天然膨润土中蒙脱石丰度的定量方法研究

基于膨润土中蒙脱石的基本结构单元在X射线衍射空间的相干散射的分布和总量是一不变量,同一膨润土矿中单位质量蒙脱石的阳离子交换容量和层电荷密度专一性的特点,本研究提出了阳离子交换容量／层电荷密度、阳离子交换容量和X射线衍射多相Rietveld分析三种蒙脱石丰度的定量方法,并测定了我国不同产地、矿物组成和物化性质各异的10种天然膨润土中蒙脱石丰度,分析了可能的干扰因素。结果表明,三种方法测得的蒙脱石丰度值在3％范围内吻合良好,且具有一致的自相关性。     

Flotation of calcareous Mussorie phosphate ore

Separation of Mussorie rock phosphate (P₂O₅ = 20%) from Uttar Pradesh, India, containing pyrite, calcite and other carbonaceous impurities by flotation has been successfully attempted to upgrade the phosphate values. Based on Hallimond cell flotation results of single and synthetic mineral mixtures of calcite and apatite using oleic acid and potassium phosphate, conditions were obtained for the separation of calcite from apatite which is considered to be the most difficult step in the beneficiation of calcareous phosphates. Further studies using 250 g of the mineral (?60 +150 and ?150 mesh fractions, deslimed) in laboratory size Fagergren subaeration machine employed a stagewise flotation viz. carbonaceous materials using terpineol, pyrite using potassium-ethyl xanthate and calcite using oleic acid respectively. Separation was, however, found to be unsatisfactory in the absence of a depressant.Among starch, hydrofluosilicic acid and dipotassium hydrogen phosphate, which were tried as depressants for apatite in the final flotation stage, dipotassium hydrogen phosphate proved to be superior to others. However, the tests with the above fractions did not yield the required grade. This was possibly due to insufficient liberation of the phosphate mineral from the ore body and different experimental conditions due to scale up operations. Experiments conducted using ?200 mesh deslimed fractions has yielded an acceptable grade of 27.6% P₂O₅ with a recovery of about 60%. The results have been explained in terms of the specific adsorption characteristics of phosphate ions on apatite and the liberation size of the mineral.     

Geochemical processes controlling the spatial distribution of selenium in soil and water,west central South Dakota,USA

Selenium (Se) is essential in the human diet, but has a low threshold for toxic concentration. It is recommended that nutrients such as Se should be consumed through foods as part of a normal diet. Se concentrations in crops and meat depend on the amount of labile Se in the soil where crops and forage are grown. Therefore, managing agriculture for optimal Se in grain crops and forage requires an understanding of the distribution and mobility of Se. Elevated concentrations of Se occur in waters, soils, and forage 120 km west of Pierre in west central South Dakota, USA. The research site lies in an elevated, dissected plain where soils developed on gently dipping Pierre Shale. Soils were sampled along catena transects and waters collected from soil, ponds, and shallow borings in areas of known elevated forage and crop Se. Soil extracts from saturated-paste extraction and acid (aqua regia and hydrofluoric acid) extraction were analyzed. Selenate was the dominant Se species in both acid and saturated-paste extracts; selenite and organic Se were below detection (<0.2 ppb) in the same soil extracts. On average, 98% of soil Se was not water-soluble. The distribution of total Se shows much less spatial variation than water-soluble Se in the areas sampled. Se shows correlation with organic carbon in soils and waters, suggesting its association with organic carbon. Ca shows some correlation to Se in acid extracts, but not in saturated-paste extracts or in waters. Total Se shows no significant correlation to Na, Mg, and total S in the soils. Se in saturated-paste extracts and water samples shows good correlations with Na, Mg, and SO₄, suggesting that evaporitic Na–Mg–sulfate minerals may temporarily concentrate water-soluble Se in shallow soils. The dissolution and precipitation of these Na–Mg–sulfate salts together with pH and oxidation–reduction conditions apparently control water-soluble Se distribution and mobilization in shallow subsurface environments.     

