欧亚大陆及边缘海岩石圈的结构特性   总被引：2，自引：0，他引：2  

蔡学林  朱介寿  曹家敏  程先琼 《地学前缘》2007,14(3):21-38

从地球层块结构的研究思路出发,运用构造解析的理论和方法,对东亚及西太平洋地区人工地震测深和天然地震面波层析成像进行构造解析,发现岩石圈中下部存在形态各异、大小不等的高速块体,结合地质学、地球化学及其他地球物理学标志的综合研究将其称为幔块构造,高速块体或幔块构造是控制东亚西太平洋岩石圈构造格局和岩石圈表层构造变形最基本条件之一。在系统研究该区岩石圈高速块体或幔块构造三维几何结构基础上,建立起东亚西太平洋岩石圈八种三维几何结构型式:克拉通陆根状结构、高原陆根状结构、造山带楔状结构、碎块状结构、香肠状结构、哑铃状结构、藕节状结构和板状结构,以及岩石圈形成与构造演化四种构造类型:克拉通型岩石圈、增厚型岩石圈、减薄型岩石圈和大洋型岩石圈。文章在详细论述岩石圈各结构构造类基本特征的基础上,认为全球最大的青藏高原具有增厚型岩石圈特性,存在大陆根,并且大陆根正在增厚过程中;地震层析成像显示,研究区存在全球最大的东亚大陆巨型裂谷体系,具有减薄型岩石圈特性,新生代晚期东亚大陆巨型裂谷体系被西太平洋沟弧盆体系叠加与改造。根据岩石圈三维结构型式,探讨了岩石圈形成机制与演化模式,东亚大陆边缘岩石圈大规模伸展拆沉减薄作用以及软流圈和地幔物质上涌加热作用与青藏高原岩石圈大规模俯冲碰撞?入增厚作用是东亚大陆及边缘海晚中生代以来地幔动力学最基本的表现型式,从而形成全球最大的青藏高原和全球最大的东亚大陆巨型裂谷体系。  相似文献   

Petrology and geochemistry of Zijinshan alkaline intrusive complex in Shanxi Province, western North China Craton: Implication for magma mixing of different sources in an extensional regime   总被引：11，自引：0，他引：11  

Jifeng Ying  Hongfu Zhang  Min Sun  Yanjie Tang  Xinhua Zhou  Xiaoming Liu 《Lithos》2007,98(1-4):45-66

In situ zircon U–Pb ages and Hf isotopic compositions and whole rock geochemical and Sr–Nd–Pb isotopic data are presented for the Zijinshan alkaline intrusive complex from the Shanxi Province, western North China Craton. Salic rocks dominate the complex with the monzonite occurring in the outermost and pseudoleucite phonolitic breccia in the center. The intrusion took place 127 Ma ago with the earliest emplacement of monzonite and the termination of cryptoexplosive pseudoleucite phonolitic breccia. All rocks from this complex show LREE enrichment and HFSE depletion and exhibit enriched to depleted Sr–Nd isotopic features. The presence of inherited zircons and enriched Hf isotopic compositions in zircon rims, along with the enriched whole rock Sr–Nd isotopic compositions, indicate that the monzonite was formed through the mixing of lithospheric mantle-derived magma with lower crust-derived melts. The diopside syenite and nepheline-bearing diopside syenite are more depleted than the monzonite in terms of the Sr and Nd isotopes, together with their very high concentrations of LILE, we proposed that they originated from a mixed mantle source of enriched lithospheric mantle and depleted asthenosphere. The nepheline syenite has very low concentrations of MgO, Ni, Cr, suggesting that the magma underwent significant crystal fractionation. The most depleted Sr and Nd isotopic compositions ((⁸⁷Sr/⁸⁶Sr)_i = 0.7036–0.7042, ε_Nd(t) = − 0.2–0.3) among all rock types indicate a great contribution of asthenosphere to the nepheline syenite. The Zijinshan complex and its related crust-mantle interaction occurred in an extensional environment which resulted in continuously asthenospheric upwelling. Such an extensional environment might have been developed during the post-orogenic stage of the Late Paleozoic amalgamation of North China Craton with Mongolian continents and subsequent Mongol–Okhotsk ocean closure.  相似文献   

