Hydrogen Isotope Values Research Articles

Hydrochemical, isotopic, and dissolved gas characterization of groundwater in Gariz aquifer, Southwest of Yazd Province, central Iran

Here we discussed the results of the first geochemical investigation of the fluids (groundwater and the associated gases) emerging in the southwest of Yazd Province. We carried out two surveys, one in July 2019 and the second in September 2019s, in the region of the Gariz aquifer (central Iran). We focused our attention to 1) the chemistry of the water (major and minor constituents coupled to the stable isotopes of oxygen and hydrogen), 2) the chemical composition of dissolved gases in water together with 3) the isotopic composition of Helium (3He/4He) and 4) the dissolved carbon in water (δ13CTDIC). Hydrogen and oxygen isotope values of groundwater display a fairly narrow range and indicate that the waters are of meteoric origin. On the base of the major ions chemistry, the bulk of the water samples are classified as Ca-HCO3, CaCl and NaCl types. The groundwater chemistry is mainly influenced by the interaction with CO2-rich fluids, leakage of chlorinated saline water into the alluvial aquifer, and silicate dissolution. High dissolved carbon contents, mainly as bicarbonate ion, reflect the noticeable interaction of the groundwater with CO2-rich fluids. CO2 is the dominant gaseous component in most samples and its amount is always greater with respect to a water in equilibrium with the atmosphere (Air Saturated Water, ASW). Such excess of CO2 contents (more than 730 cc/l STP) dissolved in groundwater also supports the presence of a deep source of CO2-rich gas. The computed δ13C(CO2) in equilibrium with the groundwater highlight a mixing in different proportion between an inorganic deep sourced CO2 (13C-enriched) and organic CO2 (13C-depleted). We also used the helium isotopes as a tools to figure out the origin of helium in the aquifer (air vs. mantle, and crust). The collected samples show a contribution of mantle-derived He in the Gariz aquifer up to (~45%) and the crust suggesting that at regional scale the tectonic discontinuities had a connection with the mantle or magmatic intrusions migrated through the crust transporting mantle volatiles to shallow crustal layers. However, we cannot infer the timing of this possible magmatism at depth in the complex tectonic evolution of the area.

Paleoaltimetry of the Western Andes in Northern Chile (∼18.5–19.5°S)

Establishing the timing of surface uplift in the Central Andes is essential for evaluating the geodynamic mechanisms responsible for mountain building and their role in the development of dry conditions along the western coasts of Peru and Chile. Here, we present new stable hydrogen isotopic values from stream waters and hydration water in volcanic glass from northern Chile (18.5–19.5°S) that show that the Western Cordillera was already elevated by the early Miocene. The hydrogen isotopic values of reconstructed surface waters obtained from ancient and modern volcanic glass indicate that the Western Cordillera in northern Chile attained modern elevations by at least 22.8 Ma. When combined with paleoaltimetric records from the Altiplano and northwestern Puna, these results demonstrate that surface uplift of the Andean plateau was a time-transgressive process that varied not just from west to east but also from north and south along the strike of the orogen. Our paleoaltimetry reconstruction also suggests that the Western Cordillera has blocked moisture coming from the east since at least the early Miocene, consistent with previously published evidence of arid-semiarid conditions in the Atacama Desert. However, hyperaridity on the western Andean slope developed later and appears to correspond with the timing of uplift in the Eastern Cordillera and Altiplano. Our results suggest that the growth of the Central Andean rain shadow relied not only on the elevation of the Western Cordillera but also on the widening of the plateau.

Inverse hydrogen isotope fractionation indicates heterotrophic microbial production of long-chain n-alkyl lipids in desolate Antarctic ponds.

Long-chain (>C25 ) n-alkyl lipids have long been considered biomarkers for higher plant leaf waxes and widely applied for paleoclimate and paleoenvironmental reconstructions. However, recent experimental and lacustrine sediment studies suggest long-chain n-alkanes and n-alkanoic acids can also be produced by aerobic microbes, probably heterotrophic microbes based on carbon isotope data. Here we show that sedimentary long-chain n-alkanes and n-alkanoic acids in two desolate Antarctic ponds where vascular plants are absent in the surroundings display hydrogen isotopic values up to 300 per mil higher than those of lake water. It is the first time that such strongly inverse or reduced hydrogen isotopic fractionation of lipid biomarkers is observed in natural sediment samples. Based on recent extensive experimental data on microbial hydrogen isotopic fractionation, our data can only be explained by the predominant production of long-chain n-alkanes and n-alkanoic acids from heterotrophic micro-organisms. Together with preliminary 16S rRNA gene sequencing data, our results represent the first unambiguous example of predominant heterotrophic microbial production of long-chain n-alkyl waxes in a natural environment.

