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1.
There are several geological, geochemical and geophysical evidences, which corroborate reconstruction of Gondwanaland and juxtaposition of India and Antarctica. Petrology of the Precambrian mafic dykes of East Antarctica and Central-East India also support juxtaposition of India and Antarctica. Mafic dykes of different generations are emplaced in the Archaean granite gneisses of these regions. These dykes appear to be an important tool to support juxtaposition of India and Antarctica. Geological and petrological data of the Central-East India Precambrian mafic dykes suggest four episodes of mafic magmatism in the region - three tholeiitic and one noritic (?). Similarly, East Antarctica also comprises four dyke suites, emplaced during three distinct periods. These suites are 2.4 Ga meta-tholeiites, 2.4 Ga high-Mg tholeiites, 1.8 Ga dolerites and 1.2–1.4 Ga dolerites. Geochemical compositions of these mafic dykes are compared and they show good relationships with each other. Similarities in petrological and geochemical characteristics of Precambrian mafic dykes of East Antarctica and Central-East India strongly support juxtaposition of these two continents. 相似文献
2.
南岭地区新元古代变质沉积岩的地球化学特征及构造意义 总被引：6，自引：0，他引：6
对华夏地块南岭地区38个新元古代基底变质岩的岩相学和地球化学分析表明,它们的原岩都是沉积岩。不同地区变质沉积岩的化学成分存在一定的变化,但是它们大都具有明显的轻重稀土元素分异和Eu负异常（Eu／Eu^＋=0．35～0．76）,高K2O／Na2O、La／Co、Th／Sc比值和低Cr／Zr比值,显示了高成熟度和沉积再循环地壳的特点,表明沉积岩的物质主要来源于古老的再循环的地壳,它们沉积于被动大陆边缘。与其他地区元古宙沉积岩的地球化学对比显示,南岭地区这些新元古代沉积岩不同于赣中和扬子地块南缘的元古宙沉积岩,而与印度东北部ksser Himalaya地区的元古宙沉积岩较为相似。所以,南岭地区新元古代沉积岩的物质不可能来自与赣中和扬子地块南缘沉积物相同的扬子南部的源区,而应该来自南方,这一推论与岩相古地理分析以及沉积物中碎屑锆石形貌特征和年龄谱变化的结论是一致的,指示华夏南部新元古代时曾与一个大陆源区相邻。根据地球化学对比研究,结合已有的年代学对比,推断华夏地块南岭地区（特别是中部）新元古代沉积物很可能来源于与Lesser Himalaya地区元古宙沉积岩相同的源区,即东Gondwana大陆的北缘。这样,华夏地块在Rodinia超大陆裂解时期很可能是位于西澳大利亚-东印度-东南极之间。 相似文献
3.
The movement of Antarctica with respect to South America has a number of implications for paleocirculation as well as for the reconstructions of Gondwanaland. Recent papers on the Southwest Indian Ridge have published new or revised poles of opening for Africa and Antarctica which can be combined with the poles of opening between South America and Africa to give resultant motions between South America and Antarctica.The first indication of a complete closure between South America and the Antarctic Peninsula is at anomaly 28 time (64 Ma) as the two continents are now configured. Between anomaly 28 time (64 Ma) and anomaly M0 time (119 Ma) the amount of closure does not change greatly, and the small computed overlap can be explained by minor uncertainties in the rotation poles used for the reconstructions or some slight extension between East and West Antarctica. By 135 Ma some rotation or translation of the Antarctic Peninsula with respect to East Antarctica must be postulated in addition to any presumed extension between East and West Antarctica in order to avoid an overlap of South America with the Antarctic Peninsula.Having determined what we feel to be a viable reconstruction of Western Gondwanaland and holding South America fixed, we rotated Africa and Antarctica, with respect to South America, for eight different times during the past. Africa moved away from South America in a more or less consistent manner throughout the time period, closure to present, while Antarctica moved away from Africa in a consistent manner only between 160 Ma and 64 Ma. At 64 Ma its motion changed abruptly: it slowed its north-south motion with respect to Africa and began slow east-west extension with respect to South America. This change supports the hypothesis that a major reorganization of the triple junction between Africa, Antarctica and South America occurred between 60 and 65 Ma. The triple junction changed from ridge-ridge-ridge to ridge-fault-fault at the time of the major westward jump of the Mid-Atlantic Ridge just south of the Falkland-Agulhas Fracture Zone.The Mesozoic opening of the Somali Basin moved Madagascar from its presumed original position with Africa in Gondwanaland. The closure of Sri Lanka with India produces a unique fit for India and Sri Lanka with respect to Africa, Madagascar and Antarctica. This fit juxtaposes geological localities in Southeast India against similar localities in Enderhy Land. East Antarctica. The late Jurassic opening in the Somali Basin is tied to opening of the same age in the Mozambique Basin. Since this late Jurassic movement represents the initial break-up of Gondwanaland, it is assumed that similar movement must have occurred in what is now the western Weddell Sea and may also explain the opening evidenced by the Rocas Verdes region of southern South America. 相似文献
4.
