壳-幔演化和板块俯冲作用过程中的硼同位素示踪

硼同位素是近年来发展起来的一门新兴的稳定同位素地球化学方法。硼有两个稳定同位素 :10 B和11B。硼同位素组成自然界变化十分大 ,δ11B值为 - 37‰～ +58‰。对地幔岩石的硼同位素研究表明 ,原始地幔的δ11B值为 - 10‰± 2‰ ,B的质量分数估算为 (0 2 5± 0 1)×10 -6。相对而言 ,地壳岩石的B含量和δ11B值均较高。由于壳、幔岩石具有不同的B含量和δ11B值 ,硼同位素已被广泛应用于研究壳幔演化和板块俯冲作用过程 ,用于示踪俯冲板块中大洋沉积物和蚀变洋壳在地幔中的循环。     

揭示地质现象的本质与核心--地质作用与时-空结构

对于如何将化学、数学、物理学和复杂性科学与地球科学相结合进行了长期的探索,得出主要结论：“地质作用与时－空结构是地质现象的本质与核心”。并且提出了由浅入深、由表及里、由静态到动态三个层次的表述形式及其相应的理论和方法,即：⑴用平衡、可逆过程热力学研究地质作用并分别用地质数学中的随机过程（马尔科夫过程）和随机场（“地质统计学”）表示时间的空间结构。这是静态的地质作用与时－空结构;（２）用非平衡、不可     

地质作用的自组织临界过程动力学——地质系统在混沌边缘分形生长(下)

笔者对复杂性科学中的自组织临界性、瞬态混沌、混沌边缘和弱混沌四大理论和研究领域就其发展现状和最近动态作系统和深入的剖析后得出结论 ,认为以上四者是对自然界中开放、远离平衡、相互作用的巨大耗散动力学系统的时空演化这个统一事物的本质的面面观。笔者进一步将四者的相互关系归纳成一个重要的命题 :自然界中开放、远离平衡、相互作用的巨大耗散动力学系统的时空演化服从“自组织临界过程动力学” ,并且系统“在混沌边缘分形生长”。地质系统是自然界中的一种既十分重要 ,又异常复杂的开放、远离平衡、相互作用的巨大耗散动力学系统。它具有自组织临界性的内禀基本属性。它的时空行为服从地质作用的自组织临界过程动力学。地质系统位于有序和混沌之间的过渡时空域 ,即混沌边缘 ,其中系统呈规则与混沌运动并存和混合的弱混沌动力学状态 ,并且地质系统在混沌边缘分形生长。将上述命题演绎和整合成一种广泛适用于地质系统的地球科学的复杂性理论 ,名之为 :“地质作用的自组织临界过程动力学———地质系统在混沌边缘分形生长” ,并将其内容归纳成 6部分 :(1)自组织临界性、瞬态混沌、混沌边缘和弱混沌 ,(2 )多组分的耦合与相互作用及其相干与协同 ,(3)演化过程的分形动力学 ,(4 )作用的时空结构 ,(     

地下热水对断裂活动与地震活动的影响研究

利用后郝窑地区的地质勘探资料和怀来地区的数字地震台网观测资料,研究了地下流体（热水）在断裂构造活动及孕震过程中的作用．结果表明,断裂构造在有地下热水参与的地段,断裂两盘剪切应力迅速下降,断层垂直断距明显增加．随着断裂垂直断距的不断增加,该段断层的剪切应力将不断向地下流体未参与的断层两端转移,有可能在断层两端孕育地震．      

赤道东太平洋SST强增温过程特征分析

本文利用太平洋海温距平场资料,对１９８６年以来发生的厄尔尼诺过程的开始时间、发展过程及强度等方面进行了分析。并与历史上的厄尔尼诺过程进行比较,结果表明,９０年代是厄尔尼诺事件的多发期,在１９９１￣９８年的８年中,间连续发生四次厄经诺事件,其中１９９７￣９８年的厄尔尼诺,成为有历史记录以来最强的一次过程。     

New models of interstellar gas–grain chemistry – I. Surface diffusion rates

In recent years it has become evident that large differences can exist between model results of grain-surface chemistry obtained from a rate equation approach and from a Monte Carlo technique. This dichotomy has led to the development of a modified rate equation method, in which a key element is the artificial slowing down of the diffusion rate of surface hydrogen atoms. Recent laboratory research into the surface diffusion rate of atomic hydrogen suggests that atomic hydrogen moves more slowly on grains than heretofore assumed. This research appears to lessen the need for modifications to the rate equation method. Based on the new laboratory work, we have developed appropriate models of gas-phase and grain-surface chemistry in quiescent dense cloud cores to examine the chemical effects of slowing down the rate at which atomic H can scan over dust surfaces. Furthermore, we have investigated the effect of slowing down the rate at which all species can move over grain surfaces.     

