"04·8"山东远距离台风暴雨成因的数值模拟

利用非静力平衡模式MM5,对由台风"艾利"和西风带冷空气相互作用造成的2004年8月26—28日山东大到暴雨天气过程进行了数值模拟,并对暴雨形成机理进行了分析。结果表明,"艾利"台风外围的急流带在华东沿海到山东南部地区产生深厚的湿层和强水汽辐合,从而导致不稳定能量的积聚;干冷空气从高层入侵使降水区对流不稳定增强,并使不饱和湿空气达到饱和,对降水具有增幅作用;低层正涡度和辐合作用的加强,导致中尺度低涡的形成和暴雨中心的产生。     

长江河口青草沙水库最长连续不宜取水天数

为解决上海日益增长的用水需求, 保障淡水资源安全, 需要建设长江河口避咸蓄淡特大型水库。本文应用改进的三维长江河口盐水入侵数值模式, 采用2007和2008年10个水文站盐度资料对模式进行验证, 计算青草沙水库最长不宜取水天数。本文以径流量特枯的1978—1979年作为水文计算年, 考虑三峡工程、南水北调东线工程和沿江引排水对大通实测逐日径流量的修正, 考虑潮汐、风应力和混合等作用。根据2003年地形计算得出青草沙水库的最长连续不宜取水天数为68天, 这个水库设计的重要参数已在水库建设中采用。根据2008年地形计算得出青草沙水库的最长连续不宜取水天数为54天, 已被水库调度采用。2003年至2008年北支上段河势发生了明显变化, 导致北支盐水倒灌减弱, 因此这期间的最长不宜取水天数减少。     

Optimal and sustainable extraction of groundwater in coastal aquifers

Four examples are investigated for the optimal and sustainable extraction of groundwater from a coastal aquifer under the threat of seawater intrusion. The objectives and constraints of these management scenarios include maximizing the total volume of water pumped, maximizing the profit of selling water, minimizing the operational and water treatment costs, minimizing the salt concentration of the pumped water, and controlling the drawdown limits. The physical model is based on the density-dependent advective-dispersive solute transport model. Genetic algorithm is used as the optimization tool. The models are tested on a hypothetical confined aquifer with four pumping wells located at various depths. These solutions establish the feasibility of simulating various management scenarios under complex three-dimensional flow and transport processes in coastal aquifers for the optimal and sustainable use of groundwater.     

安徽庐枞盆地中巴家滩岩体的岩石地球化学特征及成因

巴家滩岩体位于长江中下游庐枞中生代火山岩盆地的中心地带,出露面积约4km2.岩性主要为辉石二长岩和含英辉石二长岩,发育黄铁矿化和黄铜矿化.野外及室内证据表明该岩体可分为两期,第一期表现为闪长质岩石包体;第二期主要为旱阶段的辉石二长岩和晚阶段的含石英辉石二长岩.巴家滩岩体随着由早到晚的演化,其SiO2含量、总碱含量(Na2O K2O)和岩石的氧化度不断增高.稀土配分整体呈右倾趋势,轻稀土富集,重稀土分馏不明显.岩石学、稀土和微量元素地球化学特征表明巴家滩岩体成岩物质来源于富含金云母的富集地幔Ⅱ.巴家滩岩体属于橄榄玄粗岩系,形成于伸展构造环境.巴家滩岩体具有高Al2O2、Sr、St/Y、La/Yb,低Y、Yb、Sr正异常,Eu弱负异常,与沙溪岩体的特征相似,早期包体的Cu含量高达0.8402,推断在其深部可能有可能有类似沙溪岩体的矿化岩浆存在.     

