西昆仑玛尔坎苏石炭纪大型锰矿带构造背景与成矿条件     

张连昌  张帮禄  董志国  谢月桥  李文君  彭自栋  朱明田  王长乐 《吉林大学学报(地球科学版)》2020,50(5):1340-1357

西昆仑北段玛尔坎苏地区探明的大型碳酸锰成矿带，是我国近年最重要的找矿成果之一。该锰矿带构造上属北昆仑晚古生代弧后伸展盆地，其构造动力学背景为古特提斯洋向北俯冲于塔里木地块之下形成的弧盆体系。锰矿体主要发育于晚石炭世喀拉阿特河组含炭泥质灰岩夹薄层灰岩中。矿石中主要金属矿物为菱锰矿（75%~95%），次为软锰矿、硫锰矿及少量黄铁矿等。含锰岩系岩性和岩相学研究表明，玛尔坎苏锰矿带属典型的海相沉积锰矿床，其矿床成因可能与晚古生代半局限盆地沉积和海底热液活动有关。海底热液活动可能为成矿提供了丰富的物质来源。含锰岩系元素和同位素地球化学特征表明，玛尔坎苏锰矿沉淀时的水体环境为常氧条件，而矿层下盘（部分）岩系的岩性及地球化学特征反映其沉积时的水体环境为低氧—贫氧条件。玛尔坎苏锰矿带锰矿石具有负的δ¹³C值（-23.3‰~-10.0‰），推测有机质导致的还原作用是该锰矿由原生氧化锰在成岩期转化为菱锰矿和形成富锰矿的重要机制。  相似文献   

Conversion relationship of rainfall-soil moisture-groundwater in Quaternary thick cohesive soil in Jianghan Plain,Hubei Province,China     

《China Geology》2020,3(3):462-472

The scientific field test site of rainfall-soil moisture-groundwater conversion in Dabie Mountain Area–Jianghan Plain is located in the northern region of the Jianghan Plain, the transition zone between the Dabie Mountain Area and Jianghan Plain. It’s a great field test site to study the material and energy exchange among rainfall, soil moisture, and groundwater of the Earth ’s critical zone in subtropical monsoon climate plain areas. This paper analyzed the connection between rainfall and volume water content (VWC) of soil at different depths of several soil profiles, and the dynamic feature of groundwater was discussed, which reveals the rainfall infiltration recharge of Quaternary Upper Pleistocene strata. The results show that the Quaternary Upper Pleistocene aquifer groundwater accepts a little direct rainfall recharge, while the lateral recharge is the main supplement source. There were 75 effective rainfall events among 120 rainfall events during the monitoring period, with an accumulated amount of 672.9 mm, and the percentages of effective rainfall amount and duration time were 62.50% and 91.56%, respectively. The max evaporation depth at the upper part in Quaternary cohesive soil was no less than 1.4 m. The soil profile was divided into four zones: (1) The sensitive zone of rainfall infiltration within 1.4 m, where the material and energy exchange frequently near the interface between atmosphere and soil; (2) the buffer zone of rainfall infiltration between 1.4 m and 3.5 m; (3) the migration zone of rainfall infiltration between 3.5 m and 5.0 m; and (4) the rainfall infiltration and groundwater level co-influenced zone below 5.0 m. The results revealed the reaction of soil moisture and groundwater to rainfall in the area covered by cohesive soil under humid climate in Earth ’s critical zone, which is of great theoretical and practical significance for groundwater resources evaluation and development, groundwater environmental protection, ecological environmental improvement, drought disaster prevention, and flood disaster prevention in subtropical monsoon climate plain areas.  相似文献   

载人潜水器运行管理机制探析          下载免费PDF全文

齐海滨  李德威  刘保华  杨雷  刘晓辉 《海洋开发与管理》2019,36(7):3-7

为了探索深海,不同类型的深海运载装备得以成功开发,并应用于深海科学、资源勘探开发、工程保障及战略安全等不同领域。深海运载装备可以分为载人潜水器(HOV)、遥控深潜器(ROV)、自治式深潜器(AUV)及混合型深潜器,其中以载人潜水器为代表的高技术装备群成为建设海洋强国的重要保障力量。文章对美国"阿尔文"号、俄罗斯"和平I"号和"和平II"号、日本"深海6500"号、法国"鹦鹉螺"号、中国"蛟龙"号载人潜水器运行管理机制进行了阐述,综合比较其优缺点,提出了建立职业化运行保障队伍、优化作业流程,创新组织结构、探索多型潜水器海上作业模式等运行管理机制构架的建议。  相似文献   

