Oxygen Isotope Shift Research Articles

Transient micropaleontological turnover across a late Eocene (Priabonian) carbon and oxygen isotope shift on Blake Nose (NW Atlantic)

Abstract. The Gulf Stream, a western boundary current transporting warm water into the North Atlantic, plays a key role in climate regulation and oceanographic stability at a regional and global scale as part of the Atlantic Meridional Overturning Circulation (AMOC). Evidence suggests that an ancestral Gulf Stream has existed since the Mesozoic, and it has altered its course repeatedly over Cenozoic times. In this study, we focus on the upper Eocene (Priabonian, ca. 36 Ma) from Ocean Drilling Program Site 1053 on Blake Nose (subtropical North Atlantic). Bulk carbon and oxygen stable isotopes, as well as benthic foraminiferal and calcareous nannofossil assemblages, provide an integrated assessment of the palaeoceanographic changes impacting the area through the water column to the seafloor. Micropaleontological assemblages suggest changes in surface ocean stratification and nutrient supply to the seafloor coeval with a paired negative carbon and oxygen isotope excursion and the return to background conditions higher up in the study section. These transitory changes are compatible with the longitudinal displacement of the proto-Gulf Stream and its related eddies. Our results build on previous work and support the hypothesis that links palaeoceanographic changes in the Blake Nose area with shifts in the proto-Gulf Stream during the middle and late Eocene.

Eocene Tectonic Uplifts Caused the Early Oligocene Intrusion of the Indian Monsoon Into the Tuotuohe Basin and the Increased Evaporation, Central‐Northern Tibet: Insights From the Oxygen Isotope Record

AbstractIt is not clear how the Asian monsoon evolved after leaving the spatial range of the Intertropical Convergence Zone in the Late Eocene and before the modern‐like Asian monsoon formed at ∼26 Ma. In this study, the results of a well‐dated, robust, and continuous paleoenvironmental carbonate oxygen isotope record from the Tuotuohe section in the Tuotuohe Basin on the central–northern Tibetan Plateau indicate that the carbonate oxygen isotope showed positive bias at 30.5 Ma. Evidence concerning the temperature, precipitation, paleolatitude, paleoelevation, salt mines and global temperature changes at this time suggest that the positive oxygen isotope shift was mainly due to a combination of the intrusion of the Indian monsoon into the basin and increased evaporation, both of which were ultimately induced by the tectonic uplift of the Tuotuohe Basin before 30.5 Ma and the retreat of the Paratethys Sea after the Eocene.

Evolution of the composition of Н, О and C stable isotopes in the groundwaters of oil and gas bearing sediments in the northern regions of West Siberia

The results of a study of the isotopic composition of oxygen and hydrogen of groundwater and dissolved inorganic carbon in oil and gas deposits of the northern regions of Western Siberia, covering a wide stratigraphic range – Mesozoic and Paleozoic are presented. The obtained values are very diverse, covering the intervals from –120 to –50‰ (δD) and from –17 to –2‰ (δ18O). Such a variable isotopic composition of waters indicates the absence of a unified mechanism for the accumulation of waters and their transformation during the geological evolution of the West Siberian sedimentary basin. The main feature of most of the studied waters is the pronounced values of oxygen isotope shifts relative to GMWL, which generally increase with the age of water-bearing deposits and reach 9‰, which indicates their ancient sedimentary origin. Variations in the isotopic composition of DIC (from –51.8 to +21.8‰) and its content in waters (from 0.2 to 38.6 mmol/I) indicate a wide range of water burial conditions and processes involved in the conversion of water-soluble carbon dioxide. A general pattern of changes in the isotopic composition of carbon in CO2 with time, expressed in general form by damped oscillations of the “isotope oscillator”, is revealed. A model of transformation of the carbon isotope composition in carbon dioxide in the closed cycle “atmosphere-soils-deep aquifers” for oil and gas deposits of the northern regions of Western Siberia based on the obtained isotope data is proposed.

