Isotopic evidence of TSR origin for natural gas bearing high H_2S contents within the Feixianguan Formation of the northeastern Sichuan Basin, southwestern China

Isotopic evidence of TSR origin for natural gas bearing high H2S contents 1961 As the hazardous component of natural gas, the ex-istence of H2S, due to its extremely strong toxicity and corrosivity, not only decreases the percentage of hy-drocarbon gas within natural gas and reduces its in-dustrial value, it also threatens each aspect of drilling and exploitation. It frequently causes serious safety accidents[1] and leads to the E&P cost and risk of natural gas with higher H2S contents be…     

Formation of Paleoproterozoic eclogitic mantle, Slave Province (Canada): Insights from in-situ Hf and U–Pb isotopic analyses of mantle zircons

In-situ Hf isotope analyses and U–Pb dates were obtained by laser ablation-MC-ICP-MS for a zircon-bearing mantle eclogite xenolith from the diamondiferous Jericho kimberlite located within the Archean Slave Province (Nunavut), Canada. The U–Pb zircon results yield a wide range of ages (2.0 to 0.8 Ga) indicating a complex geological history. Of importance, one zircon yields a U–Pb upper intercept date of 1989 ± 67 Ma, providing a new minimum age constraint for zircon crystallization and eclogite formation. In contrast, Hf isotope systematics for the same zircons display an intriguing uniformity, and corresponding Hf depleted mantle model ages range between 2.1 ± 0.1 and 2.3 ± 0.1 Ga; the youngest Hf model age is within error to the oldest U–Pb date.

The Jericho eclogites have previously been interpreted as representing remnants of metamorphosed oceanic crust, and their formation related to Paleoproterozoic subduction regimes along the western margin of the Archean Slave craton during the Wopmay orogeny. Hf isotope compositions and U–Pb results for the Jericho zircons reported here are in good agreement with a Paleoproterozoic subduction model, suggesting that generation of oceanic crust and eclogite formation occurred between 2.0 and 2.1 Ga. The slightly older Hf depleted mantle model ages (2.1 to 2.3 Ga) may be reconciled with this model by invoking mixing between ‘crustal’-derived Hf from sediments and more radiogenic Hf associated with the oceanic crust during the 2 Ga subduction event. This results in intermediate Hf isotope compositions for the Jericho zircons that yield ‘fictitiously’ older Hf model ages.     

The influence of particle composition on thorium scavenging in the NE Atlantic ocean (POMME experiment)

²³⁰Th, ²³²Th and ²³⁴Th were analyzed in sinking particles collected by moored and drifting sediment traps in the NE Atlantic Ocean (POMME experiment) in order to constrain the phase(s) carrying Th isotopes in the water column. It reveals a contrasted behaviour between ²³⁴Th and ²³⁰Th. ²³⁴Th is correlated to the particulate organic carbon suggesting that it is primarily scavenged by organic compounds in the surface waters. ²³⁰Th_xs is correlated with Mn, Ba and the lithogenic fraction that are enriched in small suspended particles and incorporated in the sinking particulate flux throughout the water column. The lack of correlation between ²³⁰Th_xs and CaCO₃ or biogenic silica (bSi) indicates that CaCO₃ and bSi are not responsible for ²³⁰Th scavenging in the deep waters of this oceanic region. ²³⁰Th is generally correlated with the lithogenic content of the trapped material but this correlation disappears in winter during strong atmospheric dust inputs suggesting that lithogenic matter is not directly responsible for ²³⁰Th scavenging in the deep waters or that sufficient time is required to achieve particle–solution equilibration. MnO₂ could be the prevalent ²³⁰Th_xs-bearing phase. The narrow range of K_{d_MnO2}^Th obtained for very contrasted oceanic environments supports a global control of ²³⁰Th_xs scavenging by MnO₂ and raises the possibility that the ²³⁰Th–²³¹Pa fractionation is controlled by the amount of colloidal MnO₂ in seawater.     

1950年以来青藏高原兹格塘错碳酸盐稳定碳同位素变化及其原因

兹格塘错是青藏高原中部一个典型的半混合型咸水湖泊。本文在~(210)Pb和~(137)Cs定年的基础上,研究了兹格塘错重力岩芯(ZGTC A-1)小于38.5μm细颗粒组分碳酸盐稳定碳同位素1950年以来的变化及其影响因素。对冬夏季湖水水化学特征的分析表明,夏季湖水溶解CO_2呈逸出状态,冬季湖水钙离子浓度是夏季湖水的10倍,据此可以得出兹格塘错碳酸盐矿物主要在夏季沉淀。通过与那曲气象站气象记录对比发现,1950年以来A-1岩芯碳酸盐碳同位素变化与年均温度有很好的相关性,表现出年均温度高时碳同位素偏重,而年均温度低时碳同位素偏轻的特征。兹格塘错1950年以来自生碳酸盐碳同位素的变化是由湖区及水体碳循环(如碳酸盐沉淀,有机质的沉淀与分解,有机碳和无机碳的转化等)的变化引起的,但各种因素的相互作用非常复杂。碳酸盐含量也与温度有关,温度越高,碳酸盐含量越高,同时降水量与碳酸盐含量也存在明显的相关关系。1950年以来有机质含量与温度呈反相关,可能与湖泊生产力的下降有关。     