Hydrologic Changes Drove the Late Miocene Expansion of C4 Grasslands on the Northern Indian Subcontinent

AbstractModern tropical and subtropical C4 grasslands and savannas were established during the late‐Miocene and Pliocene, over 20 Myr after evolutionary originations of the C4 photosynthetic pathway. This lag suggests environmental factors first limited and then favored C4 plants. Here, we examine the timing and drivers for the establishment of C4 grasslands on the Indian Subcontinent using carbon and hydrogen isotope signatures of plant‐wax n‐alkanes recovered from turbidites in the Bengal Fan. Like prior studies, we find C4 ecosystems in the Ganges‐Brahmaputra catchment first emerged at 7.4 Ma and subsequently expanded between 6.9 to ∼6.0 Ma. Hydrogen isotope values varied from 10.2 to 7.4 Ma and then increased after 7.4, which suggests intermittent drying began before the establishment of C4 grasslands with further drying at the onset of C4 expansion. Synthesis of published plant fossil data from the Siwalik Group of the Himalayan foreland basin documents an ecosystem trajectory from evergreen tropical forests to seasonally deciduous forests, and then expansive C4 grasslands. This trajectory coincided with a seasonally uneven drying trend due to both increased evaporation of plant leaf and soil waters and reduced rainfall, as identified in soil carbonate and tooth enamel data sets. Collectively the fossil, biomarker, and isotopic evidence reveal the development of modern C4 ecosystems on the Indian Subcontinent followed a series of ecosystem transformations driven by drying and fire feedbacks, and possibly declining atmospheric pCO2, beginning at 10.2 Ma and strengthening through the late Miocene.

Black Sea paleosalinity evolution since the last deglaciation reconstructed from alkenone-inferred Isochrysidales diversity

The Black Sea underwent dramatic changes in salinity from the last glacial maximum to Holocene as it evolved from a large inland lake to become a part of the global ocean due to post-glacial sea level rise. However, the detailed history of the re-connection of the Black Sea to the Mediterranean and the resulting Black Sea salinity variations have been heavily debated. We take advantage of our recent study on alkenones from phylogenetically classified haptophyte groups and their association with variable salinity levels in modern environments to reconstruct detailed salinity changes in the Black Sea over the past 16,000 years. We report the first discovery and documentation of alkenones from Group I Isochrysidales in relation to past salinity changes in the Unit III sediment. Our data indicate that the Black Sea surface salinity gradually increased from near fresh at ∼16 ka (∼1-2 psu) to oligohaline (∼ 5-6 psu) at ∼ 9.4 ka, the time of initial marine inflow, suggesting a negative regional hydrological balance. Although the IMI (initial marine inflow) occurred at 9.4 ka, the relatively low surface water salinity levels persisted to the beginning of sapropel formation at 7.6 ka, suggesting a strongly positive regional hydrological balance. Alkenone profiles also indicate a period of significantly reduced salinity between 3.5 and 1.6 ka, differing from the previous proposed peak salinity at 2.7 ka based on alkenone hydrogen isotope values. We demonstrate that the mismatch originates from the predominance of previously unidentified Group II Isochrysidales over E. huxleyi during this time interval, and when species-specific hydrogen isotopic fractionation of alkenones is taken into consideration, the isotope-inferred salinity between 3.5 and 1.6 ka is consistent with our proposal. Our new assessment of the Black Sea salinity evolution since the last glacial shows broad agreement with other regional records and provides a new basis for evaluating the impact of regional hydrological changes on Neolithic human migrations to Europe.

Stable isotope geochemistry of the modern Shinfa River, northwestern Ethiopian lowlands: a potential model for interpreting ancient environments of the Middle Stone Age

