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1.
分步加热实验结果表明大别山超高压岩流体包裹体成分 (不计入水 )主要是CO2 ,其次为CO及少量的N2 和CH4;变质高峰期流体CO2 碳同位素值 ( - 2 5‰～- 30‰ )与地幔流体相差较大 ,说明其是原岩自身含碳物质在高温高压之下演化的结果 ,反映了超高压变质岩石虽然可能俯冲到地幔深度 ,但并未受到地幔流体的大规模作用 ,岩石中的流体系统是活动有限的、较为封闭的体系 .这可能与地壳岩石快速插入地幔、并又迅速折返至地表的动力学机制有关  相似文献   

2.
徐常芳 《地震学报》1996,18(3):352-357
探讨了地壳内高导层的碳膜成因说和卤水成因说，中下地壳存在卤水，卤水使碳膜连通，增大了岩石的电导率，因而认为卤水是形成壳内高导层的关键物质，进而探讨了不同浓度的卤水在高温高压下的物态及其电导率变化规律，以及壳内高导层中卤水的封存机制．壳内高导层是壳-幔流体演化形成的.   相似文献   

3.
鲜水河断裂带南段深部电性结构特征研究   总被引：6，自引：1，他引：5       下载免费PDF全文
通过对新都桥一小金剖面的大地电磁测深及重磁实测资料研究,结合区域地质资料,对鲜水河断裂带南段及邻区深部构造、壳内高导层、电性结构与历史地震的关系进行了研究.结果表明:(1)鲜水河断裂带深浅表现出不同特征,浅部是以地壳脆性-剪切带为主的断裂系统,深部是以走滑型-壳幔韧性剪切带为主的断裂系统,断裂呈花状形态,深部到达上地幔;(2)在丹巴构造带及鲜水河断裂带的中下地壳,广泛发育壳内高导层,其分布具有不均匀性,且与断裂带构造活动有关;(3)在鲜水河断裂带的走滑剪切作用下,上地壳物质发生原地重熔产生花岗岩浆是折多山花岗岩形成的主要机制;(4)鲜水河断裂带地震发生机理与塑性软弱层密切相关,受塑性软弱层拖拽作用,应力区集中在高阻体脆性介质内部靠近断层一侧,使得岩石破碎而发生地震.  相似文献   

4.
松辽盆地深部地质特征及其盆地动力学演化   总被引：19，自引：0，他引：19       下载免费PDF全文
对松辽盆地深反射地震资料的分析表明 ,该盆地地壳不仅具有层圈结构 ,而且具有明显的块断构造 ,这些块断的边界是深部热流体的网络通道。以深反射地震资料研究为基础 ,结合区域地震层析成像、火山岩地球化学等对壳幔相互作用的研究成果 ,通过地壳层圈与块断结构、构造变形史以及盆地构造与深部构造之间的关系研究 ,认为松辽盆地的形成过程是 :库拉 -太平洋板块向欧亚大陆之下俯冲作用导致的地幔隆起促使地壳拆沉减薄、地壳“三明治”结构形成 ,同时导致上地壳伸展沉降及其后期的热沉降。正因如此 ,盆地整体凹陷与地幔凸起成镜像关系 ,而断陷与拆离带凸起成偏镜像关系。强烈的壳幔作用是形成松辽盆地大规模沉降的动力学基础 ,也是盆地油气 (包括无机物质 )富集的重要原因  相似文献   

