Is northern Honshu a microplate?

Seismic slip vectors along the Japan Trench, the eastern margin of the Japan Sea and the Sagami Trough are compared with global relative plate motions (RM2, Minster and Jordan, 1978) to test a new hypothesis that northern Honshu, Japan, is part of the North American plate. This hypothesis also claims that the eastern margin of the Japan Sea is a nascent convergent plate boundary (Kobayashi, 1983; Nakamura, 1983).Seismic slip vectors along the Japan Trench are more parallel to the direction of the Pacific-North American relative motion than that of the Pacific-Eurasian relative motion. However, the difference in calculated relative motions is too small avoid to the possibility that a systematic bias in seismic slip vectors due to anomalous velocity structure beneath island arcs causes this apparent coincidence. Seismic slip vectors and rates of shortening along the eastern margin of the Japan Sea for the past 400 years are also consistent with the relative motion between the North American and Eurasian plates calculated there. Seismic slip vectors and horizontal crustal strain patterns revealed by geodetic surveys in south Kanto, beneath which the Philippine Sea plate is subducting, indicate two major directions; one is the relative motion between the North American and Philippine Sea plates, and the other that between the Eurasian and Philippine Sea plates.One possible interpretation of this is that the eastern margin of the Japan Sea may be in an embryonic stage of plate convergence and the jump of the North American-Eurasian plate boundary from Sakhalin-central Hokkaido to the eastern margin of the Japan Sea has not yet been accomplished. In this case northern Honshu is a microplate which does not have a driving force itself and its motion is affected by the surrounding major plates, behaving as part of either the Eurasian or North American plate. Another possibility is that the seismic slip vectors and crustal deformations in south Kanto do not correctly represent the relative motion between plates but represent the stresses due to non-rigid behaviors of part of northern Honshu.     

Active right-lateral strike-slip fault zone along the southern margin of the Japan Sea

We describe an active right-lateral strike-slip fault zone along the southern margin of the Japan Sea, named the Southern Japan Sea Fault Zone (SJSFZ). Onshore segments of the fault zone are delineated on the basis of aerial photograph interpretations and field observations of tectonic geomorphic features, whereas the offshore parts are interpreted from single-/multichannel seismic data combined with borehole information. In an effort to evaluate late Quaternary activity along the fault zone, four active segments separated by uplifting structures are identified in this study. The east–northeast-trending SJSFZ constitutes paired arc-parallel strike-slip faults together with the Median Tectonic Line (MTL), both of which have been activated by oblique subduction of the Philippine Sea plate during the Quaternary. They act as the boundaries of three neotectonic stress domains around the eastern margin of the Eurasian plate: the near-trench Outer zone and NW–SE compressive Inner zone of southwest Japan arc, and the southern Japan Sea deformed under E–W compression from south to north.     

亚洲大地构造的演化

<正> 一、引言 最近作者用板块构造观点编制了一幅八百万分之一的亚洲大地构造图。从这幅图可以清楚地认识到亚洲地质构造比较复杂。它并非从古以来就是一个完整的大陆块,而是由于地壳长期以来分离聚合演化的结果。板块构造在地球上开始于什么时候,目前尚无定论。亚洲大地构造图的编制,主要是从显生宙初期开始的。     

