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1.
《International Geology Review》2012,54(3):189-215
This paper is a synthesis of structural and geochronological data from eastern Mediterranean ophiolitic metamorphic rocks and surrounding units to interpret the intra‐oceanic subduction and ophiolite emplacement mechanism. Metamorphic rocks occur as discontinuous tectonic slices at the base of the ophiolites, generally between the peridotite tectonites and volcanic‐sedimentary units, and locally in fault zones in the overlying peridotites. They consist essentially of amphibolite, and in lesser quantities, micaschist, quartzite, epidotite and marble. Geological and geochronological data indicate that recrystallization of the metamorphic rocks occurred in the oceanic environment. The contact between the metamorphic rocks and the hanging‐wall is parallel to the foliation of the metamorphic rocks, and is interpreted as the fossil plane of intra‐oceanic subduction. Structural relationships suggest that intra‐oceanic subduction was situated between two lithospheric blocks separated by an oceanic fracture zone. Therefore the Neotethyan ophiolites with metamorphic soles represent the remnants of the overriding oceanic lithosphere's training slices of the metamorphic rocks at the base. In the Anatolian region, radiometric dating of metamorphic rocks from the Taurus and Izmir‐Ankara‐Erzincan zone ophiolites yield nearly identical ages. Besides, palaeontological and structural data indicate coeval opening and similar oceanic ridge orientation. Consequently it is highly probable that Taurus and Izmir‐Ankara‐Erzincan zone ophiolites represent fragments of the same oceanic lithosphere derived from a single spreading zone. Palaeontological data from underlying volcanic and sedimentary units point out that the opening of the Neotethyan ocean occurred during Late Permian‐Middle Triassic time in the Iranian‐Oman region, during Middle Triassic in Dinaro‐Hellenic area, and finally during Late Triassic in the Anatolian region. Radiometric dating of the metamorphic rocks exhibit that the intra‐oceanic thrusting occurred during late Lower‐early Late Jurassic for Dinaro‐Hellenic ophiolites, late Lower‐early Late Cretaceous for Anatolian, Iranian and Oman ophiolites well before their obduction on the Gondwanian continent. Neotethyan ophiolites were obducted onto various sections of the Gondwanian continent from late Upper Jurassic to Palaeocene time, Dinaro‐Hellenic ophiolites during late Upper Jurassic‐early Lower Cretaceous onto the Adriatic promontory, Anatolian, Iranian and Oman ophiolites from late Lower Cretaceous to Palaeocene onto the Aegean, Anatolian and Arabic promontories. 相似文献
2.
江汉叠合盆地地处扬子地区中部,夹持于秦岭--大别造山带与江南造山带中段之间,是中生代中期以来在扬子浅海台地基础上发育起来的典型海陆交互相-陆相叠合盆地,其中充填了厚逾10000m的中三叠世-新近纪陆源碎屑岩系。据印支期以来的造山活动历程与成盆演化特点,将盆山耦合过程划分为造山前期、主造山期、造山后期与非造山期4个阶段,将盆地充填层序划分为陆架边缘、前陆、断陷和坳陷4个(盆地世代)超层序。依据盆内沉积物碎屑组份分析,发现中三叠世江南造山带进入强造山活动期,白垩纪末进入造山带坍塌后的活动平静期;秦岭--大别造山带的主造山活动阶段为晚三叠-早侏罗世,古近纪末处于非造山活动相对平静阶段。盆区整体呈现东部造山活动早,山带隆升早,持续时间长,剥露地层较快较早进入变质岩层段;西部造山活动时间晚,隆升时间相对较晚,剥露地层在早侏罗世初期才依次切入变质岩层段;盆地南、北缘山带总体呈现多幕式差异隆升过程。 相似文献
3.
