Altitude et géochimie des eaux de source,Nord-Ouest du Massif central,France

In the northwestern Massif Central (France), groundwater chloride concentrations are inversely correlated with elevation, when nitrate-poor. This can be explained by an evolution of the ratio evapotranspiration/rainfall, or of the rainwater composition. Such a relationship may be used for the detection of denitrification phenomena in groundwaters, or nitrate assimilation in surface waters, or for the computation of evapotranspiration, using the chloride mass balance method. However, the main objective will be the selection of groundwaters free of any chloride-bearing contamination, in order to define the natural groundwater quality background. To cite this article: J. Barbier, C. R. Geoscience 337 (2005).     

Glacier Retreat, Mass-Balance and Thinning: Sermilik Glacier, South Greenland

This study documents thinning and retreat of the South Greenland ice margin and discusses possible reasons in the light of mass‐balance and change of dynamic conditions. Analyses of satellite images have shown that the glacier tongue of Sermilik glacier disintegrated within the past 15 years. Furthermore, the observed thinning close to the Sermilik glacier front was as much as 120 m water equivalent during this period. This figure was derived by comparing surface elevation data from a digital elevation model (1985) and laser altimeter measurements from the year 2000, showing surface elevation changes along a flow line of Sermilik glacier. Mass‐balance data from in situ measurements performed at a centre flow line of the glacier are presented. These data are compared to results from remote sensing analyses of the study area. Net ablation reconstruction over the last 41 years from positive‐degree‐day modelling, at various locations along the Sermilik glacier massbalance transect, shows an increase during the past decades. These analyses indicate that only 55% of the total thinning in this area can be explained by mass‐balance changes. The remaining 45% of the thinning is attributed to changes in the dynamic behaviour of the glacier, such as an increase of creep towards the end of the twentieth century. The significant thinning along the Qagssimiut lobe can also be explained as a combination of mass‐balance changes and changes in ice dynamic behaviour.     

地球化学开放系统的质量平衡:1.理论

从质量守恒原理出发推导出开放系统两个新的质量平衡方程：Ｃ＾ｏｉ－Ｃ＾Ａｉ－△Ｃｉ,（Ｃ＾Ｏｉ－Ｃ＾Ａｉ）／Ｃ＾Ｏｉ＝μ（Ｃ＾Ａｉ／Ｃ＾Ｏｉ）－μｉ。该方程不公在图示和计算方面均优于Ｇｒａｎｔ方程,而且还同时将Ｂｒｉｍｈａｌｌ和Ｄｉｅｔｒｉｃｈ质量平衡方程作为一个特例而包容它。     

江苏东海榴辉岩向斜长角闪岩转化的研究

东海榴辉岩曾被俯冲到上地幔，而后又折返回地表，经历了宽广的温度、压力、应力、流体条件等变化范围，形成了大量矿物反应结构，为研究岩石矿物反应提供了很好的素材。本文选取东海地区一个保留从初始榴辉岩到斜长角闪岩完整退变质序列的榴辉岩体作为研究对象，通过详细的显微结构观察、矿物成分分析、成分空间分析、成分迁移估算，揭示了东海榴辉岩向斜长角闪岩的转化过程。该过程可划分为两个阶段：早期为替代绿辉石的后成合晶形成阶段，通过绿辉石内部端元组分间的反应实现，反应产物之一的Fe^2 与金红石结合形成钛铁矿，Ca、Mg被排出到绿辉石体系之外。晚期退变为流体的渗滤交代作用，表现为石榴子石被角闪石部分取代、后成合晶的角闪石化，以及黝帘石、白云母的形成。退变质的最后阶段为石榴子石被绿帘石 角闪石 赤铁矿完全替代。榴辉岩转化成含帘石的斜长角闪岩。     

罗布泊卤水的相图分析研究

通过对罗布泊北部卤水依据不同温度下的Na~+、K~+、Mg~(2+)||Cl~-、SO_4~(2-)—H_2O体系相图分析,分别给出氯化钠、氯化钾、硫酸钾、一水硫酸镁综合开发利用罗布泊卤水的原则性工艺流程,并提出了在不同的生产阶段科学的工艺路线。这一具有较高的回收率和产品质量,为开发利用罗布泊北部卤水提供了理论依据。     

Using remote sensing to regionalize local precipitation recharge rates obtained from the Chloride Method

Water supply in semiarid Botswana is, to a large extent, based on groundwater. In the planning of a groundwater abstraction scheme, criteria for the sustainability of the abstraction with respect to both quantity and quality have to be satisfied. The most important parameter in the context of quantitative sustainability is the long-term average groundwater recharge together with its spatial distribution. A method is developed to calculate a recharge map that can be used in a groundwater model. The relative distribution of recharge is obtained from remotely sensed data and then calibrated with local values of recharge derived from the Chloride Method. The method was tested for two sites in Botswana, the Chobe Region and Ngamiland.     

