大别山东缘郯庐断裂带早期韧性剪切带的形成温度

年龄的解释强烈依靠于构造热事件的发生温度和矿物的封闭温度,在缺少构造热事件的温度资料的情况下,很难对年龄数据做出正确合理的解释.利用白云母-绿泥石地质温度计,计算了大别山东缘郯庐早期左旋走滑韧性剪切带的形成温度,获得了350～450℃的温度区间,并且多数温度值位于430～450℃之间.该温度值大于40Ar/39Ar法中自云母的封闭温度,从而由主要以残斑形式存在的白云母获得的年龄值记录了郯庐断裂带的活动时间,190 Ma左右的白云母年龄值为接近于韧性剪切带变形年龄的冷却年龄.并由此年龄和温度数据得出郯庐断裂带形成于大别造山带造山作用后期.该韧性剪切带形成温度明显低于所叠加的造山带高角闪岩相变质岩,也指示为造山后期走滑运动的结果.     

郯庐断裂南段韧性剪切带糜棱岩中纳米级颗粒的发现

在对郯庐断裂带南段安徽巢县寨山地区韧性断裂形成时限研究过程中,选取韧性剪切带糜棱岩中的重结晶石英进行透射电镜(中国科技大学结构成分分析中心,TEM型号HITACHI,H-800)观察,发现一部分石英中存在纳米级的颗粒,对于韧性剪切带糜棱岩中石英来说,这尚属首次发现。     

郯庐断裂带形成演化的年代学研究

通过对郯庐断裂带东侧张八岭蓝片岩带内白云母＾４０Ａｒ－＾３９Ａｒ年龄、断裂带内片麻状花岗岩中钾长石＾４０Ａｒ－＾３９Ａｒ年龄以及断裂带内断层泥Ｋ－Ａｒ、ＥＳＲ年龄的测定,并结合有关的地质和古地磁资料,厘定了籽庐断裂带形成和演化的过程：（１）三叠纪（２４４～２０９Ｍａ）由于华北与扬子地块碰撞,郯庐断裂带形成为其主要左行平稳时期;（２）侏罗纪（１８９～１６４Ｍａ）时郯庐断裂东侧下扬子地块可能经历了逆时     

安徽肥东西韦地区郯庐断裂带的构造特征与变形规律

郯庐断裂带南段安徽肥东西韦地区糜棱岩广泛发育,地表出露良好。通过对该地区进行细致的宏观和微观分析研究发现,韧性剪切带具有典型的左行平移特征;断裂带的持续走滑使糜棱岩带抬升并在浅层形成正花状构造;新生代以来由于太平洋板块近EW向的强烈挤压,左行平移逆断层形成,并叠加于早期构造之上,从而形成当今地表所见的构造特征。     

郯庐断裂带中生代火山活动与深部过程

郯庐断裂带中生代火山活动主要发生在早白垩世 ,形成了一套以橄榄安粗岩系为主的火山岩。火山岩岩石化学特征、地球化学特征与断裂带外明显不同 ,以富碱富钾、富轻稀土元素为特征 ,具有较高的 ISr值和明显偏低的εNd值 ,表明火山活动不仅与地壳混染有关 ,而且与深部地幔以及断裂带的演化有密切的关系。研究显示该区岩浆起源于地幔底侵、壳幔相互作用下的壳幔过渡带 ,也反映此时的断裂带切入到壳幔边界。     

郯庐断裂带早白垩世岩浆活动与断裂带的活动关系

文章通过收集晚中生代时期郯庐断裂带中南段出露的糜棱岩、火山岩和侵入岩样品的同位素年代学数据,结合区域构造应力场、断陷盆地和伸展活动时间等多方面的证据,显示了早白垩世初郯庐断裂带再次发生左行平移,之后迅速转为伸展运动,并伴随发生了大规模的岩浆岩喷发事件.与华北克拉通内部相比,断裂带内具有相对较长的演化历史和减薄程度,暗示了郯庐断裂带有着比克拉通内部更加强烈的伸展运动,为岩石圈的强烈减薄及大规模岩浆活动的发生提供了有利的条件.     

肥东低角度韧性剪切带内岩石变形特征

肥东低角度韧性剪切带紧邻郯庐断裂带巨大的近直立的左行平移韧性剪切带发育,其岩石变质变形特征具有韧性剪切带的一般特征,即越靠近剪切带内侧,岩石变质变形程度越强,远离韧性剪切带,岩石变质变形强度越弱。低角度韧性剪切带内超糜棱岩变形强烈,变质相可达到角闪岩相,其变质变形程度与直立的郯庐断裂带内超糜棱变质变形程度类似,两者在形成环境和成因类型上统一,具有大陆岩石圈被高角度韧性剪切带切割并沿低角度韧性剪切带逆冲推覆的形成机制。     

