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1.
Extensive high-grade polydeformed metamorphic provinces surroundingArchaean cratonic nuclei in the East Antarctic Shield recordtwo tectono-thermal episodes in late Mesoproterozoic and lateNeoproterozoicCambrian times. In Western Dronning MaudLand, the high-grade Mesoproterozoic Maud Belt is juxtaposedagainst the Archaean Grunehogna Province and has traditionallybeen interpreted as a Grenvillian mobile belt that was thermallyoverprinted during the Early Palaeozoic. Integration of newUPb sensitive high-resolution ion microprobe and conventionalsingle zircon and monazite age data, and ArAr data onhornblende and biotite, with thermobarometric calculations onrocks from the H.U. Sverdrupfjella, northern Maud Belt, resultedin a more complex PTt evolution than previouslyassumed. A c. 540 Ma monazite, hosted by an upper ampibolite-faciesmineral assemblage defining a regionally dominant top-to-NWshear fabric, provides strong evidence for the penetrative deformationin the area being of Pan-African age and not of Grenvillianage as previously reported. Relics of an eclogite-facies garnetomphaciteassemblage within strain-protected mafic boudins indicate thatthe peak metamorphic conditions recorded by most rocks in thearea (T = 687758°C, P = 9·411·3kbar) were attained subsequent to decompression from P >12·9 kbar. By analogy with limited UPb singlezircon age data and on circumstantial textural grounds, thisearlier eclogite-facies metamorphism is ascribed to subductionand accretion around 565 Ma. Post-peak metamorphic K-metasomatismunder amphibolite-facies conditions is ascribed to the intrusionof post-orogenic granite at c. 480 Ma. The recognition of extensivePan-African tectonism in the Maud Belt casts doubts on previousRodinia reconstructions, in which this belt takes a pivotalposition between East Antarctica, the Kalahari Craton and Laurentia.Evidence of late Mesoproterozoic high-grade metamorphism duringthe formation of the Maud Belt exists in the form of c. 1035Ma zircon overgrowths that are probably related to relics ofgranulite-facies metamorphism recorded from other parts of theMaud Belt. The polymetamorphic rocks are largely derived froma c. 1140 Ma volcanic arc and 1072 ± 10 Ma granite. KEY WORDS: Maud Belt; Pan-African orogeny; geochronology; PTt path, East Antarctica 相似文献
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一、引言超声测井是一种新的地震測井法,它是利用超声波来研究小間隔內(1-2米)鈷井剖面岩层的物理机械性貭。近年来,由于石油探測事业发展的需要,这种方法在地球物理勘探和地球物理测井中受到了广泛的注意。根据超声測井的試驗和应用的結果看来,这种方法可以簡捷、經济、精确、詳細地測定出岩石的物理机械性貭(纵波和横波的波速,波的吸收系数等等)及其随深度的变化。 相似文献
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THE THEORY STUDY GROUP OF THE th SECTION OF THE INSTITUTE OF GEOPHYSICS ACADEMIA SINICA 《地球物理学报》1975,18(2):77-80
当前,我国人民在伟大领袖毛主席关于理论问题重要指示的指引下,在党的十届二中全会和四届人大提出的战斗任务鼓舞下,认真学习马克思主义关于无产阶级专政的理论,继续普及、深入、持久地开展批林批孔运动,在上层建筑其中包括各个文化领域对资产阶级。 相似文献
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THE GEODETIC SURVEY BRIGADE FOR EARTHQUAKE RESEARCH NATIONAL SEISMOLOGICAL BUREAU 《地球物理学报》1975,18(3):153-163
1966年3月发生的邢台地震属震群型,五次大于6级的强震基本上都发生在邢衡隆起区中强烈下降的束鹿断陷内。水准测量结果说明,在地震前、地震时及地震后,断陷区都有明显的下降运动。大地测量结果证明,邢台地震是一个右旋型水平错动为主、并伴有水平方向的引张和垂直方向的下降运动,呈现出张扭性断层错动模型。在二次主震或强震的中间,水准复测结果说明:在已发生强震的震中一带强烈下沉,而可能的未来强震区有较明显的上升。邢台地震在地面垂直运动方面,地震前后大致存在四个地形变阶段,并在总体上具有同向地形变特征。 相似文献
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Since the importance of tho iron ore resources of the contact metamorphic type in China has been well recognized by many geologists and their geological occurrence and economic prospects have been described and published in detail 1, it seems desirable to have a review of those rocks known 相似文献
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Important notice to members:- All members are earnestly requested to send to the Secretary of the Society any change of address. The 相似文献