南极绕极流的经向输运

南极绕极流(ACC)是南大洋中最显著的流动，流量超过130×106m3/s (Nowlin et al.，1986)。传统认为，由于以东向运动为主的ACC的存在极大地阻碍了南大洋中上层的南北向物质和能量的交换，绕极流区的经向输运是非常小的。但是近些年的研究发现，穿过ACC的通量并不是可以忽略不计的，它对维持南极和亚南极区的动力和热力平衡起着重要作用，在全球气候系统中也有着深刻的影响(Doos et al.，1994)。     

一种高效建模数值算法及其应用——LatticeBoltzmann方法

近年来,格子Boltzmann方法(LBM)已发展为一种模拟流体和物理问题的新颖的、有前景的数值方法,在许多领域的各种数值问题求解上取得很大的成功.文章介绍了一种模拟复杂流动的高效建模数值算法Lattice Boltzmann方法和它的基本原理及其应用.并通过两个实例数值模拟计算,说明Lattice Boltzmann方法正确、有效.并展示了广阔的应用前景,为今后更深入的研究和广泛应用打下基础.     

A STUDY ON THE RELATIONSHIP BETWEEN SPRING SOIL MOISTURE OVER CHINA AND EAST ASIA SUMMER MONSOON

The correlation analysis has been used to study the relationship between spring soil moisture over China and East Asian summer monsoon (EASM). It is shown that EASM has a strong positive correlation with spring soil moisture over southwest China and the Great Bend region of the Yellow River. A standard soil moisture index (SMI) has been defined using the observed soil moisture of the two regions. The results show that SMI has a strong correlation with EASM. The years of strong (weak) SMI are associated with stronger (weaker) summer monsoon circulation. In the years of strong SMI, the west Pacific subtropical high is much northward in position and weaker in intensity; the westerlies zone is also more to the north. All of these make EASM circulation move northward and cause the rainfall belt to relocate to North China and Northeast China. SMI can reflect the variation of the summer rainfall anomaly over eastern China. In the years of strong SMI, the rainfall belt is mainly located over the northem part of China.However, during the weak years, the summer rainfall belt is largely located over the mid- and lower- reaches of the Yangtze River. Additionally, the SMI has obvious oscillations of quasi 4-6 years and quasi 2 years. Moreover, negative SMI predicts EASM better than positive SMI.     

Geochemistry of South African On- and Off-craton, Group I and Group II Kimberlites: Petrogenesis and Source Region Evolution

Bulk-rock geochemical compositions of hypabyssal kimberlites,emplaced through the Archaean Kaapvaal craton and ProterozoicNamaqua–Natal belt, are used to estimate close-to-primarymagma compositions of Group I kimberlites (Mg-number = 0·82–0·87;22–28 wt % MgO; 21–30 wt % SiO₂; 10–17 wt% CaO; 0·2–1·7 wt % K₂O) and Group II kimberlites(Mg-number = 0·86–0·89; 23–29 wt %MgO; 28–36 wt % SiO₂; 8–13 wt % CaO; 1·6–4·6wt % K₂O). Group I kimberlites are distinguished from GroupII by their lower Ba/Nb (<12), Th/Nb (<1·1) andLa/Nb (<1·1) but higher Ce/Pb (>22) ratios. Thedistinct rare earth element patterns of the two types of kimberlitesindicate a more highly metasomatized source for Group II kimberlites,with more residual clinopyroxene and less residual garnet. Thesimilarity of Sr and Nd isotope ratios and diagnostic traceelement ratios (Ce/Pb, Nb/U, La/Nb, Ba/Nb, Th/Nb) of Group Ikimberlites to ocean island basalts (OIB), but more refractoryMg-numbers and Ni contents, are consistent with derivation ofGroup I kimberlites from subcontinental lithospheric mantle(SCLM) that has been enriched by OIB-like melts or fluids. Sourceenrichment ages and plate reconstructions support a direct associationof these melts or fluids with Mesozoic upwelling beneath southernAfrica of a mantle plume(s), at present located beneath thesouthern South Atlantic Ocean. In contrast, the geochemicalcharacteristics of both on- and off-craton Group II kimberlitesshow strong similarity to calc-alkaline magmas, particularlyin their Nb and Ta depletion and Pb enrichment. It is suggestedthat Group II kimberlites are derived from both Archaean andProterozoic lithospheric mantle source regions metasomatizedby melts or fluids associated with ancient subduction events,unrelated to mantle plume upwelling. The upwelling of mantleplumes beneath southern Africa during the Mesozoic, at the timeof Gondwana break-up, may have acted as a heat source for partialmelting of the SCLM and the generation of both Group I and GroupII kimberlite magmas. KEY WORDS: kimberlite; geochemistry; petrogenesis; mantle plumes; South Africa     

