西藏特提斯喜马拉雅白垩纪中期Cenomanian-Turonian期碳同位素偏移   总被引：5，自引：0，他引：5  

李祥辉  王成善  成鑫荣  崔杰  胡修棉 《地球科学》2005,30(3):317-327

过去大量关于白垩纪中期Cenomanian-Turonian晴期的古海洋及其界线时期缺氧事件研究的高分辨率碳氧同位素的实际材料绝大多数都来自深海钻探(DSDlP)、大洋钻探(0DP)和欧美的一些较深水盆地．通过对西藏南部地区(位处特提斯洋东南)同一层位高分辨率碳同位素分析,目的在于为Cenomanian-Turonian古海洋及全球事件的碳同位素响应提供西藏地区的对比材料,并试图就浅海相的变化情况进行探讨．西藏定日和岗巴地区的高分辨率碳同位素分析结果显示．δ^13C值在Cenomanian中晚期稳定,Cenomanian-Turonian界线时期快速高幅正偏,Turonian期持续负偏,这种长期变化趋势在特提斯甚至全球可以对比．深入研究还发现,Turonian中后期存在2个较大幅度的负偏凹陷区,与来自欧洲的相关资料在偏移时间和幅度方面惊人相似．对比分析表明,岗巴地区δ^13C值长期变化和短期波动幅度及步调与定日及全球其他地区存在一定差别,幅度差异可能与样品制备和成岩改造有关,步调不一致则可能受生物地层定位的影响．研究区近海一半远洋环境Cenomanian-Turonian界线时期未出现典型富有机质黑色页岩,说明δ^13C值极度正偏与黑色页岩的出现并非一对应．  相似文献   

古南海构造属性及其与特提斯和古太平洋构造域的关系     

鲁宝亮  王璞珺  梁建设  孙晓猛  王万银 《吉林大学学报(地球科学版)》2014,44(5):1441-1450

为了进一步理解南海地区前新生代的构造演化过程,明确古南海构造属性及其与特提斯和古太平洋构造域的关系,通过对古南海遗迹（蛇绿岩、蛇绿混杂岩以及俯冲增生带）的研究,结合周围陆区地质及古生物资料,将古南海的演化划分为4个阶段。①古特提斯残留海阶段（T₁-T₂）:古南海是在早-中三叠世的古特提斯残余海基础上发展而来,与古特提斯残余海是一个连续的演化过程。②古太平洋边缘海阶段（T₃）:晚三叠世,由于古特提斯洋的全面关闭,古南海主要受古太平洋的影响。③中特提斯与古太平洋叠加影响阶段（J-K₁）:早侏罗世,古南海开始扩张,并受中特提斯和古太平洋叠加影响;晚侏罗世,南沙地块向华南大陆开始漂移,古南海进一步强烈扩张。④俯冲消亡阶段（K₂末期-E）:晚白垩世,南沙地块开始裂离华南大陆,古南海开始向南俯冲;至始新世,伴随着新南海的扩张,古南海加速消亡于巽他地块之下,并在南海南部地区形成了卢帕尔线蛇绿岩带以及一系列的俯冲增生带。  相似文献   

青藏高原形成和演化的古地磁研究进展综述   总被引：1，自引：0，他引：1  

孙知明  曹勇  李海兵  裴军令  仝亚博  叶小舟  吴百灵  曹新文  刘晨光 《地球学报》2019,40(1):17-36

20世纪80年代以来,特别是最近10年,中外古地磁学者在青藏高原获得了一大批古地磁数据,从构造古地磁角度,重建了青藏高原诸块体(喜马拉雅、拉萨地块、羌塘地块)的碰撞拼合过程,探讨了上述块体碰撞所造成的青藏高原陆内构造缩短量和变形模式。本文对近30年来青藏高原古地磁研究进行了回顾和总结,并在此基础上试图重建了中、新特提斯洋的演化过程,进一步探讨青藏高原形成和演化的动力学背景。  相似文献   

The northern Qiangtang Block rapid drift during the Triassic Period: Paleomagnetic evidence     