Seawater hydrothermal system in the middle of the Kuril Arc: Yankich Island, Ushishir Archipelago

Ushishir volcano is located in the middle of the Kuril Arc. The Ushishir crater, a closed bay connected with the ocean by a narrow and shallow strait, is characterized by a strong hydrothermal activity. Boiling springs, hot pools, fumaroles and shallow submarine vents are manifestations of a magmatic-seawater hydrothermal system that discharges a boiling solution that is generally similar in chemical and isotopic composition to the seafloor hydrothermal fluids at different tectonic settings. The main features of the Ushishir fluids are: (1) water has close to zero δD and a large oxygen isotopic shift (6 to 9 ‰); (2) 3He/4He = 7.3Ra, very low CH4 and N2/Ar > 200; (3) high boron concentration (∼70 ppm); (4) a significant uptake of Ca and Sr from the host rock and Ca/Sr ratio higher than that for seawater with 87Sr/86Sr 0.7037–0.7039, a bit higher than that of the rock value (0.7031). The measured onshore discharge of boiling water is ∼5 kg/s; however, a large plume of the discolored seawater is released from the outer submarine slope of the volcano indicating a much higher total mass and heat output. We compare the seafloor hydrothermal fluids with boiling water of the coastal Ushishir springs and estimate the effective water/rock ratio using our data on oxygen and Sr isotopes and some trace elements. We also discuss the correctness of the application of solute and gas geothermometers for both seafloor and coastal seawater hydrothermal systems.

Oxygen isotope evidence for input of magmatic fluids and precipitation of Au-Ag-tellurides in an otherwise ordinary adularia-sericite epithermal system in NE China

Abstract Tellurium-rich (Te) adularia-sericite epithermal Au-Ag deposits are an important current and future source of precious and critical metals. However, the source and evolution of ore-forming fluids in these deposits are masked by traditional bulk analysis of quartz oxygen isotope ratios that homogenize fine-scale textures and growth zones. To advance understanding of the source of Te and precious metals, herein, we use petrographic and cathodoluminescence (CL) images of such textures and growth zones to guide high spatial resolution secondary ion mass spectroscopy (SIMS) oxygen isotope analyses (10 µm spot) and spatially correlated fluid inclusion microthermometric measurements on successive quartz bands in contemporary Te-rich and Te-poor adularia-sericite (-quartz) epithermal Au-Ag vein deposits in northeastern China. The results show that large positive oxygen isotope shifts from –7.1 to +7.7‰ in quartz rims are followed by precipitation of Au-Ag telluride minerals in the Te-rich deposit, whereas small oxygen isotope shifts of only 4‰ (–2.2 to +1.6‰) were detected in quartz associated with Au-Ag minerals in the Te-poor deposits. Moreover, fluid-inclusion homogenization temperatures are higher in comb quartz rims (avg. 266.4 to 277.5 °C) followed by Au-Ag telluride minerals than in previous stages (~250 °C) in the Te-rich deposit. The Te-poor deposit has a consistent temperature (~245 °C) in quartz that pre- and postdates Au-Ag minerals. Together, the coupled increase in oxygen isotope ratios and homogenization temperatures followed by precipitation of Au-Ag tellurides strongly supports that inputs of magmatic fluid containing Au, Ag, and Te into barren meteoric water-dominated flow systems are critical to the formation of Te-rich adularia-sericite epithermal Au-Ag deposits. In contrast, Te-poor adularia-sericite epithermal Au-Ag deposits show little or no oxygen isotope or fluid-inclusion evidence for inputs of magmatic fluid.

Metal Oxo-Fluoride Molecules OnMF2 (M = Mn and Fe; n = 1-4) and O2MnF: Matrix Infrared Spectra and Quantum Chemistry.

