西北地区的自然环境类型

自然环境区划是国土规划的重要基础,是自然环境综合特征的基本反映。以西北地区的气候分区、地貌分区、植被分区(生态分区)为基础,将西北地区的自然环境类型划分为5个自然分区:阿尔泰—准噶尔区,塔克拉玛干—毛乌素沙漠区,青藏高原东北缘区,黄土高原区,秦巴山地与汉水谷地区。这5个区有完全不同的自然环境特征和资源优势特征,因而开发对策和环境对策是不同的,应予以分别对待。正确认识各区的自然环境特征,才能实现西北地区社会经济及环境的可持续发展。     

西北区东部一次大暴雨过程的湿位涡诊断与数值模拟

利用绝热、无摩擦大气湿位涡守衡理论和NCEP(1°×1°)再分析资料,对我国西北区东部2005年7月1~2日大暴雨过程进行了分析。结果表明:700 hPa上副热带高压西侧强西南气流北上,在西北区东部与东移南压的西北冷空气形成强辐合,是造成西北区东部这次强降水的主要影响系统。在700 hPa等压面上湿位涡与辐合区域相对应的是,在西北区东部存在一个湿位涡正压项MPV1的正值区和湿位涡斜压项MPV2的负值区域,它们准确地指示了辐合区的范围及变化,暴雨出现在辐合区中或MPV1和MPV2的等值线密集区边缘上;对流层高低层正值MPV1可以指示对流稳定的冷空气的变化,而对流稳定度小的暖湿气流表现为小的正值(高层)或负值(低层),等值线密集带指示了降水的后界。用模式输出的高时空分辨率资料诊断暴雨发生期间各个暴雨中心的等熵面结构,表明用湿位涡理论可以很好地解释这次暴雨发生的局地特征。     

1961-2010年西北干旱区极端降水指数的时空变化分析

结合绝对阈值和百分位法定义极端降水事件的优点,提出了一种更灵敏的检测极端降水事件的方法. 该方法不仅能检测出常用降水指数无法检测到的降水量稀少地区尤其干旱区的极端降水事件,同时也能过滤掉其检测到的降水量丰富地区的虚假极端降水事件. 此方法首次被应用于统计1961年1月至2010年2月西北干旱区72个气象站点的年和季节的极端降水指数（大降水和强降水指数）,并分析了极端降水指数的时间变化趋势及其空间分布特征. 结果表明：西北干旱区春（3-5月）、秋（9-11月）、冬（12月至次年2月）三季极端降水指数无显著（P>0.05）变化趋势,夏季（6-8月）大降水的频率和降水量以及大降水降水量占总降水量的比重都显著增加;新疆地区极端降水指数为增加趋势的区域基本都分布在海拔较高（约海拔1 000 m以上）的地区;西北干旱区东部极端降水指数变化趋势的空间分布有明显的季节差异,表现为夏、秋季大部分地区为增加趋势,冬、春季大部分地区为减小趋势.     

Felsic magmatic phases and the role of late-stage aplitic dykes in the formation of the world-class Cantung Tungsten skarn deposit, Northwest Territories, Canada

