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苏鲁高压—超高压变质带的折返构造及折返机制 总被引：85，自引：8，他引：77
苏鲁高压—超高压变质带的折返构造是由韧性剪切叠覆构造岩片组成,具NWW-SEE向剪切矢量及SEE向NWW的剪切指向,与折返构造伴随的高压和超高压退变质反应过程与石英从高温—中温—低温的组构模式吻合。150～100Ma期间的伸展事件包含了北界韧性伸展转换性剪切带及莱阳盆地的形成、苏鲁高压—超高压变质带北部花岗岩侵位、折返面理弯曲形成背形构造及伴随的韧—脆性正滑构造。多学科的综合研究表明,240～220Ma扬子板块巨量物质往北深俯冲于北中国板块之下,220～200Ma高压—超高压变质岩石整体快速折返,折返板片中保存的自上而下变质岩石单元序列与剪切叠覆构造岩片的物质组成序列基本一致。提出苏鲁高压—超高压变质折返板片呈上拱的舌形体,变形分解表明苏鲁高压—超高压变质板片是在“挤出”机制下折返及受后期伸展事件的改造。 相似文献
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本文依据浅变质岩层所保存的韵律层理、沉积构造、火山角砾一凝灰结构及残存的微古植物组合等,以及硅酸盐、稀土、微量元素分析成果的判别,对浅变质岩层进行了再认识,认定该浅变质岩是一套经受浅变质作用改造的火山碎屑沉积岩层;并就建立其地层序列,区域地层对比进行了论述;对其存在意义和时代归属进行了讨论. 相似文献
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大洋岩石圈俯冲增生过程中可能伴随着复杂的深部板片运动过程。高压变质岩无疑是记录这些深部过程的良好载体。最近的研究提出,在特定情况下,双向俯冲中占主导的俯冲板块拖曳另一侧板块发生反向运动,从而短板片可能被另一侧长板片拖出。该研究提示我们关注俯冲增生过程中这种可能的“不正常”的板片运动方式,从而客观而全面地剖析碰撞造山带。现有高压变质岩折返模式中,除了俯冲隧道流模式,其余模式均强调单次快速折返。然而,俯冲反向运动导致的折返过程有所不同:对单个高压变质岩来说仍是快速折返,但是对整体高压变质岩带来说,整个俯冲反向期间必然都存在高压变质岩折返,从而形成较长的折返过程持续时间。对上地壳层次的折返相关构造变形的研究有助于揭示上述过程。 相似文献
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宜丰—德兴一带存在新的一种造山带类型,称之为晋宁期—加里东期宜丰-德兴叠覆型造山带,总体呈半月形舌状展布,是经北南双向多期碰撞叠覆的隐伏-半隐伏型造山带。经对多个出露于造山带内的构造岩片进行时态、位态、相态的研究与恢复,建立了该造山带的结构样式和构造演化序列,具有3层结构模式。分别由代表中新元古代华南洋的残迹蛇绿混杂岩、扬子陆缘弧前盆地火山-沉积变质岩系、下南华统次深海相沉积的浅变质岩片与怀玉—广丰地区青白口纪晚期—早古生代沉积的下南华统浅变质岩片组成。造山带两侧的宜丰-景德镇与德兴-弋阳推覆带是中国重要的铜、金多金属矿集区,伏于变质岩之下的晚古生代煤系地层有巨大的找煤潜力。 相似文献
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本文依据浅变质岩层所保存的韵律层理，沉积构造，火山角砾－凝灰结构及残存的微古植物组合等，以及硅酸盐、稀土、微量元素分析成果的判别，对浅变质岩层进行了再认识，认定该浅变质岩是一套经受浅变质改造的火山碎屑沉积岩层；并就建立其地层序列，区域地层对比进行了论述；对其存在意义和时代归属进行了讨论。 相似文献
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怀安地区构造变形强烈,是研究华北克拉通形成和演化的重要窗口。通过对该区基底变质岩系构造形迹进行研究,结合区域地质资料及同位素年龄数据,将该区早前寒武纪构造变形序列划分为4期: 新太古代阜平晚期(D1),桑干岩群韧性变形,形成片麻理、无根褶皱和韧性剪切带; 新太古代五台晚期(D2),在新太古代TTG/花岗岩中形成区域性片麻理和条带状构造,并在桑干岩群中形成近EW向的复式背形和向形构造; 古元古代吕梁中期(D3),集宁岩群沙渠村岩组形成区域性片麻理,并形成与片麻理一致的NE向韧性剪切带,在新太古代地质体中叠加近SN向的开阔复式背形和向形构造; 古元古代吕梁晚期(D4),红旗营子岩群太平庄岩组形成片理和片麻理,尚义—平泉断裂形成。建立了该区早前寒武纪构造演化模式,并将其划分为新太古代陆壳增生阶段和古元古代碰撞造山阶段,对理解华北克拉通的形成及演化具有重要意义。 相似文献
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九岭岩体中片麻状岩石的成因初探 总被引：1，自引：0，他引：1
本文详细描述了九岭岩体中片麻状岩石的基本特征，并进行了成因探讨，认为九岭岩体中片麻状岩石是由新元古代侵位的深成侵入岩经在东期韧性剪切改造而形成的糜棱岩石系列的动力变质岩。 相似文献
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本文着重讨论华北地台太古代变质岩群的原岩及其火山喷发沉积建造的成岩特征和构造演化条件,以进一步探索太古界矿产资源的赋存规律,尽快获得实效. 太古界变质岩的原岩特征区内太古代变质岩群广布于辽、吉、京、冀、晋、鲁、豫、皖、内蒙、陕、宁等地.各地岩群因受变质、混合程度有差异,而形成了种类繁多的变质岩.其中有片岩、浅粒岩、变粒岩、斜长角闪岩、片 相似文献
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中天山变质岩系的成岩时代及演化探讨 总被引：8，自引：1，他引：8
中天山隆起带属天山地槽的一个组成部分,它西起中苏边界,经天山主峰呈狭长条带向东伸展.带内变质岩系广泛发育,它们主要由片麻状花岗质混合岩、石英岩、各种片岩和大理岩等中深变质岩组成.由于缺乏化石依根和在很多地方它们与古生代地层呈断裂接触关系,所以对其时代尚有争议.为搞清其成岩时代并了解该区地质演化历史,作者于1984年对中天山艾肯达坂附近的变质岩系进行了较系统地采样,分别作了铀—钍—铅法及铷—锶法同位素年龄测定,比较合理地确定了两次重要地质事件的发生时代—即变质岩原岩的形成时代和距今最近的一次强烈(热)变质作用的时代. 相似文献
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本文介绍了一个与花岗闪长质侵入体有关的金矿床勘查的经验地质模型。该模型是 Fairmile金矿公司在美国内华达州北部布法罗山谷(Buffalo Valley)地区进行金矿勘查过程中提出的 ,其建立模型的基础是区域地质调查资料和地表多元素地球化学资料及钻探资料。该模型在布法罗山谷金矿床勘查项目的几个靶区评价中得以成功应用 ,此外 ,也可作为其他地区类似矿床的勘查评价工具之一 ,特别是在覆盖区的靶区评价中尤为有用。 相似文献
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作为一种重要的土地流转模式,土地信托流转曾极大地提高了土地流转的效率,而时至今日其运作推广却陷入了困局。本文通过对绍兴土地信托流转的研究,分析了绍兴土地信托流转的运行机制和实施困境,同时在新的土地流转发展趋势下,为绍兴土地信托流转模式提出发展策略。 相似文献
