共查询到20条相似文献，搜索用时 31 毫秒
1.
中国地震局系统期刊编排质量分析 总被引：1，自引：0，他引：1
以中国地震局系统公开出版发行的２５种学术类、综合类期刊为研究样本,对照有关文献工作的国家标准、规范,对这些期刊的开本、封面、条码、书脊、目次表、摘要、关键词、分类号、序号、量和单位、数字和日期、数学和物理公式、图、表、总目次和索引、项眉、作者简介、收稿日期、参考文献表、版权标识、印刷装帧等情况进行了统计分析,得出地震期刊编排质量大体符合国家标准,规范的结论,指出了存在的问题,提出了进一步加强地硅期进编排标准化、规范化工作的建议。 相似文献
2.
湖冰光谱特征是湖冰遥感反演的物理基础,是研究湖冰光学特性和空间分布的理论依据。本文以查干湖为例,使用ASD Field Spec 4便携式地物光谱仪采集冰封期不同类型湖冰、积雪和水体光谱,利用Savitzky-Golay滤波法和包络线去除法分析白冰、灰冰、黑冰、雪冰、积雪和水体的反射光谱特征,探索气泡对湖冰反射光谱特征的影响。积雪和雪冰、白冰和灰冰、黑冰和水体的反射特征随着波长的变化特征基本一致,冰的反射率介于积雪和水体之间,其中白冰的反射率高于灰冰和黑冰,在包络线去除结果中,黑冰和水体在440 nm吸收谷处的吸收面积为5.184和10.878、吸收深度为0.052和0.106,雪、雪冰、白冰、灰冰在800和1030 nm吸收谷处的吸收面积和吸收深度的变化表现为雪<雪冰<灰冰<白冰。气泡是影响湖冰光谱特征的重要因素,气泡使白冰反射率减小和黑冰反射率增大,并且气泡使得白冰在800/1030nm和黑冰在440 nm处的吸收面积和吸收深度减小,其中气泡大小和疏密程度的不同会导致湖冰反射率的影响程度存在差异。同时,本文选取时间同步的Landsat 8 OLI遥感影像,在完成辐... 相似文献
3.
基于2007年6月3日云南宁洱6.4级地震现场近场强震与流动数字地震观测、各类建筑结构及生命线工程震害调查、政府及民众应急处置与响应调查等基础工作,结合云南多年积累的大量地震现场调查资料与认识,开展了震区各类建筑结构及生命线工程震害特征与机理、强震动观测与地震烈度分布关系、灾区恢复重建资金评估方法、政府应急处置与普通群众个体认知状况以及地壳结构、震源特性、强震动频谱与农居抗震调查等方面的综合分析与研究等工作。归纳和总结了可供我国其它多震地区在城市发展规划、工程结构抗震、地震应急管理和地震灾区恢复重建等领域参考和借鉴的技术、方法、措施和经验。 相似文献
4.
实际的地球介质十分复杂,远非当今人们所采用的理想模型可以概括,因为其属性和结构的变异是非均匀、非线性和各向异性的.在研究地球内部壳幔介质与结构、构造与属性差异、金属矿产资源和油、气、煤能源的勘查中,无论是区域构造格局、岩相和结构特征(如裂缝、破碎带、不同尺度的洞穴以及一些不规则几何体)均十分复杂.近年来基于成山、成盆、成矿、成岩和成灾研究的不断深化,对地下介质各向异性的研究受到广泛的关注.地震波动传播理论和介质与结构的物理属性研究结果表明:地震各向异性在成因上主要是由岩石、矿物和晶体的晶格优势取向、应力场异常变异和构造裂缝与深部物质运移造成的.为此,本文对14次地震各向异性会议的主体内涵进行分析,在此基础上,指出了在各向异性研究的发展进程中、特别是在应用中尚存在着的一些问题.在深化认识地球内部物质物理属性的基础上,探讨了S波分裂和偏振效应与地震各向异性与介质结构分区、构造活动,油气田勘探与岩相特征,裂隙与构造精细刻划和地震活动区(带)深部介质与构造环境的深层过程和动力学响应的关系.最后提出了地震各向异性在地球物理学发展中的作用和今后的任务. 相似文献
5.
