Analytical models of contaminant transport in coastal aquifers

The Henry formulation, which couples subsurface flow and salt transport via a variable-density flow formulation, can be used to evaluate the extent of sea water intrusion into coastal aquifers. The coupling gives rise to nontrivial flow patterns that are very different from those observed in inland aquifers. We investigate the influence of these flow patterns on the transport of conservative contaminants in a coastal aquifer. The flow is characterized by two dimensionless parameters: the Péclet number, which compares the relative effects of advective and dispersive transport mechanisms, and a coupling parameter, which describes the importance of the salt water boundary on the flow. We focus our attention on two regimes – low and intermediate Péclet number flows. Two transport scenarios are solved analytically by means of a perturbation analysis. The first, a natural attenuation scenario, describes the flushing of a contaminant from a coastal aquifer by clean fresh water, while the second, a contaminant spill scenario, considers an isolated point source.     

Features and evaluation of sea/saltwater intrusion in southern Laizhou Bay

Understanding the degree of sea/saltwater intrusion in coastal regions is of great significance to treating the intrusion and improving the environment. Based on the character analysis of the sea/saltwater intrusion, five factors were selected in the fuzzy-synthetical evaluation approach to form the index system, so as to evaluate the degree of sea/saltwater intrusion in southern Laizhou Bay. The results show that the sea/saltwater intrusion is stronger in the middle and northern areas and weaker on the sides and in southern area; currently, the intrusion is relatively serious, and the intrusion area has covered about 68.2% of the areas under study, among which the heavily intruded area is over 50%. Based on the factors analysis of the occurrence and development of sea/saltwater intrusion, the thesis proposes treatment measures.     

银矿自然重砂矿物组合规律及其找矿意义

根据20世纪60年代全国范围内展开的自然重砂测量工作所累积的自然重砂数据资料,统计了全国各省72个典型银矿床的自然重砂情况,通过计算和分析各自然重砂矿物在所对应的类型的矿床中的报出频率,得出火山沉积型、沉积型、变质型、侵入岩型4种类型的银矿所对应的自然重砂矿物组合。展现这4种类型矿床的重砂矿物组合的相似之处及不同之处。按照这种方式建立的不同矿床类型的自然重砂矿物组合,对于建立自然重砂找矿模型具有重要的意义。     

淮南煤田朱集井田岩浆侵入特征研究

在对淮南煤田朱集井田钻孔资料分析的基础上,结合侵入岩化学成分测试、X-射线衍射分析以及薄片显微镜下鉴定等结果,得出研究区侵入岩主要以岩床的形式侵入煤系地层,岩性以闪长岩、花岗岩为主,岩床层数多为单层;受NWW—NW向断裂构造带控制,侵入岩体的分布范围呈现从西向东逐渐扩大,在垂向上,从上部煤层到下部煤层,受岩浆影响的程度有明显加大的态势。由于岩浆侵入煤层,严重破坏了煤层的结构和稳定性,同时,降低了煤的工业利用价值,加大了开采难度。     

Assessment of flow paths and confluences for saltwater intrusion in a deltaic river network

Saltwater intrusion is a serious issue in estuarine deltas all over the world due to rapid urban sprawl and water shortage. Therefore, detecting the major flow paths or locations at risk of saltwater intrusion in estuarine ecosystems is important for mitigating saltwater intrusion. In this paper, we introduce a centrality index, the betweenness centrality (BC), to address this problem. Using the BC as the weighted attribute of the river network, we identify the critical confluences for saltwater intrusion and detect the preferential flow paths for saltwater intrusion through the least‐cost‐path algorithm from a graph theory approach. Moreover, we analyse the responses of the BC values of confluences calculated in the river network to salinity. Our results show that the major flow paths and critical confluences for saltwater intrusion in a deltaic river network can be represented by the least cost paths and the BC values of confluences, respectively. In addition, a significant positive correlation between the BC values of confluences and salinity is determined in the Pearl River Delta. Changes in the salinity can produce significant variation in the BC values of confluences. Therefore, freshwater can be diverted into these major flow paths and critical confluences to improve river network management under saltwater intrusion. Copyright © 2015 John Wiley & Sons, Ltd.     

内蒙古火龙沟铅锌矿床成矿岩体年代学、地球化学及其地质意义

内蒙古火龙沟铅锌矿床是近期勘查发现、预期可达中型规模以上的铅锌矿床之一,笔者对该矿区的侵入岩——正长花岗岩进行了LA-MC-ICP-MS锆石U_Pb定年和主量、微量元素分析,锆石U_Pb定年结果为(224.0±2.5)Ma,表明,该岩体侵位于晚三叠世。岩石地球化学研究结果显示火龙沟正长花岗岩体具有明显富Si O2和ALK、贫Mg O和TFe的特点,A/NK-A/CNK图解显示正长花岗岩属于准铝质花岗岩。微量元素蛛网图显示富集大离子亲石元素Rb、Th、U、K,亏损高场强元素Nb、Ta、Ti。稀土元素配分模式表现出富集LREE,亏损HREE的右倾型,LREE/HREE=8.04~10.40,具有明显Eu的负异常。花岗岩锆饱和温度计算结果表明该花岗岩岩浆形成温度为820℃,属于高温花岗岩,以上地球化学特征和高温的特点表明该花岗岩为A型花岗岩。结合区域构造演化历史,笔者认为该花岗岩体形成于古亚洲洋闭合后的造山后垮塌岩石圈伸展构造环境。     

