Oxygen Isotope Analyses Research Articles

A Neandertal dietary conundrum: Insights provided by tooth enamel Zn isotopes from Gabasa, Spain

The characterization of Neandertals' diets has mostly relied on nitrogen isotope analyses of bone and tooth collagen. However, few nitrogen isotope data have been recovered from bones or teeth from Iberia due to poor collagen preservation at Paleolithic sites in the region. Zinc isotopes have been shown to be a reliable method for reconstructing trophic levels in the absence of organic matter preservation. Here, we present the results of zinc (Zn), strontium (Sr), carbon (C), and oxygen (O) isotope and trace element ratio analysis measured in dental enamel on a Pleistocene food web in Gabasa, Spain, to characterize the diet and ecology of a Middle Paleolithic Neandertal individual. Based on the extremely low δ66Zn value observed in the Neandertal's tooth enamel, our results support the interpretation of Neandertals as carnivores as already suggested by δ15N isotope values of specimens from other regions. Further work could help identify if such isotopic peculiarities (lowest δ66Zn and highest δ15N of the food web) are due to a metabolic and/or dietary specificity of the Neandertals.

Measurements of Sulfur Isotope Composition on Ultrasmall (80 Nanomole) Sulfide and Sulfate Samples by a Modified EA‐IRMS

AbstractThe traditional method for sulfur isotope measurement using EA‐IRMS commonly requires sulfur content greater than 2 μmol. Such a large sample size limits its application to low‐S materials, the size mainly being due to ineffective utilization of sample gas, almost 99.7% of which is discarded with carrier gas through the split port of the continuous‐flow interface. A modified EA‐IRMS system with a gas chromatographic (GC) column and a custom‐built cryogenic concentration device is used in this study. We measured six reference materials to test the performance of this method. The results were consistent with those obtained through traditional EA‐IRMS. Precisions ranging from ±0.24‰ to ±0.76‰ (1σ) can be obtained with samples equivalent to ∼80 nmol sulfur, which were similar to results obtained from an alternative method using an absorption column. Our improved method is a powerful tool for sulfur isotope measurement in ultrasmall sulfide and sulfate samples, which can be further applied to carbon, nitrogen and oxygen isotope analyses of samples at about 100 nmol level.

A new method for phosphate purification for oxygen isotope ratio analysis in freshwater and soil extracts using solid-phase extraction with zirconium-loaded resin.

Phosphate (PO4 ) oxygen isotope (δ18 OPO4 ) analysis is increasingly applied to elucidate phosphorus cycling. Due to its usefulness, analytical methods continue to be developed and improved to increase processing efficiency and applicability to various sample types. A new pretreatment procedure to obtain clean Ag3 PO4 using solid-phase extraction (SPE) with zirconium-loaded resin (ZrME), which can selectively adsorb PO4 , is presented and evaluated here. Our method comprises (1) PO4 concentration, (2) PO4 separation by SPE, (3) cation removal, (4) Cl- removal, and (5) formation of Ag3 PO4 . The method was tested by comparing the resulting δ18 OPO4 of KH2 PO4 reagent, soil extracts (NaHCO3 , NaOH, and HCl), freshwater, and seawater with data obtained using a conventional pretreatment method. PO4 recovery of our method ranged from 79.2% to 97.8% for KH2 PO4 , soil extracts, and freshwater. Although the recovery rate indicated incomplete desorption of PO4 from the ZrME columns, our method produced high-purity Ag3 PO4 and accurate δ18 OPO4 values (i.e., consistent with those obtained using conventional pretreatment methods). However, for seawater, the PO4 recovery was low (1.1%), probably due to the high concentrations of F- and SO4 2- which interfere with PO4 adsorption on the columns. Experiments indicate that the ZrME columns could be regenerated and used repeatedly at least three times. We demonstrated the utility of ZrME for purification of PO4 from freshwater and soil extracts for δ18 OPO4 analysis. Multiple samples could be processed in three days using this method, increasing sample throughput and potentially facilitating more widespread use of δ18 OPO4 analysis to deepen our understanding of phosphorus cycling in natural environments.