Hydrothermal alteration and tectonic evolution of an intermediate- to fast-spreading back-arc oceanic crust: Late Ordovician Solund-Stavfjord ophiolite, western Norway

Abstract The Solund‐Stavfjord ophiolite complex (SSOC) in western Norway represents a remnant of the Late Ordovician oceanic lithosphere, which developed in an intermediate‐ to fast‐spreading Caledonian back‐arc basin. The internal architecture and magmatic features of its crustal component suggest that the SSOC has a complex, multistage sea floor spreading history in a supra‐subduction zone environment. The youngest crustal section associated with the propagating rift tectonics consists of a relatively complete ophiolite pseudostratigraphy, including basaltic volcanic rocks, a transition zone between the sheeted dyke complex and the extrusive sequence, sheeted dykes, and high‐level isotropic gabbros. Large‐scale variations in major and trace element distributions indicate significant remobilization far beyond that which would result from magmatic processes, as a result of the hydrothermal alteration of crustal rocks. Whereas K₂O is strongly enriched in volcanic rocks of the extrusive sequence, Cu and Zn show the largest enrichment in the dyke complex near the dyke–volcanic transition zone or within this transition zone. The δ¹⁸O values of the whole‐rock samples show a general depletion structurally downwards in the ophiolite, with the largest and smallest variations observed in volcanic rocks and the transition zone, respectively. δ¹⁸O values of epidote–quartz mineral pairs indicate 260–290°C for volcanic rocks, 420°C for the transition zone, 280–345°C for the sheeted dyke complex and 290–475°C for the gabbros. The ⁸⁷Sr/⁸⁶Sr isotope ratios show the widest range and highest values in the extrusive rocks (0.70316–0.70495), and generally the lowest values and the narrowest range in the sheeted dyke complex (0.70338–0.70377). The minimum water/rock ratios calculated show the largest variations in volcanic rocks and gabbros (approximately 0–14), and generally the lowest values and range in the sheeted dyke complex (approximately 1–3). The δD values of epidote (?1 to ?12‰), together with the δ¹⁸O calculated for Ordovician seawater, are similar to those of present‐day seawater. Volcanic rocks experienced both cold and warm water circulation, resulting in the observed K₂O‐enrichment and the largest scatter in the δ¹⁸O values. As a result of metal leaching in the hot reaction zone above a magma chamber, Zn is strongly depleted in the gabbros but enriched in the sheeted dyke complex because of precipitation from upwelling of discharged hydrothermal fluids. The present study demonstrates that the near intact effect of ocean floor hydrothermal activity is preserved in the upper part of the SSOC crust, despite the influence of regional lower greenschist facies metamorphism.     

Refining the pre-industrial atmospheric Pb isotope evolution curve in Europe using an 8000 year old peat core from NW Spain

Pb pollution has existed for several millennia and remains relevant today. By using peat cores as environmental archives it is possible to reconstruct this long history on a regional scale. This is a significant contribution to the findings from ice core records, the only other archive recording purely atmospheric additions. Without information that allows linking and comparison between sites regionally, within Europe and elsewhere, our ability to make coherent global models of the natural Pb cycle, and anthropogenic forcing of this cycle, is limited. In this respect, the characteristics of the Pb pre-pollution aerosol (PPA) are important to define globally. We characterize for the first time a PPA in Southern Europe with [Pb] = 0.78 ± 0.86 μg g^− 1, net Pb accumulation rates of 0.032 ± 0.030 mg m^− 2 y^− 1 and a ²⁰⁶Pb / ²⁰⁷Pb signature of 1.25470 ± 0.02575. This PPA Pb isotope signature is more radiogenic than that found thus far in Western and Northern Europe. Spain is a historically important mining site. Using three-isotope plots and a pool of potential Pb isotope signatures, a detailed source appointment of both natural and anthropogenic Pb sources was made. We found evidence of Saharan aridification and its termination ∼4400 BP and/or agricultural signals and strong local control (from rock and soil) of the Pb PPA. Human impact is first recorded at 3210 BP but does not exceed 50% of deposited Pb until 3005 BP. Mines in SE Spain dominate early Pb pollution history at this site. During the rise of Roman rule, contributions come from mines in N, NW and SW Spain with no strong indication of other European mining activities. In Medieval and Industrial times local contributions to the peat bog are reduced.     

