地震剖面中走滑断层旋向判断模型——以塔东阿拉干北断层为例

地震剖面解释中尚无走滑断层旋向的直接判别标志,本文提出了一个在地震剖面解释中直接判断走滑断层旋向的模型。该模型假定断层作用前既存的某个地层厚度有变化,则垂直或斜交地层厚度变化方向的走滑断层必定在穿过断层的地震剖面中两盘地层厚度不等。确定了地层厚度变化方向,又测定了剖面中两盘地层厚度,则走滑断层的旋向就可以唯一地确定下来。穿过塔里木盆地东部阿拉干北右行走滑断层的地震剖面资料证实了这一模型的适用性。     

SHRIMP zircon and EPMA monazite dating of granitic rocks from the Maizuru terrane, southwest Japan: Correlation with East Asian Paleozoic terranes and geological implications

Abstract The Maizuru terrane, distributed in the Inner Zone of southwest Japan, is divided into three subzones (Northern, Central and Southern), each with distinct lithological associations. In clear contrast with the Southern zone consisting of the Yakuno ophiolite, the Northern zone is subdivided into the western and eastern bodies by a high-angle fault, recognized mainly by the presence of deformed granitic rocks and pelitic gneiss. This association suggests an affinity with a mature continental block; this is supported by the mode of occurrence, and petrological and isotopic data. Newly obtained sensitive high mass-resolution ion microprobe (SHRIMP) zircon U–Pb ages reveal the intrusion ages of 424 ± 16 and 405 ± 18 Ma (Siluro–Devonian) for the granites from the western body, and 249 ± 10 and 243 ± 19 Ma (Permo–Triassic) for the granodiorites from the eastern body. The granites in the western body also show inherited zircon ages of around 580 and 765 Ma. In addition, electron probe microanalysis (EPMA) monazite U–Th–total Pb dating gives around 475–460 Ma. The age of intrusion, inherited ages, mode of occurrence, and geological setting of the Siluro–Devonian granites of the Northern zone all show similarities with those of the Khanka Massif, southern Primoye, Russia, and the Hikami granitic rocks of the South Kitakami terrane, Northeast Japan. We propose that both the Siluro–Devonian and Permo–Triassic granitic rocks of the Northern zone are likely to have been juxtaposed through the Triassic–Late Jurassic dextral strike-slip movement, and to have originated from the Khanka Massif and the Hida terrane, respectively. This study strongly supports the importance of the strike-slip movement as a mechanism causing the structural rearrangement of the Paleozoic–Mesozoic terranes in the Japanese Islands, as well as in East Asia.     

大别山北麓梅山群中韧性剪切带变形特征及形成机制

梅山群为分布于北淮阳地区位于佛子岭群之下、逆掩于晚泥盆世—石炭纪杨山煤系和中侏罗统红层之上的一套中—浅变质岩系，在其中、上部发育ＮＷ走向的韧性剪切带，产状与区域片理一致。对韧性剪切带及其变形岩石———糜棱岩的宏微观构造研究表明，韧性剪切变形发生于区域变质岩形成之后，具有右旋剪切的运动特点，反映大别山地块向北仰冲过程中所派生的侧向滑移作用     

Structural,Kinematic and Geochronological Study of the Main Tianshan Shear Zone in the Borohoro Ranges,NW China

The western segment of the Main Tianshan shear zone (MTSZ) branches into three major dextral strike-slip shear zones in the Borohoro Ranges, northwestern China. Mylonitic rocks within these zones exhibit vertical foliations, subhorizontal lineations, and dextral kinematics. The microstructures and CPO patterns of calcite and quartz in the tectonites suggest shearing at temperatures of 200°C to 500°C or above. The amount of dextral displacement along the zones is less than 100 km. LA-ICP-MS U-Pb dating of zircons from some pre-kinematic granites gave ages of 364–325 Ma and 316 Ma, and zircons from a syn-kinematic leucogranite gave an age of 291 Ma. We propose that dextral shearing along the MTSZ started in the earliest Permian. Our data indicate that collision between the Yili and Junggar plates might have finished before 325 Ma or 316 Ma, with a tectonic transformation from 325 Ma to 300 Ma, resulting in intracontinental transpression from 300 Ma or 291 Ma. We suggest that the formation of the Kazakhstan orocline (KO) took place in two stages, with the early stage of bending driven by convergence related to oblique subduction, and the late stage possibly associated with lateral disarticulation as a result of the dextral strike-slip shear zones.     