A rapid high‐precision analytical method for triple oxygen isotope analysis of CO2 gas using tunable infrared laser direct absorption spectroscopy

RationaleThe simultaneous analysis of the three stable isotopes of oxygen—triple oxygen isotope analysis—has become an important analytical technique in natural sciences. Determination of the abundance of the rare 17O isotope in CO2 gas using magnetic sector isotope ratio mass spectrometry is complicated by the isobaric interference of 17O by 13C (13C16O16O and 12C16O17O, both have mass 45 amu). A number of analytical techniques have been used to measure the 17O/16O ratio of CO2 gas. They either are time consuming and technically challenging or have limited precision. A rapid and precise alternative to the available analytical methods is desirable.MethodsWe present the results of triple oxygen isotope analyses using an Aerodyne tunable infrared laser direct absorption spectroscopy (TILDAS) CO2 analyzer configured for 16O, 17O, and 18O combined with a custom gas inlet system. We evaluate the sensitivity of our results to a number of parameters. CO2 samples with a wide range of δ18O values (from −9.28‰ to 39.56‰) were measured and compared to results using the well‐established fluorination‐gas source mass spectrometry method.ResultsThe TILDAS system has a precision (standard error, 2σ) of better than ±0.03‰ for δ18O and ±10 per meg for Δ′17O values, equivalent to the precision of previous analytical methods. Samples as small as 3 μmol CO2 (equivalent to 300 μg CaCO3) can be analyzed with a total analysis time of ~30 min.ConclusionsWe have successfully developed an analytical technique for the simultaneous determination of the δ17O and δ18O values of CO2 gas. The precision is equal to or better than that of existing techniques, with no additional chemical treatments required. Analysis time is rapid, and the system is easily automated so that large numbers of samples can be analyzed with minimal effort.

Strontium and stable oxygen isotope analysis in the Classic and Postclassic northern Maya lowlands of the Yucatan Peninsula: An analysis of social and sex-related reasons for population movement

Yucatan Peninsula’s northern Maya lowlands witnessed intense socio-political and commercial changes during Classic and Postclassic periods. Migration was part of many important changes, and isotopic analyses allow quantification of the extent of population movement and the migrants’ potential places of origin by sex, age, and other social determinants. The purpose of the present analysis is to highlight regional migration patterns using published data that move beyond site-specific interpretations. Overall, the picture that emerges is that mobility in the region was not limited to one specific sex or age group, nor was it the prerogative of any social level. A variety of reasons lay behind population movement, including trade, kinship, marital residence, and elite marriage alliances that served to reinforce power or establish new outposts. Regional analyses and comparison of large datasets will provide a better understanding of this complex and tangled process that shaped society on the Yucatan peninsula for millennia.

A new sampling method with zirconium‐loaded resin for phosphate oxygen isotope analysis in oligotrophic freshwater systems

The phosphate oxygen isotope ratio ( ) is a useful technique to trace the sources and biogeochemical cycles of phosphorus (P) in aquatic ecosystems. However, has not been widely used in oligotrophic freshwater systems due to technical and methodological difficulties in collecting sufficient phosphate (PO4 ) for the analysis, which sometimes requires hundreds of liters of the water sample. In this study, a new approach (PaS-Zir) was developed for the analysis in oligotrophic freshwater systems using zirconium (Zr)-loaded (ZrIRC) resin, which has a high affinity for PO4 . ZrClO2 was added to Amberlite IRC748 to obtain the ZrIRC resin. The adsorption/desorption experiment using KH2 PO4 with a known value of was conducted to determine the adsorption/desorption properties of the resin and the likelihood of isotopic fractionation. By installing mesh bags filled with the resin, the PaS-Zir approach was used in two rivers with low PO4 concentrations (0.2 and 5.3μmol/L). A conventional sampling method was also performed in the study river with a higher PO4 concentration to validate the efficacy of the PaS-Zir method. The adsorption/desorption experiment demonstrated that the ZrIRC resin possessed a sufficient adsorption capacity (153 μmol/resin-mL) and exhibited little isotopic fractionation during the adsorption/desorption processes. Using the PaS-Zir method, we were able to collect sufficient PO4 samples for the analysis from the rivers within at least 4 days of mesh bag installation. The values (14.2‰ ±0.2‰) obtained using the PaS-Zir method were comparable to those obtained using the conventional method (14.0‰ ±0.03‰). We proved that the PaS-Zir method is applicable to oligotrophic freshwater systems and is generally more efficient than the conventional method. In addition, our method is useful for improving the understanding of the P dynamics of oligotrophic ecosystems because of the extremely low concentration of PO4 commonly found in them, which are often prone to P pollution.

