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Boron isotope geochemistry of Na-bicarbonate, Na-chloride, and Ca-chloride waters from the Northern Apennine Foredeep basin: Other pieces of the sedimentary basin puzzle
Geofluids
Abstract
The boron stable isotope ratio δ11B of twelve water samples representative of three chemical facies (fresh Na-bicarbonate, brackish Na-chloride, saline and brine Ca-chloride) have been analyzed. Interpretation of the δ11B data, along with the chemical compositions, reveals that Na-carbonate waters from the Northern Apennine are of meteoric origin, with boron contributions from clay-desorption and mixing with seawater-derived fluids of Na-chloride or Ca-chloride compositions. The comparison of our new results with the literature data on other sedimentary basins of Mediterranean, and worldwide, confirms the contribution of Na-bicarbonate waters to the genesis of mud volcano fluids. The Na-chloride sample of Salvarola (SAL), which may represent the end-member of the mud volcanoes, and the Ca-chloride brine water from Salsomaggiore (SM) indicate boron release from clays compatible with the diagenetic process. The empirical equation: δ11B = [5.1364 x ln(1/B)mg/l] + 44.601 relating boron concentration and the stable isotope composition of the fluids observed in this study and the literature is proposed to trace the effect of diagenesis in sedimentary basins. A geothermometer associated to the diagenetic equation is also proposed: T°C = [δ11B - 38.873 (± 1.180)] / [-0.164 (± 0.012)] The application of this equation to obtain reservoir temperatures from δ11B compositions of waters should be carefully evaluated against the results obtained from other chemical and isotopic geothermometers from other basins around the world.
... This may result from the fact that the authors did not consider potential B inputs from clay minerals. It is now well established that clay desorption can affect marine pore-waters without releasing Cl [47]. Figure 5A indicates that some SR samples lie in the δ 11 B range corresponding to clay desorption, reflecting the fact that several factors may have modified their initial isotope compositions, for example: multiple transgressions and regressions [30], multiple evaporation and recrystallization cycles [48] or meteoric dilution [49]. Possibly, complex tectonics at the Neoproterozoic time, were responsible for marine or fresh water evaporate deposition of study area. ...
... A third group of samples (Mainly formed by the KS and NPW sections) plots outside of these trends ( Figure 5B) and seems to symbolize diagenetic B emitted from clay minerals following stress-driven or temperature-induced effects, as illustrated by Boschetti et al. [49] and Deyhle et al. [53]. Indeed, their B concentration (KS = 106 ppm, NPW = 75 ppm) and their δ 11 B (KS = 17.44‰, ...
... NPW = 19.18‰) are similar to those reported in Salvarola (Italy) for overstressed fluids by Boschetti et al. [49], as well as to fluids rising from a mud volcano reported by You et al. [54] in the vicinity of a decollement zone (i.e. basal detachment fault). ...
In this study, the ion concentrations (K+, Na+, Ca2+, Mg2+, Cl−, SO42−, Br−, NO3−, and B3+) and boron isotope compositions (δ11B) of 34 halite and brines samples from the Neoproterozoic Salt Range Formation, Punjab, Pakistan were studied. Relation among B3+ vs. Mg2+, B3+ vs. SO42−, δ11B vs. B3+, and δ11B vs K+ were observed, they indicated that these elements originate from multiple sources and the end members were identified as seawater, B desorption from clays, and meteoric precipitation. Halite samples of the area under study displayed a Na-HCO3-type to Ca-Cl type sedimentary basin of deposition, on δ11B vs. 1/B plot. Molar ratios of B/Cl vs. δ11B revealed the addition of B in some of the studied samples from desorption of clay minerals. This type of diagenetic desorption of B from clays is the consequence of a stress driven mechanism, generated in the proximity of a decollement zone. Results confirm that the number of B stable isotopes that fractionate between the brine and the halite is low. The halite δ11B from the Salt Range Formation vary from +2.1 to +24.4‰, compared to +17.3 to +26.1‰ in the salt pool brines, and suggest that boron isotope compositions are controlled by the δ11B of the B sources. The positive relationship between the boron content and the corresponding δ11B indicates a higher salinity and drier paleoclimate conditions during the formation process, associated with a high evaporation rate in the Late Neoproterozoic time. Presence of elevated δ11B in the present study, demonstrate compatibility with other marine basins of the world, arising the need for further investigations to better characterize the 11B-enriching processes.
... Boron concentrations are broadly correlated with chlorine concentration in natural fluids ( Fig. 1) because of the high solubility of both elements Mahon, 1964, 1967;Palmer and Sturchio, 1990;Boschetti et al., 2014). The boron and chlorine content of the fluid are mostly controlled by temperature, evaporation, salt dissolution, sequestration into minerals, and fluid mixing (Morell et al., 2008;Vengosh et al., 1991). ...
... The boron and chlorine content of the fluid are mostly controlled by temperature, evaporation, salt dissolution, sequestration into minerals, and fluid mixing (Morell et al., 2008;Vengosh et al., 1991). Saline water, freshwater, hydrothermal fluids, and brines of a given geological setting can therefore show distinct boron and chlorine concentrations (Fig. 1), as well as δ 11 B values (Barth, 1993;Xiao et al., 2013), that can be used to investigate fluid composition and boron sources (Spivack, 1986;Palmer and Sturchio, 1990;Vengosh et al., 1991;Vengosh and Hendry, 2001;Boschetti et al., 2014). The illustrated fluids ( Fig. 1) are fluids potentially involved in bentonite formation, and later cation exchange reactions (Grim and Güven, 1978;Christidis and Huff, 2009), and thus of interest to our study. ...
... Twenty five mL of distilled water (D), an aqueous 1.82% mannitol (M) solution or 1 M ammonium acetate (A) Fig. 1. The boron and chlorine concentrations of fluids from various hydrogeological settings (Palmer and Sturchio, 1990;Vengosh et al., 1991;Bottomley et al., 1994;Lico and Seiler, 1994;Vengosh et al., 1995;You et al., 1996;Aggarwal et al., 2000;Barth, 2000;Pennisi et al., 2000;Kloppmann et al., 2001;Wagner et al., 2003;Morell et al., 2008;Négrel et al., 2012;Karro and Upin, 2013;Boschetti et al., 2014;Blondes et al., 2016;Wu et al., 2016). GW = groundwater, SW = seawater. ...
The mineralogical, chemical and isotopic analyses of smectites, with variable interlayer cation occupancies, from bentonite deposits in various depositional environments, reveal new insights into the boron sources and the fluids involved in bentonitization in marine and non-marine environments.
Smectites from bentonites have non-exchangeable, structural boron concentrations of 0.2 to 196 μg/g B. Smectites from sodium bentonites have higher boron concentrations (>30μg/g) than those from magnesium or calcium bentonites. Most smectites have a small, interstratified illitic component that has a major influence on boron concentrations, requiring the use of modified fluid-mineral boron partitioning coefficients, which indicate that bentonites formed from fluids of highly variable boron concentrations of <0.1mg/L B to >100 mg/L B, and a chlorine content of 76.4 mg/L to 59,076 mg/L. The sodium bentonites formed from boron-rich saline fluids or brines whereas the fluids involved in calcium and magnesium bentonite formation have a more variable boron composition and salinity.
The δ11B values of the structural boron in tetrahedral sites of smectites range from −30.1‰ to +12.2‰. The smectites from terrestrial depositional settings have δ11B values of −30.1‰ to about 0‰, whereas smectites from marine depositional settings have negative as well as positive δ11B values. The boron isotope values indicate that all examined bentonites from terrestrial depositional settings as well as many bentonites from marine depositional settings formed from basinal fluids or brines.
The boron isotope geochemistry of smectites is demonstrated to be a tool for elucidating the fluids involved in the formation of clay mineral deposits. It also has great potential for tracing fluids in other settings involving authigenic clay minerals such as sedimentary basins and surficial crystalline rocks, as well as man-made applications such as in disposal sites for highly active nuclear waste.
... Therefore, the fluid could have preserved the source signature and the deep temperature imprint during fluid upwelling. For example, a temperature of 234°C is inferred by the d 11 B-temperature relationship of Boschetti et al. (2015). The geothermometric equation in that work was produced to explain the boron release from clay minerals in diagenetic processes. ...
... In (a), Aqua de Ney Spring (N-diamond, this study for d 11 B, mean historical data for B/Cl: see text for complete references) is compared with the hydrothermal vents from Juan de Fuca-Gorda Ridges (Campbell et al. 1994;James et al. 2003) and Complexion Spring (Peters 1993). The paths and open fields from Vengosh (2014) and Boschetti et al. (2015), melt inclusions from Mt. Shasta basaltic andesites (Le Voyer et al. 2010), AOC = altered oceanic crust (Le Voyer et al. 2010;Sano et al. 2008) and S = sediments (Boschetti et al. 2015;Campbell et al. 1994;Leeman et al. 2004) are also shown for comparison. In (b), open fields and paths from Vengosh (2014); local thermal/nonthermal groundwaters (Cullen et al. 2015) and hydrothermal vents are also shown (Butterfield et al. 1994;Campbell et al. 1994;Fouquet et al. 1998;Gieskes et al. 2000;Von Damm et al. 2005) Leeman et al. (2004). ...
... In (a), Aqua de Ney Spring (N-diamond, this study for d 11 B, mean historical data for B/Cl: see text for complete references) is compared with the hydrothermal vents from Juan de Fuca-Gorda Ridges (Campbell et al. 1994;James et al. 2003) and Complexion Spring (Peters 1993). The paths and open fields from Vengosh (2014) and Boschetti et al. (2015), melt inclusions from Mt. Shasta basaltic andesites (Le Voyer et al. 2010), AOC = altered oceanic crust (Le Voyer et al. 2010;Sano et al. 2008) and S = sediments (Boschetti et al. 2015;Campbell et al. 1994;Leeman et al. 2004) are also shown for comparison. In (b), open fields and paths from Vengosh (2014); local thermal/nonthermal groundwaters (Cullen et al. 2015) and hydrothermal vents are also shown (Butterfield et al. 1994;Campbell et al. 1994;Fouquet et al. 1998;Gieskes et al. 2000;Von Damm et al. 2005) Leeman et al. (2004). ...
The chemical and isotope compositions of slab dehydration fluids from convergent margins have been theorized by many authors who have adopted several approaches. A direct collection of natural water is possible only in an oceanic environment, despite several difficulties in estimating the deepest component due to the mixing with seawater or hydrothermal fluids from the ridge. Accordingly, the study of melt inclusions is a valuable alternative. However, the latter mainly represents high temperature/pressure conditions in deep magmatic or metamorphic settings. Here, we present new H, O, Li and B isotope along with a revision of previously published chemical data from a potential natural example of slab dehydration water, sampled in a forearc region and affected by low-temperature metamorphism and serpentinization processes (Aqua de Ney, Northern California). Its extreme composition challenges the understanding of its origin and deep temperature, but this work is a further step on a topic of increasing interest for several scientists from different academic disciplines.