吉林双辽地区橄榄岩包体中熔体-岩石作用特征及其对地幔交代作用的启示     

于宋月徐义刚  黄小龙葛文春 马金龙 《岩石矿物学杂志》2007,26(3):213-222

吉林双辽地区古近纪玄武岩中一方辉橄榄岩包体记录了上地幔交代作用的信息。原生斜方辉石被交代成因的单斜辉石和橄榄石所围绕,或形成反应边结构,或斜方辉石残留在次生单斜辉石中。这些反应结构仅出现在尖晶石的周围。电子探针分析表明次生单斜辉石具有高Mg#、Cr#和CaO/Al2O3比值,次生橄榄石高Mg#、CaO和Cr2O3,被交代的尖晶石边部高Cr#、CaO。由于交代作用并未影响橄榄岩体系的Mg#,而且熔体-岩石反应结构指示Opx(斜方辉石) Sp(尖晶石) 熔体(Ⅰ)→Cpx(单斜辉石) Ol(橄榄石) 熔体(Ⅱ),结合实验以及文献资料,认为双辽地区的岩石圈地幔受到了硅酸盐熔体的交代。这种交代导致橄榄岩中斜方辉石逐渐减少,单斜辉石和橄榄石逐渐增加,从而使方辉橄榄岩渐变成易剥橄榄岩。这种交代现象可能发生在软流圈-岩石圈接触带上的熔-岩反应区,暗示了在古近纪双辽地区岩石圈减薄和软流圈上涌导致的软流圈-岩石圈的相互作用仍在继续。  相似文献   

塔里木板块西南缘钾质煌斑岩地球化学及源区特征   总被引：5，自引：0，他引：5       下载免费PDF全文

柴凤梅帕拉提&#  阿布都卡迪尔张招崇毛景文董连慧木合塔尔&#  扎日 《地质论评》2007,53(1):11-21

塔里木板块西南缘克里阳山区的钾质煌斑岩呈脉状产于前寒武纪埃连卡特群变质沉积岩中,其主要岩石类型有:金云母透辉石煌斑岩、假白榴石透辉石煌斑岩和含球粒透辉石煌斑岩。所有岩石具有低的SiO2(41.31%～44.84%)、TiO2(0.75%～0.86%)和高的MgO(7.30%～11.33%)和K2O(4.01%～6.01%)含量,K2O/Na2O比值介于2.77～12.49之间。同时,它们具有富集大离子亲石元素(Rb、Sr、Ba、Th、U、K)和轻稀土元素(LREE),相对亏损高场强元素(Nb、Ta、Zr、Hf、Ti)的特征,并且具有高的Sr同位素比值、相似的高度分异的REE配分模式。这些岩石的母岩浆来自于金云母角闪石石榴子石二辉橄榄岩的富集地幔,是该富集地幔部分熔融约5%～10%的产物,岩浆在上升侵位过程中受到地壳物质的混染较弱。富集地幔是俯冲的板块释放的富含钾质流体交代的结果。  相似文献   

Contrasting magma types and timing of intrusion in the Permian layered mafic complex of Mont Collon (Western Alps,Valais, Switzerland): evidence from U/Pb zircon and <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar amphibole dating     

Philippe Monjoie  François Bussy  Urs Schaltegger  Andreas Mulch  Henriette Lapierre  Hans-Ruedi Pfeifer 《Swiss Journal of Geoscience》2007,100(1):125-135

  相似文献   

Pyroxenites from the Southwest Indian Ridge, 9-16{degrees}E: Cumulates from Incremental Melt Fractions Produced at the Top of a Cold Melting Regime     

Dantas  C.; Ceuleneer  G.; Gregoire  M.; Python  M.; Freydier  R.; Warren  J.; Dick  H. J. B. 《Journal of Petrology》2007,48(4):647-660

The Southwest Indian Ridge (SWIR) at 9–16°E and 52–53°Sis characterized by ultra-slow, oblique spreading and containsone of the few documented occurrences of pyroxenite veins associatedwith abyssal peridotites. The origin of these uncommon lithologiesis still debated. We present a detailed study (including electronmicroprobe and laser ablation inductively coupled plasma massspectrometry) of spinel websterites collected during Cruise162, Leg 9, of the R.V. Knorr. Rare earth element patterns inclinopyroxenes (Cpx) lead us to discard a possible origin ofthe pyroxenites as residues from partial melting of garnet pyroxenites(i.e. relics of a layered mantle protolith). Their compositionand cumulate texture (when not obscured by mylonitization relatedto emplacement on the seafloor) are better interpreted in termsof fractional crystallization from a basaltic melt at relativelyhigh pressure. Evidence for a high pressure of crystallizationincludes the lack of plagioclase in the cumulate assemblageand the high Al₂O₃ contents of the pyroxenes: up to 5 wt % inorthopyroxene (Opx) and up to 7 wt % in Cpx. These values areamong the highest reported for pyroxenes in a mid-ocean ridgesetting. Sub-solidus breakdown of spinel to plagioclase (nowaltered) is observed in one sample, providing a rough estimateof the final equilibration pressure of these cumulates, around0· 6–0· 7 GPa (plagioclase–spineltransition for a bulk pyroxenite composition). The inferredpyroxenite parent melts were close to equilibrium with the associatedresidual peridotites; some samples have a slightly evolved compositionin terms of the Mg-number [Mg/(Mg + total Fe)]. These parentalmelts had major and trace element compositions consistent witha mid-ocean ridge basalt (MORB) affinity, although they werenot rigorously identical to MORB. Among other characteristics,these melts were relatively depleted in highly incompatibleelements. We propose that they correspond to the latest, shallowest,incremental melt fractions produced during fractional decompressionmelting of a normal MORB (N-MORB) mantle source. These meltsexperienced fractional crystallization as soon as they segregatedfrom the peridotite matrix, moved upward, and crossed the lithosphere–asthenosphereboundary (defined here as the base of the conductive lid). Asa consequence, these shallow melt fractions produced beneathmid-ocean ridges did not fully mix with melt fractions producedand extracted at greater depths. Our study provides concreteevidence for the actuality of pyroxene crystallization in meltchannels beneath mid-ocean ridges at relatively high pressures,a process frequently invoked to account for the ‘pyroxeneparadox’ in MORB petrogenesis. KEY WORDS: abyssal pyroxenites; cumulates; lithospheric mantle; melt migration; Southwest Indian Ridge  相似文献   

