蒙古南戈壁欧玉陶勒盖铜(金)矿床地质特征及其对我国找矿勘查工作的启示

近二十年来,蒙古南戈壁成矿带在寻找大宗金属矿产方面取得丰硕成果,发现了欧玉陶勒盖和查干苏布尔加等与古亚洲洋晚泥盆世岛弧演化有关的大型斑岩型矿床。研究表明:1)欧玉陶勒盖—查干苏布尔加地区在法门期弧岩浆与矿化作用之后,经历了短暂的抬升和剥蚀过程,随后被石炭纪火山-沉积岩所覆盖。两个矿床皆被埋藏于法门期(D_3)—杜内期(C_1)不整合面之下;2)矿床现今出露于石炭纪—二叠纪岩体包围的"天窗"中,矿体能否保存与其上覆岩层遭受的剥蚀程度有关;3)近EW向展布的蒙古南戈壁成矿带在欧玉陶勒盖—查干苏布尔加地区受三叠纪—早白垩世准巴彦断裂左旋走滑运动的影响,局部转变为NE走向,向东可延伸至中国境内东乌旗一带。因此,在中国内蒙古东乌旗地区开展的找矿勘查工作应重点关注法门期(D_3)—杜内期(C_1)不整合之下的晚泥盆世侵入体及其围岩,并在成矿远景区进行相应的区域构造解析研究。     

深埋电极的地电阻率观测研究

首先研究了四极观测系统装置系数与电极埋深的关系;然后给出了点电流源在3层地壳模型的地表和第二层时,电源所在层的电位的解析表达式;最后将天津宝坻地区的电性结构简化成一个3层模型,计算给出了当地表层和基岩中的电阻率出现变化时,在地表和基岩上层开展四极地电阻率观测结果与供电极距和深度的关系.     

用超长基线解算分析汶川地震动态形变特征

以远距离的IGS武汉GPS站为参考站,用超长基线双差瞬时精密定位技术,获取汶川Ms8.0地震震时震区连续GPS站1 Hz动态形变序列。同时以较近距离的雅安站为参考站解算动态形变序列,结果显示,两者的形变结果具有很好的一致性。距离断层较近的郫县、成都、绵阳、中江等站形变较大（形变最大的郫县站最大振幅达1.034 m）;位于震中南侧的邛崃、雅安等站形变较小。利用动态时序的地震波到时和震中距离估计地震波地壳平均速度为3.1 km/s。     

A new model for analyzing nonlinear torsion behavior of concrete filled steel tube columns with rectangular section

An experimental study on concrete filled steel tube columns with rectangular section subjected to compressionflexure-torsion combined action has been carried out. The failure modes and load-deformation hysteretic relations were obtained. Based on the principles of classical material mechanics, the relations between the torsion curvature of the section and the shear strain of the fiber on the section were established. Then the strain distribution on the rectangular section of concrete filled steel tube columns subjected to torsion was analyzed. The three-dimensional refined finite element model was also built, in order to make the precision verification. The matrix forms of the relation between the torsion curvature of the section and the shear strain of the fiber on the section were derived, and introduced into the fiber beam model considering nonlinear torsion effect on the section. The comparison between test results and calculation results showed that the fiber beam model considering nonlinear torsion effect had high modeling efficiency and solution precision for predicting the torsion behavior of concrete filled steel tube columns with rectangular sections, and was suitable for analyzing the dynamic response of various structures subjected to the combined cyclic load caused by the earthquake load.     