Genetic link between saline and carbonatitic mantle fluids: The system NaCl-CaCO3-MgCO3 ± H2O ± Fe0 at 6 GPa

Melt inclusions in kimberlitic minerals and diamonds indicate that chlorides are important constituents of mantle carbonatite melts. Besides, alkaline chlorides are important constituents of saline high-density fluids (HDFs) found in diamonds from kimberlites and placers around the world. Continuous compositional variations suggest that saline and carbonatitic HDFs could be genetically linked. However, the essence of this link remains unclear owing to the lack of data on phase relations in the chloride-carbonate systems under pressure. Here we studied subsolidus and melting phase relations in the system NaCl–CaCO₃–MgCO₃ at 6 GPa and 1000–1600 °C using a Kawai-type multianvil press. We found that at 1000 °C, subsolidus assemblage consists of halite, magnesite, and aragonite. At higher temperatures, the stabilization of dolomite splits the subsolidus area into two partial ternary fields: halite + magnesite + dolomite and halite + dolomite + aragonite. The minimum on the liquidus surface corresponds to the halite-dolomite-aragonite ternary eutectic, situated at 1100 °C. The eutectic melt has Ca# 89 and contains 30 wt.% NaCl (26 mol% 2NaCl). The system has two ternary peritectics: halite + dolomite = magnesite + liquid located near the ternary eutectic and magnesite + dolomite = Mg-dolomite + liquid situated between 1300 and 1400 °C. Although under dry conditions incipient melting yields carbonate-dominated melt, the addition of water facilitates the fusion of NaCl and expands the liquid field to NaCl-rich compositions with up to 70 wt.% NaCl. The obtained results favor the idea that hydrous saline melts/fluids (brines) found as inclusions in diamonds could be a lower temperature derivative of mantle carbonatite melts and disagree with the hypothesis on chloride melt generation owing to the chloride-carbonate liquid immiscibility since no such immiscibility was established. We also studied the interaction of the NaCl–CaCO₃–MgCO₃ system with iron metal and found that carbonate reduction produces C-bearing species (Fe⁰, Fe-C melt, Fe₃C, Fe₇C₃, C⁰) and wüstite containing Na₂O, CaO, and MgO. Besides, a carbonate chloride compound, Ca₂Cl₂CO₃, was established among the reaction products. The interaction between NaCl-bearing carbonate melt shifts its composition toward Mg-poor and NaCl-rich. Given the above, an alternative hypothesis can be proposed, according to which the interaction of alkaline chloride-bearing carbonate melts formed in the subduction zones with the reduced mantle should be accompanied by diamond crystallization and shift the composition of the melt from carbonatitic to alkali-rich saline.     

Use of Pitzer Equations to Examine the Formation of Mercury(II) Hydroxide and Chloride Complexes in NaClO<Subscript>4</Subscript> Media

The thermodynamic stability constants for the hydrolysis and formation of mercury (Hg²⁺) chloride complexes

Application of a mass-balance model to predict PCDD/F turnover in a Baltic coastal estuary

A dynamical, process-based mass-balance model was applied to quantify the transports of polychlorinated-p-dibenzodioxins and dibenzofurans (PCDD/Fs) to, within and from the Kallrigafjärden Bay, a coastal estuary in the Baltic Sea, and to predict the PCDD/F levels in the water and sediments of the bay. Before the modelling, a one-year sampling programme was implemented in 2007–2008 to measure the flows of PCDD/Fs in tributaries entering the system, the fluxes from the adjacent sea and the levels in water, sediment and fish within the estuary. The collected data set was used as input data to the model and for validation purposes.     

Estimating groundwater recharge in a cold desert environment in northern China using chloride

Understanding sources and rates of recharge to the Badain Jaran Desert in northern China is important for assessing sustainability of the area’s oasis lake ecosystem and its water resources in general. For this purpose, direct recharge was investigated with the chloride mass balance method for 18 unsaturated zone profiles (6–16 m depth). Spatial variability is low across the area (range in mean Cl in profiles: 62–164 mg/L Cl), largely attributable to the uniformity of sandy unsaturated zone conditions. No strong correlations between environmental factors of profile locations and recharge rates were found, though a weak relationship between recharge and vegetation density was suggested. The study area’s complex dune morphology appears to have no measurable impact on recharge variability. Mean estimated diffuse recharge is 1.4 mm/year (1.0–3.6 mm/year for 95% confidence level), approximately 1.7% of mean annual precipitation. Temporal fluctuations in recharge due to climate variability are apparent and there is good correspondence in temporal trends over a time span of 200–300 years. Water balance considerations indicate that direct recharge is insufficient to support the numerous perennial lakes in the study area, suggesting that diffuse recharge presently plays a minor role in the overall water balance of the desert’s shallow Quaternary aquifer.