共查询到20条相似文献，搜索用时 156 毫秒
1.
裂变径迹研究三峡九湾溪断裂带断裂时期 总被引：3，自引：2，他引：1
九湾溪断裂带位于三峡工程大坝西南 １８ ｋｍ处。利用从断裂带中的断层泥、断裂壁岩和断裂围岩内选出的 磷灰石,进行裂变径迹断代学研究,并对径迹长度的频率分布进行统计测量。研究证实：九湾溪断裂带发生断裂时期 为距今（０． ３３ ± ０． ０４） Ｍａ,与它周边围岩形成时代（２５． ７４±１． ９） Ｍａ截然不同。通过各种绝对年龄结果的对比分析, 均未见到全新世以来有明显的活动迹象,由此确认九湾溪断裂活动性对三峡枢纽工程并不构成威胁。 相似文献
2.
三峡库首区仙女山等断裂活动性同位素测年研究 总被引：1，自引：0，他引：1
在仙女山、九湾溪两断层形变监测洞室中,通过对断裂带进行地质编录和对构造岩进行微观分析,挑选出断层泥与方解石两类样品进行热释光(TL)测年。同时对洞外披覆跨仙女山断层上的第四纪河流冲积物、断层一侧周坪河谷底上第四纪湖相纹泥夹碳化木及披覆跨九湾溪断层上的第四纪崩滑堆积体中滑带土进行测年。综合分析表明,仙女山断层与九湾溪断层新活动年龄与三峡地区区域断层基本一致,为距今22～23万年左右。最新活动年龄仙女山断层为16～19万年、九湾溪断层为14万年左右。最新活动年龄的下限值仙女山断层为14～16万年、九湾溪断层为13万年左右。晚更新世以来,两断层均没有活动迹象。九湾溪断层上的滑坡为外动力作用所致,并非该断层活动作用的结果。 相似文献
3.
活断层中断层泥分形与断裂活动关系 总被引：7，自引：1，他引：6
以长江三峡仙女山、九湾溪和天阳坪３条断裂为例,对断裂活动性与断层泥分维值（Ｄ）进行对比研究发现,Ｄ值受断裂活动性与断层泥粒度双因素制约。同一断裂带中细粒断层泥Ｄ值低且粒断层泥Ｄ值;不断断裂之间相对活动断裂Ｄ值低于弱活动断裂Ｄ值。在改进断层泥分形计算方法的基础上,通过变换得到了具有物理意义的判断断裂活动性的单因素参量（ｒＬ）。该方法克服了用断层泥分维值判断断裂活动性时粒径影响Ｄ值的困难,为利用分形理 相似文献
4.
在地震地质背景研究的基础上,运用神经网络理论中改进的BP算法对三峡水库诱发地震强度进行了预测研究。预测结果表明,秭归盆地高桥断裂近库段有可能诱发Ms>6.0级的地震,可能诱发4.5相似文献
5.
关于第四纪早期构造事件的年代学研究取得了大量数据,但对构造事件的表现形式缺乏认识。文章通过对海原断裂带内拉分盆地演化趋势及年代学研究,认为海原断裂带内的最新拉分盆地形成于1.6MaB.P.之后,代表一次新断裂的形成时期,且新断裂走向与先存断裂有一定的逆时针夹角。通过对青藏高原中部可可西里-东昆仑断裂带构造地貌的遥感解译和强震破裂调查,认为可可西里-东昆仑断裂带是一条具有新生性的强震构造带,新断裂形成时期为1.10~0.65MaB.P.之间,其构造带内的新生性断裂走向与先存断裂亦有一定的逆时针方向夹角。两条断裂带具有一致的演化趋势,说明在早更新世中后期存在区域性的构造事件,该事件表现为一系列新生性断裂的产生。 相似文献
6.