The Armutlu Peninsula and adjacent areas in NW Turkey play a critical role in tectonic reconstructions of the southern margin of Eurasia in NW Turkey. This region includes an inferred Intra-Pontide oceanic basin that rifted from Eurasia in Early Mesozoic time and closed by Late Cretaceous time. The Armutlu Peninsula is divisible into two metamorphic units. The first, the Armutlu Metamorphics, comprises a ?Precambrian high-grade metamorphic basement, unconformably overlain by a ?Palaeozoic low-grade, mixed siliciclastic/carbonate/volcanogenic succession, including bimodal volcanics of inferred extensional origin, with a possibly inherited subduction signature. The second unit, the low-grade
znik Metamorphics, is interpreted as a Triassic rift infilled with terrigenous, calcareous and volcanogenic lithologies, including basalts of within-plate type. The Triassic rift was unconformably overlain by a subsiding Jurassic–Late Cretaceous (Cenomanian) passive margin including siliciclastic/carbonate turbidites, radiolarian cherts and manganese deposits. The margin later collapsed to form a flexural foredeep associated with the emplacement of ophiolitic rocks in Turonian time. Geochemical evidence from meta-basalt blocks within ophiolite-derived melange suggests a supra-subduction zone origin for the ophiolite. The above major tectonic units of the Armutlu Peninsula were sealed by a Maastrichtian unconformity. Comparative evidence comes from the separate Almacık Flake further east.Considering alternatives, it is concluded that a Mesozoic Intra-Pontide oceanic basin separated Eurasia from a Sakarya microcontinent, with a wider Northern Neotethys to the south. Lateral displacement of exotic terranes along the south-Eurasian continental margin probably also played a role, e.g. during Late Cretaceous suturing, in addition to overthrusting. 相似文献
4.
国内外一些学者认为秦岭是一个印支碰撞造山带.但迄今为止,秦岭尚未发现三叠纪或古生代延续到三叠纪的洋盆存在的任何痕迹.秦岭泥盆系-三叠系为滨、浅海相沉积,没有远洋沉积,更没有镁铁质和超镁铁质岩石及与之密切相关的放射虫硅质岩组成的蛇绿岩套.泥盆系与下伏地质体之间有一个清楚的区域性角度不整合.商丹断裂并不是印支期,而是加里东期的板块缝合带;其两侧,中朝板块南缘和扬子板块北缘均有十分清楚的加里东造山作用的记录.沉积于扬子板块北缘的中上泥盆统刘岭群的放射性铅同位素组成与北秦岭相近,碎屑锆石年龄谱系亦证明其物质主要来自中朝板块南缘的北秦岭造山带.所谓勉略印支缝合带中的勉略和三里岗蛇绿混杂岩中的镁铁质岩,同位素测年均为元古代之产物,后者又被南华系-震旦系沉积覆盖.所谓勉略缝合带,实为一区域性大断裂带.早古生代,其北侧属扬子板块北部被动边缘;南侧为扬子板块核心部分的扬子准地台(小克拉通).所以,秦岭的印支造山作用,并不是洋盆消失后的陆陆碰撞造山作用,而是海盆消失后的中朝与扬子2个小陆块间逆冲-叠覆造山作用.作为秦岭东延的大别山超高压变质带被认为是秦岭印支碰撞造山的重要证据之一,但大别山超高压变质岩是在造山作用过程中动态超高压条件下形成的,仅用简单的静岩压力来计算其形成深度,显然是不符合实际情况的.野外地质观察、构造地质学、变质岩石学、同位素地质学、地球化学、地球物理学以及物理实验等方面的实际资料和研究结果均说明超高压变质作用并不是在上地幔而是在地壳内进行的.南秦岭-大别山的地壳构造层次,上地壳自上而下依次为:未变质的沉积岩层、绿帘-蓝片岩层、高压变质岩层、超高压变质岩层;下地壳为未卷入超高压变质作用的麻粒岩相-高角闪岩相变质杂岩.含柯石英的超高压单位只是位于上地壳下部的厚约10～12km的席状构造岩片.初步认为上地壳这一从低压到高压再到超高压的构造系统,是印支造山期间,南秦岭-大别山的上地壳以下地壳顶部为主剪切滑动面,多层次剪切作用造成的.上地壳下部的超高压变质岩,则可能是强烈剪切引起的频繁地震的震源区瞬时超高压作用的结果. 相似文献
5.