渤海海域郯庐断裂带构造解析

通过对渤海海域的地震资料及地质资料进行综合分析,认为郯庐断裂带在该地区的宽度为50 km,并分为东支和西支。以张家口—蓬莱断裂为界,渤海海域的郯庐断裂带分为南段和北段,南段东、西两支断裂的走滑特征非常明显;北段的东支走滑特征明显,而西支走滑特征不明显。古近纪,北段东支和西支都具有走滑运动,但是由于张家口—蓬莱断裂左旋切割,导致西支走滑受阻而被废弃,因此走滑运动主要集中在东支。     

郯庐断裂带南段巨型正花状构造的发现及地质意义

根据地球物理资料，郯庐断裂带(与合肥盆地接触的部分)平面上是一个破碎带，宽度约22km，断裂带内地层与两侧的下扬子陆块、华北陆块的地震反射特征和电性特征均存在较大差异，郯庐断裂带具有明显的分界特征．在横剖面上郯庐断裂带显示正花状构造，由一条走滑主断裂和几条平行的伴生断裂组成，其中主断裂断面直立，一直延伸到地下15km深处，仍未见消失或变缓的趋势，是压扭性断裂的典型特征。     

郯庐断裂带演化动力学——多力源多时期分段作用模式

提出了郯庐断裂带的演化动力学--多力源多时期分段作用模式.早-中侏罗世,扬子与华北地块碰撞后的持续会聚力、古太平洋板块的挤压力(安第斯型)联合作用于郯庐断裂带,产生了左旋压扭活动.晚侏罗世,西太平洋型的古太平洋板块挤压力作用机制率先作用于中国大陆边缘的北部地区,并一直持续到古近纪.其在郯庐断裂带中、北段诱发出上地幔上涌力,使其产生了右旋拉张活动;郯庐断裂带南段直至晚白垩世才受到这种机制作用.晚新生代以来,西太平洋俯冲带后退,上地幔上涌力作用已退到边缘海地区,郯庐断裂带全段受到边缘海地区上地幔上涌力诱发的次级挤压作用力,形成了右旋挤压活动.     

郯庐断裂带同造山期活动的前陆沉积证据

对大别山高压-超高压变质岩剥露地表的时间以及前陆盆地对郯庐断裂带起源的指示等重要问题进行了探讨。前陆盆地上三叠统至下-中侏罗统砂岩的端元组分分析结果指示了前陆盆地的物源区为大别造山带。砂岩成熟度从近断裂带处的1.54左右变化为远离断裂带处的5.4左右,反映了前陆沉积盆地中黄马青群及象山群应是直接来自大别造山带的原地沉积,也说明郯庐断裂带在晚三叠世时可能已经存在于大别山东缘。伊利石的结晶度多数介于0.24°~0.39°(Δ2θ),多型为2M型和1M 2M1型,指示了当时前陆沉积的热演化温度为190~320℃,从而反映了前陆沉积的最大原始埋深约为10 000 m。     

The large-scale ductile shear zone in Kuda, western Kunlun

A set of metamorphic suites, previously known as the Precambrian metamorphic basement in Kuda, western Kunlun has been determined as a large nappe ductile shear zone which develops penetrative foliation, oriented stretching lineation, various but consistent kinematic indicators of thrusting from north to south. The microstructure and the supermicrostructure also display the ductile deformation characteristics, and the paleotectonic differential stress is obtained. The metamorphic age is 426–451 Ma dated by⁴⁰Ar/³⁹Ar method. According to tectonic background, it is a product of early Paleozoic accretionary wedge orogenesis in western Kunlun.     

郯庐断裂带渤海段的深部构造与动力学意义

郯庐断裂带渤海段的3条大地电磁测深剖面,揭示了断裂带丰富的深部结构信息。这些剖面显示,郯庐断裂带已切穿了整个地壳,并且向下延入上地幔;该段断裂带在深部显示为陡立的走滑构造,浅部为伸展断层及断陷盆地所叠加,最后又发生过一期明显的逆冲活动;该断裂带的走滑构造在渤海湾内继续存在,指示其早期的走滑活动中向北延入了渤海内;该断裂带内部及其旁侧,浅部的断陷盆地发育与深部的高导层(带)紧密伴生,反映断陷盆地发生时在地壳深部都出现了软弱拆离带,也指示了岩石圈减薄中地壳内所发生的深部过程。     

Evolution of the Xiaotian-Mozitan fault and its implications for exhumation of Dabie HP-UHP rocks

The Xiaotian-Mozitan fault (XMF) located north of Dabie orogenic belt separates the North Dabie complex to the south from the Beihuaiyang low-grade metamorphic rocks to the north. It comprises several NW-striking ductile shear zones and brittle faults. The brittle faults obviously overprinted on the ductile shear zones and promoted the development of the volcanic basins in early Cretaceous to the north, which suggests that the brittle faults were normal faults formed in early Cretaceous during doming of Dabie orogenic belt. The ductile shear zone superposed on the north Dabie grey gneiss, and it is an important channel where the Dabie HP-UHP rocks exhumed. For obtaining new structural constraint on exhumation of the HP-UHP rocks, we present here experimental results on the microstructure, quartz C-axis fabrics and the microprobe analyses of phengite. The ductile shear zone was determined to be formed at temperature of 600-650℃ and pressure of 1.1 GPa by the mineral deformation, microprobe analyses and geobarometry of Si-in-phengite of the mylonite, the results suggest that the mylonite now exposed on the surface experienced an upper amphibolite-facies metamorphism in the lower crust. The mineral stretching lineation varies from horizontal in the east segment to sub-dip in the west. Shear sense indicators from outcrop and thin sections of orientated specimen and quartz C-axis fabrics suggest that the XMF is a sinistral normal fault. The kinematics analysis of the ductile shear zone indicates that the exhumation of Dabie HP-UHP rocks is the results of a SE-directed extrusion and an anticlockwise rotation around its eastern pivot simultaneously.     