南海的右行陆缘裂解成因

南海成果是西太平洋边缘海动力学研究的重要部分,也关系到特提期,环太平洋两大超级会聚带的相互作用,是国内外地学界长期研究的热点问题。西太平洋边缘海内带,尤其是日本海和南海在形成时代,海盆形态和海底地貌,海底扩张的多轴,多阶段,由东向西扩展特征,岩石圈地幔的地球化学异常等方面具有共同特征,可能在成因上也相似,南海的海盆的楔形的楔形形状,海底扩张及陆架盆地的断陷的由北向南发展和自东向西推进的特征,地壳伸展减薄和海底扩张程度的由东向西减弱都可用尖端向西的“剪刀模型”来描述,即南海的张开是近南北向右行剪切力作用下东亚陆缘发生裂解的结果。南海张开的同时在海盆内及其西缘印支半岛上发育大量近南北向右行走滑断裂,表明当时存在区域性的近南北向右行剪切应力,而在其东缘现在看不到大型近南北向右行走滑断裂,可能是在中中新世以后受从赤道附近近滑移北上并沿马尼拉海沟仰冲的菲律宾群岛所破坏的结果。晚中生代以来,在西太平洋构造域,特提斯构造域西段（印度）及东段（澳大利亚）先后发生了朝欧亚大陆的,不同方向和速度的会聚。在这三大作用的复合和竞争的动力学背景下,东亚陆缘发生了有地幔参加传动的“超级剪切”,其应力场经历了左行压扭体制和右行张扭体制交替的阶段性变化,正是在特提斯构造域西段的会聚起主导作用的阶段,东亚陆缘在右行张扭应力场作用下发生裂解,形成了南海和其他内带边缘海。     

地层特征对比研究在地体解析中的意义

不同地区地层特征的对比研究,是地体解析的重要方法之一。在对中国那丹哈达地区和日本美浓地区出露的地层、岩石等进行对比研究后认为,在老第三纪日本海尚未形成之前它们是连在一起的统一的地体。三叠纪时它们在赤道附近生成,侏罗纪—白垩纪时随板块运动增生于亚洲东部大陆边缘,白垩纪—老第三纪时左行剪切北移,新第三纪时因日本海的扩张而分裂移动到现今的位置。     

Evolution of the eastern margin of Korea: Constraints on the opening of the East Sea (Japan Sea)

We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the eastern Korean margin that led to the separation of the southwestern Japan Arc. The eastern Korean margin is rimmed by fundamental elements of rift architecture comprising a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. In the northern part, rifting occurred in the Korea Plateau that is a continental fragment extended and partially segmented from the Korean Peninsula. Two distinguished rift basins (Onnuri and Bandal Basins) in the Korea Plateau are bounded by major synthetic and smaller antithetic faults, creating wide and considerably symmetric profiles. The large-offset border fault zones of these basins have convex dip slopes and demonstrate a zig-zag arrangement along strike. In contrast, the southern margin is engraved along its length with a single narrow rift basin (Hupo Basin) that is an elongated asymmetric half-graben. Analysis of rift fault patterns suggests that rifting at the Korean margin was primarily controlled by normal faulting resulting from extension rather than strike-slip deformation. Two extension directions for rifting are recognized: the Onnuri and Hupo Basins were rifted in the east-west direction; the Bandal Basin in the east–west and northwest–southeast directions, suggesting two rift stages. We interpret that the east–west direction represents initial rifting at the inner margin; while the Japan Basin widened, rifting propagated southeastward repeatedly from the Japan Basin toward the Korean margin but could not penetrate the strong continental lithosphere of the Korean Shield and changed the direction to the south, resulting in east–west extension to create the rift basins at the Korean margin. The northwest–southeast direction probably represents the direction of rifting orthogonal to the inferred line of breakup along the base of the slope of the Korea Plateau; after breakup the southwestern Japan Arc separated in the southeast direction, indicating a response to tensional tectonics associated with the subduction of the Pacific Plate in the northwest direction. No significant volcanism was involved in initial rifting. In contrast, the inception of sea floor spreading documents a pronounced volcanic phase which appears to reflect asthenospheric upwelling as well as rift-induced convection particularly in the narrow southern margin. We suggest that structural and igneous evolution of the Korean margin, although it is in a back-arc setting, can be explained by the processes occurring at the passive continental margin with magmatism influenced by asthenospheric upwelling.     

