冀北坝上地区深部地质构造特征及其对火山活动和铀成矿的控制作用     

桑吉盛  李利权  田万文  张振强 《铀矿地质》1994,(2)

冀北坝上地区位于华北地台北缘。其深部地质构造有两个显著特征：一是全区性的莫霍面下拗，地壳增厚；二是软流圈部分伸入到下岩石图上部，造成局部地区地幔上隆，地壳减薄。火山喷发形成的沽源火山盆地和大滩火山盆地与两个地幔上隆，地壳减薄区，上下相互对应。铀矿床（点）沿地幔隆起周边构造活动带规律性分布。上述两事实有力地证明了深部地质构造对中新生代火山活动和铀成矿的控制作用。沿地幔隆起周边构造活动带是今后寻找铀及多金属矿产的有利地段。  相似文献   

阻塞结构对近海台风异常路径影响的数值试验   总被引：2，自引：0，他引：2       下载免费PDF全文

解以扬  徐祥德 《应用气象学报》1994,5(1):104-108

采用数值试验方法，研究了近海台风移动路径对环境动力因子的敏感性特征。数值模拟结果表明，台风北侧阻塞高压结构的变化，对近海台风路径异常现象的发生有显著影响。  相似文献   

当前反射地震学研究中的问题浅析   总被引：3，自引：4，他引：3  

马在田 《地球物理学进展》1994,9(1):84-89

反射地震学作为地震学应用于国民经济建设的分支学科取得了巨大的成功。它在矿产资源勘探、工程建设与环境、自然灾害预测等各种领域发挥了不可替代的作用，特别是在能源开发中功不可殁。另一方面，反射地震学在广泛的工业应用中全面地完善和发展了地震学的理论、方法和技术。时至今日，反射地震学的发展已经从经典理论方法的研究走向更加与客观介质密切相关的深层次研究新阶段，这些问题是，反射地震学从单纯的构造研究走向地层岩性研究，与此有关的是从偏移构造成像步入层析成像、利用单波单分量数据转向应用多波多分量数据、假设地层为固体弹性介质转向双相孔隙介质、各向同性研究转向各向异性研究以及经典的一些方法技术与现代新技术同时使用等。本文对这些方面的研究现状进行概要的分析。  相似文献   

吉林省西林河金矿构造特征及找矿方向   总被引：2，自引：0，他引：2  

赵凤桐  梁宜林 《吉林地质》1995,14(3):60-68

对矿区划分了太古宙、元古宙、中生代和新生代四个构造层；整个矿区为一棋盘格子形构造体系；主干构造形迹为由东、中、西三个韧性挤压剪切带，金矿的主要成矿构造是西部韧性挤压、剪切带，主要找矿方向为西带Ｆ６及其派生的近南北向剪切断裂群。  相似文献   

洋面冷锋的三维数值模拟──潜热释放对冷锋结构的影响     

俞小鼎  ERichar  RRosset 《气象学报》1995,53(3):319-327

通过比较一次洋面冷锋过程的干、湿三维模拟结果，揭示潜热释放对冷锋结构的影响。结果表明：由于潜热释放的作用，冷锋区的温度梯度和风矢量的气旋性切变大大地加强了，冷锋附近的涡度场和垂直速度场呈现出更多的更加紧密的中尺度结构；锋面非地转直接环流在湿模拟中比在干模拟中发展得更加充分并且具有更高的组织性；潜热加热倾向于增加锋面环流的强度，尤其是其上升支的强度。研究表明，潜热释放过程是形成冷锋前沿上方低层大气中狭窄强上升气流区的关键因素之一。  相似文献   

中国东北地区新生代火山岩的年代学研究   总被引：36，自引：19，他引：36  

刘嘉麒 《岩石学报》1987,3(4)

用常规K-Ar、~(40)Ar-~(39)Ar、~(14)C等方法系统测定了东北地区新生代火山岩的年龄,获得近百个有效年龄数据。其精度和准确度都很高,与地质背景相当吻合。对于玄武岩中超镁铁质岩色体也进行了年龄测定尝试、发现包体中含继承氩,并可能存在~(36)Ar过剩。在阶段加热过程中,样品中氩的释放有两个高峰,一个在低温阶段(450—620℃),另一个在高温阶段(>1000℃),约50％的放射成因~(40)Ar在低温阶段释放。  相似文献   

Rapid deglaciation as an initiator of volcanic activity: An hypothesis     

Kevin Hall 《地球表面变化过程与地形》1982,7(1):45-51

Volcanic activity on sub-Antarctic Marion Island is found to have occurred only during the interglacials. The present volcano distribution is associated with a radial and peripheral fault system, the location of which appears to be related to the former glacier distribution. An hypothesis is presented suggesting that the faulting is a result of deglaciation and that the specific location of the faults is due to the differential stresses occurring between ice-covered and ice-free areas during isostatic uplift. The faulting initiates volcanism due to the location of the island within a volcanic region.  相似文献   

Three-dimensional petrographical investigations on borehole rock samples: a comparison between X-ray computed- and neutron tomography     