Discovery of a Miocene Mafic Dyke from the Western Hills of Beijing and its Geological Implications

Abstract: The present study is the first report of a Miocene mafic dyke from the Dahuichang, in the Western Hills of Beijing. The dyke cuts the fossil-dated Changxindian Formation of Eocene sequences and yields K-Ar ages of 14–15?Ma. The dyke is fine-grained diabase and has 49.84%–50.81% SiO2 and 3.56–3.97% Na2O+K2O, high TiO2 (1.65%–1.93%) and MgO (7.36%–9.85%), and low K2O (<1.22%) contents, with Na2O>K2O and slightly varied magnesium numbers (Mg#=55.54–62.74). In trace elements geochemistry, the dyke is very similar to the Miocene basalts from Jining and Hanuoba. The enrichment of light rare earth elements ([La/Yb]N=5.03–6.12) and large ion lithophile elements (LILEs?), no negative Eu anomalies, relatively high Cr (265–326 ppm) and Ni (155–262 ppm), and almost constant V concentrations (194–213 ppm) reveal that the composition close to the primary basaltic magma from ?an enriched-mantle source, with little crustal contamination and fractional crystallization. The basaltic magma was possibly derived from the upwelling asthenosphere mantle beneath eastern China during the Miocene lithospheric thinning.     

The nonlinear hydro-climatic process in the Yarkand River, northwestern China

Based on the hydrologic and meteorological data in the Yarkand River Basin during 1957–2008, the nonlinear hydro-climatic process was analyzed by a comprehensive method, including the Mann–Kendall trend test, wavelet analysis, wavelet regression analysis and correlation dimension. The main findings are as following: (1) The annual runoff, annual average temperature and annual precipitation showed an increasing trend during the period of 1957–2008, and the average increase extent in runoff, temperature and precipitation was 2.234 × 10⁸ m³/10 year, 0.223 °C/10 year, and 4.453 mm/10 year, respectively. (2) The nonlinear pattern of runoff, temperature and precipitation was scale-dependent with time. In other words, the annual runoff, annual average temperature and annual precipitation at five time scales resulted in five patterns of nonlinear variations respectively. (3) Although annual runoff, annual average temperature and annual precipitation presented nonlinear variations at different time scales, the runoff has a linear correlation with the temperature and precipitation. (4) The hydro-climatic process of the Yarkand River is chaotic dynamic system, in which the correlation dimension of annual runoff, annual average temperature and annual precipitation is 3.2118, 2.999 and 2.992 respectively. None of the correlation dimensions is an integer, and it indicates that the hydro-climatic process has the fractal characteristics.     

公元前7年内蒙古包头地区8级地震的初步研究

公元前7年11月11日(汉成帝绥和二年九月丙辰)地震, 由于历史文献记载的不确定性, 长期存在分歧, 也没有学者开展过调查研究, 中国地震目录均未收入. 考古发现包头市麻池周边汉代部分木椁墓中木椁四周填塞的碎砖瓦陶片及文字瓦当, 是房屋毁坏以后的建筑垃圾和日用陶器残片的混合物, 这些房屋是在公元前52年(甘露二年)到公元前33年(竞宁元年)以后在麻池古城(汉五原郡)建成的. 上述房屋的毁坏发生在西汉晚期的墓葬稍前. 房屋毁坏的原因, 可排除自然因素、 战争及人为破坏, 更可能是由于突发性的地震灾害所致. 公元前7年地震正好发生在这一时期, 并使北边郡国30余处坏城郭, 凡压杀400余人. 根据木椁四周填塞碎砖瓦陶片的汉墓分析, 麻池古城房屋、 殿堂遭受严重破坏, 死亡人数达200人以上, 地震及其它天灾人祸, 使麻池古城逐渐衰退, 最后荒废. 结合大青山山前断裂所形成的距今2 000年前的地震形变带遗迹综合分析, 公元前7年11月11日地震宏观震中在麻池一带, 震中烈度为Ⅹ度, 震级达8级, 命名为内蒙古包头8级地震.      

