IGCP440"罗迪尼亚超大陆汇聚与裂解"项目2003年度工作进展   总被引：2，自引：0，他引：2  

S.彼萨列夫斯基 《世界地质》2004,23(2):118-122

借助于最新的地质、同位素年代学、地球化学和航空地球物理资料,对全球各地原属于罗迪尼亚大陆组成单元的构造环境、地质事件特征及其演化历史进行了探讨,并提出一些新见解和成因模式.认为东欧克拉通在1.7～0.9Ga有复杂的演化历史一个新的劳仑古陆和西伯利亚的重建发生在1 050～1 000Ma;中、新元古代南美洲造山拼贴的岩石构造历程构成南美陆台的西部边界非洲克拉通是古元古代/太古宙陆块汇聚收敛的结果;东南极的一部分在中元古时期附属于非洲南部;印度西北的新元古代长英质岩浆事件构成了罗迪尼亚大陆的西部边缘;前格林威尔时期的劳仑古陆已被确定为古元古代末期的一个主要大陆;在罗迪尼亚大陆中,华南可能位于劳仑古陆南部和澳大利亚东部之间;塔里木克拉通和扬子克拉通相连接或邻近.据此检验了关于Pisarevsky提出的罗迪尼亚超大陆汇聚和裂解的新模式.新模式提出初始裂解是沿着劳仑古陆的西部边缘,与大西洋北部相类似.同时认为一些大陆(印度、刚果/圣·弗朗西斯科)可能不是罗迪尼亚超大陆的组成部分.  相似文献   

东昆仑南带中元古代晚期—新元古代早期叠层石组合的发现          下载免费PDF全文

边千韬  朱士兴  I. I. Pospelov  M.A. Semikhatov  孙淑芬  陈代钊  那春光 《地质科学》2006,41(3):500-510

东昆仑南带加嗡门地区碳酸盐岩地层中发现的中元古代晚期-新元古代早期叠层石组合以大型锥叠层石及其相关的分子Conophyton garganicus var. inkeni,C. cf. ressoti Menchikov, Jacutophyton f. 和Conicodomenia cf. longotenuia等最丰富, 并与Baicalia共生, 故可视之为Conophyton-Baicalia组合.这叠层石组合可以与天山、华北等地蓟县系中部-青白口系中部叠层石组合对比,尤其酷似于天山地区蓟县系的爱尔基干组合和华北蓟县系的闪坡岭叠层石组合,而显著有别于华南地块.它还可以与南乌拉尔、西伯利亚、北美、北非和阿拉斯加半岛等地区的中里菲界上部--上里菲界下部层位中的叠层石组合对比.加嗡门叠层石组合的时限为距今1 300～850 Ma,大致为蓟县纪中期-青白口纪中期或中里菲晚期-晚里菲早期.东昆仑南带存在前寒武纪微地块,当时此微地块的古地理和古环境与天山、华北、西伯利亚和阿拉斯加半岛等地区的前寒武纪地块相似,均位于低纬度区,其上均广泛发育适宜叠层石繁育的温暖陆表海,它们可能共同处于罗迪尼亚超大陆的低纬度大陆边缘部位,与华南地块的不同.这对本区和东昆仑地层和大地构造研究,以及对罗迪尼亚超大陆重建提供了新的古生物约束.  相似文献   

震旦纪地层黄铁矿硫同位素组成时－空变化特征及扬子地块与晚元古超大陆关系的论证   总被引：7，自引：0，他引：7       下载免费PDF全文

李任伟  张淑坤  雷加锦  沈延安  陈锦石  储雪蕾 《地质科学》1996,(3):209

 扬子地区早震旦世时期沉积岩黄铁矿具有重的硫同位素组成,其δ¹⁴S值从早震旦世椿木组地层的24‰左右逐渐变得更正。在早震旦世扬子地区广泛沉积碳酸锰矿和黑色页岩的民乐组时期达到极正值+60‰,然后又降低至+16‰-+20‰。上述硫同位素组成的时-空变化特征支持了扬子地块属晚元古Rodinia超大陆的一个组成部分的假设。从晚震旦世早期陡山沱组底部开始,沉积岩中黄铁矿硫同位素的δ¹⁴SS出现负值,并继续降低至-27‰以下。早震旦世晚期-晚震旦世早期沉积岩中硫同位素组成特征反映了沉积盆地古海洋环境的剧烈变化,它与大约7亿年时Rodinia超大陆的解体以及扬子地块与其它大陆分离的地质推测相吻合。  相似文献   

Lithology and structure of the Grenville-aged (∼1.1 Ga) basement of Heimefrontfjella (East Antarctica)     

