中国东北地区古生代构造单元:地块还是造山带?

华北克拉通以北的中国东北地区古生代构造单元是地块还是造山带,是地质界近年争论的重要地质构造问题.通过对已有资料的综合研究,简要总结和讨论了各个"地块区"的地质特征,认为这些所谓的地块中,额尔古纳是新元古代晚期至古生代初期存在的地块,从寒武纪开始转变为造山带;其余所谓的古地块都是由古生代蛇绿岩、具有活动陆缘亲缘性的岩浆岩、增生杂岩和少量前南华纪岩石组成的古生代陆缘增生造山带或岛弧造山带.在此基础上,对该区地质历史上古老变质岩与地块关系、佳蒙地块是否存在、构造单元构造属性随时间变化等问题进行了初步讨论.      

不同构造环境下的壳─幔过渡带结构

位于中国西北部的天山造山带与准噶尔盆地是典型的盆岭构造。通过对横跨天山造山带与准噶尔盆地的沙雅-布尔津地学断面地震宽角反射、折射资料进行小波分析,获得了天山造山带与准噶尔盆地壳-幔过渡带的详细结构。结果表明,天山造山带的壳-幔间是以多个薄层过渡的。这些薄层的层厚度2～3km不等,层速度高低相间,总厚度约20km,平均速度较低,接近塔里木盆地下地壳的速度。塔里木盆地北缘与准噶尔盆地的壳-幔间不具有这种特点,其壳-幔间主要表现为一级间断面。而位于中国东北部的间阳-海城-东沟深地震测深剖面所揭示的辽东台隆-辽河盆地-燕山台褶带壳-幔过渡带的结构似乎具有完全相反的特征：辽河盆地的壳-幔过渡带比较复杂,它由数个薄层叠合而成,总厚度达15km;辽东台隆与燕山台褶带壳-幔过渡带结构十分简单,皆以一级间断面过渡为主。研究认为,造成二者差异的主要原因是它们所处的构造环境不同：前者为挤压环境,而后者为伸展环境。在挤压环境下,复杂的壳-幔过渡带形成于造山带的下面;而在伸展环境下,复杂的壳-幔过渡带形成于盆地的下面。壳-幔过渡的复杂程度与构造活动性相联系,在一定程度上反映了岩石圈目前的构造活动水平。     

洋板块地层学的概念、模式、组成及失序变化*

着重介绍了洋板块地层的概念、模式、组成及失序变化特征。造山带混杂岩和大陆边缘增生复合体是经历俯冲碰撞消亡后的古洋沉积记录,利用微体古生物地层学和同位素年代学方法可以重建造山带混杂岩和大陆边缘增生复合体的原始地层。洋板块地层(学)是用来描述沉淀在洋壳基底之上的沉积岩和火成岩序列的术语,其开始于洋中脊形成,终止于该洋中脊被移入到汇聚边缘增生楔。从造山带混杂岩中重建的古大洋地层的基本组成大体相似,但因大洋岩石圈的岩浆背景不同,造成不同时期和不同类型的洋板块地层组成也会有差异。在前人研究成果的基础上, 笔者通过对不同类型洋板块地层进行分类,介绍了如何从经历碰撞造山过程的增生造山带进行洋板块地层的重建。引入“洋板块地层学”概念的主要目的在于通过对因俯冲增生而消亡的具有洋壳基底的构造洋盆和边缘海盆地的地层单元进行重建,恢复已消失洋的地层组成单元,这对造山带地层解析、造山带构造古地理恢复、重大构造变革期古地理学研究和板块重建等都将起到积极的促进作用。     

滇西北剑川-虎跳峡大规模东向西逆冲推覆构造——兼论滇西扬子陆块区与西藏-三江造山系界线

基于剑川至虎跳峡一带的野外区域地质调查资料, 论述剑川-虎跳峡断裂的性质, 进而探讨扬子-华南陆块区与西藏-三江造山系的界线。野外观察显示, 该区存在大规模自东向西的逆冲推覆构造, 从剑川开始, 经丽江白汉场—汝寒坪、忠义村, 至香格里拉县的虎跳峡镇(下桥头)等地, 多条剖面可见上扬子稳定型的古生代及中生代三叠纪地层自东向西逆冲推覆在西藏-三江造山系地层层序之上, 推覆距离大于50 km。因此, 剑川—虎跳峡断裂不是两大板块的边界, 而是一条狭长的构造窗。两大板块的界线应是大理-剑川-丽江-木里断裂, 南段接红河断裂。      

