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本文对松潘-甘孜和西秦岭造山带地球物理特征以及基底构造进行了研究。研究表明：松潘-甘孜地块与西秦岭造山带的基底性质相似，均具有扬子块体的构造属性。褶皱基底的分布范围为：西南部以二道沟-玉树-理塘为界；东至青川-都江堰，即龙门山断裂带；北部边界由西到东，沿昆仑南缘至花石峡，然后转向北东，沿兴海-夏河-西和展布。在深地震测深和高温、高压岩石密度研究结果的约束下对重力资料进行反演，得到该地区的基底起伏。反演结果表明：松潘-甘孜-西秦岭地区的基底深度为1．3～8．6km（以海平面起算）。阿坝-甘孜-道孚以及夏河-泽库-兰州一带为基底隆起区；若尔盖-唐克-红原、花石峡达日和-达日东南一带为基底凹陷区，其中红原附近基底深度达8．6km，为全区基底深度最大的地方。 相似文献
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松潘-甘孜地区三叠系碎屑沉积岩地球化学特征及其锆石年龄研究 总被引：8，自引：1，他引：8
松潘—甘孜地块地处中国西南部,是中国大陆构造中重要的基本构造单元,三叠系碎屑沉积岩广泛分布,本文对松潘—甘孜地块的三叠系碎屑沉积岩4个样品的稀土元素及锆石U_Pb地球化学特征进行了系统研究。4个样品的稀土元素分布型式特征非常接近,这表明松潘—甘孜地区的三叠系碎屑沉积岩具有相同的来源。明显的轻、重元素分馏和铕异常则表明碎屑岩源区地壳内有较的深熔作用。锆石Th/U比和阴极发光表明它们基本上来自岩浆岩物源区。SHRI MP结果显示206Pb/238U年龄集中在200~1000Ma和1600~2400Ma,其中1600~2400Ma的锆石年龄记录了扬子克拉通基底的形成事件;200~1000Ma的锆石年龄反映了青白口纪及东吴运动期间扬子克拉通强烈的岩浆活动。此外,中三叠世末期秦岭造山带全面隆升成山,也阻断了华北克拉通为该区提供碎屑沉积岩的可能,因此,松潘—甘孜地区的三叠系碎屑沉积岩来源于杨子克拉通。 相似文献
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根据重磁资料分析,扬子地台与松潘-甘孜造山带的界线应以武都-文县断裂为界,而不是划在龙门山断裂处.由此可见,整个龙门山地区应划归扬子地台,同时认为松潘-甘孜造山带的基底性质与扬子地台的基底性质完全不同. 相似文献
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东昆仑造山带中地壳存在古洋壳俯冲的深反射地震证据 总被引：1，自引：0，他引：1
INDEPTH Ⅳ深反射地震测线横跨可可西里-巴颜喀拉地块和东昆仑-柴达木地块,为揭示青藏高原东昆仑造山带深部构造提供了直接地球物理证据。针对地表和地下"双复杂"地质构造条件,地震数据处理中通过剩余折射波静校正技术、异常振幅噪声衰减技术和CRS优化叠加技术,获得了较高信噪比的地震反射叠加剖面。INDEPTH Ⅳ深反射地震剖面揭示,在东昆仑造山带岩石圈上、下地壳之间存在不连续的古洋壳反射同相轴,该反射界面应属古特提斯域松潘-甘孜洋壳向北俯冲遗迹,不连续特征反映中生代东昆仑-柴达木地块南缘属于被动大陆边缘碰撞带。利用INDEPTH Ⅳ深反射地震单炮、速度和叠加剖面等成果,综合解译数据,提出东昆仑造山带隆升过程的另一种模式,以助于深化东昆仑造山模式认识。 相似文献
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2005年10月至2007年4月,我们在松潘-甘孜、龙门山地块布设的流动地震台阵观测剖面正好经过地震震源区映秀,这为研究地震震源区深部结构提供很好的机会.观测剖面自成都龙泉山,途经都江堰、卧龙,终止于新都桥,全长约400km,台站间距5～10km,34个流动宽频带地震仪共记录到该时间段内5.5级以上远震事件542个,大于等于6.0级为195个.利用该观测剖面记录到的远震P波波形资料,采用接收函数方法来研究汶川Ms8.0级地震震源区地壳深部结构,结合地震构造背景的分析,探讨引起这次地震的动力学模式,并由此认识汶川地震的孕育与成因机制.根据震源区地表破裂和余震分布及深部结构的综合分析,可以划出震源区下方的地震断裂带.主要研究结果表明:1)根据界面分布特征,发现松潘-甘孜地块及龙门山推覆体中在20～60km深度存在一个厚度约15～20km的低速中地壳,而四川盆地地壳内不存在低速层.该中地壳内的低速层,是引起中上地壳的推覆运动的滑脱层.2)Moho面自扬子盆地(36～42km)跨龙门山(50km)到松潘-甘孜腹地(62～65km)逐渐加深,跨鲜水河断裂又变浅(60km),说明横跨扬子盆地-龙门山-松潘-甘孜地块的该断裂带是地壳厚度的陡变带.该结果揭示了松潘-甘孜地块与扬子地块是碰撞接触模式,龙门山的推覆构造就是上地壳逆冲的结果. 相似文献
