沿海表层沉积物中重金属的有效结合态

以浙江沿海表层沉积物为研究对象,系统地研究了重金属有效结合态与沉积环境、矿物组成和人为排放等环境因素之间的相互关系.结果表明:沿海表层沉积物中重金属的积累数量,呈现出潮汐河口沉积物>沿海沉积物>强潮汐河口沉积物的趋势,这反映了不同沉积类型对重金属富集作用的差异;重金属的有效结合态,总体上以铁锰氧化物结合态>碳酸盐结合态>硫化物及有机结合态>可交换态的顺序存在,但是不同的重金属或同种重金属在不同的采点,主要有效结合态的比例存在明显的差异,这不仅与重金属的地球化学性质、沉积环境和沉积物中的粘土矿物组成有关,更受到重金属污染物的人为排放量的影响.     

地面物探在岩溶地基工程勘察中的应用——以桂林某花园综合楼为例

岩溶地区工程建筑地基的地质情况比较复杂,存在土洞、软土等工程隐患。常规工程勘察手段,由于其自身的局限性,很难一一查清这些隐患的分布特征。地面物探是一种较为省时省力的工程辅助勘探方法。但物探方法有多种,在选用时,必须根据场地条件、探测目标、方法性能及工作成本等来综合考虑,选择适用的方法(或方法组合) ,才有可能取得令人满意的探测效果。桂林某花园综合楼地基主要以红粘土为主,软土、土洞发育,红粘土之下,桂林组灰岩表面起伏强烈,溶洞发育。根据场地地质特征及基坑开挖特点,本勘察采取浅层地震折射、反射波法,并配合高密度电阻率测量,较好地查明了场地软土和土洞的分布位置,为综合楼的地基处理提供了可靠的地质依据。      

长江流域河水和悬浮物的锂同位素地球化学研究

深入理解流域侵蚀过程中的锂同位素分馏对于运用锂同位素来示踪化学循环和气候变化是十分必要的。研究集中在长江干流和主要支流的水体和悬浮物的锂及锂同位素组成。长江流域水体的锂及锂同位素组成（δ⁷Li）分别为150~4 570 nmol/L和+7.6‰~+28.1‰,两者沿上游至下游的变化趋势相反。悬浮物锂同位素组成（δ⁷Li）变化比较稳定,分别为41~92 μg/g和-4.7‰~+0.7‰,而且总是低于相应水体的锂同位素组成。悬浮物和流体之间的锂同位素分馏系数在0.977和0.992之间,与悬浮物的量及组成存在明显相关性,反映了粘土矿物的吸附和化学风化的程度。锂含量与锂同位素组成之间良好的负相关性表明流域水体的锂来自2个端元混合：其一可能是蒸发盐岩,并伴有深部热泉水;其二可能是硅酸岩。     

长江口泥沙的来源分析与数量计算的研究

本文根据地学原理，建立了长江口泥沙的来源分析与数量计算的模式。定量分析了长江口泥沙来源，计算了泥沙的数量。通过验证表明沙量的计算值与验证值两者十分吻合。     

Shear strength characteristics of Irbid clayey soil mixed with iron filling and iron filling–cement mixture

Iron filling and iron filling–cement mixture were used to improve the shear strength characteristics of Irbid clayey soil. For this purpose, five types of Irbid clay soils were obtained and mixed with iron filling and iron filling–cement mixture at different percentages. Two sets of prepared samples were mixed with the admixture. The first set was prepared by mixing the soil samples with iron filling alone at 2.5, 5.0, 7.5, and 10% by dry weight of the soil. The second set was prepared by mixing with iron filling–cement mixture at equal ratio of the same percentages of the first set. An unconfined compression test was performed in this study to measure the shear strength properties of the soils. The test results showed that the increase in the percentages of the iron filling and iron filling–cement mixture up to 10% will result in increasing the maximum dry density of the soil and increase the unconfined compressive strength and the secant of modulus of elasticity of the clayey soil. Also, the addition of iron filling–cement mixture increased the unconfined compressive strength and secant modulus of elasticity of the clayey soil higher than the addition of iron filling alone.     

Microstructures and their implications for faulting processes –Insights from DGLab core samples from the Gulf of Corinth

We have examined microstructures, mineralogical composition, geochemical alteration, and texture of four selected fault rock samples from the Deep Geodynamical Laboratory (DGLab) Gulf of Corinth project using optical microscopy, cathodoluminescence microscopy (CL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and synchrotron X-ray diffraction measurements. The fault core is composed of red and gray clayey gouge material and surrounded by a damage zone of brecciated limestones. Pressure solution features, calcite veins and calcite clasts in the breccia and gouge material attest the presence of paleo-fluids and fluid-driven mass transfer during deformation. Differences in CL-colors between the matrix and calcite vein cement and inside the vein cement suggest repeated infiltration of fluids with different composition from various sources (formation water and meteoric water). Twin lamellae densities estimated in calcite veins are used as paleo-piezometer. The deduced differential stress is ∼140 ± 70 MPa for the older vein generation and appears to be higher than stress for the youngest veins (45 ± 23 MPa). In spite of the relatively small clay content in both samples, newly formed clay minerals have been observed in gray as well as red clayey gouge material. Differences between gray and red clay gouge material are found in fault rock composition, porosity and clay fabric. The proportion of chlorite in the red gouge is significantly less than that in the gray gouge whereas the initial porosity is significantly higher than in the gray gouge material. The detection of a well-oriented clay fabric in red clay gouge samples is unique in comparison to other major fault zones.     

