离子选择电极法测定水热气体中的硼含量及硼的气态迁移能力研究

火山和成矿地质现象表明硼可以在含水流体和气体中运移,本文应用离子选择电极法测定水热气体中硼的溶解度,以揭示硼的气态迁移能力。使用氟硼酸盐选择电极,测定了经氟硼酸化的硼酸标准溶液和含硼气体凝结水的电位,当硼含量处于地质流体的主要范围内(0.52~524.50 mg/L)时,电极电位与硼浓度的对数呈现出灵敏度很高的能斯特线性关系,标准曲线具有很好的稳定性和重现性。本方法测定硼的检出限为0.13 mg/L,低于饮用水标准规定的硼含量限值,适用于测定水热气体中的硼含量。硼酸挥发实验显示,硼在150℃、0.37 MPa水蒸气中的含量可达0.65%~0.72%,与富硼火山喷气的硼含量相符,显示硼在高温水热条件下可在气相中显著迁移,且H_3BO_3气态分子是硼的主要迁移形式之一。矿床地质特征和实验表明,硼的气态迁移和电气石化与稀有金属型伟晶岩的形成和矿化以及某些热液-气成型Sn-W、Mo矿床和斑岩型Cu、Au矿床的形成密切相关。     

高压密闭酸溶-电感耦合等离子体质谱法测定花岗闪长岩中的微量锆

采用高压密闭酸溶处理样品,电感耦合等离子体质谱(ICP-MS)测定岩石中的多种微量、痕量元素是地质分析中普遍采用的一种分析方法,但在分析花岗闪长岩样品时,由于锆赋存在难溶的副矿物(锆石、金红石)中,会出现锆溶出率偏低的现象。针对这一现象,本研究增加了赶硅的预处理过程,加大氢氟酸用量,在溶液介质中引入氟离子使锆形成氟络离子改善了锆的稳定性,将锆的溶出率提高到95%左右,实现了花岗闪长岩中微量锆的准确测定。本方法的精密度(RSD,n=11)小于5%,检出限为0.052μg/g。应用于分析克拉玛依地区花岗闪长岩中的锆,测定值与过氧化钠、偏硼酸锂碱熔以及X射线荧光光谱法的测定值有良好的一致性,且基体效应小、检出限低,还可以满足锂、铍、钪等其他多种微量元素的同时测定。     

微波消解-氢化物发生原子荧光光谱法和质谱法测定高有机质无烟煤中汞砷的可行性研究

微波消解技术适用于处理大部分煤炭样品,但对于高有机质含量的无烟煤样品,因其煤化程度高,含有多种复杂的高分子有机化合物,应用现有的消解技术不能将其完全消解。本文对微波消解的实验条件包括消解试剂、消解温度及消解时间进行优化,确定了适合处理高有机质无烟煤的消解体系,评价了采用HG-AFS和ICP-MS测定其中总汞和总砷含量的可行性。结果表明,以硝酸-硫酸-氢氟酸(6∶4∶0.5)作为微波消解试剂,消解温度达205℃,保持30 min可将高有机质含量的无烟煤彻底分解,其中硫酸对无烟煤的消解起到了关键作用;ICP-MS与HG-AFS对汞的检测结果一致,回收率都达到98%以上,但由于砷的化学形态复杂,有机态砷不能全部转化无机态砷使得HG-AFS对砷的检测结果偏低。因此,对于有机质含量特别高(81%~90%)的煤炭样品,微波消解可将其彻底转化为溶液,用ICP-MS可以准确定量其中的汞和砷,而HG-AFS不能作为检测砷的有效手段。     

