北京地区铬的土壤化学地理

本文以化学地理学的观点，讨论了铬在土壤中的来源，分布规律，迁移和残留累积，生态和环境效应，循环与平衡，预测和评价。     

辽东地区水系样品中铬尖晶石特征

铬尖晶石以在风化过程中稳定性高,分布广等特征作为寻找金刚石的重要指示矿物已在找矿中取得了较满意的结果。根据普查找矿中的水系重砂样品所获取的大量铬尖晶石的分布特征、晶体形态、化学成分,以及辽宁已知金伯利岩中铬尖晶石的物理化学特征,将水系重砂中铬尖晶石与金伯利岩中铬尖晶石进行对比。研究表明,辽东北部、中部地区的铬尖晶石基本上不是来自有价值的金伯利岩,而南部地区的铬尖晶石许多是来自有价值的金伯利岩。     

原料配比对氯氧镁水泥固化砾石土干密度的影响

干密度是评价软土固化质量的重要指标,一般通过室内击实试验获得。以氯氧镁水泥(MOC)为结合料,砾石土为固化对象,研究了原料配比对MOC固化砾石土击实性能的影响。通过室内击实试验,考察了轻烧镁粉掺量、卤水浓度、卤水掺量和活性MgO/MgCl_2物质的量比(Mg/Cl比)影响混合料干密度的规律。结果表明:MOC固化砾石土击实料的干密度随卤水掺量增加先增加后降低,随轻烧镁粉掺量及Mg/Cl比的增加而先增加后降低,随卤水浓度及轻烧镁粉掺量的增加而增加,随卤水浓度增加及Mg/Cl比降低而增加。     

柴达木盐湖化工科学研究联合基金实施概况

对2014~2017年国家自然科学基金委员会—青海省人民政府柴达木盐湖化工科学研究联合基金申报与资助项目进行分析,重点研究联合基金实施概况,指出实施成效及存在的问题,并提出解决相关问题的发展建议,通过对联合基金资助和实施结果进行探讨,不断总结经验,优化模式,更好地为柴达木盐湖化工科学研究联合基金创新发展提供制度保障和参考依据。     

Hydrogeochemical and Stable Isotope Characteristics of the River Idrijca (Slovenia), the Boundary Watershed Between the Adriatic and Black Seas

The hydrogeochemical and isotope characteristics of the River Idrijca, Slovenia, where the world’s second largest mercury (Hg) mine is located, were investigated. The River Idrijca, a typical steep mountain river, has an HCO₃ ⁻–Ca²⁺–Mg²⁺ chemical composition. Its Ca²⁺/Mg²⁺ molar ratio indicates that dolomite weathering prevails in the watershed. The River Idrijca and its tributaries are oversaturated with respect to calcite and dolomite. The pCO₂ pressure is up to 13 times over atmospheric pressure and represents a source of CO₂ to the atmosphere. δ¹⁸O values in river water indicate primary control from precipitation and enrichment of the heavy oxygen isotope of infiltrating water recharging the River Idrijca from its slopes. The δ¹³C_DIC values range from −10.8 to −6.6‰ and are controlled by biogeochemical processes in terrestrial environments and in the stream: (1) exchange with atmospheric CO₂, (2) degradation of organic matter, (3) dissolution of carbonates, and (4) tributaries. The contributions of these inputs were calculated according to steady state equations and are estimated to be—11%:19%:30%:61% in the autumn and 0%:26%:39%:35% in the spring sampling seasons.     

