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为了探测西藏高原南部雅鲁藏布江缝合带地区地壳浅部和深部构造沿东西和南北方向的变化特征,在雅鲁藏布江缝合带地区布设了三条南北向剖面(错那—墨竹工卡、亚东—雪古拉、吉隆—措勤),采用超宽频带大地电磁测深方法进行了地壳、上地幔电性结构探测研究,发现该区主要电性结构特征为:1. 雅鲁藏布江缝合带附近表层发育大规模的高阻体,岩体延伸最深达30km以上,是冈底斯花岗岩体的反映. 2. 雅鲁藏布江缝合带的南部有小规模的良导体,在其下方和北侧发育有大规模良导体. 3. 沿剖面从南往北壳内普遍发育良导体,各良导体主体间是不连续的,规模逐渐增大,总体北倾,在缝合带附近产状较陡. 4. 在雅鲁藏布江缝合带附近良导体由西往东规模逐渐增大,导电性逐渐变好,相对雅鲁藏布江在剖面上的位置逐渐南移. 这些重要的电性特征可能是印度板块向北俯冲所形成的,深部大规模的良导体特征沿东西向的差异可能是板块碰撞引起物质沿东西向运移作用的结果. 相似文献
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本文分析了地表各处起因于深部电性变化前兆的大地电磁响应函数的变化形态、特征,探讨了对此大地电磁测深法的可分辨性的某些问题。研究表明,在离震中稍远的震源外围区,由扩展膨胀各向异性所引起的深部电性变化引起了某些大地电磁响应函数明显的可分辨的变化;发展中的地震断裂带和震前断裂蠕滑段,作为一个两维导电沟,可以引起邻近区域视电阻率,阻抗相位、维系数的可分辨的变化;对于一个异常的震源导电体,地表大地电磁响应函数显示出了两维模拟异常的某些类同和差异。 相似文献
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回顾了我国80年代中期以来大地电磁测深工作的进展,包括资料采集、数据处理和反演解释着重介绍了大地电磁测深法在石油、天然气构造普查勘探以及地壳和上地慢探测方面应用的情况. 相似文献
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华南地区 (指福建、广东一带 )位于中国的东南部 ,东临菲律宾板块与太平洋板块 ,是岩浆多期次的强烈活动区。在加里东、印支、燕山等各构造旋回期均有岩浆侵入活动 ,特别是燕山期更为强烈。研究区岩浆岩覆盖面广 ,占测区总面积的 80 %以上 ,是开展火山岩浆活动规律、岩类组分、内部结构特征研究的较好场所之一。笔者在 1 991~ 1 995年间 ,在该区进行了大范围的电磁探测 ,收集到一批很有价值的资料。通过 1 30多个大地电磁测点的资料分析、解释 ,对该区的电性结构特征及其构造意义有以下认识。( 1 )岩浆岩区电性特征有规律可循 ,其特征变化与火山岩浆活动的方式有着密切关系。在电性上有以下几种情况 :1 )高阻岩体 ,视电阻率曲线 (指一维形式化解释曲线 ,下同 )一般高频段为“K”型 ,高频段宽 ,视电阻率值极高 ,为 1 0 3 ~ 1 0 4甚至高达 1 0 5 Ω·m ,各类定性图上的高阻特征尤为明显 ;2 )岩体下有隐伏沉积层 ,视电阻率曲线一般为“KHK”型 ,高频段为高阻 ,以下频段为低阻或中等电阻值 ;3)沉积岩中有岩浆侵入 ,视电阻率曲线一般为“HK”型 ,定性图上的高阻圈闭不明显 ,但夹 相似文献
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针对南黄海盆地深层地震地质条件差,地震波受屏蔽,能量严重衰减,在海洋反射地震资料中很难识别反映中-古生界的反射地震波组,不能满足南黄海盆地前第三系油气资源前景评价的需要等问题,于2006年5月,开展了南黄海海域海底大地电磁测深试验,在盆地内五莲斜坡和胶州凹陷区布设了3个海底大地电磁测深点,取得了可靠的海底观测数据.本文详细阐述了海底大地电磁测深与常规大地电磁测深在数据处理方法上的差别,论述了海洋电磁噪声对海底大地电磁场观测的影响,提出了海底大地电磁场实测资料“水平姿态”校正、“方位”校正和“海洋电磁噪声”校正的方法.通过对试验观测资料的处理和反演,并结合地质、物性资料进行综合分析,结果表明在南黄海盆地海底以下深部还存留有古生代地层,这对于南黄海前第三系含油气前景的评价具有重要意义.试验结果也证明了海底大地电磁测深技术在研究古生代残留盆地方面的问题可以发挥相当好的作用. 相似文献
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Science China Earth Sciences - Trench basin, as an important sedimentary repository in oceanic subduction zones, documents faithfully the evolution of paleodrainage and paleogeographic information.... 相似文献
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LIU XiaoHan JU YiTai WEI LiJie & LI GuangWei Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China Mineral Resource Institute of China Metallurgical Geology Bureau Beijing 《中国科学:地球科学(英文版)》2010,(1)
The new field investigations along the Yarlung Zangbo ophiolites zone show that these series underwent low green-schist metamorphism and were then fractured and occurred as slabs in tectonic melanges,without regional tectonic polarity.No large shear zone in north-south direction has been identified between ophiolite bodies and flysch layers on both side and a conformable contact relationship can be observed locally between them.A great mass of tectonic mélange has been substantiated as submarine olistolith ... 相似文献
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Paleomagnetism of the Xigaze ophiolite and flysch (Yarlung Zangbo suture zone, southern Tibet): latitude and direction of spreading 总被引:1,自引:0,他引:1
J.P. Pozzi M. Westphal J. Girardeau J. Besse Yao Xiu Zhou Xian Yao Chen Li Sheng Xing 《Earth and Planetary Science Letters》1984,70(2):383-394