合肥盆地对郯庐断裂带同造山走滑活动的沉积响应

夹持于郯庐断裂带与大别造山带之间的合肥盆地,前侏罗纪基底上的印支期前陆逆冲断层靠近郯庐断裂带显著增多,指示了该断裂带印支期的活动。盆地内侏罗系地层在郯庐断裂带一侧出现了边缘相,并且发育了与断裂带平行的沉积中心,反映当时郯庐断裂带已出现在合肥盆地的东侧,构成了盆地东部边界,因走滑而隆升的张八岭带构成了盆地东部的物源区。位于大别造山带东缘的郯庐早期走滑糜棱岩中3个白云母的40A r/39A r坪年龄分别为(192.5±0.7)M a、(189.7±0.6)M a、(188.7±0.7)M a,代表了同造山期走滑的冷却年龄。这一系列现象表明,郯庐断裂带起源于华北与华南板块印支期的陆—陆碰撞,推断是以转换断层的型式出现。该断裂带早白垩世的左行平移是滨太平洋构造运动中的再次活动。     

Structural deformation and fault activity of the Tan-Lu Fault zone in the Bohai Sea since the late Pleistocene

The Tan-Lu Fault zone (TLFZ) is a significant fractural zone in eastern China and also a seismicity belt in North China. Based on total 4000-km-long shallow penetrated single seismic data with high-resolution, structural deformation and fault activity of the TLFZ in the Bohai Sea since the late Pleistocene are discussed in detail. The results show that the TLFZ with a discontinuous distribution and a general NNE-trending consists of 14 active subfaults with an NNE or NE strike in the Bohai Sea. Seismic data reveal that de-formation zones along the subfaults in the central Bohai Sea and the Laizhou Bay are wider and more complex than those in the Liaodong Gulf. Related folds and lots of secondary normal faults which are characterized by nearly vertical fault planes and a same or reverse dip construct the fractural zone in the Laizhou Bay and the central Bohai Sea. Usually, micro symmetrical grabens develop on the top of anticlines. In the Liaodong Gulf, subfault fractural zones usually consist of secondary normal faults with the same inclination or opposite inclination. Ages of seismic sequences and cutting relation between subfaults and seismic sequences suggest that the latest faulting age of the TLFZ is the end of the late Pleistocene in the Liaodong Gulf and the early Holocene in the Laizhou Bay and the central Bohai Sea. There is a good match between distribution of earthquakes and that of the subfaults in the Laizhou Bay and the central Bohai. Statistical result shows that total vertical offset of the TLFZ since the late Pleistocene ranges from 6 to 11 m. On the basis of offsets of the subfaults, the vertical slip rate is calculated and results show that average vertical slip rates in the central Bohai Sea are larger than those in the Liaodong Gulf and the Laizhou Bay. Slip rates more than 0.06 mm/a during 23–10 ka B.P. and 85–65 ka B.P. are larger than those in other stages. The TLFZ was mainly dominated by tensional normal component since the late Pleistocene. Synthesizing shallow deformation, activity and distribution of earthquakes, the TLFZ in the Bohai Sea can be divided into three segments: the Laizhou-Bay segment, the Bozhong segment, and the Liaodong-Gulf segment.     

The white schist assemblage in the kyanite quartzite from the ultrahigh-pressure metamorphic belt, eastern Dabie Mountains

The kyanite quartzite from the ultrahigh-pressure metamorphic belt in the eastern Dabie Mountains is composed mainly of quartz, kyanite, talc and epidote, which contains a typical mineral assemblage of white schist. It suffered an eclogite facies metamorphism of P =(2 4±0 3) GPa and T =630℃ together with coexisting eclogite. The protolith may be an aplite replaced by high-pressure fluid of eclogite facies.     

Quartz and clinoenstatite exsolutions in clinopyroxene of garnet-pyroxenolite from the North Dabie Mountains, eastern China

The exsolution lamellae of quartz and clinoen-statite are idenfied in diopside of garnet-pyroxenolite from the North Dabie Mountain by transmission electron microscopy, which is interpreted that the lamellae are originally exsolved from a former ultra-high-pressure clinopyroxene due to decreasing of pressure. Study of petrography shows that there is compositional zoning hi the diopside itself. It is implied that the garnet-pyroxenolite had undergone intensive high-temperature granulite fades and high-amphibolitic fades retrogressive metamorphism, while the peridotite (the garnet-pyroxenolite's host rock) emplaced the crust