J. Jacobs  W. Bauer  G. Spaeth  R. J. Thomas  K. Weber 《International Journal of Earth Sciences》1996,85(4):800-821

The Heimefrontfjella mountains, Western Dronning Maud Land (East Antarctica), are dominantly composed of Grenville-aged (≈ 1.1 Ga) rocks, which were reworked during the Pan -African orogeny at ≈500 Ma. Three discontinuity-bounded Grenville-aged terranes have been recognized namely (from north to south) the Kottas, Sivorg and Vardeklettane terranes. The terranes contain their own characteristic lithological assemblages, although each is made up of an early supracrustal sequence of metavolcanic and/or metasedimentary gneisses, intruded by various (predominantly granitoid) suites. No older basement upon which the protoliths of these older gneisses were deposited has been recognized. In each terrane the older layered gneisses were intruded by various plutonic suites ranging in age from ≈ 1150 to ≈1000 Ma. The Vardeklettane terrane is characterized by abundant charnockites and two-pyroxene granulite facies parageneses in metabasites, whereas the Sivorg and Kottas terranes were metamorphosed to amphibolite facies grade. P-T estimates show that peak metamorphic conditions changed from ≈600°C at 8 kbar in the south, to ≈700 °C at 4 kbar in the northern Sivorg terrane. Regional greenschist retrogression of high-grade assemblages may be of Pan-African age. The Heimefrontfjella terranes were juxtaposed and pervasively deformed during a complex and protracted period of E-W collision orogenesis in a transpressive regime at ≈ 1.1 Ga. This is manifest as early, gently dipping thrust-related shear fabrics (D₁), succeeded by the initiation of an important (D₂) steep dextral shear zone (Heimefront shear zone, HSZ), during which the early fabrics and structures were steepened and rotated in an anticlockwise sense. The HSZ is a curvilinear structure which changes from a dextral oblique strike-slip lateral ramp in the north to a steep dip-slip frontal ramp in the south, where it forms the boundary between the Sivorg and Vardeklettane terranes. The Pan-African event is manifested as discrete, low- to medium-temperature ductile to brittle shears (D₃) and numerous K/Ar cooling ages.  相似文献   

Oblique collision at about 1.1 Ga along the southern margin of the Kaapvaal continent,south-east Africa     

J. Jacobs  R. J. Thomas 《International Journal of Earth Sciences》1994,83(2):322-333

The 1.1 Ga Natal Metamorphic Province (NMP) lies at the heart of a world-wide system of Grenville age mobile belts which welded early continental fragments into the Mesoproterozoic supercontinent of Rodinia. Structural analysis of the three tectonostratigraphic terranes in Natal reveals a kinematic history characterized by prolonged NE-SW plate convergence, manifested as early thrust tectonics and later pervasive sinistral transcurrent shearing. Consequently, superimposed on the Natal tectonostratigraphic terranes is a kinematic subdivision into tectonic domains which are characterized by shallow, south-west dipping foliations, south-west plunging stretching lineations and north-east verging recumbent folds, and by younger domains with subvertical shear fabrics, subhorizontal to oblique lineations and folding about near-vertical axes. Microtextural and petrographic analyses suggest that the later shearing took place under high temperature conditions of at least 500°C. The recorded kinematic indicators suggest that early subhorizontal compressional tectonics gave rise to tectonic thickening of the crust, progressively followed by oblique transcurrent shearing within a transpressional regime. The shearing event in the southern arc-related terranes was associated with the widespread emplacement of late kinematic rapakivi granite -charnockite plutons, with A-type granite geochemical characteristics. This orogenic event took place around 1100 Ma during prolonged NE-SW collisional convergence along the southern margin of the stable Archean foreland, which lay to the north.  相似文献   

A long connection (750–380 Ma) between South China and Australia: paleomagnetic constraints     

Zhenyu Yang  Zhiming Sun  Tienshui Yang  Junling Pei 《Earth and Planetary Science Letters》2004,220(3-4):423-434

A new paleomagnetic study has been carried out on sediments of middle Cambrian age in the North Sichuan Basin (Yangtze Block). Detailed stepwise thermal demagnetizations allowed us to isolate three components. Site-mean direction derived from higher temperature components is D/I=146.9°/–17.1° (₉₅=8.3°) yielding a pole position at 51.3°S, 166.0°E. The fold and reversal tests suggest that remanence was acquired during early stage of sedimentation. Combined with the high-qualities early Sinian (748 Ma) and middle Silurian poles obtained recently from the Yangtze block, the deriving polar track demonstrates a similar loop to that of Australia. After rotating these poles from South China to fit that of Australia, the South China Block is placed against northwestern Australia. This reconstruction favors the correlations of the Jiangnan Grenville-age orogenic belt with the Rudall belt of western Australia, and subsequently the late Proterozoic Jiangnan and Officer/Adelaide rift systems. The paleobiogeographic evidence also indicates that this configuration might maintain by the middle Devonian.  相似文献   

Paleomagnetism of Middle Proterozoic mafic intrusions and Upper Proterozoic (Nankoweap) red beds from the Lower Grand Canyon Supergroup, Arizona     

Arlo B. Weil  John W. Geissman  Matt Heizler  Rob Van der Voo 《Tectonophysics》2003,375(1-4):199