Seawater-like trace element signatures (REE + Y) of Eoarchaean chemical sedimentary rocks from southern West Greenland,and their corruption during high-grade metamorphism

Modern chemical sediments display a distinctive rare earth element + yttrium (REE + Y) pattern involving depleted LREE, positive La/La*_SN, Eu/Eu*_SN, and Y_SN anomalies (SN = shale normalised) that is related to precipitation from circumneutral to high pH waters with solution complexation of the REEs dominated by carbonate ions. This is often interpreted as reflecting precipitation from surface waters (usually marine). The oldest broadly accepted chemical sediments are c. 3,700 Ma amphibolite facies banded iron-formation (BIF) units in the Isua supracrustal belt, Greenland. Isua BIFs, including the BIF international reference material IF-G are generally considered to be seawater precipitates, and display these REE + Y patterns (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004). Greenland Eoarchaean BIF metamorphosed up to granulite facies from several localities in the vicinity of Akilia (island), display REE + Y patterns identical to Isua BIF, consistent with an origin by chemical sedimentation from seawater and a paucity of clastic input. Furthermore, the much-debated magnetite-bearing siliceous unit of “earliest life” rocks (sample G91/26) from Akilia has the same REE + Y pattern. This suggests that sample G91/26 is also a chemical sediment, contrary to previous assertions (Bolhar et al. in Earth Planet Sci Lett 222:43–60, 2004), and including suggestions that the Akilia unit containing G91/26 consists entirely of silica-penetrated, metasomatised, mafic rock (Fedo and Whitehouse 2002a). Integration of our trace element data with those of Bolhar et al. (Earth Planet Sci Lett 222:43–60, 2004) demonstrates that Eoarchaean siliceous rocks in Greenland, with ages from 3.6 to 3.85 Ga, have diverse trace element signatures. There are now geographically-dispersed, widespread examples with Isua BIF-like REE + Y signatures, that are interpreted as chemically unaltered, albeit metamorphosed, chemical sediments. Other samples retain remnants of LREE depletion but are beginning to lose the distinct La, Eu and Y positive anomalies and are interpreted as metasomatised chemical sediments. Finally there are some siliceous samples with completely different trace element patterns that are interpreted as rocks of non-sedimentary origin, and include metasomatised mafic rocks. The positive La/La*_SN, Eu/Eu*_SN and Y_SN anomalies found in Isua BIFs and other Eoarchaean Greenland samples, such as G91/26 from Akilia, suggests that the processes of carbonate ion complexation controlling the REE − Y patterns were already established in the hydrosphere at the start of the sedimentary record 3,600–3,850 Ma ago. This is in accord with the presence of Eoarchaean siderite-bearing marbles of sedimentary origin, and suggests that CO₂ may have been a significant greenhouse gas at that time.     

Effects of groundwater level fluctuation on its chemical composition in karst soils of Lithuania

Groundwater regime and mineralization process in moraine sandy loam and peat soils of the active sulphatic karst zone (karst processes develop in the Upper Devonian gypsum–dolomites) in Lithuania and the dependence of chemical compounds concentrations on water level fluctuations are reviewed. According to ion sum, groundwater mineralization in peat soil is 1.1–1.3 times higher than in loam soil. Based on this result, lower levels of groundwater predetermine a more intensive mineralization process. A stronger correlation was determined between groundwater levels and concentrations of chemical compounds (Ca²⁺, Mg²⁺, SO₄ ²⁻ and HCO₃ ⁻) enhancing groundwater mineralization. In mineral soil (sandy loam) nitrate (NO₃)⁻ concentration is highly influenced by changing stages of groundwater level as well as by nearby sinkholes.     

Geochemistry of Renuka Lake and wetland sediments,Lesser Himalaya (India): implications for source-area weathering,provenance, and tectonic setting