Palaeomagnetic data for five time intervals in the Phanerozoic are compared for a new fit of East (Antarctica, Australia, India) and West (Africa, Madagascar, South America) Gondwanaland and the hitherto durable fit of Smith and Hallam. The dispersion of the Palaeomagnetic poles is marginally less on the Smith and Hallam fit for four time intervals and marginally greater for the remaining one (Permo-Triassic). The Permo-Triassic poles of East Gondwanaland are evenly distributed between India and Australia and the decreased dispersion of the poles for this period on the new fit of East and West Gondwanaland is paralleled by the decreased dispersion of the poles for both India and Australia. Within the limitations of the analysis imposed by the data, the palaeomagnetic comparison shows that there is little to choose between the two fits. 相似文献
5.
Cenozoic Exhumation of Larsemann Hills,East Antarctica: Evidence from Apatite Fission-track Thermochronology 总被引：1，自引：0，他引：1
<正>Does Cenozoic exhumation occur in the Larsemann Hills,East Antarctica? In the present paper,we conducted an apatite fission-track thermochronologic study across the Larsemann Hills of East Antarctica.Our work reveals a Cenozoic exhumation event at 49.8±12 Ma,which we interpret to be a result of exhumation caused by crustal extension.Within the uncertainty of our age determination, the timing of extension in East Antarctica determined by our study is coeval with the onset time of rifting in West Antarctica at c.55 Ma.The apatite fission-track cooling ages vary systematically in space, indicating a coherent block rotation of the Larsemann Hills region from c.50 Ma to c.10 Ma.This pattern of block tilting was locally disrupted by normal faulting along the Larsemann Hills detachment fault at c.5.4 Ma.The regional extension in the Larsemann Hills,East Antarctica was the result of tectonic evolution in this area,and may be related to the global extension.Through the discussion of Pan-Gondwanaland movement,and Mesozoic and Cenozoic extensions in West and East Antarctica and adjacent areas,we suggest that the protracted Cenozoic cooling over the Larsemann Hills area was caused by extensional tectonics related to separation and formation of the India Ocean at the time of Gondwanaland breakup. 相似文献
6.
《International Geology Review》2012,54(14):1791-1805
Newly discovered basalts in the Dabure area (central Qiangtang block, northern Tibet) were subjected to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb zircon dating, geochemical analyses, and zircon Hf isotope analyses. Dating of magmatic zircons from three basalt samples indicates that the Dabure basalts formed during the late Ediacaran (~550 Ma). Xenocrystic zircons yield ages of 700–1150 Ma, providing evidence of the Cryogenian crust in the Tibet block. The Dabure basalts are alkaline, rich in Ti and Fe, and are strongly enriched in light rare earth elements without Eu anomalies. The basalts are geochemically similar to within-plate basalts but are relatively depleted in Nb and Ta. Although the analysed zircons show differences in their Hf isotope compositions, the geochemical data suggest that the Dabure basalts were derived from enriched mantle and that the source magmas were contaminated by the continental crust. The basalts may have erupted during rifting at ~550 Ma (from the dating of magmatic zircons), and may have been a product of the initial breakup of Gondwanaland. 相似文献
7.
