华南热带气旋特大暴雨的统计特征   总被引：8，自引：3，他引：8  

毛夏  贺忠  毛绍荣 《热带气象学报》1996,12(1):78-84

根据珠江三角洲１９７６－１９８３年３－５月逐日天气资料和广州０８时探空资料，采用对比度分析方法，研究了本地区春季龙卷发生的环境条件，并与非龙卷局地强风暴发生的环境条件作了比较，结果表明，龙卷发生的有利环境条件对流层深层气层中气压低风速大、层结不稳定、低层高温高湿和中下层位势不稳定，定性上与局地强风暴的条件基本相同，其中对流层深厚气层中更强的强的低压辐合、更不稳定的层结和更大的水平动量是局地强风暴进  相似文献   

北祁连西段早古生代构造演化史   总被引：21，自引：2，他引：21  

左国朝  毛景文 《甘肃地质》1999,8(1):6-13

北祁连西段与北祁连中段构造带之间被一条平行于阿尔金断裂带的宗宾大坂古转换断裂所隔，东西两段在早古生代构造演化史上有明显差异。北祁连西段早古生代构造是在前震旦系陆壳基底上，在震旦纪再一次开裂演变为裂陷槽，寒武—奥陶纪为裂谷—海沟—火山弧多元构造的格局  相似文献   

A multiple representation data structure for dynamic visualisation of generalised 3D city models   总被引：2，自引：0，他引：2  

Bo Mao  Yifang Ban 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(2):198-208

In this paper, a novel multiple representation data structure for dynamic visualisation of 3D city models, called CityTree, is proposed. To create a CityTree, the ground plans of the buildings are generated and simplified. Then, the buildings are divided into clusters by the road network and one CityTree is created for each cluster. The leaf nodes of the CityTree represent the original 3D objects of each building, and the intermediate nodes represent groups of close buildings. By utilising CityTree, it is possible to have dynamic zoom functionality in real time. The CityTree methodology is implemented in a framework where the original city model is stored in CityGML and the CityTree is stored as X3D scenes. A case study confirms the applicability of the CityTree for dynamic visualisation of 3D city models.  相似文献   

凤凰山矿田成矿地质体三维结构与控矿地质因素分析   总被引：2，自引：0，他引：2  

毛先成  唐艳华  赖健清  邹艳红  陈进  彭省临  邵拥军 《地质学报》2011,85(9):1507-1518

安徽铜陵凤凰山铜矿正面临资源保有程度严重不足的问题,建立凤凰山矿田成矿地质体三维结构和控矿地质因素模型,开展矿田深部隐伏矿体立体定位预测具有重要的现实意义.凤凰山矿田矿床矿体的定位主要受接触带和断裂构造的复合控制,新屋里岩体与围岩呈侵入接触,局部地段超覆于围岩之上,接触带的形态和产状控制了矿体的空间分布.在分析矿田地质...  相似文献   

Influence of phosphate on the oxidation kinetics of nanomolar Fe(II) in aqueous solution at circumneutral pH     

Yanpeng Mao  A. Ninh Pham  T. David Waite 《Geochimica et cosmochimica acta》2011,75(16):4601-4610

The oxygenation kinetics of nanomolar concentrations of Fe(II) in aqueous solution have been studied in the absence and presence of millimolar concentrations of phosphate over the pH range 6.0-7.8. At each phosphate concentration investigated, the overall oxidation rate constant varied linearly with pH, and increased with increasing phosphate concentration. A model based on equilibrium speciation of Fe(II) was found to satisfactorily explain the results obtained. From this model, the rate constants for oxygenation of the Fe(II)-phosphate species FeH₂PO₄⁺, FeHPO₄ and FePO₄⁻ have been determined for the first time. FePO₄⁻ was found to be the most kinetically reactive species at circumneutral pH with an estimated oxygenation rate constant of (2.2 ± 0.2) × 10 M⁻¹ s⁻¹. FeH₂PO₄⁺ and FeHPO₄ were found to be less reactive with oxygen, with rate constants of (3.2 ± 2) × 10⁻² M⁻¹ s⁻¹ and (1.2 ± 0.8) × 10⁻¹ M⁻¹ s⁻¹, respectively.  相似文献   

