北天山地区活动逆断裂-褶皱带构造与潜在震源区估计   总被引：27，自引：7，他引：20       下载免费PDF全文

杨晓平  冯先岳 《地震地质》1998,20(3):2-200

北天山山前逆断裂－褶皱带是典型的大陆内部活动挤压构造,该地区的地表活动构造、隐伏活动构造及活动背斜都受地下深处近水平滑脱断层控制。对１９０６年玛纳斯地震（Ｍ７．７）的发震构造、地表变形与破裂特征和山前活动逆断裂带上古地震的研究表明,北天山山前隐伏活动深断坡具备大地震发生的构造条件,大致以金钩河为界分为东西两段,相应地构成两个大地震潜在震源（Ｍ８）。山前第２条玛纳斯逆断裂－褶皱带和第３条独山子逆断裂－褶皱带中的各个活动背斜,以及西湖隆起等可能是８个中强地震的潜在震源（Ｍ６）。  相似文献   

Magmatic changes during the stabilisation of a cordilleran fold belt: the Late Carboniferous–Triassic igneous history of eastern New South Wales, Australia     

Graziella Caprarelli  Evan C. Leitch 《Lithos》1998,45(1-4):413-430

In a 60 Ma interval between the Late Carboniferous and the Late Permian, the magmatic arc associated with the cordilleran-type New England Fold Belt in northeast New South Wales shifted eastward and changed in trend from north–northwest to north. The eastern margin of the earlier (Devonian–Late Carboniferous) arc is marked by a sequence of calcalkaline lava flows, tuffs and coarse volcaniclastic sedimentary rocks preserved in the west of the Fold Belt. The younger arc (Late Permian–Triassic) is marked by I-type calcalkaline granitoids and comagmatic volcanic rocks emplaced mostly in the earlier forearc, but extending into the southern Sydney Basin, in the former backarc region. The growth of the younger arc was accompanied by widespread compressional deformation that stabilised the New England Fold Belt. During the transitional interval, two suites of S-type granitoids were emplaced, the Hillgrove Suite at about 305 Ma during an episode of compressive deformation and regional metamorphism, and the Bundarra Suite at about 280 Ma, during the later stages of an extensional episode. Isotopic and REE data indicate that both suites resulted from the partial melting of young silicic sedimentary rocks, probably part of the Carboniferous accretionary subduction complex, with heat supplied by the rise of asthenospheric material. Both mafic and silicic volcanic activity were widespread within and behind the Fold Belt from the onset of rifting (ca. 295 Ma) until the reestablishment of the arc. These volcanic rocks range in composition from MORB-like to calcalkaline and alkaline. The termination of the earlier arc, and the subsequent widespread and diverse igneous activity are considered to have resulted from the shallow breakoff of the downgoing plate, which allowed the rise of asthenosphere through a widening lithospheric gap. In this setting, division of the igneous rocks into pre-, syn-, and post-collisional groups is of limited value.  相似文献   

西秦岭北缘断裂带的深部构造特征及其与地震活动的关系   总被引：1，自引：0，他引：1  

董治平  雷芳 《内陆地震》1996,10(3):224-234

西秦岭北缘断裂带是中国的一条主要超壳断裂带，也是祁连褶皱系与秦岭褶皱系的分界断裂带。利用近几年取得的人工地震、重力、航磁、地热等资料，从地质和地球物理两个方面就该断裂及其两侧的深部构造特征作一初步分析并讨论了断裂带的最新活动及地震活动。  相似文献   

Structural study of a semiductile strike-slip system in the Central Iberian Zone (Variscan Fold Belt,Spain): structural controls on gold deposits     