Intra-plate seismicity gap along the Median Tectonic Line and oblique plate convergence in southwest Japan

The intra-plate seismicity map for southwest Japan, based on fairly complete historical data for the past four hundred years, reveals an inverse correlation between the seismic activity along the island arc and the slip-rate along the Median Tectonic Line during the Late Quaternary. In the eastern part, the tectonic line is geologically inactive but regional historic seismicity has been high. The intra-plate seismic activity is probably related with the well developed mosaic-like conjugate system of strike-slip faults there. Conversely, the historic seismicity has been low in the western part, especially low in an area along the most geologically active segment of the Median Tectonic Line. Since no creep movement has been found there, energy greater than that of the Mino-Owari earthquake of 1891 (M = 8.0) seems to be stored in this seismicity gap. The difference in seismic released energy between the two regions for the last four hundred years would be balanced by the strain energy accumulated in the seismic gap. The fairly uniform strain release is conformable to the idea, proposed on the basis of the trend of maximum compression axes, that the Philippine Sea plate is dragging southwest Japan southwestward along the Nankai trough.     

南沙海区及邻区构造演化动力学的若干问题

通过南沙海区地球物理资料及围区地质地球物理资料的对比分析,指出南沙海域及邻区中新生代经历晚三叠世碰撞缝合事件及巽他陆块的形成,晚白垩世板块运动重大变格及东亚陆缘的大规模裂谷作用,始新世板块运动重大变革及古南海的消亡,中新世变革事件及南海今日面貌的奠基等四个重要演化阶段。并提出“东亚陆缘超级剪切”动力学模式来概括南沙海区及邻区这新生代构造演化:在特提斯构造域西段(印度部分)、东段(澳大利亚部分)及西太平洋构造域这三大体系的竞争和联合的影响下,东亚陆缘岩石圈交替承受“左行压扭”和“右行张扭”超级剪切应力场的作用,导致南海等边缘海的张开或关闭,以及周边地块的裂离、拼合。     

Passive-margin prolonged volcanism,East Australian Plate: outbursts,progressions, plate controls and suggested causes

Prolonged intraplate volcanism along the 4000 km-long East Australian margin for ca 100 Ma raises many genetic questions. Studies of the age-progressive pulses embedded in general basaltic activity have spawned a host of models. Zircon U–Pb dating of inland Queensland central volcanoes gives a stronger database to consider the structure and origin of Australian age-progressive volcanic chains. This assists appraisal of this volcanism in relation to plate motion and plate margin tectonic models. Inland Queensland central volcanoes progressed south-southeast from 34 to 31 Ma (～5.4 cm/yr) until a surge in activity led to irregular southerly progression 31 to 28 Ma. A new inland southeastern Queensland central volcano line (25 to 22 Ma), from Bunya Mountains to North Main Range, followed 3 Ma behind the adjacent coastal progression. The Australian and Tasman Sea age-progressive chains are compared against recent plate motion modelling (Indian Ocean hotspots). The chain lines differ from general vector traces owing to west-facing swells and cessations in activity. Tectonic processes on the eastern plate margin may regulate these irregularities. These include subduction, rapid roll-back and progressive detachment of the Loyalty slab (43 to 15 Ma). West-flowing Pacific-type asthenosphere, related to perturbed mantle convection, may explain the west-facing volcanic surges. Such westward Pacific flow for over 28 Ma is known at the Australian–Antarctic Discordance, southeast of the present Australian plume sites under Bass Strait–West Tasman Sea. Most basaltic activity along eastern Australia marks asthenospheric melt injections into Tasman rift zone mantle and not lithospheric plate speed. The young (post-10 Ma) fields (Queensland, Victoria–South Australia) reflect new plate couplings, which altered mantle convection and stress regimes. These areas receive asthenospheric inputs from deep thermal zones off northeast Queensland and under Bass Strait.     