Abstract Several years of weekly sampling of waters from the Shinfa River watershed in the lowlands of northwestern Ethiopia yielded 275 samples with δ D vsmow and δ 18 O vsmow values ranging from c. −10 to +100‰ and from c. −2 to +20‰, respectively. Wet season (summertime) Shinfa River water stable hydrogen and oxygen isotope values are among the lowest reported in this study, whereas the dry season (winter/spring) usually records a progressive trend towards +100 and +20‰, respectively. Overlapping with this interval of Shinfa River water sampling, air temperatures ( n = 155) also were recorded at the same time; temperatures range from c. 18 to 47°C. The coolest temperatures occur during the summer wet season, associated with the arrival of the Kiremt rains in the region, whereas the warmest temperatures occur towards the end of the dry season. In order to evaluate the extent to which this rather extreme isotope hydrology is recorded in the sediments and biota of the Shinfa River system, both hardwater calcareous deposits precipitated on basalt cobbles by evaporation in the Shinfa River channel during the dry season and aragonite from three different modern bivalve mollusc species were collected and analysed for their stable oxygen and carbon isotope compositions. Hardwater calcareous deposit δ 18 O vpdb and δ 13 C vpdb values range from c. −2 to +5‰ and c. −9 to +7‰, respectively, and preserve a trend towards progressively more positive δ 18 O vpdb and δ 13 C vpdb values through the course of the dry season. Shinfa River mollusc aragonite powders ( n = 51) were serially sampled from cf. Coelutura aegyptica , cf. Chambardia rubens and Etheria elliptica species. All species record oxygen and carbon isotopes between c. −2 and +7‰ and between c. −18 and −8‰, and each species records coherent trends between those extremes as well as a positive parametric correlation between measured oxygen and carbon isotope values. However, there does appear to be some variability of measured isotope values by species, suggesting that species-specific metabolic differences may impact the resulting range of aragonite stable carbon and oxygen values. Based upon the measured Shinfa River water δ 18 O vsmow and corresponding water temperatures at the time of sampling, a possible range of Shinfa River calcite and aragonite δ 18 O vpdb values were calculated in conjunction with well-established calcite–water and aragonite–water oxygen isotope fractionation equations. These ‘fictive’ calcite and aragonite δ 18 O vpdb values range from c. −5 to +15‰, which is a much larger range than previously documented from analyses of the hardwater calcareous deposits and mollusc aragonite samples. The narrower range of values in the natural calcite and aragonite samples may be attributed to several mechanisms, including time averaging and environmental stress. Nevertheless, the stable oxygen isotopic compositions of these natural samples offer a minimum assessment of the environmental extremes which occur in this region today, and provide a model for reconstructing the environments of the past.

Hydrogeochemistry and hydrogen and oxygen stable isotope characteristics of water in Huainan subsidence areas

以安徽淮南采煤沉陷积水为研究对象，通过样品采集与测试，研究不同沉陷年限及类型积水水文地球化学和氢氧稳定同位素组成特征及影响因素.结果表明：（1）研究区水化学类型主要为Cl-Na、HCO₃·Cl-Na型，沉陷积水中常量离子主要来源于蒸发岩溶解和硅酸盐风化，受蒸发作用和人为活动的影响明显，水化学组成随沉陷时间和类型变化不大.（2）淮南大气降水线方程为：δD=8.85δ¹⁸O+18.73，沉陷区积水氢氧稳定同位素值在淮南大气降水线右下方依次分布并接近降水线，表明沉陷积水主要来源于大气降水.（3）在降水稀释、水体蒸发及地下水补给的作用下，随着沉陷年限的增加，积水中重同位素越来越贫化，同一年限不同类型的积水同位素值变化较小.;Taking the coal mining subsidence water in Huainan, Anhui Province as the research object, through sample collection and testing, the hydrogeochemistry, hydrogen and oxygen stable isotopic composition characteristics and influencing factors of different subsidence years and types of water are studied. The results show that:(1) The main types of water chemistry in the study area are Cl-Na and HCO₃·Cl-Na. The major ions in the sedimentation water mainly come from evaporite dissolution and silicate weathering, and are affected by evaporation and human activities. Obviously, the chemical composition of water does not change much with the time and type of subsidence. (2) The Huainan atmospheric precipitation line equation is:δD=8.85δ¹⁸O+18.73. The hydrogen and oxygen stable isotopic values of the accumulated water in the subsidence area are distributed in sequence at the lower right of the Huainan atmospheric precipitation line and are close to the precipitation line, indicating that the subsided water mainly comes from atmospheric precipitation. (3) Under the effects of precipitation dilution, water evaporation, and groundwater replenishment, with the increase of the subsidence period, the heavy isotopes of the accumulated water become more and more depleted. The isotopic values of different types of accumulated water of the same age have little change, which is affected by the isotopes.

Fossil leaf wax hydrogen isotopes reveal variability of Atlantic and Mediterranean climate forcing on the southeast Iberian Peninsula between 6000 to 3000 cal. BP.

