Iron isotopic systematics of UHP eclogites respond to oxidizing fluid during exhumation

The iron stable isotope compositions (δ⁵⁶Fe) and iron valence states of ultrahigh‐pressure eclogites from Bixiling in the Dabie orogen belt, China, were measured to trace the changes of geochemical conditions during vertical transportation of earth materials, for example, oxygen fugacity. The bulk Fe³⁺/ΣFe ratios of retrograde eclogites, determined by Mössbauer spectroscopy, are consistently higher than those of fresh eclogites, suggesting oxidation during retrograde metamorphism and fluid infiltration. The studied eclogites (five samples) display limited mid‐ocean ridge basalts (MORB)‐like (~0.10‰) δ⁵⁶Fe values, which are indistinguishable from their protoliths, that is, gabbro cumulates formed through differentiation of mantle‐derived basaltic magma. This suggests that Fe isotope fractionation during continental subduction is limited. Garnet separates display limited δ⁵⁶Fe variation ranging from ?0.08 ± 0.07 ‰ to 0.02 ± 0.07‰, whereas coexisting omphacite displays a large variation of δ⁵⁶Fe values from 0.15 ± 0.07‰ to 0.47 ± 0.07‰. Omphacite also has highly variable Fe³⁺/ΣFe ratios from 0.367 ± 0.025 to 0.598 ± 0.024, indicating modification after peak metamorphism. Omphacite from retrograde eclogites has elevated Fe³⁺/ΣFe ratios (0.54–0.60) compared to that from fresh eclogites (~0.37), whereas garnet displays a narrow range of ferric iron content with Fe³⁺/ΣFe ratios from 0.039 ± 0.013 to 0.065 ± 0.022. The homogenous δ⁵⁶Fe values and Fe³⁺/ΣFe ratios of garnet suggest that it survived the retrograde metamorphism and preserved its Fe‐isotopic features and ferric contents of peak metamorphism. Because of similar diffusion rates of Fe and Mg in garnet and omphacite, and constant Δ²⁶Mg_{omphacite‐garnet} values (1.14 ± 0.04‰), equilibrium iron isotope fractionation between garnet and omphacite was probably achieved during peak metamorphism. Elevated Fe³⁺/ΣFe ratios of omphacite from retrograde eclogites and variant Δ⁵⁶Fe_{omphacite‐garnet} values of the studied eclogites (0.13 ± 0.10‰ to 0.48 ± 0.10‰) indicate that oxidized geofluid infiltration resulted in the elevation of δ⁵⁶Fe values of omphacite during retrograde metamorphism.     

国内地质灾害机理与防治技术研究现状

根据2013年4月10～12日在北京召开的第六届全国地质灾害与防治学术会议的特邀报告、主题报告以及论文集所报道的目前国内地质灾害机理与防治技术现状,分别从地质灾害成灾机理与减灾对策、地质灾害监测预警、地质灾害防治技术与应急处置、区域地质灾害风险管理与评价等4个方面进行简要介绍和分析。这些方面的研究成果代表了目前国内地质灾害机理与防治技术研究的现状和发展方向,对促进我国今后的地质灾害机理与防治技术研究有一定的积极作用。     

钛-氨三乙酸-对氯苯基荧光酮-CTMAB四元配合物的分光光度法研究

本文研究Ti(Ⅳ)-氨三乙酸(NTA)-对氯苯基荧光酮(p-ClPF)-CTMAB四元配合物的显色条件。结果表明,在pH5.8—6.6形成了摩尔比为Ti(Ⅳ):NTA:p-ClPF:CTMAB=1:1:3:3的四元配合物,借此反应测定钛,灵敏度高,其ε_(573nm)=2.1×10~5L·mol~(-1)·cm~(-1)。Ti(Ⅳ)浓度在0—1.4μg/10ml范围服从比耳定律。已用本法直接测定了岩矿和铝合金中的Ti,结果满意。     

银催化HDEA电化学发光法测定矿样中的痕量银

在碱性介质中,痕量Ag(Ⅰ)对新试剂6-(2-羟基-4-二乙基氨苯偶氮)-2,3-二氢-1,4-酞嗪二酮(简称HDEA)的电化学发光具有显著的催化作用。基于此,提出了HDEA-KCI-KOH体系测定矿样中痕量Ag的新方法。方法的检测限为2.0×10~(-8)mol/L Ag,线性范围为5.0×10~(-8)—3.0×10~(-6)mol/L Ag。采用巯基棉富集分离,应用本法测定一些矿样中的Ag,结果良好。     

延安地区上三叠统长6期沉积特征及其演化

通过对川口油田测井曲线和岩心分析,总结了延安地区上三叠统长6期沉积微相特征,建立了长6期岩性和测井曲线的响应模式。再结合分析沉积的演化过程、电性和物性特征、骨架砂体的几何形态和沉积演变,得出该地区沉积相和演化模式。认为从长6₄到长6₁期沉积环境为湖泊、三角洲前缘、三角洲平原亚相到河流相。长6₁、长6₂是主力储层,其物性最好。      

地下连续墙治理地下水污染

介绍一种治理已被严重污染的地下水的方法。即修建一道底部深入到不透水岩层的地下墙,把污染物封闭在由底部不透水岩层和周围地下防渗墙组成的“地下盆”中,降低周围地下水中有害物质的浓度,然后再治理封闭圈内的污染物,以达到彻底根治地下水污染的目的。     

