对云山异常金成矿远景的分析     

孙中任  赵雪娟  吕长生 《物探与化探》2005,29(3):217-219,236

通过对云山异常区的区域构造、地质条件的了解,以及对该区地球物理、地球化学资料的分析,认为这是一处值得关注的异常区,并指出异常区中的磁异常的地质起因极可能为剖析这一异常带来转机。  相似文献   

地面综合物探方法在浅覆盖区地质填图单元的划分研究   总被引：2，自引：0，他引：2       下载免费PDF全文

刘菁华  王祝文 《中国地质》2005,32(1):162-167

由于浅覆盖区的特殊地貌，给区域地质填图带来一定的困难。本文依据不同岩性的磁化率和放射性元素含量差异，讨论了不同填图单元地面磁法测量与地面伽玛能谱测量曲线关系。通过实测剖面的分析，得到大兴安岭火成岩区不同填图单元磁测异常曲线与放射性异常曲线的相关关系，从而用来快速确定浅覆盖区下填图单元边界，以减少槽探工程，减轻地质人员的工作强度。  相似文献   

高速公路桥头跳车病害的分析与治理方法探讨     

王万顺耿玉岭  王争明袁巧红 《中国煤田地质》2005,17(5):78-80

根据高速公路桥头跳车病害探地雷达检测结果,结合路基实际工程地质资料及沉降观测值,分析出造成此病害的原因是桥与路之间沉降差异所致,故搭板与垫层和垫层与路基之间产生了脱空,造成桥搭板、垫层碎裂而出现了桥头跳车病害.针对病害根源,采用了压密注浆进行搭板加固及重新摊铺沥青混合料进行调坡处理的治理方法.  相似文献   

内蒙古中部重、磁场特征与地壳密度结构   总被引：2，自引：2，他引：2  

张季生  洪大卫王涛 《地质通报》2005,24(2):118-123

中亚造山带中的古生代——中生代花岗岩普遍具有正εNd值，在世界上是十分独特的。美国西部加利福尼亚中生代-新生代花岗岩同样具有正εNd值，并且其地壳的速度分布特征与内蒙古中部十分相似。本文通过与美国加利福尼亚的地球物理研究成果进行对比，来研究内蒙古中部的地壳密度结构，特别是下地壳的组成，试图探讨产生正￡。值花岗岩的深部地质原因。研究结果表明，在大兴安岭-内蒙古造山带下地壳中可能存在与美国加里福尼亚类似的洋壳物质。此外，还对重、磁异常进行了处理，以确定蛇绿岩带的延展情况。由于在西拉木伦河附近存在切割至莫霍面的深断裂，结合地表出现的蛇绿岩带，故提出温都尔庙-西拉木伦河一线可能是内蒙古中部最重要的地质构造界线。  相似文献   

宁镇地区中更新世环境演变的沉积学研究   总被引：6，自引：0，他引：6  

张强  朱诚  房迎三 《沉积学报》2002,20(2):307-313

句容放牛山剖面ESR测年、粒度以及磁化率的研究结果表明,下蜀黄土作为一种受后生成土作用强烈的风尘堆积,其性状与北方黄土差别很大,主要表现为由于成壤作用及次生风化作用导致粘粒含量增多。该剖面揭示出本区中更新世 5个气候暖湿期,分别是 :15 9~ 16 3ka,192ka,195~ 198ka,2 0 3~ 2 30ka与 311~ 35 0ka。其中第一个相对暖湿期不十分明显,在大致同时期的深海氧同位素 (V2 1- 14 6孔 ) 6阶段当中为一个小的气候回暖波动,第 2、3、4气候暖湿期可大致与西峰黄土S2古土壤层所反映的气候温暖事件相对应,可与深海氧同位素 (V2 1- 14 6孔 )第 7氧同位素阶段大致相对比。其中,前 4个温暖期可大致与老虎山下蜀黄土的标准剖面自上而下的 4个埋藏古土壤层相对应。旧石器考古发掘发现 6、7层有石器,从剖面测年资料及各环境代用指标综合分析得出,当时为暖湿的生态环境(即第 5个气候暖湿期 ),较适宜人类活动,与南京汤山猿人洞研究结果相一致。东北地区庙后山下层文化 (14 0 0~2 30ka)以大石片石器为主,文化面貌兼有华北大小两个石器系统的特征。这与该遗址发掘的石器相类似,这可能说明至少在中更新世中期长江河道应在句容以南。  相似文献   

