共查询到19条相似文献，搜索用时 937 毫秒
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本文报道由蓝田、陕县、洛川、西峰、平凉、兰州及靖远等剖面获得的古地磁研究结果．主要结论为：１．中国黄土剖面记录了Ｂｒｕｎｈｅｓ正极性带与Ｍａｔｕｙａｍａ负极性带，Ｂｒｕｎｈｅｓ／Ｍａｔｕｙａｍａ极性转换过程位于第８层黄土（Ｌ８）．在段家坡黄土剖面该转换过程对应的地层厚度为０．３７５ｍ，持续时间约６０００ａ．转换过程由３次极性变化构成，每次经历的时间约为４００ａ．２．Ｊａｒａｍｉｌｌｏ正极性亚带（Ｊ）位于标志层Ｌ９至Ｌ１５之间，大约Ｓ１０－Ｓ１３位置．３．Ｏｌｄｕｖａｉ正极性亚带（Ｏ）对应的地层为Ｓ２７－Ｓ３３４．Ｒｅｕｎｉｏｎ正极性亚带（Ｒ）由两部分组成，在蓝田段家坡黄土剖面分别位于Ｌ３６和Ｓ３８５．Ｍａｔｕｙａｍａ负极性带与Ｇａｕｓｓ正极性带界限（Ｍ／Ｇａ）位于黄土和红色粘土交界处，中国黄土的底界年龄为２．４８Ｍａ左右．黄土与红色粘土为整合接触关系．６．黄土下伏的红色粘土记录了Ｇａｕｓｓ正极性带，Ｇｉｌｂｅｒｔ负极性带和古地磁年表编号５（Ｅｐｏｃｈ５）． 相似文献
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调谐质量阻尼器系统控制结构地震反应的若干问题 总被引：18，自引：3，他引：18
本文研究调谐质量阻尼器（ＴｕｎｅｄＭａｓｓＤａｍｐｅｒ，以下简称ＴＭＤ）用作抗震结构的防御体系时的一些问题，包括ＴＭＤ在结构上的最佳位置，ＴＭＤ频率的最佳值，ＴＭＤ对非调谐结构振型的影响和ＴＭＤ参数的灵敏度分析，这些问题的解决将为研究设置ＴＭＤ的结构的抗震设计方法提供理论依据。 相似文献
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Ｔｈｅｆａｕｌｔｐｌａｎｅｏｆｔｈｅ１９９１，Ｄａｔｏｎｇ－Ｙａｎｇ－ｇａｏ，Ｓｈａｎｘｉ，Ｃｈｉｎａ，Ｍｓ＝５．８ｅａｒｔｈｑｕａｋｅＭｉｎｇＷＡＮＧ（王鸣），Ｌｉａｎ－ＱｉａｎｇＺＨＡＮＧ（张廉强）ａｎｄＰｅｉ－ＤｅＷＡＮＧ（王培德）（Ｉｎｓｔｉ... 相似文献
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《地震学报(英文版)》1995,(1)
Ｇｕｏ－ＭｉｎＺＨＡＮＧ（张国民）ＧｏｔＢａｃｈｅｌｏｒａｎｄＭａｓｔｅｒＤｅｇｒｅｅｓｉｎＧｅｏｐｈｙｓｉｃａｌＤｅｐａｒｔｍｅｎｔ，ｔｈｅＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙＵｎｉｖｅｒｓｉｔｙ．ｏｆＣｈｉｎａｉｎ１９６５ａｎｄ１９６８ｒｅｓ... 相似文献
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李应平 《地震学报(英文版)》1996,9(3):377-387
Ｍｉｃｒｏｅａｒｔｈｑｕａｋｅａｎａｌｙｓｉｓｆｏｒｈｙｄｒａｕｌｉｃｆｒａｃ┐ｔｕｒｉｎｇｐｒｏｃｅｓＹＩＮＧ－ＰＩＮＧＬＩ（李应平）ＤｅｐａｒｔｍｅｎｔｏｆＥａｒｔｈ，ＡｔｍｏｓｐｈｅｒｉｃａｎｄＰｌａｎｅｔａｒｙＳｃｉｅｎｃｅｓ，Ｍａｓａｃｈ... 相似文献
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~(40)Ar/~(39)Ar dating of shear deformation of the Xianshuihe fault zone in west Sichuan and its tectonic significance 总被引：6，自引：1，他引：6
ZHANG Yueqiao CHEN Wen & YANG Nong . Institute of Geomechanics Chinese Academy of Geological Sciences Beijing China . Institute of Geology Chinese Academy of Geological Sciences Beijing China . Institute of Geology Geophysics Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2004,47(9)
TheNW-SEstrikingXianshuihefaultzoneslicesthesoutheasternTibetanPlateauandconnectssoutheastwardwiththeAnninghe-Zemuhe-Xiaojiangfaultzone,whichformahuge,activesinistralstrike-slipfaultzone(fig.1).ThisfaultzoneisanimportantseismicfaultineastTibet[1-5].EarthquakegeologystudiesandoffsetpatternsofyounggeologicalfeatureshaveshownthatlateQuaternarysinistralsliprateoftheXianshuihefaultzonereaches13mm/a[1,2].TheXianshuhefaultzoneconsistsoftwomainbranches,theDaofufaultbranchinthewestandtheXianshuih… 相似文献
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For lack of reliable isotopic chronological data, the metamorphic rock series in the Faku region of northern Liaoning has
long been regarded as the platform basement. Recent studies reveal that these deformed and metamorphosed rocks, with a variety
of protoliths of plutonic intrusions and supracrustal volcanic and sedimentary rocks, were genetically related to later ductile
shearing events, and they, together with the syntectonic intrusions, constituted the large-scale Faku tectonites. In this
paper, we report new 40Ar/39Ar data on hornblende, biotite, and K-feldspar from typical granitic mylonites in this suite of tectonites. The plateau age
256 Ma of FK53 hornblende and the high-temperature plateau age 262 Ma of Fk51-1 biotite should represent the cooling ages
when the granites, formed as a result of Paleozoic oceanic crustal subduction beneath the continental crust or collision of
multiple micro-continental blocks, were exhumed into shallow crustal levels. The plateau age 231 Ma of FK51-1 boitite and
the apparent age 227 Ma of Fk51-2 K-feldspar are interpreted to record the time of ductile deformation occurring under greenschist
facies conditions, i.e. the formation age of the Faku tectonites, while the age gradient from 197 Ma to 220 Ma of Fk51-2 K-feldspar
probably record the subsequent stable uplift-cooling process. The tectonic exhumation event indicated by the plateau age 180
Ma of Fk51-2 K-feldspar may be associated with the onset of paleo-Pacific subduction beneath the North China plate. In addition,
the U-Pb dating of FK54 zircon from later-intruded granite yields the age of crystallization of this super-unit intrusion