... Another diagnostic plot between δ 11 B and 1/B (B in mg/L) (Fig. 7) also shows two different clusters of the thermal waters. The representative regions in the Fig. 7 are taken from Awaleh et al. (2018) and Boschetti et al. (2015). As presented in Fig. 7, one group of samples from Dholera (DH-1, 2, 3), Badhiyad (BD-1), Lasundra (LS-1, 2), Tuwa (TA-1, 2, 3, 4, 5) and Tulsishyam (TS-1) region having elevated EC values show narrow variation of δ 11 B and 1/B values and fall near the seawater evaporation line thus confirming the presence of relics of evaporated seawater in these samples. ...
... These samples have distinct isotopic signature compared to that of the rainwater, basement groundwater, Na-HCO 3 waters of sedimentary origin or Na-HCO 3 waters contain methane of thermogenic origin. The boron isotope geochemistry of these group of samples can most likely be explained by the mixing of two or three end members: rainwater, Na-HCO 3 waters of sedimentary origin and seawater (Boschetti et al., 2015). Based on the previous discussions, influence agricultural return flow can be another contributing factor which had been established from the earlier studies in this region (Rina et al., 2014). ...
Cambay rift basin is the only geothermal province in India that hosts several saline thermal water manifestations having EC values varying from 525 to 10860 µS/cm. Various ionic ratios (Na/Cl, Br/Cl, Ca/ (SO4+ HCO3), SO4/Cl) as well as boron isotopic composition (δ11B = 40.5 to 46‰) clearly ascribes the presence of fossil (relics of evaporated seawater) seawater as origin of increased salinity in the majority of thermal waters. Depleted isotopic (δ18O, δ2H) composition of these thermal waters also substantiates the presence of paleowater in these systems. In rest of the thermal waters, agricultural return flow is found to be source of dissolved solutes as confirmed from different bivariate plots such as B/Cl vs. Br/Cl and δ11B vs. B/Cl as well as from ionic ratios. This study thus provides the diagnostic tools to elucidate the source of variable salinity in the thermal waters circulating in the Cambay rift basin, India.
... Another diagnostic plot between δ 11 B and 1/B (B in mg/L) (Fig. 7) also shows two different clusters of the thermal waters. The representative regions in the Fig. 7 are taken from Awaleh et al. (2018) and Boschetti et al. (2015). As presented in Fig. 7, one group of samples from Dholera (DH-1, 2, 3), Badhiyad (BD-1), Lasundra (LS-1, 2), Tuwa (TA-1, 2, 3, 4, 5) and Tulsishyam (TS-1) region having elevated EC values show narrow variation of δ 11 B and 1/B values and fall near the seawater evaporation line thus confirming the presence of relics of evaporated seawater in these samples. ...
... These samples have distinct isotopic signature compared to that of the rainwater, basement groundwater, Na-HCO 3 waters of sedimentary origin or Na-HCO 3 waters contain methane of thermogenic origin. The boron isotope geochemistry of these group of samples can most likely be explained by the mixing of two or three end members: rainwater, Na-HCO 3 waters of sedimentary origin and seawater (Boschetti et al., 2015). Based on the previous discussions, influence agricultural return flow can be another contributing factor which had been established from the earlier studies in this region (Rina et al., 2014). ...
Cambay rift basin is the only geothermal province in India that hosts several saline thermal water manifestations having EC values varying from 525 to 10,860 μS/cm. Various ionic ratios (Na/Cl, Br/Cl, Ca/(SO4 + HCO3), SO4/Cl) as well as boron isotopic composition (δ11B = 40.5 to 46 ‰) clearly ascribes the presence of fossil (relics of evaporated seawater) seawater as origin of increased salinity in the majority of thermal waters. Depleted isotopic (δ18O, δ2H) composition of these thermal waters also substantiates the presence of paleowater in these systems.
In rest of the thermal waters, agricultural return flow is found to be source of dissolved solutes as confirmed from different bivariate plots such as B/Cl vs. Br/Cl and δ11B vs. B/Cl as well as from ionic ratios. This study thus provides the diagnostic tools to elucidate the source of variable salinity in the thermal waters circulating in the Cambay rift basin, India.
... Results were compared to previously published chemical and isotopic geothermometers specific for sedimentary brines (Boschetti et al., 2015;Kharaka and Mariner, 1989;Sanjuan et al., 2014). The calculated activity of the dissolved constituents was also used to calculate the saturation index of a carbonate solid solution made of calcite, magnesite, rhodochrosite, siderite and strontianite by EQ3/6 code, version 8 (Wolery and Jarek, 2003). ...
... This could be due to a higher δ 11 B value in Cretaceous seawater (up to 3‰ higher than the present; Lemarchand et al., 2002), together with a fractionation effect due to evaporation up to halite Table 1 Physicochemical parameters, major ion composition, trace elements concentration, and isotopic results from saturation (approximatively +4‰) (Vengosh et al., 1992). Actually, by subtracting a value of 7‰ from the original values of the brines, a mean temperature of 64 ± 6 • C was obtained from the boron isotope geothermometric equation (Boschetti et al., 2015), which matches with that obtained by the calcite-dolomite-chlorite-kaolinite equilibria. ...
This paper focuses on the geochemical composition and isotope geochemistry of brines in the Cenomanian–Turonian carbonate Mishrif reservoir of southern Iraq. Main dissolved constituents, trace elements, δ2H and δ18O, 87Sr/86Sr, mineral saturation indices and thermodynamic calculations were investigated in formation waters from the Mishrif Formation to obtain a better understanding of brine evolution and diagenetic effects over geological time. Previous published δ11B data were also reinterpreted as a geothermometer tool. The results are compared with previous published data for local oilfields and coeval formations in the Arabian Gulf. The Mishrif brine has a marine origin and is diagenetically modified to Ca-excess and Na-deficit. Formation waters are quartz supersaturated and are in equilibrium with chalcedony and calcite-dolomite in the temperatures range of 50–75 °C, which is also confirmed by calcite-water oxygen isotope fractionation and δ11B geothermometer. The potential role of clays in conditioning brine chemistry during diagenetic processes was highlighted by activity diagrams; in particular,
their adsorption/exchange effect on sodium could explain the lower temperature obtained by the Na/Li geothermometer (42 ± 6 °C). The δ2H and δ18O values show that oxygen isotope composition of the brines was isotopically more affected by interaction with limestone during diagenesis than seawater evaporation. The main effect is an 18O-enrichment on the brine starting from the SMOW value. Locally, dilution by present-day meteoric water was also detected (Rumaila South), which is shifted towards the local meteoric water line. The strontium isotope ratios range from 0.707713 to 0.707749 and correspond to a marine strontium of late Cenomanian–early Maastrichtian age, except for the Majnoon sample, which shows a more radiogenic value (0.708043). Radiogenic
strontium and gypsum and anhydride saturation indices of the Majnoon sample could indicate the contribution of calcium and sulphate from the strontium-rich sulphate minerals of the Cambrian salt domes occurring in the oilfields of southern Iraq. The higher manganese concentration (4 mg/l) and the slightly higher temperature inferred by geothermometers (up to 74 °C) in comparison with present-day could indicate that the Majnoon brine is a hot fluid, probably related to a deeper structure such as the Zagros Foredeep Fault.
... While the distinctive sample clustering and trends in Fig. 3 and the fact that the heavy isotope enriched waters are also the most chloride enriched (RG1, E3bis, and RG3) are suggestive, water isotope versus chloride plots could furnish a greater distinction between freshwaterseawater mixing and evaporation because arid climate groundwater samples have similar paths in a δ 18 O versus δ 2 H binary diagram (Fig. S11 in Supplementary Materials, Boschetti et al., 2015aBoschetti et al., , 2015b. Two things are clear from these diagrams: i) the more saline C1 waters (e.g., RG1 and E3bis) and the AM groundwaters (Houmed-Gaba, 2009), tapped at about 40-45 m depth, have the same origin and/or may have undergone similar salinization processes, and ii) sample RG3 was affected by both evaporation and mixing with seawater. ...
... In (B), fields and paths are from Vengosh (2014); dotted lines represent the mixing between seawater and hydrothermal waters. In (C), fields are as in Boschetti et al. (2015a) and references therein. Following Louvat et al. (2011), the coastal rainwater field was extended to δ 11 B = 45‰. ...
The complex Djibouti volcanic aquifer system was studied to improve understanding of the recharge conditions of the Awrlofoul low-enthalpy geothermal system located in the middle of the aquifer. Forty-four thermal and non-thermal groundwater samples were analyzed to determine their major chemical compositions, trace element compositions, and multi-isotopic compositions (δ2H(H2O), δ18O(H2O), δ18O(SO4), δ34S(SO4), δ13C(DIC), 14C, 87Sr/86Sr, δ11B, δ15N(NO3−), and δ18O(NO3−)). Statistical analysis (Hierarchical Cluster Analysis and Principal Component Analysis) of chemical composition identified three main water groups, two affected by salinization (C1 and C2) and one fresh water group useful for drinking (C3). The latter group includes thermal water from the Awrlofoul geothermal field. This separation into three different water groups is also clear on a Langelier-Ludwig plot and is confirmed by analysis of historical chemical data over the last 30 years. The main causes of salinization are contamination of the fresh groundwater either by recent seawater intrusions (C2) or mixing with Ca-Cl fossil saline water (C1). The C1 waters are also highly affected by Mg/Ca-Na clay exchange. As expected, the 11B/10B isotope ratio of the intruded salt water, both recent and fossil, was much higher than that of seawater (δ11B up to +55‰). Unexpectedly, groundwater of meteoric origin (i.e., unaffected by a seawater intrusion), also showed a δ11B higher than that of seawater (46.3‰ < δ11B < 51.3‰). That the unexpectedly high δ11B values are likely due to 10B sequestration resulting from interaction with clay and/or carbonate precipitation is demonstrated by activity diagrams and saturation indices. The C1 water group is also affected by nitrate contamination (56.8 ± 19.2 mg/l). That the nitrate contamination is likely due to manure contamination is indicated by comparing the dual isotopic composition of nitrate to the boron isotope ratios. The isotopic composition of sulfate highlighted the importance of SO2-disproportionation to the local sulfate minerals that interacted with the meteoric recharge, while the strontium isotope ratios showed the importance of the seawater-basalt interaction with the fossil saline water component. The results of the mixing analysis using chemical composition, δ13C(DIC), and 14C data by geochemical software (NetpathXL) confirmed the presence of ternary mixing with at least three sources (seawater, meteoric, and fossil) in the waters with the highest chloride concentrations. The estimation of groundwater age by 14C was complicated by overexploitation (as testified by the lumped parameters approach). However, the fossil saline water component was dated back to the Holocene Humid Period.