Organic carbon and nitrogen stable isotopes in the intertidal sediments from the Yangtze Estuary, China

The natural isotopic compositions and C/N elemental ratios of sedimentary organic matter were determined in the intertidal flat of the Yangtze Estuary. The results showed that the ratios of carbon and nitrogen stable isotopes were respectively −29.8‰ to − 26.0‰ and 1.6‰–5.5‰ in the flood season (July), while they were −27.3‰ to − 25.6‰ and 1.7‰–7.8‰ in the dry season (February), respectively. The δ¹³C signatures were remarkably higher in July than in February, and gradually increased from the freshwater areas to the brackish areas. In contrast, there were relatively complex seasonal and spatial changes in stable nitrogen isotopes. It was also reflected that δ¹⁵N and C/N compositions had been obviously modified by organic matter diagenesis and biological processing, and could not be used to trace the sources of organic matter at the study area. In addition, it was considered that the mixing inputs of terrigenous and marine materials generally dominated sedimentary organic matter in the intertidal flat. The contribution of terrigenous inputs to sedimentary organic matter was roughly estimated according to the mixing balance model of stable carbon isotopes.     

黄壁庄水库降水效应的分析

南极洲万达盐湖为饱和方解石湖水。计算出的方解石饱和指数随水深增加而变化。在Ca~(2+)及HCO_3~-活度值均一的上部氧化环境湖水中,pH及溶解氧(DO)是控制该变化的主要因素,在下部还原环境湖水中,Ca~(2+)及HCO_3~-的活度对方解石的饱和指数SI的变化起主要作用。这充分揭示了湖底部近代沉积物中分布较多方解石矿物的原因。     

Storage-discharge characteristics of an active rock glacier catchment in the Innere Ölgrube,Austrian Alps

The active rock glacier “Innere Ölgrube” and its catchment area (Ötztal Alps, Austria) are assessed using various hydro(geo)logical tools to provide a thorough catchment characterization and to quantify temporal variations in recharge and discharge components. During the period from June 2014 to July 2018, an average contribution derived from snowmelt, ice melt and rainfall of 35.8%, 27.6% and 36.6%, respectively, is modelled for the catchment using a rainfall-runoff model. Discharge components of the rock glacier springs are distinguished using isotopic data as well as other natural and artificial tracer data, when considering the potential sources rainfall, snowmelt, ice melt and longer stored groundwater. Seasonal as well as diurnal variations in runoff are quantified and the importance of shallow groundwater within this rock glacier-influenced catchment is emphasized. Water derived from ice melt is suggested to be provided mainly by melting of two small cirque glaciers within the catchment and subordinately by melting of permafrost ice of the rock glacier. The active rock glacier is characterized by a layered internal structure with an unfrozen base layer responsible for groundwater storage and retarded runoff, a main permafrost body contributing little to the discharge (at the moment) by permafrost thaw and an active layer responsible for fast lateral flow on top of the permafrost body. Snowmelt contributes at least 1/3rd of the annual recharge. During droughts, meltwater derived from two cirque glaciers provides runoff with diurnal runoff variations; however, this discharge pattern will change as these cirque glaciers will ultimately disappear in the future. The storage-discharge characteristics of the investigated active rock glacier catchment are an example of a shallow groundwater aquifer in alpine catchments that ought to be considered when analysing (future) river runoff characteristics in alpine catchments as these provide retarded runoff during periods with little or no recharge.     

Subarctic catchment water storage and carbon cycling – Leading the way for future studies using integrated datasets at Pallas,Finland

Subarctic ecohydrological processes are changing rapidly, but detailed and integrated ecohydrological investigations are not as widespread as necessary. We introduce an integrated research catchment site (Pallas) for atmosphere, ecosystems, and ecohydrology studies in subarctic conditions in Finland that can be used for a new set of comparative catchment investigations. The Pallas site provides unique observational data and high-intensity field measurement datasets over long periods. The infrastructure for atmosphere- to landscape-scale research in ecosystem processes in a subarctic landscape has recently been complemented with detailed ecohydrological measurements. We identify three dominant processes in subarctic ecohydrology: (a) strong seasonality drives ecohydrological regimes, (b) limited dynamic storage causes rapid stream response to water inputs (snowmelt and intensive storms), and (c) hydrological state of the system regulates catchment-scale dissolved carbon dynamics and greenhouse (GHG) fluxes. Surface water and groundwater interactions play an important role in regulating catchment-scale carbon balances and ecosystem respiration within subarctic peatlands, particularly their spatial variability in the landscape. Based on our observations from Pallas, we highlight key research gaps in subarctic ecohydrology and propose several ways forward. We also demonstrate that the Pallas catchment meets the need for sustaining and pushing the boundaries of critical long-term integrated ecohydrological research in high-latitude environments.