Ratio In Barite Research Articles

Metallogeny and Genesis of Fault-Filling Barite-Sulfide Veins (Ougnat, Morocco): Petrography, Fluid Inclusion, and Sr-S Isotopic Constraints

The Ougnat Massif of the eastern Anti-Atlas (Morocco) hosts barite and sulfide vein-type deposits of vital economic importance. With over 150 mineralized structures reported in the Ougnat Massif, the ore-bearing ones are predominantly composed of barite, quartz, calcite, and minor portions of sulfides. The mineralized veins are driven by NW-SE and NE-SW to E-W oblique-slip opening faults that cross both the Precambrian basement and its Paleozoic cover. The mineralized structures occur as lenses and sigmoidal veins that follow stepped tension fracture sets oblique to the fault planes. These geometries and kinematic indicators of these structures point to a predominantly normal-sinistral opening in a brittle-ductile tectonic setting. The S isotopic compositions of barite from the Ougnat Massif (+10.8 to +19.5‰) fall mostly within the range of δ34S values of Late Triassic to Jurassic seawater, thus suggesting that some of the SO2− in barite comes from seawater sulfate. This range of δ34S values also corresponds approximately to the hydrothermal barite context. The 87Sr/86Sr ratios of barite, which range from 0.710772 to 0.710816, lie between the radiogenic strontium isotopic compositions of deposition by hydrothermal solutions, and also coincide with the non-radiogenic isotopic signature of Triassic to Jurassic seawater. Based on a fluid inclusions study, the ore-forming fluids were a mixture of two or more fluids. A deep hot fluid with an average temperature of 368 °C leached the granodiorites and volcanic-sedimentary complex of the Ouarzazate Group. This fluid provided the hydrothermal system with most of the Ba, radiogenic Sr, and some of the dissolved S. A second, shallow fluid with an average temperature of 242 °C was derived from Late Triassic to Jurassic seawater. The barite mineralization of the Ougnat Massif constitutes a typical example of vein-type mineralization that occurred along the northern margin of the West African Craton and regionally tied to the central Atlantic opening.

Calculation of Gamma and Neutron Shielding Parameters for Reinforced Polymer Composites

Abstract In this study, the shielding parameters for isophorone diamine (IPDA) with different ratios of barite (BaSO4), boron carbide (B4C), and aluminum oxide (Al2O3) composites were theoretically investigated. The mass attenuation coefficients (μm) were calculated at the photon energy range (1 keV to 20 MeV) using the xcom program. The obtained data were used to calculate the linear attenuation coefficients (μ), relaxation lengths (λ), half value layer (HVL), and tenth value layer (TVL) for the same range of energy. For comparison, five other shielding materials, ordinary concrete, high-density polyethylene, borated polyethylene, lithium polyethylene, and water, were also studied. The macroscopic fast neutron removal cross-sections (∑R) were calculated for the selected composites. The obtained results show that the shielding parameters strongly depend on the photon energy, chemical composition, and density of the investigated materials. The dependence of mass attenuation coefficients and macroscopic fast neutron removal cross section on the chemical composition of the selected polymer composites was discussed. Barite composite is seen to be a good attenuating material; aluminum oxide composite is a reasonable attenuating behavior, while Boron composite shows a relatively weak attenuating properties. The results obtained through this work can be used to understand the behavior and shielding effectiveness of the selected polymer composites.

Bioclast-controlled patchy barite cementation – Origin and impact on reservoir properties in deeply buried Upper Jurassic sandstones, North Sea

