Prolonged postcollisional shoshonitic magmatism in the southern Svecofennian domain – a case study of the Åva granite–lamprophyre ring complex     

Olav Eklund  Alexey Shebanov 《Lithos》2005,80(1-4):229-247

The Åva ring complex is one of four Paleoproterozoic postcollisional shoshonitic ring complexes in southwestern Finland. It is composed of ring dykes of K-feldspar megacryst-bearing granite, mingled in places with a shoshonitic monzonite, and lamprophyre dykes crosscutting all the rocks in a radial pattern. A survey was undertaken to trace the magma chamber beneath the ring complex to date it and measure some intensive parameters to clarify the crystallisation conditions at depth before the granite was emplaced in the upper crust. Mineral separates were extracted from the core zones of K-feldspar megacrysts in the granite, heavy mineral fractions (including zircons) from these separates were used for P-T assessment and age determinations, and the results were compared to data obtained from bulk rock samples. It appears that magma differentiation took place in a midcrustal magma chamber (at 4 to 7 kbar) possibly 30 Ma before the emplacement of the ring complex in the upper crust (deep assemblage 1790 Ma, shallow assemblage 1760 Ma). Relatively high activity of the alkalies and a low oxygen fugacity characterised the midcrustal chamber. The juvenile Svecofennian crust was invaded by shoshonitic magmas from an enriched lithospheric mantle over a long period of time. Some of these magmas were stored and differentiated in the middle crust before transportation to the upper crust. The results also show that coarse-grained granites may provide evidence for several magmatic evolutionary episodes, e.g., differentiation and crystallisation in different environments prior to final emplacement.  相似文献   

内蒙古大青山-乌拉山地区孔兹岩系的早期变质地层结构——下地壳近水平顺层滑脱变形的产物   总被引：4，自引：0，他引：4  

徐仲元刘正宏  杨振升 《地层学杂志》2005,29(11):423-432

近年来孔兹岩系作为高级变质岩区一套特征性的变质沉积岩石组合而受到广泛关注，但其变质地层结构及其相关的构造作用和构造样式还不为人所了解。通过对内蒙古大青山一乌拉山地区以孔兹岩系发育为特征的高级变质杂岩的研究发现，区内孔兹岩系自下而上由3个岩石地层单位组成：榴云片麻岩岩组、透辉片麻岩岩组和大理岩岩组，表现出由细碎屑沉积-碎屑沉积和钙质化学沉积的混合物-镁质碳酸盐组成的沉积旋回。这些变质地层不仅遭受到具有近等温降压顺时针P-T演化特征的麻粒岩相变质作用的改造，同时，还遭受到近水平顺层滑脱变形构造、穹-褶构造和近东西向陡倾叶理带这三种构造形式为主的多期变形的改造。由此，这些变质地层在空间上多以不规则条带状、不规则团块状或透镜状形式出露，同时，各地层单位在空间上具有“犬牙交错，参差产出”，“岩层缺失，隔层相触”的特征。研究结果表明，区内孔兹岩系目前的产出状态及“犬牙交错，参差产出”的特征是穹-褶构造尤其是近东西向陡倾叶理带叠加改造的结果，在消除其改造的影响后可以确定，由于近水平顺层滑脱变形改造的结果，这些变质地层发生“岩层缺失，隔层相触”，在空间上表现为以近水平的长轴近东西向的扁豆体堆叠而成的早期变质地层结构，这是高级变质地层所特有的变质地层结构。  相似文献   

EXPLORATION ENGINEERING     

《Abstract of Chinese Geological Literature》2014,(3)

正20141864 Deng Mengchun(Institute of Exploration Technology,CAGS,Chengdu 611734,China);Huang Shenghui Rock Sample Collection and Division Technologies for Air Reverse Circulation Sampling Drilling(Exploration Engineering,ISSN1672-7428,CN11-5063/TD,40(7),2013,p.73-76,80,16 illus.,5 refs.)  相似文献   

