鞍山陈台沟BIF铁矿与太古代地壳增生：锆石U-Pb年龄与Hf同位素约束   总被引：7，自引：4，他引：3  

代堰锫  张连昌  朱明田  王长乐  刘利 《岩石学报》2013,29(7):2537-2550

新发现的陈台沟隐伏铁矿床位于辽宁鞍山附近,矿石类型以条带状铁矿石为主,铁矿层顶板围岩为绿泥石英片岩,底板围岩为黑云石英片岩.元素地球化学分析表明,铁矿石及磁铁矿单矿物均富集重稀土,具La、Eu及Y正异常,无明显Ce负异常,反映成矿物质来源于海底高温热液(约占0.1％)与海水的混合溶液,且BIF沉积时海水处于缺氧环境.标型组分分析显示铁矿石及磁铁矿属于沉积变质型或BIF型.原岩恢复表明,绿泥石英片岩原岩为酸性火山岩,黑云石英片岩原岩为泥砂质岩石,二者皆富集Rb、Th、U、LREE,亏损Nb、Ta、Ti.构造背景分析表明两类片岩的原岩均形成于岛弧背景,反映了陈台沟BIF沉积时的构造环境.LA-ICP-MS锆石U-Pb定年显示铁矿体夹层绿泥石英片岩中岩浆锆石形成于2551±10Ma,代表陈台沟BIF形成时代;变质锆石形成于2469±23Ma,代表后期变质作用时代.Hf同位素分析显示大多数锆石具有正的εHf(t)值(-2.23 ～7.54),表明岩浆源区以亏损地幔物质为主,但明显受到古老地壳物质的混染;二阶段模式年龄(tDM2)主要介于3133～ 2580Ma之间.结合其他矿区Hf同位素资料,指示鞍本地区可能存在新太古代(～2.55Ga)地壳增生事件.综合分析认为,陈台沟铁矿属Algoma型BIF,是新太古代末华北克拉通大规模BIF成矿事件的代表之一.  相似文献   

柴达木盆地油砂山油田上干柴沟组高分辨率层序地层分析          下载免费PDF全文

周斌  汤军  廖春  周金应  桂碧雯  刘青文  林益康 《沉积与特提斯地质》2013,(3):27-33

运用Cross提出的高分辨率层序地层学理论,综合测井、岩心等资料,对油砂山油田上千柴沟组进行分析,将上干柴沟组地层划分为15～20个短期旋回、6个中期旋回和1个长期旋回。分析了各级次旋回内部沉积相特征及演化规律,建立了全区以中期基准面升、降半旋回相域为等时地层单元的高分辨率层序地层格架,以此为指导精细刻画了上干柴沟组地层的砂体展布情况,指出长期基准面上升早期和下降晚期及三角洲体系为砂体发育的最有利部位。  相似文献   

柔性工程理论在极地船舶航行风险防控中的应用          下载免费PDF全文

付姗姗 张笛桑凌志  严新平 《极地研究》2016,28(2):250-256

为预防和减少极地水域交通事故,提高船舶在极地水域通航风险防控能力,根据柔性工程理论的内涵特征和极地水域船舶通航风险,提出极地水域船舶航行风险防控柔性系统的体系构架。根据柔性系统构建的四要素(学习、预测、监测和应对)及其与环境之间的联系,从环境分析、脆性机理、风险预测、状态监测和危机应对等五个方面,讨论了极地水域船舶航行风险防控柔性系统构建所涉及的关键技术,为提升极地水域船舶航行风险防控能力和技术水平,建设安全、便捷、高效、经济、绿色的现代化海运体系,提供理论基础支持。  相似文献   