Reservoir non-destructive patchy barite cement occurs in volumes up to 16 vol% in deeply (>5150 m) buried shoreface sandstones in the Hejre field, Danish Central Graben, North Sea. Barite typically occurs as an accessory cement in the sandstones of the Upper Jurassic Heno Formation; however in the Hejre field, barite appears more abundant in the crestal-most well than in other wells. The purpose of this study is to describe the characteristics and the origin of patchy barite cement besides implications for reservoir properties. Petrographic investigations by optical and scanning electron microscopy supplemented by isotopic analysis by SIMS (secondary ion mass spectroscopy) were applied to reveal the barite cementation process. Porosity and permeability of the sandstones were measured by conventional core analysis. Barite cement occurs in the Hejre field with three morphologies: crystals arranged in rosettes, crystal fillings of bioclasts, and multiple-oriented intergrown small crystals in veins. SIMS showed similar sulphur and oxygen isotopic compositions for these barite morphologies, and this composition resembles evaporite-derived barite cement. A hydrothermal origin of the fluid is supported by the associated precipitation of pyrite, chalcopyrite, sphalerite and galena, and a high Sr/Ba ratio in barite. Conventional core analysis revealed major reductions in porosity and permeability when barite cement occurs as fracture filling or in combination with calcite cement in shell lags. However, these occurrences are rare and have a minor influence on the overall reservoir properties. Minor reduction of porosity and permeability characterizes sandstones with barite cement in rosettes of radiating crystals. This growth pattern was probably promoted by slow seep of sulphate-rich fluids which, by mixing with barium-bearing formation water became super-saturated with respect to barite as they moved towards lower temperature and pressure zones. Faults acted as pathways for transport of sulphate-rich fluids possibly from evaporite deposits, whereas barium may have originated from compactional fluids leached out of underlying volcaniclastic rocks. Thermochemical sulphate reduction led to precipitation of sulphide minerals, minor sulphur fractionation and fluid acidification, whereby calcareous bioclasts dissolved. Barite precipitated when the fluids entered these large- or over-sized pores with small obstacles causing prolonged fluid-rock interaction. The bioclast-replacing and patchy barite cement caused only limited reduction of reservoir porosity and permeability compared with barite-free sandstones from the Heno Formation found at a similar burial depth.

A revised seawater sulfate S-isotope curve for the Eocene

The sulfur isotope ratio (δ34S) recorded in marine barite is commonly used to estimate secular changes in the sulfur isotopic composition of seawater sulfate (δ34SSO4) throughout Earth's history. The Cenozoic record demonstrates a drastic 5‰ increase in seawater δ34SSO4 during the Early Eocene. However, the gradient of this excursion is based on only a few data points. Taking advantage of a much improved biostratigraphic framework, we redefine the Eocene δ34SSO4 data with a new high-resolution barite based δ34S record between 60 and 30 Ma. Our results show that the rise of δ34SSO4 starts about 3 million years later (~53 Ma) and lasts about 9 million years longer (until 38 Ma) than previously depicted. As such, the gradient of the δ34S curve is ~0.4‰/Myr. The radiogenic strontium isotopic ratio in barite suggests that some of the samples used for the original barite record are affected by diagenetic alteration.

Application of arsenic in barite as a redox indicator for suboxic/anoxic redox condition

Redox condition is an important factor that controls the behavior of various elements in an aquatic environment. Incorporation of redox-sensitive trace elements in minerals describes redox conditions in water and provides information about past environmental changes, unless it is dissolved or recrystallized during sediment burial. In the present study, we explore the application of arsenate/arsenite ratios (As(V)/As(III)) in barite as a new geochemical proxy for paleo-environmental reconstruction. Laboratory experiments showed that both As(III) and As(V) could be incorporated into barite as As(III)- and As(V)-coprecipitated barite, respectively, which could more or less retain the information of the As(V)/As(III) ratio in coexistent water, if under equilibrium in terms of the redox reactions. Furthermore, the As(V)/As(III) ratios in natural barite collected in (i) Tamagawa Hot Spring and (ii) Okinawa hydrothermal vent were determined by micro-X-ray fluorescence and micro-X-ray absorption fine structure analysis to (a) evaluate the reliability of the As(V)/As(III) ratio in barite as a redox indicator in natural system and (b) estimate the depositional redox condition in water whether barite precipitated below or above the redox boundary of As(V)/As(III), or the suboxic/anoxic boundary. Our previous study showed that barite–selenium oxyanion system could also be used as a proxy for the oxic-suboxic boundary because the selenate/selenite [Se(VI)/Se(IV)] ratio in barite is primarily correlated with the ratio in water. Given that the redox boundary of the Se(VI)/Se(IV) ratio has higher redox potential than the As(V)/As(III) boundary, the combination of these two systems can extend the redox condition, which can be specified by the analysis of one single barite grain to a wide region. Thus, one barite particle can provide information on the As(V)/As(III) and Se(VI)/Se(IV) ratios in water, and whether barite precipitated under oxic, suboxic, or anoxic redox environments.

