松辽盆地徐家围子断陷安达次洼火山岩气藏的主要特征

徐家围子断陷是由徐西、徐中和徐东3条断裂控制的复式箕状断陷,安达次洼位于该断陷北部,火山岩岩性复杂,储层发育受控于多种因素.综合地震、地质、钻井、测井、岩心、测试及岩屑、气-水的物理化学资料,对该区营城组火山岩气藏的构造、储层和成藏特征进行了系统的研究.火山岩气藏的流体分布总体上遵循重力分异原则,以上气下水为主,说明构造位置对含气性具有一定的控制作用.火山岩相带展布、各井的试气成果及测井资料表明：本区营城组气藏没有统一的气-水界面,区内预测火山岩地层连续分布,储层错叠分布,横向连通性差,含气范围覆盖全区,气藏主要受岩性和岩相控制,为构造-岩性气藏.     

The relations between land use and karst rocky desertification in a typical karst area,China

Karst rocky desertification (KRD) is one major type of desertification which is under irrational human impact on the vulnerable eco-geo-environment. In this study, Zhudong fengcong rocky desertification landscape was selected to investigate the land use types distribution law in different rock types and the KRD land in different land use types. KRD data was determined by user–computer interactive interpreting method from Aster images in 2004, according to the exposed ratio of rock, the coverage of vegetation and soil in 0.2 km² unit, integrating with land utilizing present situation map, hydrogeology map, relief map, vegetation map, soil distribution map, as well as the practical investigation and the population census datum in 2002. Results showed that the occurrence ratio of KRD land is different in land use types and rocky assemblages obviously; land cover has a strong impact upon KRD. The sloping cropland distributed in homogenous limestone has a higher occurrence ratio of light KRD, secondly, is in the limestone interbedded with clastic rock. Light KRD land was dominated by shrubland, and sloping cropland accounts for 11.67% of it, moderate KRD land was dominated by moderate coverage grass slopes, strong and extremely strong KRD was dominated by rocky dry land which is difficult to use.     

地面高精度磁测在煤田勘探中的应用

针对陕北煤田勘探中煤层自燃区自燃边界的确定,采用了地面高精度磁测的方法技术,通过求△T垂向一阶导数,来突出异常体边部影响,提高相邻异常体异常迭加的分辨率,认为该方法是解决煤层自燃区（火烧区边界）的一种行之有效的方法。     

Baiyun Movement: A Significant Tectonic Event on Oligocene/Miocene Boundary in the Northern South China Sea and Its Regional Implications

A significant geologic event occurred on the Oligocene/Miocene boundary at 23.8 Ma in the northern South China Sea,which is named the Baiyun (白云) movement in this article.This event strongly affected not only the South China Sea,but also East Asia.After the Balyun event,the ridge of seafloor spreading of the South China Sea Jumped southward and rotated counterclockwise,and a strong subsidence occurred in the Baiyun sag of the Pearl River Month basin.The shelf break shifted suddenly from the south to the north of the Baiyun sag,and the deposition environment in this sag changed from continental shelf with neritic deposition to continental slope with deep-water deposition.Sediment geochemistry study indicated that the Balyun event played a key role in the rapid change of sediment provenance for the Pearl River Mouth basin.Between 32 and 23.8 Ma,the source of sediments was mainly from the granites in South China,while after 23.8 Ma some sediments might have come from the eastern Himalaya,as the Pearl River drainage extended westward after the uplift of Tibet since that time.The Baiyun event led to a great change in the drainage framework of the paleoPearl River,sediment types and the depositional environments in the Pearl River Mouth basin,and relative sea level of the northern South China Sea,as well as sedimentation and hydrocarbon accumulation in the ares.     

新疆吐哈盆地中、下侏罗统含煤岩系层序地层及古地理

在吐哈盆地中、下侏罗统含煤岩系层序地层分析的基础上,对聚煤期古地理特征及其与聚煤作用的关系进行了研究。结果表明,吐哈盆地中、下侏罗统含煤岩系形成于河流-三角洲-湖泊沉积体系,其中共发育4个三级层序,分别对应于八道湾组、三工河组、西山窑组一、二段和三、四段。吐哈盆地从层序Ⅰ到层序Ⅳ,先后经历了沼泽（层序Ⅰ）-湖泊（层序Ⅱ）-沼泽（层序Ⅲ）-湖泊（层序Ⅳ）过程。在对应于最大湖泛面的湖侵体系域末期和高位体系域早期,较快的可容空间增加速率与泥炭堆积速率相平衡,从而有利于厚煤层的堆积。煤层厚度、碳质泥岩厚度与砂砾岩含量呈负相关关系,即砂砾岩含量越少,煤和碳质泥岩厚度越大;地层厚度300～500 m（层序Ⅰ）和400～550m之间（层序Ⅲ）时,煤层厚度最大,说明有利于煤和碳质泥岩聚集的环境是沉降速率中等、陆源碎屑供给相对较少的三角洲间湾、湖湾以及下三角洲平原环境,层序Ⅰ和层序Ⅲ的聚煤中心如艾维尔沟、柯尔碱、桃树园、七泉湖、柯柯亚、鄯善、艾丁湖、沙尔湖、大南湖和三道岭等均属于这类环境。     

A general polynomial solution to convection–dispersion equation using boundary layer theory