本文首先简要介绍了地震现场建筑物安全性鉴定辅助决策系统的定义、用途及发展现状,并阐释了将其应用于地震现场中的作用、方法及意义。此外,还介绍了此辅助系统的功能和设计分析及该系统的层次结构,重点介绍了该系统的计算模型及其理论根据以及模型算法分析。深入研究了辅助系统的功能、业务流程和总体设计,讨论了系统的需求、数据的采集与管理、模型计算、结果输出、查询、统计和分析等功能,并简要介绍了辅助系统的界面设计方法及界面框图,同时对系统的进一步扩展提出了看法。 相似文献
6.
The Tarim Desert Highway in Xinjiang, China, the longest one in the world, has a lengthof 562 km, about 80% of which runs across, from north to south, the Taklimakan Desert. Obviously,the main problem of the road maintenance is the blown sand disaster. The research resultsshowed: (1) the physical environment along thedesert highway is characterized by strong winds,fine and loose ground materials, different dunes and so on, which provides the dynamical conditionand material source for the formation of blown sand disaster to the road and its shelter system.Meanwhile, the trend and cross-section of the road and the structure of the shelter system, asdamage objects, play important roles in the formation process of blown sand disaster; (2) theblown sand disaster to the shelter system is original from the intrusion of the drift sands and mobiledunes outside the shelter system, and the wind erosion and sand deposit caused by the air streamchanges on the ground in the shelter system. The main damage object in the Tarim Desert High-way is the shelter system presently. The damage forms include wind erosion, sand burying anddune covering; and (3) the damaged length of the blocking sand fences is 83.7%, 88.4%, 72.4%,72.8% and 40.3% and the damaged area of the straw checkerboard belts is 73.1%, 58.2%, 44.5%,35.4% and 36.6%, in turn, in 5 different landform units from north to south, and, the disasters tofences and the straw checkerboard belts are 79.5% and 57.6% in the compound dunes while theyare 64.6% and 37.7% in the interdunes respectively. 相似文献
7.
尼泊尔8.1级地震对中国西藏地区造成的震害特征分析 总被引：1，自引：0，他引：1
2015年4月25日尼泊尔发生8.1级地震,对我国西藏地区造成较大人员伤亡与房屋破坏,道路、通讯等生命线工程及水利等基础设施损坏严重。本文介绍了本次地震的基本情况,并在现场地震烈度调查和地震损失评估的基础上,对灾区震害进行了分析,给出了灾区房屋类别与破坏情况以及生命线系统与各行业的受损情况。通过分析此次地震的灾害特点,指出了灾区在抗震设防中存在的问题,并提出加大地震地质灾害的防治力度,科学编制恢复重建规划,加强防震减灾宣传,提高农牧民抗震设防意识,加强农牧区房屋建筑的指导和监管等建议,以减少地震造成的人员伤亡和财产损失,促进西藏地区经济和社会的和谐发展。 相似文献
8.
利用收集到的各种来源共计7 959组的地震各向异性观测数据和21 750组应力场数据,结合板块绝对运动模型计算给出的各板块的运动规律,分别统计分析了板块运动与地震各向异性及应力场的相关性,并对板块运动对地震各向异性及应力场特征产生的影响进行了分析． 统计结果表明,阿拉伯、 加勒比、 胡安德富卡、 北美、 纳兹卡、 太平洋和南美板块上地震各向异性与板块运动均具有较好的相关性,而非洲、 南极洲、 澳大利亚、 欧亚、 印度和菲律宾板块上二者的相关性则相对较差. 讨论分析发现,板块运动拖动软流圈流动、 橄榄岩晶格优选方位、 化石各向异性和地幔流动或岩石圈流动等因素均在一定程度上控制并影响着地震各向异性与板块运动的一致性． 而板块基底拖曳力、 洋脊推力、 浮力作用和碰撞及俯冲作用等多种因素共同制约了板块运动与应力场的相关性,使得非洲、 可可斯、 欧亚、 胡安德富卡、 北美、 纳兹卡、 菲律宾和南美板块上二者的相关性较好,其它板块上其相关性则较差． 对于俯冲带地区,由于俯冲机制的复杂性和软流圈、 岩石圈地幔流动方向的不确定性,其板块运动与地震各向异性及应力场的相关性图像表现复杂,需要结合具体的俯冲带构造进行近一步研究． 相似文献
9.