内蒙古多伦中酸性侵入岩岩石地球化学特征及构造环境分析

内蒙古多伦县北部分布四个中酸性岩体,其岩石类型为:二长花岗岩、石英正长岩、石英正长斑岩和石英二长斑岩,出露面积0.5~12.4km~2不等,产状为岩株。同位素测龄成果显示二长花岗岩形成年龄为143.8±1.2 Ma,属晚侏罗世晚期(J_3);石英二长斑岩形成年龄为138.4±0.6Ma,属早白垩世早期(K_1)。岩石系列为高钾、钙碱性系列。据岩石地球化学特征推断:研究区内的四个岩体具同源特征,是岩浆同源演变的产物,岩浆来源为中下地壳。结合岩石Q-Ab-Or-H_2O相图,岩浆结晶温度接近750~800℃。二长花岗岩形成于大陆碰撞地球动力学环境即陆内造山构造环境;石英正长岩、石英正长斑岩、石英二长斑岩形成于造山后期构造环境。研究区在晚侏罗世晚期陆内碰撞造山运动已经结束而转入造山后期构造环境,至早白垩世早期大规模双峰式火山岩的喷发标志着研究区全面进入陆内造山后的裂谷阶段或者陆内伸展运动阶段。     

龙门山陆内复合造山带的四维结构构造特征

位于扬子陆块和松潘陆块过渡带上的龙门山造山带,是在印支期中国大陆主体拼合和秦岭造山带形成过程中开始发育、燕山期陆内构造活动中继承发展、喜马拉雅期印-亚碰撞和青藏高原隆升过程中遭受改造并定型的。现今构造面貌是扬子陆块向北漂移过程中产生的北西向推挤力、源自秦岭造山带的南北向推挤力和源自青藏高原的东西向推挤力三者联合作用的结果,因此是一个典型的陆内复合造山带。其陆内复合结构构造特征具有下列特点。 1）倾向上,龙门山造山带由茂县-汶川断裂、北川-映秀断裂、安县-灌县断裂和广元-大邑（隐伏）断裂4条主干断裂分隔显示出明显的分带变形特征,由北西向南东具有层次渐浅、强度递减、卷入层位变新的趋势,总体上呈前展式扩展。 2）走向上,龙门山造山带呈现北、中、南段三分格局,它们在基底性质及展布、地层发育及演化历史、变形特征、沉降与隆升特征、活动构造等多个方面具有差异。 3）垂向上,龙门山造山带发育多层次滑脱构造,最重要的滑脱界面是15～20 km深处的低速层和中下三叠统富膏盐岩层,由此控制了深浅构造不一致的变形幅度和变形样式。 4）时间演化上,龙门山造山带表现出倾向上的前展式扩展和走向上的分段式递进性或序次性演化的趋势：印支期,龙门山中北段活动较强,由北东向南西逐渐扩展,主要为挤压逆冲和左旋走滑作用; 燕山期,构造活动总体上趋于相对平静,具有南北分段、由北东向南西迁移的特征; 喜马拉雅山期,龙门山中南段活动较强,由南西向北东逐渐扩展和递进,主要为挤压逆冲、隆升和右旋走滑作用。     

五台山早元古代高压变质作用研究

根据对原五台群北金刚库组变质作用的深入研究，表明它们经历了三期变质作用，即经历了弧陆碰撞导致的初始的构造埋藏变质作用（M1）以及随后深埋到42km深度的峰期高压变质作用（M2）,压力可达0．8－1．4GPa，随后经历了快速抬升所导致的近等温的降压过程（M3）到0．5－0．7GPa，整个过程为顺时针方向演化的P－T轨迹，与造山带型P－T－t轨迹型式相同。     