辽东湾绥中海岸演变及悬沙分布特征的遥感分析

本文利用辽东湾绥中地区22个年度(1975～1997年)的多时相卫星资料,分析绥中海岸自芷锚湾至狗河口约30km岸线的动态特征、近岸泥沙运动特点和悬浮泥沙的分布状况。所得结果表明,该段海岸近期处于相对稳定状态,近岸悬浮泥沙浓度较小,一般在10～50mg／L范围,是建设大中型海港码头的可选优良岸段。此外,通过遥感图象处理并结合现场调查,分析了近期近岸输沙特征和已建码头突堤堤根岸线淤涨特征,指出绥中沿岸输沙的主要方向是自西向东。     

东海陆架前缘斜坡(冲绳海槽西坡)北部的断块隆脊地貌

东海陆架前缘斜坡(冲绳海槽西坡)北部的断块隆脊,是呈长条形的脊状台式隆起,位于29°30′N-31°10′N;128°00′E-128°20′E之间。其由NNE向链状排列的断块山地组成,且与NNE向的断裂构造相一致,其顶部水深约300m～400m左右。从实测单道地震剖面看,隆脊的东西两侧均有断层出现。隆脊西坡倾向陆架一侧,坡度大,有的地方坡度超过10°;而东侧坡度较缓,仅1°左右,缓倾至海槽西坡坡底,并以沟坎式与冲绳海槽槽底相连。冲绳海槽地区的构造运动,使隆脊地区受到断裂构造的作用。NNE向的大断裂使该隆脊位置的东西两侧断裂下降而中间抬起,加之下部岩浆上侵,显现出链式排列的断块山地,表现为一条长形的断块隆脊构造地貌体。推测该地貌体形成的时期较晚,它是与断层的发生同时期形成的。     

Historical Constraints on Slope Movement Age: a Case Study at Broadway, United Kingdom

The Broadway area of the Cotswolds has been extensively investigated in an attempt to delineate areas of slope instability, including'relict'landslides, which may have been initiated under periglacial climatic conditions. It is, therefore, useful both in terms of the geomorphology and of the understanding of the evolution of the area, to investigate the rates and timing of any reactivation and subsequent movements of landslides in this area. The remains of ridge and furrow cultivation can be seen extensively throughout the Cotswolds. This particular agricultural practice, which documentary evidence suggests dates back to Anglo-Saxon times (approximately 10th century AD), has been disturbed in many places by slope movements. A detailed study of Parish Records and other local his-torical sources has revealed that ridge and furrow cultivation ceased on Parliamentary Enclosure, which in this area, occurred in 1771. Therefore, it is possible to identify patterms of slope movement between these dates. Landslides have been identified by ground mapping and aerial photography, and can be divided into three categories. Firstly, active landslides which are those which have shown evidence of movement during the study period. Secondly, suspended landslides, which show evidence of movement, but have not been observed to move during the study period. In this context, this has been taken to mean landslides, which have shown evidence of movement since 1771. Thirdly, relict landslides which have shown no evidence of movement since 1771 and thus were probably active under a different climatic regime. By incorporating historical data with the geomorphological survey it has been possible to identify areas of potentially difficult ground for engineering geomorphological purposes.     

In-situ rainwater harvesting and gravel mulch combination for corn production in the dry semi-arid region of China

A field study was conducted to determine the effect of a combination of ridge and furrow method of in-situ rainwater harvesting with gravel mulch on corn production, soil moisture storage, and water-use efficiency in the dry semi-arid region of China. Results showed that plastic-covered ridges had an average runoff efficiency (runoff/rainfall) of 87% as compared to 7% for bare ridges, and could generate runoff at a threshold value of 0·8±0·2 mm rainfall. Bare ridges produced runoff only under high intensity rainfall events, and was ineffective for harvesting rainfall in the study area. The plastic-covered ridge and gravel-mulched furrow method of rainwater harvesting was effective in conserving moisture and increasing yield and water-use efficiency. The grain yield in this treatment was 1·9 times that of the conventional flat soil cultivation (control), and the water-use efficiency was 1·8 times that of the control. The good performance of the film-covered surface ridges and gravel-mulched furrows is attributed to the better utilization of light rains, improvement of infiltration in the root zone, and suppression of evaporation losses.