尼日尔三角洲东部深水区构造特征及其形成机理     

赵江  王秋良  卢圣力  付博  杜峰 《大地测量与地球动力学》2019,39(7):691-695

研究尼日尔三角洲东部深水区块发现，整个盆地从陆向洋具有3个大的构造分区：伸展拉张区、过渡区和挤压逆冲区。伸展区以大型同沉积断层伴生大量滚动背斜构造为特征，过渡区发育大量泥底辟构造，挤压区以复杂的逆冲叠瓦构造为主。通过分析形成机理，揭示东部深水转换带上M研究区构造特征，按构造的演化特征将该区构造分为泥底辟型、冲断-泥底辟混合型、逆冲型3种类型，提出研究区内的圈闭主要以构造-岩性圈闭为主，为尼日尔三角洲盆地深水勘探提供新的理论指导。  相似文献   

Intercomparison of measurements of bulk snow density and water equivalent of snow cover with snow core samplers: Instrumental bias and variability induced by observers     

J. Ignacio López-Moreno  Leena Leppänen  Bartłomiej Luks  Ladislav Holko  Ghislain Picard  Alba Sanmiguel-Vallelado  Esteban Alonso-González  David C. Finger  Ali N. Arslan  Katalin Gillemot  Aynur Sensoy  Arda Sorman  M. Cansaran Ertaş  Steven R. Fassnacht  Charles Fierz  Christoph Marty 《水文研究》2020,34(14):3120-3133

Manually collected snow data are often considered as ground truth for many applications such as climatological or hydrological studies. However, there are many sources of uncertainty that are not quantified in detail. For the determination of water equivalent of snow cover (SWE), different snow core samplers and scales are used, but they are all based on the same measurement principle. We conducted two field campaigns with 9 samplers commonly used in observational measurements and research in Europe and northern America to better quantify uncertainties when measuring depth, density and SWE with core samplers. During the first campaign, as a first approach to distinguish snow variability measured at the plot and at the point scale, repeated measurements were taken along two 20 m long snow pits. The results revealed a much higher variability of SWE at the plot scale (resulting from both natural variability and instrumental bias) compared to repeated measurements at the same spot (resulting mostly from error induced by observers or very small scale variability of snow depth). The exceptionally homogeneous snowpack found in the second campaign permitted to almost neglect the natural variability of the snowpack properties and focus on the separation between instrumental bias and error induced by observers. Reported uncertainties refer to a shallow, homogeneous tundra-taiga snowpack less than 1 m deep (loose, mostly recrystallised snow and no wind impact). Under such measurement conditions, the uncertainty in bulk snow density estimation is about 5% for an individual instrument and is close to 10% among different instruments. Results confirmed that instrumental bias exceeded both the natural variability and the error induced by observers, even in the case when observers were not familiar with a given snow core sampler.  相似文献   

Forests and floods: Using field evidence to reconcile analysis methods     

James C. Bathurst  Barry Fahey  Andrés Iroumé  Julia Jones 《水文研究》2020,34(15):3295-3310

The extent to which forests, relative to shorter vegetation, mitigate flood peak discharges remains controversial and relatively poorly researched, with only a few significant field studies. Considering the effect purely of change of vegetation cover, peak flow magnitude comparisons for paired catchments have suggested that forests do not mitigate large floods, whereas flood frequency comparisons have shown that forests mitigate frequencies over all magnitudes of flood. This study investigates the apparent inconsistency using field-based evidence from four contrasting field programmes at scales of 0.34–3.1 km². Repeated patterns are identified that provide strong evidence of real effects with physical explanations. Magnitude and frequency comparisons are both relevant to the impact of forests on peak discharges but address different questions. Both can show a convergence of response between forested and grassland/logged states at the highest recorded flows but the associated return periods may be quite variable and are subject to estimation uncertainty. For low to moderate events, the forested catchments have a lower peak magnitude for a given frequency than the grassland/logged catchments. Depending on antecedent soil saturation, a given storm may nevertheless generate peak discharges of the same magnitude for both catchment states but these peaks will have different return periods. The effect purely of change in vegetation cover may be modified by additional forestry interventions, such as road networks and drainage ditches which, by effectively increasing the drainage density, may increase peak flows for all event magnitudes. For all the sites, forest cover substantially reduces annual runoff.  相似文献   