大别山东缘郯庐两期走滑剪切带形成的温压条件与造山带折返的关系

郯庐断裂带与大别造山带在大别山东缘相复合 ,并将大别—苏鲁造山带左行错开达 5 0 0km。本文以大别山东缘为研究背景 ,通过对郯庐断裂带两期左旋走滑韧性剪切带温压条件的估算及热年代学信息的分析 ,来探讨大别造山带在早侏罗—早白垩世之间的折返历史与隆升量。通过矿物组合、矿物变形特征以及白云母—绿泥石地质温度计得到郯庐早、晚两期剪切带的形成温度均为 4 0 0～ 4 5 0℃。通过多硅白云母Si原子数地质压力计计算得到早、晚两期剪切带的形成压力分别为 0 .2 5～ 0 .36GPa和 0 .2 4～ 0 .39GPa。考虑到剪切摩擦加热和构造超压的影响 ,笔者推断郯庐两期走滑剪切带形成的最大深度均不超过 12km ,且两期走滑剪切带的形成深度至多相差 1～2km。郯庐断裂带在约 190Ma和 12 8Ma经历了两期走滑冷却事件 ,而在此期间 ,大别造山带东缘经历了一个构造平静期 ,基本没有发生隆升。根据郯庐断裂带的信息 ,造山带在早白垩世的热隆事件中的隆升幅度小于 12km。     

Seismic Activity in the Himalayan Orogenic Belt and Its Related Geohazards

Himalayan orogenic belt is the highest and largest continental collision and subduction zone on the Earth. The Himalayan orogenic belt has produced frequent large earthquakes and caused several geohazards due to landslides and housing collapse, having an impact on the safety of life and property along a length of over 2500 km. Here we took three earthquake clusters as examples, which occurred at Nepal Himalaya, eastern Himalayan syntaxis and western Himalayan syntaxis, respectively. Here we calculated the earthquake locations and fault plane solutions based on the waveform data recorded by seismic stations deployed in source areas by the Institute of Tibetan Plateau Research, Chinese Academy of Sciences. We found that at the Nepal Himalayan, the Main Himalayan Thrust is the major tectonic structure for large earthquakes to occur. At the eastern Himalayan syntaxis, most earthquakes are of the reverse or strike-slip faulting. The major tectonic feature is the combination of the NE-dipping thrust with the southeastern escape of the Tibetan plateau. At the western Himalayan syntaxis, intermediate-depth earthquakes are active. These observations reveal the geometry of the deep subduction of the continental plate with steep dipping angle.     

喜马拉雅造山带地震活动及其相关地质灾害

喜马拉雅造山带是地球上海拔最高、规模最大的陆陆板块俯冲碰撞带在这条长达2 500 km的板块边界上,近年来多次发生破坏性地震,造成大规模的滑坡、房屋倒塌等次生灾害,给人民生命和财产安全造成严重的威胁。分别选取尼泊尔喜马拉雅、喜马拉雅东构造结和喜马拉雅西构造结地区近期发生的3个地震震群作为研究实例,基于中国科学院青藏高原研究所在研究区架设的区域流动地震台站记录的波形资料,对地震的震源位置和震源机制解进行计算。结果表明,在尼泊尔喜马拉雅地区,主喜马拉雅逆冲断裂是大地震的主要发震构造;东构造结地区的地震以逆冲和走滑型为主,表明印度板块向北东方向的逆冲推覆和青藏高原向东南逃逸的侧向挤出是该地区的主要构造背景;西构造结地区中深源地震多发,揭示了高角度大陆深俯冲的几何形态。     

CARBONATITES FROM THE EASTERN HIMALAYAN SYNTAXIS: PETROLOGY AND TECTONIC IMPLICATIONS

Most carbonatites occur in relatively stable, intra\|plate areas but some are found to occur in near to plate margins and may be linked with plate separation (Woolley, 1989). Although many carbonatites have been discovered to occur in the orogenic belts in recent years, most of these rocks are related to post\|orogenic magmatism, that is, the rocks occur in the specially extensional setting. Therefore it is unusual that such magmatic rocks occur in the typical convergent environment. Here we report carbonatites and associated ultramafic and mafic rocks in the core of the eastern Himalayan syntaxis. The eastern Himalayan syntaxis consists of three tectonic units: the Gangdise, the Yarlung Zangbo, and the Himalayan units, each of which is bounded by faults (Liu & Zhong, 1997). The Himalayan unit, the northernmost exposed part of the Indian plate, is divided into two complexes, the amphibolite facies complex in the south and the granulite facies complex in the north. The granulite facies complex in the Himalayan unit have been argued to experience high\|pressure metamorphism and represent materials buried to upper\|mantle depths (Liu & Zhong, 1997). The carbonatites and associated ultramafic and mafic rocks only occur in the granulite facies rocks and are divided into two belts: northern and southern belts.The northern belt extends at least 30km, and is about 20km in width. The southern belt extends several kilometers, and is 3km or so in width. Each belt consists mainly of differently compositional dykes, extending parallel to gneissosity of granulite facies gneiss. Carbonatitic agglomerates are observed in the northern belt. From the center of carbonatite dykes to country rocks, five types of rock are observed: the center parts of carbonatites, the rim parts of carbonatites, ultramafic and mafic rocks, altered rocks and country rocks. The gneissosity of country rock was deformed by intrusion of dykes.     