To estimate the temperature of the Awrlofoul low-enthalpy geothermal system, a multi-method geothermometric approach was applied. Chemical (mainly SiO2) and isotope (sulfate-water oxygen fractionation) geothermometers were employed together with multiple mineral equilibria. These different geothermometric approaches estimated a temperature range of 102 °C–140 °C for the geothermal reservoir, with a mean temperature of about 110 °C.
Finally, a conceptual model was proposed for the Awrlofoul low-enthalpy geothermal system on the basis of the geochemical and isotopic data of the thermal and non-thermal groundwaters combined with the geology and hydrogeology of the study area.
... DOI: 10.1016DOI: 10. /j.marpetgeo.2016 13 Boron has great potential to be used as a geothermometer in sedimentary basins. However, applicability of a boron geothermometer is precluded when seawater-derived formation waters are diluted by meteoric waters (Boschetti et al., 2015b). Combining the 11 B-T°C and 1/B-T°C equations inferred by Boschetti et al. (2015b), it is possible to relate the boron concentration to temperature in formation waters: ...
... However, applicability of a boron geothermometer is precluded when seawater-derived formation waters are diluted by meteoric waters (Boschetti et al., 2015b). Combining the 11 B-T°C and 1/B-T°C equations inferred by Boschetti et al. (2015b), it is possible to relate the boron concentration to temperature in formation waters: ...
Free water and water in emulsion with oil from hydrocarbon wells onshore-offshore Lake Maracaibo were extracted and analyzed. The use of classical and new chemical diagrams evidenced that Na-HCO3 and Na- Cl are the main chemical facies, whereas Na-SO4 facies was rare and revealed only in faulted areas in which shallow groundwater was involved in deep circulation. Cretaceous Ca-Cl waters were not revealed, but their imprint on some samples was traced and evidenced by Langelier-Ludwig, Brine-Differentiation and Caexcess vs. Nadeficit diagrams. These square plots, allowing a discrimination between the water contributions from the
different source rocks, should be more exploited as hydrogeochemical tools in hydrocarbon exploration. Original data on monocarboxylic anions showed acetate concentration higher than ten times that of formate at sampling conditions, but speciation under deep conditions indicated a reversed activity dominance. Calculation of saturation indexes and kinetic modeling showed an active precipitation of chalcedony, kaolinite and clays, especially where the temperature was lower (T < 100 °C). Formation waters and lake water showed quite similar chloride concentration and hydrogen isotope composition. However, thermodynamic
calculations at the oilfield P-T conditions revealed chlorite and illite, produced during previous diagenetic stages of Misoa sandstones, recrystallization to smectite and vermiculite in present-day stage. The diagenetic water produced in these reactions could have enriched the delta18O isotopic composition of approximately +2‰. This isotope diagenetic effect was more evident in Na-HCO3 waters, which also showed a decrease in chloride at constant boron as a consequence of clay dewatering. In this regard, a new boron geothermometer useful for formation waters is also proposed.
... ‰ to δ 18 O(H 2 O) = 0 ‰. The former value is the isotope ratio of stable oxygen in primary magmatic water (Awaleh et al., 2017) or a local evaporated brine (Boschetti et al., 2011a;Boschetti et al., 2015) and the latter is the typical value of the present-day seawater as V-SMOW in permil. However, it is known that Jurassic paleo-seawater had no significant variation from zero, also considering the paleolatitude of the study area (Alberti et al., 2020;van Hinsbergen et al., 2015;Jaffrés et al., 2007). ...
... Here, it can be seen that the water in the pressure zones (transition zone) is brackish-type water. Boschetti (2011) and Boschetti et al. (2014) have examined the characteristics of the water in pressure zones in their study in detail. According to these results, the consequence that the hydrodynamic and hydrostatic zones of the Chebotarev classification are quite successful, is obtained. ...
In the wildcat sedimentary basin which will be explorated oil and gas, to increase the possibility discovery of find of commercial oil and gas must be benefit from approximately 90 years of experience in petroleum hydrogeology. These methods provide considerable simplicity especially in geological and geophysical surveys on illuminating subsurface geology. The HYDROPET is a new computer software was developed by authors to contribute to oil and gas exploration, especially in geologically complex and wildcat sedimentary basins. The program is developed with chemical and isotopic classification, analysis and interpretation methods proposed by a large number of different researchers based on water chemistry analysis data.This study includes test results in known oil and gas production fields that composed of different and complex geological structures. Results of the program and the data of the known oil and gas production fields are same. Program allows basin/field-scale interpretation based on water chemistry data show that especially in geologically complex and wildcat sedimentary basins, location of oil and gas deposits and properties of petroleum geology and subsurface geology can be estimated with high accuracy.
Keywords: oil and gas exploration, oilfield waters, formation waters, hydrogeology, hydrochemistry, wildcat sedimentary basin, HydroPet computer program
... The Hydrocalculator software, version 1.03 , was used to perform the isotope evaporation models. The boron and strontium isotope ratio analyses were performed on 0.45-μm-filtered sample water by negative thermal ionization mass spectrometry (N-TIMS at Tetra Tech, Fort Collins, Colorado; e.g., Boschetti et al. 2015) and multi-collector thermal ionization mass spectrometry (MC-TIMS at Isotope Science Laboratory, University of Calgary, Calgary, Alberta, Canada; e.g., Elhamel 2014), respectively. In both cases, an ion exchange method was used to purify the target element from the sample background. ...
The examination of past and new chemical–isotopic data (2H/1H–18O/16O,
11B/10B and 87Sr/86Sr ratios) shows the meteoric origin of the Sawa Lake (Muthanna
Governorate, Iraq) and its connection with the local aquifers, which feed the lake via the
groundwater emerging from its floor through fault systems. The chemical and isotopic
evaporation models are traced by geochemical computer codes by using a different composition
of some potential inflows to the lake (e.g., the Euphrates River and Dammam aquifer).
The main product of the chemical evaporation models is gypsum, as confirmed by the
mineralogical examination of the sediment and the surrounding outcrops. A strong 18O–2H
enrichment is a consequence of the evaporation effect in arid regions; δ18O–Cl models and
δ11B = + 23.4‰ exclude the contribution of any seawater-derived fluids. This latter value
along with 87Sr/86Sr = 0.707989 suggests a mixed origin from the Eocene–Miocene aquifers.
The isotope and chemical evaporation paths from the meteorically recharged sources
match the lake composition. However, compositional switches from NaCl toward MgCl2
occurred in the last decade and are related to post-drought periods, showing that the interaction
of the recharging waters with the local soils (Na–Mg exchange and/or the leaching
of the top layer salts) have a role in the chemical composition. This demonstrates that the
lake is significantly influenced by climatic variations
... In the past, B isotopic compositions of evaporites and brines have been used to trace paleosalinities and to reconstruct marine and non-marine depositional environments (Palmer and Slack, 1989;Qi et al., 1989;Vengosh et al., 1991Vengosh et al., , 1992Vengosh et al., , 1995Xiao et al., 1992;Palmer and Swihart, 1996;Jiang, 2000;Liu et al., 2000;Kloppnam et al., 2001;Paris et al., 2010;Tan et al., 2010;Zhang et al., 2013). Similarly, the origin and geochemical evolution of brines, groundwater, hot springs, and salt sediments have been evaluated based on B isotopic compositions and elemental concentration ratios (Vengosh et al., 1991(Vengosh et al., , 1995(Vengosh et al., , 1998(Vengosh et al., , 1999(Vengosh et al., , 2007Xiao et al., 1992;Li et al., 2013;Ma et al., 2015;Lv et al., 2014;Boschetti et al., 2015;Awaleh et al., 2017). In addition, over the past two decades, B isotopic compositions of marine biogenic carbonates (e.g., corals and planktonic foraminifer shells) have been regarded as an indicator to reconstruct the pH value of paleoseawater (Hemming and Hanson, 1992;Hönisch and Hemming, 2004;Hönisch et al., 2004;Ke et al., 2015). ...
In this study, nineteen brine samples from the Qarhan Salt Lake (QSL) in western China were collected and analyzed for boron (B) and chlorine (Cl) concentrations, total dissolved solids (TDS), pH values and stable B isotopic compositions. The B concentrations and δ¹¹B values of brines in the QSL range from 51.6 to 138.4 mg/L, and from +9.32‰ to +13.08‰, respectively. By comparison of B concentrations and TDS of brines in QSL with evaporation paths of brackish water, we found that B enrichment of brines primarily results from strong evaporation and concentration of Qarhan lake water. Combining with comparisons of B concentrations, TDS, pH values and δ¹¹B values of brines, previously elemental ratios (K/Cl, Mg/Cl, Ca/Cl, B/Cl) and δ¹¹B values of halite from a sediment core (ISL1A), we observe good correlations between B concentrations and TDS, TDS and pH values, pH and δ¹¹B values of brines, which demonstrate that higher B concentrations and more positive δ¹¹B values of halite indicate higher salinity of the Qarhan paleolake water as well as drier paleoclimatic conditions. Based on this interpretation of the δ¹¹B values of halite in core ISL1A, higher salinity of the Qarhan paleolake occurred during two intervals, around 46–34 ka and 26–9 ka, which are almost coincident with the upper and lower halite-dominated salt layers in core ISL1A, drier climate phases documented from the δ¹⁸O record of carbonate in core ISL1A and the paleomoisture record in monsoonal central Asia, and a higher solar insolation at 30°N. These results demonstrate that the δ¹¹B values of halite in the arid Qaidam Basin could be regarded as a new proxy for reconstructing the salinity record of paleolake water as well as paleoclimate conditions.