Hinterland intermountain basins and northern and southern piedmonts of the Qinling Mountains accumulated a large amount of loess during the Pleistocene. The loess strata not only record local paleogeographic and paleoenvironmental changes, but also contain rich hominin fossils and Paleolithic remains. In the northern piedmont of the Qinling Mountains and the lower valley of the South Luohe River, the loess strata have multi loess-paleosol sequences with aeolian loess continuously accumulating during glacial and interglacial cycles. In contrast to the northern piedmont, loess stratigraphy in the hinterland intermountain basins of the Qinling Mountains is relatively thin and contains finer loess particles. In this “mini” type of loess stratum, the density of Paleolithic remain generally is higher than the Loess Plateau in the north of the Qinling Mountains. Based on stratigraphic, chronological, and lithic artifacts analysis in recent years, it appears that the regional lithic assemblage belongs to the Oldowan (Mode I) lithic industry, and it is dominated by choppers, cores, flakes, and simple retouched flake tools from 1.15 to 0.6 Ma. Paleolithic open-air sites such as Gongwangling and Chenjiawo in the Lantian area, Shangbaichuan and Liuwan in the Luonan Basin, Qiaojiayao in the Lushi Basin, Longgangsi and Yaochangwan in the Hanzhong Basin, Guanmiao in the Ankang Basin, and the Yunxian Man Site in the Yunxian Basin are representative sites in the region; from 400 to 250 ka, the Longyadong cave site in the Luonan Basin inherited the characteristics of the local Mode I lithic industry, the stone assemblage is made up of cores, flakes, and small retouched flake tools, such as scrapers, points, and burins; during the period from 250 to 50 ka, bi-facially retouched Acheulean tools (Model II), such as hand-axes, picks, and cleavers, were commonly found in the Qinling Mountains region. The emergence of a large number of Model II artifacts indicates that local lithic industries went through a major transition process. Zhanghuokou, Guoyuan, and Huaishuping sites in the Luonan Basin, Diaozhai, Ganyu, Laochihe, and Xiehu sites in the Lantian area, Hejialiang site in the Hanzhong Basin are representative sites in this period; to the turn of the Late Pleistocene and Early Holocene, it may also exist a small flake-retouched tools lithic industry in the piedmonts of the northern and southern sides of the Qinling Mountains. The lithic assemblages in different stages of the Qinling Mountains region reflect the hominin behavioral changes and the development of lithic technology during the Pleistocene. 相似文献
10.