Geomechanical modelling of fault reactivation in the Cooper Basin,Australia

The Australian Cooper Basin is a structurally complex intra-cratonic basin with large unconventional hydrocarbon potential. Fracture stimulation treatments are used extensively in this basin to improve the economic feasibility; however, such treatments may induce fault activity and risk the integrity of hydrocarbon accumulations. Fault reactivation may not only encourage tertiary fluid migration but also decrease porosity through cataclasis and potentially compartmentalise the reservoir. Relatively new depth-converted three-dimensional seismic surveys covering the Dullingari and Swan Lake 3D seismic surveys were structurally interpreted and geomechanically modelled to constrain the slip tendency, dilation tendency and fracture stability of faults under the present-day stress. A field-scale pore pressure study found a maximum pressure gradient of 11.31 kPa/m within the Dullingari 3D seismic survey, and 11.14 kPa/m within the Swan Lake 3D seismic survey. The present-day stress tensor was taken from previously published work, and combined with local pore pressure gradients and depth-converted field-scale fault geometries, to conclude that SE–NW-striking strike-slip faults are optimally oriented to reactivate and dilate. High-angle faults striking approximately E–W appear most likely to dilate, and act as fluid conduits irrespective of being modelled under a strike-slip or compressional stress regime. Near-vertical SE–NW and NE–SW-striking faults were modelled to be preferentially oriented to slip and reactivate under a strike-slip stress regime. Considering that SE–NW-striking strike-slip faults have only recently been interpreted in the literature, it is possible that many reservoir simulations and development plans have overlooked or underestimated the effect that fault reactivation may have on reservoir properties. Future work investigating the likelihood that fracture stimulation treatments may be interacting, and reactivating, pre-existing faults and fractures would benefit field development programs utilising high-pressure hydraulic fracture stimulation treatments.     

Stress and pore pressure histories in complex tectonic settings predicted with coupled geomechanical-fluid flow models

Most of the methods currently used for pore pressure prediction in sedimentary basins assume one-dimensional compaction based on relationships between vertical effective stress and porosity. These methods may be inaccurate in complex tectonic regimes where stress tensors are variable. Modelling approaches for compaction adopted within the geotechnical field account for both the full three-dimensional stress tensor and the stress history. In this paper a coupled geomechanical-fluid flow model is used, along with an advanced version of the Cam-Clay constitutive model, to investigate stress, pore pressure and porosity in a Gulf of Mexico style mini-basin bounded by salt subjected to lateral deformation. The modelled structure consists of two depocentres separated by a salt diapir. 20% of horizontal shortening synchronous to basin sedimentation is imposed. An additional model accounting solely for the overpressure generated due to 1D disequilibrium compaction is also defined. The predicted deformation regime in the two depocentres of the mini-basin is one of tectonic lateral compression, in which the horizontal effective stress is higher than the vertical effective stress. In contrast, sediments above the central salt diapir show lateral extension and tectonic vertical compaction due to the rise of the diapir. Compared to the 1D model, the horizontal shortening in the mini-basin increases the predicted present-day overpressure by 50%, from 20 MPa to 30 MPa. The porosities predicted by the mini-basin models are used to perform 1D, porosity-based pore pressure predictions. The 1D method underestimated overpressure by up to 6 MPa at 3400 m depth (26% of the total overpressure) in the well located at the basin depocentre and up to 3 MPa at 1900 m depth (34% of the total overpressure) in the well located above the salt diapir. The results show how 2D/3D methods are required to accurately predict overpressure in regions in which tectonic stresses are important.     

应用ICP-MS研究川西南龙马溪组泥页岩稀土元素特征及沉积环境

为深入研究盐源盆地龙马溪组黑色岩系的沉积环境、构造背景及物源属性,指导区域页岩气勘探及相关研究,本文利用电感耦合等离子体质谱技术研究了盐源盆地南缘龙马溪组黑色页岩的稀土元素地球化学特征和沉积环境。结果表明:该区稀土总量偏低,轻稀土富集重稀土亏损,轻重稀土分异较大;δCe_N均值为0.87,显示弱的负异常,δEu_N值为0.66~1.43,变化范围较大,说明源岩成分复杂;La_S/Yb_S均值为1.31,说明研究区构造背景主要为被动大陆边缘,源岩为古老沉积岩、花岗岩及中基性岩的混合物,推测康滇古陆为其提供了主要物源。δCe_S为负异常,δEu_S为正异常,La/Ce1等特征均指示沉积期水体为还原环境,推测为深水陆棚沉积,且受到一定程度热水沉积影响。深海热液带来丰富的营养元素有利于有机质形成,还原水体环境有利于有机质保存,使得研究区龙马溪组泥岩页富含有机质,且富有机质页岩段厚度较大,由此初步认为龙马溪组泥页岩为优质烃源岩储层。     