城市地质信息数据安全管理研究

随着国家对城市地质工作的不断重视以及力度的加强,城市地质信息系统在经历着不断的发展和更新换代,同时有关地质体状况的基础地质数据、地质环境数据（如地面沉降监测）等也在随着技术的不断发展而逐渐增长。所有的数据集群在一起,通过各种应用平台为城市规划、建设、管理服务。但是,日益庞大的数据将面临数据存储、备份、保护等问题。经过对网络运营状况,现有网络设备、软件系统、数据库规模以及未来网络发展的分析研究,本文结合自身网络特性、通过相应技术手段,为配合未来发展需求,建立了一套城市地质信息数据安全管理体系。     

On the Petrogeny of the Leucite-bearing Rocks of the Roman and Birunga Volcanic Regions

The petrogeny of the leucite-bearing rocks occurring in theRoman and Birunga volcanic regions is reappraised using previouslypublished data. It is shown by means of Principal Latent VectorVariation Diagrams (Le Maitre, 1968) that the chemical analysesof rocks from the two provinces form complementary suites withina well defined trend, which can be interpreted in terms of low-pressurecrystal differentiation. The potential role of the basic compositionsof the trend as parent material is examined in the light ofrecent experimental evidence and a possible evolutionary modelis proposed involving polybaric crystallization.     

右江褶皱带东南缘西大明山矿集区铅同位素地球化学特征及其地质意义

广西西大明山多金属矿集区是右江褶皱带东南缘近年找矿突破的重要地区,发育凤凰山特大型银矿床、罗维中型钨锌多金属矿床、弄屯大型铅锌矿床及一些中、小型矿床等。其中罗维和弄屯矿床是近年新发现的矿床,矿体分别呈层状赋存于寒武系碎屑岩和呈脉状赋存于寒武系与泥盆系接触界面附近或断裂破碎带中。笔者对矿集区内层状和脉状矿床矿石硫化物铅同位素进行研究,并与赋矿围岩、隐伏二长花岗岩进行对比。铅同位素数据显示:罗维层状矿床矿石硫化物铅同位素组成为:~(206)Pb/~(204)Pb=18.1320~18.5980,~(207)Pb/~(204)Pb=15.5920~15.7988,~(208)Pb/~(204)Pb=38.4041~39.0461;弄屯脉状矿床矿石硫化物铅同位素组成为:~(206)Pb/~(204)Pb=18.3240~18.5060,~(207)Pb/~(204)Pb=15.7321~15.9140,~(208)Pb/~(204)Pb=38.6511~39.2311;二者具有相似的同位素组成,但弄屯矿床矿石硫化物~(207)Pb/~(204)Pb比值略高于罗维矿床矿石硫化物。罗维矿床矿石硫化物铅同位素组成与深部隐伏二长花岗岩铅同位素组成一致;而弄屯矿床矿石硫化物~(208)Pb/~(204)Pb值介于二长花岗岩和地层铅同位同位素组成之间,且矿石~(207)Pb/~(204)Pb比值指示矿石铅可能来源于上泥盆统莲花山组碎屑岩与中寒武统黄洞口组碎屑岩。渌井和大新铅锌矿床显示出异常高的~(207)Pb/~(204)Pb,暗示可能还有其他富铀的地质体为成矿提供放射成因铅,铅同位素特征值(μ值、ω值)揭示矿石硫化物和岩体都具有壳源铅的特征;从垂向上,各矿床距罗维隐伏岩体顶界距离增加,岩浆铅减少,地层铅增加。综合研究认为,西大明山多金属矿集区应属于典型的与深部燕山期岩体侵入有关的岩浆热液充填交代型矿床,成矿物质主要来源于燕山期岩浆和围岩地层。     

改进遗传算法在变形监测网平差中的应用

遗传算法在处理非线性最小二乘问题上具有其独到的优势。文中通过对遗传算法的理论性研究,对常规遗传算法的选择交叉策略、变异步长及变异率都作了改进。并将改进的遗传算法应用到变形监测网平差中,实现变形监测网在不同基准下的非线性平差计算,并通过实例证明其实用性及优越性。