Probing fault zone heterogeneity on the Nojima fault: Constraints from zircon fission-track analysis of borehole samples   总被引：2，自引：0，他引：2  

Takahiro Tagami  Masaki Murakami 《Tectonophysics》2007,443(3-4):139

Fission-track (FT) thermochronologic analysis was performed on zircon separates from rocks in and around the Nojima fault, which was activated during the 1995 Kobe earthquake. Samples were collected from the University Group 500 m (UG-500) borehole and nearby outcrops. FT lengths in zircons from localities > 25 m away from the fault plane as well as one 0.1 m away from the fault in the footwall are characterized by concordant mean values of  10–11 μm and unimodal distributions with negative skewness, which showed no signs of appreciable reduction in FT length. In contrast, those adjacent (< 3 m) to the fault at depths on the hanging wall side showed significantly reduced mean track lengths of  6–8 μm and distributions having a peak around 6–7 μm with rather positive skewness. The former pattern is interpreted to reflect cooling through the zircon partial annealing zone (ZPAZ), without later, partial thermal overprints. The latter indicates substantial track shortening due probably to secondary heating by a thermal event(s) that locally perturbed the geothermal structure. Modeled zircon FT length and age data of partially annealed samples from the UG-500 borehole revealed a cooling episode in the ZPAZ that started at  4 Ma within  3 m from the fault plane, whereas those from the Geological Survey of Japan 750 m borehole record cooling started at  31–38 Ma within  25 m from the fault. On the basis of one-dimensional heat conduction modeling as well as the consistency between the degree of FT annealing and the degree of deformation/alteration of borehole rocks, these cooling ages in both boreholes are interpreted as consequences of ancient thermal overprints by heat transfer or dispersion via fluids in the fault zone. Together with the zircon FT data of a pseudotachylyte layer recently analyzed, it is suggested that the present Nojima fault system was reactivated in the Middle Quaternary from an ancient fault initiated at  56 Ma at mid-crustal depths. Also shown is a temporal/spatial variation in terms of the thermal anomalies recorded in the fault rocks, implying heterogeneity of hot fluid flows in the fault zone.  相似文献   

胶东栖霞大霞址断裂南段金矿地质特征及成因研究          下载免费PDF全文

彭雪峰 《山东国土资源》2022,38(11)

近年来胶东栖霞大霞址断裂南段发现了多个金矿床。文章从蚀变带特征、矿体空间展布特征等方面阐述了研究区金矿地质特征;从地层、岩浆岩、构造“三位一体”分析总结了控矿因素;通过与典型矿床的分析对比,认为该区金矿床类型属于构造蚀变岩型,金矿与硅化、绢英岩化、黄铁矿化关系最为密切;结合对成矿物质来源、成矿流体运移、沉淀、富集等的认识,对大霞址断裂金矿的成因进行了总结,建立了成矿模式,提出了下一步找矿建议。  相似文献   

Determination of the fault plane using a single near-field seismic station with a finite-dimension source model     

D. Legrand  & B. Delouis 《Geophysical Journal International》1999,138(3):801-808

We explore the possibility of determining the actual fault plane of an earthquake from the inversion of near-source displacement seismograms of one station when a finite-dimension source is used instead of a point source model and when the complete displacement is taken into account, including near-field waves. Tests on synthetic seismograms and real data recorded at local distances show that this is possible even with a single, three-component station. A single accelerogram available for the Erzincan, Turkey, 1992 March 13, M _s = 6.8 earthquake is inverted and the solution found is compatible with other seismological studies and with the mechanism expected for the North Anatolian Fault.  相似文献   

同生断层及其伴生褶曲的组合式样     

陈大贤 《现代地质》1991,5(4):366-377

石油钻探遇断层而失败的情形时有发生,其中多数是由于对同生断层及其伴生褶曲认识的错误所引起。为减少勘探失误,本文讨论了同生断层及其伴生褶曲空间组合的一些规律。（1）同生断层可分为盆地边界同生断层和内部同生断层两大类。边界同生断层的断面产状基本形态有勺形、椅形、阶形和坎形四种。（2）边界同生断层是追踪盆前的一组或两组基底断裂发育而成的。单向追踪的边界同生断层平面伸展较平直;双向追踪的边界同生断层平面伸展呈锯齿形。（3）内部同生断层及其伴生褶曲在剖面上的组合式样有正牵引和同向y字形派生断层、逆牵引和反向y字形派生断层。这两类四种形变可单一出现,也可在同一剖面中共存。（4）内部同生断层系的平面组合基本式样有帚状和雁列两种。构成地堑式的两条同生断层断距都较大时就会有挤压背斜出现（构成w形构造）。（5）中国东部裂谷系盆地中的所谓“滚动背斜”都不具备标准的“滚动”特征;它只产生在特定的层位上;对它与其称“滚动背斜”,不如称“逆牵引背斜”为宜。  相似文献   