5.
本文以中俄、俄日学者合作所得到的地球物理资料为主,结合其它相关地质-地球物理数据,组构了俄罗斯贝加尔湖-日本仙台(BS)4000 km长断面,用于区域性大尺度地研究东北亚洲地壳结构和一系列地质构造问题.研究BS断面地震波速结果表明:(1)西伯利亚板块和黑龙江板块地壳结构变化较大,并可分为上、中、下部地壳,欧亚板块东部陆缘带地壳结构较简单,基本两分.贝加尔裂谷带下部地壳厚度比松辽盆地的薄约7 km,而上部地壳则相反,前者的比后者的厚约9 km.两个裂谷带在Moho界面之下的波速分布差异也较大.(2)结合前人认识,综合分析认为,贝加尔裂谷带属主动式裂谷,松辽盆地属于混合型裂谷.贝加尔裂谷形成动力主要来自地球构造圈B″层物质上涌所形成的地幔热柱的垂向作用,由BLV带佐证,松辽盆地形成动力主要来自太平洋板块斜向俯冲的中远程效应.(3)日本国所位于的西太平洋岛弧带是多地震带,除了太平洋板块俯冲产生的浅部效应、地壳中断裂与流体的直接作用等因素,本文指出仙台等速块的物性条件是岛弧带的主要不稳定因素.同时指出需要关注日本东海岸深约30~40 km的大级次地震的发生.  相似文献   

6.
山东夏甸金矿床成因一直有变质热液、岩浆热液和天水之争,经研究表明:尚有幔源流体加入成矿,其主要判别标志有:(ⅰ)深大断裂标志;(ⅱ)基性脉岩与矿脉交切和相伴标志;(ⅲ)稳定同位素地球化学标志;(ⅳ)流体包裹体地球化学标志;(V)幔源流体多层循环沟通标志,针对幔源流体总体循环系统特征与岩浆热液和天水的有机联系,将含矿流体划分3个子循环系统:(ⅰ)地幔富C,H,O,CO_2流体循环子系统;(ⅱ)中-下部地壳富硅流体循环子系统;(ⅲ)浅-表部富硫流体循环子系统.各自成矿功能主要受制于构造动力背景.  相似文献   

7.
福州盆地及其周围地区地壳深部结构与构造的初步研究   总被引：20，自引：4，他引：20  
1986-1988年,福建省地震局在福州盆地及其周围地区完成了五条地震测深剖面:宁德-永春剖面;洪懒-宁德剖面;莲峰-福州（尚干）剖面;南平-永泰-平潭非纵剖面;并在宁德-古田-嵩口首次试验扇形剖面观测系统,结果表明,扇形剖面对确定断裂是有效的. 根据对地震波走时的正、反演计算,用理论地震图和射线追踪方法进一步修改和完善,得到了福州盆地及其周围地区地壳深部为高、低速相间的速度分布特征.地壳介质速度为6.40km/s,在中地壳普遍发育一层速度为5.80-5.90 km/s、厚度约5.0 km的低速层.Moho面深度30-33 km,福州盆地为一Moho面隆起区,隆起幅度达3.0 km.北西向断裂发育,其中,闽江断裂在纵剖面和扇形剖面均有明显的反映,并切割到Moho面2.0-3.0 km. 反射波谱频方法计算得到福州盆地地壳Q值仅120-150,比邻近地区明显偏低,中地壳低速层Q值为40-80,是一典型的低速-高导-低Q（高衰减）结构层,此层上界面埋深14-15 km,与居里面埋深较一致.这些结果为福州地区的地热资源远景预测和开发提供了地壳深部结构和某些地球物理场背景.  相似文献   