The relevance of the study is caused by the lack of effective indicators to date that allow classifying fluid systems in accordance with their substance composition, geological settings and dynamics of fluids discharge to the earth's surface. Studies of the chemical and isotopic composition of the water from fluid systems will make it possible to determine the commonality and differences in origin of fluid systems of different types, as well as to describe the main geochemical processes occurring in them. This is necessary for theoretical understanding of the mechanisms and patterns of activity of different fluid systems. Problems of hydrogeochemical classification are also of great practical importance, since different fluid systems imply various scenarios for development of hazardous geological processes associated with them. Apart from that, some fluid systems are associated with the generation and migration of hydrocarbons, which can be used as one of the prospecting signs in exploration. The aim of the study is to determine possible indicators for recognizing fluid systems of different types using hydrogeochemical characteristics. Objects: waters from different systems of focused discharge of subsurface fluids - Hydrocarbon Sedimentary (mud volcanoes and thermomineral springs), Sediment-Hosted Hydrothermal (geothermal seepage of the Salton Sea and Lusi) and Volcano & Hydrothermal Geothermal (mud pools and hydrotherms on magmatic volcanoes). Methods. Concentrations of the main anions (Cl- , Br- , SO4 2- ) and cations (Li+ , Na+ , K+ , Ca2+, Mg2+) in the studied waters were determined by the method of ion chromatography; HCO3 - concentration was determined by the titrimetric method; the boron content was determined by the spectrophotometric method. The isotopic composition of waters ([delta]18O, [delta]D) was determined by infrared laser spectrometry. Subsequent processing of hydrogeochemical data was done using the methods of mathematical statistics. The comparative study of waters from fluid systems of different types was conducted using the generally accepted geochemical diagrams. Results. The present paper is a comparative study of a wide range of hydrogeochemical indicators of fluid systems - Hydrocarbon Sedimentary, Sediment-Hosted Hydrothermal, and Volcano & Hydrothermal Geothermal. It was found that these indicators for the studied groundwater have a wide range of values. Consequently, for some fluid systems there is no clearly pronounced differentiation according to the analyzed physico-chemical parameters. In particular, no significant differences were found in chemical composition of the waters from mud volcanoes and the Sediment-Hosted Hydrothermal System Lusi. It does not allow solving the problem of recognition of these fluid systems using only hydrogeochemical characteristics, or casts doubt on the correctness of antecedent statements about their different origin. At the same time, Volcano & Hydrothermal Geothermal systems are characterized by unique hydrogeochemical properties that differ significantly from other types of fluid systems. The most informative signs for these fluid systems are the pH, which mainly varies from ultra acidic to acidic values, and the geochemical type of waters, characterized by a mixed cationic composition with a high content of aluminum and iron. In addition, the waters of most of the studied fluid systems are characterized by high content of boron and lithium, but their concentration ranges often overlap. At the same time, the sources of these chemical elements for the fluid systems of the regions of modern magmatic volcanism differ from the fluid systems associated with sedimentary basins. The results obtained indicate the need to revise the existing geochemical classifications of fluid systems.
Among natural hazards, mud volcanoes can damage property and infrastructures and affect hillslope evolution at different spatial and temporal scales. The results of 10-year-long multidisciplinary investigations performed on a Roman-age archaeological site, La Rovina di Montegibbio, are presented, showing a peculiar example of mutual interplay between human settlement and geological forcing in the mud-volcanic environment. The site (350 m a.s.l.) lies at the termination of the upper Secchia River catchment, near the town of Sassuolo (Modena Province). Here, a 4-km-long mud volcano belt borders the Apennines chain front, comprising one of the most prominent mud volcanoes of Italy (Salsa di Montegibbio), and the still-active chain hinge tectonics gives origin to gas and oil seeps. Based on geological, geoarchaeological, palaeobotanical, geochemical, geophysical records and analytical data, we unravel the onset, the evolution and the abandonment of the settlement in relation to the existence of a previously unknown mud volcano, belonging to the larger Montegibbio mud volcano system. The damages affecting the Roman-age buildings record the ground deformations in the context of mud volcano tectonics. In particular, the pattern of faults set buried under the archaeological site is shown and compared with that of the main mud volcano conduit. At least two Roman-age eruptive episodes have been recorded, whose ejected muds are geochemically characterized. The first recorded eruption must be regarded as the reason for the initial location and function of the sacred ancient settlement. The final site abandonment was because of subsequent severe ground deformations affecting the hillslope as a consequence of mud volcano activity.
The goal of this study is to analyze fluid geochemistry, boron isotope and gas data to reassess the formation and evolution processes of the Changbaishan volcanic geothermal system (Jilin, China). Due to the presence of hot fumaroles (with temperatures of higher than 100 °C) and sinters, we believe that phase separation is occurring underground, which is also indicated by the characteristics of the B and gas data. Based on their hydrochemical data and B/Cl ratios, the thermal water samples in this area can be divided into three groups: 1) group 1 is steam-heated/condensate water (group 1-1: JJ, JLQ; group 1-2: SBDG, XRQ); 2) group 2 is karst water (CR3 and LSD); and 3) group 3 is residual water (CR1 and CR2). The preliminary discrimination of samples using B and gas data implies that group 1-1 around the crater is controlled by a second phase separation process, which is induced by the input of hot magmatic material; group 1-2 in the basin area is controlled by the transformation of clay minerals, and the XRQ water sample shows contamination by sewage; group 2 represents karst water that has leached metamorphic rock and been directly heated by the input of hot magmatic volatiles; and group 3 is the result of one seawater phase separation process. The mixing and fluid-rock interaction models based on the mass balance of boron concentration and isotope imply that the phase separation and input of magmatic volatiles are more important than fluid-rock interactions in the formation of the Changbaishan geothermal system, and the first phase separation process in the deep carbonate reservoir occurred in a late stage, with approximately 75%–87.5% of water becoming vapor. Additionally, the Rayleigh distillation of B isotope implies that new magma is being generated below this area, with the low B concentrations and high boron isotopic values of its gases implying that the mixed component may be derived from the subducted Pacific plate (e.g., marine sediment). The addition of “excess heat” due to the continued subduction of the Pacific plate has further encouraged the phase separation process, and the subduction process has also accelerated the transition of the hydrothermal system into a non-hydrothermal system.
Özet: Hatay Bölgesi petrol potansiyelini berlirlemek amacıyla çeşitli su sınıflama sistemleri tarafımızdan yazılmış olan Hydropet programı ile tek bir çatı altında toplanmıştır. Literatürden derlenen hidrojeokimyasal veriler Hydropet programında değerlendirilmiştir. Yazılım kullanılması petrol arama yöntemlerine ışık tutacağı ve arama işlemlerinde daha hızlı sonuca gidilebileceği tespit edilmiştir. Program ile elde edilen veriler ışığında farklı hidrojeokimyasal sınıflamalara göre su sınıflandrımaları farklı şartlarda kullanılarak hidrokarbon yönüyle değerlendirilmiş ve bölgenin petrol potansiyeli ortaya konulmuştur. Program ile ortaya çıkan veriler ışığında bölgedeki petrol potansiyelinin aramaya değer olduğu tespit edilmiştir.
To evaluate ion origins and fluid behavior, the chemical properties of thermal water sampled from the Eocene reservoir in the Yitong Basin (YB), Northeast China, were investigated. The thermal water samples are classified as Na–HCO3-type water and were fully equilibrated, except for Sijixiangkang (SJXK) and Yitong (YT). The cations originate mainly from water–rock interactions (e.g., albitization and weathering of plagioclase), while the anions originate from magmatic volatiles and leaching of limestone and granite, which were heated by hot magmatic volatiles and exhibited an evaporation-like pattern in the Gibbs diagrams. The existence of magmatic volatiles was verified by the high ion ratio, the minor-element origins, δ¹³C values of HCO3, and δ³⁴S values of SO4, which flowed upward along lithospheric faults, with higher fluxes in the northeast than in the southwest (the δ¹³C value of the Chaluhe depression (CD) is 0.93‰ lower than that of the Moliqing depression (MD, 1.63‰)). Furthermore, according to the Br/Cl and HCO3⁻/Cl ratios and the δ¹³C values, we speculate that a deep Permian limestone reservoir exists below the granitic unit. Based on the ion origins and fluid potentials, we conclude that the CD and MD are open systems rather than closed systems. The recharged water migrates from the margin to the center in the plane, and in the vertical direction, it migrates from the Yongji (E2y) and Sheling (E2sh) strata to the overlying strata and underlying Shuangyang (E2s) strata along faults. By summarizing all of the available data, we proposed a conceptual model of fluid migration.
Mud extrusion is a well-known phenomenon whereby fluid-rich, fine grained sediments ascend within a lithological succession due to their buoyancy. In this study of the terrestrial mud volcanism associated to an active thrusted area in the northern Apennines, we investigated the effect of boron incorporation in illite crystalline lattice. A significant variation was recorded on the investigated mud samples with respect to both the amount of fixed boron (118–529 μg/g) and the full width at half-maximum height value (FWHM) of illite (0.29–0.62°Δ 2Θ). We attribute these variations to the interaction between boron-rich formation waters and the silty-clayely lithologies of the local sedimentary succession. The lack of any geographical correlation between the selected geochemical and mineralogical parameters is likely due to intensive thrust and fold deformation of the study area. Comparison of FWHM values with those from Dellisanti et al., (2008; Santerno succession, northern Apennine) lead us to suggest that application of FWHM as a depth indicator could be misleading within B-rich hydro-geological environments.
The International Atomic Energy Agency (IAEA), in cooperation with the
World Meteorological Organization (WMO), has been conducting a
world-wide survey of hydrogen (2H/1H) and oxygen
(18O/16O) isotope composition of monthly
precipitation since 1961. At present, 72 IAEA/WMO network stations are
in operation. Another 82 stations belonging to national organizations
continue to send their results to the IAEA for publication. The paper
focuses on basic features of spatial and temporal distribution of
deuterium and 18O in global precipitation, as derived from
the IAEA/WMO isotope database. The internal structure and basic
characteristics of this database are discussed in some detail. The
existing phenomenological relationships between observed stable isotope
composition of precipitation and various climate-related parameters such
as local surface air temperature and amount of precipitation are
reviewed and critically assessed. Attempts are presented towards
revealing interannual fluctuations in the accumulated isotope records
and relating them to changes of precipitation amount and the surface air
temperature over the past 30 years.
In some coalbeds, naturally occurring water pressure holds methane—the main component
of natural gas—fixed to coal surfaces and within the coal. In a coalbed methane
(CBM) well, pumping water from the coalbeds lowers this pressure, facilitating the release
of methane from the coal for extraction and use as an energy source. Water pumped from
coalbeds during this process—CBM “produced water”—is managed through some combination
of treatment, disposal, storage, or use, subject to compliance with federal and state
regulations.
This paper presents new chemical data of hydrocarbon-rich gases discharged from mud volcanoes and CH4-rich emissions located in different areas of Italy (Northern Apennines and Sicily). The determination of C5–C10 alkanes, cyclics and aromatics was carried out by GC–MS, while the main gas species and C1–C4 hydrocarbons were analyzed by GC-TDC and GC-FID, respectively. Methane is by far the most abundant component of all the investigated gas emissions, with the exception of part of those discharging close to Mt. Etna volcano, which are CO2-rich. The gas samples collected from the Emilia Apennine and Sicily show δD–CH4 and δ13C–CH4 values typical of thermogenic gases. Most gases from the Romagna Apennine discharge methane with a biogenic isotopic signature. Non-methane hydrocarbons of biogenic gases are almost exclusively C2–C4 alkanes, with minor amounts (fraction of μmol/mol) of C4 + compounds, including few aromatics and cyclics, likely deriving from minor thermogenic contribution not evidenced by the δ13C–CH4 and δD–CH4 values. The Etnean gases, whose R/Ra and δ13C–CO2 values indicate a strong contribution from a hydrothermal fluid source related to the nearby volcanic system, show a significant enrichment of aromatics compounds (up to 36% of the non-methane organic gas fraction), which is likely produced by catalytic reforming processes, such as dehydrocyclization of alkanes.The thermogenic gases from the Apennines and southwestern Sicily are characterized by the presence of more than 20 different cyclic compounds with concentrations up to several μmol/mol. Cyclic compounds are likely formed by i) thermal cracking and ii) uncompleted aromatization of alkanes occurring at depth > 3 km and temperatures not exceeding 120–150 °C.