基于湖库水质目标的流域氮、磷减排与分区管理——以天目湖沙河水库为例 总被引：9，自引：3，他引：6
湖库水环境保护在保障生产与生活用水、维系生态平衡、发展旅游等方面发挥着重要的作用.水质目标管理是保护湖库水质的最佳管理办法.本文以天目湖地区沙河水库及其流域为研究区域,建立模型模拟沙河水库流域的水文与水质,评估入库污染通量和主要来源;依据水质目标测算氮、磷污染的容量和减排量,结合土地的生态保护与开发适宜性评估,提出氮、磷污染分区减排和土地管控的对策和措施.研究结果表明,沙河水库氮、磷污染物入库通量分别为206.01和3.29 t/a,面源总氮和总磷分别占总入库量的85.7%和67.5%.不同土地利用类型氮、磷输出强度有显著差异,总氮输出强度依次为茶园 >耕地 >建筑用地 >裸地 >草地 >退耕地 >林地 >河湖漫滩,总磷输出强度与地表覆盖度有关,依次为裸地 >建筑用地 >茶园 >耕地 >草地 >退耕地 >林地和河湖漫滩.从氮、磷输移过程来看,沙河水库流域总氮排放量为321.64 t/a,进入河流的为255.53 t/a,在河道输送过程中损失19.4%,最终有206.01 t/a进入水库;沙河水库流域总磷排放量为13.42 t/a,进入河流的为7.90 t/a,在河道输送过程中损失58.3%,最终有3.29 t/a进入水库.不同分区河流氮、磷滞留降解率有很大的差异,中田河总氮、总磷滞留降解能力最强,分别为34.71%和84.31%.2009年的通量计算结果显示,沙河水库总氮达到Ⅳ类水质目标需要的入湖减少量为32.01 t/a,入湖削减比例为15.50%,总氮达到Ⅲ类水质目标需要的入湖减少量为59.66 t/a,入湖削减比例为29.00%;总磷达到Ⅲ类水需要的入湖减少量为0.682 t/a,入湖削减比例为20.70%,总磷达到Ⅱ类水需要的入湖减少量为1.479 t/a,入湖削减比例为44.90%.为了实现基于土地利用的面源污染减排管控,选定植被覆盖度、水源涵养能力、地形坡度、土地利用、氮磷分区贡献量、与道路和村落距离等指标综合评估生态保护价值和开发适宜性,并划定禁止开发区、限制开发区和保护性开发区3个管理分区,最终确定各分区的开发强度限制和管控方式. 相似文献
11.
From Earthquake Prediction Research to Time-Variable Seismic Hazard Assessment Applications 总被引：1，自引：0，他引：1
Peter Bormann 《Pure and Applied Geophysics》2011,168(1-2):329-366
The first part of the paper defines the terms and classifications common in earthquake prediction research and applications. This is followed by short reviews of major earthquake prediction programs initiated since World War II in several countries, for example the former USSR, China, Japan, the United States, and several European countries. It outlines the underlying expectations, concepts, and hypotheses, introduces the technologies and methodologies applied and some of the results obtained, which include both partial successes and failures. Emphasis is laid on discussing the scientific reasons why earthquake prediction research is so difficult and demanding and why the prospects are still so vague, at least as far as short-term and imminent predictions are concerned. However, classical probabilistic seismic hazard assessments, widely applied during the last few decades, have also clearly revealed their limitations. In their simple form, they are time-independent earthquake rupture forecasts based on the assumption of stable long-term recurrence of earthquakes in the seismotectonic areas under consideration. Therefore, during the last decade, earthquake prediction research and pilot applications have focused mainly on the development and rigorous testing of long and medium-term rupture forecast models in which event probabilities are conditioned by the occurrence of previous earthquakes, and on their integration into neo-deterministic approaches for improved time-variable seismic hazard assessment. The latter uses stress-renewal models that are calibrated for variations in the earthquake cycle as assessed on the basis of historical, paleoseismic, and other data, often complemented by multi-scale seismicity models, the use of pattern-recognition algorithms, and site-dependent strong-motion scenario modeling. International partnerships and a global infrastructure for comparative testing have recently been developed, for example the Collaboratory for the Study of Earthquake Predictability (CSEP) with test regions in California, Italy, Japan, New Zealand, and the Western Pacific. Algorithms and data bases are operated in a permanently learning and upgrading mode. Future perspectives and research requirements and the feasibility and possible problems encountered with the implementation of earthquake predictions in practice are briefly summarized. 相似文献
12.
在青藏高原的地球科学研究中,国外科技界曾提出过六大论点——喜马拉雅山脉是地壳均衡的典范;青藏高原地壳乃是两个地壳的垂向重叠;雅鲁藏布江是印度洋板块和欧亚板块的缝合带;青藏高原西部的南北走向断裂带全为裂谷带;青藏高原腹地深部物质的向东逃逸;青藏高原下地壳物质通道流以及汶川MS8.0大地震的发生.这一系列论点确为国人广为引用与跟随,并发表了若干篇论著.然而在不断理解和深化研究的基点上提出了质疑,并基于新的认识提出了新的论点与论据,且在科学理念上给予了重新厘定.因为科学是为宇宙提供真正的写真. 相似文献
13.