Parameter identification of inelastic structures under dynamic loads     

Haochuan Zhang  Greg C. Foliente  Yongmin Yang  Fai Ma 《地震工程与结构动力学》2002,31(5):1113-1130

The generalized model of differential hysteresis contains 13 control parameters with which it can curve‐fit practically any hysteretic trace. Three identification algorithms are developed to estimate the control parameters of hysteresis for different classes of inelastic structures. These algorithms are based upon the simplex, extended Kalman filter, and generalized reduced gradient methods. Novel techniques such as global search and internal constraints are incorporated to facilitate convergence and stability. Effectiveness of the devised algorithms is demonstrated through simulations of two inelastic systems with both pinching and degradation characteristics in their hysteretic traces. Owing to very modest computing requirements, these identification algorithms may become acceptable as a design tool for mapping the hysteretic traces of inelastic structures. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Mantle structure and rifting processes in the Baikal–Mongolia region: geophysical data and evidence from xenoliths in volcanic rocks     

Dmitri Ionov   《Tectonophysics》2002,351(1-2)

The origin of the Baikal rift zone (BRZ) has been debated between the advocates of passive and active rifting since the 1970s. A re-assessment of the relevant geological and geophysical data from Russian and international literature questions the concept of broad asthenospheric upwelling beneath the rift zone that has been the cornerstone of many “active rifting” models. Results of a large number of early and recent studies favour the role of far-field forces in the opening and development of the BRZ. This study emphasises the data obtained through studies of peridotite and pyroxenite xenoliths brought to the surface by alkali basaltic magmas in southern Siberia and central Mongolia. These xenoliths are direct samples of the upper mantle in the vicinity of the BRZ. Of particular importance are suites of garnet-bearing xenoliths that have been used to construct P–T- composition lithospheric cross-sections in the region for the depth range of 35–80 km.Xenolith studies have shown fundamental differences in the composition and thermal regime between the lithospheric mantle beneath the ancient Siberian platform (sampled by kimberlites) and beneath younger mobile belts south of the platform. The uppermost mantle in southern Siberia and central Mongolia is much hotter at similar levels than the mantle in the Siberian craton and also has significantly higher contents of ‘basaltic’ major elements (Ca, Al, Na) and iron, higher Fe/Si and Fe/Mg. The combination of the moderately high geothermal gradient and the fertile compositions in the off-cratonic mantle appears to be a determining factor controlling differences in sub-Moho seismic velocities relative to the Siberian craton. Chemical and isotopic compositions of the off-cratonic xenoliths indicate small-scale and regional mantle heterogeneities attributed to various partial melting and enrichment events, consistent with long-term evolution in the lithospheric mantle. Age estimates of mantle events based on Os–Sr–Nd isotopic data can be correlated with major regional stages of crustal formation and may indicate long-term crust–mantle coupling. The ratios of ^143/144Nd in many LREE-depleted xenoliths are higher than those in MORB or OIB source regions and are not consistent with a recent origin from asthenospheric mantle.Mantle xenoliths nearest to the rift basins (30–50 km south of southern Lake Baikal) show no unequivocal evidence for strong heating, unusual stress and deformation, solid state flow, magmatic activity or partial melting that could be indicative of an asthenospheric intrusion right below the Moho. Comparisons between xenoliths from older and younger volcanic rocks east of Lake Baikal, together with observations on phase transformations and mineral zoning in individual xenoliths, have indicated recent heating in portions of the lithospheric mantle that may be related to localised magmatic activity or small-scale ascent of deep mantle material. Overall, the petrographic, P–T, chemical and isotopic constraints from mantle xenoliths appear to be consistent with recent geophysical studies, which found no evidence for a large-scale asthenospheric upwarp beneath the rift, and lend support to passive rifting mechanism for the BRZ.  相似文献   

