对GIS技术下地籍管理系统建立中几个问题的探讨

建立基于GIS地籍管理系统是目前土地管理部门正在开展的一项建设性工作。本文在分析GIS技术应用于地籍管理特点的基础上 ,对建立地籍管理系统时GIS地籍数据库的建设、GIS平台的选择以及系统功能开发中的一些问题进行了探讨     

The 1996 and 1998 subglacial eruptions beneath the Vatnajökull ice sheet in Iceland: contrasting geochemical and geophysical inferences on magma migration

87 Sr/⁸⁶Sr (0.70322) and δ ¹⁸O ( ∼2.9‰), whereas significantly lower and higher values, respectively, are found in samples from the Bárdarbunga volcanic system (0.70307 and 3.8‰). These results strongly indicate that the Gjálp magma originated from the Grímsv?tn magma system. The 1996 magma is of an intermediate composition, representing a basaltic icelandite formed by 50% fractional crystallization of a tholeiite magma similar in composition to that expelled by the 1998 Grímsv?tn eruption. The differentiation that produced the Gjálp magma may have taken place in a subsidiary magma chamber that last erupted in 1938 and would be located directly beneath the 1996 eruption site. This chamber was ruptured when a tectonic fracture propagated southward from Bárdarbunga central volcano, as indicated by the seismicity that preceded the eruption. Our geochemical results are therefore not in agreement with lateral magma migration feeding the 1996 Gjálp eruption. Moreover, the results clearly demonstrate that isotope ratios are excellent tracers for deciphering pathways of magma migration and permit a clear delineation of the volcanic systems beneath Vatnaj?kull ice sheet. Received: 1 April 1998 / Accepted: 17 August 1999     

Occurrence of angiosperm remains in an Early Cretaceous intertrappean bed, Rajmahal Basin, India

An angiosperm fruit of uncertain affinity and a questionable flower are reported from the Rajmahal Formation (Early Cretaceous) at the locality of Sonajori, Rajmahal Basin. The remains of ferns, Pentoxylales and conifers have been described previously from this locality. The significant addition of angiosperm megafossil remains confirms that flowering plants were evolving during the Early Cretaceous Epoch in India. The Sonajori assemblage seems to be the youngest fossil assemblage recovered so far from the Rajmahal Basin. It is tentatively dated as Barremian–Aptian.     

Electric-field gradient and mean-squared-displacement tensors in hedenbergite from single-crystal Mössbauer milliprobe measurements

We report Mössbauer milliprobe measurements on small single-crystals of a magnesium-rich hedenbergite, approximate composition CaFe_0.54Mg_0.46 (SiO₃)₂, in which each of the electric-field gradient and mean-squared displacement tensors for Fe²⁺ in the M1 site of the crystal are precisely determined. Each tensor has in common, as required of crystal symmetry, the twofold axis of the monoclinic unit cell, but the principal directions of the two tensors in the perpendicular plane are non-coincident. The mean-squared displacements determined in the Mössbauer experiment exceed those determined from the X-ray vibration ellipsoids for Fe²⁺/M1 by a factor of 1.6; the anisotropy in the mean-squared displacement tensor from the Mössbauer measurements exceeds that from X-ray by a factor of around 5. The ramifications of these differences are discussed.     

油气藏动力学成因模式与分类

根据油气运聚的动力和作用方式将油气藏成因分为 3类 8种 17式。这 8种分别是 :①高压势场作用下形成的油气藏 ;②低压势场作用下形成的油气藏 ;③油水携带溶解气游离释放形成的天然气藏 ;④浮力作用下形成的油气藏 ;⑤毛细管力作用下形成的油气藏 ;⑥天然气体积膨胀形成的深盆气藏 ;⑦分子吸附作用形成的煤层瓦斯气藏 ;⑧分子水合作用形成的水合甲烷气藏。①～③种为突发式流压作用形成的油气藏 ,④～⑥种为缓慢式烃势差形成的油气藏 ,⑦和⑧为非常规条件下天然气汇聚形成的特殊类型的 (油 )气藏。相同动力学成因的油气藏因实际地质条件的差异可以进一步分成亚类。不同动力学成因的油气藏的分布规律、主控因素和产状特征不同。研究油气运聚的动力机制和成因模式对指导油气田勘探、提高勘探效益具有重要意义。     

吉林夹皮沟金矿带构造地球化学特征分析

对夹皮沟金矿的区域、矿带、矿体和成矿元素等构造地球化学特征进行了系统分析,结果表明,中生代太平洋板块向华北板块碰撞、俯冲,其效应激发了幔源和壳源岩浆的发生,成矿微量元素活化、迁移并形成区域性Au、Cu侧向分带。矿带内Cu-Au-Bi对称性分布、控矿构造组合类型与矿体原生晕序列的相关性以及稳定同位素所揭示的构造分馏等特征,都体现夹皮沟金矿带是幔-壳流体加入、矿质多源、中生代构造-岩浆-成矿作用的产物。     

扬子板块西缘黄草山和下索子花岗岩体锆石U-Pb年代学研究

对扬子板块西缘泸定—石棉地区黄草山花岗岩体和康定地区下索子花岗岩体中自形锆石,采用205Pb-235U混合同位素稀释法测定了锆石U-Pb年龄。测试结果表明,黄草山岩体中锆石结晶年龄为786±36Ma,下索子岩体中锆石结晶年龄为805±15Ma,表明它们都是晋宁期岩浆活动产物。     

大别山北部榴辉岩和英云闪长质片麻岩锆石U-Pb年龄及多期变质增生

大别山北部榴辉岩及英云闪长质片麻岩的锆石U-Pb年龄分析表明：北部榴辉岩相峰期变质时代为226～230Ma左右;北部塔儿河一带英云闪长质片麻岩经历过印支期变质事件;大别山北部与南部超高压岩石中一致的（226～230Ma）高压或超高压变质年龄表明,北部镁铁-超镁铁质岩带中部分岩石也曾作为扬子俯冲陆壳的一部分,在印支期发生过高压或超高压变质作用;本区锆石发生过两期变质增生事件,一是印支期高压或超高压变质,另一期是燕山期热变质事件;榴辉岩及英云闪长质片麻岩的原岩形成时代为晚元古代;锆石U-Pb年龄可用多期变质增生模型来解释。     

中、新生代陆相沉积盆地砂岩型铀矿床流体作用研究

通过对中、新生代陆相沉积盆地典型砂岩型铀矿床实例分析,本文阐述了砂岩型铀矿床的分类特征及其与盆地流体演化的关系,以及盆地流体演化史分析在砂岩型铀矿床找矿中的重要性,同时对铀在流体中活化、迁移、沉淀机制及砂岩型铀矿床流体作用研究方法进行了探讨。     

时间序列模型和有限元模型在地下水资源评价和开发中的应用——以徐州市裂隙岩溶水为例

针对徐州市地下水长期无节制开采和管理不善而引起的多种环境地质问题,建立了与研究区裂隙岩溶含水层相适应的地下水流模型,并运用有限元方法进行求解。考虑到大气降水的多寡及其分配状况是影响地下水资源的最终决定因素,同时建立了研究区大气降水的时间序列模型,并应用于评价该区地下水资源,从而在宏观上为徐州市合理开采裂隙岩溶水资源提供科学依据。其结果对我国其它类似地区地下水资源的合理开采具有指导意义。