大陆碰撞造山样式与过程：来自特提斯碰撞造山带的实例

本文选取特提斯域内比利牛斯、阿尔卑斯、扎格罗斯、喜马拉雅-青藏高原四个地球上最年轻的陆-陆碰撞造山带,对其造山带结构、类型、物质组成、构造岩浆过程等方面进行详细介绍,进而讨论各个造山带的差异性及其缘由,分析碰撞造山普遍性规律。资料分析表明,四个碰撞造山带具有不同的结构和组成。根据板块汇聚方向与造山带边界间的夹角可将造山带分为正向和斜向两种;根据造山带结构可将碰撞带分为对称式和不对称式两种。由此本文将碰撞造山带划分为四种基本式样:正向对称式、正向不对称式、斜向对称式、斜向不对称式,分别以比利牛斯、青藏高原、阿尔卑斯和扎格罗斯碰撞带为代表。综合分析四个造山带碰撞以来的岩浆构造活动,本文发现完整的碰撞过程可以划分为三个阶段,第一阶段主要发生挤压缩短、地壳加厚,高压变质和钙碱性火山岩浆活动;第二阶段以大规模走滑系统发育和高钾钙碱性或钾质火山岩浆作用为特征;第三个阶段挤压应力向碰撞带两侧扩展,同时伴有大型伸展构造系统的发育。在这三阶段演化历程中,比利牛斯只进行到第一阶段,成为幼年夭折的碰撞带;扎格罗斯进行到第二阶段,出现调节挤压应变的走滑系统和钾质超钾质岩浆活动;青藏高原和阿尔卑斯进行到第三个阶段,以发育大型伸展构造和钾质、超钾质岩浆活动为特征,但后者在造山带物质组成和汇聚速率方面显示出比前者更成熟的造山演化程度。因此认为岩石圈组成是碰撞造山带结构的主要控制因素,如果上覆板块具有相对不稳定的岩石圈,会使得碰撞带后陆发育宽广的构造岩浆带,造成造山带呈不对称式结构。     

Structural deformation and evolution of right-lateral strike-slip tectonics of the Liaohe western depression during the early Cenozoic

The Tan-Lu fault zone (TLFZ) traverses the Liaohe western depression (LHWD), affords an exceptional opportunity to reveal the structural deformation and evolution of a major strike-slip fault of the LHWD using three dimensional seismic data and well data. In this paper, based on structural interpretations of the 3-D seismic data of the LHWD, combined with depth slice and seismic coherency, a variety of structural features in relation to right-lateral strike-slip fault (the western branch of the Tan-Lu fault) have been revealed presence in the depression, such as thrust faults (Xinlongtai, Taian-Dawa, and Chenjia faults), structural wedges, positive flower structures, and en echelon normal faults. Fault cutoffs, growth strata and the Neogene unconformity developed in the LHWD verify that the activity of right-lateral strike-slip from the late Eocene to Neogene (ca. 43–23 Ma). The study indicates that the right-lateral strike-slip played an important role in controlling the structural deformation and evolution of the LHWD in the early Cenozoic. Moreover, the front structural wedge generated the gross morphology of the Xinlongtai anticline and developed the Lengdong faulted anticline during the late Eocene, and the back structural wedge refolded the Lengdong faulted anticline zone in the late Eocene to the early Oligocene. Wrench-related structures (the Chenjia thrust fault and the en echelon normal faults) were developed during the late Oligocene. Uniform subsidence in the Neogene to Quaternary. Furthermore, the driving force of the right-lateral strike-slip deformation was originated from N–S extension stress related to the opening of the Japan Sea and NE–SW compression, as the far-field effect of India–Eurasia convergence.     

Cenozoic Eurasia is not a single rigid plate: Paleomagnetic evidence

The widely distributed Cenozoic paleomagnetic inclination anomaly in Asia is usually attributed to either a widespread error of magnetic field recording due to an inclination flattening mechanism in sediments, or to the persistence of an anomalous non-dipolar component of the geomagnetic field throughout the Tertiary. Based on an analysis of the Asian paleomagnetic database for Meso-Cenozoic times, we suggest that instead this puzzling anomaly results from an overlooked global plate tectonics cause where the wide so-called Eurasian plate would have suffered from previously undetected transpressive north–south relative movements between its western and eastern ends since the Cretaceous. These relative movements are most probably accommodated by a component of right-lateral shear movement distributed in the Tornquist–Tesseyre zone, and a localized left-lateral shear movement in the Ural Mountain chain during the Tertiary. Therefore, Eurasia was not the single rigid plate that Cenozoic plate reconstructions have accepted.     