羌塘盆地是我国陆域上面积最大的海相盆地,前人对该盆地构造演化过程及其油气远景存在截然不同的观点。以最近完成的1︰ 5万地质调查为基础,本文再次讨论了南羌塘盆地构造演化过程及其油气远景。羌塘盆地中央近东西向的羌中隆起山脉将羌塘盆地分为南、北两部分。最近的研究表明,在寒武-奥陶纪之交,南、北羌塘块体被古大洋分隔开。北羌塘盆地南缘形成的晚三叠-早侏罗世的那底岗日组火山岩,其上部为流纹岩,表明晚三叠世南羌塘块体北向俯冲于北羌塘块体之下,在南羌塘块体北部形成了富含有机质的前陆盆地。南羌塘盆地南缘发育一套代表成熟海盆的侏罗纪复理石建造,表明南羌塘南部地区在早侏罗世具有被动大陆边缘的特点,随着南部班公-怒江洋的扩张,在南、北羌塘块体内分别沉积了侏罗纪-早白垩世的浅海相地层,以富含有机质礁灰岩为特征。盆地内部孕育了巨厚的晚白垩-古新世陆源碎屑岩,不整合覆盖于早期海相沉积岩之上,表明在该时期南羌塘块体逐渐从被动大陆边缘海相盆地转变为陆相盆地。新生代时期,印度与亚洲大陆持续汇聚,南羌塘盆地南向逆冲于拉萨块体之上,盆地内发育了多条大型逆冲断裂带,再次将盆地内部的上三叠统、侏罗系、白垩系富含有机质的海相礁灰岩深埋,这有利于油气资源的生成与保存。横跨南羌塘盆地的构造剖面显示盆地内部主要大型逆冲断裂带之间,构造变形较弱,发育宽缓的向斜构造,向斜核部发育新生代陆相地层,推测该新生代陆相地层之下保存有深埋的富含有机质的海相地层,因此,南羌塘盆地逆冲断裂带下盘和宽缓向斜核部区域可能具有良好的油气资源前景。 相似文献
6.
藏南萨迦拉轨岗日变质核杂岩的厘定及其成因 总被引：24，自引：4，他引：24
藏南拉轨岗日带出露一系列穹状隆起，具有变质核杂岩体典型的3层结构型式。变质核由拉轨岗日岩群变质杂岩及侵入其中的花岗岩组成，围绕变质核发育多层顺层拆离断层，盖层主要为晚古生代和中生代浅变质岩石。拉轨岗日变质核杂岩与高喜马拉雅变质核杂岩之间存在密切的时空联系，是喜马拉雅造山作用及相关隆升作用过程中发生热隆伸展的结果。 相似文献
7.
A compilation of available palaeomagnetic data from the Troodos (Cyprus) and Baër–Bassit (Syria) ophiolitic terranes of the eastern Mediterranean Tethyan orogenic belt is presented. The ophiolites represent fragments of oceanic lithosphere generated at a Neotethyan spreading axis in the Late Cretaceous, although debate continues over the tectonic setting of this spreading axis and its position within the eastern Mediterranean palaeogeography. Two types of model reconstructions have been proposed: Type 1—the ophiolites formed in a southerly Neotethyan basin by spreading above an oceanic subduction zone. The Baër–Bassit ophiolite was then emplaced a relatively short distance (tens of kilometers) southwards on to the Arabian continental margin, leaving the Troodos ophiolite isolated in an intra-oceanic setting to the west; and Type 2—the ophiolites formed in a northerly Neotethyan basin by spreading at a ‘normal’ oceanic ridge, with subsequent large-scale thrusting (hundreds of kilometers) to the south of emplaced ophiolites over microcontinental fragments to reach their present positions. Palaeomagnetic determination of the palaeolatitude of the Neotethyan spreading axis is, therefore, of considerable interest.Previous palaeomagnetic analyses have demonstrated the presence of significant, and in some cases extreme, relative tectonic rotations of a variety of origins in both ophiolites. To allow palaeomagnetic data from these rotated units to be combined, an inclination-only formulation of the palaeomagnetic tilt test is employed. This provides unequivocal evidence that both ophiolites retain pre-deformational remanent magnetizations, which are interpreted as original ocean-floor magnetizations acquired close to the time of crustal formation in the Late Cretaceous. The mean inclinations of 37.0±2.6° for the Troodos terrane and 41.1±3.4° for the Baër–Bassit terrane indicate respective palaeolatitudes for the spreading axes of 20.6°N±1.8° and 23.6°N±2.5°, consistent with a Late Cretaceous position between the Arabian and Eurasian margins. These data, together with a well-defined palaeolatitude of 25.5°N±4.5° for the eastern Pontides previously reported in the literature, provide constraints which must be incorporated in any successful tectonic reconstruction of the eastern Mediterranean Tethys. The implications of these constraints for Type 1 and 2 models are discussed using a series of plate tectonic cross-sections constructed along a line extending northwards from the Arabian continental margin. In the absence of palaeomagnetic data from Late Cretaceous rocks of the eastern Taurides, however, it is presently impossible to use these palaeolatitudinal constraints to resolve the root zone debate on a purely palaeomagnetic basis. Solutions which satisfy the constraints may be found for both types of model reconstruction. Additional, published field-based geological considerations, however, strongly support models in which the Troodos and Baër–Bassit (and other southerly) ophiolites were generated in a southern Neotethyan basin, rather than those involving generation in a northerly basin and subsequent large-scale thrust displacement to the south. 相似文献
8.