复杂卫星图像中的小目标船舶识别   总被引：1，自引：1，他引：0  

姚红革  王诚  喻钧  白小军  李蔚 《遥感学报》2020,24(2):116-125

船舶作为海上的重要目标,实现对船舶自动识别有重要的意义。针对卫星图像中云雾、海岸背景等复杂海情对船舶识别带来的干扰,以及小目标船舶高漏检率问题,本文提出一种多尺度深度学习模型训练策略,在此基础上构建了一种船舶识别的深度学习网络,该网络可分为多尺度训练、特征提取、生成目标建议区域、船舶分类这4个部分。首先,采用多尺度的训练策略,将多尺度的船舶样本送入网络中进行训练,这样在训练样本中加入了大量小目标船舶的样本,使网络充分提取到小目标船舶的特征;其次,通过卷积神经网络对目标船舶进行特征自适应提取;然后,目标区域建议网络可依据卷积神经网络提取到的特征,在图像中找到感兴趣目标区域,即框定船舶的位置;最后,通过多个全连接层的组合,将高维特征映射到一个4元组中,再运用分类函数输出每一类船舶的概率值,概率值最大的则为该船舶的类别。同时为解决云雾遮挡和海岸背景的干扰,采用了一种负样本增强学习的方法,在样本数据集中加入了大量只含有云雾和海岸背景的图片,进行负样本扩充,增强网络模型对云雾及海岸背景的特征学习能力,以此解决复杂海情的影响。实验结果表明,所提方法有效解决了复杂海情条件下的船舶识别难,以及小目标船舶识别难的问题,实现了复杂海情条件下的船舶识别。同时,与现有成熟的深度学习目标识别算法相比,本文算法的精确度和召回率分别提升了6.98%和18.17%,所训练的模型具有良好的泛化能力和鲁棒性。  相似文献   

Torsional dynamic response of a large‐diameter pipe pile in viscoelastic saturated soil     

Changjie Zheng  Hanlong Liu  Xuanming Ding  Yaru Lv 《国际地质力学数值与分析法杂志》2014,38(16):1724-1743

An analytical solution is developed in this paper to investigate the dynamic response of a large‐diameter end‐bearing pipe pile subjected to torsional loading in viscoelastic saturated soil. The wave propagation in saturated soil and pile are simulated by Biot's two‐phased linear theory and one‐dimensional elastic theory, respectively. The dynamic equilibrium equations of the outer soil, inner soil, and pile are established. The solutions for the outer and inner soils in frequency domain are obtained by Laplace transform technique and the separation of variables method. Then, the dynamic response of the pile is obtained on the basis of the perfect contacts between the pile and the outer soil as well as the inner soil. The results in this paper are compared with that of a solid pile in elastic saturated soil to verify the validity of the solution. Furthermore, the solution in this paper is compared with the classic plane strain solution to verify the solution further and check the accuracy of the plane strain solution. Numerical results are presented to analyze the vibration characteristics and illustrate the effect of the soil parameters and the geometry size of the pile on the complex impedance and velocity admittance of the pile head. Finally, the displacement of the soil at different depth and frequency is analyzed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

基于分段副产物瞬时选择性的反应器网络综合     

胡仰栋  周勇  伍联营 《中国海洋大学学报(自然科学版)》2020,50(3):61-66

针对第三类反应体系的反应器网络综合问题,提出将串联反应以反应物到目的产物的反应步数为依据的新分段策略。通过比较不分段目的产物、不分段目的产物和中间产品、分段副产物和分段目的产物这四种不同的瞬时选择性,提出以分段副产物瞬时选择性为参数,以其对关键组分浓度或转化率的导数为依据选择各阶段最合适的反应器,以目的产物总选择性最大为目标采用遗传算法优化反应器网络。通过三个实例验证了本文所建立方法在解决复杂反应反应器网络综合问题的有效性,且本方法同样适用于简单反应体系。  相似文献   

福建省复杂地形下旬平均气温分布式模拟     

李威鹏  邱新法  曾燕  施国萍  徐金勤  王丹丹 《热带地理》2019,39(2):229-236

为建立高时空分辨率的福建省复杂地形下气温栅格数据集，利用福建省及其周边33个常规气象站观测资料，基于数字高程模型（DEM）数据，综合考虑海拔、太阳总辐射、地表长波有效辐射对旬平均气温的影响，模拟了福建省复杂地形下旬均温的空间分布。结果表明：1）常规站验证结果显示：各旬气温绝对误差平均值（MAE）最小为0.46℃，最大为2.3℃，全年平均为0.87℃；加密站验证结果显示，MAE最大为2.3℃，最小0.5℃，全年平均为0.96℃。2）模拟结果能反映旬均温的宏观分布规律与局地细节特征。宏观范围内，旬均温受纬度影响较大，由北至南气温逐渐升高，沿海地区旬均温整体高于内陆，山区旬均温明显较低；局地范围内，各坡向上气温差异显著，海拔越高、坡度越大，差异越明显；地形因子对旬平均温的影响具有季节差异，具体表现为冬季时地形因子对旬均温的影响最大，秋季次之，春夏季节中地形因子对旬均温的影响最弱。  相似文献   