Estimation of Se(VI)/Se(IV) ratio in water by the ratio recorded in barite

It is possible that the distribution behaviors of redox‐sensitive elements such as selenium (Se) between authigenic minerals and water can provide information on the oxidation state of the element in the coexistent water during mineral deposition. Considering the similar chemical characteristics of Se(IV) and Se(VI) oxyanions, we propose that the Se(VI)/Se(IV) ratio in a particular precipitate, such as barite, may enable us to estimate the Se(VI)/Se(IV) ratio in the coexistent water. The coprecipitation experiments of Se with barite coupled with the determination of the oxidation state of Se both in the aqueous phase and in barite were conducted by Se K‐edge X‐ray absorption near‐edge structure and high‐performance liquid chromatography connected to inductively coupled plasma‐mass spectrometry, respectively, to investigate the influence of the oxidation state of Se on its immobilization into barite at pH 4.0 and 8.0. The results showed that the Se(VI)/Se(IV) ratio in barite was correlated with the Se(VI)/Se(IV) ratio in water, which in turn can provide physicochemical and biogeochemical information related to the Se(VI)/Se(IV) ratio in water in the environment where barite precipitated.

226Ra-in marine barite: relationship with carbonate dissolution and sediment focusing in the equatorial pacific

Sedimentation rates were determined from the 226Ra ( T 1/2=1602 a) decay in barite in seven cores collected from the western, central and eastern equatorial Pacific. Timing of the last carbonate dissolution increase was investigated with this new chronometer. However, an unconformity in the 226Ra-in-barite profiles was observed at some sites, which could be related to this carbonate dissolution event. We discuss different mechanisms that may have generated these unconformities, including (1) bioturbation, (2) possible bias in the estimate of the correction for supported 226Ra activities, (3) changes in the 226Ra/Ba ratio within surface waters and (4) processes that may have affected the 226Ra/Ba ratio recorded in barite, either within the water column or at the sediment–water interface. Among the processes invoked, an increase in the sediment focusing during the Holocene constitutes the mechanism that can most likely explain the observed unconformities. An increase in the sediment redistribution by bottom currents would enhance the lateral transport of old resuspended barite crystals (with a low 226Ra/Ba ratio). The 226Ra/Ba ratio of barite that accumulates in the sediments, therefore, may have decreased, leading to the unconventional 226Ra-profile shape observed in several cores. A change in the chemistry of the bottom waters that transport the resuspended sediment may have also affected the sediment carbonate contents.

Comparison of some sediment-hosted, stratiform barite deposits in China, the United States, and India

Shifts in world barite production since the 1980s have resulted in China becoming the world's largest barite-producing country followed by the US and India. Most barite produced for use in drilling fluids is derived from black shale- and chert-hosted, stratiform marine deposits. In China, Late Proterozoic to Early Cambrian marine barite deposits occur on the oceanic margins of the Yangtze platform, in the Qinling region in the north and the Jiangnan region in the south. Most US ore-grade deposits are in the Nevada barite belt; most commercial deposits occur in Ordovician and Devonian marine rocks along the western margin of the early Paleozoic North American continent. Production in India is predominantly from a single Middle Proterozoic deposit in a sedimentary basin located on Archean basement in Andrah Pradesh. The geologic and geochemical characteristics of the deposits are consistent with origins from a variety of sedimentary-exhalative processes, with biogenic processes contributing to the concentration of some seafloor barite. Linear distributions of clusters of lenticular deposits suggest a geographic relationship to syndepositional seafloor fault zones. Sulfur isotope data of the barite deposits range from values that are similar to coeval seawater sulfate to significantly higher δ 34S values. Strontium isotope values of continental-margin-type deposits in Nevada and China are less radiogenic than those of cratonic-rift deposits (e.g. Meggen and Rammelsberg). Comparison of La n /Ce n ratios of barite in the Qinling region of China with marine chert ratios suggests a relationship to hydrothermal fluids, whereas ratios from the Jiangnan region and Nevada can be interpreted as reflecting a biogenic influence. The California Borderland provides a potential modern analog where hydrothermal barium is being deposited on the seafloor in fault-block-bounded basins. Anoxic to dysaerobic conditions on some marine basin floors result from upwelling, nutrient-rich currents and high productivity in surface waters. In this setting, biogenic processes could contribute to the concentration of barium from hydrothermal sources.

Sr/Ba in barite: a proxy of barite preservation in marine sediments?