8.
中地壳的水和水岩相互作用实验及其地球物理涵义   总被引：2，自引：0，他引：2       下载免费PDF全文
本文重点报道了高温高压下流体与流体-岩石相互作用实验结果,提供了中地壳条件下流体性质和水岩反应速率数据.这些数据有助于理解中地壳的一些地球物理现象.作者进行了25℃~435℃和22~39 MPa条件下水-岩相互作用反应动力学实验.同时,研究水在近临界区至超临界区的性质.一般地说,中地壳大致位于10(15)至25 km的深度范围.各地的地壳厚度不同,但是中地壳高导-低速层的深度范围十分相似.中地壳的顶界温度处于300℃,底界大致为450℃范围,压力高达200 MPa以上.流体-岩石相互作用实验表明:硅酸盐矿物和岩石的硅最大溶解速率出现在300℃~400℃.此时,硅酸盐矿物格架解体.通常,地壳里普遍存在水、流体.地壳构造活动导致断裂空隙、减压、流体流动.这时,有可能导致中地壳处于300℃~450℃流体的压力减低,由超临界区进入临界态、亚临界态.这会引发强烈流动的水与岩石相互作用.溶解反应导致岩层的硅淋失,硅的强烈淋失又会导致硅酸盐矿物格架解体,岩石崩塌.同时,进一步促进流体的流动.实验表明300℃~400℃下的强烈水岩相互作用促进了岩石破坏,并有可能影响岩层的地球物理性质,如高导层出现.另外,实验和理论研究表明处于300℃~400℃流体具有高电导率性质.这些水岩相互作用会使中地壳出现高导-低速层.  相似文献   

9.
山东夏甸金矿床成因一直有变质热液、岩浆热液和天水之争。经研究表明:尚有幔源流体加入成矿,其主要判别标志有:(ⅰ)深大断裂标志;(ⅱ)基性脉岩与矿脉交切和相伴标志;(ⅲ)稳定同位素地球化学标志;(ⅳ)流体包裹体地球化学标志;(ⅴ)幔源流体多层循环沟通标志。针对幔源流体总体循环系统特征与岩浆热液和天水的有机联系,将含矿流体划分3个子循环系统:(ⅰ)地幔富C,H,O,CO_2流体循环子系统;(ⅱ)中-下部地壳富硅流体循环子系统;(ⅲ)浅-表部富硫流体循环子系统。各自成矿功能主要受制于构造动力背景。  相似文献   

10.
松辽盆地非生物成因气的成藏特征   总被引：38，自引：1，他引：38  
松辽盆地所处地壳块段的纵向结构,依密度大小可分为上、中、下地壳.在上、中地壳间有一厚的3km的低密度层段.它可能是上地幔熔融物质析离出来的“流体相”在地壳中聚集的岩浆房.它通过地壳断裂和天然地震向松辽裂谷盆地供给非生物成因天然气和其它气态物质及热液流体,这是松辽盆地形成非生物成因气藏的根本条件.在上地壳(或称盆地基底)断裂两侧有基底及以上层位的构造圈闭;有不整合面或横向延展广阔的含联通孔隙的砂层做为运移通道及天然气储集层;临近气层有泥岩做为封闭的盖层,这些条件的适当配置是非生物成因气成藏的基本特征.  相似文献   

11.
Water quality, physical habitat, and fisheries at sixteen reaches in the Neversink River Basin were studied during 1991-95 to identify the effects of acidic precipitation on stream-water chemistry and on selected fish-species populations, and to test the hypothesis that the degree of stream acidification affected the spatial distribution of each fish-species population. Most sites on the East Branch Neversink were strongly to severely acidified, whereas most sites on the West Branch were minimally to moderately acidified. Mean density of fish populations ranged from 0 to 2.15 fish/m2; biomass ranged from 0 to 17.5 g/m2. Where brook trout were present, their population density ranged from 0.04 to 1.09 fish/m2, biomass ranged from 0.76 to 12.2 g/m2, and condition (K) ranged from 0.94 to 1.07. Regression analyses revealed strong relations (r2 - 0.41 to 0.99; p h 0.05) between characteristics of the two most common species (brook trout and slimy sculpin) populations and mean concentrations of inorganic monomeric aluminum (Alim), pH, Si, K+, NO3-, NH4+, DOC, Ca2+, and Na+; acid neutralizing capacity (ANC); and water temperature. Stream acidification may have adversely affected fish populations at most East Branch sites, but in other parts of the Neversink River Basin these effects were masked or mitigated by other physical habitat, geochemical, and biological factors.  相似文献   

