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1.
GEOCHEMISTRY OF THE PLIOCENE SHOSHONITIC ROCKS FROM OIYUG BASIN, CENTRAL TIBET  相似文献   

2.
DIFFUSION MODELLING IN GARNET FROM TSO MORARI ECLOGITE AND IMPLICATIONS FOR EXHUMATION MODELS1 ChakrabortyS ,GangulyJ.ContribMineralPetrol,1992 ,111:74~ 86 . 2 ChemendaAI ,BurgJ P ,MattauerM .EarthPlanetSciLett ,2 0 0 0 ,174:397~ 40 9. 3 ChemendaAI ,MattauerM ,MalavieilleJ ,etal.EarthPlanetSciLett ,1995 ,132 :2 2 5~ 2 32 . 4 GirardM ,BussyF .TerraNostra ,1999,99/ 2 ,5 7~ 5 8. 5 GuillotS ,SigoyerdeJ ,LardeauxJM ,etal.Contr…  相似文献   

3.
LOW TEMPERATURE DATING OF HIGH MOUNTAIN ROCKS:(U-Th)/He AGES FROM HIGHER HIMALAYAN SAMPLES, EASTERN NEPAL1 HouseMA ,WernickeBP ,FarleyKA .DatingtopographyoftheSierraNevada ,California ,usingapatite (U Th) /Heages[J].Nature,1998,396 (5 ) :6 6~ 6 9. 2 HubbardMS ,Harrison .4 0 Ar/ 3 9ArageconstraintsondeformationandmetamorphismintheMainCentralThrustzoneandTibetanSlab ,EasternNepalHimalaya[J].Tectonics,1989,8(4) :86 5~ 880 . 3 HubbardMS …  相似文献   

4.
MINERALIZATION AGES OF GOLD-HYDROTHERMAL DEPOSITS IN NORTHERN ZONE OF EASTERN KUNLUN MOUNTAINS BASED ON FISSION TRACK ANALYSIStheOpenLaboratoryofNuclearAnalysisTechniques;;ChineseAcademyofSciences  相似文献   

5.
HETEROGENEITY OF THE LITHOSPHERE IN TIBETAN PLATEAU ON THE CONSTRAINTS OF MAGMATISM  相似文献   

6.
PETROLOGY AND GEOCHEMISTRY OF CENOZOIC VOLCANIC ROCKS FROM THE CENTRE OF QIANGTANG,TIBET  相似文献   

7.
9个黑云母样品高精度~(40)Ar/~(39)Ar法定年结果表明,囊谦盆地高钾岩浆的活动年限为37.1~37.8Ma。高钾岩石在地质背景和岩石类型上与青藏东缘发现的两类高钾岩系中的早期高钾岩浆岩具有可比性,它们可能形成于相同的构造背景。结合前人的同位素年代学研究资料,金沙江-红河构造带南、北段高钾岩浆活动的时间分别为40~24Ma和40~33Ma,南、北段高钾岩浆活动时间的差异可能指示陆内俯冲作用时限的差异。  相似文献   

8.
INDIA/ASIA CONVERGENCE AND HIMALAYAN SHORTENING   总被引:1,自引:0,他引:1  
INDIA/ASIA CONVERGENCE AND HIMALAYAN SHORTENING  相似文献   

9.
Kohistan Sequence has been considered as island arc formed during the subduction of oceanic lithosphere at the leading edge of northward moving Indian continent.. Sedimentary sequences indicate that formation of the intra\|oceanic Kohistan arc began in early Cretaceous time. The isotopic data demonstrate the involvement of enriched, DUPAL type mantle, suggesting that Kohistan arc was formed at or south of the present equator (Khan et al., 1997). The Intra oceanic phase of Kohistan lasted until sometime between 102 and 85 Ma, when Kohistan collided with Asia. From this time until collision with India about 50 Ma ago, Kohistan existed as Andean\|type margin. This paleomagnetic study is from the volcanic and plutonic rocks exposed in Gupis\|Shamran area (west of Gilgit) in northern part of the Kohistan arc. According to geochronological data these rocks were formed 61~55Ma ago (Treloar et al., 1989), when Kohistan was existing as Andean\|type margin. Seven to nine samples were collected from nine sites of Shamran volcanics (58±1)Ma and from five sites of Pingal, Gupis, and Yasin plutons (Ar\|Ar hornblende ages ranges from 61~52Ma). On the basis of one Rb\|Sr age of (59±2)Ma from these plutons, the above\|mentioned Ar/Ar ages may be regarded as reasonable intrusion ages of these plutons (Searle, 1991).  相似文献   

10.
This paper presents the results of geochronological studies of the Tomtor alkaline-ultramafic pluton, one of the largest Nb, Y, Sc, and TR deposits. A new scheme of its magmatism is given. The current K-Ar and Rb-Sr ages of different igneous rocks of the Tomtor pluton range from 800 to 250 Ma [Zaitsev et al., 1992; Frolov et al., 2003]. Such dispersion is probably related to the intense carbonatization of the rocks. The U-Pb zircon and 40Ar/39Ar mica ages indicate two stages of the formation of the pluton (700 and 400 Ma), which agrees well with the age of cycles of rift-related tectonogenesis of the Siberian platform.  相似文献   

11.
IMPLICATIONS OF THE DEEP-SEATED XENOLITHS IN CENOZOIC BASALT IN KANGXIWA, WEST KUNLUN,CHINA  相似文献   

12.
I.McDermid    J.C.Aitchison    Badengzhu    A.M.Davis    Liu Jianbing    Luo Hui    Wu Hiyun    S.V.Ziabrev  WT  ”BX 《地学前缘》2000,(Z1)
ZEDONG TERRANE, A MID CRETACEOUS INTRA-OCEANIC ARC, SOUTH TIBET  相似文献   

