火山作用与银矿化

我国与火山作用有关的银矿床占大、中型银矿床总数的33.5 %。燕山旋回是我国与火山岩和潜火山岩有关的银矿最重要的成矿期。这类银矿几乎都产于深大断裂边缘或次级构造交汇部位、 地槽区海相火山活动地带及地台活化区陆相火山活动地带。硅化和钠化与银矿化最为密切。矿液中的Au、Pb、Sc、Mn、Cd对银的成矿作用有积极影响。银在矿石中的分布特点显示,矿石中95%以上的银呈独立银矿物存在,方铅矿、闪锌矿和黄铜矿是银的最重要载体矿物,这为银的充分回收利用提供了地质依据。     

准噶尔盆地中部下侏罗统三工河组二段沉积相及储层特征

准噶尔盆地中部下侏罗统三工河组二段广泛发育三角洲相。二段下部在研究区东北部以大型辫状河三角洲前缘沉积夹滑动浊流沉积为特征,西部以扇三角洲沉积为特征,在中部两者交汇叠加。二段上部在东北部和西部都为曲流河三角洲前缘亚相沉积,在区中部交汇叠加。三工河组二段砂岩发育大量原生孔隙和次生孔隙,为有利储层。沉积微相类型控制砂体储集性能,成岩作用对砂岩储集性的改造并不强烈。二段下部的辫状河三角洲前缘河道微相及扇三角洲前缘河道微相具有大孔中渗的特点,为Ⅰ、Ⅱ类储层;上部的曲流河三角洲前缘分支河道及前缘席状砂微相,具中孔中、低渗的特点,为Ⅱ和Ⅲ类储层。     

地质统计学中变差函数参数估计的新方法

遗传算法是一种模拟生物进化规律的全局优化算法。对传统的遗传算法进行改进,并应用于地质统计学变差函数参数估计中。实例分析表明,该方法简便、通用,具有较高拟合精度,是非线性、不连续可微模型参数估计的方法     

干旱区内陆河流域不同特征居民对气候变化及冰冻圈变化的感知差异分析——以乌鲁木齐河流域为例

选择冰川典型发育的乌鲁木齐河流域,基于面向普通民众的657份调查问卷,将气候变化与冰冻圈变化有机的结合起来,尝试分析不同特征民众对二者变化的感知差异状况,为因地制宜制定适应性措施以及普通民众有计划、有目的地调整生产和生活策略,适应未来环境变化等提供公众参与的社会依据.调查结果显示,乌鲁木齐河流域不同特征居民之间有着复杂...     

Inferred ultrahigh-temperature metamorphism of amphibolitized olivine granulite from the Sør Rondane Mountains, East Antarctica

This paper reports the first evidence of ultrahigh-temperature (UHT) metamorphism from the Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, which is evident as orthopyroxene + spinel symplectite in an amphibolitized mafic granulite. The granulite consists of olivine, orthopyroxene, clinopyroxene, pargasitic amphibole, plagioclase, and ilmenite, and it possesses a within-plate alkali basalt signature. The local bulk chemical composition of symplectite, major and trace element compositions, and thermodynamic calculations for the symplectite, suggest the presence of garnet at the high-pressure stage and that the symplectite formed from garnet, olivine, and primary orthopyroxene by decompression from more than 12 kbar at 1000 °C. The granulite records a subsequent amphibolite-facies overprint (<700 °C at <6 kbar) that involved the chemical re-equilibration of several phases. The obtained pressure–temperature (P–T) conditions and P–T path are different from the UHT metamorphism from the Schirmacher Hills, central Dronning Maud Land, which is considered to have occurred in a back-arc tectonic setting. The relatively high-P conditions and the decompression path reconstructed in the present study are similar to those reported for southern India, Sri Lanka, and part of northeastern Mozambique, possibly reflecting continental thickening and exhumation during the main collision event between East and West Gondwana.     

Dating Quaternary volcanism and incision by the River Tigris at Diyarbakır,southeast Turkey

New high‐precision Ar‐Ar dating of basalt underlying the city of Diyarbak?r, southeast Turkey, constrains the Quaternary incision history of the River Tigris, strengthening the pre‐existing chronology based on magnetostratigraphy and K‐Ar dates. The basalt, which overlies Tigris terrace gravel 70 m above the river, is part of the Karacada? shield volcano complex centred ca. 60 km to the southwest. The reverse‐magnetised Diyarbak?r basalt, one of relatively few flow units to reach the Tigris valley axis, has been dated to 1196 ± 19 ka (±2σ). Two lower terraces have been recognised in the Diyarbak?r area, 46 and 32 m above the present river, with at least one other further downstream. From this evidence the rate of Middle‐Late Pleistocene incision by the Tigris can be estimated; it probably reached ca. 0.07 mm a^?1, reflecting the characteristic global increase in uplift rates observed at that time. Copyright © 2007 John Wiley & Sons, Ltd.     

我国天文视宁度Fried参数r0的计算与统计分析

在塔塔尔斯基理论模式下，使用全国81个探空气象站1986—1995年10年探空资料计算了各测站不同高度上的Pried参数r0，统计结果表明，r0年平均值存在明显的地理分布，高值中心在3000m高度上是夏河合作、丽江和上海；在1500m高度上为民勤和贵阳，在900m高度上为汉中；在测站海拔高度上为定日，r0的月平均值的地理分布存在显著的季节变化，这种变化与东亚副热带急流季节性变化相吻合．     

微波介电陶瓷BaO-Nd2O3-TiO2发展状况及探索

对高频高介的微波陶瓷 ,主要是性能优越的BaO Nd2 O3 TiO2 系统发展状况、现状和趋势进行综述介绍     

天山乌鲁木齐河源1号冰川消融对气候变化的响应

Current glacier recession under the global warming has aroused world-wide attention.Initiated from 1958,the observations show that over the past 50 years,the glacier has changed remarkably in the aspects of snow-firn stratigraphy,ice formation zone,ice temperature,area and terminus position,etc.These changes are apparently the results of temperature rise in this area.The glacier recession continued throughout the entire observed time period,and showed an accelerated tendency since 1985.Meltwater runoff also increased 84.2% over the last 20 years.     

Stochastic models for simulation of strong ground motion in Iceland

Two types of modelling approaches for simulating ground motion in Iceland are studied and compared. The first type of models, named discrete‐time series models (ARMA), are based solely on measured acceleration in earthquakes occurring in Iceland. The second type of models are based on a theoretical seismic source model called the extended Brune model. Based on measured acceleration in Iceland during the period 1986–1996, the parameters for the extended Brune models have been estimated. The seismic source models are presented here as ARMA models, which simplifies the simulation process. A single‐layer soil amplification model is used in conjunction with the extended Brune model to estimate local site amplification. Emphasis is put on the ground motion models representing the variability in the measured earthquakes, with respect to energy, duration and frequency content. Demonstration is made using these models for constructing linear and non‐linear probabilistic response spectra using a discretised version of the Bouc–Wen model for the hysteresis of the second‐order system. Copyright © 2001 John Wiley & Sons, Ltd.