E. Gonzalez-Clavijo  M. A. Diez-Balda  F. Alvarez 《International Journal of Earth Sciences》1993,82(3):448-460

The Villalcampo shear system is a regional dextral strike-slip fault zone that affects Late Variscan granites and their metamorphic country rocks over an area of about 150 km². The detailed geometry of this subvertical north-west—south-east shear zone is outlined. The system forms an extensional fan to the northwest and extends to the south-east as a broad extensional duplex. Particular attention is focused on the distribution of fault rocks and associated veins in its north-west splay. A structural study of the shear bands (encompassing both geometric and kinematic criteria) and a microscopic study of the fault rocks has led to the interpretation of the system as a brittle—ductile shear zone. Calculations give a shear strain value of = 1.5 and a minimum displacement of s = 3700 m. The localization of gold mineralization in mylonite-filled subvertical extensional veins is a product of the formation of the Villalcampo shear system. The subvertical faults and veins underwent a process of cyclical sealing and reopening. As such they acted as valves controlled by fluid pressure regulating fluid—rock interactions and gold deposition. Conditions favouring these processes occur near the base of the seismogenic zone in the vicinity of the frictional—quasi-plastic transition at mid-greenschist metamorphic conditions (T = 350°C and 10–15 km depth).  相似文献   

Silurian to mid-Devonian basin development of the Melbourne Zone, Lachlan Fold Belt, southeastern Australia   总被引：1，自引：0，他引：1  

C. McA. Powell  P. W. Baillie  A. H. M. VandenBerg   《Tectonophysics》2003,375(1-4):9

The Melbourne Zone comprises Early Ordovician to Early Devonian marine turbidites, which pass conformably upward into a mid-Devonian fluviatile succession. There are four pulses of Silurian to mid-Devonian deep-marine sandstone-dominated sedimentation: Early Silurian (late Llandovery), Late Silurian (Ludlow), earliest Devonian (Lochkovian) and late Early Devonian (Emsian). Two dispersal patterns have been defined using more than 1100 palaeocurrent measurements, mainly from sole marks and cross-laminations in graded beds, together with sandstone compositions. The older pattern, of Silurian to earliest Devonian age, contains the lowest three sandstone pulses. Palaeocurrents and provenance define a wedge of southwesterly derived sediment, of largely cratonic provenance, thinning eastward. This older dispersal pattern is part of an Early Ordovician to earliest Devonian east-facing passive continental margin succession. Palaeocurrents and provenance in the Emsian sandstone pulse comprise three patterns: (1) west- to southwesterly directed palaeocurrents associated with fine- to coarse-grained, locally conglomeratic, lithic sandstones containing a high proportion of volcanic detritus; (2) east- to northeasterly directed palaeocurrents associated with fine- to medium-grained quartz-lithic sandstones; (3) north- to northwesterly and south- to southeasterly directed palaeocurrents associated with fine- to medium-grained sandstones of variable lithic composition. The palaeocurrent and provenance pattern defines a NNW-elongate basin with a tectonically active eastern margin, and is similar to the coeval Mathinna basin of northeastern Tasmania. Both basins are part of the same system of wrench basins, which developed along the western side of the Wagga–Omeo Metamorphic Belt during the earliest Devonian to Middle Devonian. The change in tectonic setting in the earliest Devonian appears to have occurred during an interval of significant dextral translation of the eastern Lachlan Fold Belt towards the SSE along the Governor and associated fault zones.  相似文献   

龙首山直沟门岩体特征及构造环境   总被引：2，自引：0，他引：2  

胡能高  许安东  杨家喜 《地球科学与环境学报》2005,27(2):5-11

直沟门岩体(年龄374±38Ma)侵入于华北板块西缘的龙首山岩群,主要由花岗岩、二长花岗岩等岩性组成。根据野外产状和岩相学特征可划分为3个单元,从早到晚依次为:直沟门单元、湾湾圈单元和马路湾单元。岩体的w(SiO2)65.94%～75.18%,w(K2O)2.36%～4.35%,w(Na2O)3.53%～5.47%,总体上w(Na2O)≈w(K2O)。随w(SiO2)增大w(CaO),w(TFeO),w(MgO)减少,所有岩石均具铝弱过饱和,ANKC=1.01～1.09,岩浆类型属钙碱性系列,σ=1.99～2.64,皮可克指数为55.6。Li,Cs,Rb质量分数较低,而Ba,Sr较高,从早到晚大体存在Rb/Sr减少,而Sr,Ba,Co和Ba/K增加。湾湾圈和马路湾单元在∑REE((152.11～171.94)×10-6),∑LREE/∑HREE(24.81～26.92),δEu(0.91～1.10)以及配分模式等方面是相似的,与其相比,直沟门单元的∑REE(46.62×106),∑LREE/∑HREE(3.52)低,而δEu(1.60)高。w(La)与w(La)/w(Sm)大体存在正相关,δEu,∑REE与DI变化也相一致。直沟门岩体形成于祁连造山带碰撞阶段之后,属后碰撞花岗岩。在w(CaO)/w(Na2O)对w(Al2O3)/w(TiO2)图上,与拉克伦褶皱带后碰撞花岗岩的投影区相近。直沟门岩体的岩浆可能源自祁连褶皱带下冲火山岩。  相似文献   