Different expressions of rifting on the South China Sea margins     

《Marine and Petroleum Geology》2014

Rifting of continental margins is generally diachronous along the zones where continents break due to various factors including the boundary conditions which trigger the extensional forces, but also the internal physical boundaries which are inherent to the composition and thus the geological history of the continental margin. Being opened quite recently in the Tertiary in a scissor-shape manner, the South China Sea (SCS) offers an image of the rifting structures which varies along strike the basin margins. The SCS has a long history of extension, which dates back from the Late Cretaceous, and allows us to observe an early stretching on the northern margin onshore and offshore South China, with large low angle faults which detach the Mesozoic sediments either over Triassic to Early Cretaceous granites, or along the short limbs of broad folds affecting Palaeozoic to Early Cretaceous series. These early faults create narrow troughs filled with coarse polygenic conglomerate grading upward to coarse sandstone. Because these low-angle faults reactivate older trends, they vary in geometry according to the direction of the folds or the granite boundaries. A later set of faults, characterized by generally E–W low and high angle normal faults was dominant during the Eocene. Associated half-graben basement deepened as the basins were filling with continental or very shallow marine sediments. This subsequent direction is well expressed both in the north and the SW of the South China Sea and often reactivated earlier detachments. At places, the intersection of these two fault sets resulting in extreme stretching with crustal boudinage and mantle exhumation such as in the Phu Khanh Basin East of the Vietnam fault. A third direction of faults, which rarely reactivates the detachments is NE–SW and well developed near the oceanic crust in the southern and southwestern part of the basin. This direction which intersects the previous ones was active although sea floor spreading was largely developed in the northern part, and ended by the Late Miocene after the onset of the regional Mid Miocene unconformity known as MMU and dated around 15.5 Ma. Latest Miocene is marked by a regional basement drop and localized normal faults on the shelf closer to the coast. The SE margin of the South China Sea does not show the extensional features as well as the Northern margin. Detachments are common in the Dangerous Grounds and Reed Bank area and may occasionally lead to mantle exhumation. The sedimentary environment on the extended crust remained shallow all along the rifting and a large part of the spreading until the Late Miocene, when it suddenly deepened. This period also corresponds to the cessation of the shortening of the NW Borneo wedge in Palawan, Sabah, and Sarawak. We correlate the variation of margin structure and composition of the margin; mainly the occurrence of granitic batholiths and Mesozoic broad folds, with the location of the detachments and major normal faults which condition the style of rifting, the crustal boudinage and therefore the crustal thickness.  相似文献   

Issues and challenges in spatio-temporal application of an ecosystem services framework to UK seas     

《Marine Policy》2014

The concepts of ecosystem services and human welfare provide strong integrative frameworks that can be used to inform marine policy and management decisions that support sustainable development. A theoretical framework has been developed and applied to create a model for UK seas to measure changes in final ecosystem services, in terms of human welfare. The model that has been developed is explicitly spatial and temporal to facilitate its use in supporting marine planning decisions. The development and application of this framework to UK seas necessarily requires many assumptions to be made. The paper describes the development and population of the framework and discusses the practical limitations and challenges in seeking to develop and apply such models. Significant differences in long-term values of different services were identified under the different scenarios. All scenarios highlight the projected decline in oil and gas revenues which provide particular intense values at sites of extraction. These values are partially replaced by revenues from offshore renewables in some of the scenarios. Values associated with carbon sequestration, maritime transport, tourism and pollution assimilation are also very significant but more spatially diffuse. The study has demonstrated that it is possible to develop spatio-temporal models to evaluate changes in final ecosystem service benefits using existing data, although the approach necessarily requires many assumptions to be made.  相似文献   

汶川县震后5年生态环境质量恢复评价   总被引：2，自引：0，他引：2  

杨斌  曹春香  田蓉  刘诚  田海静  刘迪  项海兵 《遥感学报》2014,18(4):946-957

对汶川县震后5年生态恢复状况进行评价,以多源遥感数据为主,其他调查统计数据为辅,构建了基于压力—状态—响应模型的生态环境质量评价指标体系,采用综合指数法对汶川县2007年、2008年和2013年生态环境质量进行评价,得到震前、震后以及5年后的生态环境质量评价分级图,并对震后5年汶川县生态恢复状况进行分析。结果表明,2007年汶川县有79.4%的区域生态环境质量良好,2008年5月12日地震对生态环境造成极大破坏,尤其是靠近震源地区,生态环境质量下降更为严重。通过震后5年恢复,到2013年汶川县生态环境质量恢复比较显著,有55.84%的区域环境质量有明显改善,特别是生态环境质量较差地区改善幅度较大,但仍未达到2007年区域生态环境质量水平。最后为今后该区域生态环境恢复重建提出相应的建议。  相似文献   

