Rare-earth elements in Luochuan loess section,Shaanxi province

TheΣ REE in loesses of different ages in the Luochuan section shows a narrow range of variation, indicating the homogeneity of loessic materials in chemical composition. The REEs in loess are concentrated mainly in silt-sized detrital minerals. Loesses and paleosols of different ages all are relatively enriched in rare-earth elements of the Ce family, and show similar REE distribution patterns. The fractionation among various REEs in the loess is different from that in morainic, marine and lacustrine sediments, but is similar to that in sand samples from deserts in Northwest China. The ratios of Ce/Ce* and Eu/Eu* reflect that the provenance of loessic materials and their accumulating area are all in an oxidation environment with weakly basic mediums under arid or semi-arid climate.     

秦巴山区重晶石与毒重石矿床成矿特征研究

秦巴山区按地质成矿特征可划分大巴山、平利、南秦岭三个区。重晶石与毒重石矿床分三条成矿带 :南带为毒重石矿带、北带与中带为重晶石矿带 ,成矿具有多期作用 ,含火山喷发、大陆边缘沉积、裂谷与脉体成矿叠加。本区找矿前景是乐观的。     

河南栾川地区铅锌矿床地质和硫同位素地球化学

河南栾川地区是我国著名斑岩钼矿集区,近年铅锌矿勘查取得重要进展,但对铅锌矿成因认识分歧颇多。研究表明,栾川地区铅锌矿产在燕山期斑岩钼矿床外围,矿区地层为中元古界官道口群和新元古界栾川群碳酸盐岩-碎屑岩沉积变质建造,地层中侵入有晋宁期辉长岩、正长岩和燕山期酸性斑岩,铅锌矿呈脉状或透镜状,发育3种类型:受燕山期斑岩与元古界钙质地层接触带控制的夕卡岩型铅锌矿、受北西西向层间断裂构造控制的脉状铅锌矿和受北东或近南北向张-张扭性断裂控制的脉状铅锌矿。铅锌矿石中硫化物δ~(34)S_(V-CDT)为近零的正值(骆驼山0.37‰～4.20‰、赤土店-0.32‰～8.30‰、百炉沟-1.20‰～10.90‰、冷水北沟0.70‰～12.10‰),岩浆来源硫特征明显;夕卡岩型铅锌硫化物的δ~(34)S_(V-CDT)与本地斑岩型钼矿石中硫化物的δ~(34)S_(V-CDT)(1.24‰～3.30‰)极为相近,脉状铅锌硫化物的δ~(34)S_(V-CDT)与斑岩型钼矿石中硫化物重合,但有地层中硫(δ~(34)S_(V-CDT)为12.43‰～18.63‰)的影响。总体上δ~(34)S_(黄铁矿)>δ~(34)S_(闪锌矿)>δ~(34)S_(方铅矿),指示矿石中主要硫化物矿物硫同位素分馏基本达到平衡,赤土店铅锌矿石中共生方铅矿与闪锌矿的硫同位素温度计指示硫化物矿物沉淀温度较高(388.29℃)。河南栾川地区铅锌矿主体应为受燕山期构造-岩浆作用控制的中高温热液铅锌矿床。     

陇县904地区混合岩型铀矿成矿特征的讨论

含铀混合岩大部分位于古陆隆起带边部、ＮＷ向花岗岩外接触带。深大断裂系统在成矿成岩中占有相当重要的地位。燕山期构造和岩浆活化，对原有的构造和矿化进行了强烈改造。在混合岩中发现了两种主要成矿类型，即铀一赤铁矿型和铀一碳酸盐型。     

A study of inclusions in fluorite from the Shuangjiangkou-Jiangjunmiao fluorite ore deposit in Hunan Province

The Shuangjiangkuo-Jiangjunmiao fluorite ore deposit occurs in Early Yenshanian granites in the fold system of south China. The average homogenization temperature of inclusions in fluorite is 250°C. The contents of CO₂ and CH₄ in the inclusions tend to increase from southeast to northwest as well as in the vertical direction. Liquid in the inclusions is composed mainly of CaO, F and Cl with minor SO ₄ ² . All this has contributed a lot to the formation of fluorite as well as to wall-rock alteration. This ore deposit is evidenced to be mesothermal in origin.     

The Influence of Weathering on the Engineering Properties of Dunites

Weathering processes cause important changes in the engineering properties of rocks. In this study, dunites in the Bursa region in western Turkey were investigated and the changes in engineering properties due to weathering were evaluated. The studies were initiated with field observations including measurement of the characteristics of discontinuities such as spacing, aperture, fill material, roughness, and Schmidt hammer rebound value. Subsequently, laboratory studies were conducted in two stages. The first stage comprised mineralogical, petrographic, and chemical analyses. The second stage included physicomechanical tests to determine specific gravity, unit weights, water absorption, effective porosity, uniaxial compressive strength, P-wave velocity, and slake-durability index. According to these evaluations, the changes in engineering properties were determined to be mostly related to serpentinization at every stage of weathering. The most suitable parameters for characterizing the degree of weathering of the studied dunites are loss-on-ignition values, specific gravity, unit weight, water absorption, and effective porosity.     

Limited Consequences of Seagrass Decline on Benthic Macrofauna and Associated Biotic Indicators

Marine phanerogams are ecosystem engineers, as their presence induces major environmental changes that impact on the benthic fauna. Consequently, modifications to the structure of benthic communities would be expected to be associated with seagrass decline. Since 2005, Zostera noltii seagrass beds in Arcachon Bay (France), the largest in Europe, have undergone a severe decline. Twelve stations distributed throughout the lagoon were sampled in 2002, and all were found to be densely planted at that time. Subsequently, the same stations were revisited in 2010 and seagrass cover had drastically decreased by that time. Based on benthic macrofauna, multidimensional scaling (MDS) analysis identified four groups. Years were separated. In 2002, two groups were distinct in relation to the water body, since in 2010 separation between the two other groups was related to seagrass occurrence. When looking at community structure and dominant species there were moderate differences within and between years, independent of seagrass decline. Seagrass loss did not drastically modify the species composition as they were preserved in the remaining seagrass patches. However, there was a drop in macrofauna abundance in unvegetated muddy compared with abundance in the remaining seagrass areas. Epifauna was particularly affected by seagrass decline. Among biotic indicators based on macrofauna, multivariate indicator MISS (Macrobenthic Index in Sheltered Systems) was in agreement with the similarity of macrofauna structure among groups, while other tested indicators performed badly in relation to seagrass occurrence. However, no index detected seagrass loss, highlighting the necessity of maintaining a separate survey on seagrass cover.     

综合处理办法在城市复杂地段桥桩施工中的应用

在北京市德内大街桥桩施工过程中,不仅遇到交通拥堵．场地狭小．地上地下障碍物等多种不利条件．而且在拟施工的桩位处遇到大量原有河道的加固材料,物品种类之多、数量之大、埋深之厚,实属罕见,施工条件极差、施工难度极高,施工单位最终通过采取多种办法、措施解决了这些难题,圆满的完成了桥桩施工任务。本人认为在旧城复杂地段施工时,综合处理措施具有很大发展空间,值得深入研究发展,在旧城改造的类似工程中具有一定借鉴作用。