营潍断裂带结构特征及其与相邻盆地的关系

营滩断裂带是渤海湾盆地东部重要的边界条件,对油气地质条件具有重要影响。依据大量实际地震资料,将营潍断裂带划分为三段,即潍坊-莱州湾-黄河口段、渤东低凸起段和辽东凸起段,各段在断裂走向、结构及组成等方面具有较大的差异。结合区域应力分析和新生代盆地盖层构造变形特征,认为营潍断裂带在新生代的活动具有明显的差异性,以伸展、右旋走滑活动为主,大致可分为三个时期,即古新世-早始新世、中始新世-渐新世、新近纪-第四纪。在此基础上,探讨了营潍断裂带与相邻新生代盆地的关系,并根据结构样式将相邻盆地划分为五种类型。     

中天山北缘大型右旋走滑韧剪带研究

中天山北缘是一个近 EW向的大型右旋走滑韧剪带。宏、微观构造尺度的运动学研究表明 ,该带经历过至少二期韧性变形作用。第一期为从南向北的逆冲推覆韧剪变形 ,时代为中—晚志留世 ,以米什沟剖面为代表 ,对应于早古生代洋壳从北向南俯冲及稍后吐哈陆块朝中天山岛弧的碰撞事件。第二期为沿 EW方向的右旋走滑韧性变形 ,其构造形迹广泛分布于中天山北缘带各个地段 ;北天山石炭纪火山岩已卷入该期构造活动 ,走滑时代为晚石炭世—早二叠世 ,对应于晚石炭世塔里木与西伯利亚两大板块碰撞造山诱发的陆内变形、走滑剪切。走滑带中新生白云母 4 0 Ar/39Ar年龄为 ( 2 69± 5) Ma。剪切面理、拉伸线理、矿物韧剪构造、石英 C轴组构提供了构造运动学证据 ;地层不整合及同位素测年值提供了变形时间证据。二叠纪以后的构造事件也影响到中天山北缘带 ,但只有脆性变形形迹 ,无韧性剪切。最后对本区古生代构造演化进行了讨论     

Stratigraphy and structure of Devonian fluvial sediments,western Beara Peninsula,south-west Ireland

A stratigraphic and structural summary of 5 km of Upper Devonian strata of south-west Beara, part of the Munster Basin, south-west Cork is presented. Five formations are recognized on the basis of lithofacies geometries and associations. The lowest Caherkeen Formation comprises rapidly alternating sheet-like, plane-bedded, low-angle, cross-bedded sandstones and laminated, rippled or desiccated mudrocks. The incoming of thin lenticular sandstone packages, commonly with high-angle cross-bedding, distinguishes the overlying Eagle Hill Formation. The succeeding Reen Point Formation comprises thicker bedsets of plane-bedded, low-angle and high-angle cross-bedded sandstones, separated by thick, massive mudrocks. Intraformational breccias and calcareous nodular siltrocks are distinctive features. The Tholane Formation is characterized by thick massive red-green mudrocks and a general absence of coarser grained lithologies. This sequence was deposited in a terminal fluvial fan in a basin characterized by decreasing subsidence rates and gradient with time. The overlying Toe Head Formation represents the deposits of a fluvial coastal plain. It has siltrocks that are predominantly green, often with preserved fish and plant debris. There is a relative absence of high-angled cross-bedded sandstones and an abundance of flat-laminated and inclined parallel-laminated sandstones. The structure of the Beara Peninsula comprises a WSW plunging anticlinorium with a single cleavage formed during the Variscan orogeny. Evidence from locally transecting cleavages and from mapping indicates dextral transpression. Development of the three main fault trends was contemporaneous with the folding. The well-known copper mineralization of the Allihies area is associated with east-west fault trends, a pattern observed elsewhere in the western Munster Basin. Basement involvement during both basin development and deformation is likely, but is difficult to test.     

Geological analysis and FT dating of the large-scale risht-lateral strike-slip movement of the Red River fault zone

Tectonically,the large-scale right-lateral strike-slip movement along the Red River fault zone is characterized at its late phase with the southeastward extension and deformation of the Northwestern Yunnan normal fault depression on its northern segment,and the dextral shear displacement on its central-southern segment.Research of the relations between stratum deformation and fault movement on the typical fault segments,such as Jianchuan,southeast Midu,Yuanjiang River,Yuanyang,etc.since the Miocene Epoch shows that there are two times dextral faulting dominated by normal shearing occurring along the Red River fault zone since the Miocene Epoch.The fission track dating (abbreviated to FT dating,the same below) is conducted on apatite samples collected from the above fault segments and relating to these movements.Based on the measured single grain's age and the confined track length,we choose the Laslet annealing model to retrieve the thermal history of the samples,and the results show that the fault zone experienced two times obvious shear displacement,one in 5.5 ±1.5 MaBP and the other in 2.1±0.8 MaBP.The central-southern segment sees two intensive uplifts of mountain mass in the Yuanjiang River-Yuanyang region at 3.6-3.8 MaBP and 1.6-2.3 MaBP,which correspond to the above-mentioned two dextral normal displacement events since the late Miocene Epoch.     

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     

CENOZOIC LARGE-SCALE STRIKE-SLIP FAULT IN WEST YUNNAN, CHINA

CENOZOIC LARGE-SCALE STRIKE-SLIP FAULT IN WEST YUNNAN, CHINA1　ZhongDalaiTapponnierP ,WuHaiwei,etal.Large scalesstrikeslipfault:themajorstructureofintracontinentaldeformationaftercollision[J] .ChineseScienceBulletin ,1990 ,35:77～ 97. 2　TapponnierP ,LacassinR ,LeloupPH ,etal.TheAilaoShan/RedRivermetamorphicbelt:tertiaryleft lateralshearbetweenIndochinaandSouthChina[J] .Nature,1990 ,343:4 31～ 4 37. 3　LiKang ,ZhongDalai.Themicrostructurecharacteristicso…