For the activities of the mining industry land, equipment, material, and energy are used. During operation material and energy flows such as overburden, dead rock, tailings, wastewater, exhaust air, dust, energy, abrasion, coolant and lubricant losses, are released. These released material and energy flows are nearly always without value for the raw material supply chain as they are not production targets. Instead, they have negative effects on the economy and ecology and are, therefore, referred to as ‘non-intended’. The knowledge of the quantities and qualities of these non-intended outputs as a function of the processes and their parameters is the basis for technical and economical measures. A methodology for the acquisition and assessment of the material and energy flows in the mining industry was developed and tested at the Technical University Berlin, Germany. For that purpose and based on a system analysis in different mines, all relevant material and energy flows were assigned to individual processes. Causal relationships, possible interactions, quantities, and qualities were examined as functions of system parameters. Finally, a technical and economic evaluation was performed. 相似文献
14.
以福州市活断层信息管理系统为例,提出了城市活断层探测信息系统建设的目标,分析了以GIS技术为支持的、面向对象的设计方法及系统结构与功能。系统在局域网内采用C/S模式,在广域网中采用B/S模式,具有用户界面、应用程序和基础数据的3层结构。探测成果数据库按照分类、分层存贮,按专题组织查询的方式管理。城市活断层探测信息管理系统以活断层探测成果数据库为基础,空间分析为支撑,集地质、地球物理、地球化学、综合查询及专题分析应用为一体,具备活断层探测及分析研究成果分类与综合查询、展示、分析等功能,这一系统的建立可为活断层研究的定量化提供坚实的数据基础与技术平台,为城市规划、土地利用等防震减灾工作的开展提供科学依据 相似文献
15.
The Wenchuan earthquake occurred near the "triple junction" linking the Bayan Har block, the South China block, and the Sichuan-Yunnan rhombic block, and its influences on the surrounding blocks and the main fault zones in the Sichuan-Yunnan region, i.e., the block boundary zone, cannot be ignored. In this paper, changes of movement and stress of the fault zones before and after a strong earthquake were simulated based on the GPS repetition survey results recently obtained during 1999–2007, 2009–2011, and 2011–2013 with a two-dimensional finite-element contact model and the "block- loading" method. The results show that, before the Wenchuan earthquake, the movement of the Longmenshan fault zone was very slow and its compressive stress accumulated rapidly; after the Wenchuan earthquake, movements toward the E-SSE direction of the Bayan Har, southwestern Yunnan, and rhombic blocks were enhanced, and the dextral and horizontal compressive speeds and annual accumulative compressive stress of the Longmenshan fault zone increased markedly by factors of 4.5, 2.1, and 2.5, respectively. The southern Xianshuihe, Anninghe, Zemuhe, Daliangshan, and Lijiang-Xiaojinhe fault zones accumulated compressive stress rapidly, forming enhanced compressive stress zones along a NE strike crossing the central part of the Sichuan-Yunnan region. The tensional movement of the Xianshuihe fault zone was enhanced and the slip movement in the central part of the zone was reversed in a short time. The changes are tightly related to the medium-intensity earthquakes that occurred during the same period in this region, revealing that the spatial migration of seismic activity is related to changes of movement of the blocks. 相似文献
16.