Friedrichbeckeite, K (□0.5Na0.5)2 (Mg0.8Mn0.1Fe0.1)2 (Be0.6 Mg0.4)3 [Si12O30], a new milarite-type mineral from the Bellerberg volcano, Eifel area, Germany

Friedrichbeckeite is a new milarite-type mineral. It was found in a single silicate-rich xenolith from a quarry at the Bellerberg volcano near Ettringen, eastern Eifel volcanic area, Germany. It forms thin tabular crystals flattened on {0001}, with a maximum diameter of 0.6 mm and a maximum thickness of 0.1 mm. It is associated with quartz, tridymite, augite, sanidine, magnesiohornblende, enstatite, pyrope, fluorapatite, hematite, braunite and roedderite. Friedrichbeckeite is light yellow, with white to light cream streak and vitreous lustre. It is brittle with irregular fracture and no cleavage, Mohs hardness of 6, calculated density is 2.686 gcm^?3. Optically, it is uniaxial positive with n_ω = 1.552(2) and n_ε = 1.561(2) at 589.3 nm and a distinct pleochroism from yellow (//ω) to light blue (//ε). Electron microprobe analyses yielded (wt.%): Na₂O 2.73, K₂O 4.16, BeO 4.67, MgO 11.24, MnO 2.05, FeO 1.76, Al₂O₃ 0.15, SiO₂ 73.51, (Σ CaO, TiO₂ = 0.06) sum 100.33 (BeO determined by LA-ICP-MS). The empirical formula based on Si = 12 is K_0.87 Na_0.86 (Mg_1.57Mn_0.28Fe_0.24)_Σ2.09 (Be_1.83?Mg_1.17)_Σ3.00 [Si₁₂O₃₀], and the simplified formula can be given as K (□_0.5Na_0.5)₂ (Mg_0.8Mn_0.1Fe_0.1)₂ (Be_0.6?Mg_0.4)₃ [Si₁₂O₃₀]. Friedrichbeckeite is hexagonal, space-group P6/mcc, with a = 9.970(1), c = 14.130(3) Å, V = 1216.4(3) ų, and Z = 2. The strongest lines in the X-ray powder diffraction pattern are (d in Å / I _obs / hkl): 3.180 / 100 / 121, 2.885 / 70 / 114, 4.993 / 30 / 110, 4.081 / 30 / 112, 3.690 / 30 / 022. A single-crystal structure refinement (R1 = 3.62 %) confirmed that the structure is isotypic with milarite and related ^[12] C ^[9] B ₂ ^[6] A ₂ ^[4] T2₃ [^[4] T1₁₂O₃₀] compounds. The C-site is dominated by potassium, the B-site is almost half occupied by sodium, and the A-site is dominated by Mg. The site-scattering at the T2-site can be refined to a Be/(Be?+?Mg) value close to 0.61; the T1-site is occupied by Si. Micro-Raman spectroscopy reveals an increasing splitting of scattering bands around 550 cm^?1 for friedrichbeckeite. The mineral can be classified as an unbranched ring silicate or as a beryllo-magnesiosilicate. With respect to the end-member formula K (□0.5Na0.5)₂ Mg₂ Be₃ [Si₁₂O₃₀] friedrichbeckeite represents the Mg-dominant analogue of almarudite, milarite or oftedalite. The mineral and its paragenesis were formed during pyrometamorphic modifications of the silicate-rich xenoliths enclosed in Quaternary leucite-tephritic lava of the Bellerberg volcano. Holotype material of friedrichbeckeite has been deposited at the mineral collection of the Naturhistorisches Museum Wien, Austria. The mineral is named friedrichbeckeite in honour of the Austrian mineralogist and petrographer Friedrich Johann Karl Becke (1855–1931).     

Rare-earth elements as source indicators of Pan-African granites from Obudu Plateau,Southeastern Nigeria

The rare-earth element （REE） concentrations of representative granite samples from the southeast of the Obudu Plateau, Nigeria, were analyzed with an attempt to determine the signatures of their source, evolutionary history and tectonic setting. Results indicated that the granites have high absolute REE concentrations （190×10^-6-1191×10^-6; av.=549×10^-6） with the chondrite-normalized REE patterns characterized by steep negative slopes and prominent to slight or no negative Eu anomalies. All the samples are also characterized by high and variable concentrations of the LREE （151×10^-6-1169×10^-6; av.= 466×10^-6）, while the HREE show low abundance （4×10^-6-107×10^-6; av.=28×10^-6）. These are consistent with the variable levels of REE fractionation, and differentiation of the granites. This is further supported by the range of REE contents, the chondrite-normalized patterns and the ratios of LaN/YbN （2.30-343.37）, CeN/YbN （5.94-716.87）, LaN/SmN （3.14-11.68） and TbN/YbN （0.58-1.65）. The general parallelism of the REE patterns, suggest that all the granites were comagmatic in origin, while the high Eu/Eu＊ ratios （0.085-2.807; av.=0.9398） indicate high fo2 at the source. Similarly, irregular variations in LaN/YbN, CeN/YbN and Eu/Eu＊ ratios and REE abundances among the samples suggest behaviors that are related to mantle and crustal sources.     