弯岛湖蛇绿混杂岩带是金沙江缝合带西段的重要组成部分。蛇绿岩混杂于上三叠统变质碎屑岩夹变质火山岩中,成份主要为镁铁质-超镁铁质杂岩,岩石类型有变质橄榄岩、变质堆晶质辉长岩及其伴生的岛弧型花岗岩系。岩石化学及地球化学特征表明:蛇绿岩主要为低Ti(岛弧-弧后)型、富集型洋中脊(E-MORB)拉斑玄武岩;与之共(伴)生的基性喷出岩、辉绿岩脉属板内洋岛型裂谷型碱性玄武岩及其过渡类型系列。在变质辉长岩获得全岩Sm-Nd等时线年龄值为232±11Ma,代表了镁铁质-超镁铁质杂岩的形成年龄,可能为洋壳初始俯冲变质的时间。在蛇绿岩上覆的硅质岩中发现有中三叠世拉丁晚期至晚三叠世卡宁早期的放射虫化石,表明弯岛湖镁铁质-超镁铁质杂岩可能形成于中三叠世多岛洋盆或弧后盆地构造环境。 相似文献
9.
Geodynamic evolution of ophiolites from Albania and Greece (Dinaric-Hellenic belt): one, two, or more oceanic basins? 总被引：1，自引：0，他引：1
Valerio Bortolotti Marco Chiari Michele Marroni Luca Pandolfi Gianfranco Principi Emilio Saccani 《International Journal of Earth Sciences》2013,102(3):783-811
All the geological constraints for an exhaustive reconstruction of the Triassic to Tertiary tectonic history of the southern Dinaric-Hellenic belt can be found in Albania and Greece. This article aims to schematically reconstruct this long tectonic evolution primarily based on a detailed analysis of the tectonic setting, the stratigraphy, the geochemistry, and the age of the ophiolites. In contrast to what was previously reported in the literature, we propose a new subdivision on a regional scale of the ophiolite complexes cropping out in Albania and Greece. This new subdivision includes six types of ophiolite occurrences, each corresponding to different tectonic units derived from a single obducted sheet. These units are represented by: (1) sub-ophiolite mélange, (2) Triassic ocean-floor ophiolites, (3) metamorphic soles, (4) Jurassic fore-arc ophiolites, (5) Jurassic intra-oceanic-arc ophiolites, and (6) Jurassic back-arc basin ophiolites. The overall features of these ophiolites are coherent with the existence of a single, though composite, oceanic basin located east of the Adria/Pelagonian continental margin. This oceanic basin was originated during the Middle Triassic and was subsequently (Early Jurassic) affected by an east-dipping intra-oceanic subduction. This subduction was responsible for the birth of intra-oceanic-arc and back-arc oceanic basins separated by a continental volcanic arc during the Early to Middle Jurassic. From the uppermost Middle Jurassic to the Early Cretaceous, an obduction developed, during which the ophiolites were thrust westwards firstly onto the neighboring oceanic lithosphere and then onto the Adria margin. 相似文献
10.
桂西南那坡盆地位于八布-Song Hien构造带,发育早-中三叠世岩浆岩和巨厚海相碎屑岩系,是研究华南地块南缘古特提斯造山过程的关键地区。本文对那坡盆地中三叠统河口组中-上部的两套沉凝灰岩开展了详细的岩石学、地球化学和锆石U-Pb-Hf同位素分析研究。两件沉凝灰岩样品LA-ICP-MS锆石U-Pb定年结果分别为240.6±1.0Ma和236.3±0.8Ma,指示河口组碎屑岩沉积时代为中三叠世拉丁期,部分为晚三叠世卡尼期早期。全岩地球化学结果显示,该沉凝灰岩属于亚碱性英安质,富集轻稀土(LREEs)和大离子亲石元素(LILEs)、Rb、Th和U,亏损高场强元素(HFSEs),具有显著的Nb、Ta和Ti负异常。沉凝灰岩锆石具有较低的ε_(Hf)(t)值(-18.6~-6.3)和较老的地壳模式年龄(t_(DM)^(C)=1664~2434Ma),结合锆石微量元素特征认为其形成于俯冲环境。整体上,那坡盆地河口组沉凝灰岩表现出俯冲作用形成的岛弧火山岩地球化学特征,推断其来源于桂西南凭祥地区的中-晚三叠世酸性火山岩。结合已有区域地质调查成果,认为华南地块南缘八布-Cao Bang古特提斯分支洋盆于晚二叠世至晚三叠世早期向北俯冲,随后自西向东呈“剪刀”式逐渐闭合。华南地块与北越地块完全碰撞拼合的时间发生在晚三叠世中晚期。 相似文献
11.