Many recently published papers have investigated the spatial and temporal manifestation of the 4.2 ka BP climate event at regional and global scales. However, questions with regard to the potential drivers of the associated climate change remain open. Here, we investigate the interaction between Atlantic and Mediterranean climate forcing on the south-eastern Iberian Peninsula during the mid- to late Holocene using compound-specific hydrogen isotopes from fossil leaf waxes preserved in marine sediments. Variability of hydrogen isotope values in the study area is primarily related to changes in the precipitation source and indicates three phases of increased Mediterranean sourced precipitation from 5450 to 5350 cal. BP, from 5150 to 4300 cal. BP including a short-term interruption around 4800 cal. BP, and from 3400 to 3000 cal. BP interrupted around 3200 cal. BP. These phases are in good agreement with times of prevailing positive modes of the North Atlantic Oscillation (NAO) and reduced storm activity in the Western Mediterranean suggesting that the NAO was the dominant modulator of relative variability in precipitation sources. However, as previously suggested other modes such as the Western Mediterranean Oscillation (WeMO) may have altered this overall relationship. In this regard, a decrease in Mediterranean moisture source coincident with a rapid reduction in warm season precipitation during the 4.2 ka BP event at the south-eastern Iberian Peninsula might have been related to negative WeMO conditions.

Larch Cellulose Shows Significantly Depleted Hydrogen Isotope Values With Respect to Evergreen Conifers in Contrast to Oxygen and Carbon Isotopes

The analysis of the stable isotope of the tree-ring cellulose is an important tool for paleo climatic investigations. Long tree-ring chronologies consist predominantly of oaks and conifers in Europe, including larch trees (Larix decidua) and cembran pines (Pinus cembra) that form very long tree ring chronologies in the Alps and grow at the treeline, where tree growth is mainly determined by temperature variations. We analyzed δ13C, δ18O and δ2H isotopes in the cellulose extracted from tree-rings of wood samples collected at high altitude in the Swiss and Tyrol Alps, covering the whole Holocene period. We found that larch cellulose was remarkably more depleted in deuterium than that of cembran pine, with mean δ2H values of −113.4 ± 9.7‰ for larch and of −65.4 ± 11.3‰ for cembran pine. To verify if these depleted values were specific to larch or a property of the deciduous conifers, we extended the analysis to samples from various living conifer species collected at the Bern Botanical Garden. The results showed that not only the larch, but also all the samples of the deciduous larch family had a cellulose composition that was highly depleted in δ2H with regard to the other evergreen conifers including cembran pine, a difference that we attribute to a faster metabolism of the deciduous conifers. The δ18O values were not statistically different among the species, in agreement with the hypothesis that they are primary signals of the source water. While the δ13C values were slightly more depleted for larch than for cembran pine, likely due to metabolic differences of the two species. We conclude that the deciduous larch conifers have specific metabolic hydrogen fractionations and that the larch unique signature of δ2H is useful to recognize it from other conifers in subfossil wood samples collected for paleoclimatic studies. For climate information the absolute δ2H values of larch should be considered carefully and separate from other species.

Using oxygen and hydrogen stable isotopes to track the migratory movement of Sharp-shinned Hawks (Accipiter striatus) along Western Flyways of North America.

The large-scale patterns of movement for the Sharp-shinned Hawk (Accipiter striatus), a small forest hawk found throughout western North America, are largely unknown. However, based on field observations we set out to test the hypothesis that juvenile migratory A. striatus caught along two distinct migration routes on opposite sides of the Sierra Nevada Mountains of North America (Pacific Coast and Intermountain Migratory Flyways) come from geographically different natal populations. We applied stable isotope analysis of hydrogen (H) and oxygen (O) of feathers, and large scale models of spatial isotopic variation (isoscapes) to formulate spatially explicit predictions of the origin of the migrant birds. Novel relationships were assessed between the measured hydrogen and oxygen isotope values of feathers from A. striatus museum specimens of known origin and the isoscape modeled hydrogen and oxygen isotope values of precipitation at those known locations. We used these relationships to predict the origin regions for birds migrating along the two flyways from the measured isotope values of migrant’s feathers and the associated hydrogen and oxygen isotopic composition of precipitation where these feathers were formed. The birds from the two migration routes had overlap in their natal/breeding origins and did not differentiate into fully separate migratory populations, with birds from the Pacific Coast Migratory Flyway showing broader natal geographic origins than those from the Intermountain Flyway. The methodology based on oxygen isotopes had, in general, less predictive power than the one based on hydrogen. There was broad agreement between the two isotope approaches in the geographic assignment of the origins of birds migrating along the Pacific Coast Flyway, but not for those migrating along the Intermountain Migratory Flyway. These results are discussed in terms of their implications for conservation efforts of A. striatus in western North America, and the use of combined hydrogen and oxygen stable isotope analysis to track the movement of birds of prey on continental scales.