A number of models have been established to simulate the behaviour of solute transport due to chemical pollution, both in croplands and groundwater systems. An approximate polynomial solution to convection–dispersion equation (CDE) based on boundary layer theory has been verified for the use to describe solute transport in semi-infinite systems such as soil column. However, previous studies have only proposed low order polynomial solutions such as parabolic and cubic polynomials. This paper presents a general polynomial boundary layer solution to CDE. Comparison with exact solution suggests the prediction accuracy of the boundary layer solution varies with the order of polynomial expression and soil transport parameters. The results show that prediction accuracy increases with increasing order up to parabolic or cubic polynomial function and with no distinct relationship between accuracy and order for higher order polynomials (\(n\geqslant 3\)). Comparison of two critical solute transport parameters (i.e., dispersion coefficient and retardation factor), estimated by the boundary layer solution and obtained by CXTFIT curve-fitting, shows a good agreement. The study shows that the general solution can determine the appropriate orders of polynomials for approximate CDE solutions that best describe solute concentration profiles and optimal solute transport parameters. Furthermore, the general polynomial solution to CDE provides a simple approach to solute transport problems, a criterion for choosing the right orders of polynomials for soils with different transport parameters. It is also a potential approach for estimating solute transport parameters of soils in the field.     

Groundwater circulation and hydrogeochemical evolution in Nomhon of Qaidam Basin,northwest China

In this study, analysis of hydrogeological conditions, as well as hydrochemistry and isotopic tools were used to get an insight into the processes controlling mineralization, recharge conditions, and flow pattern of groundwater in a typical arid alluvial-lacustrine plain in Qaidam Basin, northwest China. Analysis of the dissolved constituents reveals that groundwater evolves from fresh water (TDS =300–1000 mg/l) to saline water (TDS ≥5000 mg/l) along the flow paths, with the water type transiting from HCO ₃?Cl–Na ?Mg to HCO ₃?Cl–Na, and eventually to Cl–Na. Groundwater chemical evolution is mainly controlled by water–rock interaction and the evaporation–crystallization process. Deuterium and oxygen-18 isotopes in groundwater samples indicate that the recharge of groundwater is happened by meteoric water and glacier melt-water in the Kunlun Mountains, and in three different recharge conditions. Groundwater ages, estimated by the radiogenic (³H and ¹⁴C) isotope data, range from present to Holocene (～28 ka). Based on groundwater residence time, hydrogeochemical characteristics, field investigation, and geological structure distribution, a conceptual groundwater flow pattern affected by uplift structure is proposed, indicating that shallow phreatic water is blocked by the uplift structure and the flow direction is turned to the northwest, while high pressure artesian water is formed in the confined aquifers at the axis of the uplift structure.     

Hydromechanical modelling of the SEALEX experiments

Numerical modelling of coupled physical processes in bentonite–sand mixtures under the geological conditions is significant for designing and constructing sealing systems in deep underground repositories for highly radioactive nuclear waste. Within the framework of DECOVALEX 2015, Task A, this work presents the model validation of OpenGeoSys by numerical modelling of coupled hydromechanical (HM) processes in bentonite–sand mixtures. Parameters used in the HM model were determined by modelling the laboratory tests of the sealing experiment (SEALEX). Afterwards these parameters were applied for the modelling of a small-scale mock-up test considering the influence of technological gap and incidental fail of the seal in the sealing system. In order to investigate the availability of employing these HM parameters and numerical models directly to field predictions, the modelling results and measured data of an in situ SEALEX experiment were analysed comparatively. The modelling results reproduced well the main features in HM behaviour of the compacted bentonite–sand mixture, which denotes that the adopted HM models and parameters are adequate for describing the HM processes in the sealing system. It is necessary to take the elastoplastic behaviour and evolution of the permeability of bentonite–sand mixtures into account when using the adopted models to reproduce the HM processes of a sealing system.     

Application of inverse modeling in a study of the hydrogeochemical evolution of karst groundwater in the Jinci Spring region,northern China

This study explores the hydrogeochemical evolution of karst groundwater in the Jinci Spring region, Shanxi Province, northern China. During 2015, karst groundwater samples collected from 24 sampling points along several profiles that follow the groundwater flow direction were subjected to hydrochemical analysis. Reaction paths and mineral phases for the hydrogeochemical modeling were determined based on the analysis results and in conjunction with the regional geology and hydrogeology. The PHREEQC hydrogeochemical modeling software was used to perform mass balance and reaction path modeling of the hydrogeochemical evolution of the spring region. The modeling results showed that from the recharge area through the runoff area to the drainage area, the hydrogeochemical processes occurring in the karst water vary widely between the northeastern, central, and southwestern parts of the spring region, and across the piedmont discharge area. Additionally, hydrodynamic fields and geological structures were found to have significant control over the hydrogeochemical reactions occurring within the spring region’s karst groundwater.     

Effects of crack inclination on shear failure of brittle geomaterials under compression

A micromechanics-based approach is proposed to predict the shear failure of brittle rocks under compression. Formulation of this approach is based on an improved wing microcrack model, the Mohr-Coulomb failure criterion, and a micro-macro damage model. The improved wing microcrack model considers the effects of crack inclination angle on mechanical behaviors of rocks. The micro-macro damage model describes the relation between crack growth and axial strain. Furthermore, comparing experimental and theoretical relations between crack initiation stress and confining pressure, model parameters (i.e., μ, a, β, and φ) hardly measured by test are solved. Effects of crack inclination angle, crack size, and friction coefficient on stress-strain relation, compressive strength, internal friction angle, cohesion, shear failure plane angle, and shear strength are discussed in details. A most disadvantaged crack angle is found, which is corresponding to the smallest compressive strength, cohesion, internal friction angle, and shear strength of rocks. Rationality of the theoretical results is verified by the published experimental results. This approach provides a theoretical prediction for effects of microcrack geometry on macroscopic shear properties in brittle rocks under compression.