Origin of sulphate in the unsaturated zone and groundwater of a loess aquifer     

Yin Long  Tianming Huang  Fen Zhang  Zhenbin Li  Baoqiang Ma  Yiman Li  Zhonghe Pang 《水文研究》2021,35(4):e14166

The use of the sulphate mass balance (SMB) between precipitation and soil water as a supplementary method to estimate the diffuse recharge rate assumes that the sulphate in soil water originated entirely from atmospheric deposition; however, the origin of sulphate in soil and groundwater is often unclear, especially in loess aquifers. This study analysed the sulphur (δ³⁴S-SO₄) and oxygen (δ¹⁸O-SO₄) isotopes of sulphate in precipitation, water-extractable soil water, and shallow groundwater samples and used these data along with hydrochemical data to determine the sources of sulphate in the thick unsaturated zone and groundwater of a loess aquifer. The results suggest that sulphate in groundwater mainly originated from old precipitation. When precipitation percolates through the unsaturated zone to recharge groundwater, sulphates were rarely dissolved due to the formation of CaCO₃ film on the surface of sulphate minerals. The water-extractable sulphate in the deep unsaturated zone (>10 m) was mainly derived from the dissolution of evaporite minerals and there was no oxidation of sulphide minerals during the extraction of soil water by elutriating soil samples with deionized water. The water-extractable concentration of SO₄ was not representative of the actual SO₄ concentration in mobile soil water. Therefore, the recharge rate cannot be estimated by the SMB method using the water-extractable concentration of SO₄ in the loess areas. This study is important for identifying sulphate sources and clarifying the proper method for estimating the recharge rate in loess aquifers.  相似文献   

辽东铀成矿带连山关地区韧性剪切带与铀成矿作用     

吴迪  刘永江  李伟民  常瑞虹 《岩石学报》2020,36(8):2571-2588

连山关地区位于华北克拉通北缘铀成矿省辽东铀成矿带，已知铀矿床（点）均发育在韧性剪切带附近。为了解韧性剪切带运动学、几何学构造变形机制及与铀矿的关系，本文以连山关岩体周缘韧性剪切带为研究对象，通过野外宏观调查和室内微观研究相结合的研究方法，探讨构造变形期次、韧性剪切带形成机理及其对铀成矿的控制作用。研究表明：连山关岩体周缘发育的韧性剪切带与近南北向挤压构造变形有关，其右行韧性剪切带应变类型为压扁应变，属于一般压缩-平面应变范围，Flinn指数K值在0.19~0.69之间，岩石类型属于S/SL型构造岩。研究区内铀矿体均为隐伏盲矿体，主要赋存于沿着连山关岩体和辽河群接触带右行剪切作用形成的背斜褶皱核部，和北东东向断裂关系密切。综合分析认为，连山关岩体南缘北西向韧性剪切带为一级控矿构造，是区内铀矿热液运移的通道，而剪切带边部的晚期北东东向断裂则是铀矿储存空间；铀源可能来自于太古宙古风化壳，并在大型韧性剪切活动（提供热液运移通道）和基性脉岩侵入（提供热源和还原剂）等综合因素作用下运移、富集成矿。  相似文献   

准噶尔盆地玛湖凹陷西斜坡三叠系百口泉组扇三角洲优质储集层预测          下载免费PDF全文

桑林翔  刘军  王贵文  王苏天  李全  张云龙 《古地理学报》2020,22(6):1053-1064

针对准噶尔盆地玛湖凹陷西斜坡风南地区三叠系百口泉组扇三角洲砂岩物性空间变化大、优质储集层(孔隙度大于7.4%,渗透率大于0.05×10^-3μm²)预测难的问题,在沉积岩石学、地震沉积学以及地震反演和解释理论指导下,综合利用测井、岩心和三维地震等资料开展了高精度层序地层划分、沉积微相描述和优质储集层地震反演研究。建立了风南井区四级层序地层格架,明确了扇三角洲多期水进水退的充填过程,指出SSQ3和SSQ5是优质储集层的发育层系;识别出扇三角洲平原分流河道、河道间和扇三角洲前缘水下分流水道、河口坝、席状砂等沉积微相,指出扇三角洲平原是优质储集层发育相带;通过应用高分辨层序地层纵向边界和沉积相横向边界约束,进行分层相控叠后地震波阻抗反演,提升储集层预测精度,在SSQ3和SSQ5预测5个优质储集层发育区,提出3口井的井位建议,钻探均获工业油流。  相似文献   

Did the “Autochthonous” European foreland of Corsica Island (France) experience Alpine subduction?     