On reacting laser-ablated manganese or iron difluorides with O2 or O3 during codeposition in solid neon or argon, infrared absorptions of several new metal oxo-fluoride molecules, including OMF2, (η1-O2)MF2, (η2-O3)MF2, (η1-O2)2MF2 (M = Mn and Fe), and O2MnF, have been observed. Quantum chemical density functional and multiconfiguration wavefunction calculations have been applied to characterize these new products by their geometric and electronic structures, vibrations, charges, and bonding. The assignment of the main vibrational absorptions as dominant symmetric or antisymmetric M-F or M-O stretching modes is confirmed by oxygen isotopic shifts and quantum chemical calculations of frequencies and thermal stabilities. The tendency of Fe to form polyoxygen complexes in lower oxidation states than the preceding element Mn is affirmed experimentally and supported theoretically. The M-F stretching frequencies of the isolated metal oxo-fluorides may provide a scale for the local charge on the MF2 sites in active energy conversion systems. The study of these species provides insights for understanding the trend of oxidation state changes across the transition-metal series.

Geochemical characteristics and genesis of the high-temperature geothermal systems in the north section of the Sanjiang Orogenic belt in southeast Tibetan Plateau

A large number of thermal springs are widely distributed along the deep suture zones and faults in the north section of the Sanjiang Orogenic belt in southeast Tibetan Plateau, connecting the two high-temperature hydrothermal areas in southern Tibet and western Sichuan. Whether the genesis of all geothermal water in the north section of the Sanjiang Orogenic belt is consistent is still an unanswered question. In order to fill the research gap of the high temperature geothermal system in this region, in this study, we classified the geothermal springs into three geothermal fields (Jinsha, Lancang, and Nujiang geothermal fields) and attempted to find clues by comparing the hydrochemical and isotopic characteristics of geothermal fluids in the three geothermal fields. The δ2H and δ18O composition of geothermal springs suggest that all thermal springs are replenished by the meteoric water. Low content of trace elements and low degree of oxygen isotope shift indicate that the partial melting of the crust at a depth of about 20 km mainly provide heat for all thermal springs in the geothermal fields through conduction. But due to the difference of tectonic conditions, there are two formation patterns of geothermal waters in the study area, one was controlled by regional faults, the other was controlled by the folded complex. The geothermal waters controlled by regional faults were heated after deep circulation, and the reservoir temperatures calculated by the Silica-enthalpy mixing model are 175–200 °C and 200–225 °C, respectively. But the geothermal waters controlled by the folded complex were heated after shallow circulation, and the reservoir temperature is only 100–125 °C. Upon rising to the surface, the geothermal waters mixed with cold groundwater to different degrees. The dissolution of Na/K-silicates and carbonate rocks controlled the formation of Na-HCO3 and Ca·Mg-HCO3 type water, respectively. But dissolution of halite and gypsum (or anhydrite) in some areas can lead to further diversity of hydrochemical species, resulting in the formation of Na-Cl, Na-HCO3·Cl, Ca·Mg-SO4 and Na-HCO3.SO4 type waters.

Microfacies and multi-isotope records of Anisian sequences from the Upper Yangtze Block: possible responses to tectonics and climate-driven relative sea-level change

The Middle Triassic epoch is the key to understanding the environment changes after the Permian–Triassic mass extinction. The Anisian Badong Formation is a carbonate and siliciclastic succession deposited on the Yangtze Platform, Upper Yangtze Block. In this paper, we use facies analysis combined with sequence stratigraphy of the Badong Formation in the Nashuixi section, Yangtze Block, to discuss the Anisian relative sea-level changes. Microfacies analyses were used to define ten microfacies in four depositional facies zones (tidal flat, restricted platform, restricted to open platform, and open platform) indicating an epeiric platform depositional environment. The lowstand, transgressive, and highstand systems tracts and two sequences were identified. Sequence stratigraphy interpretations indicate that relative sea-level at Nashuixi experienced two rises in the Middle Anisian, which is correlated with those in the Yangtze Block, confirming that sea-level changes during the Anisian were of eustatic origin. However, a distinct regression at Nashuixi occurred in the late Bithynian to IIIyrian while the global sea-level rose, which is likely to be caused by interference from regional tectonics during IIIyrian. The carbon and oxygen isotopic shifts in the Nashuixi section exhibit two negative-values stage in the time near end of Aegean and early Pelsonian, which is well correlated with the global typical sections, indicating two middle Anisian warming events. Our study indicated that the relative sea-level at Nashuixi was controlled by global sea-level change and regional tectonics (Indosinian Orogeny), and the C and O isotopes records respond to global climate change.