Boron (B) and chlorine (Cl) are widely distributed on the Earth's sur- face and show distinctive geochemical behaviors. Cl behaves rather conser- vatively in oceanic environments while B is an excess-volatile and its distri- bution is sensitive to sediment absorption and organic matter degradation. The distribution of B, Cl and their isotopes in pore waters provide useful information for distinguishing between shallow circulation and deep origin fluid sources. Thirty-six sediment cores 0 - 5 m in length were sampled from a foreland accretionary prism offshore Southwestern Taiwan where strong bottom simulating reflectors (BSRs) and an abundance of mud dia- pirs were discovered. More than 350 pore water samples were separated and analyzed for B, Cl and other major ions. Four long cores were selected for B and Cl isotopic analysis. We found that the Cl in all cores varied less than 10%, suggesting no major hydrate dissolution or formation involve- ment at shallow depths in the study area. However, the B concentration changed greatly, ranging between 360 and 650 µM , indicating a possible sedimentary contribution during the early diagenesis stage. The B isotopic compositions were relatively depleted (~25 to 37 0 00) in these pore waters, implying the addition of sedimentary exchangeable B with low δ 11B. The Cl isotopes showed rather large variations, more than 8 0 00, possibly related to the addition of deep situated fluids. In summary, the chemical and isoto- pic characteristics of pore waters separated from piston cores off South- western Taiwan suggest strong influence from organic matter degradation
The relations between mud volcanism and active tectonic strainwere investigated at the Nirano mud volcano field (NMVF), nearthe active Pede-Apennine thrust front of the Northern Apenninesthrust-and-fold belt (Italy). Active fluid release occurs throughnumerous vents within an elliptical depression developed overthe crest of a thrust-related anticline. This depression isinterpreted as a caldera collapse-like structure thatmay have developed in response to the deflation of a shallowmud chamber triggered by eruption and sediment fluid evacuationevents. Like many volcanic calderas, the NMVF caldera is elongatednearly parallel to the direction of least horizontal compressivestress Sh, and is thus deduced to reflect the regional tectonicstress axes. It is concluded that mud volcano calderas exhibitmechanical similarities to the igneous analogs, and that themethods used in this first test could be applied to other calderasimaged by seismic data and in the field.
Analysis of total dissolved boron and boron isotopes for interstitial
waters from recent Ocean Drilling Program drill cores in two
accretionary prisms indicates an efficient return to the ocean of
exchangeable boron of subducted sediments via pore-fluid expulsion. This
source of boron helps to balance the ocean sinks, but a complete balance
of the ocean budget requires deeply subducted boron to be returned
efficiently to the oceans via explosive arc volcanism.
Late Miocene to Quaternary volcanic rocks from the frontal arc to the back-arc region of the Central Volcanic Zone in the Andes show a wide range of δ11B values (+4 to −7 ‰) and boron concentrations (6 to 60 ppm). Positive δ11B values of samples from the volcanic front indicate involvement of a 11B-enriched slab component, most likely derived from altered oceanic crust, despite the thick Andean continental lithosphere, and rule out a pure crust-mantle origin for these lavas. The δ11B values and boron concentrations in the lavas decrease with increasing depth of the Wadati-Benioff Zone. This across-arc variation in δ11B values and decreasing B/Nb ratios from the arc to the back-arc samples are attributed to the combined effects of boron-isotope fractionation during progressive dehydration in the slab and a steady decrease in slab-fluid flux toward the back arc, coupled with a relatively constant degree of crustal contamination as indicated by similar Sr, Nd and Pb isotope ratios in all samples. Three-component mixing calculations for slab-derived fluid, the mantle wedge and the continental crust based on B, Sr and Nd isotope data indicate that the slab-fluid component dominates the boron composition of the fertile mantle and that the primary arc magmas were contaminated by an average addition of 15 to 30% crustal material. Modeling of fluid-mineral boron-isotope fractionation as a function of temperature shows that dehydration reactions liberate continuously changing fluid compositions from the slab during progressive subduction. A combination of a boron-isotope fractionation model and a temperature model for the Central Andean subduction zone fits the across-arc variation in δ11B and we conclude that the boron-isotope composition of arc volcanic rocks, especially in island arcs, is dominated by changing δ11B-composition of boron-rich slab-fluids during progressive dehydration. Owing to the decrease in slab-derived fluid flux crustal contamination becomes more important toward the back-arc. Because of the boron-isotope fractionation effect, across-arc variations in δ11B need not necessarily reflect different mixing proportions between boron derived from the slab-fluid and the mantle wedge.
Natural seeps in the Northern Apennines document a variability of fluids and reservoirs in terms of origin, age and evolution. Their spatial distribution appears controlled by the presence or absence of the tectonic overburden provided by the Ligurian nappe. The general trend of deepening of the Mesozoic basement toward the internal part of the thrust belt is reflected by the nature of the seeps, characterized by thermogenic methane and oil at the foothills, whereas the innermost seeps show occurrence of dry thermogenic gas suggesting overcooking of the residual oil. At the front of the Ligurian nappe, or in places never covered by it, the seepages are associated with biogenic methane related to bacterial degradation of the organic-rich intervals occurring in the Pliocene and Pleistocene marine succession. The coupling of geochemical and structural analysis allows reconstructing the tectono-thermal evolution of the belt, improving our knowledge on the processes acting within the reservoir and controlling important parameters of the petroleum system, such as the reservoir porosity and its modifications, and the migration patterns.
In natural resource exploration, Ca–Cl basinal brines are important for understanding the origin and spatial and temporal distribution of hydrocarbons and sedimentary ore deposits. Little attention has been paid to the possible connection between fossil basinal brines and paleo-seawaters and to the implications for reconstructing paleoseawater compositions. Secular variations of Ca/Mg and Ca/Sr ratios in seawater have been documented mainly using fluid inclusions in halite, calcareous fossils and mineral analyses.
However, brines and other sedimentary records connected to paleo-seawater or its evaporated residues may be chemically affected by burial diagenesis or the effects of continental waters of meteoric origin, thus complicating interpretations of the analytical results. To investigate these effects on fluids and minerals related to the Messinian salinity crisis of the Mediterranean basin, we re-evaluate published data from: (1) brackish-to-brine waters from onshore (Northern Apennine foredeep; Levantine basin) and offshore (porewaters from the Deep Sea Drilling Project); (2) Messinian parental seawater deduced from calcareous fossils, fluid inclusions and sulfate minerals; (3) meteoric waters dissolving evaporites. The compositional trends related to seawater evaporation, diagenesis and mixing that affect the Ca/Mg and Ca/Sr molar ratios of the basinal brines are effectively discriminated on a binary plot depicting the proper fields for seawater and meteoric derived fluids. Brines showing stronger dolomitization start from Ca/Mg and Ca/Sr molar ratios of Messinian seawater deduced from the published analysis of fluid inclusions and open ocean fossils, that are therefore here validated ex post.
Examination of boron isotopes, elemental B, Br, and Li in brines, and coprecipitated salts during fractional evaporation of sea water shows that Br, Li, and B in the evaporated sea water have lower concentrations than expected, as determined from mass-balance calculations. The deficiency is found beyond a degree of evaporation of ˜30 and is associated with a gradual increase in the delta11B values of the evaporated sea water, from 390/00 to 54.70/00 (relative to standard NBS 951). The high delta11B values of the brines and the relatively lower delta11B values of the coexisting precipitates (MgSO4 and K-MgSO4 salts; delta11B = 11.40/00 to 36.00/00) suggest selective uptake of 10B by the salts. Applying Rayleigh distillation equations, the empirical fractionation factors for the depletion of the salts in 11B are estimated as 300/00 (alpha = 0.969) for the early stages of precipitation (gypsum and halite range) and 200/00 (alpha = 0.981) for the late stages (K-MgSO4 minerals). Coprecipitation of B(OH)4- species with the salts, and/or precipitation of Mg-borate minerals with a coordination number of 4 are the proposed mechanisms for boron isotope fractionation during fractional evaporation of sea water. The boron isotope composition of sea water (delta11B = 390/00) is significantly higher than that of continental water (delta11B = -30/00 ±50/00). Our study shows that salt deposits may be depleted in 11B by 200/00 to 300/00 relative to their parent brines. These variations suggest that boron isotopes can be used to determine the origin (marine vs. nonmarine) of brines and ancient evaporitic environments.
Na-carbonate (NaCW) waters are not concentrated in well defined areas, but usually widespread in areas where other water types (e.g., Ca-carbonate) are dominant. NaCW are the product of long-term water-rock interaction with dissolution of Na-silicates in presence of phyllosilicates, silica phases, and calcite. NaCW circulating in calcite-bearing sediments very probably have a Ca-carbonate parent with moderate to low P CO 2 , which changes its composition assuming increasing Na character as the water-rock interaction proceeds. However, the moderate to low P CO 2 values of the potential parent Ca-carbonate waters do not account for the high Na content of many NaCW. The higher P CO 2 required may be due to oxidation of organic matter of the sediments and, perhaps, to further addition of CO 2 coming from deeper crustal levels, from the mantle, or from other sources. Na-Ca exchange involving a Na-exchanger could be an alternative genetic hypothesis. At present, however, at least for some areas (e.g., Northern Apennines, Italy), this hypothesis is not supported by mineralogical evidence. water types (e.g., Ca-carbonate) are dominant. Some analyses of different types of NaCW (mostly from Italy) are reported in Table 1 together with indications about the rocks involved in water-rock interaction. In the following pages we will focus on wa-ters of extreme composition, i.e., with na and calc higher than 0.85. In the Northern Apennines (Italy), waters with na and calc > 0.85 are wide-spread and thus, frequently, we shall implicitly refer to them. Data processing For water speciation and for other calculations we have used a recent version of PHREEQC (Parkhurst and Appelo, 1999), a flexible ad user-friendly software. The software is adequate for low ionic strength solutions (Debye-Hückel expres-sion), and suitable at higher ionic strength for so-dium chloride dominated systems. The limits of
Cited By (since 1996): 7, Export Date: 27 June 2012, Source: Scopus, Language of Original Document: English, Correspondence Address: Moore, G.F.; Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822, United States; email: gmoore@hawaii.edu, References: Adamson, S., Controls on the morphological variability of the décollement zone in the Nankai Trough subduction zone (2004), [M.S. thesis]. Univ. California, Santa CruzAndo, M., Source mechanisms and tectonic significance of historical earthquakes along the Nankai Trough, Japan (1975) Tectonophysics, 27, pp. 119-140;
This collection brings together important contributions by leading econometricians on (i) parametric approaches to qualitative and sample selection models, (ii) nonparametric and semi-parametric approaches to qualitative and sample selection models, and (iii) nonlinear estimation of cross-sectional and time series models. The advances achieved here can have important bearing on the choice of methods and analytical techniques in applied research.