Zhang Nuo Wang ChangBing Liu ZhengHong Xu ZhongYuan Li Gang Xuan YuFei Gao Yu Wang Chen 《岩石学报》2022,(8):2323-2344
LA-ICP-MS U-Pb dating, whole -rock geochemistry and Hf isotopic analyses for the Jianshanzi volcanic rocks in the Kaiyuan area are presented to explore the Late Paleozoic -Early Mesozoic tectonic evolution history of the eastern segment of the northern margin of the North China block. The detailed research indicates that the protolith of Jianshanzi metamorphic volcanic rocks includes rhyolite, dacite and andesite, they are calc-alkaline series and metaluminous-weak peraluminous rocks. According to the zircon U-Pb dating, the metamorphic rhyolite and metamorphic andesite formed in the Late Permian (256. 1 +/- 1. 5Ma, 252.4 +/- 1. 7Ma) and the Late Triassic (222. 4 +/- 1. 8Ma, 227. 9 +/- 1. 2Ma), respectively. They are characteristized by enrichment in light rare earth elements and large ion lithophile elements, and depletion of heavy rare earth elements and high field strength elements. Metamorphic rhyolite has an obvious negative Eu anomaly with epsilon(Hf) ( t) values of 10. 83 + 8. 10 and the second -stage model are 698 similar to 1967Ma. They are mainly due to the partial melting of the juvenile basaltic lower crust and the contamination of a small amount of ancient crustal materials. Metamorphic andesite has no obvious Eu anomaly, and the epsilon(Hf)( t) value and the second -stage model are +4.54 similar to + 6. 79 and 825 similar to 968 Ma, which may be the product of partial melting of basic lower crust. There are two periods of magmatism in Jianshanzi volcanic rocks: Late Permian -Early Triassic (247 similar to 256Ma) and Late Triassic (similar to 225Ma). The material composition of the Jianshanzi volcanic rocks is characterized by different times and different tectonic backgrounds. It is comprehensively believed that the eastern segment of the northern margin of the North China block was in an active continental margin tectonic environment during the Permian, and the Palaeo-Asian Ocean subducted in both directions; Mantle -derived magma ascends and emplaces, forming a nascent crust and causing crustal thickening. The Paleo-Asian Ocean finally closed in the early Middle Triassic, and the impact of collisional orogeny may have continued until the early Late Triassic. 相似文献
12.
青藏高原东缘的昌都地块是连接青藏高原腹地和藏东南三江-印支地区的关键区域,发育有较完整的晚古生界,以三叠系、侏罗系-白垩系广泛分布为特色;但其前寒武纪基底岩系出露较少,主要以宁多岩群(Pt_(1-2)Nd.)和草曲群(Pt_(3)C)为代表。本文针对昌都地块东南缘贡觉地区出露的一套被前人称为“宁多岩群”的中深变质岩系,开展了系统的野外地质调查、显微薄片分析、锆石U-Pb年代学等研究工作,认为该套中深变质岩系属于一套变质杂岩,其岩石组合既包括了原岩沉积时代不早于奥陶纪的片麻岩、变粒岩和大理岩等副变质岩,又包含了原岩时代分别为中二叠世的斜长角闪岩和中三叠世花岗质片麻岩等正变质岩。其原岩时代特征与昌都地块北缘的宁多岩群有较大差别,不应当归属为昌都地块的前寒武纪结晶基底。结合片麻岩的变质新生云母类矿物Ar-Ar测年数据和变质后期侵入的闪长玢岩脉锆石U-Pb年龄,认为贡觉地区出露的中深变质岩的变质时代为ca.260~244Ma(P_(2)-T_(2))。该期发生在昌都地块东南缘的角闪岩相变质作用,是金沙江古特提斯洋向西俯冲-碰撞的构造响应。 相似文献
13.