The observation by Bertram and Cowen [J. Mar. Res. 55 (1997) 577–593] that the strontium content of marine barite decreased from the water column to the deep-sea floor suggested that the Sr/Ba ratio in barite was sensitive to barite dissolution. Following this observation, we have investigated the potential of using the Sr/Ba ratio in barite as a proxy of barite preservation by separating barite crystals from sediment cores collected at different water depths in the equatorial Pacific and in the Southern Ocean. Our investigations do not reveal significant downcore variations in the Sr/Ba ratios during the Holocene period in the two basins and up to a few hundred thousand years in the equatorial Pacific. However, a comparison of the mean Sr/Ba ratios in individual cores suggests that the Sr/Ba ratios in barite decrease with increasing water depth, a feature that could be related to dissolution of barite crystals during settling to the deep-sea floor and/or at the sediment–water interface. If confirmed, the Sr/Ba ratios in barite could be used to infer the intensity of barite dissolution and the state of preservation of barite crystals in sediments. Such information could be employed usefully in paleoproductivity reconstructions for the purpose of distinguishing between productivity and dissolution signals affecting barite distributions in marine sediments.

Mineralogy, Geochemistry, and Age Constraints on the Zn-Pb Skarn Deposit of Maria Cristina, Quebrada Galena, Northern Chile

The Maria Cristina Zn-Pb skarn deposit, hosted by carbonate rocks of the Lower Cretaceous Chanarcillo Group in northern Chile, is described to provide a basis of comparison to adjacent (~2 km) barite deposits and regional Pb-Zn and Ba deposits with Mississippi Valley-type affinities. Strongly retrograded garnet (andradite to Ad30Gr70), diopsidic pyroxene, and epidote skarn, and barite-bearing massive sulfides (sphalerite-pyrite-galena-marcasite-magnetite) occur at the contact of potassically altered diorite porphyry of mid-Cretaceous age. The skarn mineral compositions, similar to those of Cu skarns, may reflect emplacement in a high f O2 context. Sulfur isotope values of sulfides (–8.8 to +7.1‰) and barite (14.0–26.1‰) indicate disequilibrium conditions and different sulfur sources, including magmatic sulfur. Lead isotope ratios of galena and strontium isotope ratios of barite indicate a similar metal reservoir for the different ore deposit types, constituted by the intercalated Lower Cretaceous volcanic rocks or mid-Cretaceous intrusive rocks. 40Ar/39Ar dating of hydrothermal K feldspar suggests an age between 94 and 90 Ma for the mineralization.

Vein and Karst Barite Deposits in the Western Jebilet ofMorocco: Fluid Inclusion and Isotope (S, O, Sr) Evidence for Regional FluidMixing Related to Central Atlantic Rifting

Numerous vein and karst barite deposits are hosted by Hercynian basement and Triassic rocks of the western Jebilet in Morocco. Sulfur, oxygen, and strontium isotope analyses of barite, combined with fluid inclusion microthermometry on barite, quartz, and calcite were used to reveal the nature and source of the ore-forming fluids and constrain the age of mineralization. The δ 34S values of barite between 8.9 and 14.7 per mil are intermediate between the sulfur isotope signatures of Triassic evaporites and Triassic-Jurassic seawater and lighter \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(SO_{4}^{2{\mbox{--}}}\) \end{document}, probably derived from the oxidation of dissolved H2S and leaching of sulfides in the Hercynian basement. The 87Sr/86Sr ratios of barite between 0.7093 and 0.7130 range between the radiogenic strontium isotope compositions of micaceous shale and sandstone and the nonradiogenic isotopic signature of Triassic to Jurassic seawater and Cambrian limestone. The δ 18O values of barite between 11 and 15 per mil (SMOW) support mixing between two or more fluids, including Late Triassic to Jurassic seawater or a water dissolving Triassic evaporites along its flow path, hot basinal, or metamorphic fluids with δ 18O values higher than 0 per mil and/or meteoric fluids with δ 18O values lower than 0 per mil. The general trend of decreasing homogenization temperatures and initial ice melting temperatures with increasing salinities of H2O-NaCl ± CaCl2 fluid inclusions trapped in barite, quartz, and calcite indicates that a deep and hot basinal fluid with salinities lower than 6 wt percent NaCl equiv might have mixed with a cooler surficial solution with a mean salinity of 20 wt percent NaCl equiv. Calcium was leached from the Cambrian limestone and the clastic and mafic volcanic rocks of the Hercynian basement. Alkali feldspars and micas contained in the Cambrain sandstones provided most of the Ba to the hydrothermal system. Vein and karst deposits are modeled as a two-component mixing process in which the temperature and the S and Sr isotope composition of the end members changed during the 220 to 155 Ma interval. The hot basinal fluid remained volumetrically dominant during the entire mineralization process. Differences in mean S, O, and Sr isotope compositions among the barite families are interpreted as reflecting differences in mineralization age. Most barite deposits formed before the Kimmeridgian, except for north-south-oriented vein barite, karst barite, and barite cement in the conglomeratic Upper Jurassic, which were deposited later, possibly around 155 Ma. Similar genetic processes have been described for late Paleozoic to Mesozoic F-Ba vein deposits in western Europe. The vein and karst barite in the western Jebilet of Morocco reveals a wide-scale regional mineralization event related to Central Atlantic rifting.