三峡库区蓄水以来,长江周边出现了大量的水库地震,主要集中于巴东—泄滩—仙女山区域,目前已达上万次,最大震级为5.1级。通过野外地质调查及对已有水库地震数据进行研究,采用构造地质分析方法,对三峡库区仙女山和九畹溪断裂带水库地震空间上的迁移规律、时间上的周期规律以及微地震群的成因机理进行分析。结果表明：从时间上看,水库地震具有周期性,表现为长周期（与库水位相关）和短周期（与库水位快速波动相关）;从空间上看,水库地震具有迁移规律,受九畹溪断裂控制的触发型水库地震存在着逐渐向南迁移的特征,受仙女山断裂控制的触发型水库地震局限分布于仙女山断裂北延端点处,分布于仙女山断裂西侧（周坪乡附近）带状分布的水库诱发地震逐渐呈点状向南迁移。 相似文献
7.
大型水利水电工程水库诱发地震历来受业主、工程技术人员的重视。三峡工程蓄水10多年来,在蓄水过程中,三峡库区较蓄水前地震明显增多。本文选择了三峡库区既有活动断裂,又有可溶岩和煤层分布的近坝库段作为研究对象,通过对库区地震活动与水位的关系和诱发地震空间展布特征分析,认为:三峡水库诱发地震,发生在有可溶岩和含煤地层部位的塌陷型地震占总数的90%,而非可溶岩和不含煤地层中只占总数的10%;近坝库段地震主要发生在仙女山断层北端,且有地震呈丛集活动的特征;九湾溪断层上盘远离长江部位地震零星分布,距长江较近地段地震相对增多,下盘地震极少。地震与水位的对应关系十分密切,三峡水位上升,长江两岸发生的小地震较多,当水位蓄至175m时,地震主要发生在仙女山断裂的北端和九湾溪断裂的上盘及北端。 相似文献
8.
在分析研究前人资料的基础上,结合野外实际工作和室内研究,从三峡九湾溪断裂带内各段断层泥的特征研究分析出发,探讨了九湾溪断裂带的分段性,结果发现:九湾溪断裂带存在明显的分段性,中段和南段地震活动频度和强度大,应变强度高,断层活动以粘滑为主,其分维值在2.2～2.6之间,石英碎砾表面发育各种撞击揳入现象、线状擦痕等显微构造;北段地震活动频度和强度较小,应变强度弱,断层活动以稳滑为主,兼具粘滑,其分维值在2.4～2.8之间,石英颗粒多为磨圆球砾,其刻蚀形貌以裂而不破现象为代表;中段是九湾溪断裂带最有可能发生诱发地震的地段和我们的重点监测地段。 相似文献
9.
10.
用磷灰石的裂变径年龄及径变宅度变化规律,证实仙女山断裂带发生断裂的时期为距今０．７Ｍａ在若;从讨论的各种绝对年龄结果分析,均未见到全新世以来有明显的活动迹象,以此确定仙女山断裂的活动性对三峡枢纽工程并不构成威胁。 相似文献
11.
阿尔泰造山带富蕴基性麻粒岩折返过程:来自裂变径迹热年代学的限定 总被引：1，自引：1，他引：0
论文在阿尔泰造山带富蕴县乌恰沟基性麻粒岩的锆石SHRIMP年代学、地球化学、变质温压条件和形成的大地构造背景研究基础上,利用麻粒岩、围岩片麻岩和侵入到麻粒岩的辉绿岩岩墙的裂变径迹热年代学探讨了麻粒岩从深部折返至地表的过程。裂变径迹年代学研究发现基性麻粒岩的锆石裂变径迹年龄为三叠纪,而麻粒岩、围岩片麻岩和侵入到麻粒岩的辉绿岩岩墙的磷灰石裂变径迹年龄均显示为晚白垩世至新生代早期。对磷灰石裂变径迹测试所得到的径迹长度和单颗粒年龄数据进行热史模拟表明,三叠纪时,基性麻粒岩抬升至约地表以下7.8km的上地壳,温度冷却至锆石裂变径迹的封闭温度;晚白垩世至新生代早期(约100～50Ma),麻粒岩、围岩片麻岩和辉绿岩抬升至约地表以下3.5km,温度冷却至磷灰石裂变径迹的封闭温度;约50～15Ma,三者滞留在约地表以下1.7km的磷灰石部分退火带;约15Ma以来,喜马拉雅运动使得它们被抬升剥蚀至地表。 相似文献
12.
