Carbon isotopes in the rivers from the Lesser Antilles: origin of the carbonic acid consumed by weathering reactions in the Lesser Antilles

In this paper, we use carbon isotopes in the dissolved load of rivers from the Lesser Antilles volcanic arc (Guadeloupe, Martinique and Dominica islands) to constrain the source of the carbon dioxide (CO₂) involved in the neutralization reactions during water–rock interactions. The δ¹³C data span a large range of variations, from –19‰ to –5 · 2‰ for DIC (dissolved inorganic carbon) concentrations ranging from 11 μM to 2000 μM. Coupled with major element concentrations, carbon isotopic ratios are interpreted as reflecting a mixture of magmatic CO₂ (enriched in heavy carbon (δ¹³C ≈ –3 · 5‰) and biogenic CO₂ produced in soils (enriched in light carbon (δ¹³C < –17‰)). Carbon isotopes show that, at the regional scale, 23 to 40% of CO₂ consumed by weathering reactions is of magmatic origin and is transferred to the river system through aquifers under various thermal regimes. These numbers remain first‐order estimates as the major uncertainty in using carbon isotopes as a source tracer is that carbon isotopes can be fractionated by a number of processes, including soil and river degassing. Chemical weathering is clearly, at least, partly controlled by the input of magmatic CO₂, either under hydrothermal (hot) or surficial (cold) weathering regimes. This study shows that the contribution of magmatic CO₂ to chemical weathering is an additional parameter that could explain the high weathering rates of volcanic rocks. The study also shows that a significant part of the carbon degassed from the Earth's interior is not released as CO₂ to the atmosphere, but as DIC to the ocean because it interacts with the groundwater system. This study calls for a better understanding of the contributions of deep carbon to the hydrosphere and its influence on the development of the Critical Zone. Copyright © 2013 John Wiley & Sons, Ltd.     

Solute geothermometry of springs and wells of the Los Azufres and Las Tres Vírgenes geothermal fields,Mexico

Subsurface reservoir temperatures of two important Mexican geothermal systems (Los Azufres and Las Tres Vírgenes) were estimated by applying all available solute geothermometers for 88 and 56 chemical data measurements of the spring waters and fluids of the deep geothermal wells, respectively. Most of the chemical data for spring water of these two geothermal fields are for HCO₃ water, followed by SO₄ and Cl types. For the Los Azufres geothermal field (LAGF), the reservoir temperatures estimated by Na-K geothermometers for springs of HCO₃ and SO₄ waters, and by Na-Li and Li-Mg geothermometers for Cl water, are close to the average bottom-hole temperature (BHT) of the geothermal wells. However, all reservoir temperatures for spring waters from the Las Tres Vírgenes geothermal field (LTVGF) estimated by all solute geothermometers indicated significantly large differences (low temperatures) compared to the BHT. Evaluation of inferred reservoir temperatures for spring waters of the LAGF and LTVGF suggests that not all springs nor all solute geothermometers provide reliable estimation of the reservoir temperatures. Even though chemical equilibrium probably was not achieved in the water–rock system, Na-K geothermometers for HCO₃ water (peripheral water mainly of meteoric origin with little geothermal component) and SO₄ water (geothermal steam heated) and Na-Li and Li-Mg geothermometers for Cl-rich spring water (fully mature geothermal water) of the LAGF indicated reservoir temperatures close to the BHT. However, in comparison with the geothermometry of spring water of the LAGF and LTVGF, fluid measurements from geothermal wells of these two fields indicated reservoir temperatures in close agreement with their respective BHTs. For the best use of the solute geothermometry for spring water, it is advisable to: (1) chemically classify the springs based on water types; (2) identify and eliminate the discordant outlier observations by considering each water type as a separate sampled population; (3) apply all available solute geothermometers employing a suitable computer program such as SolGeo instead of using some specific, arbitrarily chosen geothermometers; and (4) evaluate the temperatures obtained for each solute geothermometer by considering the subsurface lithology, hydrological conditions, and BHTs or static formation temperatures whenever available.     