Gondwanaland origin, dispersion, and accretion of East and Southeast Asian continental terranes 总被引：3，自引：0，他引：3
East and Southeast Asia is a complex assembly of allochthonous continental terranes, island arcs, accretionary complexes and small ocean basins. The boundaries between continental terranes are marked by major fault zones or by sutures recognized by the presence of ophiolites, mélanges and accretionary complexes. Stratigraphical, sedimentological, paleobiogeographical and paleomagnetic data suggest that all of the East and Southeast Asian continental terranes were derived directly or indirectly from the Iran-Himalaya-Australia margin of Gondwanaland. The evolution of the terranes is one of rifting from Gondwanaland, northwards drift and amalgamation/accretion to form present day East Asia. Three continental silvers were rifted from the northeast margin of Gondwanaland in the Silurian-Early Devonian (North China, South China, Indochina/East Malaya, Qamdo-Simao and Tarim terranes), Early-Middle Permian (Sibumasu, Lhasa and Qiangtang terranes) and Late Jurassic (West Burma terrane, Woyla terranes). The northwards drift of these terranes was effected by the opening and closing of three successive Tethys oceans, the Paleo-Tethys, Meso-Tethys and Ceno-Tethys. Terrane assembly took place between the Late Paleozoic and Cenozoic, but the precise timings of amalgamation and accretion are still contentious. Amalgamation of South China and Indochina/East Malaya occurred during the Early Carboniferous along the Song Ma Suture to form “Cathaysialand”. Cathaysialand, together with North China, formed a large continental region within the Paleotethys during the Late Carboniferous and Permian. Paleomagnetic data indicate that this continental region was in equatorial to low northern paleolatitudes which is consistent with the tropical Cathaysian flora developed on these terranes. The Tarim terrane (together with the Kunlun, Qaidam and Ala Shan terranes) accreted to Kazakhstan/Siberia in the Permian. This was followed by the suturing of Sibumasu and Qiangtang to Cathaysialand in the Late Permian-Early Triassic, largely closing the Paleo-Tethys. North and South China were amalgamated in the Late Triassic-Early Jurassic and finally welded to Laurasia around the same time. The Lhasa terrane accreted to the Sibumasu-Qiangtang terrane in the Late Jurassic and the Kurosegawa terrane of Japan, interpreted to be derived from Australian Gondwanaland, accreted to Japanese Eurasia, also in the Late Jurassic. The West Burma and Woyla terranes drifted northwards during the Late Jurassic and Early Cretaceous as the Ceno-Tethys opened and the Meso-Tethys was destroyed by subduction beneath Eurasia and were accreted to proto-Southeast Asia in the Early to Late Cretaceous. The Southwest Borneo and Semitau terranes amalgamated to each other and accreted to Indochina/East Malaya in the Late Cretaceous and the Hainanese terranes probably accreted to South China sometime in the Cretaceous. 相似文献
8.
河南汝阳竹园沟钼矿床是在东秦岭-大别山钼成矿带新发现的钼矿床,估算钼金属量9.59万t,平均品位0.10%,储量为中型。该钼矿是在燕山晚期侵入花岗岩体内找钼取得的新进展。竹园沟花岗岩为太山庙花岗岩体的一部分,具陆内造山作用后期拉张环境下A型花岗岩特征。矿体赋存于燕山晚期第三次侵入的正长花岗斑岩与第一次侵入的中粗粒正长花岗岩的内接触带,矿体呈似层状、透镜状产出,矿床类型为斑岩型钼矿床。在全面分析该区成矿地质条件、化探异常特征的基础上,以寻找斑岩型矿开展勘查工作,逐步认识、实践,最终取得了找矿突破。通过对矿床地质特征研究,总结了以下找矿关键部位：（1）燕山晚期花岗岩区内1：5万Mo地球化学异常地段;（2）不同比例尺Mo元素地球化学异常重叠部位;（3）与区域NE向断裂方向一致,彼此大致平行的小型断裂构造带、裂隙发育带或密集带;（4）燕山晚期太山庙A型花岗岩内不同期次花岗岩侵入体内接触带附近;（5）从成因上看属于斑岩型钼矿床。竹园沟钼矿床的发现,为在东秦岭-大别山钼成矿带找矿提供了新的思路。 相似文献
9.