Geochemistry of Bazman thermal springs, southeast Iran

Thermal springs of the Bazman geothermal field, 27km south of the Holocene Bazman volcano caldera in Makran continental margin, SE Iran, were studied for the first time. New data on major components, selected trace elements (Li, Rb, Cs, Ba, Sr, Fe, Al), water isotopic composition (H, O and S), chemical and isotopic (δ13C of CO2 and CH4, 3He/4He and 40Ar/36Ar) composition of dissolved and bubbling gases from the hottest vents are presented. Four groups of springs with temperature range of 27–44°C discharge Na-Cl waters with total dissolved solids (TDS) of ∼800 to ∼7000mg/L from different aquifers composed of diverse type of rocks including granites and limestone. Only the hottest and most saline springs of the Bazman field with low bicarbonate are close to equilibrium with surrounding rocks whereas the others discharge immature waters. Geothermometry based on SiO2 concentrations, Na-K and Na-K-Ca-Mg systems shows low equilibrium temperatures of up to 130°C, consist with the temperatures estimated by alumino-silicate minerals saturation indices. The water isotopic composition (δ18O and δD) indicates meteoric origin with a small oxygen isotopic shift measured in the saline waters. The δ34S values of SO4 indicate influence of gypsum and anhydrite dissolution from the host rock. Dissolved and free gases are N2-rich (>95vol.%) with a high He content (0.5vol.%). A biogenic origin may be suggested for CH4 and CO2 based on their carbon isotopic characteristics (−62‰ and −13‰ vs. V-PDB, respectively). The R/Ra value of 0.5 indicates a contribution of about 6 % of He from the mantle. It is suggested that the Bazman thermal waters are heated at considerable depth (4−5km) in a deep fault system most probably by the regional heat flow according to the local geothermal gradient.

Multi-element isotope study of natrocarbonatites (1993 lava flows) from Oldoinyo Lengai volcano, Tanzania: Implications for core-mantle interactions

We contribute to the debate of core-mantle interactions by providing tungsten (W) isotope (ε182W) data from natrocarbonatite samples collected from the 1993 lava flows at Oldoinyo Lengai (OL) volcano, Tanzania. The 182Hf-182W system (half-life = 8.9 Ma) is well suited to constraining the timing of core formation and monitoring incursions of the core into the mantle. Most mantle-derived rocks are difficult to analyze because of their ultra-low W contents. We consider natrocarbonatites as suitable proxy for quantifying the core-mantle interactions given their unusually high W concentrations (published values range from ~40 to 115 ppm). The ε182W values of 7 natrocarbonatites measured by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) represent the first dataset obtained for the OL lavas (OLLs). The ε182W values calculated from W isotope ratios range from −0.01 to +0.16 and are indistinguishable within limits of uncertainty, from those of the ambient modern mantle sources (i.e., EM1, HIMU, and HIMU-like). The relatively uniform W isotope compositions associated with the lack of any ε182W anomaly from the natrocarbonatites imply that there may have been no contribution from the core (i.e., ε182W < 0) into the magma source of the OLLs. Alternately, the core signature could have been obscured either by the addition of mantle components that survived since the Earth's early accretion, or by an unknown region formed by an inefficient percolation of metal during core-mantle segregation that left parts of the mantle enriched in W. New C–O isotope data from the same samples (δ13C = −5.9 to −6.9‰; δ18O = 9.5–10.9‰) rule out any involvement of the continental crust into the OL magma and are consistent with other studies that show a mantle signature for most natrocarbonatites. The heavier δ18O values can be attributed to sub-solidus processes. The potential oxygen isotopic shift would not, however, affect the W isotopic compositions of the OLLs.