Oxygen isotopes and human mobility in Middle and Late Holocene hunter-gatherer groups from the eastern Pampa-Patagonia transition (Argentina)

This work seeks to explore human mobility in the lower course of the Colorado River (Argentina) during the Middle and Late Holocene (ca. 5900-250 years BP) through the analysis of stable oxygen isotopes (δ18O) of bone bioapatite. The δ18O values are interpreted and compared with those from North Patagonia and Western Pampas to evaluate mobility at a regional scale. Forty-one adult individuals of both sexes from 12 archaeological sites were analyzed. δ18Oc values were transformed into drinking water (δ18Odw). The results were compared with the hydrological baseline generated for central-eastern North Patagonia and real rainfall data and predictive rainfall models. ẟ18Oc values indicate higher values in individuals corresponding to Middle Holocene (−0.7‰) compared with the Initial Late Holocene (−3.1‰) and Final Late Holocene (−2.3‰) and statistically significant differences between Middle Holocene and Late Holocene. Based on the δ18Odw values, 17.1% (7/41) correspond to hydrologic zones defined for central-eastern North Patagonia, and 48.8% to the real and predictive rainfall models. Although differences in δ18Odw values are observed between the Middle and Late Holocene, it is not yet possible to propose precise human mobility geographical directions in the study area. Nevertheless, during the Late Holocene, the δ18Oc values showed that individuals buried in the study area could have shared some water sources with those from Western Pampas and nearby sectors from Northeastern Patagonia, such as the lower course of the Negro River.

Lutrinae Bonaparte, 1838 (Carnivora, Mustelidae) from the Plio-Pleistocene of the Lower Omo Valley, southwestern Ethiopia: systematics and new insights into the paleoecology and paleobiogeography of the Turkana otters

We describe otter remains (Lutrinae Bonaparte, 1838) from the Plio-Pleistocene of the Lower Omo Valley of southwestern Ethiopia. We report isolated lower and upper teeth of Torolutra sp. dated to c. 3.3 Ma, dental specimens and a femur of Enhydriodon Falconer, 1868, attributed to a new species, dated between c. 3.4 Ma and 2.5 Ma, as well as a humerus of Lutrinae indet. dated between c. 1.9 Ma and 1.8 Ma. The new species Enhydriodon omoensis n. sp. is the largest species of the genus discovered so far. It is even larger than its close relative E. dikikae Geraads, Alemseged, Bobe & Reed, 2011, a Pliocene lion-sized otter from the Afar region and potentially from eastern Turkana. Based on stable oxygen and carbon isotope analyses, we found that Enhydriodon from the Lower Omo Valley could have been terrestrial and fed on both aquatic and terrestrial prey, acquired by either hunting or scavenging. It filled a unique ecological niche in the past communities co-existing with australopithecines. Enhydriodon and Torolutra Petter, Pickford & Howell, 1991 went extinct in Africa around the Plio-Pleistocene transition, along with many large-sized and ecologically specialized carnivorans. This extinction event could be linked to the many geological, climate, and biotic changes occurring in the eastern African rift during this period, notably the incursion of early hominins into the carnivore guild.

A single extensional, diffuse, ductile fault zone in the Goriganga section, western Himalaya: Part of the upper South Tibetan Detachment System?

The Trans-Himadri Detachment Fault (T-HDF) of the Kumaon region of western Himalaya, a north-easterly steeply dipping discrete brittle/semi-brittle fault, had previously been regarded as a strand of the South Tibetan Detachment System (STDS). Yet, elsewhere in the Himalaya, the STDS is defined as a diffuse, ductile low-angle normal-sense shear zone. This aspect of the STDS remained conjectural and was even refuted by various workers in the Goriganga valley in the Kumaon. We have systematically documented the STDS as a low-angle, northerly dipping, ductile, diffuse shear zone, with a true thickness of >5 km in this transect. In the present scenario, the shear zone is located only within the psammo-pelitic basal part of the Tethyan Sedimentary Sequence (TSS), and bypassed the rock units of the Greater Himalayan Sequence (GHS). Multiple grain-statistical parameters of mylonitized micaceous quartzites point to an anastomosing architecture which displays a single precursory damage zone and a wider core for the entire STDS shear zone. The 40Ar*/39Ar geochronology and oxygen isotope analysis of the micas in mylonites demonstrated that the STDS evolved in weak lithologies, between c.14–11 Ma, at ∼300–350 °C ambient temperature, at or immediately below the brittle-plastic transition depth in the quartzo-feldspathic continental crust.Consideration of similar range of optimum ages of cessation of the extensional activity and already published timings of the end of brittle motion of the STDS in adjacent regions suggests that this wide diffuse shear zone is a deeper counterpart of the brittle upper STDS. This is in sharp contrast to the exposures of the detachment elsewhere in the Himalaya, where diffuse zone demonstrably constitutes the lower branch of this detachment. This finding has potential implications on overall understanding of the deformation related to the STDS and late Miocene geodynamic evolution of the GHS in this region.