A field and petro-chemical classification of felsic magmatic phases (FMPs) at the world-class Cantung W skarn deposit was undertaken to document the evolution of magmatism and the relationships between different FMPs, metasomatism, and mineralization. Early FMPs include moderately differentiated (Zr/Hf = 18–26, Ti/Zr = 14–15) biotite monzogranitic plutons and early biotite-rich granitic dykes, and compositionally similar quartz–feldspar porphyry dykes. Late, highly fractionated (Zr/Hf = 8–17, Ti/Zr = 3–13) FMPs sourced from a deeper monzogranitic intrusion include: (1) leucocratic biotite- or tourmaline-bearing dykes derived from localized entrapments of residual magma; and, (2) sub-vertical NE-trending aplitic dykes derived from a larger segregation of residual fluid- and incompatible element-enriched magma. The aplitic dykes have textures, morphologies, spatial associations, and a pervasive calcic metasomatic mineral assemblage (Ca-plagioclase + quartz or clinozoisite) indicative of syn-mineralization emplacement. Very late-stage overpressuring and initiation of sub-vertical fractures into the overlying plutonic carapace and country rocks by supercritical magmatic fluid led to an interaction with calcareous country rocks that resulted in an increased aCa²⁺ in the fluid and the concurrent precipitation of W skarn. Residual magma also ascended with, and quenched in equilibrium with the magmatic fluid to from the aplitic dykes, then was metasomatized by the fluid as it interacted with calcareous country rocks. Overall, highly fractionated and moderately to very highly undercooled FMPs at Cantung provide evidence for a large and evolving felsic magmatic system at depth that segregated and maintained a stable fluid- and incompatible element-enriched residual magma until the latest stages of crystallization. The detailed study of FMPs associated with magmatic-hydrothermal mineral deposits allow us to refine our understanding of these mineralizing systems and better define metallogenic and exploration models for intrusion-related mineralization.     

我国西北地区气候变化与北极涛动的交叉小波分析

运用交叉小波方法分析了近56 a来我国西北地区气候变化与北极涛动指数（AOI）、欧亚纬向环流指数之间的联系,讨论了西北地区冬季气温和夏季降水变化与同期AOI之间的多时间尺度相关。结果表明,AOI、西北地区降水和气温变化都存在着不同尺度的周期振荡,西北地区降水与AOI之间存在准3 a尺度的显著共振周期,而AOI与西北地区气温变化的多时间尺度相关表现为准2a、3-5 a和8-11 a左右的显著相关振荡且以8-11 a共振周期的凝聚性最强;AO对西北地区气温变化的影响比对降水的影响更显著,与其年代际尺度的相互作用有关。当冬季北极涛动处于正相位时,欧亚纬向环流偏强,西北地区冬季气温偏高。夏季西北地区降水变化与前期北极涛动指数异常密切相关,这对于西北地区夏季降水变化预测具有重要的参考意义。     

西北地区近期地壳水平运动与构造变形特征

利用截止2004年的西北地区GPS和跨祁连-龙首山构造带的红外测距观测资料，借助最小二乘配置、弹性块体边界负位错模型及单一力源反演，研究昆仑山口西8．1级大震前后西北地区水平形变应变场的动态演化特征；尤其是大震3年后，即当前的构造形变与应力场态势；获取活动块体及其边界断裂上可能反映中强以上孕震背景的高应变能积累区、段，以及可能的潜在震源。结果表明：青藏块体北缘地区经8．1级大震后的短期松弛和调整，目前正在恢复印度板块北东向碰撞推挤背景场的主控作用。而北天山构造带中段及其与西段的交汇区、南天山构造带中西段及其与西昆仑构造带的交汇区、阿尔金断裂中段、祁连山构造带中东段及其与海原断裂的交汇区、西秦岭北缘断裂与庄浪河断裂东南延伸线的交汇区域等具有相对高应变能积累背景；临泽与海原这两个地区也反映一定程度的应变能积累状态。     