Stable isotope analyses of the carbonate component of bones and teeth: The need for method standardization

In addition to the collagen and phosphate components of bones and teeth, the stable carbon and oxygen isotope compositions of skeletal carbonate are frequently measured to determine diet, environmental conditions, and populational or individual migration in bioarchaeological research. A standardized method for the stable isotopic analysis of skeletal carbonate has not yet been established, despite the importance of these data. In this study, significant differences in the stable oxygen isotope values of bones and dental enamel were observed, which arose due to instrument- and methodology-based differences. The same target archaeological samples were analyzed in three laboratories, and the stable isotope analyses were supplemented by Fourier Transformation Infrared Spectroscopy (FTIR) measurements, which detected a strong OH− concentration-dependence in the stable oxygen isotopic shifts measured between the three laboratories. Laboratory experiments were conducted to quantify the effects of reaction temperature and phosphoric acid (H3PO4) concentration on the oxygen isotopic composition of carbonate, both of which resulted in significant, though smaller δ18O changes than the OH-related δ18O change. As such, we suggest that the δ18O values of bone structural carbonate should not be included in anthropological interpretation and that the analysis of tooth enamel should be conducted at 70 °C using 102% H3PO4, in order to make the results comparable. Furthermore, carbonated hydroxylapatite (CHAP) reference materials with varied isotopic compositions should be developed in the near future.

Processes Controling Isotopic Composition (δD and δ18O) of Thermal Waters of the Kuril Island Arc

The edifices of many active volcanoes on the Kuril Islands contain hydrothermal systems whose surface manifestations include springs with diversity in their chemical compositions and in their physical and chemical parameters. Thermal waters of Kuril Islands were found to exhibit four main isotopic shifts relative to the local meteoric water line. The ultra-acid Cl–SO4 (SO4–Cl) waters show a mixing trend between the meteoric component and volcanic steam. Acid steam-heated SO4 waters demonstrate trends indicating kinetic fractionation at temperatures near the boiling point. The isotope compositions for coastal springs plot at the line of mixing between meteoric and sea water. The oxygen isotope shift for the thermal waters that from geothermal wells is formed by isotope exchange with the host rock. The latitude effect detected in the isotope composition of meteoric water is also seen to varying degrees in the isotope composition of thermal water.

Seawater-rock interaction at Ushishir volcano-hydrothermal system, Kuril Islands

Ushishir volcano is located in the middle of the Kuril Arc. The Ushishir crater, a closed bay connected with the ocean by a narrow and shallow strait is characterized by a strong hydrothermal activity. Boiling springs, hot pools, fumaroles and shallow submarine vents are manifestations of a magmatic-seawater hydrothermal system with the discharging solution similar in chemical and isotopic composition to the seafloor hydrothermal fluids. The main features of the Ushishir fluids are: (1) water has close to zero δD and a large oxygen isotopic shift (6 7‰); (2) high boron concentration (~70 ppm); (3) a significant uptake of Ca and Sr from the rock and Ca/Sr higher than that for seawater with 87Sr/86Sr ~0.7037, a bit higher than the rock value (0.7032). The measured onshore discharge of boiling water is ~ 5 kg/s; however, a large plume of the discoloured seawater releasing from the outer submarine slope of the volcano indicates a much higher total mass and heat output.