论大陆岩石圈内的垂直转换断层     

白文吉  杨经绥  任玉峰 《地质力学学报》1997,3(3):53-58

近些年来,地震测深和重力测量方法揭示出大陆岩石圈内存在一组穿透地壳并延深到上地幔的高角度断裂,经厘定,被命名为垂直转换断层(vertical trans-form fault)。原只认为它们存在于高亚洲,包括青藏高原。本文表明其也出现于低亚洲西伯利亚平原。大陆岩石圈内是否普遍存在垂直转换断层以及它们在大陆岩石圈动力学研究中的意义,是今后构造地质学研究的方向之一。   相似文献   

新疆伽师及邻区地震与控震构造分析     

吴珍汉  吴淦国  孙宝珊 《地质力学学报》1997,3(3):4-11

1996年3月-1997年4月间,新疆伽师西部相继发生6.9级强震与由7次6-6.6级子震所构成的强震群。历史上伽师及邻区曾发生多次强烈地震,导致伽师及邻区包括塔里木盆地周缘地震强烈活动的原因,是印度岩石圈块体快速北向运动造成的SN向强烈挤压与欧亚岩石圈块体缓慢向西运动所引起的左旋走滑的联合作用及其相关的现今不同方向、不同性质的断裂活动。区域性EW向盆缘活动断裂控制盆缘大型地震活动带的空间展布,盆缘EW向主干活动断裂与其他方向次级活动断裂的交叉复合部位是强烈地震发震的有利部位。伽师强震群子震震中分布受塔里木盆地西缘近SN-NNW向隐伏深断裂及其与EW向盆缘活动断裂的复合所控制。伽师强震群发生之后,在原强震群震中处发生7级以上更大地震的可能性很小;但由于塔里木盆地及其周缘,自1996年起已进入一个新的地震活跃期,在伽师附近及其南侧或东侧,近年内发生6-7级以上强烈地震的可能性较大。   相似文献   

云开地区断裂构造对金矿的控制作用     

陈树旺 《地质与资源》1994,3(1):32-37

云开地区断裂构造对金矿的控制主要表现在两个方面：其一,断裂带带内的大断裂及大断裂的次级断裂,分别控制着区内的金矿带、矿带内的主要金矿床（点）及金矿体;其二,断裂构造的力学性质、活动期次及构造岩发育程度等,控制或影响着金矿的矿石组构特征、矿化期次及矿化强度等。本文还对断裂构造的控矿机制进行了探讨。  相似文献   

河北省赤城县赵家沟金矿成矿地质条件及找矿方向初探     

陈宝双 《地质与资源》1993,2(4):326-331

该矿床产于尚义-赤城深断裂南侧之水泉沟正长岩外接触带中。区内主要地层为桑于群第二岩段,原岩为一套中基一中酸性火山熔岩,含金量平均为46×10^-9。矿体主要受控于东西向断裂带中,该带既为导矿构又是容矿构造。矿体具垂直分带特点。即地表为石英脉型,往深部渐变为蚀变岩型。区内赵家沟正长岩属于印支期水泉沟碱性杂岩体东延部分,含金量平均为22.2×10^-9;赵家沟金矿床形成与该岩体密切相关,岩体外接触带是本区找矿的有利地段。  相似文献   

Magnitude of lateral displacement on the Crevillente Fault Zone (Betic Cordillera,SE Spain): stratigraphical and sedimentological considerations     

L. M. Nieto  J. Rey 《Geological Journal》2004,39(1):95-110

The Crevillente Fault Zone (CFZ) comprises a system of northeast to southwest oriented dextral faults that extend for some 600 km in the External Zones of the Betic Cordillera (SE Spain). The magnitude of lateral displacement related to this fault zone is not well constrained, and it is considered to be between 20 and 400 km. The stratigraphical and sedimentological criteria used in this work have proven effective in quantifying the magnitude of the displacement along this structure. We have analysed an oolitic turbidite facies in the Middle Jurassic of the Sierra de Ricote (Median Subbetic of Murcia Province). A detailed revision of ooidal limestone outcrops has revealed that the source area of these deposits was to the Internal Subbetic zone, north of Vélez Rubio (Almería Province). These two tectonic units, the Median and Internal Subbetic, are currently 75 km from each other and separated by the CFZ. The conclusions arising from our stratigraphical, petrological and sedimentological studies favour interpretation of a 75–100 km lateral displacement. After restoring the Late Jurassic–Cretaceous anticlockwise rotation of Iberia, the CFZ appears to belong to the E–W palaeofault system that is related to the extension of the South Iberian Continental Margin (SICM). Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

陷落柱伴生断层特征及陷落柱预测   总被引：5，自引：0，他引：5  

褚志忠 《煤田地质与勘探》1998,26(3):26-28

通过对陷落柱伴生断层的分布规律、性质及特征的研究,认识了断层带内煤岩层特征及与周围煤岩层的关系,并以此对陷落柱进行预测预报,取得了较好的效果,该方法便于生产现场推广应用。   相似文献