新疆鄯善康古尔塔格蛇绿岩及其大地构造意义   总被引：4，自引：1，他引：4  

李文铅  夏斌吴国干  王核王冉 《岩石学报》2005,21(6):1617-1632

康古尔塔格蛇绿岩的岩石组合为变质橄榄岩-堆晶橄榄岩-辉长岩-斜长花岗岩-辉绿岩-玄武岩。方辉橄榄岩（蛇纹岩）、蛇纹石化辉石岩、蚀变辉长岩与特罗多斯蛇绿岩中同类型岩石类似，岩石总体低钾。变质橄榄岩MgO／（MgO＋TFeO）为0．834～0．866，TiO，（wt％）为0．02％，为SSZ型蛇绿岩的变质橄榄岩。玄武岩的构造环境判别显示其形成于边缘海盆。放射虫硅质岩的Al2O3／（Al2O3＋Fe2O3）值平均为0．047，MnO／TiO2比值平均为0．93，Ce具负异常，Ce／Ce^＊=0．548，Lan／Cen=1．661．表明放射虫硅质岩的形成环境与洋中脊有密切关系。该蛇绿岩位于塔里木板块和哈萨克斯坦-准噶尔板块的艾比湖-康古尔塔格缝合线上，为一套无序产出的古生代北天山洋在该区的古洋壳残片。  相似文献   

Permo-Carboniferous Radiolarians from the Wupata＇erkan Group, Western South Tianshan, Xinjiang, China   总被引：1，自引：0，他引：1  

LIYuejun SUNLongde WUHaoruo ZHANGGuangya WANGGuolin HUANGZhibin 《《地质学报》英文版》2005,79(1):16-23

The Wupata‘erkan Group, also called Wupata‘erkan Formation, distributed in the South Tianshan, Xinjiang,China, mainly consists of gray and dark gray fine-grained clastic rocks, interlayered with volcanic rocks, carbonates and cherts. Some ultra-basic rocks (blocks) punctuate the formation. The formation was variously assigned to Silurian-Middle Devonian, Silurian-Lower Devonian, and pre-Devonian, mainly based on Atrypa bodini Mansuy, Hypothyridina parallelepipedia (Brour.) and Prismatophyllum hexagonum Yoh collected from the limestone interlayers, respectively.However, radiolarian fossils obtained from 24 chert specimens of the Wupata‘erkan Group, mainly include Albaillella sp.cf. A. undulata Deflandre, Albaillella sp. cf. A. paradoxa Deflandre, Albaillella cf. A. deflandrei Gourmelon, Albaillella sp. cf. A. indensis Won, Albaillella sp. cf. A. excelsa Ishiga, Kito and Imoto, Albaillella sp. and Latentifistulidae gen. et. sp.indet., are earliest Carboniferous and Late Permian. The earliest Carboniferous assemblage is characterized by Albaillella sp. cf. A. undulata Deflandre, Albaillella sp. cf. A. paradoxa Deflandre, Albaillella cf. A. deflandrei Gourmelon and Albaillella sp. cf. A. indensis Won, and the Late Permian assemblage by Albaillella sp. cf. A. excelsa Ishiga, Kito and Imoto. This new stratigraphic evidence indicates that the Wupata‘erkan Group is possibly composed of rocks with different ages from Silurian to Permian, and therefore, it is probably an ophiolite mrlange. The discovery of Late Permian Albaillella sp. cf. A. excelsa provides more reliable evidence supporting the existence of a Permian relic ancient oceanic basin in the western part of Xinjiang South Tianshan.  相似文献   

Seafloor spreading, obduction and triple junction tectonics of the Mineoka Ophiolite, Central Japan     

