ to − 111 ‰) to Stage V (δ18OH2O = − 4.2 ‰ to − 3.7 ‰ and δDH2O = − 119 ‰ to − 96 ‰), suggesting that the ore-forming fluid sources may have evolved from magmatic fluids to meteoric water. The average δ34SH2O values of the early sulfide, late sulfide, and quartz-calcite stages are 5.7 ‰, 8.5 ‰ and 14.0 ‰, respectively, indicating that the sulfur in the early stage was mainly derived from magmatic hydrothermal sulfur, while the increase of the δ34SH2O values in the late stages is likely to be sourced from the Kawabulake Group through water–rock reaction. Above all, we propose that the Shaquanzi may have been a skarn-type Zn–Pb deposit.
Geology and mineralization of Nb, P, Fe and light rare earth elements of the Araxá alkaline-carbonatite complex, Minas Gerais state, Brazil
2023, Journal of South American Earth SciencesNew 40Sr/39Ar dating revealed that the magnetite phlogopitite at the center of the Araxá complex reached the surface at 98 Ma, and generated volcanoes with mineralized volcanic tuffs and crater lakes. At the bottom of the crater lakes, micro-graywacke deposited. Based on the mineral composition, hydrothermal structures, and δ18O and δD values, a hydrothermal episode occurred between ∼98 and 86 Ma Ma. The δ18O of phlogopites of phlogopities vary between 4.8‰ and 5.7‰, and those of magnetitites are 4.3‰ and 6.8‰. The δ18O of the water in equilibrium with phlogopites of the phlogopitites vary between 2.3‰ and 3.2‰, and those with magnetitite are 4.3‰ and 1.8‰. The δD of phlogopites of phlogopitites vary between −86.5‰ and −95.2‰, and those of magnetitite are −84.9‰, and −85.8‰. The δD of the water in equilibrium with phlogopites of the phlogopitites vary between −26.8‰ and −35.5‰, and with magnetitite are −25.6‰, and −26.26‰. During the hydrothermal event, magnetite phlogopitites were hydrothermally altered into phlogopite magnetitite, magnetite apatitite (epifoskorites), and mineralized with pyrochlore. At 84 Ma, the phlogopitic core was permeated by veins and micro-veins of Sr-rich norsethite carbonatites. At 83.5 Ma, calcitic carbonatites and micro-phlogopitites originating from the same mantle source as the magnetite phlogopitite intruded, which resulted in the formation of a carbonatite ring around the core and the assimilation of part of the phlogopitic core. This magmatism generated a new hydrothermal event of limited coverage that mineralized phlogopitites and carbonatites with monazite and massive pyrite ± chalcopyrite. The magmatism ended at 77 Ma, when phosphorous-saturated calcitic carbonatite surrounded the core. The saturation of phosphorous favored the crystallization of apatite, which generated phosphate deposits.
Temporal variations in geochemistry of hydraulic fracturing fluid and flowback water in a tight oil reservoir
2023, Petroleum ScienceHydraulic fracturing facilitates the development and exploitation of unconventional reservoirs. In this study, the injected hydraulic fracturing fluid (HFF) and flowback and produced water (FPW) in tight oil reservoirs of the Lucaogou Formation in the Junggar Basin are temporally sampled from day 1 to day 64. Freshwater is used for fracturing, and HFF is obtained. The chemical and isotopic parameters (including the water type, total salinity, total dissolved solids (TDS), pH, concentrations of Na+, Cl−, Ba+, K+, Fe2+ + Fe3+, and CO32−, δD, and δ18O) are experimentally obtained, and their variations with time are systematically analyzed based on the flowback water. The results show that the water type, Na/Cl ratio, total salinity, and TDS of the FPW change periodically primarily due to the HFF mixing with formation water, thus causing δD and δ18O to deviate from the meteoric water line of Xinjiang. Because of water–rock interaction (WRI), the concentrations of Fe2+ + Fe3+and CO32− of the FPW increase over time, with the solution pH becoming more alkaline. Furthermore, based on the significant changes observed in the geochemistry of the FPW, three separate time intervals of flowback time are identified: Stage I (< 10 days), where the FPW is dominated by the HFF and the changes in ions and isotopes are mainly caused by the WRI; Stage II (10–37 days), where the FPW is dominated by the addition of formation water to the HFF and the WRI is weakened; and finally, Stage III (> 37 days), where the FPW is dominated by the chemistry of the formation water. The methodology implemented in this study can provide critical support for the source identification of formation water.
Equilibrium hydrogen isotope fractionation between portlandite/brucite and water: Implication from the vibrational spectra at elevated temperature and pressure
2023, Chemical GeologyMinerals in brucite-type structure, including brucite (Mg(OH)2) and portlandite (Ca(OH)2), have been studied as important analogs of hydrous silicate minerals for their thermodynamic properties, including equilibrium hydrogen and oxygen isotope fractionations between minerals and water at elevated temperatures and pressures. In this study, Raman and Fourier transform infrared (FTIR) spectra were collected at high-temperature (T) and high-pressure (P) conditions on synthetic hydrogenated and deuterated portlandite samples (i.e., Ca(OH)2 and Ca(OD)2), and their isobaric and isothermal mode Grüneisen parameters, as well as anharmonic parameters, were then evaluated. These high-precision vibrational spectra enable the evaluation of thermodynamic properties of portlandite (ΔU, CV, CP and ΔS) up to 427 °C, to which anharmonicity has positive contributions. More importantly, they help to determine the isobaric (at P = 1 bar) β factors of brucite and portlandite for equilibrium D/H fractionation considering anharmonic effects, and the D/H fractionation factor (103∙lnα) between brucite/portlandite and water at high-P,T conditions. The calculated equilibrium fractionation factor (lnαbrucite-water) agrees with experimental results in the temperature range from 300 to 647 K (∼27 to ∼374 °C, the critical point of water) within analytical uncertainties estimated using Monte Carlo method. The Ab initio calculation using DFT theory and VASP program was also carried out to obtain phonon spectra for brucite and portlandite with three-split hydrogen sites and to evaluate the dispersion effect, which is found to be smaller than the statistical uncertainty at high temperatures. Our results show that the internal OH-stretching modes in brucite/portlandite play a dominant role in determining the β values, and the anharmonic OH-stretching potential (xi parameter) contributes significantly to the D/H fractionation factor. Because previous studies show that OH-stretching frequencies generally decrease with increasing mass of cation in the metallic hydroxide having similar crystal structure, our results imply that the deuterium isotope may be preferentially enriched in the hydroxide phase with the light cation bonded to the hydroxyl group, which is also consistent with the observed D/H fractionations among hydrous silicates.