The geochemical investigation of sediments deposited in the Renuka Lake basin and its adjoining wetland has shown variation in the distribution and concentration of major, trace and REEs. The major elements are depleted in the lake in relation to wetland and that of Post Archaean Australian, Shale (PAAS), except for CaO which is strikingly in excess and has a dilution effect on SiO₂ and other oxides and trace elements. The Wetland sediments, on the other hand, are enriched in Al₂O₃, Fe₂O₃, K₂O and TiO₂ and the latter three show a positive correlation with Al₂O₃ in both wetland and lake sediments suggesting their association with phyllosilicates and similar source rocks. The enrichment of Y, Zr, Ni, Th, U and Nb in wetland compared to lake and their similarity with PAAS in the former, suggests more clay fractions in the wetland. A high Zr/Hf ratio in wetland and lake sediments and a positive correlation of Zr with Y and HREE indicate Zr control on HREEs. However, higher Zr/Yb and Zr/Th ratios in wetland compared to lake indicate mineral sorting during the process of lighter particles (clays) being trapped in wetland soil. This is also reflected from negative correlation of Gd_N/Yb_N with Al₂O₃ and a strong positive correlation with SiO₂ in wetland sediments. The wetland in this context has a control on lake sediment chemistry. The chondrite normalized REE patterns are essentially the same for lake as well as wetland sediments but abundance decreases in the former. The similarity of pattern with that of PAAS and negative Eu anomaly indicates a cratonic source of sediments. In a plot of the individual samples, wetland samples cluster while lake samples are separated indicating fractionation of lake sediments. A strong positive correlation of La_N/Yb_N with Al₂O₃ and a positive correlation of Zr-∑LREE and Zr-La_N/Yb_N suggest that LREEs are controlled by both phyllosilicates and zircon. The chemical index of alteration (CIA) indices in lake sediments and in wetland are higher than PAAS indicating moderate chemical weathering in the source area. The petrography, lack of felsic magmatic rock fragments, and negative correlation between Zr-(Gd/Yb)_C indicate sedimentary source rocks for the detritus. This is in conformity with the Lesser Himalayan sedimentary sequence belonging to neo-Proterozoic–Proterozoic age and constituting lake catchment of Renuka. The tectonic delineation and discriminant function plots of lake and wetland sediments indicate their cratonic and/or quartzose sedimentary orogenic terrain source that has been deposited in a passive margin setting.     

Chemical weathering of granite under acid rainfall environment, Korea

Chemical weathering was investigated by collecting samples from five selected weathering profiles in a high elevation granitic environment located in Seoul, Korea. The overall changes of chemistry and mineralogical textures were examined reflecting weathering degrees of the samples, using polarization microscopy, X-ray diffraction (XRD), electron probe micro analysis (EPMA), X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma–mass spectroscopy (ICP–MS). The chemical distribution in the weathering profiles shows that few trace elements are slightly immobile, whereas most major (particularly Ca and Na) and trace elements are mobile from the beginning of the granite weathering. On the other hand, there were mineralogical changes initiated from a plagioclase breakdown, which shows a characteristic circular dissolved pattern caused by a preferential leaching of Ca cation along grain boundaries and zoning. The biotite in that region is also supposed to be sensitive to exterior environmental condition and may be easily dissolved by acidic percolated water. As a result, it seems that some rock-forming minerals in the granitic rock located in Seoul are significantly unstable due to the environmental condition of acidic rainfall and steep slopes, where they are susceptible to be dissolved incongruently leading some elements to be highly depleted.     

地幔Sr-Nd-Pb同位素演化的综合模型与n维同位素空间 “地幔面”的地质意义

在n维的Sr-Nd-Pb同位素空间中,几乎所有的大洋中脊玄武岩（MORB）和洋岛玄武岩（OIB）都落在一个虚拟平面上,被称为“地幔面（mantle plane）”。“地幔面”描述了大部分玄武岩的同位素地球化学特征,是最重要的、也是最早提出的地幔动力学演化特征之一,但是长期以来关于“地幔面”的内涵和意义并不清楚。本文通过一个综合模型,反演受岩浆作用控制的地幔微量元素（包括各种同位素母体元素）分异、Sr—Nd—Pb同位素演化,并推导出地幔Sr-Nd-Pb同位素演化的二元参数方程形式。模型表明,通过部分熔融向地壳输出相对富硅、富碱的物质成分,是地幔长期演化的主要特点,这个过程受到两个参数一部分融融程度（F）和岩浆分离的时间（t）-的控制,即n维参数可化为2维,因此在n维同位素空间出现“地幔面”的特征。壳源物资循环,能够使局部地幔偏离“地幔面”,就地幔总体统计特征而言,地壳混染的比例很低,不同的统计数据显示大约1％～6％的系统偏差,即可能的地壳混染程度;进一步模拟,可能作出更加精确的估算。