铌钽元素分析技术新进展

铌钽是发展新兴产业所需的功能性和结构性材料,铌钽矿产是国家重点支持的战略新兴矿产资源,开展相关物料中铌钽的分析技术研究具有重要意义。由于铌和钽的物理化学性质十分相似,彼此难以分离,且易水解,加之地质样品分解困难,因此铌和钽的分析测试一直困扰着分析工作者。本文重点对铌钽元素分析中的样品前处理技术和现代分析测试技术进行综述。样品前处理是铌钽分析的关键环节,结合分析方法和样品特性,选择合理的样品分解和分离富集方法是准确测定铌钽的前提。仪器分析是现代分析测试技术的主流,电感耦合等离子体发射光谱/质谱法(ICP-OES/MS)是目前测定铌钽应用最多的方法,需要解决共存组分的干扰、基体效应和盐类影响等问题。激光剥蚀(LA)技术、X射线荧光光谱法(XRF)和中子活化分析法(NAA)采用固体进样,避免了前期样品处理的繁琐步骤和杂质的引入,是铌钽元素分析发展的方向。     

树脂交换分离-电感耦合等离子体质谱法测定铅锌矿中钨钼锡锗硒碲

铅锌矿常与硫化矿共生形成复合多金属矿床,其中伴生有益元素的含量对矿床的综合利用评估有重要的参考意义。在目前常用方法中,钨钼锡锗硒碲主要采用分组或单独熔矿和测试的方法,操作强度大、分析效率低,且高含量铜、铅和含量高于1μg/g的硒分别干扰钨钼和碲的测定。本文采用过氧化钠碱熔,提取后加入0. 8%柠檬酸溶液络合钨、钼、锡形成金属复合物,以8～9 g阳离子树脂交换分离高含量钠盐和铜、铅、锌、铁等主量元素,采用动能歧视模式以铼、硼为内标用电感耦合等离子体质谱仪同时测定钨钼锡锗硒碲的含量。经树脂处理后,铜铅锌铁的去除率均高于96%,在测定介质中实际浓度为0. 192 ng/mL～1. 28μg/mL,基本消除了主量元素的干扰。各待测元素工作曲线相关系数为0. 9994～0. 9999,优于阳离子树脂处理前的0. 9923～0. 9992。经标准物质验证,各元素测定相对误差为-8. 33%～7. 00%,加标回收率为94. 9%～107. 5%,相对标准偏差(RSD,n=8)小于8%。该方法在样品前处理环节将主量干扰元素从溶液体系中分离,优化了测定介质,实现了铅锌矿中多元素的准确快速测定。     

乙醇介质制备载炭泡塑及其在地质样品金测定中的应用

载炭泡塑相较于无负载泡塑,可有效提高泡塑对金的吸附能力,但现有制备载炭泡塑的方法制备效率不高。为了缩短制备载炭泡塑的时间,提高制备效率,本文采用活性炭-乙醇溶液制备载炭泡塑,通过优化制备条件,包括负载介质的种类、试剂浓度、浸泡时间,使得制备100个载炭泡塑的时间可以控制在30 min之内,并结合ICP-OES建立了测定地质样品中金的方法。实验结果表明:该方法的振荡时间可以缩短至20 min。金的质量浓度在0～100. 00μg/mL范围内与光谱强度呈良好的线性关系,相关系数为0. 9997,方法检出限(3σ)为0. 0066μg/g,测定结果相对标准偏差为0. 81%～2. 11%(n=10)。该方法经4个国家标准物质验证,准确度与精密度良好,能够满足地质样品中金的分析测试要求。     

Estimating liquefaction-induced settlement of shallow foundations by numerical approach

Occurrence of liquefaction in saturated sand deposits underlying foundation of structure can cause a wide range of structural damages starting from minor settlement, and ending to general failure due to loss of bearing capacity. If the bearing capacity failure is not the problem, reliable estimation of the liquefaction-induced settlement will be of prime importance in assessment of the overall performance of the structure. Currently, there are few procedures with limited application in practice for estimation of settlement of foundations on liquefied ground. Therefore, development of a general relationship is important from the practical viewpoint. In this paper, the dynamic response of shallow foundations on liquefied soils is studied using a 3D fully coupled dynamic analysis. For verification of the numerical model, simulation of a centrifuge experiment is carried out and the analysis results are compared with the experimental measurements. The results of centrifuge experiment are taken from the literature for the purpose of comparison and the experiment has not been performed by the authors. After verification of the numerical model, a practical relationship for estimation of liquefaction-induced settlement of rigid footings on homogeneous loose to medium fine sand is proposed based on the results of a comprehensive parametric study. In the interpretation process, the soil layer thickness in which the liquefaction takes place is found to be a key parameter, since by normalization with respect to this parameter, effects of a number of other parameters can be eliminated.