Geochemistry of organic matter and elements of black shale during weathering in Northern Guizhou,Southwestern China: Their mobilization and inter-connection

Different from previous studies on effect of weathering upon geochemical variation along a single weathered profile, this paper provides a new methodology validated by comparing a weathered outcrop samples and their stratigraphic counterpart un-weathered core samples in a nearby shallow borehole. This outcrop and borehole penetrated the Ordovician-Silurian Wufeng–Longmaxi shales, located in the same anticline structure in the northern part of Guizhou Province, Southern China. The mineral composition, major, trace and rare earth elements (REEs) composition and Rock-Eval parameters of outcrop and core samples were analyzed and compared. Organic matter (OM) was observed in the microscope and extracted for elements analysis. The results show that short-term weathering still has significant influence on OM, mineral and elemental composition of black shales. The elements composition shows the outcrop profile was moderately weathered. The REEs compositions do not alter much during weathering process and the REEs composition and their relative ratios still are valid for rock origin determination. The OM, mainly composed by graptolite and bitumen, even entering the highly-over thermal maturity, is still sensitive to the weathering with a systematic loss 30–50% of TOC along the outcrop profile, which suggests that the OM consumption is predominantly controlled by weathering duration and the distance from the weathering surface. In turn, OM has significant influence on the trace elements transportation behavior during weathering. Some trace elements associated with the OM such as V, Cr, Th, U, Ni and Co, change significantly in their absolute concentration during weathering, but their relative ratios do not necessarily change too much and might be still reliable proxies for paleo-environmental determination. The mobility of shale minerals during weathering is in the following order: plagioclase?>?potassium feldspar and dolomite >pyrite and OM. Short-term weathering can also result in considerable transportation of elements and significant variation of minerals content in black shale, which may pose potentially high environmental and engineering risk in the regions rich in black shale.     

瑞安市基础控制网改造与原有控制网精度分析

通过瑞安市基础控制网的改造实践,对各地控制网改造的方法进行了探讨,并对原有测绘成果转换到新坐标基准中进行了分析、探讨.     

煤中微量元素分布特征初步研究

采自我国不同聚煤区的不同时代的89件煤样品,用中子活化分析法(INAA)分别测定了29种微量元素。据统计分析结果表明:(1)绝大多数微量元素的平均值高于世界的平均值,含量范围也较美国宽。我国各聚煤区不同时代间相比较,煤中大多数元素的平均含量和富集因数,从华南二叠纪至华北石炭—二叠纪到全国中-新生代逐渐降低。(2)中-新生代的煤中,元素间的相关性较好,华南二叠纪次之,而华北石炭—二叠纪的煤最差。(3)REE分布模式类型以中-新生代的煤最复杂;而华北石炭—二叠纪的煤较简单。     

Tracing infiltration and recharge using stable isotope in Taihang Mt., North China

The groundwater in headwater region is an important recharge source for the adjacent mountain-front plain. In order to reveal the relationship among precipitation, soil water and groundwater, from June to September in 2004, stable isotopes (deuterium and oxygen-18) in precipitation and soil waters at the depths of 10, 20, 30, 50, 70, 90, and 110 cm were analyzed at two sites covered by black locust (Robinia Pseudoacia L.) (Site A) and grass predominated by Themeda triandra (T. japonica (Willd.) Tanaka) and Bothriochloa ischaemum (B. ischaemum (L.) Keng) (Site B) in an experimental catchment at Taihang Mt., North China, respectively. The δ¹⁸O of precipitation in daily rain events shows large variations (−13.3 to −4.3‰) with a mean of 8.1‰. The δ¹⁸O and δ D of soil waters along profiles in two sites suggest that the influence of canopy cover was just up to 10 cm in top soil water. The soil water moved over the zero flux plane at 70 cm in-depth is expected to escape the evaporative effect at the end of September in both sites. The results show that the stable isotope, instead of tritium as tradition, can be used to trace the soil water behaviors based on the movement of isotopic peak along the vertical profiles in this semi-arid and semi-humid mountainous region. The infiltration depths of soil water in Taihang Mt. are 12 and 10 mm/day from June to September in 2004 in Site A and Site B, respectively. Tracing by stable isotope, recharge fluxes of soil water to local groundwater are of 3.8 and 3.2 mm/day in Site A and Site B, respectively. The results provide desirable information for assessment of local groundwater resources. An erratum to this article can be found at     

Study on Three-dimensional Visualization for Rock Structure

The visualization of rock structure is a very useful and important technique in many aspects in geological and geotechnical engineering such as investigating and evaluating the stability of a high rock slope. The conventional method used to visualize rock structure is limited to plotting the orientation of individual discontinuities by using the Schmidt stereographic net. The present paper shows a new technique to visualize the three-dimensional structure of rock masses. The fitting function for three-dimensional rock structure was established based on data gathered from field survey. Two fitting methods by which the discontinuous points gathered from a plane and discrete points from field survey were fitted respectively are suggested. The technique to visualize the three-dimensional structure of rock masses includes many aspects such as projection transformation, blanking and mutual cutting, are investigated. Based on the visualizing technique, the rock structure at the site of Xilupdu dam which is being built in Southwest of China was investigated.     