Integrating structural geology and petroleum systems modeling – A pilot project from Bolivia's fold and thrust belt     

Friedemann Baur  Matias Di Benedetto  Thomas Fuchs  Carolyn Lampe  Simone Sciamanna 《Marine and Petroleum Geology》2009

For the first time, a new approach to petroleum systems analysis is presented which allows full integration of tectonic and palinspastic restoration with three-dimensional (3D), PVT-controlled, multi-component, three-phase petroleum migration analysis through time. A systematic modeling study has been applied to a study area dominated by fold and thrust belts located in the Sub Andean orogeny near Tarija, Bolivia. The project has been performed with a special focus on the simulation technique and on the correct distribution of temperature, source-rock maturity and pressure development through time with reference to its input data. This is the first pilot project presenting a 3D numerical model in a compressional structural regime to which the basin modeling approach has been applied to explain the observed distribution of temperature, pressure, maturity and petroleum accumulations in general.  相似文献   

Mechanical aspects of thrust faulting driven by far-field compression and their implications for fold geometry   总被引：1，自引：0，他引：1  

Pablo F. Sanz  Ronaldo I. Borja  David D. Pollard 《Acta Geotechnica》2007,2(1):17-31

In this paper we present a mechanical model that intends to captures the kinematical aspects of thrust fault related folds induced by regional-scale far-field contraction. Fold shapes may be the only surface evidence of the geometry of underlying faults, so complex fault interactions are assessed in terms of how they influence fold geometry. We use the finite element method to model the fold and finite deformation frictional contact to model the activation and evolution of slip throughout preexisting faults. From several simulated 2D fault patterns we infer how one may form an anticline similar to that observed at Sheep Mountain Anticline, Wyoming.  相似文献   

Lewis Ponds, a hybrid carbonate and volcanic-hosted polymetallic massive sulphide deposit, New South Wales, Australia     

Michael W. Agnew  Ross R. Large  Stuart W. Bull 《Mineralium Deposita》2005,39(8):822-844