How tides and river flows determine estuarine bathymetries

For strongly tidal, funnel-shaped estuaries, we examine how tides and river flows determine size and shape. We also consider how long it takes for bathymetric adjustment, both to determine whether present-day bathymetry reflects prevailing forcing and how rapidly changes might occur under future forcing scenarios.Starting with the assumption of a 'synchronous' estuary (i.e., where the sea surface slope resulting from the axial gradient in phase of tidal elevation significantly exceeds the gradient in tidal amplitude ), an expression is derived for the slope of the sea bed. Thence, by integration we derive expressions for the axial depth profile and estuarine length, L, as a function of and D, the prescribed depth at the mouth. Calculated values of L are broadly consistent with observations. The synchronous estuary approach enables a number of dynamical parameters to be directly calculated and conveniently illustrated as functions of and D, namely: current amplitude Û, ratio of friction to inertia terms, estuarine length, stratification, saline intrusion length, flushing time, mean suspended sediment concentration and sediment in-fill times.Four separate derivations for the length of saline intrusion, L_I, all indicate a dependency on (U_o is the residual river flow velocity and f is the bed friction coefficient). Likely bathymetries for `mixed' estuaries can be delineated by mapping, against and D, the conditions L<sub>I</sub>/L<1,E<sub>X</sub>/L<1 (E<sub>X</sub> is the tidal excursion) alongside the Simpson-Hunter criteria D/U<sup>3</sup><50 m<sup>−2</sup> s<sup>3</sup>. This zone encompasses 24 out of 25 `randomly' selected UK estuaries.However, the length of saline intrusion in a funnel-shaped estuary is also sensitive to axial location. Observations suggest that this location corresponds to a minimum in landward intrusion of salt. By combining the derived expressions for L and L_I with this latter criterion, an expression is derived relating D_i, the depth at the centre of the intrusion, to the corresponding value of U_o. This expression indicates U_o is always close to 1 cm s⁻¹, as commonly observed. Converting from U_o to river flow, Q, provides a morphological expression linking estuarine depth to Q (with a small dependence on side slope gradients).These dynamical solutions are coupled with further generalised theory related to depth and time-mean, suspended sediment concentrations (as functions of and D). Then, by assuming the transport of fine marine sediments approximates that of a dissolved tracer, the rate of estuarine supply can be determined by combining these derived mean concentrations with estimates of flushing time, F_T, based on L_I. By further assuming that all such sediments are deposited, minimum times for these deposition rates to in-fill estuaries are determined. These times range from a decade for the shortest, shallowest estuaries to upwards of millennia in longer, deeper estuaries with smaller tidal ranges.     

长江中下游金属矿找矿前景与找矿方法

本文论述了长江中下游地区金属矿床的地质、地球物理和地球化学特点,提出今后深部找矿的主要对象是：找隐伏含矿岩体及有关的各类矿体,找岩体中的大型斑岩型矿床,找受岩体和五通砂岩联合控制的层状矿;讨论了地球物理和地球化学方法应用中要注意解决的几个主要问题,强调应发挥包括重力、磁法、激发极化法、电磁法、岩性探测仪及多种天然地震法和化探方法等综合方法的作用,并与地质矿床成矿规律研究密切结合;讨论了方法应用试验中要注意的几个问题。文章最后一部分是从本区大地构造的演化探讨了区域构造岩浆活动与成矿前景,认为这一地区是扬子板块与华北板块陆-陆碰撞挤压造山带及其前陆区,在岩石圈强烈挤压下形成地壳增厚和深部物质的挤出折返,使深部的高压和超高压变质岩层推到地壳浅部;深部生成的柯石英等高压超高压矿物及地幔熔融岩浆同时上侵;生成大量钙碱性岩浆并存储在中地壳部位,通过长期与中下地壳金属物质进行交换,形成矿液的集中优势,通过后期出现的张性断裂构造而进入地壳表层,再经过与围岩发生物理化学成矿作用后沉淀成矿。归纳出扬子板块与华北板块陆-陆碰撞造山带一种新的构造模式。     

Thermochronology and exhumation rates of granitic intrusions at Mesa Central,Mexico