数字晋江地理空间框架数据建设及关键技术     

周友义 《现代测绘》2014,(1):61-64

本文介绍了数字晋江地理空间框架数据建设及关键技术,包括建设内容、主要建设内容的关键技术和流程方法,对于其他地方的数字城市地理空间框架的数据建设具有参考价值。  相似文献   

第一次世界大战初期德国东亚驻军跨岛链作战的军事地理分析     

杨霄 《地理学报》2023,78(1):230-240

就军事地理环境而言,当代中国在海洋方向面临的最主要威胁来自环中国岛链的封锁,研究这一限制性地理环境对准备和实施军事活动的影响与相应对策,具有重要的现实意义。第一次世界大战（简称“一战”）初期,德国东亚驻军进行了跨岛链作战的实践,但在日本海军依托岛链和优势兵力的封锁下,其战略目标未能达成,并且出现了军事地理位置上的优劣转换。本文通过对“一战”初期德国东亚驻军跨岛链作战行动的军事地理分析,尝试提出军事地理研究思路、跨学科融合路径和分析框架。本文分析认为,彼时德占青岛虽然具有良好的战略态势和强大的军事力量,但孤悬海外,且缺乏战略纵深;从宏观的区域尺度分析来看,基地与舰队间的联系被岛链分隔,腹背受敌,军事地理上的劣势凸显。但依托岛链进行封锁,需要集结大量兵力,利用对方边缘区内作战力量相对比较薄弱的有利条件,原本实力较弱的德国东亚舰队取得了重大战果,形成反转式的“核心—边缘”结构。本文为中国的海疆安全和海洋强国建设提出了5条建议。  相似文献   

在时空框架中理解中国大学人文地理教学特色及其成因——以1912—1949年中国主要大学地理系为例     

周尚意  江道敏 《地理研究》2023,42(2):580-596

采用历史唯物主义史观,建立一个时空框架,分析民国时期中国大学人文地理教学特色及其成因。本文主要关注1912—1949年间,国立北平（北京）师范大学、国立中央大学、国立清华大学、国立中山大学的地理系的人文地理学教学特色。研究史料来自大学的教学档案、人物回忆文章、政府文件、中国学者编撰和翻译的教材和教参,同时参考了相关研究文献。借助时空框架,基于史料对比,得出结论：(1)只有在历史的时间脉络下,才能理解民国时期军事地理、国防地理和政治地理课程设置的必然性;(2)只有在世界格局的空间框架下,才能理解民国时期的“国耻地理”教育内容,以及“中体西用”主张的失败;(3)只有将时空框架进一步细化,才能深入理解民国时期大学人文地理教学中不同教师的能动性,如学术思想、教学风格、政治主张、教材编写和选用等。综上所述,只有站在开放的时空框架中,才能更为清醒地定位当前中国大学人文地理学教学。  相似文献   

湖南省成矿地质事件纲要          下载免费PDF全文

柏道远  唐分配  李彬  曾广乾  李银敏  姜文 《中国地质》2022,49(1):151-180

[研究目的]湖南省矿产资源丰富,矿种及成因类型繁多,但对各类矿产形成的时代和构造背景尚缺乏系统归纳和总结.[研究方法]本文在既有区域矿产资料基础上,结合近些年区域构造演化、成岩成矿年龄、矿床成因机制等研究成果,对湖南省成矿地质事件及各期成矿事件的构造背景、矿床成因、矿产发育和分布特征等进行了系统探讨和总结.[研究结果]...  相似文献