北淮阳地区中生代逆冲推覆构造

大别山北缘北淮阳地区中生代逆冲推覆构造作用使本区广泛发育的以下古生界为主体的中、浅变质构造地层,在数百公里的范围内向ＮＥ逆冲（掩）于石炭系和中侏罗统之上,形成一系列构造窗、飞来峰和逆冲（掩）断层带,其最小逆冲推覆距离平均为２４４ｋｍ,形成时代介于Ｊ２—Ｊ３之间,其形成与大别造山带的碰撞挤压有关,是大别地块中生代向北仰冲作用的结果。     

Structural evolution of the Gonzha block (Argun-Idermeg superterrane of the Central Asian orogenic belt)

The structural data and available geochronological constraints suggest that the Gonzha tectonic block located in the northeastern part of the Argun-Idermeg superterranes, Central Asian orogenic belt, is considered as an analogue of Cordilleran metamorphic core complexes of western Transbaikalia. These metamorphic core complexes, as well as the Gonzha block, may have resulted from collapse of a Late Mesozoic orogen after closure of the Mongolia-Okhotsk paleo-ocean basin.     

RELATIONSHIP BETWEEN P-T CONTITIONS OF TWO PHASES OF TAN-LU STRIKE-SLIP SHEAR ZONES AND DELAMINATION OF OROGENIC BELTS ON THE EASTERN MARGIN OF THE DABIE MOUNTAINS

The Tan-Lu fault zone joins the Dabie Mountains on its eastern margin, and offsets the Dabie and Sulu orogenic belts sinistrally for about 500 kin. On the basis of calculation of temperature and pressure experienced by the two phases of the fault zone as well as the thermo-chronological information on mylonite from the earlier and later Tan-Lu fault zones on the eastern margin of the Dabie Mountains, this paper discusses the delamination history and uplifting magnitudes of the Dabie Mountains from earlier Jurassic to earlier Cretaceous. From mineral assemblages, mineral deformation and muscovite-chlorite geothermometry calculation, it is known that the temperature experienced by the two phases of Tan-Lu fault zones are between 40℃ and 450℃, and the confining pressures are between 0.25Gpa and 0.36GPa for the earlier shear zones and 0.24-0.39GPa for the late shear zones. According to the geobarometry of Si-in-phengite and by considering shear heating and tectonic over-pressure, it is concluded that the maximum formation depths for the two phases of the ductile shear zones are not more than 12 kin. Differential formation depths for the two phases of shear zones are 1-2 km at most. At about 190 Ma and 128 Ma, the Tan-Lu fault zone experienced two phases of cooling events. During this period, the eastem margin of the Dabie Mountains experienced a tectonic calm period and no uplifting. According to information from the Tan-Lu fault zone, the uplifting magnitudes of the Dabie orogenic belts are not more than 12 km during the earlier Cretaceous.     

塔藏构造混杂岩带特征

运用大陆造山带构造岩片填图方法，首次对九寨沟塔藏构造带进行了系统研究。认为塔藏构造带为-构造混杂岩带。其南北边界断裂清楚，北界为牙扎沟断裂，呈北西-南东向展布；南界为荷叶断裂，也呈北西-南东向展布，边界断裂内部为塔藏构造混杂岩带，呈北西-南东向延伸长16-24km，宽7-8km，由上古生界与三叠系的多个大小不同，形态各异的构造岩片（或岩块）混杂堆积组成，与塔藏岩组砂板岩呈断层接触，总体表现为块体之间无序，块内有序，微观变形特征清楚，三维有限应变测量显示为北东-南西向，近南北向两个方向压缩，结合测区构造地质环境分析有4期变形。     