The end-Permian regression in the western Tethys: sedimentological and geochemical evidence from offshore the Persian Gulf, Iran

Detailed sedimentological and geochemical records across the Permian–Triassic boundary (PTB) in five offshore wells of the central Persian Gulf served to interpret the end-Permian sea-level change in this region. A decrease in sea level at the PTB was established by petrographical and geochemical study of the boundary. Thin sections showed that Upper Permian strata are composed of dolomite with minor anhydrite, changing into limestone in Lower Triassic sediments. Brine dilution toward the boundary supports sea-level fall in the Permian–Triassic transition, reflected by a decrease in anhydrite content and a shallowing-upward trend from lagoonal to peritidal facies. Isotopic changes at the boundary are in favor of sea-level fall. Changes in both carbon (from about 4 to –1‰) and oxygen (from 2 to –5‰) stable isotopes show negative excursions. The shift in carbon isotope values is a global phenomenon and is interpreted as resulting from carbonate sediment interaction with 12C-rich waters at the end-Permian sea-level fall. However, the oxygen isotope shift is attributed to the effect of meteoric waters with negative oxygen isotope values. The increase in strontium isotope ratios is also consistent with the high rate of terrestrial input at the boundary. The effect of meteoric conditions during diagenesis is evident from vuggy and moldic porosities below the PTB. The following transgression at the base of the Triassic is evident from the presence of reworked fossils and intraclasts resulting from deposition from agitated water.

Fluid geochemistry and geothermometry applications of the Kangding high-temperature geothermal system in eastern Himalayas

High-temperature geothermal systems hold an enormous capacity for generating geothermal energy. The Kangding area is a typical high-temperature geothermal field in the Himalayan Geothermal Belt. Hydrogeochemical, gas geochemical and isotopic investigations were performed to identify and qualify the main hydrogeochemical processes affecting thermal water composition, including mixing and degassing, and then to estimate a reliable reservoir temperature. Nine water samples and four geothermal gas samples were collected and analysed for chemical and isotopic components. The results demonstrate the alkaline deep geothermal water is the mixtures of approximately 75% snow-melt water and 25% magmatic water. It is enriched in Na, K, F, Li and other trace elements, indicating the granite reservoir nature. The shallow geothermal water is the mixtures of approximately 30% upward flow of deep geothermal water and 70% meteoric cold water. High concentrations of Ca, Mg and HCO3 indicate the limestone reservoir nature. There is no remarkable oxygen isotope shift in the geothermal water since the rapid circulation is difficult to trigger off strong water-rock interaction. CO2 is the predominant geothermal gas, accounting for more than 97% of total gases in volume percentage. The concentration of CO2 degassing ranged from 0.4 mol L−1 to 0.8 mol L−1 via geothermometrical modelling. As a result, the geothermal water pH increased from 6.0 to 9.0, and approximately 36% of the total SiO2 re-precipitate. The sources of CO2 are the metamorphism of limestone and magmatic degassing based on the composition of carbon isotope. The appropriate geothermometers of Na-K and Na-Li yield reservoir temperature of 280 °C. The geothermometrical modelling, developed to eliminate the effects of CO2 degassing, yields temperature of 250 °C. The silica-enthalpy mixing model yields temperature of 270 °C with no steam separation before mixing.

Formation of amorphous calcium carbonate in caves and its implications for speleothem research.

Speleothem deposits are among the most valuable continental formations in paleoclimate research, as they can be dated using absolute dating methods, and they also provide valuable climate proxies. However, alteration processes such as post-depositional mineralogical transformations can significantly influence the paleoclimatic application of their geochemical data. An innovative sampling and measurement protocol combined with scanning and transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy is presented, demonstrating that carbonate precipitating from drip water in caves at ~10 °C contains amorphous calcium carbonate (ACC) that later transforms to nanocrystalline calcite. Stable oxygen isotope fractionations among calcite, ACC and water were also determined, proving that ACC is 18O-depleted (by >2.4 ± 0.8‰) relative to calcite. This, in turn, has serious consequences for speleothem-based fluid inclusion research as closed system transformation of ACC to calcite may induce a negative oxygen isotope shift in fluid inclusion water, resulting in deterioration of the original compositions. ACC formation increases the speleothems’ sensitivity to alteration as its interaction with external solutions may result in the partial loss of original proxy signals. Mineralogical analysis of freshly precipitating carbonate at the studied speleothem site is suggested in order to determine the potential influence of ACC formation.