Regeneration of unconventional natural gas by methanogens co-existing with sulfate-reducing prokaryotes in deep shale wells in China

Biogenic methane in shallow shale reservoirs has been proven to contribute to economic recovery of unconventional natural gas. However, whether the microbes inhabiting the deeper shale reservoirs at an average depth of 4.1 km and even co-occurring with sulfate-reducing prokaryote (SRP) have the potential to produce biomethane is still unclear. Stable isotopic technique with culture-dependent and independent approaches were employed to investigate the microbial and functional diversity related to methanogenic pathways and explore the relationship between SRP and methanogens in the shales in the Sichuan Basin, China. Although stable isotopic ratios of the gas implied a thermogenic origin for methane, the decreased trend of stable carbon and hydrogen isotope value provided clues for increasing microbial activities along with sustained gas production in these wells. These deep shale-gas wells harbored high abundance of methanogens (17.2%) with ability of utilizing various substrates for methanogenesis, which co-existed with SRP (6.7%). All genes required for performing methylotrophic, hydrogenotrophic and acetoclastic methanogenesis were present. Methane production experiments of produced water, with and without additional available substrates for methanogens, further confirmed biomethane production via all three methanogenic pathways. Statistical analysis and incubation tests revealed the partnership between SRP and methanogens under in situ sulfate concentration (~ 9 mg/L). These results suggest that biomethane could be produced with more flexible stimulation strategies for unconventional natural gas recovery even at the higher depths and at the presence of SRP.

Phenological and isotopic evidence for migration as a life history strategy in Aeshna canadensis (family: Aeshnidae) dragonflies

1. Investigating dragonfly migration is important for understanding species' life history strategies, migratory connectivity, terrestrial‐aquatic linkages, and for successful species conservation. While migration patterns are well‐documented for some species (e.g., Anax junius), questions remain about potential migratory behaviour of others.2. We investigated the potential for migration of Aeshna canadensis (Walker, 1908; Canada darner) using phenological observations in three study ponds in central Minnesota, 2017–2019. We also conducted probabilistic assignment to natal origins by measuring stable hydrogen isotope values of wing tissue (δ2Hw) of dragonflies collected in Minnesota and acquired through Canadian museum collections.3. This species emerged May–June from study ponds in central Minnesota, with a 10–15 week lag after onset of emergence before mature adults were observed flying and ovipositing in late summer. The probabilistic assignment depictions of emerging tenerals overlapped with the sampling location, confirming accuracy of isotopic assignments of natal origin.4. Late‐flying mature adults collected at our study ponds likely originated from southern Manitoba, suggesting a north–south migration pathway. We found further evidence for migration by analysing δ2Hw of adult dragonflies collected in northern Minnesota and south‐central Canada. Their likely origins were farther north in central Canada (Manitoba/Quebec) or the northeastern reaches of this species' range in eastern Canada.5. We provide the first conclusive evidence of Aeshna migration in North America and demonstrate a robust approach, combining field observations with probabilistic assignment to origin using stable isotope analysis, which can test for migration in other dragonfly populations.

Implications for groundwater recharge from stable isotopic composition of precipitation in Hawai'i during the 2017–2018 La Niña

AbstractThe project captured a subset of the hydrological cycle for the tropical island of O'ahu, linking precipitation to groundwater recharge and aquifer storage. We determined seasonal storm events contributed more to aquifer recharge than year‐round baseline orographic trade wind rainfall. Hydrogen and oxygen isotope values from an island‐wide rain collector network with 20 locations deployed for 16 months and sampled at 3‐month intervals were used to create the first local meteoric water line for O'ahu. Isotopic measurements were influenced by the amount effect, seasonality, storm type, and La Niña, though little elevation control was noted. Certain groundwater compositions from legacy data showed a strong similarity with collected precipitation from our stations. The majority of these significant relationships were between wet season precipitation and groundwater. A high number of moderate and heavy rainfall days during the dry season, large percentage of event‐based rainfall, and wind directions outside of the typical NE trade wind direction were characteristics of the 2017–2018 wet season. This indicates that the majority of wet season precipitation is from event‐based storms rather than typical trade wind weather. The deuterium‐excess values provided the strongest evidence of a relationship between groundwater and different precipitation sources, indicating that this may be a useful metric for determining the extent of recharge from different rain events and systems.