P. Christe  M. Bernasconi  P. Vontobel  P. Turberg  A. Parriaux 《Acta Geotechnica》2007,2(4):269-279

Technical difficulties associated with excavation works in tectonized geological settings are frequent. They comprise instantaneous and/or delayed convergence, sudden collapse of gallery roof and/or walls, outpouring of fault-filling materials and water inflows. These phenomena have a negative impact on construction sites and their safety. In order to optimize project success, preliminary studies on the reliability of rock material found on site are needed. This implies in situ investigations (surface mapping, prospective drilling, waterflow survey, etc.) as well as laboratory investigations on rock samples (permeability determination, moisture and water content, mineralogy, petrography, geochemistry, mechanical deformation tests, etc.). A set of multiple parameters are then recorded which permit better insight on site conditions and probable behavior during excavation. Because rock formations are by nature heterogeneous, many uncertainties remain when extrapolating large-scale behavior of the rock mass from analyses of samples order of magnitudes smaller. Indirect large-scale field investigations (e.g. geophysical prospecting) could help to better constrain the relationships between lithologies at depth. At a much smaller scale, indirect analytical methods are becoming more widely used for material investigations. We discuss in this paper X-ray computed tomography (XRCT) and neutron tomography (NT), showing promising results for 3D petrographical investigations of the internal structure of opaque materials. Both techniques record contrasts inside a sample, which can be interpreted and quantified in terms of heterogeneity. This approach has the advantage of combining genetic parameters (physico-chemical rock composition) with geometric parameters resulting from alteration or deformation processes (texture and structure). A critical analysis of such 3D analyses together with the results of mechanical tests could improve predictions of short- and long-term behavior of a rock unit. Indirect methods have the advantage of being non-destructive. However, as it is the case with large-scale geophysical surveying, XRCT and NT are affected by several error factors inherent to the interaction of a radiation modality (X-ray or neutron beam) with the atomic structure of the investigated materials. Recorded signals are therefore in particular cases not artifact-free and need to be corrected in a subsequent stage of data processing.  相似文献   

Effect of agricultural land use on the chemistry of groundwater from basaltic aquifers, Jeju Island, South Korea   总被引：2，自引：0，他引：2  

Dong-Chan Koh  Kyung-Seok Ko  Yongje Kim  Seung-Gu Lee  Ho-Wan Chang 《Hydrogeology Journal》2007,15(4):727-743

Geochemical processes were identified as controlling factors of groundwater chemistry, including chemical weathering, salinization from seawater and dry sea-salt deposition, nitrate contamination, and rainfall recharge. These geochemical processes were identified using principal component analysis of major element chemistry of groundwater from basaltic aquifers in Jeju Island, South Korea, a volcanic island with intense agricultural activities. The contribution of the geochemical processes to groundwater chemistry was quantified by a simple mass-balance approach. The geochemical effects due to seawater were considered based on Cl contributions, whereas the effects due to natural chemical weathering were based on alkalinity. Nitrogenous fertilizers, and especially the associated nitrification processes, appear to significantly affect groundwater chemistry. A strong correlation was observed between Na, Mg, Ca, SO₄ and Cl, and nitrate concentrations in groundwater. Correspondingly, the total major cations, Cl, and SO₄ in groundwater were assessed to estimate relative effect of N-fertilizer use on groundwater chemistry. Cl originates more from nitrate sources than from seawater, whereas SO₄ originates mostly from rainwater. N-fertilizer use has shown the greatest effect on groundwater chemistry, particularly when nitrate concentrations exceed 6–7 mg/L NO₃–N. Nitrate contamination significantly affects groundwater quality and 18% of groundwater samples have contamination-dominated chemistry.  相似文献   

Recent Geochemical Variation of the Hot-Spring Gases from the Tianchi Volcano, Changbai Mountains, Northeast China   总被引：1，自引：0，他引：1  

Gao Ling 《中国地震研究》2007,21(2):179-188

Recent fluid monitoring work shows that the contents of mantle-derived CO_2,He and CH_4 increased anomalously in 2002 and 2003. The 3He/4He ratio of the deep-fault-type Jinjiang hot springs increased highly anomalously in 2003, and then decreased in 2004. The 3He/4He ratio from the thermal-reservoir-type Changbaijulong hot springs increased slowly in 2003, and the increase continued in 2004. The mantle-derived He content of the He released from the Changbaijulong springs increased obviously in 2004. The anomaly of the released gases and the isotopic He was consistent with the trends of seismic activities in the Tianchi volcanic area between 2002 and 2004. The abnormal release of the Jinjiang hot springs apparently decreased after the seismic activities ceased in the second half of 2004, while the abnormal release from the Changbaijulong increased significantly after these seismic activities. It shows that the abnormal release of magmas-derived gases from the thermal-reservoir-type springs lags behind that of the deep-fault-type springs. These characteristics may be of great significance for identifying deep magmatic activity and predicting volcanic earthquakes in the future.  相似文献