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松潘-甘孜褶皱带内部火山岩类的分布有限,对产于松潘-甘孜褶皱带中部洼赛和阿坝地区的火山岩进行的锆石LA-ICP-MS定年、锆石Hf同位素及地球化学的研究结果表明,洼赛火山岩形成时代为205±1Ma,阿坝火山岩形成时代为210～213Ma. 相似文献
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松潘- 甘孜造山带巨厚的三叠系复理石沉积盖层给探讨其基底性质、俯冲- 碰撞过程和深部岩浆作用增添了难度，使得带内广泛出露的花岗质岩体和少量镁铁质岩体成为解开松潘- 甘孜造山带构造演化谜团的重要研究对象。锆石U- Pb定年结果表明道孚花岗闪长岩形成于223. 5~217. 4 Ma，炉霍二长岩结晶年龄为219. 4 Ma，辉长岩为218. 9 Ma，均属于晚三叠世岩浆活动的产物。化学成分研究结果表明，花岗质岩石都表现出I型花岗岩特征，其中炉霍二长岩具有较高的Ba、Sr含量，相对较高且均一的εHf(t)值（-3. 69~-1. 65），表明其可能来源于富集玄武质新生下地壳的熔融。道孚花岗闪长岩具有分散的εHf(t)值（-13. 51~0. 41），野外和地球化学特征指示其形成于幔源熔体与古老壳源熔体的混合。辉长岩在微量元素蜘蛛图上具有类似的模式，不同程度富集Ba、Sr、Pb、Th和U元素，出现Nb、Ta、Ti元素亏损，具有岛弧玄武岩的特征，来源于流/熔体交代的地幔楔部分熔融。综合区域已有资料，我们对甘孜- 理塘洋的演化历史提出新的认识，认为甘孜- 理塘洋不仅仅存在向南俯冲的可能性，同时也具有北向俯冲的历史，晚三叠世道孚- 炉霍岩浆岩的形成受控于甘孜- 理塘洋向北边松潘- 甘孜地块俯冲的背景之下。 相似文献
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松潘-甘孜地体中部晚三叠世安山质增生弧的确定及其意义 总被引：2，自引：0，他引：2
本文研究揭示,巴颜喀拉-松潘甘孜地体(简称松潘-甘孜地体)中部三叠系复理杂岩中的安山岩块是增生弧岩浆活动的产物,具有高度不均一均匀的岩石组构、地球化学与同位素组成。特别是这些安山岩显示了与松潘-甘孜三叠系海相浊积岩具有高度的Sr-Nd同位素亲缘性,沿亏损地幔和三叠系海相浊积岩混熔曲线分布,且主要分布于三叠系海相浊积岩端元区。这表明该增生弧安山质岩浆主要由增生楔中的海相浊积岩基质部分熔融形成,并受到了增生楔中大洋岩石圈残片等超镁铁/铁镁质组分的不同程度混染。安山岩时代(226.8±1.9Ma~213.7±0.9Ma)以及同时期广泛的S型花岗岩侵入活动(228±2Ma~204±7Ma)揭示增生弧形成于晚三叠世Norian期。前人工作表明,位于松潘-甘孜地体东北隅的诺尔盖-松潘盆地是一个周缘前陆盆地。因此,松潘-甘孜地体并非单一构造成因的地质体,至少由二叠纪-三叠纪演化的古特提斯大洋和中三叠世拉丁期-晚三叠世诺列期周缘前陆盆地两部分构成。前者是松潘-甘孜地体的主体部分,由松潘-甘孜古特提斯洋在三叠纪时期快速收缩形成的增生楔杂岩组成,其上发育增生弧,局部残存古特提斯大洋盆地及被构造移置的洋壳残片;后者为西秦岭弧(248~234Ma)与扬子地块碰撞的产物。 相似文献
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Hong-Fei Zhang Li Zhang Nigel Harris Lan-Lan Jin Honglin Yuan 《Contributions to Mineralogy and Petrology》2006,152(1):75-88
The Songpan-Garze fold belt, located in the eastern part of the Tibetan Plateau, covers a huge triangular area bounded by the Yangtze (South China), the North China and the Tibetan Plateau blocks. In the northeastern part of the Songpan-Garze fold belt, the Yanggon and Maoergai granitoids provide insights into regional tectono-magmatic events, basement nature and tectonic evolution. U–Pb zircon SHRIMP dating shows that the Yanggon and Maoergai