Heat flow and thermal modeling of the Yinggehai Basin, South China Sea   总被引：9，自引：0，他引：9  

Lijuan He  Liangping Xiong  Jiyang Wang 《Tectonophysics》2002,351(3)

Geothermal gradients are estimated to vary from 31 to 43 °C/km in the Yinggehai Basin based on 99 temperature data sets compiled from oil well data. Thirty-seven thermal conductivity measurements on core samples were made and the effects of porosity and water saturation were corrected. Thermal conductivities of mudstone and sandstone range from 1.2 to 2.7 W/m K, with a mean of 2.0±0.5 W/m K after approximate correction. Heat flow at six sites in the Yinggehai Basin range from 69 to 86 mW/m², with a mean value of 79±7 mW/m². Thick sediments and high sedimentation rates resulted in a considerable radiogenic contribution, but also depressed the heat flow. Measurements indicate the radiogenic heat production in the sediment is 1.28 μW/m³, which contributes 20% to the surface heat flow. After subtracting radiogenic heat contribution of the sediment, and sedimentation correction, the average basal heat flow from basement is about 86 mW/m².Three stages of extension are recognized in the subsidence history, and a kinematic model is used to study the thermal evolution of the basin since the Cenozoic era. Model results show that the peak value of basal heat flow was getting higher and higher through the Cenozoic. The maximum basal heat flow increased from 65 mW/m² in the first stage to 75 mW/m² in the second stage, and then 90 mW/m² in the third stage. The present temperature field of the lithosphere of the Yinggehai Basin, which is still transient, is the result of the multistage extension, but was primarily associated with the Pliocene extension.  相似文献   

Unstable Climate Oscillations during the Late Holocene in the Eastern Bransfield Basin, Antarctic Peninsula     

Boo-Keun Khim  Ho Il Yoon  Cheon Yun Kang  Jang Jun Bahk 《Quaternary Research》2002,58(3):234

Core A9-EB2 from the eastern Bransfield Basin, Antarctic Peninsula, consists of pelagic (diatom ooze-clay couplets and bioturbated diatom ooze) and hemipelagic (bioturbated mud) sediments interbedded with turbidites (homogeneous mud and silt–clay couplets). The cyclic and laminated nature of these pelagic sediments represents alternation between the deposition of diatom-rich biogenic sediments and of terrigenous sediments. Sediment properties and geochemical data explain the contrasting lamination, with light layers being finer-grained and relatively rich in total organic carbon and biogenic silica content. Also, the high-resolution magnetic susceptibility (MS) variations highlight distinct features: high MS values coincide with clastic-rich sections and low MS values correspond to biogenic sections. The chronology developed for core A9-EB2 accounts for anomalous ages associated with turbidites and shows a linear sedimentation rate of approximately 87 cm/10³ yr, which is supported by an accumulation rate of 80 cm/10³ yr calculated from ²¹⁰Pb activity. The late Holocene records clearly identify Neoglacial events of the Little Ice Age (LIA) and Medieval Warm Period (MWP). Other unexplained climatic events comparable in duration and amplitude to the LIA and MWP events also appear in the MS record, suggesting intrinsically unstable climatic conditions during the late Holocene in the Bransfield Basin of Antarctic Peninsula.  相似文献   

厚层覆盖区综合物化探方法找金试验研究——以广西兴安金石金矿为例     

胡云沪  罗先熔  王桂琴  杜建波  张小路 《矿产与地质》2002,(5)

在兴安金石金矿外围 4号分散流异常区 ,通过地电化学提取金测量法 ,查明测区存在 5个走向规模小于 5 0 m的金异常区 ,W( Au) 最大值为 72 .4× 10 - 9,高出背景值十几倍 ,并藉综合土壤吸附汞测量 ,高精度磁测和激发极化法等多种物化探方法来确定这些异常区的地质、地球化学和地球物理特征 ,提出金矿成矿的有利部位在金的地电提取高异常区、高汞量异常区、高磁性异常区、低视电阻率异常区和中等视极化率异常区的“三高一低一中”的找矿模式。确定测区的北北东角 (右下角 )一带具备有利的金矿成矿条件  相似文献