粤东南燕山期热隆伸展及其古水热系统——以恩平-新丰拆离断层为例

粤东南地区广泛发育燕山期NE-SW走向的拆离断层系统。文章对恩平-新丰拆离断层进行了野外地质调查和室内测试分析,重点研究了拆离断层之下韧性剪切带中的糜棱岩和拆离断层上盘与高角度脆性正断层伴生的硅化岩。初步认为,研究区热隆伸展构造于燕山早期开始形成,糜棱岩的变形温度在350℃左右,硅化岩内石英中气液包裹体的均一温度在155℃~326℃,盐度在2.74%~21.61% NaCl_eqv,平均盐度为11.17% NaCl_eqv,古热液流体沸腾时的温度在235℃~241℃,激光拉曼光谱分析结果表明,含硅热液的成分为富含Si、CO₂的NaCl-H₂O溶液。硅化岩流体包裹体的H-O稳定同位素组成表明古水热流体为岩浆水与大气降水混合作用的产物。沿着正断层分布的硅化岩可能是燕山期古水热型地热能的重要标志。燕山期热隆伸展构造系统及其深层与浅层相结合的古水热系统对认识现代地热能的类型、成因及其分布规律有一定的意义。     

极地深部冰层取心钻探孔壁水压致裂研究

为了维护极地深部冰层取心钻探工作中钻孔的稳定,避免孔内事故的发生,冰层孔壁的水压致裂问题是亟待解决的重要科学问题之一。本文在深入分析国内外冰层钻探资料的基础上,结合冰盖动力学相关理论,计算得出了钻孔所在区域冰层的密度、温度及内部应力随深度的变化规律。在此基础上,结合油气资源勘探水力压裂技术与冰层钻进钻井液等相关理论,建立了合理的孔壁压差计算方法,深入探讨了适用于深部冰层钻探孔壁水压致裂机理。研制了冰层钻孔水压致裂模拟实验装置,可分析研究不同围压条件下冰样的脆性变形机理。结合我国Dome A深冰心钻探工程实际,提出钻孔可能发生水压致裂的深度区域及孔壁所需的起始裂纹长度判定,以期为后续的安全高效冰层钻进提供重要的理论依据。     

泾阳南塬蒋刘4#滑坡特征及成因机制

2016年3月6日,泾阳南塬蒋刘村发生了约2×104 m3的小型黄土滑坡。滑坡发生后,在对滑坡现场进行详细的地质调查基础上,结合无人机航测和三维激光扫描综合手段,对滑坡的基本特征及成因机理进行了初步分析。结果表明:长期引水灌溉是滑坡发生的基本条件;坡脚滞水软化作用、与灌溉渠较短的渗透距离、坡脚冻结黄土春季解冻是导致滑体发生的直接原因;底部饱和泥化黄土的铺垫及导流作用,是导致其滑程较远的根本原因。该类滑坡近几年来发生频率较高,为泾阳南塬滑坡演化后期的主要发生类型,具有一定的特殊性,值得深入研究。     

高分遥感技术在西昆仑大红柳滩-俘虏沟地区地质找矿中的应用

在西昆仑大红柳滩-俘虏沟地区,以WorldView-2高空间分辨率数据为主要信息源,在标准影像图制作基础上,针对性地进行图像增强处理,突出相关控矿要素和矿化信息,开展地质矿产遥感解译;利用ASTER数据开展矿化蚀变有关的遥感异常信息提取,配合适量的野外调查验证,发现了4种极具找矿前景的矿化带类型：①大红柳滩（含稀有金属）花岗伟晶岩带1处;②大红柳滩层控型铁多金属矿化带1处;③俘虏沟燕山期花岗岩有关热液脉型铁、铅、银、铜矿化区1处;④俘虏沟层控型含铜铅锌银的菱铁-赤铁矿矿化带4处;通过遥感综合分析,圈定遥感找矿靶区11处,其中A级遥感找矿靶区5处、B级遥感找矿靶区3处、C级遥感找矿靶区3处,为后续区域地质矿产调查项目规划部署和矿产资源勘查评价提供依据。因此,高分遥感技术在西昆仑地区矿产地质综合调查中作用显著,可实现找矿工作的快速突破,值得在相同或类似区域进一步推广应用。     