The objectives of this chapter are (1) to review the complex relations between the Alps and the Northern Apennines, and (2) to outline the kinematic history in the transitional belt from the Northern Apennines front to the adjoining Po Plain foreland. The first section contains a comparative summary of the structural evolution of the two adjoining chains. The second section unravels the relations among the three main tectonic elements buried beneath the Quaternary deposits of the Po Plain; that is (1) the N-facing Northern Apennines front, (2) the S-facing Southern Alps front and (3) the Adriatic-Po Plain foreland in between. The third section discusses possible interpretations and implications.
Building on the success of its 1993 predecessor, this second edition of Geochemistry, Groundwater and Pollution has been thoroughly re-written, updated and extended to provide a complete and authoritative account of modern hydrogeochemistry. Offering a quantitative approach to the study of groundwater quality and the interaction of water, minerals, gases, pollutants and microbes, this book shows how physical and chemical theory can be applied to explain observed water qualities and variations over space and time. Integral to the presentation, geochemical modelling using PHREEQC code is demonstrated, with step-by-step instructions for calculating and simulating field and laboratory data. Numerous figures and tables illustrate the theory, while worked examples including calculations and theoretical explanations assist the reader in gaining a deeper understanding of the concepts involved. A crucial read for students of hydrogeology, geochemistry and civil engineering, professionals in the water sciences will also find inspiration in the practical examples and modeling templates. © 2005 C.A.J. Appelo & D. Postma, Amsterdam, The Netherlands and Ben Akkerman collection Stedelijk Museum, Amsterdam. All rights reserved.
The isotopic composition of boron in illite-smectite (I-S) can be important for monitoring fluid/rock interactions in sedimentary basins. Boron substitutes for Si during reaction of smectite to illite and can preserve information about paleofluid B-isotopic composition. Boron is enriched in oilfield brines, therefore the isotopic composition of those brines may be recorded during illitization and represent a monitor of hydrocarbon maturity and migration. We re-examined previously published experimental results on B-isotope fractionation between I-S and water. By separating B from two crystallographic sites of I-S (tetrahedral and interlayer), we found differences in the δ11B that might be used as a single-mineral geothermometer. Boron incorporation in I-S follows a non-linear kinetic pathway. Maximum interlayer-B incorporation occurs during R1-ordering. R3-ordering approaches equilibrium with expulsion of interlayer-B leaving only tetrahedral layer-B. The important discovery is that tetrahedral layer δ1B does not change between R1 and R3 ordering. Boron substitutes in an equilibrium ratio early in the crystallographic reordering of I-S. Natural I-S samples were tested from Gulf Coast mudstones, increasingly illitized with burial depth. Diagenetic reaction kinetics differ from hydrothermal experiments, but still reveal large δ11B differences (up to 40‰) between the interlayer and tetrahedral layer. Interlayer δ11B decreases with increasing temperature and illitization. We propose that interlayer δ11B values represent metastable equilibrium, whereas tetrahedral layer B represents a temperature-dependent equilibrium. If this is true, then the B-isotope geochemistry of I-S can be used to determine paleotemperatures and monitor the influence of hydrocarbons on pore fluids associated with diagenetic I-S.
Most water produced from Cenozoic oil and gas reservoirs in the Gulf of Mexico sedimentary basin is derived from dewatering of the clastic sediments themselves. Locally, both water and solutes enter the Cenozoic section from underlying Mesozoic strata. Aqueous solutes, as distinct from the water, are derived almost entirely from extensive water/rock reactions, including dissolution/recrystallization of the Jurassic Louann Salt. Three types of water dominate Cenozoic clastic reservoirs. Most reservoirs produce water consisting of mixtures of these three types, explaining why some reservoirs are characterized by highly variable water chemistry. -from Authors
The evolution of the nitrogen and boron content of shales during diagenesis and anchimetamorphism was studied in the Carboniferous rocks of Donbas by means of the bulk rock chemical analysis and the XRD quantification of mineral composition, aided by CEC and EGME sorption measurements. The contributions of the organic-bound N and B were taken into account, based on the literature data (B) and on the relationship established in the course of this study (N). 28–98% of the total N and 80–100% of the total B are contained in the mineral fraction of the investigated shales.
The mineral nitrogen is located mostly in illite and accounts for 3 to 64% of the sites available for its fixation in 1Md illite. The fixation of N by illite seems to diminish in the course of diagenesis, but additional fixation occurs in newly formed 2M 1 illite during the anchimetamorphic stage. The volume of N contained in illite in most samples greatly surpasses the N available locally from the organic matter contained in shale. Modelling indicates that the measured level of N for K substitution in illite corresponds to the capture in 30 vol.% of shale of all N released in a basin containing 5 vol.% of coal.
Boron is held predominantly by the 1Md fraction (illite+smectite). During diagenesis boron is redistributed into the 1Md illite, and during anchimetamorphism it is released from the 1Md illite and incorporated into new 2M 1 illite. No indication of the net enrichment of pore water in B due to the clay alteration process was found.
The origin of hypersaline brines from Urania and Bannock deep anoxic basins in the eastern Mediterranean Sea has been investigated by integrating geochemical data and boron isotopic ratios. Bottom brines from Urania basin have chloride contents up to 4200 mmole/kg H2O and a marine Na/Cl ratio (0.87). All the other ionic ratios are different from the marine ratios and show a relative enrichment in Ca, K, Br, and B and depletion in Mg and SO4, as normalized to the chloride ion. The δ11B values of the Urania brines (δ11B = 29.8 ± 2.9‰; n = 7) are lower than that of Mediterranean seawater (39‰). The concentrations of Cl and Na, which make up 95% of the total dissolved ions (in molal units), suggest that the Urania brines were derived from eightfold evaporated seawater. The relative enrichment of Ca and depletion of Mg and SO4 reflect dolomitization, gypsum precipitation, and sulfate reduction processes which modified the original evaporated seawater while the brines were entrapped as interstitial waters in the sedimentary section of the Mediterranean. The relative enrichments of Br, B, and K, and the low δ11B value of the Urania brines suggest high-temperatures interactions of the evaporated sea water with sediments. Mass-balance calculations suggest that desorption of exchangeable B from the sediments (δ11B ∼ 20‰) modified the marine B isotopic composition of the original eightfold evaporated seawater. Potassium was also leached from clay minerals whereas Br was contributed from degradation of organic matter in the sediments. This is consistent with a thermal anomaly (up to 45°C) recorded at depth in the region of Urania basin. In contrast, bottom brines and shallow interstitial fluids from Bannock basin with low temperatures (15°C) show marine δ11B (δ11B = 39.6 ± 2.8‰; n = 5; 38.5 ± 2.2‰; n = 5, respectively) and B/Cl ratios (7 × 10−4). The B isotope data confirm that the Bannock brines were derived from twelvefold evaporated seawater. We argue that the brines from both basins are relics of fossil evaporated seawater that was entrapped in Late-Miocene sediments and accumulated in the deep basins of the Mediterranean seafloor.
Soulevant le paradoxe de la definition pluraliste de la raison au sein du paradigme interculturel de la philosophie, aboutissant a la divergence des theories de l'unite et de la multiplicite, l'A. propose d'analyser le concept de monde, defini comme mondanite ou phenomene-monde, qui apparait au centre de cette situation interculturelle de base. Examinant les notions d'environnement, systeme, nihilisme, monde de la vie, monde de signification, l'A. mesure la possibilite de la definition du monde comme dependance a l'horizon, intermediaire entre l'un et l'autre, phenomene elementaire, monde pluriel, et ouvre la voie a une phenomenologie du dialogue des mondes
Authigenic carbonates and muds from six mud volcanoes in the eastern Mediterranean Sea were recovered during the French/Dutch MEDINAUT cruise utilizing the submersible Nautile in November 1998. The mud volcanoes are active seafloor vents in two areas at the plate boundary between the converging African and Eurasian Plates: the Mediterranean Ridge accretionary prism near Crete (Greece) and the Anaximander Mountains south of Turkey. B contents and δ 11 B signatures were measured with the aim of identifying the diagenetic processes and source depths of the material in the collision zone. B concentrations of the carbonate precipitates cover a range of 8-45 ppm and vary isotopically from +15.6 to +22.9% (corresponding to a parent solution of 34.9-42.2‰ at pH 7). Both the B-enrichment and a δ 11B valve slightly lower than seawater suggest the mud domes originate from a moderately deep fluid source, with local admixture of seawater. B contents and δ 11B of the mud show distinct differences between the areas: the Mediterranean Ridge mud domes have lower B contents and higher δ 11B (average 3.9‰) compared to Anaximander Mountains mud volcanoes (δ 11B average -0.6‰). These B results attest the release of structurally-bound B from clay mineral lattices, probably due to stronger deformation near Turkey. These mudstones, which had previously been affected by deep-seated thrusting beneath the Antalya Complex, may have been liquefied and remobilized in their present setting. By contrast, the mud on the Mediterranean Ridge represents offscraped clay-rich strata that was incorporated into the large accretionary wedge.
Geochemical and isotopic data for methane and ground water indicate that gaseous hydrocarbons in Eocene aquifers in east-central Texas form by bacterial processes. The δ¹³C values of methane from live wells in the clay-rich Yegua and Cook Mountain Formations range from -71{per thousand} to -62{per thousand}. Methane from ten wells in the cleaner sands of the Sparta Queen City Formations have δ¹³C values between -57{per thousand} and -53{per thousand}. The carbon isotopic difference between methanes from the Yegua and Sparta aquifers is comparable to the isotopic difference in sedimentary organic matter from outcrops of the units, suggesting substrate control on the δ¹³C of bacterial methane. Hydrogen isotopic compositions of methane from the aquifers are similar, averaging -181{per thousand}. This high value suggest methane production predominantly by COâ reduction. The δ¹³C dissolved inorganic carbon (DIC) in high bicarbonate waters increase from about -20{per thousand} to 0{per thousand} with increasing DIC. Mass-balance calculations indicate that the DIC added to the ground water has δ¹³C values as high as 10{per thousand}. This ¹³C-enriched carbon is predominantly derived from COâ production by fermentation and anaerobic oxidation reactions combined with COâ consumption by COâ reduction. This process is responsible for high bicarbonate contents in these and probably other Gulf Coast ground waters.