The Lewis Ponds Zn–Pb–Cu–Ag–Au deposit, located in the eastern Lachlan Fold Belt, central western New South Wales, exhibits the characteristics of both volcanic-hosted massive sulphide and carbonate-hosted replacement deposits. Two stratabound massive to disseminated sulphide zones, Main and Toms, occur in a tightly folded Upper Silurian sequence of marine felsic volcanic and sedimentary rocks. They have a combined indicated resource of 5.7 Mt grading 3.5% Zn, 2.0% Pb, 0.19% Cu, 97 g/t Ag and 1.9 g/t Au. Main Zone is hosted by a thick unit of poorly sorted mixed provenance breccia, limestone-clast breccia and quartz crystal-rich sandstone, whereas Toms Zone occurs in the overlying siltstone. Pretectonic carbonate–chalcopyrite–pyrite and quartz–pyrite stringer veins occur in the footwall porphyritic dacite, south of Toms Zone. Strongly sheared dolomite–chalcopyrite–pyrrhotite veins directly underlie the Toms massive sulphide lens. The mineralized zones consist predominantly of pyrite, sphalerite and galena. Paragenetically early framboidal, dendritic and botryoidal pyrite aggregates and tabular pyrrhotite pseudomorphs of sulphate occur throughout the breccia and sandstone beds that host Main Zone, but are rarely preserved in the annealed massive sulphide in Toms Zone. Main and Toms zones are associated with a semi-conformable hydrothermal alteration envelope, characterized by texturally destructive chlorite-, dolomite- and quartz-rich assemblages. Dolomite, chlorite, quartz, calcite and sulphides have selectively replaced breccia and sandstone beds in the Main Zone host sequence, whereas the underlying porphyritic dacite is weakly sericite altered. Vuggy and botryoidal textures resulted from partial dissolution of the dolomite-altered sedimentary rocks and unimpeded growth of base metal sulphides, carbonate and quartz into open cavities. The intense chlorite-rich alteration assemblage, underlying Toms Zone, grades outward into a weak pervasive sericite–quartz assemblage with distance from the massive sulphide lens. Limestone clasts and hydrothermal dolomite at Lewis Ponds are enriched in light carbon and oxygen isotopes. The dolomite yielded ¹³C_VPDB values of –11 to +1 and ¹⁸O_VSMOW values of 6 to 16. Liquid–vapour fluid inclusions in the dolomite have low salinities (1.4–7.7 equiv. wt% NaCl) and homogenization temperatures (166–232°C for 1,000 m water depth). Dolomitization probably involved fluid mixing or fluid–rock interactions between evolved heated seawater and the limestone-bearing facies, prior to and during mineralization. ³⁴S_VCDT values range from 2.0 to 5.0 in the massive sulphide and 3.9 to 7.4 in the footwall carbonate–chalcopyrite–pyrite stringer veins, indicating that the hydrothermal fluid may have contained mamgatic sulphur and a component of partially reduced seawater. The sulphide mineral assemblages at Lewis Ponds are consistent with moderate to strongly reduced conditions during diagenesis and mineralization. Low temperature dolomitization of limestone-bearing facies in the Main Zone host sequence created secondary porosity and provided a reactive host for fluid-rock interactions. Main Zone formed by lateral fluid flow and sub-seafloor replacement of the poorly sorted breccia and sandstone beds. Base metal sulphide deposition probably resulted from dissolution of dolomite, fluid mixing and increased fluid pH. Pyrite, sphalerite and galena precipitated from a relatively low temperature, 150–250°C hydrothermal fluid. In contrast, Toms Zone was emplaced into fine-grained sediment at or near the seafloor, above a zone of focused up-flowing hydrothermal fluids. Copper-rich assemblages were deposited in the Toms Zone footwall and massive sulphide lenses in Main and Toms zones as the hydrothermal system intensified. During the D₁ deformation, fracture-controlled fluids within the Lewis Ponds fault zone and adjacent footwall volcanic succession remobilized sulphides into syntectonic quartz veins. Lewis Ponds is a rare example of a synvolcanic sub-seafloor hydrothermal system developed within fossiliferous limestone-bearing facies. The close spatial association between limestone, hydrothermal dolomite, massive sulphide and dacite provides a basis for new exploration targets elsewhere in New South Wales.Editorial handling: D. Lentz  相似文献   

The junction of the eastern Central Asian Fold Belt and the Siberian Platform: deep structure and Mesozoic tectonics and geodynamics     

B.F. Shevchenko  M.V. Goroshko  A.N. Didenko  V.A. Gur'yanov  V.S. Starosel'tsev  A.S. Sal'nikov 《Russian Geology and Geophysics》2011,52(12):1672-1679

The tectonic structure of the junction of the eastern Central Asian Fold Belt and the Siberian Platform, along with the deep structure of the Earth's crust and lithosphere in this region, has been described on the basis of new geological and geophysical data (seismic, geoelectric, and space-structural studies as well as new-generation geological maps), combined with new interpretation techniques (processing of the previous data by special software). The data suggest the existence of oblique collision during the convergence of the tectonic plates and, correspondingly, tectonic units composing these plates, when the Mongol–Okhotsk paleobasin closed. Such a scenario within the Aldan–Stanovoi Shield is evidenced by areas of syn- and postcollisional magmatism, with their deep-level and geochemical characteristics, and by the presence of a Late Mesozoic fold–thrust zone. Deep “traces” of these tectonomagmatic events, detected in the course of geological and geophysical modeling, are manifested in inclined deep boundaries between the crustal and lithospheric blocks. On the Earth's surface, they correspond to large fault systems: the Dzheltulak, North and South Tukuringra, Gulyui, and Stanovoi. It has been found that the influence of collision decreases northward with distance from the junction of the eastern Central Asian Fold Belt and the Siberian Platform (Dzheltulak and North Tukuringra transcrustal faults).  相似文献