Paleoceanographic reconstruction of the Ediacaran Dengying Formation, Sichuan Basin, Southwest China: Implications for the origin of Precambrian microbial carbonates

Abundant microbial carbonates with well-preserved primary textures occur in the upper Ediacaran Dengying Formation in the Sichuan Basin, southwest China, providing an opportunity to study the paleoceanographic conditions and the origin of Precambrian microbial carbonates. However, paleoenvironmental studies of these microbial carbonates are relatively rare, especially with respect to the comparison between the upper and lower parts of the Dengying Formation. In this paper, we present new analyses of carbon and oxygen isotopes and major, trace, and rare earth elements (REEs) for carbonate rocks from the Dengying Formation, in order to reveal the paleoceanographic redox and salinity conditions of the seawater from which these rocks were deposited. These rocks have shale-normalized REE and Y patterns that display weak negative Ce anomalies, weak positive Eu anomalies, and moderate middle REE enrichment, indicating the suboxic seawater for their deposition. From the lower to upper parts of the Dengying Formation, negative Ce anomalies become more prominent, while positive Eu anomalies and middle REE enrichment weaken, suggesting a gradual increase in the seawater oxygen concentration. The heavier oxygen isotopes of the carbonate matrixes and fibrous cements in the second member of the lower part of the Dengying Formation reflect a higher seawater salinity, conforming to the thick evaporates in the second member. The elevated oxygen content and decreased salinity in the seawater promoted the emergence of metazoans that inhibited the growth of microbes, causing the decreasing development of microbial carbonates in the upper part of the Dengying Formation compared to the lower part.

First estimates for Jurassic seawater temperatures based on oxygen isotope analyses of calcitic fossils from Central Iran: Evidence for a major plate tectonic shift?

• First absolute seawater temperatures for the Jurassic of Iran are estimated. • Oxygen isotope analyses of calcitic fossils indicate a significant long-term warming. • Warming is explained by plate tectonic shift of Central Iran into lower latitudes. • Warming also caused changes in sedimentation and ecosystem composition. • Plate tectonics drive regional long-term climate patterns in the Middle-Late Jurassic. Stable oxygen isotope values of calcitic marine fossils (δ 18 O shell ) were used to calculate the first absolute seawater temperature estimates for the Jurassic of Central Iran. Results indicate a significant long-term warming in the study area through the Middle to Late Jurassic of around 6 °C or more (0.3 to 0.4 °C per million years). Following recent methodological advances in temperature reconstructions, the δ 18 O shell values of bivalves translate into water temperatures slightly warmer than in today’s oceans at comparable latitudes with averages of 26.6 °C in the Middle Jurassic and 32.1 °C in the Late Jurassic. Belemnites would indicate still warmer temperatures, but these values might be less reliable and partly overestimated due to potentially altered specimens. The recorded long-term warming can be explained by a concurrent major plate tectonic shift of Central Iran from temperate to tropical latitudes. The gradual influence of this southward drift is also seen by changes in sedimentation and ecosystem composition. This way, the stable oxygen isotope record of Central Iran is further evidence for the strong impact of plate tectonics on regional long-term climate patterns in the Middle and Late Jurassic.

A detailed record of early solar system melting in the carbonaceous achondrites Northwest Africa 7680 and 6962