ABSTRACT

The Mesa Central of Mexico (MC) is an elevated plateau located 2000 m above sea level in central Mexico, where intrusions outcrop that register the history of exhumation-erosion occurring during the Late Cretaceous-Paleogene. The tectonic history of the region records formation of the Late Cretaceous-Paleogene ‘Mexican orogen’; this was followed by extension of the entire region and several plutons were then exhumed. The age and magnitude of the crustal uplift and erosion occurring during exhumation has not been addressed to date. Therefore, this study reports the crystallization and cooling ages of two plutons, the Tesorera Granodiorite and the Comanja Granite, and estimates their emplacement depths. Based on these data, the exhumation age of the Tesorera Granodiorite is estimated to be between ~73 Ma and ~63 Ma at an exhumation rate of ~528 m/m. y. and that of the Comanja Granite is 52 Ma and 48 Ma at an exhumation rate of ~2500 m/m. y. Exhumation-erosion event of the Tesorera Granodiorite was located on the trace of the San Luis-Tepehuanes Fault System and that of the Comanja Granite on the a trace of the El Bajío Fault System. Furthermore, the high exhumation rate in the Comanja Granite suggests that gravitational collapse played an important role during exhumation.     

Effects of geology and human activity on the dynamics of salt-water intrusion in three coastal aquifers in southern Spain

 Mathematical modelling of salt-water intrusion processes in three aquifers on the southern coast of Spain (Río Verde, Río Vélez and Castell de Ferro) reveals that, although all three systems are subject to the same climate and seasonal over-exploitation, geological and human factors have very different effects on the dynamics of contamination. In the Río Verde aquifer, the most important influence is the high volume of extractions occurring during the dry season; in Río Vélez, the intrusion is strongly controlled by infiltration of water from the river to the aquifer, and, in the Castell de Ferro system, an intensely karstified carbonate massif lying in contact with both the sea water and the detrital aquifer represents the main entrance point for influx of sea water and subsequent washing of the aquifer. We have undertaken a mathematical simulation of various possible measures to counteract intrusion, according to the specific characteristics of the process in each aquifer. These measures include artificial recharge, use of natural recharge from the river as a hydraulic barrier, and the construction of a low-permeability barrier. Received: 5 December 1995 · Accepted: 12 April 1996     

Thermal alteration of coal in the Khasyn coalfield, Magadan region, Russia

The Early Cretaceous coal deposits of the Khasyn coalfield are intruded by Palaeogene diabase dikes. The coal has vitrinite reflectance values of 2.0–2.5% R_o, and characteristics of normal anthracite at some distance from the dikes, but at direct contact with the dike two morphological coal varieties occur: coal inclusions in the diabase dike and dispersed carbonaceous matter within the dike rock. Both types of coaly matter have properties typical of anthracites: strong anisotropy, altered internal structure and high vitrinite reflectance values ranging from 3.8 to 5.5% R_o. The X-ray diffraction measurements of the interplanar spacing d(002) and the crystallite sizes Lc and La show rather similar values for coal inclusions in the dike and dispersed carbonaceous matter. The additional reflection at 3.37 Å, corresponding to semi-graphite admixture, occurs in the coal and carbonaceous matter inside the dike and is absent in the natural coal outside the dike.     

Sinkhole hazards along the eastern Dead Sea shoreline area, Jordan: a geological and geotechnical consideration

For the last four decades, the level of the Dead Sea has been subjected to continual variation which, among other important factors, has led to the occurrence of much subsidence and many sinkholes in the southern Dead Sea area. Sinkhole activities occurred repetitively and were observed in open farms, across roads, near dwellings and near an existing factory, thus causing a serious threat to the locals and farmers of the area and their properties. This paper presents the main results from detailed geological and geotechnical studies of this area. Aerial photo interpretation and borehole drilling aided these studies. Parallel geophysical investigations (vertical electrical sounding and seismic refraction) and hydrological and hydrogeological studies were made by others in the same area to also investigate this phenomenon. It was found that sinkholes are aligned to and follow old water channels and are concentrated parallel to the recent shoreline of the Dead Sea. The development of subsurface cavities is associated mainly with the variation in the level of the Dead Sea over the four past decades, the presence of regional salt intrusion under the surface of salt beds, the fluctuation of the water table and continuous dissolution and the active tectonism of the area. Moreover, this work showed that the area is still under active sinkhole hazards and other parts of the area will be inevitably affected by sinkholes in the future.No practical engineering solution to this problem is feasible. Received: 1 July 1999 / Accepted: 11 October 1999