Authigenic Barite as an Indicator of Fluid Movement through Sandstones Within the Colorado Plateau

ABSTRACT Sandstones of the Salt Wash Member, Late Jurassic Morrison Formation, contain abundant authigenic barite on the east side of the northern Colorado Plateau (mean = 0.5 g barite/kg rock) and systematically less barite (mean = 0.02 g barite/kg rock) in the western part. The area containing abundant barite coincides approximately with the extent of bedded evaporites in the underlying Pennsylvanian Hermosa Formation. A genetic link between the barite and solutes from the Hermosa Formation is supported by sulfur isotope data. Most barites from the abundant barite zone have 34S values that range from +8 to +14 per mil, which is similar to the range of bedded gypsum and anhydrite in the Hermosa Formation. Sulfate derived from t e evaporites probably entered the Morrison Formation in solutions that moved along faults. Measured 87Sr/86Sr ratios of barite in the abundant barite zone are indicative of fault-controlled solution flow. Strontium contents and 87Sr/86Sr ratios (0.7103 to 0.7084) in barite decrease with increasing distance from faults. These trends reflect mixing of radiogenic strontium in the saline waters that ascended faults (87Sr/86Sr = 0.7100), with strontium originally contained in early diagenetic carbonate cements within the sandstones (87Sr/86Sr = 0.7080). Because measured 87Sr/86Sr values exceed the ratios in Hermosa anhydrite, it is concluded that radiogenic strontium was added to the rising brines by reaction between the evaporite-derived saline solutions and arkosic san stones along the flow path. Morrison sandstones within the abundant barite zone were altered by saline waters that added sulfate and strontium. Barite formation in this zone was limited by the availability of dispersed barium in the host rock. The zone of sparse barite on the western side of the Colorado Plateau was not affected by the same warm saline waters. Instead, intraformational redistribution of small amounts of barium, strontium, and sulfate formed the relatively sparse barite in this area.

A hypothesis concerning the origin of barite in Devonian carbonate rocks of northeastern British Columbia

The sulphur isotope ratios of barite in many syngenetic barite deposits are shown to be approximately the same as those of the seawater from which they were deposited. Although the stratiform replacement barite-fluorite deposits of northeast British Columbia are epigenetic, their barite sulphur isotope ratios (δ34S) of +24.2 to +30.1‰ may indicate a late Middle Devonian time of mineralization if the sulphur in these deposits was derived from seawater.A model for barite mineralization is proposed in which mixing of euxinic (i.e., reducing) seawater with meteoric groundwater near the seaward edge of a large coastal aquifer, similar to the present-day Floridan Aquifer, caused solution of the shelf carbonates and induced low-temperature precipitation of barite in the resultant solution cavities. The extensive solution collapse that accompanied mineralization, and the coarse crystallinity and low manganese content (< 65 ppm) of the barite in northeastern British Columbia support this interpretation. The postulated Devonian paleoaquifer in northeastern British Columbia coincided with the regional distribution of solution-collapse breccias in the Stone Formation dolomite. The karsted upper surface of the Sulphur Point Formation may have been the landward recharge area for this aquifer.The variation in the mole percent SrSO4 along barite blades suggests that during precipitation there were changes in the rate of circulation of the mineralizing solution. In some places up to 30% of the barium in solution may have been precipitated. The δ34 values of later formed, strontium-enriched barites tend to be lower suggesting an isotope effect during crystallization favouring 34S in the crystalline phase.

Geochemical implications of the lead content of barite from various origins

Pb/Ba ratios of barite from various origins (hot springs, banks in the Japan Sea and Kuroko-type or vein-type ore mines) vary from 10-5 to 10-1. When they are plotted against chloride concentrations of the barite-precipitating solutions, both expressed in logarithms, the ratios increase almost linearly with a decrease in those of the solutions. For their chloride concentrations except those of hot spring waters, NaCl-equivalent salinities of fluid inclusions in the barite were used as an approximation. This fact is possibly elucidated in terms of chloro-complexing of lead in thermal solutions.