构造物理化学的思路、研究和问题

构造物理化学是研究地壳物质受构造作用产生的物理和化学变化相互关联的领域。构造力可以分解为两部分一部分是均应力,指各向相等的应力,它叠加在原有压力之上,并且影响着各种化学反应的平衡,也是成岩、成矿和变质作用的影响因素。另一部分是差应力,固体中受外力作用普遍产生差应力,它引起地壳物质变形,产生各种构造形迹。构造物理化学特别关注构造作用产生或引起的压力、温度及其他的物理化学条件的变化,研究这些构造附加参量对各种化学平衡的影响,逐渐发展成为独立的学科研究领域。     

Oxidation and metal-insertion in molybdenite surfaces: evaluation of charge-transfer mechanisms and dynamics

Molybdenum disulfide (MoS₂), a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms in MoS₂ is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia.     

干旱区陆面过程参数改进对东亚区域气候影响的数值模拟

为了进一步检验裸土参数化的气候模拟性能,本文在文献[1,2]的基础上,利用NCEP再分析资料和Xie等全球降水资料与CCM3模拟结果进行了对比。结果表明：加入裸土参数化方案的CCM3能较好地再现冬季东亚和中国地区区域气候的主要特征,模式较原CCM3能更好地模拟地表温度和东亚及中国西北地区的降水,对东亚季风环流的模拟也较接近实际。同时,该方案在CCM3中的加入改进了青藏高原冬季降雪带及夏季高原东南部降水中心的模拟,提高了模式对高原冬夏季降水的模拟能力,从而再次说明利用观测资料对模式参数修正及参数化方法的改进是提高数值模式模拟能力的一个重要途径。     

不同土壤湿度条件下绿洲边界层特征的敏感性试验

应用NCAR的非静力平衡中尺度数值模式MM5V3．6,设计了三种不同土壤湿度对金塔绿洲边界层的特征影响的敏感性试验。结果表明：土壤灌溉后地表温度和气温升温率较灌溉前有所减小。土壤湿度越大,绿洲温度越低,绿洲的“冷岛效应”越显著。绿洲灌溉后地面感热通量较灌溉前偏低,潜热通量比灌溉前高;土壤湿度越大,这种差异越显著。土壤湿度为0．35时,绿洲能够很好地表现绿洲特性,维持其自身的发展。绿洲边界层高度在灌溉前后有很大的变化。随着土壤湿度的增加,绿洲的边界层高度逐渐降低。这种较低的边界层对绿洲起到了保护作用,它将绿洲的能量与水分保存任较低的边界层中,促进了绿洲的进一步维持和发展。     

Monthly prediction of rainfall over India and its homogeneous zones during monsoon season: a supervised principal component regression approach on general circulation model products

A supervised principal component regression (SPCR) technique has been employed on general circulation model (GCM) products for developing a monthly scale deterministic forecast of summer monsoon rainfall (June–July–August–September) for different homogeneous zones and India as a whole. The time series of the monthly observed rainfall as the predictand variable has been used from India Meteorological Department gridded (1°?×?1°) rainfall data. Lead 0 (forecast initialized in the same month) monthly products from GCMs are used as predictors. The sources of these GCMs are International Research Institute for Climate and Society, Columbia University, National Center for Environmental Prediction, and Japan Agency for Marine Earth Science and Technology. The performance of SPCR technique is judged against simple ensemble mean of GCMs (EM) and it is found that over almost all the zones the SPCR model gives better skill than EM in June, August, and September months of monsoon. The SPCR technique is able to capture the year to year observed rainfall variability in terms of sign as well as the magnitude. The independent forecasts of 2007 and 2008 are also analyzed for different monsoon months (Jun–Sep) in homogeneous zones and country. Here, 1982–2006 have been considered as development year or training period. Results of the study suggest that the SPCR model is able to catch the observational rainfall over India as a whole in June, August, and September in 2007 and June, July, and August in 2008.