实验岩石学对埃达克岩成因的限定——兼论中国东部富钾高Sr/Y比值花岗岩类

大量变玄武岩脱水熔融实验表明,制约埃达克岩形成的主要因素是源岩、水和地壳热结构(p-T轨迹)。变玄武岩低到中等程度(10％～40％)的部分熔融过程中,含水矿物(主要是角闪石)脱水反应产生埃达克岩熔体,残余相组合为石榴石+单斜辉石±斜方辉石±角闪石(没有斜长石)。在俯冲带,当压力为1.6～2.2 GPa(约70～90 km)和温度为800～1150℃时,具有高的剪切热速率和非常年轻的(<25 Ma)、热的俯冲大洋岩石圈就会发生脱水熔融形成埃达克熔体。在增厚地壳内,具有高的热状态的底侵玄武质下地壳在压力≥0.8 GPa(>35 km)和温度介于800～1100℃之间发生部分熔融形成埃达克质熔体。然而,中国东部晚中生代富钾高Sr/Y比值花岗岩类,可能形成于加厚地壳开始减薄及地壳从挤压向拉张伸展转换的环境下,所对应的岩浆,与下地壳底侵的碱性玄武岩和/或拉斑玄武岩在压力1.0～1.5 GPa和温度850～1080℃之间发生部分熔融有关,熔融的残余相为辉石岩类,岩浆在上升侵位过程中还受到了地壳AFC的影响。中国东部中生代岩石圈从加厚转变为减薄的过程,就可能与玄武质岩浆的底侵作用及随后含石榴石辉石岩类残余体的拆沉作用有关。     

大别山南、北坡花岗岩风化作用的差异及其构造、气候环境意义

对大别山南、北坡燕山期花岗岩风化壳研究表明: 南坡司空山黑云母二长花岗岩风化壳为剥蚀型风化壳, 在水解作用以及酸性介质条件下脱碱、钙、硅和富铝, 主要矿物学演化是长石、黑云母风化蚀变为伊利石→(蛭石→1.4 nm过渡矿物)→高岭石→多水高岭石. 北坡河棚黑云母正长花岗岩风化壳为稳定型风化壳, 在氧化作用以及弱酸偏中性介质条件下无硅的淋失、富铁和非晶化作用显著, 主要矿物学演化是长石、黑云母转变为蒙脱石、多水高岭石→非晶质. 这些结果显示, 大别山南、北坡风化作用的差异可能与气候条件和构造运动的差异有关, 即, 南坡高温多雨, 淋溶强烈, 土壤处于酸性环境, 经历过构造抬升; 北坡高温少雨, 淋溶较弱, 土壤处于弱酸偏中性环境.     

地震通信网络安全刍议

本文介绍了地震通信网络在安全方面采用的措施，如操作系统安全策略，路由器安全策略，防火墙，VLAN技术，IDS入侵检测系统等，同时，对地震通信网络未来安全的一些措施进行了探讨，浅议了双网计算机，物理隔离技术，网络隐患扫描技术和PKI技术，期望地震通信网络安全问题能够得到各个方面的重视。     

Comparison of an algebraic multigrid algorithm to two iterative solvers used for modeling ground water flow and transport

Numerical solution of large-scale ground water flow and transport problems is often constrained by the convergence behavior of the iterative solvers used to solve the resulting systems of equations. We demonstrate the ability of an algebraic multigrid algorithm (AMG) to efficiently solve the large, sparse systems of equations that result from computational models of ground water flow and transport in large and complex domains. Unlike geometric multigrid methods, this algorithm is applicable to problems in complex flow geometries, such as those encountered in pore-scale modeling of two-phase flow and transport. We integrated AMG into MODFLOW 2000 to compare two- and three-dimensional flow simulations using AMG to simulations using PCG2, a preconditioned conjugate gradient solver that uses the modified incomplete Cholesky preconditioner and is included with MODFLOW 2000. CPU times required for convergence with AMG were up to 140 times faster than those for PCG2. The cost of this increased speed was up to a nine-fold increase in required random access memory (RAM) for the three-dimensional problems and up to a four-fold increase in required RAM for the two-dimensional problems. We also compared two-dimensional numerical simulations of steady-state transport using AMG and the generalized minimum residual method with an incomplete LU-decomposition preconditioner. For these transport simulations, AMG yielded increased speeds of up to 17 times with only a 20% increase in required RAM. The ability of AMG to solve flow and transport problems in large, complex flow systems and its ready availability make it an ideal solver for use in both field-scale and pore-scale modeling.     

培养跨世纪的地震科技人才队伍

依据我国防震减迷十年目标任务和地震科技“九五”计划及２０１０年长远发展规划的实施,就面向２１世纪大力开展继续教育活动,培养与造就跨世纪的地震科技人才队伍,提高其整体素质方面谈几点认识和建议。     

Video observations, atmospheric path, orbit and fragmentation record of the fall of the Peekskill meteorite

Large Near-Earth-Asteroids have played a role in modifying the character of the surface geology of the Earth over long time scales through impacts. Recent modeling of the disruption of large meteoroids during atmospheric flight has emphasized the dramatic effects that smaller objects may also have on the Earth's surface. However, comparison of these models with observations has not been possible until now. Peekskill is only the fourth meteorite to have been recovered for which detailed and precise data exist on the meteoroid atmospheric trajectory and orbit. Consequently, there are few constraints on the position of meteorites in the solar system before impact on Earth. In this paper, the preliminary analysis based on 4 from all 15 video recordings of the fireball of October 9, 1992 which resulted in the fall of a 12.4 kg ordinary chondrite (H6 monomict breccia) in Peekskill, New York, will be given. Preliminary computations revealed that the Peekskill fireball was an Earth-grazing event, the third such case with precise data available. The body with an initial mass of the order of 10(4) kg was in a pre-collision orbit with a = 1.5 AU, an aphelion of slightly over 2 AU and an inclination of 5 degrees. The no-atmosphere geocentric trajectory would have lead to a perigee of 22 km above the Earth's surface, but the body never reached this point due to tremendous fragmentation and other forms of ablation. The dark flight of the recovered meteorite started from a height of 30 km, when the velocity dropped below 3 km/s, and the body continued 50 km more without ablation, until it hit a parked car in Peekskill, New York with a velocity of about 80 m/s. Our observations are the first video records of a bright fireball and the first motion pictures of a fireball with an associated meteorite fall.     

1991年3月26日5.8级地震的磁效应初探

本文将华北地区1990年10月—1991年4月地磁核旋定点观测数据利用加权差分法和带通滤波处理提取地震磁效应。发现1991年3月26日山西大同发生Ms5.8级地震的地磁前兆异常和同震异常现象。