关于南海北部特提斯的讨论

南海及邻区处于欧亚大陆与冈瓦纳古陆拼合带的东南端,是特提斯构造域和濒太平洋构造域交汇的重要地区.特提斯缝合带沿金沙江-哀牢山构造带进入南海,人们从而认为南海可能存在特提斯洋遗迹,并认为缝合带存在于磁静区中.本文通过对南海北部陆坡地球物理资料的解释结果,包括重力、磁力、海底地震和深反射地震数据,以及区域地质特征分析,研究了南海北部陆缘高磁异常带和磁静区的成因.结果表明高磁异常带是中白垩世时期古太平洋板块转向俯冲形成的陆缘火山弧,当时存在古俯冲带.磁静区经历了后期大陆边缘张裂和古南海和南海的打开,并经历了高温热物质的底辟作用,使得地壳拉张减薄,居里面抬升形成磁静区.经历了南海的扩张后,原始的俯冲带可能已经向南迁移到南海南部或者已经俯冲消失,其中也不存在缝合带.      

Early Jurassic granitoids from deep drill holes in the East China Sea Basin: implications for the initiation of Palaeo-Pacific tectono-magmatic cycle

The timing of the Palaeo-Pacific Plate (PPP) subduction in East Asia, following the amalgamation of the North and South China Blocks (NCB and SCB), remains equivocal despite several investigations on the widespread subduction-related Mesozoic magmatism in this region. Here we report newly discovered granodiorites in the East China Sea Basin (ECSB) from deep boreholes (2945–2983 m), which yield SHRIMP zircon U–Pb age of 174 ± 1.1 Ma. The rock shows relatively high Sr/Y and La/Yb ratios, low contents of Ni, Cr, and MgO, and markedly negative values of εHf(t) (21.0 to ?27.0). These geochemical and isotopic features are similar to those of the tonalite-trondhjemite-granodiorite (TTG) suites produced by the partial melting of the thickened lower continental crust. Our data, together with the ca. 190–180 Ma I-type granites reported from the eastern Zhejiang–Fujian and Taiwan areas, lead us to conclude that the continental crust in the coastal areas of South China underwent some degree of thickening during the Early Jurassic. A comparison with the coeval magmatic rocks in South Korea and Japan suggests that a large NE-trending continental arc (ca. 190–170 Ma) might have been constructed along the eastern margin of Asia at this time. Our study provides insights into the initiation of the Palaeo-Pacific tectono-magmatic cycle immediately following the consolidation of the SCB and NCB.     

Seismic evidence of divergent rifting and subsequent deformation in the southern Japan Sea, and a Cenozoic tectonic synthesis of the eastern Eurasian margin

Neogene rift system configuration for the back-arc of southwest Japan, southern rim of the Japan Sea, is argued on the basis of reflection seismic interpretation. Divergent rifting and subsequent contraction provoked by an arc–arc collisional event are manifested by the formation of faulted grabens and their inverted deformation, respectively. We identified the following four Cenozoic tectonic epochs as a decomposition process of the eastern Eurasian margin based on reliable paleomagnetic data: (1) Plate margin rearrangement on a regional left-lateral fault through southwest Japan and Sikhote Alin, which constituted a continuous geologic province before the early Tertiary differential motion; (2) Early Tertiary clockwise rotation (>20°) of the east Tan-Lu block relative to the North China block; (3) Oligocene to early Miocene divergent rifting and spreading of the Japan Sea, which divided southwest Japan from the east Tan-Lu block; (4) Middle Miocene bending and back-arc inversion of southwest Japan caused by collision with the Izu-Bonin arc. According to the estimation of relative motions during these events, a paleogeographic reconstruction is presented through Cenozoic time.     

