苏州阳西高岭土矿床氢氧稳定同位素特征

苏州阳西南岭土矿床按成因可分为脉岩型高岭土及溶洞充填型高岭土.高岭土的氢氧稳定同位素组成变化大,取决于样品的采集部位.在δD—δ~(18)O相关图上,以δ~(18)O=19‰为界,可分为A、B两区.脉岩型的残斑状高岭土氢氧同位素组成位于A区(δ~(18)O<19‰);而溶洞充填型的致密块状高岭土的氢氧同位素组成位于B区(δ~(18)O>19‰).据此可以认为脉岩型高岭土以热液成矿作用为主,溶洞充填型高岭土以风化淋滤作用为主.并分别在成矿后又受到了后期作用的叠加改造.     

Using water isotopes and hydrogeochemical evidences to characterize groundwater age and recharge rate in the Zhangjiakou area,North China

Despite the increasing depletion of the groundwater at the Zhangjiakou aquifer system in the northwest of Beijing-Tianjin-Hebei region, little information is available on the hydrological process of groundwater in this region. In this study, we utilized water isotopes composition(δ~(18) O, δD and ~3 H) of groundwater, river and precipitation to identify the characteristics of hydrochemistry, groundwater age and recharge rates in different watersheds of the Zhangjiakou area. Results showed that the river water and groundwater could be characterized as HCO_3-Mg·Na, HCO_3·Cl-Na and HCO_3-Mg·Na, HCO_3·Cl-Na, HCO_3·Cl-Na·Mg types, respectively. The δD and δ~(18) O values in precipitation were linearly correlated, which is similar to the Global Meteorological Water Line(GMWL). Furthermore, the decreasing values of the δD and δ~(18) O from precipitation to surface water and groundwater indicate that groundwater is mainly recharged by atmospheric precipitation. In addition, the variation of 3 H concentration with depth suggests that groundwater shallower than around 100 m is generally modern water. In contrast, groundwater deeper around 100 m is a mixture of modern and old waters, which has longer residence times. Groundwater showed a relatively low tritium concentration in the confined aquifers, indicating the groundwater recharged might be relatively old groundwater of over 60 years. The flow velocity of the groundwater in the study area varied from 1.10 to 2.26 m/a, and the recharge rates ranged from 0.034 to 0.203 m/a. The obtained findings provide important insights into understanding the groundwater recharge sources and hydrochemistry in the Zhangjiakou area, in turn developing a sustainable groundwater management plan.     

渝东南断裂型碳酸盐岩地热水的形成特征

通过水化学法和同位素示踪法对渝东南断裂型碳酸盐岩地热水的地球化学特征及其水资源的形成进行研究。结果表明:郁山断裂以西地热水的水化学类型为Cl-Na型,断裂以东地热水以SO4-Ca?Mg型为主。根据Gibbs图,郁山断裂以西、以东的地热水分别受到蒸发浓缩和岩石风化作用的影响;断裂以西地热水的γNa+/γCl-接近1,表明地热水中高浓度的Cl-和Na+主要是源于地层中岩盐的溶解;断裂以东地热水的γ（Ca2++Mg2+）/γ（HCO_3^-+ SO〖_4^(2-)〗）接近1,表明地热水中高浓度的Ca2+和SO〖_4^(2-)〗主要来源于地层中膏岩的溶解。地热水的δD和δ18O值分别为-64.7‰~-50‰和-9.17‰~-7.89‰,分布在当地大气降水线两侧,表明补给来源主要为大气降水。地热水水源平均补给高程为1 278 m,这很可能来自附近岩溶中山地区。其热储温度为41~90 ℃,平均热储温度为66℃;循环深度为1 000~3 500 m,平均值为2 300 m。大气降水到达地表后,在重力（地形）作用下向深部径流,接受地球内部的热传导形成地热水,由西北向东南流动,沿着断裂带上涌,并接受冷水的混入。      