The Xigaze ophiolite (29.2°N, 89.5°E), which outcrops in the Yarlung Zangbo suture zone, represents the remnants of an oceanic lithosphere formed in middle Cretaceous times between the Lhasa block to the north and the Indian plate to the south. In an attempt to define the paleo-orientation and latitude of the spreading center at which it has been created, a paleomagnetic study has been done on three sites in volcanics and overlying (or interbedded) radiolarites forming the upper part of the ophiolite sequence and also on seven sites in the Xigaze Group flysch which stratigraphically overlies the volcanics to the north. In each site, hand-blocks carefully oriented both with sun and magnetic compass have been sampled. The paleomagnetism data, combined with structural data on the ophiolite dolerite intrusives, allow a partial reconstruction of South Eurasia at the time of formation of the Xigaze ophiolite. The paleolatitude of accretion and deposition of the Xigaze ophiolite and overlying sediments is found to be 10–20°N. Both ophiolite and basin have encountered a 85 ± 20° anti-clockwise rotation. The corresponding ridge was close to the southern margin of the Lhasa block and was oriented N175 ± 25°. 相似文献
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Hanpu Fu Xiumian Hu Erica M. Crouch Wei An Jiangang Wang Eduardo Garzanti 《中国科学:地球科学(英文版)》2018,61(9):1204-1220
The history of convergence between the India and the Asia plates, and of their subsequent collision which triggered the Himalayan orogeny is recorded in the Yarlung Zangbo suture zone. Exposed along the southern side of the suture, turbidites of the the Jiachala Formation fed largely from the Gangdese arc have long been considered as post-collisional foreland-basin deposits based on the reported occurrence of Paleocene-early Eocene dinoflagellate cysts and pollen assemblages. Because magmatic activity in the Gangdese arc continued through the Late Cretaceous and Paleogene, this scenario is incompatible with U-Pb ages of detrital zircons invariably older than the latest Cretaceous. To solve this conundrum, we carried out detailed stratigraphic, sedimentological, paleontological, and provenance analyses in the Gyangze and Sajia areas of southern Tibet,China. The Jiachala Formation consists of submarine fan deposits that lie in fault contact with the Zongzhuo Formation.Sandstone petrography together with U-Pb ages and Hf isotope ratios of detrital zircons indicate provenance from the Gangdese arc and central Lhasa terrane. Well preserved pollen or dinoflagellate cysts microfossils were not found in spite of careful research, and the youngest age obtained from zircon grain was ~84 Ma. Based on sedimentary facies, provenance analysis and tectonic position, we suggest that the Jiachala Formation was deposited during the Late Cretaceous(~88–84 Ma) in the trench formed along the southern edge of Asia during subduction of Neo-Tethyan oceanic lithosphere. 相似文献
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Mesozoic radiolarian chert from the middle sector of the Yarlung Zangbo suture zone,Tibet and its tectonic implications 总被引:5,自引:1,他引:5
ZHU Jie DU Yuansheng LIU Zaoxue FENG Qinglai TIAN Wangxue LI Jinping WANG Changping 《中国科学D辑(英文版)》2006,49(4):348-357
The middle sector of the Yarlung Zangbo suture zone stretches over 200 km long from Ngamring through Geding to Rinbung, roughly along Yarlung Zangbo River valley (Fig. 1). This belt resulted from the closure of the Tethyan ocean and the collision be- tween Indian plate and Lhasa block[1―8]. Lots of works demonstrated that rifting of the Tethyan basin in southern Tibet started from Triassic time. Initial oce- anic crust appeared in the Late Jurassic, and then ex- perienced a rapid sprea… 相似文献