Carbon and hydrogen isotopic variations in gold tube gas pyrolysates from an Athabasca oil sand

Closed system gold tube pyrolysis experiments were conducted on an oil sand bitumen from the Athabasca region in western Canada to investigate gas isotope variation with heating temperatures. Experiments were carried out at 350–650 °C and a pressure of 50 MPa, with heating rates of 2 °C/h and 20 °C/h. The progressive cracking of bitumen and liquid oil lead to continuous release of methane with increasing pyrolysis temperatures, while the yields of wet gas components increase initially at the lower temperature range and then decrease drastically at high temperatures. A general trend of 13C- and 2H-enrichment in the gas products is seen with increasing pyrolysis temperatures due to thermal cracking of various hydrocarbon and non-hydrocarbon components. Isotopic variations can be quite extensive, commonly occurring for both hydrocarbon gases and CO2 as pyrolysis progresses. A carbon isotopic rollover (isotope of gas component shifting from 13C enrichment to 12C-enrichment with increasing temperature) occurs for bulk hydrocarbon gas components at low temperature (< 450 °C), while rollover only occurs for ethane and propane at high temperature (> 550 °C), where partial reversal (lower carbon numbered gas component becomes more 13C-enriched relative to higher carbon numbered ones) also exists. The isotopic values of CO2 show a wide range of variation with the highest δ13C value seen at the lowest temperature while the lowest δ13C value occurs at 500 °C and 550 °C for 2 °C/h and 20 °C/h, respectively. Relative 13C-enrichment occurs only in the high temperature range. The unusual carbon isotope ratios of CO2 in pyrolysates is likely related to biodegradation influence on the precursors, but further investigation is still called for. Hydrogen isotopic values of hydrocarbon gases show even more dramatic variation than that seen for carbon. While methane is progressively 2H-enriched to 650 °C, ethane and propane are relatively 2H-enriched when the pyrolysis temperature is < 500 °C, while the trend is inverted at higher temperatures. Data presented here clearly deviate from the trajectories expected by simple equilibrium or Rayleigh-type kinetic cracking models. Dynamic generation, destruction and mixing processes govern the final isotopic signature in an associated gas product. Isotopic rollover and reversal seem to be a common phenomenon during thermal evolution where heterogeneous precursors are available. While the reaction system of pyrolysis at high temperature differs completely from source rock evolution at low temperature and some artifacts are inevitably involved, the isotope behavior observed here may provide some insights into the complexity in natural cases and help our understanding of the mechanisms of isotopic evolution during thermal maturation.

Growing up in Ancient Sardinia: Infant-toddler dietary changes revealed by the novel use of hydrogen isotopes (δ2H).

Detailed information about the lives and deaths of children in antiquity is often in short supply. Childhood dietary histories are, however, recorded and maintained in the teeth of both juveniles and adults. Primary tooth dentinal collagen does not turn over, preserving a sequential record of dietary changes. The use of nitrogen (δ15N) and carbon (δ13C) isotope values of incrementally sampled dentin are used in the study of breastfeeding practices but evidence for the addition of weaning foods, both in terms of mode and, particularly, duration, has remained analytically inaccessible to date. Here, we demonstrate how the novel use hydrogen isotope (δ2H) values of sequentially micro-sampled dentin collagen, measured from individuals excavated from a Punic cemetery, in Sardinia, Italy, can serve as a proxy for weaning food type and duration in ancient childhood diet. The weaning rate and age, based on the decline in δ15N and δ13C values of permanent first molars and the concomitant increase in δ2H, appears to be broadly similar among six individuals. Hydrogen isotopes vary systematically from a low value soon after birth, rising through early childhood. The early post-birth values can be explained by the influence of 2H-depleted lipids from mother’s breastmilk and the later δ2H rise is consistent with, among other things, a substantial portion of boiled foodstuffs, such as the higher δ2H values observed in porridge. Overall δ2H in dentin shows great promise to elucidate infant and childhood feeding practices, and especially the introduction of supplementary foods during the weaning process.

Geochemical characteristics and genesis of the Middle Devonian and the Middle Permian natural gas in the Sichuan Basin, China