A study of microearthquake seismicity and focal mechanisms within the Sea of Marmara (NW Turkey) using ocean bottom seismometers (OBSs)

We have carried out seismological observations within the Sea of Marmara (NW Turkey) in order to investigate the seismicity induced after Gölcük–İzmit (Kocaeli) earthquake (M_w 7.4) of August 17, 1999, using ocean bottom seismometers (OBSs). High-resolution hypocenters and focal mechanisms of microearthquakes have been investigated during this Marmara Sea OBS project involving deployment of 10 OBSs within the Çınarcık (eastern Marmara Sea) and Central-Tekirdağ (western Marmara Sea) basins during April–July 2000. Little was known about microearthquake activity and their source mechanisms in the Marmara Sea. We have detected numerous microearthquakes within the main basins of the Sea of Marmara along the imaged strands of the North Anatolian Fault (NAF). We obtained more than 350 well-constrained hypocenters and nine composite focal mechanisms during 70 days of observation. Microseismicity mainly occurred along the Main Marmara Fault (MMF) in the Marmara Sea. There are a few events along the Southern Shelf. Seismic activity along the Main Marmara Fault is quite high, and focal depth distribution was shallower than 20 km along the western part of this fault, and shallower than 15 km along its eastern part. From high-resolution relative relocation studies of some of the microearthquake clusters, we suggest that the western Main Marmara Fault is subvertical and the eastern Main Marmara Fault dips to south at 45°. Composite focal mechanisms show a strike-slip regime on the western Main Marmara Fault and complex faulting (strike-slip and normal faulting) on the eastern Main Marmara Fault.     

Conceptual model and numerical simulation of the hydrothermal system in Hammam Faraun hot spring, Sinai Peninsula, Egypt

The tectonic position of Egypt in the northeastern corner of the African continent suggests that it may possess significant geothermal resources, especially along its eastern margin. The most of the thermal springs in Egypt are located along the shores of Gulf of Suez and Red Sea. These springs are probably tectonic or nonvolcanic origin associated with the opening of the Red Sea—Gulf of Suez rifts, where the eastern shore of the Gulf of Suez is characterized by superficial thermal manifestations including a cluster of hot springs with varied temperatures. Hammam Faraun area consists of the hottest spring in Egypt where the water temperature is 70°C. Conceptual as well as numerical models were made on the Hammam Faraun hot spring based on geological, geochemical, and geophysical data. The models show that the heat source of the hot spring is probably derived from high heat flow and deep water circulation controlled by faults associated with the opening of the Red Sea and Gulf of Suez rifts.     

Shallow-focus seismicity and tectonic structure of the Sea of Japan

The analysis of the available seismological data on the Sea of Japan region made it possible to prepare the first complete unified catalog of earthquakes with M ? 3.0 and h ? 60 km for the period of 1975–2010. Four maps of epicenters for different depth intervals (0–10, 11–20, 21–30, and 31–60 km) and three sublatitudinal sections 1° wide are constructed. The analysis includes the structural features and the probable tectonic nature of the seismoactive zone along the underwater margin or borderland of the Japan-Sakhalin island arc: the regional or, more exactly, megaduplex of compression faults determined by the crust sliding in the back part of the frontal deep-seated thrust. The crustal seismicity in the southeastern margin of the Korean Peninsula (the Sino-Korean Shield) is likely related to the Tsushima and Ullyndo faults. It is assumed that it may provoke block, potentially thsunamigenic landslides in the southern and eastern cirques of the Ullyndo Basin incised into the underwater delta of the Huanghe River.     

Ophiolites from the Mianlue Suture in the Southern Qinling and Their Relationship with the Eastern Paleotethys Evolution

The Mianlue suture extends from Derni-Nanping-Pipasi-Kangxian to the Lueyang-Mianxian area, then traverses the Bashan arcuate structure eastward to the Huashan region, and finally to the Qingshuihe area of the southern Dabie Mountains. From east to west, with a length of over 1500 km, the ophiolitic melange associations are distributed discontinuously along the suture. The rock assemblages include ophiolite, island-arc and oceanic island rock series, indicating that there existed a suture zone and a vanished paleo-ocean basin. The Mianliie paleo-ocean basin experienced its main expansion and formation process during the Carboniferous-Permian and closed totally in the Triassic. It belongs to the northern branch of the eastern paleotethys, separated from the northern margin of the Yangtze block under the paleotethys mantle dynamic system.     