Paleomagnetic data from lavas and dikes of the Unkar igneous suite (16 sites) and sedimentary rocks of the Nankoweap Formation (7 sites), Grand Canyon Supergroup (GCSG), Arizona, provide two primary paleomagnetic poles for Laurentia for the latest Middle Proterozoic (ca. 1090 Ma) at 32°N, 185°E (dp=6.8°, DM=9.3°) and early Late Proterozoic (ca. 850–900 Ma) at 10°S, 163°E (dp=3.5°, DM=7.0°). A new ⁴⁰Ar/³⁹Ar age determination from an Unkar dike gives an interpreted intrusion age of about 1090 Ma, similar to previously reported geochronologic data for the Cardenas Basalts and associated intrusions. The paleomagnetic data show no evidence of any younger, middle Late Proterozoic tectonothermal event such as has been revealed in previous geochronologic studies of the Unkar igneous suite. The pole position for the Unkar Group Cardenas Basalts and related intrusions is in good agreement with other ca. 1100 Ma paleomagnetic poles from the Keweenawan midcontinent rift deposits and other SW Laurentia diabase intrusions. The close agreement in age and position of the Unkar intrusion (UI) pole with poles derived from rift related rocks from elsewhere in Laurentia indicates that mafic magmatism was essentially synchronous and widespread throughout Laurentia at ca. 1100 Ma, suggesting a large-scale continental magmatic event. The pole position for the Nankoweap Formation, which plots south of the Unkar mafic rocks, is consistent with a younger age of deposition, at about 900 to 850 Ma, than had previously been proposed. Consequently, the inferred 200 Ma difference in age between the Cardenas Basalts and overlying Nankoweap Formation provides evidence for a third major unconformity within the Grand Canyon sequence.  相似文献   

湖南中—新元古代火山—侵入岩地球化学及成因意义   总被引：11，自引：2，他引：11  

王孝磊  周金城等 《岩石学报》2003,19(1):49-60

江南造山带西段湖南中、新元古代火山－侵入岩具有截然不同的地球化学特征。中元古代火山－侵入岩金属亚碱性玄武岩类，MgO,Ni,Cr含量及Al2O3/TiO2比值高，稀土元素分馏形式多样，更多地具有岛弧火山岩的特征，新元古代中基性火山－侵入岩MgO,Ni,Cr含量较低；其中的基性岩大多属碱性玄武岩类，并较富TiO2,Al2O3/TiO2比值较低，HFSE明显富集，微量元素标准化曲线与OIB类似，具有裂谷玄武岩的特征。中元古代南桥玄武岩εNd(t)为6．86－8．98，具有明显的N－MORB特征，是俯冲带附近的古洋壳残片，为九岭古岛弧提供了新的证据。中元古代的益阳玄武岩εNd(t)为1．56－1．76，Nb,Ti,Zr亏损，Th相对富集，具俯冲带火山岩的地球化学特征，同时这些玄武岩具有高MgO、高Al2O3/TiO2比值和Ni,Cr含量，具科马提质玄武岩的特性，可能是局部地幔柱－弧相互作用的产物。新元古代早期益阳安山质集块岩Th,La,Sm和Nd富集，Nb,Ti,Zr和Hf亏损，εNd(t)值为－0．53－－1．05，是格林威尔造山运动的产物。新元古代黔阳，古丈、高桥火山－侵入岩原始地幔标准化曲线近似于OIB，具裂谷玄武岩的特征，黔阳，古丈基性岩εNd(t)值在1．09－1．69，来源于软流圈地幔，湖南这些中－新元古代火－侵入岩的地球化学特征记录了Radinia超大陆在该区从拼合到裂解的演化踪迹。  相似文献   

华南在Rodinia古陆中位置的讨论——扬子地块西缘变质-岩浆杂岩证据及其与Seychelles地块的对比   总被引：38，自引：1，他引：38  

颜丹平  周美夫  宋鸿林  John MALPAS 《地学前缘》2002,9(4):249-256

沿扬子地块西缘出露的一系列变质杂岩的构造性质及形成时代是分析华南地块大地构造属性的关键。这些杂岩均被初始为低角度的正断层所围限 ,具有变质核杂岩的构造性质 ,其剥露时间在177Ma左右。目前 ,对这一区域几个代表性杂岩体进行的系统的岩石学和地球化学分析表明 ,这是一套主体为与俯冲板块有关的岛弧型岩浆杂岩 ,其形成时代从 72 6～ 86 4Ma ,时间跨度在 10 0Ma以上。证明这些岩石的形成与地幔柱作用无关。上述结果与最近在Madagascar东北缘、Seychelles岛及印度的Malani的一条类似的变质岩浆杂岩带的地球化学与地质年代学研究结果完全吻合 ,这个构造带被解释为一条沿Mozambique洋东缘的巨大的向东俯冲的安第斯型俯冲 岩浆岛弧带。据此我们推测在Rodinia古大陆中 ,华南地块位于印度板块东北缘 ,其南东则可能与澳大利亚相接。  相似文献   

Late Mesoproterozoic (ca 1.2 Ga) palaeomagnetism of the Albany–Fraser orogen: no pre-Rodinia Australia–Laurentia connection     

S. A. Pisarevsky  M. T. D. Wingate  L. B. Harris 《Geophysical Journal International》2003,155(1):F6-F11

  相似文献