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Since the West Pingdingshan Section in Chaohu was proposed as the candidate of the Global Stratotype Section and Point of the Induan-Olenekian boundary in 2003, the Lower Triassic of Chaohu has been extensively studied. Based on the studies on the Lower Triassic of Chaohu, (1) a continuous conodont zonation is established, which has become an important reference for Lower Triassic stratigraphic correlation over the world; (2) the First Appearance Datum of conodont Neospathodus waageni was suggested and has been basically accepted as the primary marker to define the Induan-Olenekian boundary; (3) a characteristic Lower Triassic excursion of carbon isotopes was brought to light and has been proven to be not only an excellent index for the stratigraphic correlation but also a unique indication for the perturbation of ecological environments in the aftermath of the end-Permian mass extinction; (4) a magnetostratigraphic sequence is constituted with a certain biostratigraphic control in the low-latitude region and it presents an important correlation to the Boreal sequence; (5) a cyclostratigraphic study provides an alternative method to constrain the age of the chronostratigraphic units; and (6) a scheme of the Olenekian subdivision is recently suggested to define the boundary between the Smithian and Spathian Substages. In addition, Chaohu is also the type locality of the Chaohuan Stage, the upper stage of the Lower Triassic in the China Chronostratigraphic System. Thus, the Lower Triassic of Chaohu is not only a classic sequence in South China, but also a key reference sequence to the investigation of the corresponding stratigraphy and geological events over the world. The recent achievements are viewed here for an overall understanding of the sequence. Then the current situation of the Induan-Olenekian and Smithian-Spathian boundaries is discussed to provide a reference for later works. 相似文献
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浙东南遂昌湖山萤石矿田成矿构造地球化学特征 总被引：1，自引：1，他引：0
本文以浙东南遂昌湖山萤石矿田为例,对此类浅成低温热液矿床成矿构造地球化学特征,进行了初步研究与探讨;进一步揭示了萤石矿成矿物质组分的分配、迁移、分散、富集特征与控矿构造之间的内在联系。 相似文献
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Rashed Abdullah Delwar Hossain M. Rafiqul Alam 《Journal of the Geological Society of India》2013,82(3):271-276
The Begumganj structure of the Hatia Trough in Bengal Basin has proved it’s hydrocarbon potentiality. Several seismic sections have been analyzed to construct different maps and to interpret subsurface geology, structure and stratigraphy. These maps reveal that the Begumganj structure is an elongated to oval shaped asymmetrical anticline having the general trend NNW-SSE. No major faults affecting the structure could have been identified. Most of the reflectors are strongly affected by channels, especially at the western flank. Based on the analysis of seismic and available well data, the only gas bearing strata at depth of 2995 m (or TWT 2.02 seconds) has been identified. The structure is interpreted as a strati-structure entrapment because shale fill channel truncated this layer on western flank and at the crestal part of the anticline. The structure probably formed after the deposition of sediments. The channel has formed after the corresponding unit cut has been deposited. The channels eroding the reservoir unit range from Late Miocene to Early Pliocene age where the anticline probably begun to form during the Pliocene. Strong increase in amplitude (bright spot), possibly associated with hydrocarbon, has been apparent on seismic lines BG 9 and BG 10. The stratigraphic succession based on the information of the wells drilled on this structure and it’s surrounding fields reveals that the lithological sequences range from Miocene to Recent age where the only proven gas producing sand zone is located in the Bhuban Formation. 相似文献
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Changes of the Hailuogou Glacier, Mt. Gongga,China, against the Background of Global Warming in the Last Several Decades 总被引：2，自引：0，他引：2