Displacement analytical prediction of shallow tunnel based on unified displacement function under slope boundary     

Fanchao Kong  Dechun Lu  Xiuli Du  Chenpeng Shen 《国际地质力学数值与分析法杂志》2019,43(1):183-211

For slope condition of ground surface, the asymmetrical deformation about the vertical center line and the horizontal center line of the tunnel cross section can be formed. A unified displacement function expressed by the Fourier series is presented to express the asymmetrical deformation of the tunnel cross section. Five basic deformation modes corresponding to the expansion order 2 are a complete deformation mode to reflect deformation behaviors of the tunnel cross section under slope boundary. Such this complete displacement mode is implemented into the complex variable solution for analytically predicting tunneling-induced ground deformation under slope boundary. All of these analytical solutions are verified by good agreements of the comparison between the analytical solutions and finite element method results. A parameter study is carried out to investigate the influence of deformation modes of the tunnel cross section, geometrical conditions of the tunnel and the slope angle, and “Buoyancy effect” on the displacement field. Finally, the proposed method is consistent with measured data of the Hejie tunnel in China qualitatively. The presented solution can provide a simplified indication for evaluating the ground deformation under slope condition of ground surface.  相似文献   

Phase equilibria modelling and LASS monazite petrochronology: P–T–t constraints on the evolution of the Priest River core complex,northern Idaho          下载免费PDF全文

L. M. Stevens  J. A. Baldwin  J. M. Cottle  A. R. C. Kylander‐Clark 《Journal of Metamorphic Geology》2015,33(4):385-411

Phase equilibria modelling, laser‐ablation split‐stream (LASS)‐ICP‐MS petrochronology and garnet trace‐element geochemistry are integrated to constrain the P–T–t history of the footwall of the Priest River metamorphic core complex, northern Idaho. Metapelitic, migmatitic gneisses of the Hauser Lake Gneiss contain the peak assemblage garnet + sillimanite + biotite ± muscovite + plagioclase + K‐feldspar ± rutile ± ilmenite + quartz. Interpreted P–T paths predict maximum pressures and peak metamorphic temperatures of ~9.6–10.3 kbar and ~785–790 °C. Monazite and xenotime ²⁰⁸Pb/²³²Th dates from porphyroblast inclusions indicate that metamorphism occurred at c. 74–54 Ma. Dates from HREE‐depleted monazite formed during prograde growth constrain peak metamorphism at c. 64 Ma near the centre of the complex, while dates from HREE‐enriched monazite constrain the timing of garnet breakdown during near‐isothermal decompression at c. 60–57 Ma. Near‐isothermal decompression to ~5.0–4.4 kbar was followed by cooling and further decompression. The youngest, HREE‐enriched monazite records leucosome crystallization at mid‐crustal levels c. 54–44 Ma. The northernmost sample records regional metamorphism during the emplacement of the Selkirk igneous complex (c. 94–81 Ma), Cretaceous–Tertiary metamorphism and limited Eocene exhumation. Similarities between the Priest River complex and other complexes of the northern North American Cordillera suggest shared regional metamorphic and exhumation histories; however, in contrast to complexes to the north, the Priest River contains less partial melt and no evidence for diapiric exhumation. Improved constraints on metamorphism, deformation, anatexis and exhumation provide greater insight into the initiation and evolution of metamorphic core complexes in the northern Cordillera, and in similar tectonic settings elsewhere.  相似文献   

COAL GEOLOGY     

《Abstract of Chinese Geological Literature》2014,(3)

正20141574 Chen Hao(Exploration and Development Research Institute,Daqing Oilfield Company,Daqing 163712,China)High-Resolution Sequences and Coal Accumulating Laws in Nantun Formation of Huhe Lake Sag(Petroleum GeologyOilfield Development in Daqing,ISSN1000-3754,CN23-1286/TQ,32(4),2013,p.15-19,5 illus.,15 refs.)Key words:coal accumulation regularity,coal  相似文献