四川甲基卡锂矿区二长花岗岩的地球化学、氢氧同位素组成及其地质意义

四川甲基卡锂矿床为超大型锂矿床,矿区南部呈岩株状产出的二云母花岗岩与稀有金属伟晶岩在时间、空间及成因上具有密切关系。通过对该岩体元素地球化学特征和氢氧同位素组成的研究,探讨了其在稀有金属成矿过程中的作用。研究结果表明,甲基卡二云母花岗岩为富硅、高钾、钙碱性、强过铝质S型花岗岩,其稀土总量较低,岩浆来源为三叠系西康群砂泥岩为代表的地壳物质的部分熔融,流体来源可能是岩浆水和变质水的混合水。岩体微量元素R型聚类分析显示,与稀有金属成矿最密切的元素为Li、Rb、Ti、W、Mn,而岩体稀有元素含量的变化规律指示岩体北侧成矿效率高于南侧,是下一步找矿工作的重点。综合地球化学、氢氧同位素及前人研究,认为花岗岩浆在底辟侵入过程中可能发生了不混溶作用,由此分离出的伟晶岩浆在运移过程中稀有金属得到不断富集,最终形成伟晶岩型稀有金属矿床。     

Plant source water apportionment using stable isotopes: A comparison of simple linear,two‐compartment mixing model approaches

Plant source water identification using stable isotopes is now a common practice in ecohydrological process investigations. Notwithstanding, little critical evaluation of the approaches for source apportionment have been conducted. Here, we present a critical evaluation of the main methods used for source apportionment between vadose and saturated zone water: simple mass balance and Bayesian mixing models. We leverage new isotope stem water samples from a diverse set of tree species in a strikingly uniform terrain and soil conditions at the Christchurch Botanic Garden, New Zealand. Our results show that using δ²H alone in a simple, two‐source mass balance approach leads to erroneous results, particularly an apparent overestimation of groundwater contribution to xylem. Alternatively, using both δ²H and δ¹⁸O in a Bayesian inference framework improves the source water estimates and is more useful than the simple mass balance approach, particularly when soil and groundwater contributions are relatively disproportionate. We suggest that plant source water quantification methods should take into consideration the possible effects of ²H/¹H fractionation. The Bayesian inference approach used here may be less sensitive to ²H/¹H fractionation effects than simple mass balance methods.     

滇西云龙锡矿流体包裹体及稳定同位素研究

对云龙锡矿流体包裹体及氢、氧同位素的研究表明 ,该矿床至少存在两个矿化阶段 :早期的高温 (≥40 0℃ )及晚期的中—高温 (30 0～ 40 0℃ )矿化阶段。早期的矿化流体的δ1 8OH2 O(7.7‰～ 9.0‰ )和δDH2 O(- 5 8‰～ - 43‰ )值相对较高 ,主要是由岩浆水或 和变质水组成 ;晚期由于有大量演化了的大气降水的加入 ,使流体的δ1 8OH2 O值 ,特别是δDH2 O 值降低。在此期间 ,大气降水与岩浆水或 和变质水不同比例的混合 ,使流体的盐度产生不同程度的波动 ,并在石英中形成了不同类型的流体包裹体。     

川东北飞仙关组鲕滩天然气地球化学特征与成因

四川盆地东北部下三叠统飞仙关组鲕滩气藏天然气烃类气体以甲烷为主,含量主要分布在75%～90%之间,C2 含量很少,为0%～0.15%,干燥系数为0.997 0～0.999 8,是典型的干气;非烃气体以H2S和CO2为主,含量分别为4.21%～16.24%和0.97%～10.41%.天然气δ13C1值为-29.0‰～-31.5‰,δ13C2值为-29.4‰～-32.4‰.多参数表明鲕滩气藏天然气是以腐泥型为主的高过成熟天然气.高含H2S的天然气分布区域与含石膏地层分布基本一致,这些H2S为飞仙关组气藏附近的石膏经热化学硫酸盐还原作用(TSR)而生成,CO2是其主要的副产物.在TSR过程中,C2 重烃气体比甲烷更容易与硫酸盐发生反应,也就是C2 重烃气体的消耗速率大于甲烷,从而导致发生TSR反应的天然气C2 含量低、H2S和CO2含量高.天然气δ13C1值与甲烷含量之间具有很好的负相关关系,而与天然气酸性系数[H2S/(H2S CnH2n 2)]具有正相关关系.根据同位素动力学的分馏效应,随着TSR的进行,烃类分子中的12C损耗速率大于13C,残留下来的烃类分子中则更加富集13C,也就是TSR反应使天然气碳同位素变重.     