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Abstract The Xialu chert radiolarian fauna is latest Jurassic–earliest Cretaceous in age (Pseudodictyomitra carpatica zone) and contains many taxa in common with coeval northern hemisphere middle‐latitude (temperate) radiolarian faunas represented by the Torinosu fauna in southwest Japan. Common elements include Eucyrtidiellum pyramis (Aita), Protunuma japonicus Matsuoka & Yao, Sethocapsa pseudouterculus Aita, Sethocapsa (?) subcrassitestata Aita, Archaeodictyomitra minoensis (Mizutani), Stichocapsa praepulchella Hori and Xitus gifuensis (Mizutani). The Xialu fauna is less similar to low‐latitude (tropical) assemblages represented by the Mariana fauna. For this reason, the Xialu fauna is regarded as representative of a southern hemisphere middle‐latitude (temperate) fauna. A mirror‐image bi‐temperate provincialism to the equator in radiolarian faunas is reconstructed for the Ceno‐Tethys and Pacific Ocean in latest Jurassic–earliest Cretaceous time. 相似文献
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A total of 11 earthquakes with 15 Rayleigh wave paths, recorded at 11 broadband digital PASSCAL seismometers installed in the Tibet Plateau by the Sino-U.S. joint research group, were used to determine the phase velocity and attenuation coefficient of surface waves in periods of 10–130 s. The average shear wave velocity and quality factor {ie271-1} structures in the crust and upper mantle were obtained in this region. The result shows the average {ie271-2} is low and there exists a high attenuation ({ie271-3}=93–141) layer in the crust. The depth range of the low {ie271-4} value layer (16–42 km) is consistent with the range of low velocity layer (21–51 km) in the crust. Below 63 km in the lower crust, {ie271-5} decreases with depth from 114 to 34 at depth of 180 km. The low shear wave velocity and low value of {ie271-6} at the same depth range in the crust indicate that the rocks in the range is probably melted or partially melted. According to the shear wave velocity structure, the average thickness of the crust is about 71 km and a clear velocity discontiniuty appears at the depth of 51 km. The low-velocity zone (4. 26 km/s) at depth of 96–180 km may be corresponding to the asthenosphere. 相似文献
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Inversion of Q value structure beneath the Tibet Plateau 总被引:1,自引:0,他引:1
InversionofQvaluestructurebeneaththeTibetPlateauJIAN-PINGWU(吴建平)andRONG--SHENGZENG(曾融生)(InstitutefoGeophysicsStateSeismologic... 相似文献
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Early Ordovician strongly peraluminous granite in the middle section of the Yarlung Zangbo junction zone and its geological significance 总被引:2,自引:0,他引:2
LA-ICP-MS zircon U-Pb isotopic dating and rock geochemical analysis were done of the Xarru granite in the middle section of the Yarlung Zangbo junction zone.Zircon 206Pb/238U weighted mean ages of 474.9±2.3 and 478.3±1.7 Ma have been obtained for two gneiss granite samples respectively,which represent the formation age of the granite.This is the first discovery of the Early Ordovician magmatism in the Yarlung Zangbo junction zone.The rocks are high-K calcic-alkalic granite,contain tourmaline but not hornblende,with aluminum saturation index(ASI) of A/CNK1.1(1.10–1.20),and are enriched in Rb,Th and U and relatively depleted in Ba,Nb,Sr,Zr,Ti and Eu.They are strongly peraluminous S-type granite,resulting from partial melting of argillaceous components in the crust in a syn-collisional setting.According to previous studies as well as the analysis in this paper,the formation of the Xarru granite is probably related to the Andean-type orogeny in the process of subduction of the Proto-Tethys Ocean towards the Gondwanaland,and it is a product of partial melting of the thickened upper crust as a result of collision between blocks or micro-blocks in the northern margin of the Gondwana supercontinent in the process of oceanic subduction.The Xarru granite is identified as the Early Ordovician granite,indicating that the wall rocks had probably formed in the Cambrian or Precambrian.A crustal basement may exist in the Xarru region. 相似文献