Mantle peridotites from the Western Pacific   总被引：1，自引：0，他引：1  

Shoji Arai  Natsue Abe  Satoko Ishimaru 《Gondwana Research》2007,11(1-2):180

We review petrographical and petrological characteristics of mantle peridotite xenoliths from the Western Pacific to construct a petrologic model of the lithospheric mantle beneath the convergent plate boundary. The peridotite varies from highly depleted spinel harzburgite of low-pressure origin at the volcanic front of active arcs (Avacha of Kamchatka arc and Iraya of Luzon–Taiwan arc) to fertile spinel lherzolite of high-pressure origin at the Eurasian continental margin (from Sikhote-Alin through Korea to eastern China) through intermediate lherzolite–harzburgite at backarc side of Japan island arcs. Oxygen fugacity recorded by the peridotite xenoliths decreases from the frontal side of arc to the continental margin. The sub-arc type peridotite is expected to exist beneath the continental margin if accretion of island arc is one of the important processes for continental growth. Its absence suggests replacement by the continental lherzolite at the region of backarc to continental margin. Asthenospheric upwelling beneath the continental region, which has frequently occurred at the Western Pacific, has replaced depleted sub-cratonic peridotite with the fertile spinel lherzolite. Some of these mantle diapirs had opened backarc basins and strongly modified the lithospheric upper mantle by metasomatism and formation of Group II pyroxenites.  相似文献   

Shear wave splitting as a diagnostic of variable anisotropic structure of the upper mantle beneath central Fennoscandia   总被引：1，自引：0，他引：1  

L. Vecsey  J. Plomerov  E. Kozlovskaya  V. Babu&#x;ka 《Tectonophysics》2007,438(1-4):57-77

We analyze splitting of shear waves recorded during the SVEKALAPKO passive seismic experiment in south-central Finland to study fabrics of the mantle lithosphere of the Precambrian region and thus to bring information into a debate on existence of plate tectonics or its forms in the early stage of continent formation. Geographical variations of the splitting parameters and their distinct dependence on direction of wave propagation through the upper mantle allow us to identify six domains of the central Fennoscandian mantle lithosphere, including the Proterozoic–Archean transition, and to model their fabrics by joint inversion of body wave anisotropic parameters. Fabrics of the Archean mantle lithosphere can be approximated by a peridotite aggregate with lineation a dipping to the NE. On the other hand, anisotropy of the Proterozoic mantle lithosphere is weaker and we model its fabric by the (a, c) foliations dipping to the SE. We present a 3D self-consistent anisotropic model of the Proterozoic and Archean upper mantle along the SW-NE profile in the south-central Finland. Boundaries of inter-growing wedges of the Proterozoic and Archean mantle lithospheres explain the longitudinal and shear wave propagation and polarization, mantle xenolith ages, surface wave tomography and location of the upper mantle reflectors. We interpret the six anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro-continents assembled.  相似文献   

Contrasting Peridotite Types in the Dabie UHP Belt, Eastern China: the Raobazhai and Bixiling Ultramafic-mafic Complex     

Jianping Zheng  Min Sun  W. L. Griffin  Mei-Fu Zhou  Guochun Zhao 《矿物岩石地球化学通报》2007,26(Z1)

The Dabie UHP metamorphic belt, central China,contains two contrasting types of mafic-ultramafic complex. The Bixiling peridotite in the southern Dabie terrane contains abundant garnet (21.1-32.2 vol% )and thus has high CaO + Al2O3 (9.81-15.9 wt% ).  相似文献   

大陆岩石圈流变学研究进展          下载免费PDF全文

刘绍文  王良书  李成 《地球物理学进展》2007,22(4):1209-1214

大陆岩石圈流变学是固体地球科学领域的基本问题，也是理解大陆变形的动力学过程和构造演化史的关键.本文对近年来大陆岩石圈流变学的研究进展进行了综述.重点讨论大陆岩石圈流变学的纵向分层和横向分块特性及流变学与地震活动性、壳－幔解耦及下地壳流动变形的地球动力学意义和中国大陆地区岩石圈流变学研究状况.最后，对大陆岩石圈流变学研究存在的问题和未来的研究方向做了一定的探讨和展望.  相似文献