A. R. Crawford 《Tectonophysics》1974,22(1-2)
A detailed examination of a Gondwanaland re-assembly of Peninsular India and part of East Antarctica permits several conclusions to be drawn largely from data from the Indian coastal belt, which includes Ceylon. These are that original major granulite metamorphism probably occurred at about 2000 m.y., and that the sinuosity of the granulite belt, now split into two coastal belts, is a later distortion, outlined by anorthosite occurrences in India, which probably occurred between 720 and 450 m.y. Brief mention is made of the continuation of this belt into Madagascar, and of the problem of what lay between Western Australia and India in Gondwanaland. 相似文献
10.
11.
Ezz El Din Abdel Hakim Khalaf 《Arabian Journal of Geosciences》2012,5(4):663-695
Nugara volcanics are one of the northernmost outcrops of the Arabian?CNubian Shield. Two distinct volcanic successions are found in the Nugara basin: (1) old volcanic sequence composed of voluminous medium- to high-K calc-alkaline lavas and minor alkali basalt and (2) young volcanic sequence composed of subordinate tholeiitic mafic lavas. Their eruptions were punctuated by occasional volcaniclastic deposits that generated fall, flow, or reworked suites compositionally identical to the lava flows. These volcanics are a part of a post-subduction and extensional-related magmatic event in Northeastern Desert of Egypt. The volcanic rocks of the Nugara basin are characterized by strong enrichment in LILE relative to HESF, high LILE/HFSE ratios, and depletions of Nb on MORB-normalized multi-element diagrams. The geochemical features of the volcanic rocks suggest that they experienced fractional crystallization, along with mixing processes. Crustal contributions to the magma sources may also have occurred during magmatic evolution. These processes have resulted in scattered major and trace element variations with respect to increasing silica contents. The model proposed for their origin involves contrasting ascent paths and differentiation histories through crustal columns with different thermal and density gradients. The geochemical features of the most mafic samples suggest that the volcanic rocks in the region were derived from a mainly lithospheric mantle source that had been heterogeneously metasomatized by previous subduction events during convergence between the East and West Gondwanaland. The volcanic activity in the region is best explained by the delamination of lithospheric mantle slices that were heterogeneously enriched by previous subduction-related processes. 相似文献
12.
东昆仑造山带发育大量花岗质岩浆岩,对其研究不仅能为东昆仑的岩浆、构造提供新的信息,且对探讨古特提斯的构造-演化过程具重要意义。本文报道东昆仑西段落雁山花岗闪长斑岩体的两组锆石U-Pb年龄和地球化学数据,并对其成因及构造意义进行探讨。两组落雁山花岗闪长斑岩体锆石206Pb/238U-年龄分别为(312.4±2.0)Ma、(312.4±2.2)Ma,形成于晚石炭世。岩石地球化学特征显示,该岩体具高钾钙碱性准铝质花岗岩特征,稀土元素标准分布曲线呈右倾,富集轻稀土,轻、重稀土分异明显,微量元素中大离子亲石元素(LILE:Rb,Ba)相对富集;高场强元素(HFSE:Nb,P,Ti)亏损。锆石Hf同位素特征和岩石成因物源研究表明,落雁山花岗闪长斑岩为少量幔源岩浆参与的壳幔混源I型花岗岩。据区域构造研究,落雁山花岗闪长斑岩形成于晚石炭世古特提斯洋壳俯冲作用背景下的岛弧晚期岩浆活动。 相似文献
13.
A. A. Chashchin Yu. A. Martynov S. V. Rasskazov S. O. Maksimov I. S. Brandt E. V. Saranina 《Petrology》2007,15(6):575-598
Major oxides, trace elements (ICP-MS analysis), and Sr isotope ratios were analyzed in the late Miocene subalkaline and alkaline basaltoids of the southern part of the Russian Far East, which were formed during the final stage of the development of intraplate basaltic volcanism. Based on these data, variations in the main geochemical and mineralogical characteristics of various tectonomagmatic terranes were evaluated. The enriched and heterogeneous continental lithosphere modified to a varying extent by postaccretion subduction processes of different ages played a major role in the formation of the rocks. The first geochemical evidence was obtained for the subduction of the Solonker paleoceanic plate beneath the Amur microcontinent during the Permian. 相似文献
14.
15.