乌鲁木齐河流域普通民众对冰冻圈变化的感知及适应性对策选择   总被引：3，自引：0，他引：3       下载免费PDF全文

邓茂芝  张洪广  毛炜峄  王英巍 《气候变化研究进展》2011,7(1):65-72

基于乌鲁木齐河流域普通民众对气候变化及冰冻圈变化感知情况的问卷调查,结合有关监测研究结果,分析了普通民众对流域气候变化及冰冻圈变化的感知情况,探讨了环境变化对流域水资源和农业生产的可能影响.普通民众对气候变化和冰冻圈变化的感知基本与科学监测事实相符.对气候变化和冰冻圈变化条件下普通民众对水资源紧缺的适应措施的分析发现:...  相似文献   

攀枝花市区5-7月人体舒适度变化趋势研究     

毛家勋  吕忠东  陈永琼 《气象与环境科学》2011,34(Z1):65-69

选用攀枝花市区1977-2009年5-7月逐日平均气温、平均相对湿度和平均风速资料,计算擎枝花市区的人体舒适度指数,并利用线性趋势系数、多项式以及MK突变检验等方法分析攀枝花市区的舒适程度和舒适度指数变化规律.结果表明:攀枝花市区舒适度指数绝大多数处于5～6级,占到总统计天数的96.9％;攀枝花市区舒适度指数5级、6级...  相似文献   

Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?   总被引：1，自引：0，他引：1  

Guang-Hai Shi  Xiang-Kun Zhu  Qian Mao  Guo-Wu Li 《Geochimica et cosmochimica acta》2011,75(6):1608-1620

Here we report spherules in Myanmar jadeitite, a rock forming from jadeitic fluids within mantle-derived serpentinized rocks in subduction zones under high-pressure conditions (>1.0 GPa) and rather low temperatures of about 250-370 °C. The spherules have off-centre iron nuclei and dendritic wüstite cortexes, with tiny wüstite crystals perpendicular to the surface of iron core. Within the spherules are vesicles occupied by calcite, jadeite, albite? or mixtures of these phases, and the cortexes contain about 10 wt.% SiO₂ + Al₂O₃ + Na₂O filling materials within wüstite. The spherules are in direct contact with jadeite crystals. Contrasting patterns of some individual spherules are obvious between a front area with a crowd of hill-like prominences and a rear zone with one or more rings on the surface. Such surface features and internal textures suggest that they experienced movement at high temperature and then rapid cooling. Chemical compositions of the nuclei are homogenous and consist of nearly pure iron with minor Cr (<0.05 wt.%), Mn (<0.80 wt.%), and Ni (0.142-0.23 wt.%), and a trend of Ni decreasing and Cr increasing from core to cortex. Mn in the cortex (up to about 2.00 wt.%) is far more enriched than the nucleus. The bulk ratios (average) of δ⁵⁶Fe and δ⁵⁷Fe in the core and cortex are 0.51and 0.78, respectively. Such features suggest that there is a very low possibility of origin associated with volcanic explosive eruption, impact ejecta, chemical reduction or oxidation of iron on seafloor. Since biological reduction processes are not significant under high P/T condition in subduction zones, this origin is excluded. Considering their low Ni contents, it is more likely that they belong to the minor type-I deep-sea cosmic spherules/dusts of low isotope fractionation. This discovery shows that such spherules could remain stable under low-temperature and high-pressure conditions during recycling processes, and therefore could be found in rocks related to slab-derived sediments within subduction zones. This also suggests that subducted oceanic slab sediments contribute to the formation of jadeitite, coupled with dehydration of sediments and altered oceanic crust.  相似文献   

Review of geology, alteration and origin of iron oxide–apatite deposits in the Cretaceous Ningwu basin, Lower Yangtze River Valley, eastern China: Implications for ore genesis and geodynamic setting     

Jinjie Yu  Yuchuan Chen  Jingwen Mao  Franco Pirajno  Chao Duan 《Ore Geology Reviews》2011,43(1):170-181

