High-altitude Plio–Quaternary fluvial deposits and their implication on the tilt of a horst, western Anatolia, Turkey     

M.L. Süzen  V. Toprak  B. Rojay 《Geomorphology》2006,74(1-4):80-99

This study investigates the origin and regional tectonic implications of high-altitude Plio (?)–Quaternary fluvial deposits developed over the Bozdağ horst which is an important structural element within the horst–graben system of western Anatolia, Turkey.A total of 23 deposits occur near the modern drainage divide comprising fluvial to occasionally lacustrine deposits. The deposits are all elongated in N–S direction with a width / length ratio of 1 / 10. The largest of them is of 13 km in length with a maximum observable thickness of about 100–110 m. Morphological, lithological, deformational characteristics of these deposits and the drainage system of the area all suggest that the deposits were formed due to uplift and southward tilting of the Bozdağ horst. This tilting which is estimated as 1.2° to 2.2° caused accumulation of the stream load along channels flowing from south to north. All the deposits were later dissected by the same streams with the exception of one deposit which still preserves its original lake form. These deposits are of Quaternary age, which corresponds to the latest N–S directed extensional tectonic phase in the region.  相似文献   

Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene     

Antonio Schettino  Eugenio Turco 《Geophysical Journal International》2006,166(3):1398-1423

The tectonic history of the Western Mediterranean region during the Oligocene and Early Miocene is illustrated through a series of plate reconstructions, from chron C13n to chron C6n. The reconstructions are based on a new interpretation of published magnetic anomaly data and two-ships seismic data, and their integration with known geological constraints, in order to determine style and timing of the backarc extension processes in the Liguro-Provençal, Valencia and Algerian basins. In particular, a reinterpretation of the regional magnetic anomaly field allowed the calculation of the instantaneous Euler poles associated with the motion of 11 microplates relative to Eurasia and Iberia. Furthermore, a quantitative analysis of the acoustic basement morphology and the balancing of deep crustal profiles were used to estimate the closure and pre-rift rotation angles associated with the Euler poles of opening of the Ligurian, Provençal, Valencia and Algerian basins. This rigorous reconstruction of the geometry of the pre-rift continental margins of Iberia and Eurasia could furnish important insights into the study of Mediterranean tectonics for older times.  相似文献   

A catalogue of Spanish archaeomagnetic data     

M. Gómez-Paccard  G. Catanzariti  V. C. Ruiz-Martínez  G. McIntosh  J. I. Núñez  M. L. Osete  A. Chauvin  Ph. Lanos  D. H. Tarling  D. Bernal-Casasola  J. Thiriot  'Archaeological Working Group'ast 《Geophysical Journal International》2006,166(3):1125-1143

A total of 58 new archaeomagnetic directions has been determined from archaeological structures in Spain. Together with five previous results they allow the compilation of the first archaeomagnetic catalogue for Spain, which includes 63 directions with ages ranging between the 2nd century BC and the 20th century AD. Characteristic remanence directions have been obtained from stepwise thermal and alternating field demagnetization. The hierarchical structure has been respected in the calculation of the mean site directions. Rock magnetic experiments reveal that the main magnetic carrier is magnetite or titanomagnetite with different titanium contents. The age estimate of the studied structures is generally well justified by archaeological constraints. For six structures the proposed date is also supported by physical methods. The data are in close agreement with the French secular variation (SV) curve. This catalogue represents the first step in the construction of a SV curve for the Iberian Peninsula, which will be of much use in archaeomagnetic dating and in modelling of the Earth's magnetic field in Western Europe.  相似文献   

Excess Ar-free phengite in ultrahigh-pressure metamorphic rocks from the Lago di Cignana area, Western Alps     

Chitaro Gouzu  Tetsumaru Itaya  Hironobu Hyodo  Takaaki Matsuda   《Lithos》2006,92(3-4):418-430

Ar/Ar analyses of phengites and paragonites from the ultrahigh-pressure metamorphic rocks (zoisite–clinozoisite schist, garnet–phengite schist and piemontite schist) in the Lago di Cignana area, Western Alps were carried out with a laser probe step-heating method using single crystals and a spot dating method on thin sections. Eight phengite and two paragonite crystals give the plateau ages of 37–42 Ma with 96–100% of ³⁹Ar released. Each rock type also contains mica crystals showing discordant age spectra with age fractions (20–35 Ma) significantly younger than the plateau ages. Phengite inclusions in garnet give ages of 43.2 ± 1.1 Ma and 44.4 ± 1.5 Ma, which are significantly older than the spot age (36.4 ± 1.4 Ma) from the matrix phengites, and the plateau ages from the step-heating analyses. Inclusion ages (43 and 44 Ma) are consistent with a zircon SHRIMP age (44 ± 1 Ma) in this area. These results suggest that the oceanic materials that underwent a simple subduction related UHPM, form excess ⁴⁰Ar-free phengite and that the peak metamorphism is ca. 44 Ma or little older. We suggest that matrix phengites experienced a retrogression reaction changing their chemistry contemporaneously with deformation related to the exhumation of rocks releasing significant radiogenic ⁴⁰Ar from the crystals. This has lead to the apparent ages of the matrix phengites that are significantly younger than the inclusion age.  相似文献   