Crustal structure and transform margin development south of Svalbard based on ocean bottom seismometer data

The Barents Sea is located in the northwestern corner of the Eurasian continent, where the crustal terrain was assembled in the Caledonian orogeny during Late Ordovician and Silurian times. The western Barents Sea margin developed primarily as a transform margin during the early Tertiary. In the northwestern part south of Svalbard, multichannel reflection seismic lines have poor resolution below the Permian sequence, and the early post-orogenic development is not well known here. In 1998, an ocean bottom seismometer (OBS) survey was collected southwest to southeast of the Svalbard archipelago. One profile was shot across the continental transform margin south of Svalbard, which is presented here. P-wave modeling of the OBS profile indicates a Caledonian suture in the continental basement south of Svalbard, also proposed previously based on a deep seismic reflection line coincident with the OBS profile. The suture zone is associated with a small crustal root and westward dipping mantle reflectivity, and it marks a boundary between two different crystalline basement terrains. The western terrain has low (6.2–6.45 km s⁻¹) P-wave velocities, while the eastern has higher (6.3–6.9 km s⁻¹) velocities. Gravity modeling agrees with this, as an increased density is needed in the eastern block. The S-wave data predict a quartz-rich lithology compatible with felsic gneiss to granite within and west of the suture zone, and an intermediate lithological composition to the east. A geological model assuming westward dipping Caledonian subduction and collision can explain the missing lower crust in the western block by subduction erosion of the lower crust, as well as the observed structuring. Due to the transform margin setting, the tectonic thinning of the continental block during opening of the Norwegian-Greenland Sea is restricted to the outer 35 km of the continental block, and the continent–ocean boundary (COB) can be located to within 5 km in our data. Distinct from the outer high commonly observed on transform margins, the upper part of the continental crust at the margin is dominated by two large, rotated down-faulted blocks with throws of 2–3 km on each fault, apparently formed during the transform margin development. Analysis of the gravity field shows that these faults probably merge to one single fault to the south of our profile, and that the downfaulting dominates the whole margin segment from Spitsbergen to Bjørnøya. South of Bjørnøya, the faulting leaves the continental margin to terminate as a graben 75 km south of the island. Adjacent to the continental margin, there is no clear oceanic layer 2 seismic signature. However, the top basement velocity of 6.55 km s⁻¹ is significantly lower than the high (7 km s⁻¹) velocity reported earlier from expanding spread profiles (ESPs), and we interpret the velocity structure of the oceanic crust to be a result of a development induced by the 7–8-km-thick sedimentary overburden.     