at 159 Ma, thus establishing an upper limit for the formation age of the Faku tectonites, while the plateau age 125 Ma of
Fk54 K-feldspar most likely corresponds to the rapid cooling and tectonic denudation event associated with the final collision
between the Siberian plate and the North China plate. These isotopic ages provide important geochronological constraints for
re-evaluating the tectonic essence of the Faku Faulted Convex and ascertaining the suturing boundary between the North China
Platform and the Xingmeng Fold System. 相似文献
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ZHANG Xiaohui WANG Hui & LI Tiesheng Key Laboratory of Lithosphere Tectonic Evolution Institute of Geology Geophysics Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(5)
As for the metamorphic rock series distributed on the “Faku Faulted Convex (FFC)”[1] of the northern Liaoning, the earliest geologic investigation divided it into the Langzishan, Dashiqiao and Gaixian forma-tions1) and considered it to be equivalent to the Liaohe Group in the eastern Liaoning, whereas Liaoning Bu-reau of Geology and Mineral Resources (LBGMR) included it into the Lower Proterozoic basement[1]. Recent 1︰50000 scale geological mapping2) reveals that this deformed and … 相似文献
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New40Ar/39Ar plateau ages from rocks of Changle-Nanao ductile shear zone are 107.9 Ma(Mus), 108.2 Ma(Bi), 107.1 Ma(Bi), 109.2 Ma(Hb)
and 117.9 Ma(Bi) respectively, which are concordant with their isochron ages and record the formation age of the ductile shear
zone. The similarity and apparent overlap of the cooling ages with respective closure temperatures of 5 minerals document
initial rapid uplift during 107–118 Ma following the collision between the Min-Tai microcontinent and the Min-Zhe Mesozoic
volcanic arc. The40Ar/39 Ar plateau ages, K-Ar date of K-feldspar and other geochronologic information suggest that the exhumation rate of the ductile
shear zone is about 0.18–1.12 mm/a in the range of 107–70 Ma, which is mainly influenced by tectonic extension. 相似文献
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对鄂尔多斯盆地磷灰石裂变径迹资料深入分析表明．最迟２３Ｍａ以来盆地发生了一期由于快速抬升剥蚀引起的冷却事件．盆地东部以９５ｍ／Ｍａ的速率抬升，造成约２０００ｍ的剥蚀量；而盆地西部则以５６ｍ／Ｍａ的速率抬升，导致了约１０００ｍ的剥蚀量．盆地东、西部的差异抬升剥蚀导致了盆地现今微微西倾的构造面貌．这一抬升剥蚀事件是印度板块与欧亚板块碰撞引起亚洲构造运动形式以挤压为主，转换为中新世以来以地壳增厚为主的结果．Ｋ－Ａｒ年龄和镜质体反射率资料分析表明，盆地在１７０－１６０Ｍａ（中侏罗末）曾发生一期热事件，使古地温梯度达５７℃／ｋｍ，古热流值达９６－１０９ｍｗ／ｍ２． 相似文献
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40Ar/39Ar age spectrum analyses of samples from Broken Hill, New South Wales, indicate that the region has experienced a complex thermal history following high-grade metamorphism, 1660 Ma ago. The terrain cooled slowly (～3°C Ma?1) until about 1570 Ma ago, when the temperature fell below about 500°C. Following granitoid emplacement ～1500 Ma ago, the region remained relatively cold until affected by a thermal pulse 520±40Ma ago, causing temperatures to rise to～350°C in some places. During this event, accumulated40Ar was released from minerals causing a significant Ar partial pressure to develop. Laboratory Ar solubility data combined with the40Ar/39Ar age spectra gives a local estimate of this partial pressure of ～10?4atm. The region finally cooled below 100°C about 280 Ma ago.40Ar/39Ar age spectrum analyses of hornblende, plagioclase and clinopyroxene containing excess40Ar are characterized by saddle-shaped age spectra. Detailed analysis of plagioclase samples reveals a complex diffusion behaviour, which is controlled by exsolution structures. This effect, in conjunction with the presumed different lattice occupancy of excess40Ar with respect to radiogenic40Ar, appears to be responsible for the saddle-shaped age spectra. 相似文献