Analysis of Anomalous Characteristics of Regional Crustal Deformation before the September 16th, 2019 Zhangye MS5.0 Earthquake, Gansu, China     

MA Haiping  WANG Qian  ZHANG Bo  WU Shanyi  WANG Pengtao  DOU Xiying  LI Minjuan 《中国地震研究》2020,34(2):210-218

To study the crustal movement in the vicinity of the epicenter before the Zhangye M_S5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field analysis based on the CMONOC data observed from GPS. The baseline time series between two continuous GPS stations and the strain time series of an area among several stations are analyzed in the epicenter area. The resulting time series of baseline azimuth around the epicenter reflects that the energy of the fault in the northern margin of Qilian Mountain is accumulated continuously before 2017. Besides, the movement trend of azimuth slows down after 2017, indicating the stress accumulation on both sides of the seismogenic fault zone has reached a certain degree. The first shear strain and EW-direction linear strain in the epicentral area of the Zhangye M_S5.0 earthquake remain steady after 2017, and the surface strain rate decreases gradually after 2016. It is illustrated that there is an obvious deformation loss at the epicentral region three years before the earthquake, indicating that a certain degree of strain energy is accumulated in this area before the earthquake.  相似文献   

垂直地电场观测新技术的数据研究——基于坪城观测点的分析          下载免费PDF全文

周卫东  牛延平  叶青  田野  苏小芸  王娟 《地震工程学报》2020,42(4):914-918

结合同台观测的水平地电场数据,研究坪城垂直地电场观测数据,结果表明:(1)采用固体不极化电极进行垂直地电场观测,同一极距的观测结果基本一致,而铅板电极与固体不极化电极之间存在较大的电位差;(2)垂直地电场日变化形态清晰,长极距测道(A1C1、A2C1和A3C1测道)日变幅为5.85 mV/km左右,短极距(B1C1、B2C1和B3C1测道)日变幅为10.02 mV/km左右;(3)垂直向观测的地电场日变化优势周期在12 h和24 h。  相似文献   

2019年长宁M_S6.0地震邻区分钟采样地电场分析     

王玮铭  谭大诚 《地震》2020,40(3):41-51

2019年6月17日四川宜宾市长宁县发生M_S6.0地震, 分析震中周边600 km内7个地电场台站观测分钟值数据, 获知震前2个月左右红格等6个台站地电场均存在不同方位之间、 同方位长短极距之间的相关系数持续降低, 6月17日这些相关系数基本降至最低, 反映出这6个场地的地电场在此次地震前后发生了非均匀变化; 同时, 这6个台站的地电场优势方位角出现了约45°或90°跃变, 并伴有显著发散或收窄现象。分析表明长宁M_S6.0地震前后, 这6个场地的多种地电场异常现象具有局部场地效应、 时间准同步性。  相似文献   

2011年日本东北大地震（M_W=9.0）震间与震前变形场特征及其对强震预测的启示          下载免费PDF全文

朱守彪 《地球物理学报》2020,63(2):427-439

强震震前(preseismic)动力学过程的研究对于地震预测具有十分重要的意义,但由于观测资料的限制,目前对强震前孕震区力学状态及其演化过程的认识还非常有限.2011年日本东北9.0特大地震(Tohoku-Oki)发生在GPS观测台站最为密集的地区,为研究特大地震震间(interseismic)与震前的变形状态提供了难得的机会.文中将利用日本东北大地震之前连续的GPS观测资料,分别计算震间与震前的速度场与变形场.通过对比分析发现,日本东北地区(Tohoku)震前的应变状态与震间的有很大的不同,震间的变形主要受到太平洋板块向日本海沟北西西向的俯冲挤压作用所控制,其主压应变以近东西向压缩为主,日本东北地区的运动方向与太平洋板块的运动方向大体一致.但是,临近地震前(震前)日本东北地区的运动方向发生了很大变化,震前30天的连续GPS观测结果显示,速度场的优势方向经常变换,间歇性地出现与太平洋板块运动方向相反的情况.这意味着震前孕震区的力学状态发生了很大的改变.这种变化可能与震前破裂成核或慢滑移及慢地震等过程有关,这些过程将加速或促进大地震的发生,从而为大地震的发生准备了力学条件.值得特别强调的是,这些现象都是可以通过直接观测能够发现的大地震之前的异常现象.由此可见,加密GPS站点进行连续观测,寻找震前变形异常区以及探索异常的物理机制对于地震预测预报有重要的科学意义.  相似文献