《地学前缘(英文版)》2019,10(6):2313-2327

As one of the pivotal Gondwana–derived blocks, the kinematic history of the northern Qiangtang Block (in the Tibetan Plateau) remains unclear, mainly because quantitative paleomagnetic data to determine the paleoposition are sparse. Thus, for this study, we collected 226 samples (17 sites) from Triassic sedimentary rocks in the Raggyorcaka and Tuotuohe areas of the northern Qiangtang Block (NQB). Stepwise demagnetization isolated high temperature/field components from the samples. Both Early and Late Triassic datasets passed field tests at a 99% confidence level and were proved to be primary origins. Paleopoles were calculated to be at 24.9°N and 216.5°E with A₉₅ = 8.2°(N = 8) for the Early Triassic dataset, and at 68.1°N, 179.9°E with A₉₅ = 5.6° (N = 37) for the Late Triassic, the latter being combined with a coeval volcanic dataset published previously. These paleopoles correspond to paleolatitudes of 14.3°S±8.2° and 29.9°N±5.6°, respectively. Combining previously published results, we reconstructed a three-stage northward drift process for the NQB. (1) The northern Qiangtang Block was located in the subtropical part of the southern hemisphere until the Early Triassic; (2) thereafter, the block rapidly drifted northward from southern to northern hemispheres during the Triassic; and (3) the block converged with the Eurasian continent in the Late Triassic. The ∼4800 km northward movement from the Early to Late Triassic corresponded to an average motion rate of ∼11.85 cm/yr. The rapid drift of the NQB after the Early Triassic led to a rapid transformation of the Tethys Ocean.  相似文献   

泥盆纪右江盆地演化与层序充填响应   总被引：4，自引：0，他引：4  

侯明才  陈洪德  田景春 《地层学杂志》2005,29(1):62-70

早泥盆世时东特提斯洋沿金沙江—哀牢山缝合带逐渐向东打开 ,广南—靖西等基底断裂与板块边界断裂——金沙江—哀牢山断裂带平行展布和同步演化 ,边界断裂的向东开裂扩张 ,广南—靖西等基底断裂活动亦逐渐加剧 ,导致右江盆地由陆内裂陷盆地向被动陆缘裂谷盆地演化。据构造活动的强弱和盆地充填物的特征 ,将右江盆地的演化分为洛赫科夫期至布拉格期的陆内裂陷盆地阶段、埃姆斯期—艾费尔期的拉张发展阶段、吉维期至弗拉斯期的强烈拉张阶段、法门期的充填补齐阶段 ,后三者组成被动陆缘裂谷盆地阶段。不同次级盆地的不同阶段 ,其构造沉降和海平面升降幅度不一样 ,层序发育样式各异 ,其中孤立碳酸盐岩台地层序发育主要受控于相对海平面变化和碳酸盐生产率 ,而台盆层序发育则受构造活动、海平面变化、台缘重力流和沉积物供应的综合影响。据此 ,将该区泥盆系划分为两个 级层序 ,18个 级层序 ,并建立了各演化阶段的层序充填模型。这种层序充填的差异性正是对盆地构造演化和全球海平面变化的响应。  相似文献   

Tectonic and Hydrocarbon Accumulation Elements Characteristics of the Tethyan Realm in South China   总被引：1，自引：0，他引：1  

YU Yixin  TANG Liangjie  YIN Jinyin  DONG Li  WANG Pengwan  ZHOU Yan 《《地质学报》英文版》2009,83(6):1214-1223

Abstract: The evolution of the global Tethys Sea can be classified into three stages, Proto-Tethys, Paleo-Tethys and Neo-Tethys. The Tethyan realm has distinctive features of zonations and segmentations along north-south and east-west, respectively, and has variable richness in oil and gas. The petroleum geological conditions of Tethys are complicated, partly represented by multi-layer of source and seal rocks, and reservoirs. The hydrocarbon accumulation elements and periods of the Tethyan realm show gradually younger from west to east and north to south. South China is located in the north belt and Yangtze segment of the Tethyan realm, and its polycyclic tectonic movements were governed by the Tethyan and Pacific realms. The blocks in South China rotated clockwise and counter-clockwise during their drift northward from Gondwana. The belts and segmentations of Tethys in South China are also clear, with six tectonic belts including: Chuxiong-Sichuan; middle Guizhou-Hunan-Hubei; lower Yangtze; Xuefeng-Jiangnan; Guangxi-Hunan-Jiangxi; and Cathaysia. Numerous faults, including compressional, compressional-shear, extensional, extensional-shear and shear are well developed in South China. The fault strikes are mainly NE, NW and NS, in which the NE is the dominant direction. Lower, middle and upper hydrocarbon assemblages, respectively corresponding to Proto-, Paleo- and Neo-Tethys, formed in the Tethyan realm of South China with the lower and middle having excellent hydrocarbon accumulation conditions. An integrated analysis of tectonic evolution, superimposed deformation and later hydrocarbon preservation shows that during the Neo-Tethyan stage in South China, continental sediments were deposited and experienced intense tectonic deformation, which had resulted in different hydrocarbon pool-forming features from those of the Neo-Tethyan realm.  相似文献   