granitoids have magmatic crystallization ages of 221 ± 3.8 Ma and 216 ± 5.7 Ma, respectively. Both the granitoids display adakitic geochemical signatures, suggesting that their magma was derived from partial melting of thickened lower crust. Pb–Sr–Nd isotopic compositions for granitoids reveal that there is an unexposed Proterozoic basement in the Songpan-Garze belt, which has an affinity with the Yangtze block. During development of the Paleo-Tethys ocean, the basement of the Songpan-Garze belt would be a peninsula approaching the Paleo-Tethys ocean from the Yangtze block. 相似文献
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松潘地块与西秦岭造山带下地壳的性质和关系——深地震反射剖面的揭露 总被引：28，自引：1，他引：28
松潘地块位于青藏高原的东缘，处于中国大陆东西向构造与南北向构造的结合部位，特殊的构造环境使其长期控制并影响着中国大陆的形成与演化。探测松潘地块的岩石圈细结构，揭示其与东昆仑-西秦岭造山带的关系，既可为研究青藏高原东北缘板块碰撞的深部过程奠定基础，同时又关联着松潘地块的油气远景评价。2004年完成了第一条横过松潘地块北缘若尔盖盆地和西秦岭造山带的长约257km的深地震反射剖面，首次揭露出若尔盖盆地和西秦岭造山带岩石圈的细结构。发现若尔盖盆地和西秦岭造山带同属统一的稳定的大陆地块，并且下地壳均以北倾的强反射为主要特征。这种北倾的反射为松潘地块向西秦岭下地壳俯冲提供了地震学证据。近于平坦的Moho反射特征反映出西秦岭造山带在造山后又经历了强烈的伸展作用。 相似文献
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青藏高原东北缘早古生代造山系中前寒武纪微陆块的再认识——兼谈原特提斯洋的起源 总被引：1，自引：0，他引：1
在青藏高原东北缘的祁连-阿尔金-昆仑早古生代造山系中,夹杂有一些前寒武纪大陆块体,这些地块的组成、性质和演化既蕴含有超大陆聚散的重要信息,也对原特提斯体系的洋陆格局、造山类型和造山机制有重要启示意义。本文综合近年来这些前寒武纪微陆块的研究进展,结合我们所获得的新的研究资料,梳理了这些前寒武纪微陆块变质基底的岩石组成、构造热事件及年代格架,得出以下主要认识:(1)这些前寒武纪微陆块普遍遭受早古生代造山事件的改造并发生再活化。它们或者作为早古生代原特提斯洋的活动大陆边缘,被洋壳俯冲有关的弧岩浆和变质作用改造,以早古生代大陆弧的形式存在;或者被早古生代碰撞造山过程中的陆内变形、增厚地壳及相关的区域变质作用、深熔作用和碰撞型花岗岩所改造。(2)在这些前寒武纪微陆块中,仅仅欧龙布鲁克地块保存有早前寒武纪的变质基底,具有克拉通性质。中元古代以前,欧龙布鲁克地块的变质基底与华北克拉通(特别是阿拉善地块)和塔里木克拉通具有相似的岩石组成和年代格架;而晚中元古代到新元古代,所有的前寒武纪微陆块与华南陆块和塔里木陆块的亲缘性更强。(3)青藏高原北缘早古生代造山系中的大部分前寒武纪微陆块可能在罗迪尼亚超大陆解体时已从冈瓦纳大陆北部分离,而柴达木地块记录了泛非期造山作用的构造热事件,可能在泛非造山期(530Ma)以后才从冈瓦纳大陆分开;在青藏高原东北部,晚新元古代-早古生代并不存在统一的原特提斯洋,原特提斯洋的打开是穿时的。 相似文献
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Asbjrn Johan Breivik Rolf Mjelde Paul Grogan Hideki Shimamura Yoshio Murai Yuichi Nishimura 《Tectonophysics》2003,369(1-2):37-70
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. 相似文献
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川西北松潘-阿坝地区油气勘探进展与初步评价 总被引：2，自引：1，他引：2
