Two geomagnetic excursions during the Brunhes chron recorded in Chinese loess-palaeosol sediments

Detailed palaeomagnetic integrated with rock magnetic studies have been carried out on a loess-palaeosol sequence in Baoji, Shaanxi province, southern Chinese Loess Plateau. For most samples stepwise thermal demagnetization revealed two well-defined magnetization components. A low-temperature component (LTC), which was isolated between 100 and 200 °C, is consistent with the present geomagnetic field direction. A high-temperature component (HTC), which was isolated between 250 and 620–680 °C, shows normal, reversed or transitional polarities. Our new magnetostatigraphy revealed two distinct geomagnetic excursions recorded in loess unit of L5 and palaeosol unit of S7, respectively, and the Matuyama-Brunhes (M-B) polarity boundary in loess unit of L8. Rock magnetic experiments demonstrated that the specimens from the excursion zones have the same magnetic properties as those from the Brunhes normal or Matuyama reversed polarity zones. Measurements of anisotropy of magnetic susceptibility (AMS) showed that the sediments have primary sedimentary fabrics. Based on the palaeoclimatological and magnetostratigraphic age models, the middle Brunhes excursion in loess L5 is dated at 413–433 ka, and the early Brunhes excursion is estimated to occur 23–33 ka after the M-B reversal. Comparing with previously reported geomagnetic excursions in the Brunhes chron, the middle Brunhes excursion (L5) is likely global. For the early Brunhes excursion (S7), we need further studies to examine its global occurrence.     

大兴安岭富林-兴隆沟一带金及多金属成矿条件分析

研究区位于额尔古纳地块的额木尔山中间隆起带东部边缘塔河过渡带内，砂金资源极为丰富，成矿条件十分优越，具有良好的找矿远景.通过对区内地层、岩浆岩、构造、地球物理、地球化学、遥感等综合信息进行分析，初步总结了区内成矿规律，指出找矿的有利部位，并对区内找矿关键作了简单探讨，为区内下步找矿工作取得突破性进展提供了一定的思路.     

遥感图像相关性及其熵计算

针对新一代遥感图像辐射分辨率提高的情况,设计了计算双字节联合熵的算法,讨论了量化级数对信息熵计算的影响,并考虑信源的记忆性质,对多波段图像讨论削减像元之间相关性及多波段间相关性的方法,进而对接近无记忆信源的图像数据进行联合熵的计算和分析,取得更为合理的评价结果.所发展的方法适用于多波段影像融合中最适宜的波段选择和质量评估.     

主分量与广东北江年最大流量预测

提出一种应用因子场的主分量建立北江长期洪水预报模型的方法,对发生暴雨洪水有重大影响的500hPa高度场和太平洋海温场作主分量分析,提取其含高信息量的主分量作为预报因子,通过相关和逐步回归计算建立模型.详细分析了用该模型对珠江的重要支流——北江年最大流量的拟合和预测,用该模型对北江流域年最大流量的预测表明,模型是有效的,效果较好,对较大洪水年的拟合效果尤其令人满意.     

Recent Development in Simultaneous Multi-Element Determination of the Platinum Group Elements and Gold in Geological and Environmental Samples

In recent years, the modern methods of multi-element analysis of precious metals have attracted wide attention in scientific research and industry. The application and development in the decomposition of samples, separation and enrichment, and modern instrumental analysis of the platinum-group elements (PGEs) and gold in geological and environmental samples have been reviewed. Finally, the tendency of analysis of precious metals is also prospected.     

Elastic and inelastic drift performance optimization for reinforced concrete buildings under earthquake loads

This paper presents an effective optimization technique for the elastic and inelastic drift performance design of reinforced concrete buildings under response spectrum loading and pushover loading. Attempts have been made to develop an automatic optimal elastic and inelastic drift design of concrete framework structures. The entire optimization procedure can be divided into elastic design optimization and inelastic design optimization. Using the principle of virtual work, the elastic drift response generated by the response spectrum loading and the inelastic drift response produced by the non‐linear pushover loading can be explicitly expressed in terms of element sizing design variables. The optimization methodology for the solution of the explicit design problem of buildings is fundamentally based on the Optimality Criteria approach. One ten‐story, two‐bay building frame example is presented to illustrate the effectiveness and practicality of the proposed optimal design method. While rapid convergence in a few design cycles is found in the elastic optimization process, relatively slow but steady and smooth convergence of the optimal performance‐based design is found in the inelastic optimization process. Copyright © 2004 John Wiley & Sons, Ltd.     

从历史记录看地震与火山喷发关系

史料记载表明，五大连池火山1720~1721年喷发期间有大量地震活动.本文从描述这些地震活动的文字记录入手，并结合国际火山地震研究的新成果，探讨了地震类型及地震与火山喷发关系，指出震群是火山喷发的重要前兆指标，强调火山地震的监测对火山喷发预报的意义.      

滇西龙川江盆地中南部砂岩型铀矿成矿特征及成因探讨

研究了龙川江盆地中南部的沉积特征、构造特征及含矿岩系特征，提出铀成矿与构造演化中的2个沉积间断面关系密切。通过对龙川江盆地中南部铀矿化特征的研究，在382矿床内发现了沥青铀矿、铀黑和磷钙铀矿，在381矿床发现了超显微状放射性矿物，并根据龙川江盆地中南部382矿床成矿年龄的研究，提出了龙川江盆地中南部铀矿化的多阶段成因。     

广东凡口铅锌(银)矿床成矿流体来源研究

在已有研究成果的基础上 ,通过对矿物流体包裹体化学成分和氢氧同位素地球化学的研究 ,认为凡口矿区成矿期热液为多源混合流体 ,其来源包括建造水和岩浆水。这种混合流体的加热驱动与岩浆事件有关。     

Study on Active Faults in Quaternary Unconsolidated Sediments by Microstructural Method

Active faults in Quaternary unconsolidated sediments are important indicators to determine paleoearthquake events,They can be studied by macroscopic geological survey,but some problems have been encountered,such as invisible active faults.The authors found an approach to solve these problems by microstructural observation.Firstly,oriented original-state samples of Quaternary Unconsolidated sediments in active fault zones are collected.Secondly,the samples are consolidated in laboratory.Thirdly,microstructureal slides are gound in three-dimension coordinate system.Lastly,microstructures are observed in the microscopic field.By this method,the movement properties of active faults can be determined in lack of the support of macroscopic data.The invisible faults in Quaternary unconsolidated sediments can be found and described.The mechanisms of die-out faults can be also studied.oreover,the boundaries between different unconsolidated sediments in engineering sites can be studied to judge whether they are active faults or not.