Yujiro Ogawa  Akiko Takahashi 《Tectonophysics》2004,392(1-4):131

The Tertiary Mineoka ophiolite occurs in a fault zone at the intersection of the Honshu and Izu forearcs in central Japan and displays structural evidence for three major phases of deformation: normal and oblique-slip faults and hydrothermal veins formed during the seafloor spreading evolution of the ophiolite at a ridge-transform fault intersection. These structures may represent repeated changes in differential stress and pore-fluid pressures during their formation. The second series of deformation is characterized by oblique thrust faults with Riedel shears and no significant mineral veining, and is interpreted to have resulted from transpressional dextral faulting during the obduction of the ophiolite through oblique convergence and tectonic accretion. This deformation occurred at the NW corner of a TTT-type (trench–trench–trench) triple junction in the NW Pacific rim before the middle Miocene. The third series of deformation of the ophiolite is marked by contractional and oblique shear zones, Riedel shears, and thrust faults that crosscut and offset earlier structures, and that give the Mineoka fault zone its lenticular (phacoidal) fabric at all scales. This deformation phase was associated with the establishment and the southward migration of the TTT Boso triple junction and with the kinematics of oblique subduction and forearc sliver fault development. The composite Mineoka ophiolite hence displays rocks and structures that evolved during its complex geodynamic history involving seafloor spreading, tectonic accretion, and triple junction evolution in the NW Pacific Rim.  相似文献   

西藏羌塘角木日地区二叠纪蛇绿岩的地质特征及意义   总被引：23，自引：24，他引：23  

翟庆国　李才程立人  张以春 《地质通报》2004,23(12):1228-1230

1：25万玛依岗日幅区域地质调查期间，在角木日地区发现了一套保存十分完整的蛇绿岩，岩石由放射虫硅质岩、枕状玄武岩、辉长辉绿岩和变质橄榄岩组成。这套岩石是羌塘中部地区发现的保存最为完整的蛇绿岩组合。  相似文献   

High-Ti type N-MORB parentage of basalts from the south Andaman ophiolite suite,India     

Rajesh K. Srivastava  R. Chandra  Anant Shastry 《Journal of Earth System Science》2004,113(4):605-618

A complete dismembered sequence of ophiolite is well exposed in the south Andaman region that mainly comprises ultramafic cumulates, serpentinite mafic plutonic and dyke rocks, pillow lava, radiolarian chert, and plagiogranite. Pillow lavas of basaltic composition occupy a major part of the Andaman ophiolite suite (AOS). These basalts are well exposed all along the east coast of southern part of the south AOS. Although these basalts are altered due to low-grade metamorphism and late hydrothermal processes, their igneous textures are still preserved. These basalts are mostly either aphyric or phyric in nature. Aphyric type exhibits intersertal or variolitic textures, whereas phyric variety shows porphyritic or sub-ophitic textures. The content of alkalies and silica classify these basalts as sub-alkaline basalts and alkaline basalts. A few samples show basaltic andesite, trachy-basalt, or basanitic chemical composition. High-field strength element (HFSE) geochemistry suggests that studied basalt samples are probably derived from similar parental magmas. Al₂O₃/TiO₂ and CaO/TiO₂ ratios classify these basalts as high-Ti type basalt. On the basis of these ratios and many discriminant functions and diagrams, it is suggested that the studied basalts, associated with Andaman ophiolite suite, were derived from magma similar to N-MORB and emplaced in the mid-oceanic ridge tectonic setting.  相似文献   

Geodynamic Information in Peridotite Petrology   总被引：12，自引：1，他引：12  

HERZBERG  CLAUDE 《Journal of Petrology》2004,45(12):2507-2530

Systematic differences are observed in the petrology and majorelement geochemistry of natural peridotite samples from thesea floor near oceanic ridges and subduction zones, the mantlesection of ophiolites, massif peridotites, and xenoliths ofcratonic mantle in kimberlite. Some of these differences reflectvariable temperature and pressure conditions of melt extraction,and these have been calibrated by a parameterization of experimentaldata on fertile mantle peridotite. Abyssal peridotites are examplesof cold residues produced at oceanic ridges. High-MgO peridotitesfrom the Ronda massif are examples of hot residues producedin a plume. Most peridotites from subduction zones and ophiolitesare too enriched in SiO₂ and too depleted in Al₂O₃ to be residues,and were produced by melt–rock reaction of a precursorprotolith. Peridotite xenoliths from the Japan, Cascades andChile–Patagonian back-arcs are possible examples of arcprecursors, and they have the characteristics of hot residues.Opx-rich cratonic mantle is similar to subduction zone peridotites,but there are important differences in FeO_T. Opx-poor xenolithsof cratonic mantle were hot residues of primary magmas with16–20% MgO, and they may have formed in either ancientplumes or hot ridges. Cratonic mantle was not produced as aresidue of Archean komatiites. KEY WORDS: peridotite; residues; fractional melting; abyssal; cratonic mantle; subduction zone; ophiolite; potential temperature; plumes; hot ridges  相似文献   