In the present work, the first results are reported for both Li and B isotope ratios in rainwater samples collected over a long time period (i.e. monthly rainfall events over 1 a) at a national scale (from coastal and inland locations). In addition, the stable isotopes of the water molecule (δD and δ18O) are also reported here for the same locations so that the Li and B isotope data can be discussed in the same context. The range of Li and B isotopic variations in these rainwaters were measured to enable the determination of the origin of these elements in rainwaters and the characterization of both the seasonal and spatio-temporal effects for δ7Li and δ11B signatures in rainwaters. Lithium and B concentrations are low in rainwater samples, ranging from 0.004 to 0.292μmol/L and from 0.029 to 6.184μmol/L, respectively. δ7Li and δ11B values in rainwaters also show a great range of variation between +3.2‰ and +95.6‰ and between −3.3‰ and +40.6‰ over a period of 1 a, respectively, clearly different from the signature of seawater. Seasonal effects (i.e. rainfall amount and month) are not the main factors controlling element concentrations and isotopic variations. δ7Li and δ11B values in rainwaters are clearly different from one site to another, indicating the variable contribution of sea salts in the rainwater depending on the sampling site (coastal vs. inland: also called the distance-from-the-coast-effect). This is well illustrated when wind direction data (origin of air masses) is included. It was found that seawater is not the main supplier of dissolved atmospheric Li and B, and non-sea-salt sources (i.e. crustal, anthropogenic, biogenic) should also be taken into account when Li and B isotopes are considered in hydrogeochemistry as an input to surface waters and groundwater bodies as recharge. In parallel, the isotopic variations of the water molecule, vector of the dissolved B and Li, are also investigated and reported as a contour map for δ18O values based on compiled data including more than 400 δ18O values from throughout France. This δ18O map could be used as a reference for future studies dealing with δ18O recharge signature in relation to the characterization of surface waters and/or groundwater bodies.
The B isotopic composition, in combination with O and H isotopes and hydrochemical tracers, is utilized to constrain the evolution of basement-hosted groundwaters via water–rock interactions and fluid infiltration from external (sedimentary) reservoirs. Two distinct groundwater types have been identified in the Central European crystalline basement (N Switzerland–SW Germany): (1) fresh groundwaters characterized by low values of δ11B (−3.5 to −0.6‰), δ18O (−12.0 to −10.0‰), and δD (−86.8 to −71.9‰), and (2) brackish groundwaters with distinctly heavier B, O, and H isotopic compositions (δ11B=+6.4 to +17.6‰, δ18O=−9.4 to −5.6‰, δD=−67.6 to −60.8‰). Fresh groundwaters show a systematic decrease in δ11B, related to an increase in B concentrations (and degree of total mineralization), along the pathway of groundwater migration which can only be interpreted in terms of leaching of crystalline host rocks. A δ11B value of −3.3‰ is inferred for the crustal B source (mainly Hercynian granites) involved in the leaching process, in agreement with the known δ11B range of granitic rocks. The evolution of brackish groundwaters, derived from crystalline basement reservoirs with little water circulation, is more complex. As indicated by B–O–H stable isotope and hydrochemical (e.g. B/Cl, Na/Cl, and Br/Cl) constraints, brackish groundwaters from the study area are influenced by admixture of sediment-derived fluids which infiltrated from Late Paleozoic (Permo-Carboniferous) and Early Mesozoic (Lower Triassic) sedimentary strata. The data presented show that B isotopes are sensitive to mixing processes of fluids derived from different crustal reservoirs and, hence, may be utilized as a tracer for constraining the internal (autochthonous) vs external (allochthonous) origin of salinity in basement-hosted groundwaters.
Lithium and Boron isotopic compositions of rainwaters in France: origin and spatio-temporal characterization
Mud volcanoes are important conduits for deep fluids to migrate upward, providing an important window to study fluid/sediment interactions at depth in accretionary prisms. Fluids emitting from mud volcanoes in southern and eastern Taiwan were analyzed for dissolved chemical composition and B isotopes to delineate the sources and chemical alteration occurring during fluid migration. Concentrations of dissolved major elements (Cl, Na, K, Ca, Mg, and SO4) in most of the mud volcano fluids were lower than seawater concentrations, except for the high Ca samples in eastern Taiwan, which were probably affected by fluids/igneous rock interactions. The high concentrations of B, Ba, and Li in the mud volcano fluids are consistent with a scenario that involves intense sediment alteration and clay dehydration at depth. The reaction temperatures estimated using chemical thermometers fall within the range of 70–170 °C, with some variation by location. In nearby mud volcano sites, the concentration of dissolved major elements varied little, but the B stable isotope compositions varied by as much as 20‰, supporting the argument that dissolved B concentrations were over-printed with effects of sediment adsorption. This explains the occurrence of B enriched and heavy δ11B fluids at moderate depths in subduction zones. It is probable that the fluids in mud volcanoes in Taiwan originated from 2 to 5 km depth and are influenced by processes involving tectonic shortening, sediment alteration, and clay dehydration, and subsequent retrograde adsorption during fluid migration.
This work reports chemical and isotope data and temperature estimates for seven water samples collected
from Triassic formations in the Paris Basin in France. Four samples were collected in the central part of the
Basin (saline waters) and three were collected at the edge of the Basin near the recharge zone (dilute waters).
The saline waters collected from the Chaunoy and Champotran boreholes have high salinities (around
120 g/L) and very similar chemical and isotopic compositions. The saline water sample from the La Torche
borehole has much higher salinity (168 g/L) and significantly different isotope characteristics. The chemical
geothermometers applied to these fluids from the centre of the Basin give temperature values ranging
between 80 and 100 °C. The fresh water samples collected at the edge of the Basin have very different
chemical and isotopic compositions. These dilute water samples (Santenay and Châteauroux) are shallow,
with colder temperatures of around 45 to 50 °C. The study of uranium activity ratios for these Triassic
formation waters allows us, as a first approximation, to estimate a mean apparent fluid circulation velocity of
around 0.2 m/yr, which corresponds to a “mean age” slightly higher than 1 My for waters sampled in the
Chaunoy, Champotran and La Torche fields in the centre of the Basin. The multi-isotope characterization of
Triassic formation waters shows that our data are in agreement with literature values as concerns
“traditional” isotope systematics (δ18O, δD, 87Sr/86Sr). Li and B isotope signatures in the centre of the Paris
Basin are in a good agreement with a fluid signature derived mainly from water/rock interactions involving
clastic rocks with water essentially resulting from a seawater-derived brine endmember diluted by meteoric
waters. The data reported in the present work for Li and B isotopes could be used as a reference for future
studies to characterize sandstone formation waters.
Composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout Italy. These samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area. On the basis of the results obtained a first map of the isotopic composition of precipitations in Italy has been drawn up. The main features of this map are the following: (1) no isotopic latitudinal gradient has been found along the Tyrrhenian coast from Sicily to the Italian–French border, despite the considerable range of latitude; (2) a minor latitudinal gradient is found in the southeasternmost section of the country (Apulia), partially favored by the local morphology; (3) a marked ‘shadow effect’ of the Apennines is apparent along the southern section of the Po valley and along the central section of the Adriatic coast; (4) the contribution of water vapor from the northernmost section of the Adriatic sea affects the eastern and central sections of the Po plain; (5) the shadow effect of the Alps is considerably smaller than expected; (6) the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about −0.2‰/100m; (7) when mean monthly temperature values were available, their relationship with the isotopic composition of precipitation was found to be, on average, very poor; (8) the relationship between mean δ18O and mean δD calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line. These shifts are different for northern, central, and southern Italy; (9) in a few cases anomalously low monthly δ values suggest the existence of pronounced ‘amount effects’.
A fundamental question in the genesis of komatiites is whether these rocks originate from partial melting of dry and hot mantle, 400–500 °C hotter than typical sources of MORB and OIB magmas, or if they were produced by hydrous melting of the source at much lower temperatures, similar or only moderately higher than those known today. Gorgona Island, Colombia, is a unique place where Phanerozoic komatiites occur and whose origin is directly connected to the formation of the Caribbean Large Igneous Province. The genesis of Gorgona komatiites remains controversial, mostly because of the uncertain origin of volatile components which they appear to contain. These volatiles could equally result from shallow level magma contamination, melting of a “damp” mantle or fluid-induced partial melting of the source due to devolatilization of the ancient subducting plate. We have analyzed boron isotopes of olivine-hosted melt inclusions from the Gorgona komatiites. These inclusions are characterized by relatively high contents of volatile components and boron (0.2–1.0 wt.% H2O, 0.05–0.08 wt.% S, 0.02–0.03 wt.% Cl, 0.6–2.0 μg/g B), displaying positive anomalies in the overall depleted, primitive mantle (PM) normalized trace element and REE spectra ([La/Sm]n = 0.16–0.35; [H2O/Nb]n = 8–44; [Cl/Nb]n = 27–68; [B/Nb]n = 9–30, assuming 300 μg/g H2O, 8 μg/g Cl and 0.1 μg/g B in PM; Kamenetsky et al., 2010. Composition and temperature of komatiite melts from Gorgona Island constrained from olivine-hosted melt inclusions. Geology 38, 1003–1006). The inclusions range in δ11B values from − 11.5 to + 15.6 ± 2.2‰ (1 SE), forming two distinct trends in a δ11B vs. B-concentration diagram. Direct assimilation of seawater, seawater-derived components, altered oceanic crust or marine sediments by ascending komatiite magma cannot readily account for the volatile contents and B isotope variations. Alternatively, injection of < 3wt.% of a 11B enriched fluid to the mantle source could be a plausible explanation for the δ11B range that also may explain the H2O, Cl and B excess.Highlights► Melt inclusions in olivine from Gorgona komatiites range in δ11B from − 10 to + 16‰. ► These inclusions contain 0.2–1.0 wt.% H2O, 0.02–0.03 wt.% Cl and 0.6–2.0 μg/g B. ► Shallow depth magma contamination does not explain the observed δ11B range. ► The δ11B range is due to the injection of < 3 wt.% of slab fluid into rising mantle plume. ► This result supports wet origin of komatiites from the Island of Gorgona, Colombia.
Since approximately forty years ago, the equation relating the oxygen isotope fractionation between bisulfate and water has been extensively used as a geothermometer for acidic and high-enthalpy hydrothermal systems (T > 150 °C). Its application to near-neutral or basic, low-enthalpy (T < 150 °C) systems was considered to be unreliable. Recently, empirical and theoretical geothermometric equations were formulated for the (SO42 −–H2O) oxygen isotope system, opening new perspectives on isotope geochemistry applied to geothermal research. In the present paper, these geothermometers are applied while revisiting a variety of hydrological case studies. In addition to the equilibrium fractionation, isotopic effects on geothermometric estimates due to mixing–dilution, salinity, sulfide oxidation, sulfate reduction, standardization of the analytical results and aqueous speciation are also discussed.