Seismic activity at the western Pyrenean edge   总被引：1，自引：1，他引：1  

M. Ruiz  J. Gallart  J. Díaz  C. Olivera  D. Pedreira  C. Lpez  J.M. Gonzlez-Cortina  J.A. Pulgar 《Tectonophysics》2006,412(3-4):217-235

The present-day seismicity at the westernmost part of the Pyrenean domain reported from permanent networks is of low to moderate magnitude. However, it is poorly constrained due to the scarce station coverage of the area. We present new seismic data collected from a temporary network deployed there for 17 months that provides an enhanced image of the seismic activity and its tectonic implications. Our results delineate the westward continuity of the E–W Pyrenean band of seismicity, through the Variscan Basque Massifs along the Leiza Fault, ending up at the Hendaya Fault. This seismicity belt is distributed on a crustal scale, dipping northward to almost 30 km depth. Other relevant seismic events located in the area can be related to the central segment of the Pamplona fault, and to different E–W thrust structures.  相似文献   

The recent fault scarps of the Western Alps (France): Tectonic surface ruptures or gravitational sackung scarps? A combined mapping, geomorphic, levelling, and Be dating approach     

Jean-Claude Hippolyte  Gilles Brocard  Marc Tardy  Grard Nicoud  Didier Bourls  Rgis Braucher  Gilles Mnard  Blaise Souffach 《Tectonophysics》2006,418(3-4):255-276

In the Western Alps, some recent scarps were previously interpreted as surface ruptures of tectonic reverse and normal faults that agree with microseismicity and GPS measurements. Our analysis shows that in fact there are hundreds of recent scarps, up to 30 m high and 2.1 km long, with only pure normal motions. They share the same characteristics as typical sackung scarps. The scarps are mainly uphill facing, parallel to the ridge crests and the contour lines. They are relatively short (less than 2.1 km) with respect to tectonic fault ruptures, and organized in swarms. They cut screes and relict rock glaciers with a slow (commonly 1 mm/year) average slip rate. In the Aiguilles Grives massif these sackung scarps clearly express the gravitational toppling of sub-vertical bedding planes in hard rocks. In contrast, the Belledonne Outer Crystalline Massif exhibits scarps that stem from the gravitational reactivation of conjugate tectonic faults. The recent faults extend to about 1600 m beneath the Rognier ridge crest, but are always above the valley floor. The main scarp swarm is 9.2 km long and constitutes the largest sackung ever described in the Western Alps. ¹⁰Be dating of a scarp and offset surfaces shows that > 4 m slip may have occurred rapidly (in less than 3800 years) sometimes between the end of the glaciation and 8800 ± 1900 years ago. This dating, together with the location of some faults far from the deep glacial valleys, suggests that sagging might have been triggered by strong earthquakes during a post-glacial period of probably enhanced seismicity. The Belledonne and Synclinal Median faults (just beneath the Rognier sackung) could have been the sources of this seismicity.  相似文献   

台湾西部前陆盆地的构造格局和演化规律   总被引：1，自引：4，他引：1  

王海荣  王英民  刘振湖  周爱华  黄奇志 《大地构造与成矿学》2006,30(3):275-282

基于对台湾岛、台湾海峡和周边海域(南海、东海)的盆山系统、相应动力学机制、构造单元以及其他诸多造山带和毗邻前陆盆地的研究,提出了台湾西部前陆盆地演化的4阶段模式,即:①增生楔发育-单向物源阶段;②挠曲响应-双向物源阶段;③前陆盆地系统形成阶段;④造山带坍塌-前陆衰退阶段。并对各阶段的构造特征、沉积特征和物源供给方式的差异给予了探讨,认为在增生楔发育-单向物源阶段,尽管增生楔业已推覆至陆缘层序之上,但盆地依然呈被动陆缘的外廓特征,以大陆方向为盆地的唯一物源;在挠曲响应-双向物源阶段,盆地开始明显出现挠曲响应,增生楔开始具备并逐步加大向盆地供应沉积物质的能力,但依然以大陆方向为主要物源方向;在前陆盆地系统形成阶段,前渊和前隆区逐步形成,在来自唯一物源、后陆方向造山带物质的快速充填下,前陆期层序快速向前隆方向超覆,形成典型的前陆楔形体;在造山带坍塌-前陆衰退阶段,伸展作用出现并快速扩展,前渊抬升,前陆层序遭受剥蚀,火山作用重新出现。并探讨了该模式是否具有周缘前陆盆地的普遍适用性。  相似文献   