Maria Di Rosa  Chiara Frassi  Michele Marroni  Francesca Meneghini  Luca Pandolfi 《地学学报》2020,32(1):34-43

Despite the important role played by the Sardinia‐Corsica block in the reconstruction of the Western Mediterranean geodynamics, the extent of involvement of the “Autochthonous” European margin exposed in Corsica (France) (i.e., Hercynian Corsica) in the Alpine orogeny remains uncertain. Stratigraphic and sedimentological studies in the post‐Variscan deposits on the Hercynian Corsica are scarce and even scarcer are the structural and metamorphic constraints. To face these uncertainties, we present new stratigraphic, structural and metamorphic data from the area of Razzo Bianco, Central Corsica, where a complete sequence belonging to the European continental margin is exposed. Field and structural investigations demonstrate that the sequence represents the easternmost edge of the downgoing European plate. Metamorphic studies on the Eocene deposits indicate that the margin was buried at depth up to blueschist facies conditions and, subsequently, it was progressively exhumed mainly through the activation of oblique top‐to‐the NW shear zones.  相似文献   

大深度潜航器水下空间运动建模与仿真     

乔冰  刘鑫  袁龙 《数字海洋与水下攻防》2020,3(1):65-70

分析大深度潜航器水下空间运动特点，建立描述其空间运动的数学模型，并以数学模型为基础利用 MATLAB\Simulink 软件完成潜航器空间运动仿真模型的开发。在搭建的仿真模型基础上，通过数学仿真手段分析了潜航器在螺旋下潜、抛载过渡、定角爬升、稳定至水面航行状态下的水下运动全过程，给出了具有弧形翼板的潜航器外形设计方案的运动能力仿真评估，为后续潜航器运动能力优化设计提供仿真依据。  相似文献   

Interactive Effects of Ultraviolet Radiation and Dissolved Organic Carbon on Phytoplankton Growth and Photosynthesis in Sanya Bay,Northern South China Sea     

Liao  Jianzu  Xu  Jie  Yuan  Xiangcheng  Liang  Yuxian  Guo  Yajuan  Zhou  Weihua  Huang  Hui  Liu  Sheng  Long  Aimin 《Ocean Science Journal》2019,54(4):581-593

Ocean Science Journal - The effects of a simulated climate change scenario, i.e., increased ultraviolet radiation (UVR) and dissolved organic carbon (DOC), on the growth and photosynthesis of...  相似文献   

文莱-沙巴盆地深水褶皱冲断带构造变形特征及成因机制          下载免费PDF全文

唐武  赵志刚  张功成  谢晓军  刘世翔  王一博  宋双  王龙  孙瑞  郭佳 《地球物理学报》2018,61(10):4281-4295

为揭示活动陆缘深水褶皱冲断带的特征及成因，本文利用地震和区域地质资料的综合分析，系统阐述了文莱—沙巴盆地深水褶皱冲断带的构造变形特征，并结合盆地演化动力学特点，探讨其构造变形机制及其对深水区油气成藏的影响.研究结果表明，文莱—沙巴盆地深水褶皱冲断带具有"垂向分期、平面分段"的特点，垂向上，以中中新统底界面为界可划分为下部（始新世-早中新世）和上部（中中新世-现今）两套逆冲褶皱冲断体系，其中下部逆冲褶皱冲断带的形成与古南海的俯冲作用密切相关，上部逆冲褶皱冲断带是中中新世以来三角洲前缘重力滑动与苏禄海扩张造成的区域挤压应力远程效应共同作用的结果，且苏禄海扩张造成的远程挤压效应主控平面上南北段褶皱冲断带变形的差异性，导致北段褶皱变形强度大于南段，具有背斜褶皱数量多、褶皱间距离短、逆冲断层倾角陡的特点，南段反之；且晚上新世以来北段深水区地层缩短量大于陆架区伸展量，两者之差为2~6 km，而南段两者相当，仅受三角洲前缘重力滑动影响.整个褶皱冲断带发育断弯、断展、断滑褶皱等3种断层相关褶皱以及叠瓦扇和冲起构造2种逆冲构造组合，是多期NW向挤压应力作用下形成的大型逆冲推覆构造，以前展式向盆地扩展.此外，由于中中新世以来逆冲断层的持续活动，研究区深水褶皱冲断带发育众多构造圈闭，油气成藏条件优越，且南段优于北段，靠近陆坡的近端优于远端，可作为勘探部署重点.  相似文献   

Precise Location of Earthquakes at the Eastern Boundaries of the Sichuan-Yunnan Rhombic Block     

