相山铀矿田成矿作用的地球化学模拟

相山铀矿田是我国最大的火山岩型热液铀矿田，在地质地球化学和高温高压实研究的基础上，利用地球化学模式程序ＥＱ３／６模拟了成矿热水溶液的形成过程和减压排泄区铀成矿作用。计算机模拟结果表明，通过大气降水与碎斑熔岩相互作用，可以形成富含Ｆ和ＳｉＯ２等矿化剂的含铀热水溶液；由于铀以ＵＯ２Ｆ＾３和ＵＯ２（ＣＯ３（＾２－３等配合形式存在，非常稳定，即使在深部强还原环境中仍能能够迁移；酸性和碱性环境，尤其是强酸性     

RILL EROSION PROCESS ON STEEP SLOPE LAND OF THE LOESS PLATEAU

IntheLoessPlateau,alongtheslopelengthfromthetoptothebottom,soilerosionischaracterizedbyobviousverticalzonaldivision,thatis,sheeterosionzone,sheeterosionandrillerosionzone,rillerosionandshallowgullyerosionzoneandgullyerosionzone.Inthesheetandrillero..sionzone,rillerosionamounttakesup70%ofthetotalsoilloss[TANGKenetal.,1983,ZHENGFenlietal.,19871;intherillandshallowgullyerosionzone,rillerosionamountaccountsfor30--40%ofthetotalsoilloss.Sorillerosionisamajorerosionpatternonsteepslopeland.Riller…     

Magnetostratigraphy and palaeoclimate of Red Clay sequences from Chinese Loess Plateau

Two Red Clay profiles near Xi’an and Xifeng were investigated in an attempt to determine magnetostratigraphic and palaeoclimatic records. The results show that aeolian dust accumulation and the related East Asia palaeomonsoon system had begun by 6.5 Ma, and it is deduced that the Tibetan Plateau had reached a significant elevation at that time. The late Tertiary palaeoclimatic history of the Red Clay as reflected by magnetic susceptibility is reconstructed during the period of 6.5–2.5 Ma. Stepwise increase in susceptibility of aeolian dust accumulation appears to have a close correlation to the uplift processes of the Tibetan Plateau. The remarkable increase of aeolian dust accumulation at 3.2 Ma appears to be due to the influence of global ice volume on the East Asia monsoon. Palaeomonsoon variation during the late Tertiary as recorded in the Red Clay sequences from the Chinese Loess Plateau can be regarded as the product of a number of interacting factors, such as uplift of the Tibetan Plateau, solar radiation, global ice volume, etc. Project supported by the National Natural Science Foundation of China and the Foundation of Xi’an Laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences.     

静海地震台地磁短周期变化及其在地震短临预报中的应用

近年来的一些研究表明，由于地震前孕震区地下介质的电性结构的变化，将导致地磁短周期转换函数发生异常变化。通过对地震前后的地磁短周期转换函数的参数的计算、分析和研究，有可能提取出可靠的地震短临前兆异常（曾小苹等，１９９０）。为了进一步开展对该方法研究工作并使其在我区地震预测预报研究中得到应用，我们使用了静海台的地磁记录资料，分析计算了该台地磁短周期转换函数在地震前后的变化情况，确立了该方法应用天津地区地震预报的短临异常特征及指标，取得了较好的效果。     

关于银山矿床成矿作用的几个问题——兼与《江西银山铜铅锌金银矿床》的作者商榷

银山多金属矿床是一个特大型火山—潜火山热液矿床,具有复杂的多期多阶段的成矿作用和有序的成矿分带。成矿作用主要为火山—潜火山热液作用,但在此之前,还经历了一期由韧脆性剪切带形成而引起的动力变质热液作用。根据矿体与3个旋回潜火山岩体的时空关系,火山—潜火山热液成矿作用又可分为两个成矿期和5个成矿阶段。矿床地质地球化学研究表明成矿作用在空间上具有定向迁移的特点,结合流体动力学计算机数值模拟认为定向迁移的根本原因是构造岩浆脉动和隐伏岩体形态产状。笔者认为,矿区深部可能有隐伏岩体,但对隐伏的斑岩铜矿床不应抱很大希望     

大地电磁场的两种大震短临异常

根据中法电磁合作台运行6年的资料，在年变形态对比的基础上合理地选取有效测道值构建了相应的时间序列图。从中发现昆仑山口西8．1级大震前一个多月时间中，正常大地电磁场中叠加间歇性畸变干扰，按形态分为‘阶跃突跳’、‘单尖突变’两种类型。简略地讨论了产生两种异常现象的可能机制。     