Discrete element analysis of breakage of irregularly shaped railway ballast

In order to reduce the maintenance costs of ballasted railway track and improve passenger comfort, the railway ballast particle breakage and its effect on track settlement need to be better understood. The failure process of individual railway ballast loaded between flat platens is simulated using the discrete element method, considering its irregular shape with the incorporation of parallel bonds. The tensile strength, the stress of a survival probability of 37% of samples, is obtained and compared with laboratory results from published literature for the verification of DEM simulations. The evolution to failure of the particle is understood from the stress-strain curve and progressive failure modes. The internal breakage mechanisms are analysed by tracking the accumulation of bond breakage number and the contact force distributions.     

冲绳海槽中南部柱状沉积物氧化还原敏感元素赋存机理与环境指示意义

沉积物中氧化还原敏感元素（Redox Sensitive Element,RSE）含量变化是上覆水体氧化还原环境良好的替代指标。本文通过冲绳海槽中南部两个柱状沉积物（深度：30 cm）粒度、总有机碳、总氮及其同位素含量和氧化还原敏感元素含量等指标,探究复杂环境背景下冲绳海槽柱状沉积物中RSE的赋存机理与环境指示意义。研究发现,柱状沉积物中除了Cr亏损,其他RSE均显示有不同程度的富集。“粒控效应”对冲绳海槽柱状沉积物的RSE含量影响较小;分析可知,海水表层生产力是影响沉积物氧化还原环境的主要因素,通过Mn（氢）氧化物的吸附或解吸附作用实现RSE的富集与亏损。δCe、V/Cr、Ni/Co和V/（V+Ni）等指标指示沉积物整体处于氧化−弱氧化环境。沉积物中Mn元素通过还原作用以Mn²⁺形式向上扩散,在25～30 cm处被含氧间隙水氧化富集形成锰峰,指示柱状沉积物0～25 cm处为氧化环境,25～30 cm处为弱氧化环境。     

Water sources of plants and groundwater in typical ecosystems in the lower reaches of the Heihe River Basin

Stable oxygen and hydrogen isotopic compositions （δ18O and δD） of soil water and shallow groundwater of a riparian forest, an artificial shrub forest, and Gobi of the lower reaches of the Heihe River Basin are used to study the recharge water sources of those ecosystems. IsoSource software is used to determine the δ180 values for root water of Populous euphratica and Tamarix ramosissima in the riparian forest ecosystem, Haloxylon ammodendron in the artificial shrub forest, and Reaumuria soongorica in the Gobi, as well as for local soil water and groundwater, and precipitation in the upper reaches of the Heihe River Basin. Our results showed that soil water and shallow groundwater of the riparian forest and the artificial shrub forest were recharged by river water which originated from precipitation in the upper reaches, and strong evaporation occurred in the artificial shrub forest. Soil water of the Gobi was not affected by Heihe River water due to this area being far away from the river channel. The main water sources of Populous euphratica were from 40-60-cm soil water and groundwater, and of Tamarix ramosissima were from 40-80-cm soil water in the riparian forest ecosystem. In the artificial forest, Haloxylon ammodendron used 200-cm saturated-layer soil water and shallow groundwater. The Reaumuria soongorica mainly used soil water from the 175-200-cm depth in the Gobi. Therefore, soil water and groundwater are the main water sources which maintain survival and growth of the plants in the extremely arid regions of the lower reaches of the Heihe River Basin.