水射流破碎南海含水合物沉积物数值模拟研究

为研究高压水射流切割、破碎南海天然气水合物储层的过程,采用著名的LS—DYNA显示动力分析有限元程序,对淹没状态下,水射流破碎海底含水合物沉积物过程进行数值模拟研究,研究了不同射流速度对高压水射流作用下含水合物沉积物破碎效果的影响规律。随着射流速度的增大,冲蚀深度逐渐增大,两者呈线性递增关系。含水合物沉积物冲蚀体积是轴向冲蚀与径向冲蚀共同作用的结果,射流速度越大,对含水合物沉积物的轴向与径向冲蚀作用增强,加大了含水合物沉积物冲蚀体积递增速率。     

大兴安岭呼中钼多金属矿床成矿流体特征及成矿机制

大兴安岭呼中镇钼多金属矿床产于早白垩世碎裂花岗岩中,矿体形态似层状、脉状或透镜状。成矿阶段分为辉钼矿阶段、铜铅锌阶段、方解石阶段等3个阶段。本矿床中的包裹体主要有气液H_2O包裹体、气相H_2O包裹体、含子矿物H_2O包裹体,CO_2包裹体、CO_2-H_2O包裹体等五大类。辉钼矿阶段均一温度为209.2℃413.4℃,盐度ω(NaCleq)为0.53%16.53%,平均值7.3%,属中低盐度,成矿压力在53.3 68.5 MPa,相应的成矿深度为2 052 2 807 m;铜铅锌阶段为191.5℃351.0℃,盐度ω(NaCleq)为0.88%34.24%,平均值3.96%,属低盐度;方解石阶段207.2℃233.5℃,盐度ω(NaCleq)为3.55%4.18%,平均值3.77%,为低盐度。从辉钼矿阶段到铜铅锌阶段再到方解石阶段,温度及盐度逐渐降低。辉钼矿成矿压力在53.3 72.9 MPa,成矿深度为2 052 2 807 m。成矿过程中发生了CO_2-H_2O不混溶作用,这是导致辉钼矿沉淀的主要机制。矿床类型属中低温浅成热液型矿床。     

华北克拉通北缘东段“开原岩群”的解体及重新认识

根据近年来的同位素年代学资料,对分布于辽北地区的一套构造变质岩系（"开原岩群"或"清河镇岩群"）进行了重新认识和划分,并将其重新定义为清河构造混杂岩,由中太古代、新太古代、中元古代、新元古代、二叠纪等不同时代、不同构造环境的地质体组成.其中,中太古代、新太古代、中元古代岩石来自华北克拉通,而新元古代、二叠纪岩石则来自兴蒙造山带.将原沈家堡子岩组重新划分为新太古代变质表壳岩和中-新太古代变质深成岩,原板石沟岩组（或芦家堡子岩组）厘定为中元古代石门岩组,原照北山岩组重新划分为新元古代南平岩片和晚二叠世照北山岩组,将原佟家屯岩组和尖山子火山岩合并为晚二叠世佟家屯岩组.最后,提出了清河构造混杂岩带为华北克拉通与兴蒙造山带的界线以及古亚洲洋在华北板块北缘东段的最终闭合时间为中三叠世早期（约245Ma）的认识.     