由于人口过速增长和不合理的传统发展模式等种种原因,江西历史上也出现过山区毁林种粮、湖区盲目围垦和酷渔滥捕等短期行为,造成了水土流失严重,旱涝灾害频繁,生态环境恶化,资源利用效率低,经济发展缓慢等区域性的环境与发展不协调问题,对江西的社会经济发展构成了日益严重的威胁.始于20世纪80年代初的江西省山江湖工程,应用流域综合管理理念和生态经济理论,以流域为单元,按照流域水土等自然资源的发育与退化规律,流域的物质循环、能量流动、信息传递和价值增殖规律,系统考虑流域内人口、资源与环境间的相互关系,在全面规划的基础上,合理安排农、林、牧副各业用地和组织布局生产力,因地制宜地布设综合治理措施,对水土及其他自然资源进行保护、改良与合理利用,寻求恢复和保持鄱阳湖流域生态系统良性循环,为实现流域内经济、社会与环境协调发展而进行的_次探索与实践.本文总结了江西省山江湖工程过去近二十年来在鄱阳湖流域综合管理方面所取得的成功经验和方法,以供其他类似地区参考和借鉴. 相似文献
17.
南沙东部海域构造位置特殊,油气资源丰富,其构造过程对认识南海形成演化意义重大.由于地质条件复杂、资料分布不均,其地层系统和主要构造变革面属性认识尚不清楚,尤其具有断坳转换性质的裂陷结束不整合面地质时代和意义存在诸多争议.本文在综合国内外地层划分方案的基础上,运用连井剖面对比、地震相类比方法,对该海域多道地震资料进行系统的构造-地层综合解释,重点厘定了T7、T6和T5三个与裂陷结束相关的不整合面.研究表明,裂陷结束不整合面具有抬升剥蚀、断块掀斜、挠曲变形、拆离滑脱、沉积相突变等特征,且具有东北早西南晚,南侧靠陆早、北侧近洋晚的带状时空迁移规律.结合南海构造演化、地层岩性和沉积环境变化分析裂陷结束不整合面的构造含义,认为该界面是南海岩石圈破裂、洋脊跃迁、挠曲前隆、陆陆碰撞、扩张停止等一系列构造事件在不同构造位置单次或多次叠加的构造-沉积响应. 相似文献
18.
Silvia Maria Caglierani Casanova Eliana Aparecida Panarelli Raoul Henry 《Limnologica》2009,39(4):292-301
Rotifera density, biomass, and secondary production on two marginal lakes of Paranapanema River were compared after the recovery of hydrologic connectivity with the river (São Paulo State, Brazil). Daily samplings were performed in limnetic zone of both lakes during the rainy season immediately after lateral inflow of water and, in the dry period, six months after hydrologic connectivity recovery. In order to identify the factors that affect rotifer population dynamics, lake water level, volume, depth, temperature, transparency, dissolved oxygen, pH, alkalinity, conductivity, suspended solids, nutrients, and chlorophyll-a were determined. Variations of water physical and chemical factors that affect rotifer population were related to the lake-river degree of connection and to water level rising after drought. The water lateral inflow from the river resulted in an increase in lake water volume, depth, and transparency and a decrease in water pH, alkalinity, and suspended solids. The lake with the wider river connection, more frequent biota exchange, and larger amount of particulate and dissolved materials was richer and more diverse, while rotifer density, biomass, and productivity were lower in both periods studied. Density, biomass, and secondary production were higher in the lake with the smaller river connection and the higher physical and chemical stability. Our results show that the connectivity affects the limnological stability, associated to seasonality. Stable conditions, caused by low connectivity in dry periods, were related with high density, biomass and secondary production. Conversely, instability conditions in rainy periods were associated to elevated richness and diversity values, caused by exchange biota due to higher connectivity. 相似文献
19.
LIMITATION OF CURRENT TECTONIC DEFORMATION MODES IN THE WESTERN MARGIN OF ORDOS BASED ON SEISMIC ACTIVITY CHARACTERISTICS 
下载免费PDF全文
下载免费PDF全文 ZHAN Hui-li ZHANG Dong-li HE Xiao-hui SHEN Xu-zhang ZHENG Wen-jun LI Zhi-gang 《地震地质》1979,42(2):346-365
Due to the interaction between the Tibetan plateau, the Alxa block and the Ordos block, the western margin of Ordos(33.5°~39°N, 104°~108°E)has complex tectonic features and deformation patterns with strong tectonic activities and active faults. Active faults with different strikes and characteristics have been developed, including the Haiyuan Fault, the Xiangshan-Tianjingshan Fault, the Liupanshan Fault, the Yunwushan Fault, the Yantongshan Fault, the eastern Luoshan Fault, the Sanguankou-Niushoushan Fault, the Yellow River Fault, the west Qinling Fault, and the Xiaoguanshan Fault.