AbstractDetailed textural and geochemical analyses of the carbonaceous achondrites Northwest Africa (NWA) 7680 and NWA 6962 support a rapid progression of thermal events, by similar processes, on the same parent body. The achondrites have olivine compositions of Fa44.8 and Fa47.4 for NWA 7680 and NWA 6962, respectively. Replicate oxygen isotope analyses of grains and bulk powders from NWA 7680 yielded average Δ17O values of −1.04 ± 0.03‰ and −1.00 ± 0.05‰, respectively, which is identical to that reported for NWA 6962. The whole rock ɛ54Cr compositions are also equivalent for NWA 7680 and NWA 6962 (1.36 ± 0.05 and 1.30 ± 0.05, respectively). Both meteorites are plagioclase‐rich, and NWA 7680 is also Fe‐metal‐rich, suggesting they both formed via differentiation processes that resulted in the pooling of partial melt products. Major element geochemical trends show that both rocks could be formed through the melting of chondritic material on a CR chondrite‐like parent body. This is consistent with oxygen isotope and chromium isotope compositions. Intrusion of a late‐stage melt is evident in both meteorites and the crystallization products include silica‐rich, alkali‐deficient nepheline. The late‐stage liquid has partially melted and mixed with primary plagioclase in NWA 6962. In contrast, the late‐stage liquid was often restricted to grain boundaries in NWA 7680, leaving some of the primary plagioclase crystals intact. In situ dating of NWA 7680 phosphate minerals (merrillite and fluorapatite) reveals that it has not experienced long duration thermal metamorphism, or impact‐related Pb loss and age resetting since 4578 ± 17 Ma (207Pb/206Pb age ± 2σ, within error of solar system age). Phosphates associated with the late‐stage melt in NWA 6962 yield a 207Pb/206Pb age of 4556.6 ± 8.0 Ma (2σ) within 2σ of the NWA 7680 age. These early dates indicate that the observed chromium isotope signatures in these meteorites were not introduced by a later high‐temperature event, such as late impact accretion processes. These data are consistent with a rapid separation of inner and outer solar system chemical reservoirs, planetesimal melting, differentiation, and cooling, all within several million years of calcium‐aluminum‐rich inclusion formation.

Natal origin of Pacific bluefin tuna Thunnus orientalis determined by SIMS oxygen isotope analysis of otoliths.

Accurate understanding of changing population dynamics associated with climate change is critical for managing highly migratory fish species. However, long-term data on population dynamics and the resulting recruitment variability is still lacking for many species, making it difficult to predict and integrate the effects of ocean warming into management schemes. In this study, high-resolution stable oxygen isotope (δ18O) analysis was performed on the otoliths of adult Pacific bluefin tuna Thunnus orientalis using secondary ion mass spectrometry (SIMS) to determine the natal origin of an individual fish. The core δ18Ootolith corresponding to the larval stage greatly varied among the individuals, indicating that the larvae experienced a wide range of thermal environments. The non-hierarchical cluster analysis performed on the core δ18Ootolith grouped fish into those with higher δ18Ootolith (lower temperature) and those with lower δ18Ootolith (higher temperature), most likely representing relative temperature difference experienced between fish born in the Sea of Japan and in the Nansei Islands area. The Nansei Islands area cluster showed more variability in the early otolith growth indicating a longer spawning season, which is consistent with the observed longer spawning duration in this area. The absolute temperature estimates based on the SIMS-measured core δ18Ootolith were significantly higher than those expected from sea surface temperature data, suggesting the effects of matrix-related bias on the temperature offsets. The relative temperature difference, however, matched well with the known spawning temperature range of the two spawning grounds. The recruitment contribution from each spawning ground (all year-classes pooled, n = 51) was 45% in the Sea of Japan and 55% in the Nansei Islands area. Overall, this study demonstrated the effectiveness of SIMS δ18Ootolith analysis for investigating the natal origin of fish and its potential application in fish population dynamics studies.

Characteristics and Genesis of Alkaline Lacustrine Tight Oil Reservoirs in the Permian Fengcheng Formation in the Mahu Sag, Junggar Basin, NW China

Through optical microscopic examination, scanning electron microscope analysis, whole rock X-ray diffraction analysis, X-ray fluorescence spectrum analysis, carbon and oxygen isotope analysis, and temperature measurement of fluid inclusions, the characteristics and formation mechanism of the alkaline lacustrine tight oil reservoirs of the Permian Fengcheng Formation in the Mahu Sag of the Junggar Basin have been systematically studied, and a genetic model has been proposed. Porosity of tight oil reservoirs of the Fengcheng Formation in the Mahu Sag is mostly less than 4%, with permeability mostly less than 0.1 mD. The lithology of the Fengcheng Formation in the Mahu Sag is mainly tuff, and the authigenic minerals mainly consist of feldspar, quartz, dolomite, and salt minerals (e.g., shortite, trona). The authigenic feldspar and quartz of the Fengcheng Formation in the Mahu Sag mainly originate from devitrification of volcanic glass in pyroclastic rocks. Reservoir space is dominated by dissolution pores of feldspar and salt minerals, followed by intercrystalline pores among feldspar, quartz, and other minerals formed by devitrification. Fractures are mainly comprised of shrinkage fractures, structural fractures, and bedding seans. The Permian Fengcheng Formation was mainly formed in an alkaline lake in the Mahu Sag, and the alkaline lacustrine sedimentary setting plays a decisive role in the formation of the tight oil reservoirs of the Fengcheng Formation. Volcanic glass in the tight oil reservoirs was generally devitrified within the alkaline lacustrine diagenetic fluid in the early diagenetic stage, and the devitrified micropores become an important reservoir space. Feldspars and salt minerals were mainly dissolved by acidic fluids generated by burial thermal evolution of the alkaline lacustrine source rocks of the Fengcheng Formation in the Mahu Sag, which produces the most developed dissolution pores in the tight oil reservoir. The abnormal high pressure formed by the early hydrocarbon generation and expulsion of the alkaline lacustrine source rocks in the Fengcheng Formation is one of the main reasons for porosity preservation. In the alkaline lake sedimentary environment of the Fengcheng Formation, widespread dolomitization and precipitation of a large number of salt minerals in the early diagenetic stage resisted partial compaction, which not only effectively protected early porosity, but also provided material conditions for dissolution porosity enhancement.