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Detrital microcline grains from sedimentary strata preserve a record of thermal evolution in the temperature range ～ 100° to 200°C which can be revealed by40Ar/39Ar age spectrum analysis. Microcline separates from deep drill hole intersections with Eocene to Miocene sediments in the Basin and Tejon Blocks of the southern San Joaquin Valley, California, analysed by the age spectrum approach show radiogenic40Ar (40Ar*) gradients that record both the slow cooling of the uplifting sediment source ～ 65 Ma ago, and a recent thermal event. This information, in conjunction with the observation of fission track annealing in the coexisting apatites, allows estimation of the temperature-time conditions of this thermal event at about 140°C for ～ 200 ka. Present and paleotemperature data is in accord with heating related to several kilometers of Pleistocene sediment deposition. Heat flow calculations suggest that this recent subsidence has depressed the thermal gradient from about 30°C km?1 to the present apparent gradient of 24°C km?1.40Ar/39Ar analysis of detrital microcline crystals yields thermochronological information in the temperature-time range of petroleum maturation and provides this technique with potential as both a useful exploration tool and as a means of probing the fundamental geodynamic processes of basin evolution. 相似文献
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Barbara E John David A Foster Michael J Cheadle C.Mark Fanning 《Earth and Planetary Science Letters》2004,222(1):145-160
The cooling history and therefore thermal structure of oceanic lithosphere in slow-spreading environments is, to date, poorly constrained. Application of thermochronometric techniques to rocks from the very slow spreading SW Indian Ridge provide for the first time a direct measure of the age and thermal history of in situ lower oceanic crust. Crystallization of felsic veins (∼850°C) drilled in Hole 735B is estimated at 11.93±0.14 Ma, based on U-Pb analyses of zircon by ion probe. This crystallization age is older than the ‘crustal age’ from remanence inferred from both sea surface and near-bottom magnetic anomaly data gathered over Hole 735B which indicate magnetization between major normal polarity chrons C5n.2n and C5An.1n (10.949-11.935 Ma). 40Ar/39Ar analyses of biotite give plateau ages between 11 and 12 Ma (mean 11.42±0.21 Ma), implying cooling rates of >800°C/m.y. over the first 500,00 years to temperatures below ∼330-400°C. Fission-track ages on zircon (mean 9.35±1.2 Ma) and apatite reveal less rapid cooling to <110°C by ∼7 Ma, some 4-5 m.y. off axis.Comprehensive thermochronometric data from the structurally intact block of gabbro between ∼700 and 1100 m below sea floor suggest that crust traversed by ODP Hole 735B mimics conductive cooling over the temperature range ∼900-330°C, characteristic of a 2-D plate-cooling model for oceanic lithosphere. In contrast, lower temperature chronometers (fission track on zircon, titanite, and apatite; T≤280°C) are not consistent with these predictions and record anomalously high temperatures for crust >700 m below sea floor at 8-10 Ma (i.e. 2-4 m.y. off axis). We offer two hypotheses for this thermal anomaly:
- (i)
- Off-axis (or asymmetric) magmatism that caused anomalous reheating of the crust preserved in Hole 735B. This postulated magmatic event might be a consequence of the transtension, which affected the Atlantis II transform from ∼19.5 to 7.5 Ma.
- (ii)
- Late detachment faulting, which led to significant crustal denudation (2.5-3 km removed), further from the ridge axis than conventionally thought.
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The Hougou gold deposit in northwestern Hebei is a typical K-metasomatism-related gold deposit hosted by K-altered rocks overprinting
alkali intrusive rocks. In order to determine the age and pulse intervals of K-metasomatism in this gold deposit, some metasomatic
K-feldspars from K-altered rocks are selected to measure their formation time by laser probe 40Ar-39Ar dating method. The new analyzing data show that these metasomatic K-feldspar formed during 202.6 Ma and 176.7 Ma, and the
corresponding K-metasomatism and associated gold mineralization occurred in the early stage of Mesozoic era. The pulse intervals
of K-metasomatism in the Hougou area are estimated to be about 4 Ma. 相似文献