Seasonal and Diurnal Variation of Surface Ozone and a Preliminary Analysis of Exceedance of its Critical Levels at a Semi-arid Site in India

The mixing ratios of surface O₃ were measured at St. John's College, Agra, an urban and traffic influenced area for the period of 2000–2002. The monthly averaged O₃ mixing ratios ranged between 8 to 40 ppb with an annual average of 21 ppb. Strong diurnal and seasonal variations in O₃ mixing ratios were observed throughout the year except for monsoon season. The mixing ratios of O₃ follow the surface temperature cycle and solar radiation (r = 0.72 and r = 0.65 with temperature and solar radiation, respectively). Concentrations were higher with winds associated with NE and NW direction indicating the impact of pollution sources on surface O₃ concentration. Exceedance of ozone critical level was calculated using the AOT 40 index and found to be 840 ppb.h and 2430 ppb.h for summer and winter seasons, respectively. The present O₃ exposures are lower than the critical level of O₃ and suggest that the present level of O₃ does not have any impact on reduction in crop yields.     

Simulation Experiments of Land Surface Physical Processes and Ecological Effect over Different Underlying Surface

Based on the existing Land Surface Physical Process Models(Deardorff, Dickinson, LIU, Noilhan, Seller, ZHAO), a Comprehensive Land Surface Physical Process Model (CLSPPM) is developed by considering the different physical processes of the earth‘s surface-vegetation-atmosphere system more completely. Compared with SiB and BATS, which are famous for their detailed parameterizations of physical variables, this simplified model is more convenient and saves much more computation time. Though simple, the feas...     

Water exchange between Tokyo Bay and the Pacific Ocean during winter

Variability in water-exchange time between Tokyo Bay and the Pacific Ocean during winter is investigated based on the results of intensive field observation from November 2000 to March 2001. Water-exchange time between Tokyo Bay and the Pacific Ocean during winter mainly depends on the strength of northerly monsoon, being about 16 days under the weak monsoon and about 12 days under the strong monsoon. Moreover, it becomes longer by about 1 day in spring tide and shorter in neap tide due to the coupling effect of estuarine circulation and vertical mixing. Water-exchange time also varies depending on the open-ocean condition. When the warm water mass approaches from the Pacific Ocean to the mouth of Tokyo Bay through the eastern channel of Sagami Bay, which connects Tokyo Bay and the Pacific Ocean, water-exchange time becomes longer by about 2 days because the warm water mass is blocked in the surface layer at the bay mouth. On the other hand, when the warm water mass approaches to the mouth of Tokyo Bay through the western channel of Sagami Bay, water-exchange time becomes shorter by about 1 day because the warm water mass intrudes into the middle or lower layers of Tokyo Bay. Such different behavior of warm water mass at the mouth of Tokyo Bay is due to the difference in density of approaching warm water masses, that is, the density of the warm water mass through the eastern channel is smaller than that of the warm water mass through the western channel of Sagami Bay.Responsible Editors: Yens Kappenberg     

Global scale annual and semi-annual variations of daytime NmF2 in the high solar activity years

The annual and semi-annual variations of the ionosphere are investigated in the present paper by using the daytime F2 layer peak electron concentration (NmF2) observed at a global ionosonde network with 104 stations. The main features are outlined as follows. (1) The annual variations are most pronounced at magnetic latitudes of 40–60° in both hemispheres, and usually manifest as winter anomalies; Below magnetic latitude of 40° as well as in the tropical region they are much weaker and winter anomalies that are not obvious. (2) The semi-annual variations, which are usually peak in March or April in most regions, are generally weak in the near-pole regions and strong in the far-pole regions of both hemispheres. (3) Compared with their annual components, the semi-annual variations in the tropical region are more significant.In order to explain the above results, we particularly analyze the global atomic/molecular ratio of [O/N2] at the F2 layer peak height by the MSIS90 model. The results show that the annual variation of [O/N2] is closely related with that of NmF2 prevailing in mid-latitudes and [O/N2] annual variation usually may lead to the winter anomalies of NmF2 occurring in the near-pole region. Moreover, NmF2 semi-annual variations appearing in the tropical region also have a close relationship with the variation of [O/N2]. On the other hand, the semi-annual variations of NmF2 in the far-pole region cannot be simply explained by that of [O/N2], but the variation of the solar zenith angle may also have a significant contribution.