Fluid origin and critical ore-forming processes for the giant gold mineralization in the Jiaodong Peninsula, China: Constraints from in situ elemental and oxygen isotopic compositions of quartz and LA–ICP–MS analysis of fluid inclusions

The Jiaodong Peninsula, China, is one of the largest gold provinces in the world. During a short time interval in the Early Cretaceous, over 5000 t of gold were accumulated there. The mechanisms controlling the focused Au deposition and the origins of massive amounts of auriferous fluids are still controversial. Quartz–sulfide lode mineralization (Linglong-type) and disseminated/stockwork mineralization (Jiaojia-type) are the two major mineralization styles in the Jiaodong Peninsula. Herein, we conducted in situ textural, elemental and oxygen isotopic analyses using scanning electron microscopy (SEM), laser ablation-inductively coupled plasma-mass spectrometry (LA–ICP–MS) and secondary ion mass spectrometry (SIMS) on quartz from different hydrothermal stages and depths for three representative Linglong-type (Linglong deposit) and Jiaojia-type (Xiadian and Jiangjiayao deposits) gold deposits in the northwestern Jiaodong Peninsula, with the aim to constrain the ore-forming processes. The LA–ICP–MS analysis of individual fluid inclusions was also conducted to unravel the origin of the auriferous fluids. The results show that from the pre-mineralization to the ore-forming stages in the Linglong-type mineralization, the homogenization temperatures and salinities of fluid inclusions and the δ18Oquartz values change slightly, but the Al concentrations of quartz decrease continuously. Combined with the coexistence of CO2- and H2O-rich fluid inclusion endmembers, these trends indicate the increase of pH induced by CO2 degassing (fluid–fluid unmixing), which led to focused Au deposition. The quartz grains from the Jiaojia-type mineralization typically show a homogeneous texture with well-correlated lithophile elements (e.g., K, Al and Rb), which are distinct from those of the Linglong-type that are characterized by oscillatory zoning with much higher Al concentrations and δ18Oquartz values. These phenomena indicate that enhanced fluid–rock interaction occurred in the Jiaojia-type mineralization. In addition, the δ18Oquartz values show an increase from deep to shallow depths. In combination with thermodynamic modelling, it suggests decreasing fluid–rock interaction with decreasing depth. The above results corroborate that multiple mechanisms led to the efficient Au deposition in the Jiaodong Peninsula. Fluid–fluid unmixing typically occurred in the Linglong-type mineralization, while fluid–rock interaction was dominant in the Jiaojia-type mineralization. The different mechanisms might render mining challenging due to the changeable locations of favorable Au unloading.The LA–ICP–MS results of fluid inclusions suggest that the ore-forming fluids are metamorphic fluids rather than magmatic–hydrothermal fluids. In combination with the isotopic compositions of ores showing considerable mantle affinities and large-scale mafic underplating occurring beneath the study region, we propose a new genetic model that accounts for the origin of the auriferous fluids. The new model invokes the devolatilization of previously emplaced H2O- and Au-rich amphibole cumulates through amphibolite- to granulite-facies metamorphism in the middle–lower crust. It suggests an alternative way to generate the ‘orogenic-like’ gold deposits.