鄂尔多斯盆地南部奥陶系马六段白云岩特征及形成机制研究

鄂尔多斯盆地马六段在盆地大部分地区被剥蚀,仅在盆地周缘地区分布,因此,有关该盆地马六段白云岩成因研究较少。本文通过对马六段白云岩岩石学特征、阴极发光特征、微量元素特征以及碳氧同位素地球化学特征进行分析,对鄂尔多斯盆地南部马六段白云岩特征及形成机制进行了研究。研究结果表明,盆地南部马六段白云岩主要由细—中晶白云岩组成,白云石具"雾心亮边"结构,阴极发光呈暗红色光。微量元素总体上具有较低的Fe、Mn值,平均值分别为447×10~(-6)和62×10~(-6),较高的K、Na值,平均值分别为517×10-6和252×10~(-6),以及中等含量的Sr元素值,平均值为155×10~(-6)。δ~(13)C值平均为-0.617‰,δ~(18)O值平均为-7.6‰,以上特征均反映出海源流体特征。白云石的"雾心"和"亮边"结构中微量元素含量相差不大,认为是在相同成岩环境的不同成岩阶段形成,其中"雾心"形成于浅埋藏环境的渗透回流白云石化作用,而"亮边"是在深埋藏环境下对早期白云石的调整和加强。     

An Experimental Calibration on the Sphalerite-Galena Sulfur Isotope Geothermometer

A new experimental calibration was undertaken in this study to get a more reliable sphalerite-galena sulfur isotope geothermometer. The experimental conditions selected in study were very similar to those of natural hydrothermal solution. The high-precision SF6 method was used in sulfur isotope analyses. The obtained calibration curve for sulfur isotope fractionation between sphalerite and galena can be expressed with the equation 10001nαSp-Gn= 0.74×106T-2+0.08.     

Dissolved Organic Carbon Fractions Formed during Composting of Municipal Solid Waste: Properties and Significance

The properties and transformation of dissolved organic matter (DOM) extracted (10 L water per kilogram compost) from municipal solid waste (MSW) compost at five stages (days 47, 77, 105, 126, and 187) of composting were investigated. The DOM was fractionated into hydrophobic or hydrophilic neutrals, acids, and bases. The unfractionated DOM, the hydrophobic acids and neutrals (HoA and HoN, respectively), and the hydrophilic neutrals (HiN) fractions were studied using solid-state ¹³C-NMR, FTIR, and DRIFT spectroscopy. The HoA fraction was found to be the dominant (percentage of total DOM) hydrophobic fraction, exhibiting a moderate increase during composting. The HoN fraction increased sharply from less than 1% to 18% of the total DOM during 187 days of composting, while the hydrophobic bases (HoB) exhibited the opposite trend. The HiN represented the major fraction of the hydrophiles up to 120 days of composting, decreasing thereafter by 38%. The relative concentration of the hydrophilic acids and bases (HiA and HiB, respectively) exhibited no consistent trend during composting. DRIFT spectra of the unfractionated DOM taken from the composting MSW revealed a decreasing level of polysaccharide structures with time. The ¹³C-NMR and FTIR spectra of the HoA fraction exhibited a polyphenol-humic structure, whereas the HoN spectra exhibited strong aliphatic features. The spectra of the HiN fraction confirmed its polysaccharide nature. During the final stage of composting, the DOM concentration was steady, while a relative decrease of HiN concomitant with an increase of HoA and HoN fractions was observed. These indicate that the DOM contained a low concentration of biodegradable organic matter and a higher content of macromolecules related to humic substances. The biological significance and heavy metal binding of these fractions are being studied based on earlier observations showing enhanced plant growth in the presence of DOM extracted from mature as opposed to immature compost.     

Learning from CDM SD tool experience for Article 6.4 of the Paris Agreement

The Paris Agreement (PA) emphasizes the intrinsic relationship between climate change and sustainable development (SD) and welcomes the 2030 agenda for the global Sustainable Development Goals (SDGs). Yet, there is a lack of assessment approaches to ensure that climate and development goals are achieved in an integrated fashion and trade-offs avoided. Article 6.4 of the PA introduces a new Sustainable Mitigation Mechanism (SMM) with the dual aim to contribute to the mitigation of greenhouse gas emissions and foster SD. The Kyoto Protocol’s Clean Development Mechanism (CDM) has a similar objective and in 2014, the CDM SD tool was launched by the Executive Board of the CDM to highlight the SD benefits of CDM activities. This article analyses the usefulness of the CDM SD tool for stakeholders and compares the SD tool’s SD reporting requirements against other flexible mechanisms and multilateral standards to provide recommendations for improvement. A key conclusion is that the Paris Agreement’s SMM has a stronger political mandate than the CDM to measure that SD impacts are ‘real, measurable and long-term’. Recommendations for an improved CDM SD tool are a relevant starting point to develop rules, modalities, and procedures for SD assessment in Article 6.4 as well as for other cooperative mitigation approaches.

POLICY RELEVANCE

Research findings are relevant for developing the rulebook of modalities and procedures for Article 6.4 of the Paris Agreement, which introduces a new mechanism for mitigation of greenhouse gas emissions and sustainable development. Lessons learnt from the CDM SD tool and recommendations for enhanced SD assessment are discussed in context of Article 6 cooperative approaches, and make a timely contribution to inform negotiations on the rulebook agreed by the Conference of the Parties serving as the Meeting of the Parties to the Paris Agreement.