12.
The Cheb Basin, located in the western Eger (Ohře) Rift, is part of the European Cenozoic Rift system. Although presently non-volcanic, it is the most active area within the European Rift with signs of recent geodynamic activity like emanations of mantle derived CO2, and the repeated occurrence of swarm earthquakes, which are common features in active volcanic regions. It is assumed that the fluids, uprising in permeable channels, play a key role for the genesis of these earthquake swarms.  相似文献   

13.
Field observations coupled with experimental results show that CO2 can be produced by mechanical energy applied to carbonate rocks becoming an unexpected additional gas source besides that degassed from the mantle or produced by thermometamorphism. The evidence that a large amount of carbon dioxide associated with radiogenic-type helium (R/Ra as low as 0.01–0.08) is released through continental areas, denotes the absence of a contribution from the mantle or from mantle-derived fluids. Data collected during the seismic crisis which struck the Central Apennines in 1997–98 have shown an enhanced CO2 flux not associated with the presence of mantle or thermometamorphic-derived fluids. On the other hand, new experimental results highlight the possibility of producing CO2 by mechanical energy that acts on the calcite crystalline lattice. While the CO2 released over the geothermal areas (e.g., Larderello Geothermal Field) is obviously derived by mantle-derived activities, this is not the case of the huge amount of CO2 released over the seismically active areas where the presence mantle-derived products is ruled out. We propose that mechanical energy, e.g., released during seismic events, microseismicity or creeping processes is a possible additional energy source able to produce CO2 and thus could explain the presence of CO2 degassing over tectonic areas where the influence of the mantle is low.  相似文献   

14.
《Journal of Geodynamics》2008,45(3-5):149-159
Locations of the Eger Rift, Cheb Basin, Quaternary volcanoes, crustal earthquake swarms and exhalation centers of CO2 and 3He of mantle origin correlate with the tectonic fabric of the mantle lithosphere modelled from seismic anisotropy. We suggest that positions of the seismic and volcanic phenomena, as well as of the Cenozoic sedimentary basins, correlate with a “triple junction” of three mantle lithospheres distinguished by different orientations of their tectonic fabric consistent within each unit. The three mantle domains most probably belong to the originally separated microcontinents – the Saxothuringian, Teplá-Barrandian and Moldanubian – assembled during the Variscan orogeny. Cenozoic extension reactivated the junction and locally thinned the crust and mantle lithosphere. The rigid part of the crust, characterized by the presence of earthquake foci, decoupled near the junction from the mantle probably during the Variscan. The boundaries (transitions) of three mantle domains provided open pathways for Quaternary volcanism and the ascent of 3He- and CO2-rich fluids released from the asthenosphere. The deepest earthquakes, interpreted as an upper limit of the brittle–ductile transition in the crust, are shallower above the junction of the mantle blocks (at about 12 km) than above the more stable Saxothuringian mantle lithosphere (at about 20 km), probably due to a higher heat flow and presence of fluids.  相似文献   

15.
Locations of the Eger Rift, Cheb Basin, Quaternary volcanoes, crustal earthquake swarms and exhalation centers of CO2 and 3He of mantle origin correlate with the tectonic fabric of the mantle lithosphere modelled from seismic anisotropy. We suggest that positions of the seismic and volcanic phenomena, as well as of the Cenozoic sedimentary basins, correlate with a “triple junction” of three mantle lithospheres distinguished by different orientations of their tectonic fabric consistent within each unit. The three mantle domains most probably belong to the originally separated microcontinents – the Saxothuringian, Teplá-Barrandian and Moldanubian – assembled during the Variscan orogeny. Cenozoic extension reactivated the junction and locally thinned the crust and mantle lithosphere. The rigid part of the crust, characterized by the presence of earthquake foci, decoupled near the junction from the mantle probably during the Variscan. The boundaries (transitions) of three mantle domains provided open pathways for Quaternary volcanism and the ascent of 3He- and CO2-rich fluids released from the asthenosphere. The deepest earthquakes, interpreted as an upper limit of the brittle–ductile transition in the crust, are shallower above the junction of the mantle blocks (at about 12 km) than above the more stable Saxothuringian mantle lithosphere (at about 20 km), probably due to a higher heat flow and presence of fluids.  相似文献   

