长江中下游晚中生代中基性岩的铅同位素特征:富集地幔的证据

长江中下游东段庐枞、怀宁、繁昌、铜陵和宁芜地区的中基性岩属于碱性系列 ,具有高的U ,Th含量和Th/Pb ,U/Pb比值 ,分别平均为 2 .82× 10 -6,9.5 6× 10 -6和 0 .6 35 ,0 .184。样品的初始铅同位素 (130Ma)组成为 :(2 0 6Pb/ 2 0 4Pb) i=17.6 5～ 18.6 0 ,(2 0 7Pb/ 2 0 4Pb) i=15 .4 2～ 15 .5 0 ,(2 0 8Pb/ 2 0 4Pb) i=37.6 7～ 38.0 4。形成中基性岩的原始岩浆来源于富集的岩石圈地幔 ,具有EMⅠ和EMⅡ ,且以EMⅡ为主的特征。和长江中下游西段黄石地区以及大别地块西南部玄武岩的比较表明 ,长江中下游地区岩石圈地幔高的Th/Pb和U/Pb比值可能和俯冲板片析出流体的交代有关。晚中生代时期 ,华北板块岩石圈地幔以EMⅠ特征为主 ,华南板块岩石圈地幔以EMⅡ特征为主 ,岩石圈地幔性质的区域性分布与印支期扬子板块深俯冲事件密切相关。虽然中国东部新生代玄武岩因岩石圈大规模减薄表现了亏损特征 ,但残留的富集岩石圈地幔在中国东部新生代玄武岩的Pb同位素中仍有所反映     

Dynamical response to supernova-induced gas removal in spiral galaxies with dark matter halo

We investigate the dynamical response, in terms of disc size and rotation velocity, to mass loss by supernovae in the evolution of spiral galaxies. A thin baryonic disc having the Kuzmin density profile embedded in a spherical dark matter halo having a density profile proposed by Navarro, Frenk & White is considered. For the purpose of comparison, we also consider the homogeneous and   r ⁻¹  profiles for dark matter in a truncated spherical halo. Assuming for simplicity that the dark matter distribution is not affected by mass-loss from discs and the change of baryonic disc matter distribution is homologous, we evaluate the effects of dynamical response in the resulting discs. We found that the dynamical response only for an adiabatic approximation of mass-loss can simultaneously account for the rotation velocity and disc size as observed particularly in dwarf spiral galaxies, thus reproducing the Tully–Fisher relation and the size versus magnitude relation over the full range of magnitude. Furthermore, we found that the mean specific angular momentum in discs after the mass-loss becomes larger than that before the mass-loss, suggesting that the mass-loss would most likely occur from the central disc region where the specific angular momentum is low.     

相态研究在化探异常评价中的应用——以马架子水系沉积物异常评价为例

利用相态研究可确定异常元素的赋存状态,马架子水系沉积物综合异常强度高,浓集中心明显,经过几次异常检查及查证,未获得良好的找矿效果,引起异常的成因机制不清。对异常样品中元素在氧化物相、结合相及硫化物相中分配的综合研究证实,Ph、Zn元素主要是以均匀分散形式存在于岩石中,为非矿致异常,从而节省了大量的人力、财力及物力,为异常查证及评价提供了一套新的思路。     

Geodynamic setting,structure, and composition of continuous trachybasalt-trachyandesite-rhyolite series in the north of Altai-Sayan area: the role of crust-mantle interaction in continental magma formation

The geologic positions and geochemical and isotope parameters of the Ordovician-early Silurian and Early-Middle Devonian continuous volcanic series of the Minusa basin and its mountainous framing are compared. Both series are composed mostly of moderately alkaline rocks with variations in SiO₂ contents from 45 to 77 wt.%. The Ordovician-early Silurian series differs from the Early-Middle Devonian one in lower contents of TiO₂ (< 1.7 wt.%) and Fe₂O_3tot and higher contents of Al₂O₃ in all rock varieties and in the more fractionated REE patterns of trachybasalts. The compositions of both series reflect two simultaneous mechanisms of magma evolution. The main process was fractional crystallization leading to the formation of rocks from trachybasalts to trachyrhyodacites. The accessory mechanism was the contamination of fractionated melts by crustal material, anatectic melting of crust, and mixing of deep-seated magmas with crustal melts. These processes had specifics at each stage and were controlled by the composition of the sources of parental melts. Their geochemical and isotopic parameters (high alkalinity, high contents of lithophile elements, negative anomalies of Nb, Ta, and Ti, and enrichment in radiogenic Sr) point to the interaction of mantle plumes with the lithospheric mantle that was metasomatically transformed during the preceding Vendian-early Cambrian subduction processes.     