淮北矿区煤层气资源勘查潜力评价

淮北矿区地处华东腹地,煤层气资源丰富,具备大规模开发的前景。选用层次分析法与灰色聚类法评价方法,通过构建层次结构模型、计算指标权重、制定参数分类评价标准、运用灰色聚类法判别灰类、计算综合优度值,对矿区16个评价单元的山西组和下石盒子组煤层气资源潜力进行了评价,结果显示,淮北矿区山西组煤层气勘查潜力中等,下石盒子组勘查潜力较好。     

Detachment folding in a Lower Cambrian–Upper Permian karst reservoir: 3D model of the Yubei 3D area (eastern Markit Slope,Tarim Basin,Northwest China)

A three-dimensional (3D) structural modeling of the Lower Cambrian–Upper Permian Yubei 3D area was performed to understand its structural evolution. This model reproduces the present-day structure of the basin and comprises 11 horizons within Lower Cambrian to Upper Permian rocks. The analysis is based on 3D depth views and faults. The results image salt movements due to tectonics and/or burial. From these observations, this paper deduces that salt structures are correlated to the main faults and tectonic events. From the model analysis, we interpret the timing and geometry of Tarim Basin tectonics. The fault geometry can be resolved based on the strike of the fault, the morphology of hanging wall strata, and the stratigraphic distribution. Emphasis is placed on gypsum rock detachment, considering its movements during the Middle Caledonian event and decoupling effects during tectonic evolution. Moreover, we point to the structural control of the Paleozoic basement and the crustal architecture (Yubei 3D Zone) on the geometry of the Tarim Basin.     

Recharge source and hydrogeochemical evolution of shallow groundwater in a complex alluvial fan system,southwest of North China Plain

Many cities around the world are developed at alluvial fans. With economic and industrial development and increase in population, quality and quantity of groundwater are often damaged by over-exploitation in these areas. In order to realistically assess these groundwater resources and their sustainability, it is vital to understand the recharge sources and hydrogeochemical evolution of groundwater in alluvial fans. In March 2006, groundwater and surface water were sampled for major element analysis and stable isotope (oxygen-18 and deuterium) compositions in Xinxiang, which is located at a complex alluvial fan system composed of a mountainous area, Taihang Mt. alluvial fan and Yellow River alluvial fan. In the Taihang mountainous area, the groundwater was recharged by precipitation and was characterized by Ca–HCO₃ type water with depleted δ¹⁸O and δD (mean value of −8.8‰ δ¹⁸O). Along the flow path from the mountainous area to Taihang Mt. alluvial fan, the groundwater became geochemically complex (Ca–Na–Mg–HCO₃–Cl–SO₄ type), and heavier δ¹⁸O and δD were observed (around −8‰ δ¹⁸O). Before the surface water with mean δ¹⁸O of −8.7‰ recharged to groundwater, it underwent isotopic enrichment in Taihang Mt. alluvial fan. Chemical mixture and ion exchange are expected to be responsible for the chemical evolution of groundwater in Yellow River alluvial fan. Transferred water from the Yellow River is the main source of the groundwater in the Yellow River alluvial fan in the south of the study area, and stable isotopic compositions of the groundwater (mean value of −8.8‰ δ¹⁸O) were similar to those of transferred water (−8.9‰), increasing from the southern boundary of the study area to the distal end of the fan. The groundwater underwent chemical evolution from Ca–HCO₃, Na–HCO₃, to Na–SO₄. A conceptual model, integrating stiff diagrams, is used to describe the spatial variation of recharge sources, chemical evolution, and groundwater flow paths in the complex alluvial fan aquifer system.     

汶川科学钻探PDC取心钻头有限元分析

汶川地震断裂带科学钻探项目是在龙门山"北川-映秀"断裂及龙门山前缘安县-灌县断裂附近实施5口科学群钻,由于所实施的5个钻孔都位于地震断裂带上,地层十分松软破碎,普通取心钻进的取心率低、岩心扰动大。为解决该问题,设计并采用了一种超前式隔水防冲蚀PDC取心钻头,取得了良好的效果,提高了岩心采取率,并保证了岩心的原状性。论文通过UG建立的实体模型导入ANSYS Workbench下的CFX流场分析和Steady-Thermal稳定热分析模块,分析了该钻头的井底流场分布、大小以及钻头的冷却效果,并计算孔底有效排粉的最低泵量,以确定超前式隔水防冲蚀PDC取心钻头取心钻进时保证取心率和岩心原状性要求的最优泵量。     

Study on low‐strain integrity testing of pipe‐pile using the elastodynamic finite integration technique

This study focuses on the three‐dimensional (3‐D) characteristics of wave propagation in pipe‐pile using elastodynamic finite integration technique. First, a real 3‐D pile‐soil model in cylindrical coordinate system is presented. Then, the governing equations are established. With the boundary and initial conditions, the numerical solution is obtained. The accuracy and feasibility of the self‐written code are further verified via comparing with the measured data. Velocity histories at different angles of pile top and pile tip are illustrated, and the snapshots reflecting the 3‐D characteristics of wave propagation are given. It shows that the interferences of Rayleigh waves can confuse the result interpretation for pile integrity testing. The increase of hammer contact time can effectively mitigate the interferences, and the interferences of Rayleigh waves are weakest at an angle of 90° from where hammer hits. Besides, surrounding soil can partly mitigate the wave interferences. Copyright © 2012 John Wiley & Sons, Ltd.