Fluid Inclusion and Stable Isotope Study at the Southeastern Martabe Deposit: Purnama, Barani and Horas Ore Bodies, North Sumatra, Indonesia

AbstractThe Martabe Au–Ag deposit, North Sumatra Province, Indonesia, is a high sulfidation epithermal deposit, which is hosted by Neogene sandstone, siltstone, volcanic breccia, and andesite to basaltic andesite of Angkola Formation. The deposit consists of six ore bodies that occurred as silicified massive ore (enargite–luzonite–pyrite–tetrahedrite–tellurides), quartz veins (tetrahedrite–galena–sphalerite–chalcopyrite), banded sulfide veins (pyrite–tetrahedrite–sphalerite–galena) and cavity filling. All ore bodies are controlled by N–S and NW–SE trending faults. The Barani and Horas ore bodies are located in the southeast of the Purnama ore body.Fluid inclusion microthermometry, and alunite‐pyrite and barite‐pyrite pairs sulfur isotopic geothermometry show slightly different formation temperatures among the ore bodies. Formation temperature and salinity of fluid inclusions of the Purnama ore body range from 200 to 260 C and from 6 to 8 wt.% NaCl equivalent, respectively. Formation temperature and salinity of fluid inclusions of the Barani ore body range from 200 to 220 °C and from 0 to 2.5 wt.% NaCl equivalent and those of the Horas ore body range from 240 to 275 °C and from 2 to 3 wt.% NaCl equivalent, respectively. The Barani and Horas ore bodies are less silicified and sulfides are less abundant than the Purnama ore body.A relationship between enthalpy and chloride content indicates mixing of hot saline fluids with cooler dilute fluids during the mineralization of each of the ore bodies. The δ18O values of quartz samples from the southeast ore bodies exhibit a wide range from +4.2 to +12.9‰ with an average value of +7.0‰. The δ18O values of H2O estimated from δ18O values of quartz, barite and calcite confirm the oxygen isotopic shift to near meteoric water trend, which support the incorporation of meteoric water. Salinity of the fluid inclusions decrease from &gt;5 wt.% NaCl equivalent in the Purnama ore body to &lt;3 wt.% NaCl equivalent in the Barani ore body, indicating different fluid systems during mineralization.The δ34S values of sulfide and sulfate in Purnama range from − 4.2 to +5.5‰ and from +1.2 to +26.7‰, those in the Barani range from − 4.3 to +26.4‰ and from +3.9 to +18.5‰ and those in the Horas ore body range from − 11.8 to +3.5‰ and from +1.4 to +25.7‰, respectively. The δ34S of total bulk sulfur in southeastern ore bodies (Σδ34S) was estimated to be approximately +6‰.The estimated sulfur fugacity during formation of the Purnama and Horas ore bodies is relatively high. It was between 10−4.8 and 10−10.8 atm at 220 to 260 °C. Tellurium fugacity was between 10−7.8 and 10−9.5 atm at 260 °C and between 10−9 and 10−10.6 atm at 220 °C in the Purnama ore body. The Barani ore body was formed at lower fS2, lower than about 10−14 atm at 200 to 220 °C based on the presence of arsenopyrite and pyrrhotite in the early stage, and between 10−14 and 10−12 atm based on the existence of enargite and tennantite in the last stage. © 2016 The Society of Resource Geology

Recrystallization-induced oxygen isotope changes in inclusion-hosted water of speleothems – Paleoclimatological implications