祁漫塔格造山带——青藏高原北部地壳演化窥探   总被引：2，自引：0，他引：2  

于淼  丰成友  何书跃  赵梦琪  赵一鸣  李大新  瞿泓滢  刘建楠  王辉  周建厚  钟世华 《地质学报》2017,91(4):703-723

祁漫塔格是东昆仑造山带的一个分支,位于青藏高原中北部,夹持于柴达木盆地和库木库里盆地中间,向西被阿尔金走滑断裂错段。从元古代到早中生代,由于受到多期、多阶段大洋俯冲和关闭影响,导致不同地体间发生碰撞拼贴和大陆增生过程,并由此引发一系列的岩浆事件。祁漫塔格造山带内发育新元古代花岗岩(1000~820 Ma)是对Rodinia超大陆形成的响应。以阿达滩和白干湖逆冲断裂为界,划分为南、北祁漫塔格两地体。北祁漫塔格地体作为活动大陆边缘,发育大量的早古生代与俯冲有关的花岗岩和VA型蛇绿岩;南祁漫塔格地体最初为洋内俯冲形成的原始大洋岛弧,发育早古生代SSZ型蛇绿岩、岛弧拉斑玄武岩和钙碱性火山岩。随着持续俯冲,年轻岛弧伴伴随地壳加厚转变为成熟岛弧。南、北祁漫塔格地体间的碰撞(弧-陆碰撞)可能发生在晚志留世(422Ma),并持续到早泥盆世(398Ma)。在此期间(422~389Ma),南祁漫塔格地体内发育一系列同碰撞型花岗岩;北祁漫塔格地体内发育一系列的大洋岛弧花岗岩。南祁漫塔格作为外来地体,碰撞拼贴对于大陆边缘、大陆增生意义重大。之后,南、北祁漫塔格地体进入后碰撞环境并发育一系列板内花岗岩。此外,伸展导致造山带垮塌,发育中泥盆统磨拉石建造。碰撞使得海沟后退,海沟阻塞导致俯冲减弱甚至停止,因而产生了石炭-二叠纪(357~251 Ma)岩浆活动缺口。古特提斯祁漫塔格洋的最终关闭可能始于晚二叠世,使得库木库里微板块拼贴于大陆边缘;碰撞抬升导致缺失上二叠统-中三叠统地层。早中三叠世(251~237 Ma)由于碰撞,俯冲大洋板片回转,之后断离,软流圈地幔物质沿岩石圈地幔通道上涌,使得新生下地壳部分熔融;到了晚三叠世,大规模岩石圈地幔和下地壳物质拆沉,导致古老地壳物质发生熔融,形成了一系列后碰撞背景下的钙碱性和碱性花岗岩。  相似文献   

西昆仑甜水海地块南屏雪山早古生代花岗岩地球化学、Hf同位素特征及其壳幔岩浆作用   总被引：4，自引：0，他引：4  

胡军  王核  慕生禄  王敏  候学文 《地质学报》2017,91(6):1192-1207

南屏雪山早古生代花岗岩体位于西昆仑甜水海地块东段,主要岩性为中粒含斑黑云母二长花岗岩(485Ma)和中细粒黑云母二长花岗岩(528Ma)。化学组成上,两者均具有高硅、富碱,贫TFe2O3、MgO和CaO的特征,属高钾钙碱性弱过铝质系列;微量和稀土元素组成上,两者均富Rb、Th、U、K、Pb和轻稀土,贫Ba、Sr、Nb、Ta、Ti和P,Rb/Sr、Rb/Ba、Nb/Ta和Y/Yb比值高,具有明显的Eu负异常,其Zr、Nb、Ce、Y等高场强元素均较之典型A型花岗岩偏低,综合地质地球化学特征的判别表明南屏雪山花岗岩应属高分异的I型花岗岩。中粒含斑黑云母二长花岗岩和中细粒黑云母二长花岗岩均具有较均一的正εHf(t)值(0.9~5.3和1.4~5.6)和中元古代的二阶段模式年龄TDM2(1118~1398Ma和1136~1396Ma),相似的地球化学特征和锆石Hf同位素组分暗示两者可能是同源岩浆演化的产物。结合区域构造演化历史,推测在早古生代原特提斯洋存在双向俯冲,南屏雪山早古生代花岗岩则是在早寒武世-早奥陶世(528~485 Ma)原特提斯洋持续向南的俯冲消减-碰撞造山过程中,诱导幔源岩浆上涌底侵下地壳,诱发区内中元古代新生地壳物质至少两次部分熔融(早寒武世和早奥陶世),并经历一定程度的分离结晶作用而形成的。  相似文献   

Multiple Mesozoic porphyry-skarn Cu (Mo–W) systems in Yidun Terrane,east Tethys: Constraints from zircon U–Pb and molybdenite Re–Os geochronology     