Structural framework of the Bashkirian anticlinorium, SW Urals

The Bashkirian anticlinorium of the southwestern Urals shows a much more complex structural architecture and tectonic evolution than previously known. Pre-Uralian Proterozoic extensional and compressional structures controlled significantly the Uralian tectonic convergence. A long-lasting Proterozoic rift process created extensional basement structures and a Riphean basin topography which influenced the formation of the western fold-and-thrust-belt with inversion structures during the Uralian deformation. A complete orogenic cycle during Cadomian times, including terrane accretion at the eastern margin of the East European platform, resulted in a high-level Cadomian basement complex, which controlled the onset of Uralian deformation, and resulted in intense imbrication and tectonic stacking in the subjacent footwall of the Main Uralian fault. The Uralian orogenic evolution can be subdivided into three deformation stages with differently oriented stress regimes. Tectonic convergence started in the Late Devonian with ophiolite obduction, tectonic accretion of basin and slope units and early flysch deposits (Zilair flysch). The accretionary complex prograded from the SE to the NW. Continuous NW/SE-directed convergence resulted finally in the formation of an early orogenic wedge thrusting the Cadomian basement complex onto the East European platform. The main tectonic shortening was connected with these two stages and, although not well constrained, appears to be of Late Devonian to Carboniferous age. In the Permian a final stage of E–W compression is observed throughout the SW Urals. In the west the fold-and-thrust-belt prograded to the west with reactivation of former extensional structures and minor shortening. In the east this phase was related to intense back thrusting. The East European platform was subducted beneath the Magnitogorsk magmatic arc during the Late Paleozoic collision. The thick and cold East European platform reacted as a stable rigid block which resulted in a narrow zone of intense crustal shortening, tectonic stacking and high strain at its eastern margin. Whereas the first orogenic wedge is of thick-skinned type with the involvement of crystalline basement, even the later west-directed wedge is not typically thin-skinned as the depth of the basal detachment appears below 15 km and the involvement of Archean basement can be assumed.     

西南“三江”造山带大地构造相

西南“三江”造山带由多条缝合带及其间多个大小不等的中间陆块构成,其大地构造属性与划分方案历来受地学界关注与争论。本文以大地构造相理论为切入点,将西南“三江”造山带划分出11个一级及其若干二级大地构造相,包括俯冲、消减杂岩、仰冲等一级大地构造相以及与其相伴的后造山及走滑大地构造相。俯冲大地构造相类包括块体变质相、前陆褶冲相、前陆盆地相;消减杂岩大地构造相包括洋壳残片相、陆壳残片相、增生变质杂岩相、活化基底相、侵入岩相、上叠磨拉石相;仰冲板块大地构造相包括弧前盆地相、岛弧相、弧后及弧间盆地相。特提斯洋向北消减,使泛华夏大陆群各块体先拼接,其后弧后扩张、闭合、造山,从而形成了“三江”造山带“多缝合带”、“多陆体”特征。     

华北板块北缘中元古代造山带的确立及其构造演化

华北板块北缘发育一条中元古代晚期大陆边缘碰撞造山带 ,它由内蒙西部狼山起向东延伸到辽西和吉林东部一带 ,全长 2 0 0 0余km。造山带内部发育了不同类型变质的沉积岩、火山沉积岩 ,以及各种类型深成侵入岩。在 1.0Ga左右 ,由西伯利亚板块和华北板块对接碰撞 ,形成了巨大陆缘碰撞造山带。这次构造事件是Rodinia超大陆拼合事件的一部分 ,表明了在Rodinia超大陆时期华北板块和西伯利亚板块是连在一起的。     

大别地块超高压变质省的构造变形研究

构造解析的基本目的是建立构造事件造成的地质体几何学、运动学、动力学和流变学。大陆碰撞造山带内含柯石英及微粒金刚石等矿物组合的超高压（ＵＨＰ） 变质岩的形成和折返,是极为复杂的地球动力学过程。与世界上已知大多数超高压变质带相似,中国大别地块内超高压变质省现今观察到的主体构造形式,主要是在碰撞或超高压变质峰期后伸展体制下形成的。通过对大别超高压变质省内伸展组构及挤压（ 碰撞） 组构的鉴别、分析,结合有关超高压变质带构造学研究领域的简略综述指出,在揭示超高压变质带的形成及折返动力学过程中,构造解析的思维和工作方法是行之有效的     

五垛山复式岩基锆石U-Pb年龄及其地质意义

五垛山复式岩基位于北秦岭构造带东段,地处朱阳关—夏馆断裂和乔端—瓦穴子断裂之间,整体呈NWW向展布,由多个岩体复合组成,具多期次岩浆活动特征,岩性主要为黑云母二长花岗岩。本文在其解体出来的石门序列和五垛山序列中,采集5件样品进行了锆石U-Pb年龄值测定。测定结果对该区岩浆活动、构造背景及区域构造演化、地层时代确定等具有一定的地质意义。