The Anarak, Jandaq and Posht-e-Badam metamorphic complexes in central Iran: New geological data, relationships and tectonic implications 总被引：3，自引：0，他引：3
The Anarak, Jandaq and Posht-e-Badam metamorphic complexes occupy the NW part of the Central-East Iranian Microcontinent and are juxtaposed with the Great Kavir block and Sanandaj-Sirjan zone. Our recent findings redefine the origin of these complexes, so far attributed to the Precambrian–Early Paleozoic orogenic episodes, and now directly related to the tectonic evolution of the Paleo-Tethys Ocean. This tectonic evolution was initiated by Late Ordovician–Early Devonian rifting events and terminated in the Triassic by the Eocimmerian collision event due to the docking of the Cimmerian blocks with the Asiatic Turan block.
The “Variscan accretionary complex” is a new name we proposed for the most widely distributed metamorphic rocks connected to the Anarak and Jandaq complexes. This accretionary complex exposed from SW of Jandaq to the Anarak and Kabudan areas is a thick and fine grain siliciclastic sequence accompanied by marginal-sea ophiolitic remnants, including gabbro-basalts with a supra-subduction-geochemical signature. New 40Ar/39Ar ages are obtained as 333–320 Ma for the metamorphism of this sequence under greenschist to amphibolite facies. Moreover, the limy intercalations in the volcano-sedimentary part of this complex in Godar-e-Siah yielded Upper Devonian–Tournaisian conodonts. The northeastern part of this complex in the Jandaq area was intruded by 215 ± 15 Ma arc to collisional granite and pegmatites dated by ID-TIMS and its metamorphic rocks are characterized by some 40Ar/39Ar radiometric ages of 163–156 Ma.
The “Variscan” accretionary complex was northwardly accreted to the Airekan granitic terrane dated at 549 ± 15 Ma. Later, from the Late Carboniferous to Triassic, huge amounts of oceanic material were accreted to its southern side and penetrated by several seamounts such as the Anarak and Kabudan. This new period of accretion is supported by the 280–230 Ma 40Ar/39Ar ages for the Anarak mild high-pressure metamorphic rocks and a 262 Ma U–Pb age for the trondhjemite–rhyolite association of that area. The Triassic Bayazeh flysch filled the foreland basin during the final closure of the Paleo-Tethys Ocean and was partly deposited and/or thrusted onto the Cimmerian Yazd block.
The Paleo-Tethys magmatic arc products have been well-preserved in the Late Devonian–Carboniferous Godar-e-Siah intra-arc deposits and the Triassic Nakhlak fore-arc succession. On the passive margin of the Cimmerian block, in the Yazd region, the nearly continuous Upper Paleozoic platform-type deposition was totally interrupted during the Middle to Late Triassic. Local erosion, down to Lower Paleozoic levels, may be related to flexural bulge erosion. The platform was finally unconformably covered by Liassic continental molassic deposits of the Shemshak.
One of the extensional periods related to Neo-Tethyan back-arc rifting in Late Cretaceous time finally separated parts of the Eocimmerian collisional domain from the Eurasian Turan domain. The opening and closing of this new ocean, characterized by the Nain and Sabzevar ophiolitic mélanges, finally transported the Anarak–Jandaq composite terrane to Central Iran, accompanied by large scale rotation of the Central-East Iranian Microcontinent (CEIM). Due to many similarities between the Posht-e-Badam metamorphic complex and the Anarak–Jandaq composite terrane, the former could be part of the latter, if it was transported further south during Tertiary time. 相似文献
14.
本文在对渭河地区及周缘晚古生代-中生代残存地层分布研究的基础上,采用岩石学、锆石同位素年代学、主微量元素地球化学分析方法,对渭河地区南北两侧上古生界二叠系及中生界三叠系进行对比,进而恢复了研究区晚古生代晚期、中生代早期沉积面貌,并结合裂变径迹构造抬升的研究结果,探讨了渭河地区中生代后期改造过程及演化阶段。结果显示:渭河盆地内部主要凹陷可能仅残留小范围的、不连续的C-P地层,未发现中生代地层。岩石学、锆石U-Pb年龄、主微量元素表明鄂尔多斯南部和北秦岭地区二叠系、三叠系具有很好的对比性,两者在相同时期为同一盆地。二叠系碎屑岩源区可能为再旋回造山带及陆块源区,主要来自北秦岭中-新元古界宽坪群变质碎屑岩及南部二郎坪群火山-沉积岩;三叠系沉积岩物源主要来自北秦岭地区的宽坪群、秦岭群或同期发育的火山岩。裂变径迹资料暗示渭河地区与渭北隆起及秦岭造山带中生代抬升期次具有一致性:晚侏罗世-早白垩世末,地层以强烈的构造变形、弱抬升为主;早白垩世末以来,地层发生大规模抬升、剥蚀,致使上古生界-中生界在渭河地区残留较少。在以上研究的基础上,将渭河地区晚古生代-中生代演化过程分为晚古生代二叠纪、中生代三叠纪-早中侏罗世、晚侏罗世-早白垩世末、早白垩世末-白垩纪末几个演化阶段。 相似文献
15.