In the Cretaceous Ningwu volcano-sedimentary basin in the Yangtze River Valley metallogenic belt, eastern China, there are three areas with a dense distribution of magnetite or hematite deposits: the Meishan deposit in the north; Washan, Nanshan and Taocun deposits in the center; and the Zhongjiu and Gushan deposits in the south. The mineralization in the Ningwu basin is associated mainly with subvolcanic intrusions, consisting of gabbro–diorite porphyry and/or gabbro–diorite. Alteration zoning of these deposits is pronounced, and includes: (1) an upper light colored zone of argillic, kaolinite, silica, carbonate and pyritic alteration (2) a middle dark colored zone of diopside, fluorapatite–magnetite, phlogopite, and garnet with fluorapatite–magnetite; (3) a lower light colored zone of extensive albitic alteration. However, at the Gushan iron deposit, the lower light colored zone and the middle dark colored zone are absent, whereas the principal alteration is represented by silicification, kaolinization, and carbonatization.The iron oxide–apatite deposits in the Ningwu basin are typically magmatic–metasomatic origin and are similar to the Kiruna-type deposits in Scandinavia, particularly with respect to mineral assemblages, fabric and structure of the iron ores, occurrence of the orebodies and wall rock alteration. The iron oxide–apatite deposits of the Ningwu basin contain magnetite and/or hematite, with diopside or actinolite and apatite gangue. They were formed in a rift or extensional environment and the mineralization is associated with alkaline magmatism. The time interval between magmatism and related mineralization is very short.  相似文献   

Mesozoic molybdenum deposits in the east Qinling–Dabie orogenic belt: Characteristics and tectonic settings     

J.W. Mao  F. Pirajno  J.F. Xiang  J.J. Gao  H.S. Ye  Y.F. Li  B.J. Guo 《Ore Geology Reviews》2011,43(1):264-293

The East Qinling–Dabie orogenic belt accommodates the largest Mo ore district in the world. It contains 8.43 Mt of proven Mo metal reserves which accounts for 66% of the total proven Chinese Mo reserves. The Mo ore district includes 24 deposits and 12 occurrences, with four major types of Mo mineral systems, i.e., porphyry, porphyry-skarn, skarn and hydrothermal veins. The latter can be further subdivided into quartz vein and carbonatite vein types. Although Mo mineralization in the belt began in the Paleoproterozoic (1680 ± 24 to 2044 ± 14 Ma), all economically significant deposits were formed during the Mesozoic. Re/Os dating of molybdenite has shown that there are three episodes of Mo mineralization, i.e., Late Triassic (233–221 Ma), Late Jurassic to Early Cretaceous (148–138 Ma) and Early to middle Cretaceous (131–112 Ma).Late Triassic Mo deposits developed as molybdenite–quartz veins and carbonatite vein types. Stable isotope systematics (C, O, S) and high contents of Re and Sr indicate that the carbonatite Mo veins are mantle-derived. Porphyry and porphyry–skarn Mo mineral deposits were formed in the Late Jurassic to Early Cretaceous and Early to middle Cretaceous. The Late Jurassic to Early Cretaceous granite porphyries that are associated with the Mo deposits usually occupy less than 1.5 km² at the surface and are situated in the East Qinling area, far west of China's continental margin. On the other hand, the Early to middle Cretaceous batholiths and granite porphyries, , with associated Mo deposits are located in the Dabieshan area and eastern part of the East Qinling area. The Late Jurassic to Early Creataceous granitoids and related Mo deposits possibly formed in a back-arc extensional setting of the Eurasian continental margin, which was probably triggered by the oblique subduction of the Izanagi plate. The Early to middle Cretaceous batholiths and granite porphyries are linked to the tectonic regime of lithospheric thinning, asthenospheric upwelling and partial melting of the crust, induced by a change in Izanagi Plate motion parallel to the continent margin.In the East Qinling–Dabie belt there are vein type Pb–Zn–Ag deposits surrounding porphyry and/or porphyry–skarn Mo (W) deposits, forming well defined ore clusters. The same spatial arrangement (i.e., porphyry Mo stockworks and outlying Pb–Zn–Ag ore veins) is also observed at the deposit scale. Thus, Mo porphyry stockworks and distal polymetallic veins belong to the same ore system and may reflect an outward temperature decrease from the highly fractionated granite plutons. Both, porphyry stockworks and polymetallic veins, can be used as vectors for further prospecting.  相似文献