Effects of adjusting cropping systems on utilization efficiency of climatic resources in Northeast China under future climate scenarios

Quantitatively evaluating the effects of adjusting cropping systems on the utilization efficiency of climatic resources under climate change is an important task for assessing food security in China. To understand these effects, we used daily climate variables obtained from the regional climate model RegCM3 from 1981 to 2100 under the A1B scenario and crop observations from 53 agro-meteorological experimental stations from 1981 to 2010 in Northeast China. Three one-grade zones of cropping systems were divided by heat, water, topography and crop-type, including the semi-arid areas of the northeast and northwest (III), the one crop area of warm–cool plants in semi-humid plain or hilly regions of the northeast (IV), and the two crop area in irrigated farmland in the Huanghuaihai Plain (VI). An agro-ecological zone model was used to calculate climatic potential productivities. The effects of adjusting cropping systems on climate resource utilization in Northeast China under the A1B scenario were assessed. The results indicated that from 1981 to 2100 in the III, IV and VI areas, the planting boundaries of different cropping systems in Northeast China obviously shifted toward the north and the east based on comprehensively considering the heat and precipitation resources. However, due to high temperature stress, the climatic potential productivity of spring maize was reduced in the future. Therefore, adjusting the cropping system is an effective way to improve the climatic potential productivity and climate resource utilization. Replacing the one crop in one year model (spring maize) by the two crops in one year model (winter wheat and summer maize) significantly increased the total climatic potential productivity and average utilization efficiencies. During the periods of 2011–2040, 2041–2070 and 2071–2100, the average total climatic potential productivities of winter wheat and summer maize increased by 9.36%, 11.88% and 12.13% compared to that of spring maize, respectively. Additionally, compared with spring maize, the average utilization efficiencies of thermal resources of winter wheat and summer maize dramatically increased by 9.2%, 12.1% and 12.0%, respectively. The increases in the average utilization efficiencies of precipitation resources of winter wheat and summer maize were 1.78 kg hm⁻² mm⁻¹, 2.07 kg hm⁻² mm⁻¹ and 1.92 kg hm⁻² mm⁻¹ during 2011–2040, 2041–2070 and 2071–2100, respectively. Our findings highlight that adjusting cropping systems can dominantly contribute to utilization efficiency increases of agricultural climatic resources in Northeast China in the future.     

Early J2 basalts in SE China: Incipience of large-scale late Mesozoic magmatism

Magmatism in SE China was dormant during 204–180 Ma, but was reactivated in 180–170 Ma (early J₂), and then became more and more intensive towards the end of early Cretaceous. The small-scale early J₂ magmatism is the incipience to long-term and large-scale magmatism in this region. A near east-west (EW) trend volcanic belt was distributed across south Hunan, south Jiangxi and southwest Fujian was formed during early J₂ time. Along this belt from the inland toward the coast, the lithology of basalts changes from alkali into tholeiite, and the amount of erupted volcanic rocks and the proportions of rhyolites coexisting with the basalts increase. On the basis of geochemical characteristics of these basalts, we infer that the melting degree of source rocks and the extent of fractional crystallization and crustal contamination all increased whereas the depth of mantle source decreased from the inland to the coast, which led to the variations of geological characteristics of the volcanic belt. In early J₂, the western spreading Pacific plate began to subduct underneath SE China continental block, reactivating near EW trend deep fault that was originally formed during the Indosinian event. The stress of the western spreading Pacific plate and the extent of asthenosphere upwelling increased from the inland to the coast, which is consistent with the generation and evolution of early J₂ basalts.     

鄂温克旗干旱、洪涝灾害期评定及预测方法

根据鄂温克旗1959—2008年气象历史资料,统一归类,并采用统计预报方法,简要评定预测出鄂温克旗50年来主要气象灾害之一的干旱、洪涝灾害期,为鄂温克旗防范旱涝灾害做参考。     

深圳市景亿山庄滑坡特征及成因分析

根据现场工程地质调查和勘察,论文深入分析了景亿山庄滑坡的变形特征、性质、变形机制,并探讨了滑坡的成因。指出在具有剥蚀残丘地貌特征的场地开挖以砂岩残积物为主要组成物质的边坡时,边坡高陡是造成边坡变形破坏的主要因素。长时间的持续降雨是诱发因素。对于陡倾原生节理裂隙发育的土质和类土质边坡,滑坡周界受边坡体内原生节理裂隙控制,滑坡后缘常沿该陡倾的节理裂隙发育。在深圳等降雨量大的亚热带气候区,若坡体内没有不利于边坡稳定的各种结构面,当边坡开挖高度不超过20m,总体坡率不陡于1∶1时,边坡能够保持短期稳定。但长期稳定性受当地降雨量和降雨强度的控制,开挖后若不采取适当的加固措施,易发生滑坡等浅层病害。其病害从孕育到发生可持续长达10a之久。通过论文的研究,可供在类似地区开挖边坡、整治边坡病害借鉴。     

Biofacies analysis of Upper Cretaceous deposits in the Ust-Yenisei region: Implications of palynomorphs

The results of palynomorph biofacies analysis in the Upper Cretaceous deposits of the Ust-Yenisei region are presented. The established facies confinement and indicative features of separate palynomorph groups are used, along with identified dinocyst morphotypes and taxa, in paleogeographic reconstructions. Seven palynomorph associations characterizing continental, coastal-marine, shallow-and deep-water facies are distinguished based on quantitative proportions between morphological groupings and individual taxa. As boundaries between distinguishable biostratigraphic and facies subdivisions do not coincide, dinocysts were likely insignificantly dependent in distribution on facies in the West Siberian epicontinental basin at least. On the other hand, distribution trends of particular dinocyst morphotypes and other microphytofossils are correlative with transgressive-regressive cycles and can be used for reconstruction of paleoenvironments.     

厄尔尼诺现象与黄、东海,对马海域马面渔获量关系─—长江口及其邻近海区ENSO渔场学问题之三

对黄,东海及其邻近海域马面历年（1974—1986年）渔获量变化与Elnino现象关系并结合捕捞强度进行一些初步分析,总结出渔获量变化规律,为合理开发渔业资源提供有用信息。