《International Geology Review》2012,54(12):1088-1117
Upper-crustal elements of the ～35 km thick crust of the southern portion of the Lachlan Orogen consist of a chevron-folded and faulted turbidite package (15 to 17 km structural thickness) overlying imbricated Cambrian metabasites and cherts (～5 km structural thickness). These are intruded by both Early and Late Devonian granites and are overlain by Upper Silurian (?) marine to continental clastics (Grampians Group) in the west, and Upper Devonian-Early Carboniferous silicic volcanics and continental redbed elastics in the east. The turbidites show a general younging to the east, as well as eastward vergence apart from a local reversal (Tabberabbera zone). The region has been relatively stable since the mid-Paleozoic with apatite fission-track data recording cooling below ～100°C at 340-330 Ma in the west and 300 to 280 Ma in the east. Younger fission-track ages to the south, approaching the present coastline, reflect denudation during the opening of Bass Strait and the formation of the Cretaceous Otway and Gippsland basins. The major crustal discontinuities, the Woorndoo-Moyston and Mount Wellington fault zones, show significant Mesozoic reactivation and juxtapose regions of younger against older apatite fission-track ages. The nature of the lower crust remains unclear, but there is increasing evidence that it is not underlain by thinned Proterozoic continental crust. The Lachlan Orogen is an example of mid-Paleozoic tectonic accretion in a Southwest Pacific-style oceanic setting. Subduction-related oceanic thrusting produced the deformed and imbricated turbidite packages, and subduction-related magmatic underplating (perhaps during “rollback”) produced the large volumes of granite and volcanic rocks, and the localized high-T/low-P metamorphism. 相似文献
13.
通过对西昆仑北部山前的碎屑锆石裂变径迹年代学分析,将年龄划分为8个峰值区间:P1—4.7Ma以来;P2—13～9Ma;P3—24～18Ma;P4—47～33Ma;P5—79～57Ma;P6—131～103Ma;P7—185～180Ma;P8—267～235Ma,各峰值分布受阶段性抬升剥露和热事件共同影响。P8与P5主要受热事件控制,P6、P4、P3、P2、P1主要和抬升剥露有关,P7主控因素不明显。裂变径迹年龄峰值与西昆仑及邻区发生的一系列重大构造事件的时限吻合,并伴随强烈的区域性断裂活动,指示裂变径迹年龄峰值记录了西昆仑及邻区构造演化的重大事件;其中,晚白垩世以来喜马拉雅东、西构造结抬升具有相似性,反映了青藏高原自印度板块与欧亚大陆碰撞以来经历了相似的阶段性抬升。柯克亚连续沉积剖面显示西昆仑及邻区4.7Ma以来开始最后一次大规模抬升,并指示上新世以来西昆仑及邻区的径迹年龄储备表现出由多样性向一致性、由无规律向年轻化的发展趋势,暗示4.7Ma以来的抬升具整体抬升性质;3.6Ma为抬升的转折点,表现为抬升剥露速率加快、基底开始大规模出露地表,西昆仑山对南边的水流形成障碍。 相似文献
14.
依据走滑断裂的运动学和年代学,确认滇西腾冲地区新生代大型走滑断裂带变形作用的三个阶段:1)始新世初(54-56Ma),在槟榔江两岸出露的与新特提斯俯冲和两大陆碰撞相关的左旋走滑-逆冲断裂,由此推断腾冲地块西缘南北向展布格局是两大陆碰撞后发生顺时针旋转达90°的结果.2)渐新世-中新世,腾冲地块东缘的高黎贡右旋走滑断裂和西缘的那邦右旋走滑断裂存在两个走滑活动的峰期:24-19Ma和11-14Ma,早期与Tapponnier模式中挤出块体东边界红河-哀牢山左旋走滑断裂活动的时限相一致,指示高黎贡和那邦右旋走滑断裂在此时期是挤出的印支地块的西边界;晚期与安达曼海的扩张、缅甸境内实皆断裂的右旋活动相一致,可能是此期地块再次发生挤出的结果.3)中新世末,约5-8Ma间两大陆的进一步会聚,引起了腾冲地区岩石圈结构的重要变化,腾冲地块发生了向南的挤出和顺时针的旋转,促成了一系列与此前右旋走滑相关的盆地的折返和南北向凹陷盆地的形成,制约了腾冲火山岩的喷发和整个地区的快速抬升.腾冲地块及其周缘新生代断裂带多阶段运动的转换对揭示青藏高原东南部块体运动型式具有重要的研究意义. 相似文献
15.