Michael R. W. Johnson 《地学学报》2003,15(1):46-51
ABSTRACT The nature of the Indian crust underthrusting the Himalaya may be studied in xenoliths within Ordovician granites in the external part of the Himalaya. These peraluminous S-type granites have travelled for c . 200 km in the Main Central (or related) thrust. The granites and xenoliths sample Indian basement now buried beneath the High Himalayan thrust pile. In low-strain granites the xenoliths reveal polyphase tectonite fabrics older than the fabrics in the country rocks. Most xenoliths show greenschist/lower amphibolite facies assemblages; none is typical granulite facies of the Indian Shield. Therefore, the portion of the Indian crust underthrusting the Himalaya may be early/middle Proterozoic reworked Indian Shield, as in peninsular India. Alternatively reworking may be assigned to the Pan-African (late Proterozoic) orogeny. This prospect is raised by recent work in East Antarctica but evidence in the Himalaya is rather ambiguous. If confirmed, a Pan-African event calls for reassessment of the geological history of the Himalayan region, particularly with respect to the placing of India in Gondwanaland. 相似文献
16.
Revised palaeomagnetic data for the Mesozoic of Australia confirm the unity of Gondwanaland until the mid-Jurassic. By combining palaeomagnetic poles from all the Gondwana continents, an apparent polar shift is recognized for the late Palaeozoic, Triassic and Jurassic. 相似文献
17.
通过对东昆仑-阿尔金地区区域化探工作研究程度及取得主要成果的介绍,说明了该区开展区域化探工作所采用关键技术方法的有效性,并大致阐述了本区39种元素的富集特征及其分带性。通过研究认为,东昆仑-阿尔金地区是铅、锌、铁、铜、金、银、钨、钼、锡、锑、汞等多元素的富集区,东昆仑祁漫塔格是以铅、锌、铁、铜、钨、锡、金等为主的多金属地球化学带,阿尔喀山一带则是东昆仑地区的主要汞、锑地球化学带,另外,阿尔金金、铜成矿带和阿帕-茫崖超基性岩带也是本区具有重要地质找矿意义的地球化学区带,上述研究成果对该区后继的地质找矿工作具有极高的指导意义和参考价值,亦为该区成为重要的整装勘查区和资源接替区奠定了基础。 相似文献
18.
Three late Anisian (Etalian) and five late Ladinian (Kaihikuan) crinoids are known to occur in a sequence exposed at Caroline Cutting, Oreti Valley, Southland, New Zealand - ‘Isocrinus’ carolinensis, ‘Isocrinus’ balrnacaanensis, Dadocrinus gractlis (late Anisian - Etalian), Holocrinus trechmanni, Encriniis undatus, Encrinus ternio, Holocrinus quinqueradiatus, Tollmannicrinus sakltbelensts (Late Ladinian - Kaihikuan). Crinoids D. gracilts, E. ternto, H. quinqueradiatus, and T. saklibelensis are known to occur elsewhere, albeit in the Northern Hemisphere. These species are also known from intermediate migratory points on a Tethys Ocean route between New Zcaland and Europe. ‘Isocrinus’ occurs at Caroline Cutting about thc time when it has been proposed that thc Isocrinidae radiated from the Holocrinidae. It is suggested that the offshore Gondwanaland environment of Caroline Cutting was the locus of some of the earliest Isocrinidae known in the Southern hemisphere. This biogeographic situation suggests an ongoing interchange of migratory crinoid faunas from Northern Hemisphere basinal peri-Tethys, along a Tethys Ocean route, to an offshore Gondwanaland Middle Triassic point now called Caroline Cutting. 相似文献
19.
A geochemical investigation was carried out mainly in a 14-km thick sedimentary sequence of late Precambrian age. The project included analysis of rock samples and drainage samples for Cu, Co, and Zn. The drainage samples were heavy-mineral concentrates and stream sediment samples.The results for the drainage sediments distinguish three well defined cupriferous horizons in the sedimentary column. Lithogeochemical studies of quartzites, pelites, and carbonates confirm that the anomalous values obtained in the drainage sediments arise from several Cu-mineralized horizons.The study has shown that geochemical prospecting appears to be well suited to Cu prospecting in Central East Greenland under arctic climate conditions even with a low sampling density of one sample per 5–10 km2 for the drainage samples, and one sample per 10–100 m of the sedimentary stratigraphic column for the rock samples. 相似文献