Breakthroughs have been made for the natural gas exploration of the Middle Devonian and the Middle Permian formations in the Sichuan Basin in recent years. Nevertheless, its natural gas source is still not clear, which then affects the next exploration deployment decision. A comprehensive study is conducted on the geochemical characteristics of the Middle Devonian and the Middle Permian natural gas, the biomarkers of reservoir bitumen, and the source rocks. The results show that these natural gases are secondary cracking dry gas that includes more than 86% of methane content, a small amount of ethane, propane, and a non-hydrocarbon gas (e.g., nitrogen, carbon dioxide, and hydrogen sulfide). The natural gas maturity varies slightly in different regions. The carbon and hydrogen isotope values of natural gas are as follows: δ13C1 ranges from −35.7‰ to −27.3‰, δ13C2 ranges from −38.7‰ to −26.6‰, δ13C3 ranges from −37‰ to −26.5‰, δ2HCH4 ranges from −141‰ to −138‰, and δ2HC2H6 ranges from −164‰ to −112‰. The isotope values indicate that the genetic type of natural gas is the sapropelic type and the mixture type is dominated by sapropelic type. The difference between natural gas values of δ13C1, δ13C2, and δ2HCH4 in different regions is related to the contribution ratio of source rocks from different ages. The gases of the Middle Devonian and the Middle Permian of the Shuangyushi structure in Northwestern Sichuan, the Middle Permian of Southwestern Sichuan, and the Middle Permian of Paleo-uplift in Central Sichuan are mainly derived from the Cambrian Qiongzhusi Formation and the Middle-Lower Permian source rocks. The Middle-Upper Permian natural gases of the volcanic reservoir in Southwestern Sichuan is mainly from the Qiongzhusi source rock. The Middle Permian natural gases of the Hewanchang structure in Northwestern Sichuan, Eastern Sichuan, and Southern Sichuan are mainly derived from the Silurian Longmaxi source rock. The research results have important guiding significance for developing exploration and deployment solutions for natural gas of the Middle Devonian and the Middle Permian formation in the Sichuan Basin.

Advancing interpretation of stable isotope assignment maps: comparing and summarizing origins of known-provenance migratory bats

AbstractProbability-of-origin maps deduced from stable isotope data are important for inferring broad-scale patterns of animal migration, but few resources and tools for interpreting and validating these maps exist. For example, quantitative tools for comparing multiple probability-of-origin maps do not exist, and many existing approaches for geographic assignment of individuals have not been validated or compared with respect to precision and accuracy. To address these challenges, we created and analyzed probability-of-origin maps using stable hydrogen isotope values from known-origin individuals of three species of migratory bat. We used a metric of spatial overlap to group individuals by areas of origin without a priori knowledge of such regions. The metric of spatial similarity allowed for quantitative comparison of geographic origins and grouping of individuals with similar origins. We then compared four approaches for inferring origins (cumulative-sum, odds-ratio, quantile-only, and quantile-simulation) across a range of thresholds and probable minimum distance traveled. The accuracy of geographic origins and minimum distance traveled varied across species at most threshold values for most approaches. The cumulative-sum and quantile-simulation approaches had generally higher precision at a given level of accuracy than the odds-ratio and quantile-only approaches, and many threshold values were associated with a relatively high degree (&gt; 300 km) of variation in minimum distance traveled. Overall, these results reinforce the importance of validating assignment techniques with known-origin individuals when possible. We present the tools discussed as part of an R package, ‘isocat’ (“Isotope Origin Clustering and Assignment Tools”).

Thermal Fluid Changes after Operating a Geothermal System: A Case Study of the Chingshui Geothermal Field, Taiwan

The operation of Taiwan’s first geothermal power plant from 1981 to 1993 affected the chemistry of hot fluids in the Chingshui geothermal field. Long-term chemical and isotope data from the production wells have been analyzed since 1973, and the rising steam ratio and enthalpy indicate that shortages of recharging fluids lead to a serious boiling and scaling of carbonates within the first few years of production. Furthermore, the progressively depleted hydrogen and oxygen isotope ratios and the high chloride concentrations in the southern part of the reservoir after discharge indicate that the hot fluids may have been derived from high altitudes and circulated through a deep layer during the discharge period. Decreasing chloride concentrations, lowered silica temperatures, and enriched hydrogen isotope values in the northern part of the reservoir indicate that there is a shallower meteoric fluid circulation from another fractured system that has seeped into and discharged the reservoir when the pressure of the main conduit dropped. After a long non-discharging period, the isotope values are enriched, the concentration of chloride is halved, and silica temperatures are lower than initially state. These observations indicate that the reservoir after the pressure drop was recharged by a shallower meteoric fluid, but the residence time is too short for heating to the initial condition.