In this study, 7 845 earthquakes(M≥1.0)from January 1st, 1990 to June 30th, 2018 were relocated using the double-difference location algorithm, and finally, we got valid locations for 4 417 earthquakes. Meanwhile, we determined focal mechanism solutions for 54 earthquakes(M≥3.5)from February 28th, 2009 to September 2nd, 2017 by the Cut and Paste(CAP)method and collected 15 focal mechanism solutions from previous studies. The spatial distribution law of the earthquake, the main active fault geometry and the regional tectonic stress field characteristics are studied comprehensively.
We found that the earthquakes are more spatially concentrated after the relocation, and the epicenters of larger earthquakes(M≥3.5) are located at the edge of main active faults. The average hypocenter depth is about 8km and the seismogenic layer ranges from 0 to 20km. The spatial distributions and geometry structures of the faults and the regional deformation feature are clearly mapped with the relocated earthquakes and vertical profiles. The complex focal mechanism solutions indicate that the arc-shaped tectonic belt consisting of Haiyuan Fault, Xiangshan-Tianjingshan Fault and Yantongshan Fault is dominated by compression and torsion; the Yellow River Fault is mainly by stretching; the west Qinling Fault is characterized by shear and compression. The structural properties of the fault structure are dominated by strike-slip and thrust, with a larger strike-slip component. The near-north-south Yellow River Fault is characterized by high angle NW dipping and normal fault motion.
Based on small earthquake relocation and focal mechanism solution results, and in combination with published active structures and geophysical data in the study area, it is confirmed that the western margin of Ordos is affected by the three blocks of the Tibetan plateau, the Alax and the Ordos, presenting different tectonic deformation modes, and there are also obvious differences in motion among the secondary blocks between the active faults. The area south of the Xiangshan-Tianjingshan Fault has moved southeastward since the early Quaternary; the Yinchuan Basin and the block in the eastern margin of the Yellow River Fault move toward the SE direction. 相似文献
20.
New Sr and Nd isotope data for whole rocks, glasses and minerals are combined to reconstruct the nature and origin of mixing
end-members of the 200 km3 trachytic to phonolitic Campanian Ignimbrite (Campi Flegrei, Italy) magmatic system. The least-evolved magmatic end-member
shows equilibrium between host glass and the majority of the phenocrysts and is less radiogenic in Sr and Nd than the most-evolved
magma. On the contrary, only the Fe-rich pyroxene from the most-evolved erupted magma is in equilibrium with the matrix glass,
while all other minerals are in isotopic disequilibrium. These magmas mixed prior to and during the Campanian Ignimbrite eruption
and minerals were freely exchanged between the magma batches. Combining the results of the geochemical investigations on magma
end-members with geophysical and geological data, we develop the following scenario. In stage 1, a parental, less differentiated
magma rose into the middle crust, and evolved through combined crustal assimilation and crystal fractionation. In stage 2,
the differentiated magma rose to shallower depth, fed the pre-Campanian Ignimbrite activity and evolved by further open-system
processes into the most-evolved and most-radiogenic Campanian Ignimbrite end-member magma. In stage 3, new trachytic magma,
isotopically distinct from the pre-Campanian Ignimbrite magmas, rose from ca. 6 km to shallower depth, recharged the most-evolved
pre-Campanian Ignimbrite magma chamber, and formed the large and stratified Campanian Ignimbrite magmatic system. During the
course of the Campanian Ignimbrite eruption, the two layers were tapped separately and/or simultaneously, and gave rise to
the range of chemical and isotopic values displayed by the Campanian Ignimbrite pumices, glasses and minerals. 相似文献