再论台湾造山带构造格架与演化过程SCIEI北大核心CSCD

台湾造山带是中新世晚期以来相邻菲律宾海板块往北西方向移动,导致北吕宋岛弧系统及弧前增生楔与欧亚大陆边缘斜碰撞形成的。目前该造山带仍在活动,虽然规模很小,但形成了多数大型碰撞造山带中的所有构造单元,是研究年轻造山系统的理想野外实验室,为理解西太平洋弧-陆碰撞过程和边缘海演化提供了一个独特的窗口。本文总结了二十一世纪以来对台湾造山带的诸多研究进展,讨论了其构造单元划分及演化过程。我们将台湾造山带重新划分为6个构造单元,由西至东分依次为:(1)西部前陆盆地;(2)中央山脉褶皱逆冲带;(3)太鲁阁带;(4)玉里-利吉蛇绿混杂岩带;(5)纵谷磨拉石盆地;(6)海岸山脉岛弧系统。其中,西部前陆盆地为6.5Ma以来伴随台湾造山带的隆升剥蚀形成沉积盆地。中央山脉褶皱逆冲带为新生代(57~5.3Ma)欧亚大陆东缘伸展盆地沉积物由于弧-陆碰撞受褶皱、逆冲及变质作用改造形成的。太鲁阁带是造山带中的古老陆块,主要记录中生代古太平洋俯冲在欧亚大陆活动边缘形成的岩浆、沉积和变质岩作用。玉里-利吉蛇绿混杂岩带和海岸山脉岛弧系统分别为中新世中期(~18Ma)以来南中国海板块向菲律宾海板块之下俯冲形成的岛弧和弧前增生楔,其中玉里混杂岩中有典型低温高压变质作用记录,变质年龄为11~9Ma;岛弧火山作用的主要时限为9.2~4.2Ma。纵谷磨拉石盆地记录1.1Ma以来的山间盆地沉积。台湾造山带的构造演化可划分为4个阶段:(a)古太平洋板块俯冲与欧亚大陆边缘增生阶段(200~60Ma);(b)欧亚大陆东缘伸展和南中国海扩张阶段(60~18Ma);(c)南中国海俯冲阶段(18~4Ma);(d)弧-陆碰撞阶段(<6Ma)。台湾弧-陆碰撞造山带是一个特殊案例,其弧-陆碰撞并不伴随着弧-陆之间的洋盆消亡,而是由于北吕宋岛弧及弧前增生楔伴随菲律宾海板块运动向西北方走滑,仰冲到欧亚大陆边缘,形成现今的台湾造山带。     

西太平洋边缘海盆地的扩张过程和动力学背景

西太平洋集中发育了全球 75%的边缘海盆地 ,这些盆地形成于始新世、渐新世—中新世和晚中新世—第四纪 3个边缘海扩张幕。文中介绍了边缘海盆地的基本特征和发育模式 ,详细讨论了西北太平洋边缘海盆地周缘板块构造时空格架及其对边缘海盆地形成、演化和关闭过程的控制作用。太平洋板块的俯冲及俯冲带的后退 ,印度—亚洲大陆碰撞的远程效应以及澳洲与印度尼西亚的碰撞是边缘海盆地的 3个重要的区域性控制因素。印度—亚洲大陆的碰撞所形成的向东和东南的地幔流可能推动了东亚大陆东侧和南侧俯冲带的后退 ,并引发弧后扩张作用。同时 ,由这一碰撞引起的东亚大陆边缘NE或NNE向断裂的右旋走滑 ,进一步影响和控制了边缘海盆地的几何学特征及演化。澳大利亚和印度尼西亚的碰撞阻碍了俯冲带的后退 ,导致了南海、Sulu海和Celebes海盆地的扩张终止。同时这一碰撞推动菲律宾海板块向北运移 ,并使Bonin弧与中央日本碰撞 ,导致日本海关闭     

Kinematic analysis of sinistral cataclastic shear zones along the northern margin of the Mino Belt, central Japan

In this paper, cataclastic shear zones along the northern margin of the Mino Belt, central Japan are described, and the significance of the shearing in the tectonic evolution of SW Japan is examined. The Mino Belt in SW Japan is composed of accretionary complexes of Jurassic to Early Cretaceous age. Field investigation revealed that remarkable cataclastic shear zones trending east to northeast run along the northern margin of the Mino Belt. Closely spaced cleavage is developed in these shear zones. Lineation on the cleavage plunges at shallow to moderate angles. Deformation structures (e.g. composite planar fabric and asymmetric structure of clasts) in the sheared rocks clearly indicate a sinistral sense of shear. The shearing ceased by latest Cretaceous time, because the sheared rocks are overlain by unsheared Upper Cretaceous volcanic rocks. The sinistral shearing may be closely related to Cretaceous sinistral movement along the eastern margin of Asia. Sinistral shearing along the northern margin of the Mino Belt can be considered as a key for re-examining the tectonic development of SW Japan.