Response of Travertine Dam to Precipitation over the Past 800 Years in Zabuye Salt Lake, Southwestern Tibetan Plateau

The Tibetan Plateau is known as the core area of the third pole of the Earth and is a key area for global climate change research. This study uses the Zabuye Salt Lake travertine dam as the research object and U–Th dating as the chronological framework and proposes that the carbon and oxygen isotopes of travertine can be used as a precipitation index through the analysis of hydrogen and oxygen isotopes of spring water, and petrology, mineralogy, carbon and oxygen isotopes of travertine. The precipitation records of Zabuye Salt Lake over the last 800 years show a dry condition in 1191–1374 AD (Medieval Warm Period), a humid condition in 1374–1884 AD (Little Ice Age), and a dry condition in 1884–1982 AD (Current Warn Period), indicating a warm–dry/cold–moist climate pattern, which is consistent with precipitation records from many places on the Tibetan Plateau. We preliminarily point out that travertine can record the evolution of paleoprecipitation (paleomonsoon) at least on the decadal–centennial scale. The Indian summer monsoon has been the main factor influencing precipitation change in Zabuye Salt Lake over the past 800 years, and the change in evapotranspiration intensity caused by temperature change driven by solar radiation is also an important factor affecting dry–moist change.

SIMS matrix effects in oxygen isotope analysis of olivine and pyroxene: Application to Acfer 094 chondrite chondrules and reconsideration of the primitive chondrule minerals (PCM) line

The instrumental bias (here expressed as bias*, the difference relative to San Carlos Olivine, SC-Ol) of oxygen isotopes in secondary ion mass spectrometry (SIMS) analyses of olivine and pyroxene were investigated. Sixteen olivine (Fo0–100), nine orthopyroxene (En70–100Wo0–3), and three clinopyroxene (En28-49Wo45–50) reference materials (RMs) were utilized. The values of bias* are nearly invariant (within 0 ± 0.5‰) among magnesian olivine (Fo ≥60) RMs but decrease systematically with increasing Fe molar fraction down to ~ −10‰ (Fo0). The session-to-session variability of bias* for Fo ≥60 olivines is ≤0.3‰ but becomes slightly larger for more Fe-rich compositions (≤1.5‰). Orthopyroxene RMs have a narrow range of bias* values (−1.7‰ to −2.6‰) that show session-to-session variability ≤0.3‰; correspondingly, the sputter rates are similarly low and resemble those of Fo ≥60 olivines. Clinopyroxene RMs bias* values (−0.2‰ to +1.2‰) are more variable and have larger session-to-session variability (≤0.8‰), which appear to be independent of sputter rates. Bias* of the same RMs change slightly from session to session with different analytical settings (≤0.6‰ for Fo ≥60 and as much as 2‰ for fayalite) so that equations of bias* as a function of Fo, En, and Wo should be determined for each SIMS session by the analyses of multiple RMs.The new suite of olivine and pyroxene RMs with expanded composition range were used to correct the instrumental biases during oxygen three-isotope analysis of olivine and low-Ca pyroxene in chondrules of the ungrouped Acfer 094 chondrite, from which the primitive chondrule minerals (PCM, δ18O vs. δ17O) line was originally derived. The PCM line is considered to be a mixing trend of two extreme primary oxygen isotope reservoirs of solids in the early solar system. However, this new dataset, with better analytical precision and instrumental bias correction, allows two oxygen isotope trends to be clearly identified. One is represented by chondrules that plot on or above the PCM line, likely linked to ordinary chondrite (OC)-like materials. A second trend is represented by the major chondrule population in this chondrite that defines a regression line of δ17O = (0.968 ± 0.022) × δ18O − (3.46 ± 0.10) (MSWD = 2.0), consistent with recent oxygen isotope data of chondrules in carbonaceous chondrites (i.e., CV, CK, CO, and CM). We propose that this regression line represents a mixing of two oxygen isotope reservoirs (possibly 16O-rich solids and 16O-poor H2O ice) in the outer solar system and likely resulting from the separate evolutions of isotope reservoirs after the “Jupiter divide” built up.

The High-Status Late Medieval Skull Shaped Relic in Turku Cathedral Finland – Study of the Origin with Oxygen and Strontium Isotope Analyses

The relics and associated reliquaries of Turku Cathedral are among the most significant early Christian artefacts in Finland preserved in situ. Despite their importance, they have not been the focus of scientific enquiry for a number of decades. This study has focused on one skull shaped relic, although the origin and name of its associated saint remains unknown. The relic is the only such example with high-status decoration in the Turku Cathedral collection and is covered with a red silk decorated with yellow yarn. The bones and fabric have been dated from the beginning of the modern era to the 13th century AD, and variance among the radiocarbon (<sup>14</sup>C) dates acquired from the bones shows the remains incorporate several individuals. In this study, oxygen and strontium isotope compositions were determined from fragmented bones and textiles. The results are the first isotope analysis performed on this collection housed in Turku Cathedral. Analysis indicates an origin from outside Finland, possibly elsewhere in northern Europe or an Alpine region. This helps take us a little closer to understanding the mystery associated with this sacred artefact.