Spring waters issuing from serpentinized ultramafic rocks of the Taro-Ceno Valleys (Northern Apennine, Emilia-Romagna region, Italy) were analyzed for major element, trace element and dissolved gas concentrations and δ11B, δ7Li, δ18O(H2O), δ2H(H2O), δ13C(CH4) and δ2H(CH4) isotope compositions. Similar to other springs worldwide that issue from serpentinites, the chemical composition of the waters evolves with water–rock interaction from Ca-HCO3, through Mg-HCO3 and ultimately to a hyperalkaline Na-(Ca)-OH composition. Most of the Ca- and Mg-HCO3 springs have δ11B ranging between +16.3‰ and +23.7‰, consistent with the range of low P–T serpentinites. Very high δ11B in two springs from Mt. Prinzera (PR10: +39‰; PR01: +43‰) can be related to isotopic fractionation during secondary phase precipitation, as also inferred from δ7Li values. In contrast to typical abiogenic isotope signatures of CH4 from serpentinized rocks, dissolved CH4 from the Taro-Ceno hyperalkaline springs has an apparent biotic (thermogenic and/or mixed thermogenic-microbial) signature with δ13C(CH4) ranging from −57.5‰ to −40.8‰, which is similar to that of hydrocarbons from production wells and natural seeps in adjacent hydrocarbon systems. The data suggest that CH4 in the hyperalkaline springs investigated in this study may derive from organic matter of the sedimentary (flysch and arenaceous) formations underlying the ophiolite unit. However, small amounts of H2 were detected in one hyperalkaline spring (PR10), but for two springs with very low CH4 concentrations (PR01 and UM15) the δ2H value could not be measured, so the occurrence of some abiotic CH4 cannot be excluded. The occurrence of thermogenic CH4 in ophiolites may be a widespread phenomenon, and thus the characterization of serpentinization-related gases requires accurate evaluation of the regional context including a careful knowledge of the relationships with surrounding sedimentary rocks and their hydrocarbon potential.
The boron isotopic compositions and boron concentrations of selected modern marine carbonates were analysed by negative thermal ionization mass spectrometry with a 2 reproducibility of standards and samples better than 0.7%. It was found that the boron isotopic compositions of modern marine carbonates fall within a relatively narrow range (+22.1 ± 3%. relative to NBS SRM951 boric acid standard) for all samples (biogenic, nonbiogenic, warm water, cold water, aragonitic, or calcitic). This is about 17%. lighter than seawater. This indicates that mineralogy, temperature, and vital effects are not primary controls on the observed isotopic composition. The narrow range in isotopic composition is in contrast to the wide range in boron concentrations of these samples (10.9-71.4 ppm). The boron isotopic compositions and boron concentrations in modern marine carbonates are consistent with preferential adsorption of the isotopically lighter B(OH) 4 1- aqueous species over the B(OH) 3 species before incorporation into the carbonate site. Because there is a pH control on the availability of B(OH) 1- 4 , the result is a pH control on the boron abundance in the carbonates. Possible second-order biomineralogic controls on pH may account for boron concentrations in calcareous organisms that produce low pH microenvironments at the site of CaCO 3 precipitation.
Classical chemical classification plots that use major anions and cations can discern between different water facies but they do not offer sufficient discriminatory power for salt waters from sedimentary basins, whose origin is therefore frequently misunderstood. The Brine Differentiation Plot (BDP) was proposed by Hounslow (1995) in order to investigate the brine genesis, principally evaporite dissolution, alkali lakes and oilfield brines. However, its diagnostic potential has been undervalued so far. In this paper, the potential of BDP was tested and compared with the classical Langelier–Ludwig plot using concentration of major dissolved constituents of fresh to brine waters from different sedimentary basins (Northern Apennine Foredeep, Italy; Provence Basin, Western Mediterranean; Caucasus; Trinidad). Mixing processes between different water types as evaluated by these diagrams would seem to be constrained by the boron–chloride plot.
This paper presents new chemical data of hydrocarbon-rich gases discharged from mud volcanoes and CH 4 -rich emissions located in different areas of Italy (Northern Apennines and Sicily). The determination of C 5 –C 10 alkanes, cyclics and aromatics was carried out by GC–MS, while the main gas species and C 1 –C 4 hydrocarbons were analyzed by GC-TDC and GC-FID, respectively. Methane is by far the most abundant component of all the investigated gas emissions, with the exception of part of those discharging close to Mt. Etna volcano, which are CO 2 -rich. The gas samples collected from the Emilia Apennine and Sicily show δD–CH 4 and δ 13 C–CH 4 values typical of thermogenic gases. Most gases from the Romagna Apennine discharge methane with a biogenic isotopic signature. Non-methane hydrocarbons of biogenic gases are almost exclusively C 2 – C 4 alkanes, with minor amounts (fraction of μmol/mol) of C 4 + compounds, including few aromatics and cy-clics, likely deriving from minor thermogenic contribution not evidenced by the δ 13 C–CH 4 and δD–CH 4 values. The Etnean gases, whose R/Ra and δ 13 C–CO 2 values indicate a strong contribution from a hydrother-mal fluid source related to the nearby volcanic system, show a significant enrichment of aromatics com-pounds (up to 36% of the non-methane organic gas fraction), which is likely produced by catalytic reforming processes, such as dehydrocyclization of alkanes. The thermogenic gases from the Apennines and southwestern Sicily are characterized by the presence of more than 20 different cyclic compounds with concentrations up to several μmol/mol. Cyclic compounds are likely formed by i) thermal cracking and ii) uncompleted aromatization of alkanes occurring at depth > 3 km and temperatures not exceeding 120–150 °C.
Abstract In order to elucidate the origin and migration of basinal brines in the Bachu Bulge, Tarim Basin, we have carried out analyses on chemical composition, and boron, hydrogen and oxygen isotopes of formation waters together with the XRD of clay minerals from the Paleozoic strata. The waters show Ca, B, Li and Sr enrichment and SO4 depletion in the Carboniferous and Ordovician and K enrichment in part of the Ordovician relative to seawater. The relationship between δD and δ18O shows that all the data of the waters decline towards the Global Meteoric Water Line with the intersection of them close to the present-day local meteoric water, suggesting that modern meteoric water has mixed with evaporated seawater. The 87Sr/86Sr ratios range from 0.7090 to 0.7011, significantly higher than those of the contemporary seawater. The δ11B values range from +19.7 to +32.3‰, showing a decrease with the depth and B concentrations. The results suggest that isotopically distinct B and Sr were derived from external sources. However, since the percentages of illite are shown to increase with depth among clay minerals in the study area, i.e., illite is due to precipitation rather than leaching during deeper burial, it is unlikely for illite to have contributed a significant amount of B to the waters. Thus, B with low δ11B values is interpreted to have been added mainly from thermal degradation of kerogen or the basalts in the Cambrian and Lower Ordovician.
The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories - virtually all those performing geochemical boron isotope analyses in the world - which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ11 B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution.
The Br/Cl, Li/Cl and B/Cl ratios and boron isotope compositions of hypersaline pore fluids from DSDP Sites 372 and 374 were measured in an attempt to evaluate the origin of the brines. In Site 374 the relationships between the Cl concentrations (up to 5000 mM) and Br/Cl (∼ 12 × 10-3), Na/Cl (as low as 0.1), B/Cl (2.5 × 10-3), and δ11B values (43–55%o)ofthedeepporewererbetween 300 and 055 mfsf,loceted withinthe Mesniniansediments,feflecrremnantoof ; 65-fold evaporated sea water. The original evaporated sea water was modified by: (1) dilution with overlying or less saline water by about 30%; and (2) slight dissolution of NaCl evaporites. The variations in δ11B show a continuous increase in δ11B values with depth in Site 374, up to 66.7%oat adepthof 000 mfsf (UpperPliocene marlsecliments). hhe conspicuous 11B enrichment trend is consistent with elemental boron depletion, which was calculated from the expected boron concentrations of evaporated sea water with corresponding Br/Cl and Na/Cl ratios. Li/Cl variations also show a depletion of Li relative to evaporated sea water. The apparent depletions of B and Li, as well as the 11B enrichment, reflect uptake of these elements by clay minerals at low water/sediment ratios.
The Bagni di Lucca thermal waters (Lucca province, Tuscany, Italy) have been well known since the Middle Age for their alleged curative properties. In the present work, the waters have been analysed for major and trace components and for O, H, S and Sr isotopes. The δ2H and δ18O values indicate a meteoric origin of the waters and the tritium content suggests long-term (more than 40 years) circulation at depth. The δ34S values in dissolved sulphate of the warmest waters (Doccione, Paolina, Bernabò, Demidoff, Cova) indicate interaction with Triassic evaporites; however, the δ34S values as well as the 87Sr/86Sr ratios in the waters appear to be a little higher (on average 17.6±0.4‰ and 0.70834±0.00006, respectively) than in Triassic sulphate minerals from the Northern Apennines (16.0±0.5‰ and 0.70778±0.00011).The waters are Ca-sulphate and characterised by high Na/Cl (≌2) and low Ca/SO4 (≌0.7) mole ratios, high Sr (≤12 mg/L), F (≤4.2 mg/L), As (≤80 μg/L), Cs (≤70 μg/L), Rb (≤107 μg/L) and salinity (up to 3087 mg/L of total dissolved solids), low alkalinity, and pH in the range 6.3–7.5. Assuming equilibrium of the waters with anhydrite and chalcedony, the evaluated temperature and pressure are about 70–75 °C and 200–300 bar; considering the pressure as hydrostatic, the evaluated depth of equilibration approaches that of the metamorphic basement (about 3.0–3.8 km) underlying the carbonate-evaporite formations occurring in the area. Thermodynamic computations indicate that the high Na/Cl ratio and the low Ca/SO4 ratio in the waters may be due to progressive dissolution of albite, anhydrite, dolomite and carbon dioxide accompanied by calcite precipitation. The linear correlations between the major and trace components, including 2H and 18O, demonstrate that thermal springs undergo dilution by low-salinity shallow waters which are recharged at low elevation.
Boron and its two stable isotopes 10 B and 11 B are considered powerful tracers in low temperature regimes like ocean waters and subduction zones, while very little is known about the isotopic fractionation in high pressure–temperature (PT) regimes. However, recent studies indicate that boron fractionation in silicate–water systems may follow a systematic relationship with temperature, regardless of the geological regime. In this paper we review previous B isotope studies and test the empirical relationship proposed by Williams et al. [Boron isotope geochemistry during diagenesis. Part I. Experimental determination of fractionation during illiti-zation of smectite, Geochim. Cosmochim. Acta 65 (2001a) 1769–1782; Boron isotope geochemistry during diagenesis. Part II. Appli-cations to organic sediments, Geochim. Cosmochim. Acta 65 (2001b) 1783–1794; Application of boron isotopes to the understanding of fluid–rock interactions in a hydrothermally stimulated oil reservoir in the Alberta Basin, Canada, Geofluids 1 (2001c) 229–240] by comparing it with the wealth of earlier data from studies of different geological scenarios. Our main conclusion is that, given the large variations of B isotope fractionation patterns in natural silicate–water systems, the majority of these systems are not represented by the proposed relationship. Factors more complex than temperature alone appear to control B isotope geo-chemistry, which include species of the silicate mineral, starting fluid, pH, geological setting, fluid/rock ratio (i.e. porosity), or time for equilibration between the solid and fluid phase.
Cited By (since 1996): 7, Export Date: 27 June 2012, Source: Scopus