Investigation of gas content of organic-rich shale:A case study from Lower Permian shale in southern North China Basin,central China

Measuring gas content is an essential step in estimating the commerciality of gas reserves. In this study,eight shale core samples from the Mouye-1 well were measured using a homemade patented gas desorption apparatus to determine their gas contents. Due to the air contamination that is introduced into the desorption canister, a mathematical method was devised to correct the gas quantity and quality.Compared to the chemical compositions of desorbed gas, the chemical compositions of residual gas are somewhat different. In residual gas, carbon dioxide and nitrogen record a slight increase, and propane is first observed. This phenomenon may be related to the exposure time during the transportation of shale samples from the drilling site to the laboratory, as well as the differences in the mass, size and adsorptivity of different gas molecules. In addition to a series of conventional methods, including the USBM direct method and the Amoco Curve Fit(ACF) method, which were used here for lost gas content estimation, a Modified Curve Fit(MCF) method, based on the 'bidisperse' diffusion model, was established to estimate lost gas content. By fitting the ACF and MCF models to gas desorption data, we determined that the MCF method could reasonably describe the gas desorption data over the entire time period, whereas the ACF method failed. The failure of the ACF method to describe the gas desorption process may be related to its restrictive assumption of a single pore size within shale samples. In comparison to the indirect method, this study demonstrates that none of the three methods studied in this investigation(USBM, ACF and MCF) could individually estimate the lost gas contents of all shale samples and that the proportion of free gas relative to total gas has a significant effect on the estimation accuracy of the selected method. When the ratio of free gas to total gas is lower than 45%, the USBM method is the best for estimating the lost gas content, whereas when the ratio ranges from 45% to 75% or is more than 75%, the ACF and MCF methods, are the best options respectively.     

Upscaling permeability for three-dimensional fractured porous rocks with the multiple boundary method

Upscaling permeability of grid blocks is crucial for groundwater models. A novel upscaling method for three-dimensional fractured porous rocks is presented. The objective of the study was to compare this method with the commonly used Oda upscaling method and the volume averaging method. First, the multiple boundary method and its computational framework were defined for three-dimensional stochastic fracture networks. Then, the different upscaling methods were compared for a set of rotated fractures, for tortuous fractures, and for two discrete fracture networks. The results computed by the multiple boundary method are comparable with those of the other two methods and fit best the analytical solution for a set of rotated fractures. The errors in flow rate of the equivalent fracture model decrease when using the multiple boundary method. Furthermore, the errors of the equivalent fracture models increase from well-connected fracture networks to poorly connected ones. Finally, the diagonal components of the equivalent permeability tensors tend to follow a normal or log-normal distribution for the well-connected fracture network model with infinite fracture size. By contrast, they exhibit a power-law distribution for the poorly connected fracture network with multiple scale fractures. The study demonstrates the accuracy and the flexibility of the multiple boundary upscaling concept. This makes it attractive for being incorporated into any existing flow-based upscaling procedures, which helps in reducing the uncertainty of groundwater models.     

Effects of Wave–Current Interaction on Salt Intrusion During a Typhoon Event in a Highly Stratified Estuary

Wave–current interaction (WCI) is important in modulating hydrodynamics and water mixing in estuaries, and thereby the transport of water-borne materials. However, the effects of WCI on salt transport and salt intrusion in estuaries during storm events have been rarely examined. In the present study, we use a coupled atmosphere–ocean–wave–sediment transport (COAWST) modeling system to investigate the effects of WCI on salt intrusion in the highly stratified Modaomen Estuary during Typhoon Hagupit (2008). The model is validated by the measured wave, water elevation, and surface salinity data, and several diagnostic model experiments are conducted. WCI increases the storm surge by 0.8 m at the peak surge (25% of the total surge height). The wave-breaking-induced momentum flux and the Stokes drift increase the magnitude of the landward flow by 0.3 m s^?1 (30% of the total landward flow). In addition, the waves increase water mixing by 2–4 times compared with that without waves. Hence, WCI significantly increases the landward advective salt transport and decreases the steady shear transport. The net effect of the WCI is a significant increase of salt import and salt intrusion during the typhoon event. However, in the aftermath of the storm, the imported salt water is rapidly flushed out by the increased river discharge, and the estuary regains its stratification within one day.