塔里木盆地东南缘(阿尔金山)"变质基底"记录的多期构造热事件:锆石U-Pb年代学的制约 总被引：23，自引：16，他引：7
塔里木盆地东南缘的阿尔金山被认为是塔里木克拉通变质基底的主要出露地区之一。 本文通过阿尔金山北坡不整合在太古代-古元古代变质基底之上的安南坝群中的碎屑岩和中南阿尔金中深变质岩石(原定为阿尔金岩群)的锆石U-Pb年代学研究,来确定塔里木盆地东南缘变质基底的性质及所经历的多期构造热历史。研究结果显示,塔里木盆地东南缘的安南坝群中含砾砂岩的碎屑锆石年龄集中在1.92Ga左右,少量在2.0~2.4Ga,表明其碎屑物质主要来源于下伏的太古代-早元古代米兰岩群和相关的深成侵入体。在中阿尔金地块和南阿尔金俯冲碰撞杂岩带的深变质岩石中,锆石U-Pb年代学数据表明其记录有新元古代早期(920~940Ma)、新元古代晚期(760Ma左右)和早古生代(450~500Ma)三期构造热事件,新元古代早期的构造热事件与塔里木(或晋宁)造山作用有关,它普遍存在于塔里木盆地周缘的和南中国地块(扬子克拉通)的变质基底岩石中,与Rodinia超级大陆汇聚相关;新元古代晚期的构造热事件也同样广泛存在于塔里木盆地周缘和扬子克拉通之中,被认为与Rodinia超大陆的裂解作用有关。因此,在新元古代时期,阿尔金的地质演化历史与扬子克拉通非常相似,而与华北则有很大的不同,锆石U-Pb测定还表明中南阿尔金的深变质岩石普遍遭受了早古生代的变质作用的改造,显示它们普遍卷入了早古生代的碰撞造山事件之中,成为早古生代碰撞造山带的组成部分。 相似文献
16.
青海南部治多-杂多地区石炭纪-三叠纪砂岩地球化学特征与构造背景探讨 总被引：2，自引：0，他引：2
选取青海南部治多-杂多地区石炭纪-三叠纪的砂岩、粉砂岩样品,进行主量元素地球化学分析,利用分析结果判别物源区大地构造背景,探讨北羌塘盆地的性质及演化。研究结果表明:北羌塘中段的治多-杂多地区物源区大地构造背景早石炭世为被动大陆边缘;早中二叠世为被动大陆边缘、活动大陆边缘和大陆岛弧;晚三叠世为被动大陆边缘、活动大陆边缘和大陆岛弧。结合地层学、沉积学和岩石学,治多-杂多地区的沉积盆地经历了早石炭世被动陆缘克拉通盆地-早中二叠世裂陷盆地和早中三叠世被动边缘克拉通盆地-晚三叠世弧后前陆盆地的两个演化旋回,体现了金沙江缝合带和甘孜-理塘缝合带成生发展在研究区内的沉积响应。 相似文献
17.
A.H.F. Robertson 《地学学报》1990,2(4):333-339
In northern Euboea (Eastern Greece), Late Cretaceous platform carbonates of the Pelagonian Zone pass depositionally upwards into Maastrichtian hemipelagic limestones, possibly reflecting a rifting event in the adjacent Neotethys. This is followed by a c. 1 km-thick unit of siliciclastic turbidites, debris flows and detached limestone blocks. Thrust intercalations of ophiolitic rocks comprise altered pillow basalts and ultramafic rocks with ophicalcite. Calcite veins in sheared serpentinite contain planktonic foraminifera and the ophicalcite is directly overlain, with a depositional contact, by Globotruncana-bearing pelagic limestones and calciturbidites of Maastrichtian age. The ophiolitic rocks are interpreted as Late Cretaceous oceanic crust and mantle, that formed at a fracture zone, or rifted spreading axis within a Neotethyan, Vardar basin to the east. During the Early Tertiary (Palaeocene–Eocene), the Neotethyan basin began to close, with development of a subduction-accretion complex, mainly comprising sheared, trench-type sandstones, associated with ophiolitic slices. In response to trench/margin collision, the Pelagonian carbonate platform foundered and limestone debris flows and olistoliths were shed into a siliciclastic foreland basin. Suturing of the Neotethyan ocean basin then resulted in westwards thrusting of oceanic units over the foreland basin, thrusting of slices of inferred Late Cretaceous Pelagonian carbonate platform slope and large-scale recumbent folding. 相似文献
18.