赣西北狮子岭花岗岩型锂矿床成因：来自岩石地球化学和锆石U-Pb年代学的约束

赣西北矿集区是中国重要的花岗岩型锂矿资源基地,以发育多期次多阶段岩浆作用和大规模锂等稀有金属矿床著称。区内花岗质岩浆与稀有金属成矿关系密切,为进一步研究该地区花岗质岩浆演化特征及其与稀有金属成矿的联系,确定相关花岗岩成岩时代及成因类型,查明稀有金属成矿机制,笔者选择九岭地区狮子岭花岗岩作为研究对象,对其开展了岩相学、锆石U-Pb年代学及岩石地球化学分析。结果显示,狮子岭花岗岩属高钾钙碱性系列,具有高Si,富P,贫Ca、Mg、Fe,富集U、Hf等高场强元素,亏损Ba、Sr等大离子亲石元素,稀土元素总量较低（ΣREE=2.12×10^-6~146.24×10^-6）,轻稀土元素相对富集（LREE/HREE=3.5~16.53）,弱Eu负异常（δEu=0.23~0.59）的特征。整体上具有S型花岗岩的地球化学特征。锆石U-Pb定年显示,黑云母二长花岗岩成岩年龄为（141.02±0.59）Ma,锂（白）云母碱长花岗岩成岩年龄为（113.96±0.72）Ma。锂（白）云母碱长花岗岩成岩过程中形成磷锂铝石及锂云母等含锂矿物,其成岩年龄可视为锂等稀有金属成矿年龄。该区稀有金属矿化受燕山晚期岩浆结晶分异作用及后期热液交代作用共同影响,岩浆结晶分异作用是Li、Nb、Ta成矿的决定性因素,后期热液交代作用为Li等成矿元素的二次富集提供条件。     

A new Brachiosauridae Sauropod dinosaur from the lower Cretaceous of Europe (Soria Province,Spain)

A new dinosaur sauropod from the Golmayo Formation (upper Hauterivian-lower Barremian) in Soria province (Spain) is described as Soriatitan golmayensis gen. et sp. nov. The new material consists of one tooth, three dorsal vertebrae with ribs, a partial sacrum, five caudal centra, two caudal vertebral spines, one chevron, a humerus, an ulna, a radius, two partial ilia, two ischia, a fragment of pubis, and a partial femur. Cladistic analysis identified the material as belonging to Brachiosaruidae within Titanosauriformes. Sauropod material from the Golmayo Formation shares a diagnostic feature with Abydosaurus, Cedarosaurus, Tastavinsaurus and Venenosaurus including anteriorly deflected anterior–middle caudal neural spines and with Cedarosaurus a proximodistally straight lateral margin between the proximal head and the shaft of the humerus. Eight characters are potential autapomorphies in the sauropod from Spain, including the presence of a large rectangular ventral ridge below the preacetabular process of the ilium, the same length of the pubic and ischiadic blades in the ischium, and two lateral ridges in the lateral area of the deltopectoral crest of the humerus. The presence of Early Cretaceous brachiosarids in both, North America and Europe, give support to the hypothesis of a connection between the tectonic plates of these continents at some point during the Early Cretaceous.     

西北干旱区水资源约束下城市化过程及生态效应研究的理论探讨

城市化是西北干旱区实现小康目标的必由之路,然而最大的自然障碍因素是水资源严重短缺。现实的城市化与水资源及生态环境保护之间存在着各种矛盾与胁迫。从城市化过程及其生态效应研究的重要性出发,透过对国内外研究进展的分析与评述,把水资源作为西北干旱区先决约束条件。提出了水资源约束下西北干旱区城市化过程及其生态效应的研究思路,包括选择水资源变化过程与城市化过程之间相互胁迫的驱动因子,揭示水资源变化对城市化过程的胁迫机制与规律;分析城市化过程引起的与水相关的生态效应;建立城市化过程及其生态效应预警指标体系。对不同强度水资源约束下城市化过程进行动态预警和情景分析;选择最节水的城市化发展模式和建设节水型城镇体系等。进而为加快西北干旱区城市化发展进程、改善干旱区生态环境、实现小康目标提供科学的决策依据。     

A Debt to the West: Recent Developments in the International Financial Situation of East-Central Europe

East-Central Europe is undergoing a rapid political and economic transformation. The unprecedented depth and speed of the economic reforms have produced serious questions about the stability of the region, and its future relations with western Europe and the world economy. This paper surveys and evaluates the size and character of existing debt stocks owed to the West by Hungary, Poland, and Czechoslovakia. The future political and economic stability of East-Central Europe and the European Community depends, to a large extent, on the ability of the Western financial system to respond to the long-term needs of the region.