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"双沟蛇绿岩"是笔者最早研究的蛇绿岩之一,位于云南哀牢山带。双沟出露的岩石有二辉橄榄岩、辉长岩、辉绿岩、斜长花岗岩、玄武岩、硅质岩等。辉长岩亏损LREE,锆石U-Pb年龄为362~328Ma。玄武岩具N-MORB和E-MORB的特征,锆石U-Pb年龄为249Ma。研究认为,"双沟蛇绿岩"可能产于陆间小洋盆或裂谷或裂陷槽背景。但是,双沟没有可信的深海沉积和混杂堆积的记录,虽然岩石组合类似蛇绿岩,地球化学也具有MORB的特征,暗示双沟可能不是一个典型的蛇绿岩。如果双沟不是蛇绿岩,则晚古生代的哀牢山带就不存在一个有一定规模的洋盆,也不可能存在大陆碰撞的记录。双沟不是蛇绿岩是什么?可能是造山橄榄岩(Orogenic peridotite)。造山橄榄岩与蛇绿岩的岩石组合类似,蛇绿岩的橄榄岩产于洋壳之下;造山橄榄岩产于陆壳之下。检讨双沟蛇绿岩的研究,反思蛇绿岩的概念。笔者认为,斯泰因曼的"三位一体"概念是合适的,1972年彭罗斯会议的决议是正确的,1996年怀柔会议构造学家对蛇绿岩概念的理解是对的。考虑到混杂堆积对于蛇绿岩的重要性,建议将混杂堆积也作为与蛇绿岩相伴的一个重要指标加进来。如果这个想法合适,则一个完整的蛇绿岩组合将由三个要素组成:1)岩浆岩(包括地幔岩、堆晶岩、侵入岩和火山岩,代表大洋岩石圈的物质组成); 2)深海沉积(代表洋盆顶部的物质组成); 3)混杂堆积(代表洋盆消失、陆块碰撞的构造产物)。蛇绿岩不同于其他岩浆岩,其研究需要特殊的方法和思路,明白这一点,蛇绿岩研究才能走上正轨。双沟蛇绿岩研究遇到危机,中国其他一些蛇绿岩也可能需要重新审视。因此,检讨双沟蛇绿岩,对反思蛇绿岩的研究具有一定的意义。 相似文献
124.
黄蜡玉的主要组分为石英,材料特性完全符合玉石的三大标准;美观、耐久、稀少,是品质很好的一种云南玉石新品,与翡翠、软玉相比有相似性或一致性。与我国其他地区所产石英质的京白玉、东陵玉、密玉、贵翠等相比,质地更细腻绵润,颜色更柔和,光泽更亮丽。龙陵黄蜡玉有独特的工艺经济价值,以及很高的科研价值。 相似文献
125.
碳中和已成为引领中国中长期可持续发展的纲领性目标.通过对已有研究成果的梳理与评述,从目标内涵和实现路径两个方面探讨了"碳中和是一场广泛而深刻的经济社会系统性变革"这一重要命题.中国碳中和目标与全球温控2℃/1.5℃目标内涵一致,需要以阶段性减排成效为基础制定中期行动方案来逐步实现长期减排目标.作为实现碳中和目标的两个主... 相似文献
126.