Stable Isotope Analysis Supports First Occurrence of a Wild-Origin Greylag Goose (Anser anser) to Make Landfall in North America

In North America, the Greylag Goose (Anser anser) has been added to the list of vagrant North American waterfowl based on a bird observed in 2005 on a stationary oil ship in the Atlantic Ocean 167 km southeast of the island of Newfoundland, and on single birds observed in Connecticut and Nova Scotia in 2009 and 2010, respectively. Here, feather and toe-claw hydrogen isotope values (δ2H) linked to spatial hydrological hydrogen isotope patterns are used to demonstrate the origin of the first probable wild-origin Greylag Goose known to make landfall in North America. The bird in question, shot by hunters on Grand Manan Island, New Brunswick, in December 2007 and subsequently deposited at the New Brunswick Museum (specimen NBM 11143), was identified as Anser anser and potentially a wild-origin bird. Isotope data indicates the bird is of probable Greenlandic origin. This supports and pre-dates recent (2014) reports of the Greenlandic molting of Icelandic Greylag Geese, until recently believed to molt exclusively on Iceland. Greylag Geese recorded in North America appear to be part of a pattern of increasing numbers and diversity of geese of northeastern Atlantic origin detected in eastern North America in recent decades.

Genesis of the graphite orbicules in the Huangyangshan graphite deposit, Xinjiang, China: Evidence from geochemical, isotopic and fluid inclusion data

The Huangyangshan graphite deposit in the East Junggar Orogen (China) contains intriguing graphite orbicules. This contribution is designed to present reasonably comprehensive assessment of their origin. In this deposit, the intrusive orebodies are mechanically juxtaposed against contacts with granitic wall rocks. The orbicules are typically concentrically zoned in texture with a notable binary configuration involving a central core and an outer shell. The orbicule cores possess mineralogical and compositional variations that are more or less similar to those of the granitic wall rocks. The orbicule shells are composed of various ferromagnesian minerals (clinopyroxene + hornblende) in stark contrast to the matrix, where hornblende, sanidine and albite have higher Mg#, Ab and An values, respectively. The replacement of silicates by graphite and sulfides (pyrrhotite + chalcopyrite + pyrite) is common. The graphite throughout the matrix and orbicules features a patchy distribution of major elements (C) and dispersed elements (Cr, Ni, Co, S, Cu, Zn, As, Pb, etc.). The carbon isotopic compositions of the orbicular ore are −20.9 to −20.5‰, analogous to those of the surrounding strata, i.e., −25.6 to −19.3‰. The sulfur isotopic compositions of sulfides in the orbicular ore are −4.8 to −2.6‰, which differ from those of the surrounding strata, i.e., 16.0–23.0‰. Fluid inclusions principally comprise the volatile component CH4 and solid daughter minerals (graphite + chalcopyrite) with Tm > 450 °C. Vapor-liquid two-phase fluid inclusions formed under conditions of Th = 143.6–367.5 °C, P = 3–194 bar, and fO2 = −52.76 to −31.15. The hydrogen and oxygen isotopic values of the orbicular ore are δD = −110.3 to −107.0‰ and δ18Owater = 10.1–11.7‰. Zircons from the orbicular ore have 206Pb/238U ages of 304–359 Ma, with a weighted average of 319.0 ± 6.4 Ma, overlapping the geochronological age of the granitic host rocks (305.1–321.4 Ma). The orbicular ore has SiO2 concentrations ranging from 53.30 to 72.61 wt%, falling within the compositional fields of granite, quartz monzonite, granodiorite, diorite, and monzodiorite in the TAS classification diagram. The Sr-Nd and Hf isotopic data from the orbicular ore indicate mixing between materials derived from the depleted mantle and materials derived from the crust, with a dominant mantle contribution. The petrographic, geochemical, isotopic and fluid inclusion characteristics indicate that the processes of incorporation of H2O and wall rock fragments, liquid immiscibility and exsolution of a late magmatic fluid were responsible for orbicule formation in the Huangyangshan deposit. The following genetic model is proposed: (1) In the late Carboniferous, a new orbicular magma containing organic matter-derived CH4 and deep-mantle SO2 emplaced within the Huangyangshan pluton. Contemporaneously, crystal fragments and H2O were incorporated into the orbicular magma from the granitic host rocks. (2) H2O saturation was reached in the orbicular magma and fostered segregation of a hydrous ferromagnesian melt (orbicules) with a silicic residual melt (matrix). (3) At approximately 630 °C, 2000 bar and −18 lgfO2, graphite and sulfides formed en masse through deuteric alteration: 3CH4 + 2SO2 + 2(Fe2+)7[Si4O11]2(OH)2 (hornblende) = 3C (graphite) + 2FeS (pyrrhotite) + 8SiO2 (quartz) + 2(Fe3Si4O10(OH)2 + Fe3(OH)6) (chlorite), following the expulsion of a late magmatic fluid from the ferromagnesian melt.