By a detailed investigation of geometry and kinematics of the Shangma (商麻) fault in Dabieshan (大别山),three different crust levels of extension movement have been recognized in sequence from the deep to the shallow:① low-angle ductile detachment shearing with top to the NW; ② low-angle normal fault with top to the NW or NWW in brittle or brittle-ductile transition domain; ③high-angle brittle normal fault with top to the W or NWW. Two samples were chosen for zircon U-Pb age dating to constrain the activity age of the Shangma fault. A bedding intrusive granitoid pegmatite vein that is parallel to the foliation of the low-angle ductile detachment shear zone of the country rock exhibits a lotus-joint type of boudinage deformation,showing syn-tectonic emplacing at the end of the ductile deformation period and deformation in the brittle-ductile transition domain. The zircon U-Pb dating of this granitoid pegmatite vein gives an age of (125.9±4.2) Ma,which expresses the extension in the brittle-ductile transition domain of the Shangma fault. The other sample,which is collected from a granite pluton cutting the foliation of the low-angle ductile detachment shear zone, gives a zircon U-Pb age of (118.8±4.1) Ma,constraining the end of the ductile detachment shearing. Then the transformation age from ductile to brittle deformation can be constrained between 126-119 Ma.Combined with the previous researches,the formation of the Luotian (罗田) dome,which is located to the east of the Shangma fault,can beconstrained during 150-126 Ma. This study gives a new time constraint to the evolution of the Dabie orogenic belt. 相似文献
16.
《Journal of South American Earth Sciences》2000,13(1-2):115-122
The Atacama Fault Zone is a major Mesozoic structure that trends along the Coastal Batholith of northern Chile. Part of the fault zone underwent a kinematic change from dip-slip to strike-slip displacement during the Early Cretaceous. The Las Tazas complex intruded the fault zone during this change. New analyses of country rock protomylonites from the edge of the complex firmly constrain the age of the change to 130 Ma and confirm that the complex was emplaced during active displacement along the fault zone. The intrusion heated its immediate country rocks and allowed localised ductile shearing during emplacement. Upper crustal intrusions like the Las Tazas complex are ideal targets for geochronological studies of major shear zones. 相似文献
17.
阿尔金山北段阿克塞—当金山口一带的裂变径迹测年证据表明,该地区于9～7 Ma以来发生过快速抬升和剥蚀,并且一直持续形成了现今所见的阿尔金山。新生代以来至少经历了三次抬升:早期43.6～24.3Ma、中期19.6～13.6 Ma、晚期9～7 Ma。抬升速率先缓慢、后相对快速,9～7 Ma以来的抬升速率为0.94 mm/a。晚期的构造拾升可能与阿尔金断裂带左行走滑活动有关,而与相邻的柴达木盆地北缘地区的构造抬升并不一致。 相似文献
18.
在1/5万袁家房子等四幅区域矿产地质填图的基础上,对乌兰巴山复式岩体的野外地质特征、岩石学、矿物学、地球化学和同位素年代学等方面进行了初步研究.同位素锆石U-Pb分析结果表明,206 Pb/238 U表面年龄为225.4±1.6 Ma岩体,侵位时代为早三叠纪.该岩体总体展布受区域北东向构造控制明显.岩石化学、地球化学表明该复式岩体属钙碱性岩;东壕欠闪长岩可能为地幔成因,并有地壳物质的加入,乌兰巴山等花岗岩、二长花岗岩可能为壳源成因.稀土元素配分曲线显示出向右倾的平坦曲线型,轻稀土富集,重稀土明显亏损,无明显的铕异常 相似文献
19.