16.
Chemical heterogeneities of pumice clasts in an ash-flow sheet can be used to determine processes that occur in the magma chamber because they represent samples of magma that were erupted at the same time. The dominant ash-flow sheet in the Tiribí Tuff contains pumice clasts that range in composition from 55.1 to 69.2 wt% SiO2. It covers about 820 km2 and has a volume of about 25 km3 dense-rock equivalent (DRE). Based on pumice clast compositions, the sheet can be divided into three distinct chemical groupings: a low-silica group (55.1-65.6 wt% SiO2), a silicic group (66.2-69.2 wt% SiO2), and a mingled group (58.6-67.7 wt% SiO2; all compositions calculated 100% anhydrous). Major and trace element modeling indicates that the low-silica magma represents a mantle melt that has undergone fractional crystallization, creating a continuous range of silica content from 55.1-65.6 wt% SiO2. Eu/Eu*, MREE, and HREE differences between the two groups are not consistent with crystal fractionation of the low-silica magma to produce the silicic magma. The low-silica group and the silicic group represent two distinct magmas, which did not evolve in the same magma chamber. We suggest that the silicic melts resulted from partial melting of relatively hot, evolved calc-alkaline rocks that were previously emplaced and ponded at the base of an over-thickened basaltic crust. The mingled group represents mingling of the two magmas shortly before eruption. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00445-001-0188-8.  相似文献   

17.
A wide range of stoichiometries has been previously proposed for soluble iron sulfide species and there is no general agreement on their importance in natural waters. The solubility of Fe(II) in 0.1 M NaClO4 equilibrated at 20 - 0.1°C with various partial pressures of H2S (0.1, 0.001, 0.0001, 0.00001 MPa) was measured in the pH range 3.1-7.9. Equilibrium was established within 1-6 h when amorphous FeS was the solid phase. The results could all be fitted using values for the solubility product constant (I = 0) of p*Ks = 3.00 - 0.12 and of the stability constant for a soluble Fe(HS) 2 species (I = 0) of p#2 = -6.45 - 0.12 where *Ks = aFe2+ · aHS-/aH+ and #2 = aFe(HS) 2/aFe2+ · (aHS-)2. Any soluble species of the form Fex (HS) 2x where x = &gif1; would fit the data equally well. Measurements at different partial pressures are inconsistent with labile species of the form FexSx. There was no evidence for a Fe(HS) + species. When a solution is saturated with respect to amorphous FeS, Fe(HS) 2 will only be a significant proportion of Fe(II) when S(-II) is higher than 0.2mmoll-1. The constants for Fe(HS) 2 or Fex (HS) 2x (x S 2) are consistent with all freshwater data where constant values of measured ion activity products provide no evidence for soluble complex formation. For marine waters with high sulfide concentrations (S 6mmol l-1), measured concentrations of Fe(II) are consistent with there being negligible soluble iron sulfide. The data are better fitted if the dissolved species are polymeric as predicted concentrations of the monomer Fe(HS) 2 are significant. These findings suggest that rather than the dissolved species being Fe(HS) 2, it is probably polymeric, that is Fex (HS) 2x (x S 2).  相似文献   