甘肃文县地区阳山超大微细浸染型金矿床的成因与类型   总被引：11，自引：1，他引：11  

程斌张复新  贺国芬 《地质通报》2006,25(11):1354-1360

含矿岩石为本区泥盆系的一套Au含量较高的炭-硅-泥质地层.其中发现大量含As异常(含As约0.15%)的草莓状黄铁矿;矿体沿断裂带呈构造透镜体-扁豆体斜列等间距分布,产于断裂带中次级破碎带或顺层剪切带内;在早-中期阶段的矿化硫化物中,金以不可见金赋存于合As黄铁矿及毒砂中,含As黄铁矿发育增生环带,载金矿物主要沿片理化带呈微细浸染状分布;在中-晚期阶段的金属硫化物-石英碎裂脉体中,可见显微颗粒金;斜长花岗斑岩为地壳重熔型花岗岩,具多期次性;H、O、S同位素及流体包裹体资料表明,成矿流体以大气降水为主,岩浆水也参与成矿.由此可见,阳山金矿具沉积-岩浆叠加-构造及热液改造的多因复成特征,矿床属超大型卡林-类卡林复合型金矿床.  相似文献   

秦岭造山带商南-西峡地区富水杂岩的变辉长岩中斜锆石与锆石U-Pb同位素年龄的差异   总被引：9，自引：4，他引：9  

李惠民陈志宏  相振群李怀坤陆松年  周红英宋彪 《地质通报》2006,25(6):653-659

秦岭造山带富水杂岩体的一些变辉长岩含有粒度较大且U、Pb含量较高的斜锆石和锆石,是U-Pb同位素测年的极好矿物.对该杂岩体的中粗粒角闪黑云辉长岩中的斜锆石和锆石分别进行了SHRIMP法和TIMS法U-Pb同位素年龄测定,获得斜锆石和锆石的U-Pb同位素年龄分别为501.4 Ma±1.2 Ma和480.0 Ma±3.4Ma,两者相差约20 Ma.对该岩石中部分斜锆石向锆石转化的现象及锆石的成因进行了初步研究,认为斜锆石的U-Pb同位素年龄应解释为秦岭富水杂岩中基性岩石的形成时代,而锆石的成因及其U-Pb同位素系统在变质作用过程中的变化比较复杂,对其U-Pb同位素年龄地质意义的合理解释需做进一步的研究.  相似文献   

川西喜马拉雅期碰撞造山带岩浆碳酸岩的地幔源区特征——Pb-Sr-Nd同位素证据   总被引：5，自引：0，他引：5  

田世洪  侯增谦  袁忠信谢玉玲费红彩尹淑苹衣龙升杨志明 《岩石学报》2006,22(3):669-677

对形成于大陆碰撞带内的川西碳酸岩进行了详细的Pb-Sr-Nd同位素分析.结果表明,川西碳酸岩具有非常负的εNd值（-3.2～-18.7）和高的（^87Sr/^86Sr）i值（0.706020～0.707923）,以及较宽的^207Pb/^204Pb值（15.362～15.679）和^208Pb/^204Pb值（38.083～39.202）的特征,明显不同于世界上由非造山作用形成的碳酸岩.它们的Sr-Nd、Pb-Pb、Sr-Pb和Nd-Pb同位素特征表明大多数碳酸岩来源于EM Ⅰ与EMⅡ之间的一种混合地幔,与元古宙不同质量比的深海/陆源沉积物和下覆的似MORB由俯冲作用引起的洋壳的再循环有关,而少数碳酸岩则受到地壳物质混染的结果.此外,通过动力学背景分析可以得出,富集地幔EM Ⅰ与EMⅡ之间的熔融产生了川西碳酸岩以及同时代的富钾岩浆岩,这种熔融可能是由于印度大陆板片与扬子大陆板片俯冲引起的新生代软流圈物质的上涌产生的,并发生于青藏高原东缘始新世-渐新世分界线的从转换压扭变形向转换张扭变形的转变过渡的构造背景下.  相似文献