含富锂(钾)卤水断陷盆地的深部构造特征: 以中国华南吉泰盆地为例

中国华南吉泰盆地在白垩纪?古近纪发育大量蒸发岩,其中含富锂卤水矿床,由于盆地深部构造特征认识不清,导致富锂卤水矿勘查评价明显滞后.基于盆地东北部泰和坳陷二维地震数据和钻孔资料,经过精细保幅处理和综合构造解释,总结了含富锂卤水矿断陷盆地的深部构造特征.地震剖面和构造属性表明,盆地深部发育错断白垩系的NE-SW走向、NW倾...     

Spatial and temporal changes in flooding and the affecting factors in China

Spatial and temporal changes in flood events in China are becoming increasingly important due to the rapid climate warming that is occurring. This study was conducted to consider changes in flood events and the factors affecting such changes. To accomplish this, China was divided into natural and social-economic flood regions: north China, northwest China, northeast China, southwest China, central China, east China, south China, and Taiwan, Hong Kong and Macau. Spatial and temporal changes in flood patterns were rebuilt during 1980?C2009, and Fast Fourier Transform Filtering was then employed to stimulate the changes in floods during this period. The factors affecting flooding were then analyzed quantitatively. The results showed that, based on the time series for China as a whole, flooding was more serious during 1990?C1999 than 1980?C1989 and 2000?C2009. However, in different regions, the trends in flooding differed greatly. Based on spatial changes, the areas hardest hit by floods were northeast China in the 1980s, northeast China, central China and east China in the 1990s, and central China after 2000. In China, the main flood-affecting factors were meteorological, ecological, population, water conservation facilities, and policy factors. However, the main affecting factors differed by region. Overall, the complex spatial and temporal features of flood variations and various affecting factors demand proper national and regional governmental action in the face of the changing flood patterns in China. The results of the present study provide valuable information to flood policymakers and flood disaster researchers.     

Integrated provenance analysis of a convergent retroarc foreland system: U–Pb ages,heavy minerals,Nd isotopes,and sandstone compositions of the Middle Magdalena Valley basin,northern Andes,Colombia

Sediment provenance analysis remains a powerful method for testing hypotheses on the temporal and spatial evolution of uplifted source regions, but issues such as recycling, nonunique sources, and pre- and post-depositional modifications may complicate interpretation of results from individual provenance techniques. Convergent retroarc systems commonly contain sediment sources that are sufficiently diverse (continental magmatic arc, fold–thrust belt, and stable craton) to enable explicit provenance assessments. In this paper, we combine detrital zircon U–Pb geochronology, heavy mineral identification, Nd isotopic analyses, conventional sandstone petrography, and paleocurrent measurements to reconstruct the clastic provenance history of a long-lived sedimentary basin now exposed in an intermontane zone of the northern Andean hinterland of Colombia. The Middle Magdalena Valley basin, situated between the Central Cordillera and Eastern Cordillera, contains a 5–10 km-thick succession of Upper Cretaceous to Quaternary fill. The integrated techniques show a pronounced change in provenance during the Paleocene transition from the lower to upper Lisama Formation. We interpret this as a shift from an eastern cratonic source to a western Andean source composed of magmatic-arc rocks uplifted during initial shortening of the Central Cordillera. The appearance of detrital chloritoid and a shift to more negative ε_Nd(t=0) values in middle Eocene strata of the middle La Paz Formation are attributed to shortening-related exhumation of a continental basement block (La Cira–Infantas paleohigh), now buried, along the axis of the Magdalena Valley. The diverse provenance proxies also show distinct changes during middle to late Eocene deposition of the Esmeraldas Formation that likely reflect initial rock uplift and exhumation of the fold–thrust belt defining the Eastern Cordillera. Upsection, detrital zircon U–Pb ages and heavy mineral assemblages for Oligocene and younger clastic deposits indicate that the Mesozoic sedimentary cover of the Eastern Cordillera was recycled during continued Cenozoic shortening. Our multidisciplinary provenance study refines the tectonic history of the Colombian Andes and demonstrates that uncertainties related to sediment recycling, nonunique sources, source heterogeneity, and climate in interpreting provenance data can be minimized via an integrated approach.