基于砂岩碎屑组成、古流向恢复、全岩地球化学分析并结合已报道岩相古地理等研究成果的综合分析,探讨川西南晚三叠世瑞替期须家河组的物源体系、沉积记录及其形成的构造背景。砂岩碎屑组成分析结果显示,峨眉川主地区须家河组砂岩成分成熟度较低,组分与已报道的须家河组砂岩组分相似,物质以再旋回造山带来源为主;古流向测试数据统计显示须家河组主要接受来自东至东北部和东南部的物源,少量接受来自西南部和西北部的物源;地球化学主量元素及风化指数显示峨眉川主须家河组形成于构造活动背景下以被动大陆边缘和活动大陆边缘为主的沉积环境,物源成分成熟度较低;微量和稀土元素分析提示须家河组来源于长英质碎屑且含有较多古老沉积组分的加入,其球粒陨石标准化配分模式、原始地幔标准化微量元素模式与上地壳配分形式具有高度相似性,且物源主要与再旋回的扬子西南攀西-滇黔地区太古代-二叠纪变质岩、秦岭造山带前中生界变质岩和沉积岩、江南雪峰造山带西段的新元古代沉积有关,少量来自康滇古陆新元古代-元古代变质岩和龙门山周缘三叠纪沉积岩。结合须家河组已报道的岩相古地理数据,表明川西南峨眉地区晚三叠世瑞替期须家河组物源主要来自东南部的江南雪峰构造带和北部的秦岭造山带,少量来源于西南部的康滇古陆和西北部的龙门山构造带,川西南峨眉地区形成了主要受江南雪峰构造带、秦岭造山带为主控制的须家河组海陆交互相-陆相沉积盆地。 相似文献
19.
澜沧江南带三叠纪火山岩岩石学、地球化学特征、Ar-Ar年代学研究及其构造意义 总被引：5，自引：3，他引：2
滇西三江地区澜沧江南带广泛发育三叠纪火山岩。在北部云县一带,中晚三叠世火山岩出露齐全,自下而上可划分为中三叠统忙怀组(T2m),上三叠统小定西组(T3x)和上三叠统芒汇河组(T3mh)。忙怀组以酸性火山岩为主,为一套流纹岩夹火山碎屑岩组合;小定西组发育为中基性火山熔岩夹火山碎屑岩;芒汇河组具有流纹质火山碎屑岩与玄武岩共存的"双峰式"火山岩特征。地球化学特征表明,南澜沧江带三叠纪火山岩具有弧火山岩与大陆板内火山岩的双重属性,推测其形成环境为过渡型的大陆边缘造山带环境。对南澜沧江带南部景洪附近采集到的石英安山岩样品进行Ar-Ar年龄测试,得到的坪年龄为236.7±2.2Ma,为中三叠世。结合火山岩年代学结果,推测澜沧江洋主碰撞期为早三叠世,中三叠世与晚三叠世早期分别为碰撞后的应力松弛阶段与洋盆继续俯冲期,到晚三叠世末期,俯冲作用结束,澜沧江洋关闭。 相似文献
20.
藏夏河组是指发育于北羌塘盆地北部的一套砂、泥质互层的复理石相沉积地层, 其时代为晚三叠世诺利期.由于其形成时间正是羌塘地体与可可西里-松潘地体沿金沙江缝合带进行碰撞、缝合的时期, 因此该套地层对于探讨晚三叠世藏北地质演化具有重要的指示意义.通过对北羌塘盆地多色梁一带藏夏河组砂岩进行X射线衍射, 全岩常量、稀土和微量元素分析, 以及锆石裂变径迹等方法分析该套砂岩的物源、沉积构造背景, 进而探讨晚三叠世羌塘盆地的性质.研究结果表明, 其岩石类型为杂砂岩, 物源主要为长英质火成物质, 另有少量古地壳再循环物质加入, 沉积大地构造背景为活动大陆边缘与大陆岛弧.结合前人研究资料, 推断晚三叠世北羌塘盆地的性质可能为前陆盆地, 藏夏河组为一套造山前或同造山期形成的复理石沉积建造. 相似文献