位于青藏高原东北部松潘-甘孜构造带中央部位的松潘-阿坝地区是目前中国石化公司油气勘探与探索的全新领域。2002年以来中国石化南方勘探开发分公司对该区进行了系统的石油地质、重、磁、电、震、遥感、化探等综合勘探与评价研究，发现了相对稳定的若尔盖隐伏地块、多个局部构造显示和化探异常区域，认为该区可能存在下古生界生烃、上古生界储集、三叠系封盖的油气地质条件，评价优选出了若尔盖坳陷的中部凸起及其向北侧凹陷带过渡的斜坡地带为近期油气勘探的有利地区并实施了红参1井的钻探。各项勘探成果资料表明该区应该具有油气勘探前景，但三叠系巨厚且经历了多期形变改造，油气勘探的难度较大，加强随钻跟踪分析、深化油气地质研究并开展物探技术攻关是近期工作的重点。 相似文献
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We report a series of two-ship multichannel seismic experiments carried out on the continental shelf off northwest Scotland in February 1981. Both expanding spread and constant offset profiles were shot using explosives and a 16.4-1 airgun. The expanding spread shot-receiver configurations yield detailed information on the variation of seismic velocity with depth, whilst constant offset profiles allow us to monitor lateral variations in the upper crustal velocity structure. We show an example of marked variations in the efficiency of compressional to shear wave conversion along a constant offset profile over shallow Lewisian basement west of the Outer Hebrides which we interpret as due to changes in the uppermost basement velocity structure. From profiles north of Cape Wrath we show that where the Precambrian Lewisian basement is buried beneath Mesozoic sediments of variable thickness we can use the constant offset profile of the basement refractor to strip off the effect of the sediments and so correct deeper crustal returns on the coincident expanding spread profiles. 相似文献
17.
青藏高原东部及其邻区力学耦合的岩石圈变形模式 总被引：1，自引：0，他引：1
根据青藏高原东部及其邻区布设的143个宽频带固定和流动地震台站的远震记录的SKS波分裂分析获得了各台站的快波偏振方向和快慢波之间的时间延迟。SKS分裂分析结果总体上反映了高原东部的上地幔物质流动方向,即高原内部表现为环绕喜马拉雅东构造结的顺时针旋转。在造山运动过程中有关岩石圈地壳和地幔力学耦合的造山变形方式,用从GPS和第四纪断裂滑动速率数据确定的地面变形场和由地震波各向异性数据推断的地幔变形场联合分析来定量求得。在青藏高原东部和云南、四川等地区新近快速增加的GPS和SKS波分裂观测数据,提供了对青藏高原岩石圈地幔实际变形方式的检验。这些新的数据不仅加强了高原内部力学耦合岩石圈的证据,而且也解释了高原外部相同的耦合特征。文中引入简单剪切变形和纯剪切变形的概念,用于解释高原内外不同的耦合变形特征。青藏高原和周围区域力学耦合岩石圈的垂直连贯变形有两个方面的大陆动力学含义:第一,岩石圈垂直强度剖面被一个重要的条件所约束,即要求与重力势能变化相关的应力能够从地壳传递到地幔;第二,青藏高原各向异性的空间变化反映了一个岩石圈变形的大尺度模式,以及从高原内部的简单剪切变形向高原外部的纯剪切变形的过渡带。文中提出的力学耦合岩石圈变形模型与当前已有的多种造山运动变形模型具有不同的变形含义,因此,地幔变形在青藏高原隆升过程中起主要作用。 相似文献
18.