Great change, associated with global warming, has occurred at the Hailuogou (海螺沟)has retreated 1 822 m in the past 106 years, with an annual mean retreat of 17.2 m, and the front elevation has risen by 300 m since 1823. Comparison of glacier variations and temperature fluctuations in China and the Northern Hemisphere, over the last 100 years, indicates that glacier retreat stages occurred during the warm phase, and vice versa. Mass balance records during 1959/60--2003/04 have shown that the glacier has suffered a constant mass loss of snow and ice. The accumulated mass balance, -10.83 m water equivalent, indicates an annual mean value of -0.24 m water equivalent. The correlation between the mass balance and temperature is significant, which also indicates that climate warming is the crucial cause of glacier loss.Local hydrological and climatic data demonstrate that runoff from the glacier has been increasing both seasonally and annually.The correlation analysis and trend analysis indicate that ice and snow melted water is the main cause of an increase in the runoff. As the climate has become warmer, changes in the glacier surface morphology have obviously occurred. These include a decrease in glacier thickness, enlargement of glacial caves, and reduction of the size of clefts on the glacier surface. The ablation period has lengthened and the ablation area has expanded. A variety of factors thus provide evidence that the Hailuogou glacier has suffered a rapid loss of snow and ice as a result of climatic warming. 相似文献
18.
Frolova N. L. Kireeva M. B. Magrickiy D. V. Bologov M. B. Kopylov V. N. Hall J. Semenov V. A. Kosolapov A. E. Dorozhkin E. V. Korobkina E. A. Rets E. P. Akutina Y. Djamalov R. G. Efremova N. A. Sazonov A. A. Agafonova S. A. Belyakova P. A. 《Natural Hazards》2016,80(1):103-125
Hydrological extreme events pose an imminent risk to society and economics. In this paper, various aspects of hydrological hazards in Russia are analysed at different scales of risk assessment. It is shown that the number of hydrological and meteorological hazards in Russia has been growing every year. The frequency of economic losses associated with extreme low flow in this century has increased by factor five compared to the last decade of the previous century. With regard to floods, an interesting spatial patter can be observed. On the one hand, the number of floods in the Asian part of the country has increased, whereas on the other hand, the number and intensity of floods in estuarine areas in the European part of Russia have significantly reduced since the middle of the twentieth century, especially in the 2000s. This decrease can be attributed to runoff flooding in the mouths of regulated rivers, with an effective system of flood and ice jam protection. The analysis shows that there is an 8–12-year periodicity in the number of flood occurrences and that flood surges have intensified over the last 110 years, especially on the European territory of Russia. An integrated index that accounts for flood hazards and socio-economic vulnerability was calculated for each region of Russia. A classification of flood risk was also developed, taking into account more than 20 hydrological and social–economic characteristics. Based on these characteristics, hazard and vulnerability maps for entire Russia were generated which can be used for water management and the development of future water resources plans.
相似文献19.
Field and laboratory observations on an association of cobia,Rachycentron canadum with cownose ray,Rhinoptera bonasus are reported. Cobia main-tained a position in close proximity to the back of the rays. The cobia would move away from the rays to take food presented. This opportunistic and probably facultative feeding on rejected food scraps or displaced benthos may be the first step in the evolution of commensal attachment as has been shown for the remoras. 相似文献
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黄铁矿是闹枝金矿的主要载金矿物之一,不同成矿阶段的黄铁矿在晶体形态、化学成分以及热电性等方面各有其特点,特别是黄铁矿的热电性特征,在金矿的找矿勘探中具有重要的指导意义。 相似文献