Up-temperature flow of surface-derived fluids in the mid-crust: the role of pre-orogenic burial of hydrated fault rocks 总被引：1，自引：0，他引：1
The Walter‐Outalpa shear zone in the southern Curnamona Province of NE South Australia is an example of a shear zone that has undergone intensely focused fluid flow and alteration at mid‐crustal depths. Results from this study have demonstrated that the intense deformation and ductile shear zone reactivation, at amphibolite facies conditions of 534 ± 20 °C and 500 ± 82 MPa, that overprint the Proterozoic Willyama Supergroup occurred during the Delamerian Orogeny (c. 500 Ma) (EPMA monazite ages of 501 ± 16 and 491 ± 19 Ma). This is in contrast to the general belief that the majority of basement deformation and alteration in the southern Curnamona Province occurred during the waning stages of the Olarian Orogeny (c. 1610–1580 Ma). These shear zones contain hydrous mineral assemblages that cut wall rocks that have experienced amphibolite facies metamorphism during the Olarian Orogeny. The shear zone rock volumes have much lower δ18O values (as low as 1‰) than their unsheared counterparts (7–9‰), and calculated fluid δ18O values (5–8‰) consistent with a surface‐derived fluid source. Hydrous minerals show a decrease in δD(H2O) from ?14 to ?22‰, for minerals outside the shear zones, to ?28 to ?40‰, for minerals within the shear zones consistent with a contribution from a meteoric source. It is unclear how near‐surface fluids initially under hydrostatic pressure penetrate into the middle crust where fluid pressures approach lithostatic, and where fluid flow is expected to be dominantly upward because of pressure gradients. We propose a mechanism whereby faulting during basin formation associated with the Adelaidean Rift Complex (c. 700 Ma) created broad hydrous zones containing mineral assemblages in equilibrium with surface waters. These panels of fault rock were subsequently buried to depths where the onset of metamorphism begins to dehydrate the fault rock volumes evolving a low δ18O fluid that is channelled through shear zones related to Delamerian Orogenic activity. 相似文献
20.
《International Geology Review》2012,54(2):107-113
The lack of preserved Phanerozoic units within the Proterozoic Mount Isa Inlier of northern Australia renders it difficult to determine its Phanerozoic tectonic history. However, thermo-chronological methods provide a means for assessing this problem. Apatite fission-track data from the central and southern parts of the Inlier reveal periods of post-early Carboniferous accelerated cooling. Apatite fission-track ages vary from 235 to 390 Ma and corresponding mean track lengths range from 11.76 to 13.55 microns. These results record a protracted cooling history below about 110 ± 10° C. The earlier period of cooling revealed by the data occurred during middle Carboniferous time. The event resulted in >2 km of exhumation across the Inlier and probably was in response to intra-continental deformation associated with the Alice Springs Orogeny and tectonics in the adjacent Tasman Orogen. A high proportion of partly annealed fission tracks in the samples suggests that rocks now exposed across the Inlier resided at the top of the apatite partial annealing zone (approximately 60° C to 70° C) following the mid-Carboniferous cooling. Modeling of the fission-track age and length parameters suggests that approximately 30° C to 50° C of cooling occurred over the past 100 Ma. Assuming a geothermal gradient of 25° C/km, this corresponds to 1.2-2.0 km of exhumation. The post-Middle Cretaceous cooling possibly is related to extensional tectonics at the southern and eastern margins of the Australian plate during the Mesozoic and Tertiary periods and to the more recent collision at the northern margin of the plate. The spatial variation of apatite fission-track data within the Inlier indicates that the three major structural belts-the Western fold belt, Kalkadoon-Leichhardt belt, and the Eastern fold belt-exhibit similar thermal histories on a regional scale. It also indicates that the main N-S fault zones bounding the belts have not been reactivated in a vertical sense along their entire length since ～350 Ma. However, adjacent smaller-scale fault-bounded blocks within the belts demonstrate variable cooling histories, suggesting that reactivation of favorably oriented minor faults within the Inlier, including segments of the major faults, probably occurred during this time interval. Variations in apatite fission-track data along the 1994 Australian Geological Survey Organization/Australian Geodynamics Co-operation Research Center (AGSO/AGCRC) Mount Isa seismic traverse indicate that up to 1 km of vertical displacement has occurred between two major intrabelt fault zones since middle Carboniferous time. 相似文献