Timing and geochemical characters of the Sanchazi magmatic arc in Mianlüe tectonic zone, South Qinling     

LI Shuguang  HOU Zhenhui  YANG Yongcheng  Sun Weidong  ZHANG Guowei  LI Qiuli 《中国科学D辑(英文版)》2004,47(4)

The Sanchazi mafic-ultramafic complex in Mianlue tectonic zone, South Qinling can be subdivided into two blocks, i.e. Sanchazi paleo-magmatic arc and Zhuangkegou paleo-oceanic crust fragment (ophiolite). The Sanchazi paleo-magmatic arc is mainly composed of andesite, basaltic and basalt-andesitic gabbro (or diorite), andesitic dyke, plagiogranite and minor ultramafic rocks, which have typical geochemical features of island arc volcanic rocks, such as high field strength element (e.g. Nb, Ti) depletions and lower Cr, Ni contents. The Light rare earth element (LREE) and K enrichments of these rocks and zircon xenocrystals of 900 Ma from plagiogranite suggest that this magmatic arc was developed on the South active continental margin of the South Qinling micro-continent. The U-Pb age of (300 ± 61)Ma for zircons from plagiogranite indicates that the Mianlue paleo-oceanic crust was probably subducted underneath the South Qinling micro-continent in Carboniferous. This is consistent with the formation time (309Ma) of the Huwan eclogite originating from oceanic subduction in Dabie Mountains, suggesting that the Mianlue paleo-ocean probably extended eastward to the Dabie Mountains in Carboniferous. The high-Mg adakitic rocks in Sanchazi paleo-magmatic arc suggest that the subducted oceanic crust was relatively young (＜25Ma) and hot.  相似文献   

北祁连玉石沟蛇绿岩形成于晚震旦世的SHRIMP年龄证据   总被引：45，自引：5，他引：45  

史仁灯  杨经绥  吴才来  J.WOODEN 《地质学报》2004,78(5):649-657

玉石沟蛇绿岩位于青藏高原东北缘的北祁连山中部 ,由地幔橄榄岩、堆晶辉长岩、辉绿岩、枕状熔岩以及夹杂在其中的硅质岩组成。地幔橄榄岩主要是方辉橄榄岩 ,其主要氧化物成分较为单一 ,具 L REE富集、Eu亏损的 U形 REE配分模式 ,亏损强不相容元素 ;枕状熔岩具典型 MORB特征 ,在构造判别图解上位于 MORB和 IAT区域 ,指示蛇绿岩可能形成于类似于洋中脊的构造环境 ,并受到火山弧岩浆作用的影响。堆晶辉长岩具明显的 Eu正异常 ,其锆石离子探针 (SHRIMP) 2 0 6 Pb/2 38U加权平均年龄为 5 5 0± 17Ma,Th/U值为 0 .5 3～ 1.85 ,大于0 .2 3,为岩浆成因锆石 ,其年龄代表辉长岩的成岩时代 ,推断玉石沟蛇绿岩形成于晚震旦世。  相似文献   

Geochemistry of ophiolite cherts from the Qinling orogenic belt and implications for their tectonic settings     

ZHANG Chengli    GAO Shan    ZHANG Guowei  GUO Anlin  YUAN Honglin  LIU Xiaoming & WANG Jianqi . The key Laboratory of Continental Dynamics  Ministry of Education  Department of Geology  Northwest University  Xian China  . State Key Laboratory for Mineral Deposits Research  Nanjing University  Nanjing  China  . Department of Geochemistry  China University of Geosciences  Wuhan  China 《中国科学D辑(英文版)》2004,47(4)

Since the 1980s, one of the important progresses in the study of the Qinling orogenic belt is marked by findings of numerous ophiolite zones[1—4]. On the basis of the former orogenic models of the Paleozoic colli-sional orogeny[1,5,6] and the Mesozoic collision[7—9], another orogenic evolution model from the Paleozoic subduction-collision along the Shangdan suture to the Mesozoic final collision orogeny along the Mianle suture[3,10], including the relicts of the Jining orogeny, has been pr…  相似文献   

~(40)Ar-~(39)Ar GEOCHRONOLGY OF THE OPHIOLITE OF INDUS SUTURE ZONE,LADAKH,INDIA:IMPLICATION FOR THE TIMING OF INITIATION OF THE COLLISION     

Kanchan Pande  Rajneesh Bhutani 《地学前缘》2000,(Z1)

~(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