Impact of CO2 generated from coal-measure source rocks on physical properties of reservoirs — A case study of the Sulige gas field in the Ordos Basin, Northwest China

We did have done thermal simulation experiments on coal-measure source rocks, carbon and oxygen isotope analysis of calcite cement in tight sandstone reservoirs, as well as uniform temperature and composition determination of fluid inclusions to illustrate the relationship between the gas generation of coal-measure source rocks and reservoir densification. Coal-measure source rocks produce a considerable amount of CO2 during the entire thermal simulation experiment, especially in the initial stage with the carbon isotope of CO2 ranging from −21.2‰ to −11.6‰, which indicates organic origin. The carbon isotope value of CO2 becomes heavier as the degree of thermal maturation increases. The carbon isotope of calcite cements in the tight sandstone reservoirs of the lower Shihezi Formation is in the range of −13‰ to −4.7‰, which may have the same origin as the CO2 produced during the gas generation of coal-measure source rocks. CO2 derived from coal-measure source rocks can promote the formation of cement, which may be a key reason for the densification of sandstone reservoirs. The fluid inclusions related to oil and gas charging which are mainly methane and carbon dioxide also can confirm this conclusion. At the same time, the CO2 also will impact the dissolution of potash feldspar, albite, and other minerals as well as the reprecipitation of clay minerals, resulting in a more complicated variation of porosity and permeability. CO2 is of great significance in improving oil recovery and the application of carbon capture, utilization, and storage. Studying the influence of CO2 generated from coal-measure source rocks on the physical properties of reservoirs can provide guidance for the mechanism of CO2 storage in the ground.

Insights into the Ore Genesis of the Harla Gold Deposit in Eastern Tianshan, NW China: Evidence from Geology, Fluid Inclusions, and H-O-C-S-Pb Isotopes

The Harla gold deposit is located on the eastern segment of the Kanggur-Huangshan ductile shear belt in Eastern Tianshan, on the southern margin of the Central Asian Orogenic Belt. The orebodies show close spatial association with NEE-trending faults and are hosted in volcanic rocks of the Lower Carboniferous Xiaorequanzi Formation. Three mineralization stages were recognized: an early stage characterized by specularite–pyrite–quartz mineralization, an intermediate stage with pyrite–chalcopyrite–gold–quartz genesis, and a late stage defined by sulfide-poor calcite and quartz veins. Three types of fluid inclusions (FIs) were recognized: daughter mineral-bearing triphase FIs (S-type), liquid-dominated biphase FIs (LV-type), and liquid-only monophase FIs (L-type). S- and LV-type FIs entrapped in the early stage show similar homogenization temperatures (Th) at 216–229 °C and 199–222 °C. However, they display contrasting salinities of 32.2–33.4 and 6.7–8.9 wt.% NaCl eqv., respectively. LV-type FIs entrapped in the intermediate stage display Th of 163–191 °C, with salinities of 5.6–7.4 wt.% NaCl eqv. LV-type FIs occur in the late stage display Th of 135–258 °C and salinities of 3.7–5.6 wt.% NaCl eqv. Insights from hydrogen, oxygen, and carbon isotope analyses (δ18OH2O = −10.7 to 3.3‰, δDH2O = −88.1 to −61.4‰, δ13CH2O = −8.9 to −6.2‰), combined with FI characteristics, indicate that the ore-forming fluids were derived from a hybrid source of magmatic and meteoric water, with the latter becoming dominant in the later stage. Sulfide and lead isotopic compositions (δ34Spyrite = 0.2 to 2.5‰, 206Pb/204Pb = 17.709–18.273, 207Pb/204Pb = 15.483–15.569, 208Pb/204Pb = 37.533–37.754) suggest that ore-forming materials were mainly derived from wall rocks (Xiaorequanzi Formation rocks and plagiogranite). By integrating geological background work and fluid inclusion analyses, as well as isotope data, we conclude that the Harla gold deposit is an epithermal-type deposit.