青藏块体强震与祁连山地震带中强震相关性的初步探讨

对青藏块体强震与祁连山地震带中强震的相关性进行了初步分析。结果表明：青藏块体发生强地震后,祁连山地震带中强地震活动具有增强趋势。通过分析认为,祁连山地震带已进入新的地震活跃期,并有可能发生7级以上地震。     

Compositions of Upper Mantle Fluids Beneath Eastern China: Implications for Mantle Evolution

The composition of gases trapped in olivine, orthopyroxene and clinopyroxene in Iherzolite xenoliths collected from different locations in eastern China has been measured by the vacuum stepped-heating mass spectrometry. These xenoliths are hosted in alkali basalts and considered as residues of partial melting of the upper mantle, and may contain evidence of mantle evolution. The results show that various kinds of fluid inclusions in Iherzolite xenoliths have been released at distinct times, which could be related to different stages of mantle evolution. In general, primitive fluids of the upper mantle (PFUM) beneath eastern China are dominated by H2, CO2 and CO, and are characterized by high contents of H2 and reduced gases. The compositions of PFUM are highly variable and related to tectonic settings. CO, CO2 and H2 are the main components of the PFUM beneath cratons; the PFUM in the mantle enriched in potassic metasomatism in the northern part of northeastern China has a high content of H2, while CO2 a     

乌鲁木齐河源区不同海拔的火绒草叶片结构特征的比较研究

采用PEG和Epon-812二次包埋方法, 利用光学显微镜和扫描电子显微镜对乌鲁木齐河源区海拔4 000 m、 3 400 m、 2 500 m三种不同高度的火绒草(Leontopodium leontopodiodes(Willd.) Beauv.)叶片剖面及表面结构进行了观察. 结果表明: 火绒草叶片既具有中生植物又兼有旱生和湿生植物的部分结构特征; 其叶片厚度、表皮细胞外壁角质层表面、外角质层蜡质分泌物的有无、表皮细胞形状、气孔器分布特征、保卫细胞极区"T"型角质加厚程度、气孔开口(长/宽)、气孔密度、维管束形态、 CTR值、叶肉细胞叶绿体含量等性状特征,在不同海拔的火绒草间呈现出明显差异; 而表皮的气孔水平位置类型、毛状附属器等性状则差异较小. 数值分析火绒草叶结构各类性状以及不同性状状态的组合, 显示出个体形态的多样性及其对高山环境和海拔高度的适宜性特征.     

北疆牧区积雪图像分类与雪深反演模型的研究

利用NOAA/AVHRR晴空气象条件下的资料, 建立积雪监测反演模型, 动态监测雪灾期间大范围的积雪空间分布状况, 对牧区雪灾综合评价及防灾救灾具有重要的意义. 使用北疆地区1996-97年2次雪灾期间的4个时相的晴空NOAA卫星数据及20个地面气象台站观测资料, 研究了云与雪的判识及图像去云处理方法, 提出了云层覆盖下图像缺值插补处理的一种新算法; 采用线性混合光谱分解方法, 研究了基于像元的积雪覆盖率及积雪空间分类算法, 模拟出北疆地区积雪深度遥感地学反演模型. 研究结果可为牧区雪情动态监测、分析与综合评价系统的建设提供科学依据.     

中国冰雹研究的新进展和主要科学问题

简要总结了自1990年以来中国人工防雹在科学技术方面的进展,分析了冰雹研究和防雹作业方面存在的一些科学技术问题,提出了解决问题的建议。     

新型天气预报业务系统框架

在兰州区域气象中心ＤＥＣ业务网络下运行的新型天气预报业务系统,对西北地区东部的重要天气,按中短期预报时效,以模块的方式建立预报系统;以引进人工智能神经元网络技术,预报甘肃省降水天气。该系统经试运行,具有业务实用性强、预报效果较好等特点     

一个降水预报的时间序列线性平稳预测模型

本文利用兰州１９４４～１９９７年的月平均降水资料,建立了线性平稳序列的降水预测模型,该模型使用了功谱密度函数中的最大熵法（或叫全极模型）,并将特征多项式模大于１的根反射到单位圆内,再返回修正后的线性预测的系数。并对１９８６～１９９７年１１年的月降水做了预测试验,试验结果表明,该模型具有一定的预报能力,其中取１５阶预报效果较好。此方法在短期气候预测业务中,可作为台站月、季、年降水预测走向客观化、定量化方法的一种初步尝试     

祁连造山带玉石沟地幔橄榄岩中挥发分的流体化学和稳定同位素组成及古大洋岩石圈演化意义

Fluid inclusions in olivine and orthopyroxene of mantle peridotites from the Yushigou ophiolite can be divided into three types based on decrepitation temperature,shape and distribution.Type-1 fluid inclusions are characterized by oval or negative crystal shapes and small size(<5μm across).They occur in the cores and mantles of the host crystals,and decrepitated at>840℃.Type- 2 fluid inclusions have irregular or tabular shapes with relatively large size(10～100μm in length).They occur in irregular or circular healed micro-fractures in the host crystals,and decrepitated at 612～710℃.Type-3 fluid inclusions have size and shape,similar to type-2 fluid inclusions but occur in micro-fractures restricted to the margins of the host crystals,and decrepitated at much lower temperature from 190℃to 340℃.The three different types of fluid inclusions are interpreted to represent primary,metasomatic (pseudo-secondary)and secondary inclusions,respectively.Stepwise heating reveals three concentration peaks of volatiles at 200～400℃,400～800℃and 800～1200℃released from olivine and orthopyroxene in harzburgite and dunite from the Yushigou ophiolite, which are considered to correspond to the decrepitation of secondary,metasomatic and primary fluid inclusions at similar temperature ranges.CO2 is a major constituent in the volatiles released at three different temperature intervals.Trace amounts of H_2 and N_2 are present in the volatiles released at<800℃and trace amounts of H_2O and SO_2 are mainly present in the volatiles at 400～800℃.TheδD(-95.2‰,-306.3‰)of H_2O and theδ~(13)C(-15.5～-12.5‰)andδ~(18)O values(1.4～1.9‰)of CO_2 released at<800℃are lower than normal mantle values and suggest the mixing origin of crustal fluids( sedimentary organic)with ocean water,implying that Yushigou AOLM had undergone an intensive metasomatism by a fluid composed of CO_2.H_2O and SO_2,and followed by degassing. In contrast,the volatiles released at 800～1200℃are characterized by trace amounts of H_2 and CO in dunite and SO_2 in harzburgite, much lighterδ~(13)C(-29.1‰～-19.5‰),heavierδ~(13)O(8.8‰)of CO_2 and positive relationship between these isotopic ratios and the concentration of CO_2.Such features can be best explained by mixing of significant terrestrial crustal(organic)and minor mantle volatiles.We proposed that the Yishigou peridotites are more likely to have derived from a continental lithosphere instead of an oceanic lithosphere comprising the Yishigou gabbros and pillowed basalts.A supra-subduction tectonic setting is thus inferred for the Yushigou ophiolite.     

龙首山岩群成岩时代探讨

文中利用颗粒锆石 U- Pb法获得了龙首山岩群奥长花岗岩 2 0 15± 16 Ma的上交点年龄和 4 5 2±16 Ma下交点年龄 ,上交点代表成岩的时代 ,下交点揭示的为广泛发育的加里东期同碰撞热构造事件 ;结合 Sm-Nd、Rb- Sr法的年龄数据和区域地质对比 ,认为龙首山岩群成岩时代属古元古代 ,它反映的是华北陆台除 2 5 0 0 Ma和 180 0 Ma之外 ,又一重要构造 -热事件