《Ore Geology Reviews》2017

Porphyry Cu ± Mo ± Au deposits typically formed in volcanoplutonic arcs above subduction zones. However, there is increasing evidence for the occurrence of porphyry deposits related to magmas generated after the underplating arc has ceased. Post-subduction lithospheric thickening, lithospheric extension, or mantle lithosphere delamination could trigger the remelting of subduction-modified arc lithosphere and lead to the formation of post-subduction porphyry deposits. The NNW-trending Yidun Terrane, located in the eastern Tethys, experienced subduction of Garze–Litang oceanic plate (a branch of the Paleotethys) in the Late Triassic and witnessed two mineralization events respectively associated with the ca. 215 Ma arc-related intermediate–felsic porphyries and the 88–79 Ma mildly-alkaline granitic porphyries. It is, therefore, an ideal place to investigate the genetic linkage between the subduction-related porphyry deposits and post-subduction porphyry deposits. Our new in situ zircon U–Pb dating of the two granitic intrusions (biotite granite, 213.4 ± 0.9 Ma; monzogranite porphyry, 86.0 ± 0.4 Ma) in the Xiuwacu district, the molybdenite Re–Os age (84.7 ± 0.6 Ma) of the mineralization, and previously published geochronological data, together show the spatially overlapping distribution of the multiple Mesozoic porphyry systems in the Late Triassic Yidun arc system. Furthermore, the arc-like elemental signatures and the mixed Sr–Nd–Hf isotopic signatures of the Late Cretaceous ore-related porphyries (i.e., originating from a mixed components between the ∼215 Ma juvenile arc crust and the Mesoproterozoic mafic lower crust) indicate a genetic linkage between the Late Triassic and Late Cretaceous porphyry systems. This suggests that the remelting of underplated arc-related mafic rocks formed during the subduction of the Garze–Litang Ocean could be responsible for the mixing between the mantle-derived components and the Mesoproterozoic lower crustal materials, when post-subduction transtension occurred in the Late Cretaceous. The formation of the Late Cretaceous porphyry–skarn Cu–Mo–W deposits could most likely be related to the remelting of Late Triassic residual sulfide-bearing Cu-rich cumulates in the subduction-modified lower crust that triggered by the Late Cretaceous transtension.  相似文献   

The Loppio Oolitic Limestone (Early Jurassic,Southern Alps): A prograding oolitic body with high original porosity originated by a carbonate platform crisis and recovery     

《Marine and Petroleum Geology》2017

The Loppio Oolitic Limestone is a lithostratigraphic unit of the Early Jurassic Trento Platform in the Southern Alps, Northern Italy, which deposited over an area of ca. 3500 km². It appears as a roughly tabular or wedge-shaped sedimentary body with thickness gradually increasing from 0 to ca. 100 m toward the western platform margin. We investigated the sedimentology, petrography and bulk carbonate carbon isotope geochemistry of the Loppio Oolitic Limestone in order to shed light on its depositional setting and origin. The Loppio Oolitic Limestone is made almost exclusively of oolitic grainstone, and can be subdivided in two parts. In the lower part, ooids are poorly sorted and sedimentary structures are scarce or absent. In the upper part, sorting becomes good and sedimentary structures are common. The vertical succession of sedimentary structures and the upward increase in sorting suggest a shallowing upward trend within the oolite. A reddened surface, meteoric cements and dinosaur footprints occur at the top of the unit, testifying for a subaerial exposure which is also confirmed by carbon and oxygen stable isotopic data. In terms of sequence stratigraphy, the Loppio Oolitic Limestone represents a Highstand Systems Tract, bounded at the top by a subaerial exposure surface. Bulk carbonate stable carbon isotope curves across the Loppio Oolitic Limestone from 7 stratigraphic sections could be correlated over distances of tens of km on the whole Trento Platform. This correlation suggests that the deposition of ooids was nearly synchronous across the platform. A negative excursion of carbon isotopes with magnitude of ca. 1‰ VPDB was identified within a lime mudstone unit (“Nodular lithozone” of the Monte Zugna Formation) immediately below the Loppio Oolitic Limestone, which can be correlated to a global perturbation of the carbon cycle in the mid-Sinemurian. The flooding of a wide area of formerly peritidal carbonate platform below the wave base was interpreted as due to an ecological crisis that caused a drop of carbonate production. We suggest that the subsequent recovery of carbonate production is marked by the shallowing upward succession of the Loppio Oolitic Limestone, which quickly occupied the accommodation space formed in consequence of the crisis, thus preventing the platform drowning. The Loppio Oolitic Limestone deposited as an initially highly porous oolitic sand that was then topped by a clayey interval (base of the Rotzo Formation), giving origin to a structural and stratigraphic configuration that could be favourable for the accumulation of hydrocarbons in the subsurface. The recurrence of similar facies superpositions, formed in consequence of perturbations of the carbon cycle with documented climatic effects, is discussed with regard to the Tethysian record of Mesozoic carbonate platforms.  相似文献