The issue of diagenetic alteration of carbonate deposits in caves (speleothems) has gained increasing importance in recent years, as this process has serious consequences for speleothem-based paleoclimate studies. In this study stable hydrogen and oxygen isotope data of water trapped in fluid inclusions were collected for recently forming stalagmites and flowstones in order to determine how dripwater compositions are reflected and preserved in the inclusion water compositions. Hydrogen isotope compositions were found to reflect dripwater values, whereas the oxygen isotope data were increasingly shifted from the local dripwater compositions with the time elapsed after deposition. The δ18O data are correlated with X-Ray diffraction full width at half maximum values (related to crystal domain size and lattice strain), suggesting that the oxygen isotope shift is related to recrystallization of calcite. Transmission electron microscope analyses detected the presence of nanocrystalline (<50 nm) calcite, whose crystallization to coarser-grained calcite crystals (>200 nm) may have induced re-equilibration between the carbonate and the trapped inclusion water. The Ostwald ripening process provides an explanation for unexpectedly low oxygen isotope compositions in the inclusion water. The detected diagenetic alteration and its isotopic effects should be taken into consideration during sampling strategies and data evaluation as speleothems containing nanocrystalline calcite during their deposition are prone to late-stage oxygen isotope water-carbonate re-equilibration, which may shift the oxygen isotope composition of the inclusion water to more depleted values while the hydrogen isotope composition remains intact.

Expansion and diversification of high-latitude radiolarian assemblages in the late Eocene linked to a cooling event in the southwest Pacific

Abstract. The long-term cooling trend from middle to late Eocene was punctuated by several large-scale climate perturbations that culminated in a shift to "icehouse" climates at the Eocene–Oligocene transition. We present radiolarian micro-fossil assemblage and foraminiferal oxygen and carbon stable isotope data from Deep Sea Drilling Project (DSDP) sites 277, 280, 281, and 283 and Ocean Drilling Project (ODP) Site 1172 to identify significant oceanographic changes in the southwest Pacific through this climate transition (~ 40–30 Ma). We find that the Middle Eocene Climatic Optimum at ~ 40 Ma, which is truncated but identified by a negative shift in foraminiferal δ18O values at Site 277, is associated with a small increase in radiolarian taxa with low-latitude affinities (5 % of total fauna). In the early late Eocene at ~ 37 Ma, a positive oxygen isotope shift at Site 277 is correlated with the Priabonian Oxygen Isotope Maximum (PrOM). Radiolarian abundance, diversity, and preservation increase within this cooling event at Site 277 at the same time as diatom abundance. A negative δ18O excursion above the PrOM is correlated with a late Eocene warming event (~ 36.4 Ma). Radiolarian abundance and diversity decline within this event and taxa with low-latitude affinities reappear. Apart from this short-lived warming event, the PrOM and latest Eocene radiolarian assemblages are characterised by abundant high-latitude taxa. High-latitude taxa are also abundant during the late Eocene and early Oligocene (~ 38–30 Ma) at DSDP sites 280, 281, 283 and 1172 and are associated with very high diatom abundance. We therefore infer a northward expansion of high-latitude radiolarian taxa onto the Campbell Plateau in the latest Eocene. In the early Oligocene there is an overall decrease in radiolarian abundance and diversity at Site 277, and diatoms are scarce. These data indicate that, once the Antarctic Circumpolar Current was established in the early Oligocene (~ 30 Ma), a frontal system similar to present day developed, with nutrient-depleted Subantarctic waters bathing the area around DSDP Site 277, resulting in a more restricted siliceous plankton assemblage.

Geothermal energy resources of Jizan, SW Saudi Arabia

Jizan geothermal province has evolved over an oceanic ridge slice which is under plated a thin continental crust. The area is characterized by high heat flow and high geothermal gradient and hosts several thermal and warm springs whose chemistry indicates a high temperature reservoir within the granites. The geophysical data indicated that the thermal fluids are fault controlled. The residence time of the fluids, estimated based on 14C, is about 33 kilo years. Oxygen isotope shift suggests that the reservoir temperature is around 220°C. It is estimated that the province can generate electricity of the order of 134×106kWh which can be effectively utilized to meet future fresh water demand and save CO2 emissions by decreasing the domestic oil and gas consumption.