Support vector machines in remote sensing: A review 总被引:19,自引:0,他引:19
Giorgos Mountrakis Jungho Im Caesar Ogole 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(3):247-259
A wide range of methods for analysis of airborne- and satellite-derived imagery continues to be proposed and assessed. In this paper, we review remote sensing implementations of support vector machines (SVMs), a promising machine learning methodology. This review is timely due to the exponentially increasing number of works published in recent years. SVMs are particularly appealing in the remote sensing field due to their ability to generalize well even with limited training samples, a common limitation for remote sensing applications. However, they also suffer from parameter assignment issues that can significantly affect obtained results. A summary of empirical results is provided for various applications of over one hundred published works (as of April, 2010). It is our hope that this survey will provide guidelines for future applications of SVMs and possible areas of algorithm enhancement. 相似文献
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Neil Ellis 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(3):353-362
Geoconservation – protecting, managing and enhancing natural geological features and materials, and geomorphological landforms and processes – is especially important in Great Britain, a place sometimes described as the ‘cradle’ of the science of geology. For such a small area of land, Britain has an unusually diverse geological make-up, with rocks from every geological period present. Many stratigraphical terms used internationally were devised here, and British sites provide key study areas where important new geological theories were developed in the pioneering era of the Earth sciences. Therefore, with such a wealth of geology, and Britain's seminal place in the science itself, it is particularly important to conserve and protect key localities here for future generations. A first step in that process is the auditing of the geology and geomorphology of Britain, by carrying out a scientific evaluation exercise according to standard criteria, and creating an inventory of the most important sites for science.In the mid-1970s, the Nature Conservancy Council (NCC) began an ambitious programme for assessment and documentation of the most important sites for the scientific study of geology and geomorphology in Great Britain, building on previous statutory site conservation activity that had already been started in 1949 by the former Nature Conservancy. As a result, the ‘Geological Conservation Review’ (GCR) was formally launched in 1977. The GCR was a world-first project of its type in the systematic assessment of the whole geological heritage of a country, from first principles. Widespread consultation with geologists and geomorphologists across Great Britain was co-ordinated; their guidance and involvement was a key component of the site selection process. Almost 3000 nationally or internationally important sites had been selected for around 100 site-selection categories for the GCR register by 1990. Almost all the GCR sites are now conserved under British law as Sites of Special Scientific Interest (SSSIs), the GCR information providing the scientific evidence-base that underpins that designation.As part of the site-selection process – which is still active – a considerable archive of information about geological sites was amassed. A major publication exercise detailing all the GCR sites in what was to become the GCR Series of books was devised early on in the GCR programme.Thirty-six volumes of the GCR Series have been seen to completion by NCC and the Joint Nature Conservation Committee, and many GCR site reports have been many made freely available on the World Wide Web. As a new venture, the remaining nine volumes will now be published by Elsevier Science Publishers as Special Issues of the Proceedings of the Geologists’ Association. Each GCR volume includes an overview of the subject and outlines the history of study of the relevant branch of the Earth sciences, but most importantly contains detailed accounts of the features of geological importance in the sites described. A scientific interpretation is provided for each site account, which includes supportive illustrations, tables and photographs and an extensive reference list.The GCR rationale, methods and information resource have been invaluable in almost every aspect of geoconservation carried out in Britain, including World Heritage Site nominations, protection of stratotypes, justifying the scientific conservation value of sites at Public Inquiries, in stimulating geological research and in providing a readily available information resource for local, regional, national and international geoconservation activities. 相似文献
128.
CBM and CO2-ECBM related sorption processes in coal: A review 总被引:1,自引:0,他引:1
This article reviews the state of research on sorption of gases (CO2, CH4) and water on coal for primary recovery of coalbed methane (CBM), secondary recovery by an enhancement with carbon dioxide injection (CO2-ECBM), and for permanent storage of CO2 in coal seams.Especially in the last decade a large amount of data has been published characterizing coals from various coal basins world-wide for their gas sorption capacity. This research was either related to commercial CBM production or to the usage of coal seams as a permanent sink for anthropogenic CO2 emissions. Presently, producing methane from coal beds is an attractive option and operations are under way or planned in many coal basins around the globe. Gas-in-place determinations using canister desorption tests and CH4 isotherms are performed routinely and have provided large datasets for correlating gas transport and sorption properties with coal characteristic parameters.Publicly funded research projects have produced large datasets on the interaction of CO2 with coals. The determination of sorption isotherms, sorption capacities and rates has meanwhile become a standard approach.In this study we discuss and compare the manometric, volumetric and gravimetric methods for recording sorption isotherms and provide an uncertainty analysis. Using published datasets and theoretical considerations, water sorption is discussed in detail as an important mechanisms controlling gas sorption on coal. Most sorption isotherms are still recorded for dry coals, which usually do not represent in-seam conditions, and water present in the coal has a significant control on CBM gas contents and CO2 storage potential. This section is followed by considerations of the interdependence of sorption capacity and coal properties like coal rank, maceral composition or ash content. For assessment of the most suitable coal rank for CO2 storage data on the CO2/CH4 sorption ratio data have been collected and compared with coal rank.Finally, we discuss sorption rates and gas diffusion in the coal matrix as well as the different unipore or bidisperse models used for describing these processes.This review does not include information on low-pressure sorption measurements (BET approach) to characterize pore sizes or pore volume since this would be a review of its own. We also do not consider sorption of gas mixtures since the data base is still limited and measurement techniques are associated with large uncertainties. 相似文献
129.
从20世纪50年代末以来,江苏的环境地质工作经历了寻找地下水资源及区域性基础水文地质、工程地质勘察,城市水文地质、 工程地质、环境地质勘察,全省市、县地下水资源评价,环境地质及地质灾害防治研究,走向市场直接为国民经济建设服务等发展阶段.它在国民经济建设中发挥了极其重要的作用,并在各方面取得了很大发展. 相似文献
130.