青藏高原东部及周边现时地壳运动

通过1991—2001年期间在青藏高原东部及周边地区的GPS测量,获得该地区不同参考框架下的地壳运动速度场,其测量的速度精度高于2mm／yr。印度板块与华北地块之间的地壳形变分为喜马拉雅及高原南部、高原中部(拉萨—格尔木)和高原北部(格尔木—金塔)三部分,它们分别吸收了印度板块与欧亚板块汇聚速率的43％、24％和32％。在欧亚框架下和相对于成都,印度板块和华南地块之间存在着以东喜马拉雅构造结为轴心的顺时针巨型涡旋构造——滇藏涡旋构造,运动速度分别为26～6mm／yr和24～7mm／yr,总体上从北东方向转变为南东和南西方向,有别于青藏高原中部的北东方向。滇藏涡旋和东喜马拉雅构造结的形成与南迦巴瓦—阿萨姆“犄角”的楔入作用有关。     

A Review Of Slr Contributions To Geophysics In Eurasia By Cgs

In the past 30 years the Satellite Laser Ranging(SLR) technique has improved to a large extent, currently achieving a ranging precision down toa few millimeters. Moreover the growth in the size of the international network of SLR stations and therapidly growing constellation of geodetic target satellites make the SLR a well established technique for solidEarth studies and for the related Earth subsystem sciences. The long SLR observation history has become a veryimportant source of data for global and local changes detection and monitoring in many different fields.Tectonic plate motion, crustal deformation, post-glacial rebound and subsidence, Earth rotation, and polarmotion, time variations of the Earth's gravitational field, ocean tides modeling, center of mass of the totalEarth system monitoring, International Terrestrial Reference System (ITRS) maintenance are only themain applications in which the SLR technique plays a significant role. Plate boundary zones in whichdeformation is diffuse are in general geographical areas associated with high seismic and volcanic activity.A principal key to understand the geophysics of a plate boundary process is the detailed knowledge of the3-D kinematics. This work will focus on the relevant results of the Eurasian SLR subnetwork in termsof technological evolution and crustal deformation. A general overview of the Eurasian SLR stationperformance will be presented with particular reference to the state-of-the-art SLR observatory MLRO (Matera LaserRanging Observatory). The current tectonic deformations (velocity and strain-rate field) detectedby the Eurasian network and by the former WEGENER/MEDLAS campaigns will also be discussed.     

Permo–Triassic intraplate magmatism and rifting in Eurasia: implications for mantle plumes and mantle dynamics

At the transition from the Permian to the Triassic, Eurasia was the site of voluminous flood-basalt extrusion and rifting. Major flood-basalt provinces occur in the Tunguska, Taymyr, Kuznetsk, Verkhoyansk–Vilyuy and Pechora areas, as well as in the South Chinese Emeishen area. Contemporaneous rift systems developed in the West Siberian, South Kara Sea and Pyasina–Khatanga areas, on the Scythian platform and in the West European and Arctic–North Atlantic domain. At the Permo–Triassic transition, major extensional stresses affected apparently Eurasia, and possibly also Pangea, as evidenced by the development of new rift systems. Contemporaneous flood-basalt activity, inducing a global environmental crisis, is interpreted as related to the impingement of major mantle plumes on the base of the Eurasian lithosphere. Moreover, the Permo–Triassic transition coincided with a period of regional uplift and erosion and a low-stand in sea level. Permo–Triassic rifting and mantle plume activity occurred together with a major reorganization of plate boundaries and plate kinematics that marked the transition from the assembly of Pangea to its break-up. This plate reorganization was possibly associated with a reorganization of the global mantle convection system. On the base of the geological record, we recognize short-lived and long-lived plumes with a duration of magmatic activity of some 10–20 million years and 100–150 million years, respectively. The Permo–Triassic Siberian and Emeishan flood-basalt provinces are good examples of “short-lived” plumes, which contrast with such “long lived” plumes as those of Iceland and Hawaii. The global record indicates that mantle plume activity occurred episodically. Purely empirical considerations indicate that times of major mantle plume activity are associated with periods of global mantle convection reorganization during which thermally driven mantle convection is not fully able to facilitate the necessary heat transfer from the core of the Earth to its surface. In this respect, we distinguish between two geodynamically different scenarios for major plume activity. The major Permo–Triassic plume event followed the assembly Pangea and the detachment of deep-seated subduction slabs from the lithosphere. The Early–Middle Cretaceous major plume event, as well as the terminal–Cretaceous–Paleocene plume event, followed a sharp acceleration of global sea-floor spreading rates and the insertion of new subduction zone slabs deep into the mantle. We conclude that global plate kinematics, driven by mantle convection, have a bearing on the development of major mantle plumes and, to a degree, also on the pattern of related flood-basalt magmatism.     

华南地块的地极移动曲线及其地质意义

结合最近获得的古地磁数据,作者重新计算编制了华南地块的地极移动曲线,进而讨论了华南和华北地块在早古生代的地理位置,二者最后拼合的时代,以及华南地块和欧亚大陆北部两条极移曲线之间的系统偏差等问题。     

欧亚大陆及西太平洋边缘海瑞利面波频散反演

从亚洲、欧洲及西太平洋地区台网113个数字地震台所记录的分布在40°W~180°E,40°S~80°N范围内近万个地震事件中,挑选出发生在1982-2005年间,震级绝大部分在5.0~7.0之间,震源深度小于100 km的1 700余个事件。共得到周期在8~400 s之间9 980余条质量较高的瑞利面波频散曲线进行面波频散反演,得到欧亚大陆及西太平洋边缘海28个周期的群速度分布图。反映了欧亚大陆及西太平洋边缘海横向和纵向存在着明显的非均匀性。