18.
Our objective is to look for deep paths of Cenozoic volcanism and migration routes of active mantle volatiles through the lithosphere of the western Bohemian Massif. We show that the rejuvenated junction of three mantle domains, delimited by different orientation of seismic anisotropy and belonging to originally separated microplates — the Saxothuringian (ST), Moldanubian (MD) and Teplá-Barrandian (TB) — can provide the easiest upward routes of fluids through the deep lithosphere. Geographic distribution of mantle-fluid escapes at the surface suggests fluid migration through the ductile lower crust and through partly open faults in the rigid upper crust, which is locally detached and shifted from its lower part and from the mantle lithosphere. Present-day escapes of mantle-derived helium and CO2 concentrate mainly in two tectonically different crust edifices — in the Cheb Basin (CHB) and in an allochtonous block called the Mariánské Lázně Complex (MLC). Crystalline basement of the CHB developed above the Variscan ‘triple junction’ of the mantle lithosphere domains. The basement was extended during the Cenozoic and dissected by systems of faults into small partly sunken blocks. Thanks to buoyancy the mantle fluids migrate upwards along the lithosphere junction into the faulted basement of the CHB. The highest CO2 flow and the highest 3He/4He ratios are observed at intersections of major normal faults and along the southern boundary of the Smrčiny (Fichtelgebirge) granite Pluton. The fluid escapes are separated from the earthquake swarm epicentres. Routes of the fluids to the MLC are longer and more complicated. Surface escapes tap the mantle fluids mainly from the Mariánské Lázně Fault (MLF) and from the tectonic boundaries along which the MLC block of the TB lower crust was thrust over the ST complexes. Hypocentres of earthquake swarms of the two major focal areas at Novy Kostel and Lazy, located mainly at depths of 6–13 km, reside either in granite or in underlying gneiss, while the escapes of mantle fluids follow major faults or boundaries of crystalline units outside the Smrčiny and Karlovy Vary granite Plutons. We suggest that primarily those parts of faults in the upper crust, which is strengthened by granite magmatism and rigid enough to selectively accumulate stresses, are seismoactive. On the other hand, other parts of the faults tapping ascending mantle volatiles are ‘lubricated’ by the fluids and secondary mineralogical changes, and thus they cannot accumulate sufficient stresses to be released by earthquakes. A comparison of the most probable paths of the mantle fluids with the space-time distribution of the Novy Kostel hypocentres does not seem to support the model of the earthquake swarms triggered by pressurized fluids of mantle origin.  相似文献   

19.
Reservoir-forming features of abiotic origin gas in Songliao Basin   总被引：4，自引：0，他引：4  
The vertical structure of the crustal block of the Songliao Basin can be divided into upper, middle and low Earth’s crust according to density. There is an about 3-km-thick low density interval between the upper crust and the middle crust. This interval may be a magma chamber accumulated in crust by “fluid phase” which is precipitated and separated from upper mantle meltmass. The abiogenetic natural gas, other gaseous mass and hydrothermal fluids are provided to the Songliao rifted basin through crustal faults and natural earthquakes. This is a basic condition to form an abiogenetic gas reservoir in the Songliao Basin. On both flanks of the upper crust (or named basin basement) fault there are structural traps in and above the basement and unconformity surface or lateral extended sand, which contains communicated pores, as migration pathway and natural gas reservoir; up to gas reservoirs there is shale as enclosed cap rock, and the suitable arrangement of these conditions is the basic features of abiogenetic gas reservoir. Project supported by the National Natural Sc~ence Foundation of China.  相似文献   

20.
-- We propose a thermal-mechanical model of shear deformation of a viscoelastic material to describe the temperature-dependence of friction law. We consider shear deformation of one-dimensional layer composed of a Maxwell linear viscoelastic material under a constant velocity V and temperature Tw at the boundary. The strain rate due to viscous deformation depends both on temperature and shear stress. The temperature inside the layer changes owing to frictional heating and conductive cooling. Steady-state calculations show that the sign of d†ss/dV, where †ss is steady-state stress, changes from positive to negative as V increases, and that the threshold velocity above which the sign of d†ss/dV is negative increases with increasing Tw. These results are in accordance with the conjecture that the downdip limit of seismogenic zones is marked by the transition in the sign of d†ss/dV due to temperature rise with depth. We also find that the response of steady state to a step change in V is quite similar to the response of frictional slip with constitutive laws which employ state variables. These findings suggest that by further improving the present model a model of constitutive relations along faults or plate boundaries can be developed which contains temperature-dependence in a physically-sound manner.  相似文献   

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