Water transport in continental subduction zones: Constraints from eclogite from the Dabie orogen, east-central China
2023, Journal of Asian Earth SciencesWater in nominally anhydrous minerals may exist as structural hydroxyl and molecular H2O, and their inter-transformation can occur during subduction zone metamorphism. This issue is examined here by a systematic study on water in garnet and omphacite for ultrahigh-pressure metamorphic eclogites from the Dabie orogen. IR spectra of garnet at different preheating temperatures imply that the broad absorption band at 3400–3450 cm−1 mainly represents molecular H2O. Molecular H2O in garnet can be intrinsic origin, but is mainly originated from external fluid during exhumation. The positive correlation between molecular H2O and structural hydroxyl in garnet suggests their inter-transformation. Molecular H2O that was formerly included in garnet or derived from decomposition of hydrous minerals was transformed gradually to structural hydroxyl in garnet during subduction. OH− modes at higher wavenumber in garnet are more stable and more enriched in D, and d-poor molecular H2O is preferentially lost during dehydration. Hydroxyl in both anhydrous and hydrous minerals would be transformed to molecular H2O during exhumation and redistributed into garnet or retrograde minerals. The addition of molecular H2O into garnet during exhumation causes increase of structural hydroxyl but decrease of δD value, and affects accurate estimate of water content in peak garnet. Different from the large variation of garnet water contents, omphacite tends to be water-saturated at high-pressure conditions and its water content is mainly controlled by Ca-Eskola. The subducting mafic crust can transport a considerable amount of water to subarc depths to result in the formation of relatively water-rich mantle regions.
The Peña do Seo W-Sn deposit, NW Iberia: Petrology, fluid inclusions and O-H-S isotopes
2023, Ore Geology ReviewsThe Peña do Seo W-Sn ore deposit in NW Iberia consists mainly of quartz veins hosted in schists. Vein mineralogy comprises wolframite, cassiterite and minor molybdenite. Peraluminous S-type granites and minor metaluminous granitoid breccias crop out in the same location. Whole rock geochemistry, mineral characterization, fluid inclusions and stable isotope geochemistry have been combined to infer hydrothermal mineralization conditions.
A pre-ore stage (0) involving the alteration of host rocks, three stages of mineralization (I, II and III), and a supergene stage (IV) have been identified. Stage I (oxide-halide-sulfide stage) consisted of a cassiterite-pyrite-fluorite mineralization in granitoid breccias. Stage II (main oxide stage) involved wolframite-rich selvages and wolframite-cassiterite-(molybdenite) quartz veins. Stage III (main sulfide stage) consisted of a sulfide mineralization in quartz veins comprising pyrite and minor arsenopyrite and chalcopyrite.
Three types of fluid inclusions were found in vein quartz: (1) aqueous two-phase inclusions, with homogenization temperatures (Th) between 445 °C and 280 °C and moderate salinities (9–14 wt% NaCl eq.), (2) aqueous-carbonic three-phase fluid inclusions, with Th from 340 °C to 260 °C and low salinities (2–7 wt% NaCl eq.), and (3) aqueous two-phase fluid inclusions, with Th from 270 °C to 155 °C and low salinities (0–6 wt% NaCl eq.). δ18O values in quartz from mineralized veins range from +11.2‰ to +13.4‰, and between +15.0‰ and +15.4% in quartz from mineralized granitoid breccias. δ34S values in sulfides (pyrite, arsenopyrite and chalcopyrite) range between +13.0 ‰ and +37.1 ‰, thus suggesting a marine source of sulfate and possible equilibration with host-rock sulfides. δD values in muscovite and chlorite from quartz veins range between −105.7 ‰ and −71.5 ‰ and between −69.4 ‰ and −67.1 ‰, respectively, indicating a transition from magmatic to magmatic-metamorphic conditions.
An aqueous (H2O–NaCl) magmatic-hydrothermal fluid led to the W-Sn mineralization, as deduced from the studied fluid inclusions and isotopic signatures. High W and Sn contents in the peraluminous granites indicate that the W-Sn mineralization in Peña do Seo could partially be related to the granites and granitoid breccias. Whereas the Sn (±W) likely derived from hydrothermal fluids exsolving from the crystallizing magmas, host quartz schists would have supplied other elements required for wolframite deposition such as Fe and Mn. Sulfide mineralization in stage III was probably driven by fluid dilution.
- ☆
Publication of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125. Contribution No. 1921.
- †
Present address: Department of Chemistry, Meteorological College, Asahi-Cho, Kashiwa, Chiba-Pref., 277, Japan.