http://www.sciencedirect.com/science/article/pii/S1674987111001332

Isoprenoidal glycerol dialkyl glycerol tetraethers（iGDGTs） from the Gulu hot springs （23-83.6℃,pH>7） and Yangbajing hot springs（80—128℃,pH>7） were analyzed in order to investigate the distribution of archaeal lipids among different hot springs in Tibet.A soil sample from Gulu was incubated at different temperatures and analyzed for changes in iGDGTs to help evaluate whether surrounding soil may contribute to the iGDGTs in hot springs.The sources of bacterial GDGTs（bGDGTs） in these hot springs were also investigated.The results revealed different profiles of iGDGTs between Gulu and Yangbajing hot springs. Core iGDGTs and polar iGDGTs also presented different patterns in each hot spring.The PCA analysis showed that the structure of polar iGDGTs can be explained by three factors and suggested multiple sources of these compounds.Bivariate correlation analysis showed significant positive correlations between polar and core bGDGTs.suggesting the in situ production of bGDGTs in the hot springs.Furthermore,in the soil incubation experiment,temperature had the most significant influence on concentration of bGDGTs rather than iGDGTs.and polar bGDGTs had greater variability than core bGDGTs with changing temperature.Our results indicated that soil input had little influence on the composition of GDGTs in Tibetan hot springs. On the other hand,ring index and TEX₈₆ values were both positively correlated with incubation temperature, suggesting that the structure of archaeal lipids changed in response to varying temperature during incubation.     

Squid mandibles from the stomachs of sperm whales (physeter catodon l.) captured in the cook strait region of New Zealand

The lower mandibles of squid in the stomachs of two sperm whales examined at the Tory Channel whaling station in 1963–4 were separated into 11 types according to a system of grouping devised by the authors and based on a key drawn up by M. R. Clarke.     

航空摄影测量模式下的海岸线综合推算技术

论证了航空摄影测量模式下由潮位推算技术确定岸线的基本原理,设计了岸线高程确定的两种技术方案,分析了岸线高程确定的精度,介绍了该技术的工程应用。     

文登市地热资源现状及开发建议

文登市地热温泉资源丰富,且开发历史悠久。为更好地保护开发地热资源,文登市国土资源局确立了＂有效节约和保护矿产资源,加强地热资源开发利用管理,打造中国温泉之都,构建资源节约型、环境友好型社会＂的指导思想。在充分考虑区域温泉地质条件、资源勘查程度、温泉水质量及其开发利用现状的基础上,结合规划区内各地段产业结构特点、地理条件、经济发展水平及未来产业结构调整方向,按照走集约化开发、规模化发展的总体思路,全面整顿和规范文登地热资源开发秩序。通过强化温泉资源开发审批、建立勘查开发利用投入机制、加强温泉资源的勘查与保护工作和加大查处力度等措施,全面提升了地热资源开发利用水平。     

涞源北盆地地下水氢氧同位素特征及北海泉形成模式

拒马源泉群作为拒马河的源头,受到了较多专家和学者的关注。但这些研究多集中在地下水的水化学、水位动态、泉流量等特征上,对地下水氢氧同位素特征的分析几乎没有,且对北海泉的成因解释多为粗略的定性概述。为了说明涞源北盆地地下水的氢氧同位素特征,详细揭示北海泉的形成模式,首次系统地采集了不同含水岩组的地下水样品,测定了水样的氢氧同位素组分。结果表明:样品点δD和δ18O值均落在区域大气降水线上或附近,大气降水是研究区地下水的主要补给来源;白云岩、灰岩含水岩组高程效应较明显,径流途径长,松散含水层径流途径短,受蒸发作用较强;白云岩、灰岩含水岩组和松散含水层氘盈余d值分别为6.0‰～11.6‰、4.2‰～11.2‰、3.8‰～8.0‰,较大气降水大部分偏小,表明岩溶水和松散孔隙水经历了不同的流动过程;白云岩、灰岩含水岩组从补给区向排泄区各自流动过程中,在小西庄、香炉屯村附近断裂带发生沟通混合,然后在向盆地中心径流过程中受断层阻水上升,上升过程中又接受了松散孔隙水的补给,最后在松散岩层中出露成泉,形成北海泉。在孔隙水混入前,两者的平均补给比例大约为48.4%～57.6%和42.4%～51.6%。     

藏北羌塘中部吉瓦地热田的特征及其资源评价

吉瓦温泉位于西藏尼玛县绒马乡吉瓦村北。温泉出露于一个新生代断陷盆地之中,受江爱藏布活动断裂带的控制。地下热水矿化度为5.54×103~5.58×103mg/L,水化学类型属Na-Cl·HCO3型。温泉水中H2SiO3、Li+、F-等含量较高,这3项指标满足医疗矿水的标准。热水系统的热源来自于地壳中的部分熔融层,热水的补给来源主要为大气降水,伴有深部热液加入。混合模型研究显示,温泉水为地下热水和冷水的混合物,冷水占的比例介于77%~95%之间,混合水的循环年龄约31a,利用SiO2温标法计算出浅部热储温度为120℃,深度为832m。混合前热水温度为215~280℃,对应深部热储深度为1466~1900m。吉瓦热田面积约6km2,天然放热量为7.53×1013 J/a,地热资源量为32606×1014 J。