Compaction of diagenetically altered mudstones – Part 2: Implications for pore pressure estimation

Diagenetically altered mudstones compact mechanically and chemically. Consequently, their normal compaction trends depend upon their temperature history as well as on the maximum effective stress they have experienced. A further complication is that mudstones are commonly overpressured where clay diagenesis occurs, preventing direct observation of the hydrostatic normal compaction trend. A popular way to estimate pore pressure in these circumstances is to calculate the sonic normal compaction trend in a well with a known pressure–depth profile by applying Eaton's method in reverse, and then to estimate pore pressure in offset wells using Eaton's method conventionally. We tested this procedure for Cretaceous mudstones at Haltenbanken. The results were inconsistent because the sonic log responds differently to disequilibrium compaction overpressure and unloading overpressure, and their relative contributions vary across the basin. In theory, a two-step method using the density and sonic logs could estimate the contributions to overpressure from disequilibrium compaction and unloading. The normal compaction trend for density should be the normal compaction trend at the maximum effective stress the mudstones have experienced, not at hydrostatic effective stress. We advocate the Budge-Fudge approach as a starting point for pore pressure estimation in diagenetically altered mudstones, a two-step method that requires geological input to help estimate the overpressure contribution from disequilibrium compaction. In principle, the Budge-Fudge approach could be used to estimate the normal compaction trend for mudstones at the maximum effective stress they have experienced, and so form the basis of the full two-step method through the use of offset wells. Our initial efforts to implement the full two-step method in this way at Haltenbanken produced inconsistent results with fluctuations in estimated pore pressure reflecting some of the fluctuations in the density logs. We suspect that variations in the mineralogical composition of the mudstones are responsible.     

Impact of high water pressure on oil generation and maturation in Kimmeridge Clay and Monterey source rocks: Implications for petroleum retention and gas generation in shale gas systems

This study presents results for pyrolysis experiments conducted on immature Type II and IIs source rocks (Kimmeridge Clay, Dorset UK, and Monterey shale, California, USA respectively) to investigate the impact of high water pressure on source rock maturation and petroleum (oil and gas) generation. Using a 25 ml Hastalloy vessel, the source rocks were pyrolysed at low (180 and 245 bar) and high (500, 700 and 900 bar) water pressure hydrous conditions at 350 °C and 380 °C for between 6 and 24 h. For the Kimmeridge Clay (KCF) at 350 °C, Rock Eval HI of the pyrolysed rock residues were 30–44 mg/g higher between 6 h and 12 h at 900 bar than at 180 bar. Also at 350 °C for 24 h the gas, expelled oil, and vitrinite reflectance (VR) were all reduced by 46%, 61%, and 0.25% Ro respectively at 900 bar compared with 180 bar. At 380 °C the retardation effect of pressure on the KCF was less significant for gas generation. However, oil yield and VR were reduced by 47% and 0.3% Ro respectively, and Rock Eval HI was also higher by 28 mg/g at 900 bar compared with 245 bar at 12 h. The huge decrease in gas and oil yields and the VR observed with an increase in water pressure at 350 °C for 24 h and 380 °C for 12 h (maximum oil generation) were also observed for all other times and temperatures investigated for the KCF and the Monterey shale. This shows that high water pressure significantly retards petroleum generation and source rock maturation. The retardation of oil generation and expulsion resulted in significant amounts of bitumen and oil being retained in the rocks pyrolysed at high pressures, suggesting that pressure is a possible mechanism for retaining petroleum (bitumen and oil) in source rocks. This retention of petroleum within the rock provides a mechanism for oil-prone source rocks to become potential shale gas reservoirs. The implications from this study are that in geological basins, pressure, temperature and time will all exert significant control on the extent of petroleum generation and source rock maturation for Type II source rocks, and that the petroleum retained in the rocks at high pressures may explain in part why oil-prone source rocks contain the most prolific shale gas resources.     

Organic geochemical study of the Upper Kimmeridge Clay of the Dorset type area

Results are presented from an organic geochemical investigation of a suite of rock samples taken from the Upper Kimmeridge Clay near Kimmeridge, Dorset. All samples contain immature organic matter of marine origin, although one horizon, the Whitestone Band, contains an additional secondary input of partially biodegraded mature hydrocarbons, due to an oil seepage of unknown origin. With the exception of increased relative abundances of 4-methylsteroidal hydrocarbons in the more organic-rich samples, the immature molecular distributions are very similar, suggesting a consistent source of organic matter. The results are in agreement with the palaeoenvironmental model proposed by Tyson et al. (1979) for the deposition of the Kimmeridge Clay, where the different lithologies are controlled by a fluctuating oxic/anoxic boundary, with only the organic-poor mudstones being deposited in relatively oxygenated waters.     

A solution around a backfilled cavity in a low‐permeability poroelastic medium with application in in situ heating tests

Thermo‐hydro‐mechanical responses around a cylindrical cavity drilled or excavated in a low‐permeability formation are studied when the cavity is subjected to a time‐dependent thermal loading. The cavity is considered backfilled after it is supported by casing or lining. Solutions of temperature, pore water pressure, stress, and displacement responses are analytically formulated based on Biot's consolidation theory with the assumption that the backfilling material, supporting material, and surrounding low‐permeability formation are poroelastic media. The solution is expressed in Laplace space, and numerical inversion techniques are used to find field variables in the real‐time domain. After the solution is verified with the numerical results, it is applied in a large‐scale in situ heating test – PRACLAY heating test – for a predictive reference calculation and an extensive parametric study. Another medium‐scale in situ heating test – ATLAS III heating test – is also analyzed using the solution, which provides reasonable agreement with measurements. The new analytical solution proves to be a convenient tool for a good understanding of the resulting coupled thermo‐hydro‐mechanical behavior and is therefore valuable for the interpretation of measured data in engineering practices and for a rational design of potential radioactive waste repositories. Copyright © 2016 John Wiley & Sons, Ltd.