Fu Ying  Hu Bin  Long Feng  Wang Shiyuan 《中国地震研究》2018,32(4):470-481

Based on the seismic station data sets from Sichuan and Yunnan provinces, we employed a multi-step seismic location method (Hypo2000 + Velest + HypoDD) to precisely locate the 7,787 earthquakes that occurred during 2010-2015 along the eastern boundaries of the Sichuan-Yunnan rhombic block, namely from southern Dawu to the Qiaojia segment. The final results show that location precision is greatly advanced and epicenter distribution exhibits good consistency with the linear distribution of the seismic faults. Earthquake distribution is quite intensive at the intersection region in the southern segment of the Xianshuihe fault, the Anninghe fault zone, the Xiaojinhe fault zone and the Daliangshan fault zone to the east. The depth profile of seismicity shows a clear stepwise activity along the active seismic fault zones. The profile crossing the faults of the Xianshuihe, Anninghe, and Daliangshan presents a complex interaction among faults near the multiple faults intersection region, Shimian, where the earthquakes are obviously divided into two groups in depth. Earthquakes are very rare at the depth of 15km-20km, which is consistent with the region of the plastic rheology between 14km-19km calculated by Zhu Ailan et al.,(2005).  相似文献   

港湾中海啸流的模拟及其时空演变特征对输入条件不确定性的响应分析          下载免费PDF全文

王培涛  闪迪  侯京明  王岗  高义  任智源  范婷婷  王宗辰  王君成 《地球物理学报》2018,61(4):1325-1340

一直以来，海啸波特征作为表征海啸潜在破坏性的参数指标得到了广泛应用，特别是针对近场极端海啸事件造成的灾害来说，这种表征具有较好的适用性.然而总结分析历史海啸事件造成的损失发现：在远场近岸及港湾系统中，海啸诱导的强流却是造成损失的主要原因.陆架或港湾振荡导致海啸波幅快速升降诱发强流，可能促使港工设施受到威胁及损害，进而对海啸预警服务及海事应急管理提出了新的挑战.因此，全面理解与评估海啸在港湾中诱发的灾害特征，探索港湾中海啸流的数值模拟方法，发展针对港湾尺度的海啸预警服务指导产品尤为迫切.受限于海啸流验证数据的缺乏及准确模拟海啸流技术方法的诸多不确定性，大部分海啸数值模拟研究工作主要是针对水位特征的研究及验证，可能导致对港湾中海啸灾害危险性认识的曲解与低估.本研究基于非线性浅水方程，针对夏威夷群岛三个典型港湾建立了精细化海啸数值模型（空间分辨率达到10 m），并联合有限断层破裂模型计算分析了日本东北地震海啸在三个港湾及其邻近区域的海啸特征，波、流计算结果与实测结果吻合较好，精细化的海啸港湾模型模拟结果可信.模拟发现港湾中较小的波幅，同样可以产生强流.综合分析日本东北地震海啸波、流特征对输入条件不确定性的响应结果发现：港湾中海啸波-流能量的空间分布特征差异较大，这与港湾系统中海啸波的驻波特性相关；相比海啸波幅空间特征，海啸流特征具有更强的空间敏感性；海啸流时空分布特征对输入条件的不确定性响应比海啸波幅对这些不确定性的响应更强，海啸流的模拟与预报更有挑战性；不确定性对海啸流计算精度的影响会进一步传导放大港湾海啸流危险性的评估及对港工设施产生的应力作用的误差，合理的输入条件对海啸流的精确模拟至关重要.最后，希望通过本文的研究可以从海啸波-流特征角度更加全面认识近岸海啸灾害特征，拓展海啸预警服务的广度与深度，从而为灾害应急管理部门提供更加科学合理的辅助决策产品.  相似文献   

Chemical and mineralogical characterization of the Mineo (Sicily,Italy) pallasite: A unique sample          下载免费PDF全文

A. Zucchini  M. Petrelli  F. Frondini  C. M. Petrone  P. Sassi  A. Di Michele  S. Palmerini  O. Trippella  M. Busso 《Meteoritics & planetary science》2018,53(2):268-283

The Mineo pallasite is characterized here for the first time. The only 42 g still available worldwide is part of the collection of the Department of Physics and Geology, University of Perugia. A multianalytical approach was used, joining field-emission scanning electron microscopy, Raman analysis, X-ray powder diffraction, electron-probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry. Results highlighted that (1) the Mineo pallasite belongs to the Main Group pallasites; (2) the silicate component is essentially olivine, with no pyroxene component; (3) the olivine chemical composition varies in terms of both iron and trace elements; (4) the metal phase is essentially kamacite with the taenite mainly found in the plessite structure; (5) phosphide phases are present as schreibersite and barringerite. The observed compositional variability in olivines as well as their occurrence as both angular and rounded crystals suggest that the Mineo pallasite could have been derived from a large impact of a differentiated parent body with a larger solid body. The resulting pallasite conglomerate consists of the compositionally different olivines, likely coming from different areas of the same differentiated parent body, and the residual molten Fe-Ni.  相似文献