13.
~(40)Ar-~(39)Ar GEOCHRONOLGY OF THE OPHIOLITE OF INDUS SUTURE ZONE,LADAKH,INDIA:IMPLICATION FOR THE TIMING OF INITIATION OF THE COLLISION1 BeckRA ,BurbankDW ,etal.Nature,1995,373( 55) . 2 DeweyJF ,etal.EclogaegeolHelv ,1989,82 ( 717) . 3 RowleyDB .EarthandPlanetaryScienceLetters,1996 ,14 5( 1) . 4 SharmaKK .PhysicsandChemistryoftheEarth ,1990 ,17. 5 VenketasanTR ,PandeK ,GopalanK .EarthandPlanataryScienceLetters,1993…  相似文献   

14.
青藏高原东部贡觉盆地新生代火山岩的K-Ar稀释法年龄   总被引:4,自引:0,他引:4  
通过新生代高钾钙碱性中、酸性火山岩的年代学研究来了解青藏高原的隆升特征,首次报道了藏东贡觉盆地新生代7个火山岩样品的K-Ar定年结果.全岩和黑云母的表面年龄均在40.8~46.2Ma间(平均值为44.2Ma).样品中放射成因Ar与K构成了一条相关性良好的、几乎通过原点的线性等时线,表明它们有相同的成因和相近的形成时代。而且样品中可能既无过剩Ar,也无放射成因Ar的丢失,代表着真实的成岩年龄(始新世中期).火山活动发生在印度—欧亚板块碰撞(50 Ma左右)后形成的构造环境中。受陆内水平剪切—走滑断裂带控制.结合前人对藏东地区岩浆活动的年代学研究成果.表明青藏高原东缘新生代岩浆活动具多期性.这种多期性可能反映着青藏高原阶段性隆升的壳—幔相互作用。  相似文献   

15.
印度—亚洲大陆主碰撞过程的火山作用响应   总被引:203,自引:7,他引:203  
广泛发育在西藏冈底斯岩浆岩带中的林子宗火山岩及其与下伏地层间的区域性不整合 ,提供了印度—亚洲大陆碰撞 (在西藏南部 )的构造火成岩新证据。岩石学、主元素、微量元素、稀土元素及Nd Sr Pb同位素地球化学研究表明 ,林子宗火山岩早期带有较多陆缘弧火山岩特征 ,中期开始出现标志陆内岩浆活动的钾玄岩 ,晚期更多地显示了加厚陆壳条件下火山岩的特点 ,记录了由新特提斯俯冲消减末期过渡到印度—亚洲大陆碰撞的信息。系统的40 Ar/3 9Ar同位素测年确定林子宗火山岩的年龄区间为 4 0 .84~ 6 4 .4 7Ma ;其底部年龄给出了林子宗火山岩与下伏地层间不整合形成时间的最晚时限 (~ 6 5Ma)。该不整合面上、下之地层在沉积相、变形样式与变形程度上均截然不同 ,反映形成环境的重大变化 ,标志着一次重大的地质事件。根据上述事实 ,结合青藏高原岩浆活动的区域时空分布 ,及西藏南部地层、古生物与沉积研究成果 ,笔者认为印度—亚洲大陆碰撞开始于 6 5Ma左右(K/T界限时间 )。  相似文献   

16.
he 2500km long Indus\|Tsangpo Suture has been recognized as one of the best examples of continent to continent collisional Suture Zone. It has come into existence as a result of subduction followed by continental collision (55~60Ma) between Indian (Sinha, 1989, 1997; Sinha et al., 1999) and Eurasian plates. While considering the recent palaeogeographic reconstruction of Pangea during late Palaeozoic it appears that a southern belt of Asian microcontinents stretching from Iran and Afghanistan through southern Tibet to western Thailand, Malaysia and Sumatra, comprise several continental blocks and numerous fragments that have coalesced since the Mid\|Palaeozoic along with the closure of Tethys. The origin, migration, assembly and timing of accretion of all these blocks to their present geotectonic position is not well known and there is no Permo—Triassic crust left in the present day Indian Ocean. The oldest ocean crust adjacent to the west African and Antarctic margin is of early or middle Cretaceous age (approximately 140~100Ma) (Searle, 1991). The Karakoram\|Hindukush microplate in the west and the Qiangtang\|Lhasa block in the central and eastern segment of South Asia margin are among those blocks already welded with Asian plates around 120~130Ma ago, before the collision of India (55~60Ma) with the collage of plates forming Peri\|Gondwanian microcontinents. But the reconstruction of palaeogeographic configuration remain incomplete due to paucity of authentic geologic information available from Karakoram, Pamir and Western Tibet. Prior to our discovery no early Permian plant remains and palynomorphs were ever reported from Karakoram terrane. Our discovery of Early Permian remains and late Asselian (about 280~275Ma) palynomorphs provides crucial clue regarding the palaeogeographic reconstruction of the Karakoram\|Himalayan block in the Permian time.  相似文献   

17.
THE EARLY UPLIFT IN NORTHERN TIBETAN PLATEAU: EVIDENCE FROM THE STUDY ON CENOZOIC VOLCANIC ROCKS IN QIANGTANG REGION  相似文献   

18.
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   

19.
RESEARCH PROGRESS OF ALTYN FAULT IN WESTERN CHINA   总被引:2,自引:0,他引:2  
RESEARCH PROGRESS OF ALTYN FAULT IN WESTERN CHINATheresearchisfundedbyNSFC (No.4 9772 157)  相似文献   

20.
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