阿尔金山南缘长沙沟镁铁-超镁铁质层状杂岩体的发现与地质意义——岩石学和地球化学初步研究

阿尔金山南缘地区,侵入于新太古界—新元古界变质地层中的长沙沟镁铁-超镁铁质岩由四个呈断层接触的镁铁-超镁铁质岩块组成,形成年龄为462~470Ma。不同岩块内岩石的地球化学特征虽有差异,但均以LREE及强不相容元素的富集和高的Zr/Y比值（＞4.1）为特征,形成于大陆裂谷环境。其中,清水泉北段可以划分出3~4个主体由辉橄岩-角闪辉长岩构成的岩浆旋回,具有层状岩体的特征,其母岩浆的Mg^#=53.7~55.9,为演化型母岩浆,暗示其经历了富镁矿物的分离结晶,且(Th/Nb)_N＞1.0、Nb/La比值＜1.0、以及发育的矿物逆序包裹现象等表明经历了明显的地壳混染和岩浆混合作用;而清水泉南和长沙沟中段镁铁-超镁铁质岩的(Th/Nb)_N＜1.0、Nb/La比值＞1.0,基本未遭受地壳混染,并且此Mg^#与FeO^T、TiO₂负相关、与SiO₂正相关,呈现良好的Fenner演化趋势特征;清水泉南纯橄岩-辉橄岩具有极高的Mg^#（90.6~84.5）,而赋存有钛-磁铁矿工业矿体的长沙沟中段镁铁-超镁铁岩的Mg^#值较低（75.8~49.2）,推测它们是同一母岩浆（Mg^# =78.2）经Fenner演化趋势后分别形成的早期富Mg矿物堆晶相和稍晚期的富Fe-Ti残余岩浆相。长沙沟中奥陶世裂谷型层状镁铁-超镁铁质杂岩体的发现,意味着这一时期阿尔金山南缘地区处于伸展背景下,具有形成岩浆型PGE-Cu-Ni硫化物矿床和V-Ti-Fe氧化物矿床的地质背景和重要的成矿物质载体。作为该地区一种新的找矿思路,该地区同一构造带内其它镁铁-超镁超镁铁质岩体的性质及可能的金属矿化作用等也是值得进一步研究探索的。     

海岸带海水入侵的研究进展

海岸带海水入侵问题一直是国际社会共同关注的焦点。海水入侵的影响因素很多,其中人为因素占较大比重。海水入侵的方式因地而异,孔隙水含水层海水入侵较为严重。在研究中突变界面模型和过渡带模型各有其实用性。其中过渡带模型更具有适用价值,是今后主要的研究方向。本文概述了海岸带海水入侵问题现状,系统地总结了海岸带海水入侵模型近40多年来的研究成果,分析了研究中存在的困难,为进一步的研究打下基础。     

分布式光纤振动传感系统中数据采集及信号处理系统设计

本文主要介绍了一套分布式光纤振动传感系统中的数据采集及信号处理系统,该系统设计采用高性能的运算放大电路完成光电信号调理,以高精度差动模数转换器AD9246完成模数转换工作,并选用高性能FPGA作为核心逻辑控制器,并以低功耗的OMAP-L137作为CPU负责振动数据计算、网络通讯等工作,从而使该-OTDR分布式光纤振动传感系统测量范围扩展到25 km范围。本文通过计算相邻测点振动增量方法检测是否发生了振动入侵,提高了分布式光纤振动入侵检测的灵敏度。该设计方法提高分布式光纤振动传感系统的信噪比,使得该系统振动检测灵敏度提高、抗干扰能力增强,因此该分布式光纤振动传感系统可以用于实际工程的振动监控。     

Geochemistry,Zircon U–Pb Analysis,and Biotite 40Ar/39Ar Geochronology of the Maoling Gold Deposit,Liaodong Rift,NE China

The Maoling gold deposit is located in the southwestern part of the Liaodong rift, NE China, and has estimated reserves of 25 t. In this paper we present the results of an investigation into the geochronology and geodynamic mechanisms of igneous activity and metallogenesis within the Maoling gold deposit. New zircon U–Pb age data, biotite ⁴⁰Ar/³⁹Ar age data, whole‐rock geochemistry, and Hf isotopic analyses are presented in order to constrain the petrogenesis and mineralization of the deposit. Zircon U–Pb dating of the Wolongquan biotite monzogranite and Maoling biotite granite yielded mean ages of 194.0 ± 1.1 Ma and 196.1 ± 1.1 Ma, respectively. All the granites are characteristically high‐K calc‐alkaline, enriched in light rare earth elements and large ion lithophile elements, and depleted in high field strength elements, which is consistent with the geochemical characteristics of arc‐type magmas. The Hf isotope characteristics indicate that the granites formed by partial melting of early Paleoproterozoic crustal material. In addition, biotite ⁴⁰Ar/³⁹Ar dating indicates that the Maoling gold deposit formed at 188.9 ± 1.2 Ma, implying that the mineralization was related to both the granite intrusions. Taking into account previous data on S–Pb–O–H isotopes and our new age data, the Maoling deposit can be classified as an intrusion‐related gold deposit. Taking into account the geology of the study area and adjacent regions, we propose that the Maoling gold deposit and its associated granitic intrusions formed in a geodynamic setting that was dominated by subduction of the Paleo‐Pacific Plate beneath the Eurasian continent.