The Deep Geophysical Structure of the Middle Section of the Longmen Mountains Tectonic Belt and its Relation to the Wenchuan Earthquake 总被引：1，自引：0，他引：1
Investigation of the deep geophysical structure of the Longmen Mountains tectonic belt and its relation to the Wenchuan Earthquake is important for the study of earthquakes. By using magnetotelluric sounding profiles of the Luqu–Zhongjiang and Anxian–Suining; seismic sounding profiles of the Sichuan Maowen–Chongqing Gongtan, the Qinghai Huashi Gorge–Sichuan Jianyang, and the Batang–Zizhong; and magnetogravimetric data of the Longmen Mountains region, the deep geophysical structure of the Songpan–Ganzi block, the western Sichuan foreland basin, and the Longmen Mountains tectonic belt and their relation was discussed. The eastward extrusion of the Qinghai–Tibet Plateau thrusts the Songpan–Ganzi block upon the Yangtze block, which obstructs the eastward movement of the Qinghai–Tibet Plateau. The Maoxian–Wenchuan, Beichuan–Yingxiu, and Anxian–Guanxian faults of the Longmen Mountains fault belt dip to northwest with different dip angles and gradually converge in the deeper parts. Geophysical structure suggests that an intracrustal low-velocity, low-resistivity, and high-conductivity layer is common between the middle and upper crust west of the Longmen Mountains tectonic belt but not in the upper Yangtze block. The Sichuan Basin has a thick low-resistance sedimentary layer on a stable high-resistance basement; moreover, there are secondary paleohighs and depression structures at the lower part of the western Sichuan foreland basin with characteristic of high magnetic anomalies, whereas the Songpan–Ganzi block has a high resisitivity cover of upper crust and continues to a low-resistance layer. Considering the Longmen Mountains tectonic belt as the boundary, there are Bouguer gravity anomalies of "one belt between two zones." Thus, we infer that there is a corresponding relation between the inferred crystalline basement of the Songpan block and the underlying basin basement of the Longmen Mountains fault belt. Furthermore, there may be an extensive ancient Yangtze block, which is west of the Ruoergai block. In addition, the crust–mantle ductile shear zone under the Longmen Mountains tectonic belt is the main fault, whereas the Beichuan–Yingxiu and Anxian–Guanxian faults at the surface are earthquake faults. The Wenchuan Ms 8.0 earthquake might be attributed to the collision of the Yangtze block and the Qinghai–Tibet Plateau. The eastward obduction of the eastern edge of the Qinghai–Tibet Plateau and eastward subduction of its deeper part under the influence of the collision of the Indian, Pacific, and Philippine Plates with the Eurasia Plate might have caused the Longmen Mountains tectonic belt to cut the Moho and extend to the middle and upper crust; thus, creating high stress concentration and rapid energy release zone. 相似文献
19.
K. R. Richardson J. R. Smallwood R. S. White D. B. Snyder P. K. H. Maguire 《Tectonophysics》1998,300(1-4):159-180
We have mapped the transition from the continental Faroe block (the Faroe Islands and surrounding shelf) to the thickened oceanic crust of the Faroe–Iceland Ridge in the North Atlantic using the results of a detailed sea-to-land seismic profile with wide-angle to normal-incidence recordings of explosive and airgun shots fired at sea along the Faroe–Iceland Ridge. Interpretation of all available seismic and gravity data indicates that this aseismic ridge is composed of 30±3-km-thick oceanic crust, with a gradual transition to ancient continental crust from 100 to 40 km northwest of the Faroe Islands, close to the shelf edge. This confirms that the crust beneath the Faroe Islands, which may be up to 46 km thick, comprises continental material in agreement with previous seismic and geochemical results. Results suggest that the upper 5.2±0.7 km of the Faroe crust consists of Tertiary basalts generated during continental breakup, overlying the continental crust beneath. The lower crust, where seismic constraint is poor, may exhibit high seismic velocities (7.1–7.6 km s−1) which we attribute to underplating or intrusion by mafic melts during continental breakup in the early Tertiary. 相似文献
20.
西沙地块是南海岩石圈地壳拉伸减薄过程中发育于深水区的陆块,其保存了陆缘演化的重要信息。文章研究以西沙地块作为研究对象,基于研究区地质和地球物理资料,开展了地壳结构、盆地构造—地层分析和断层活动特征等研究。研究发现,西沙地块与其周缘的凹陷地壳结构具有显著的差异,西沙地块地壳厚度较大,发育了高角度断层控制的小型断陷盆地,基底断层活动一直可持续到T60地震界面发育时（~23 Ma）;而西沙地块周缘发育的是规模较大的拆离断层及其控制的强烈减薄陆壳。结合区域动力学事件,研究认为渐新世早期拆离断层在南海西北次海盆的活动导致了西沙地块北部的岩石圈地壳的减薄,而中新世早期拆离断层在南海西南次海盆构造位置的活动使西沙地块与南沙地块分离。文章研究成果不仅深化了西沙地块裂解规律的认识,而且对该区的油气勘探具有启示意义。 相似文献