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1.
Shaohua Zhou 《地学学报》1996,8(6):514-524
An analytical solution has been derived for the steady-state geotherm of the continental lithosphere, using an empirical thermal conductivity model that incorporates the experimentally observed temperature and pressure effect. Based on recent global compilations of crustal thickness and heat flow data, a standard continental lithosphere is re-defined by a global mean model with total crustal thickness of 40 km and surface heat flow of 55 mWm-2 (within which 28 mWm-2 is assumed to be derived from deep mantle source). The thickness of the continental lithosphere (≅125 km), consistent with previous models, is given by the depth at which the geotherm intersects the potential asthenosphere temperature of 1280°C. It is shown that the new steady-state geotherm is much hotter than that based on the previously adopted model where material thermal conductivity is assumed to be constant (≅3.14 W/m/k) throughout the lithosphere. The consequence of this re-evaluation of pre-extension thermal structure in the lithosphere is that the minimum stretching factor required to cause the onset of dry mantle partial melting can be 15–20% lower than the previous estimate. Also, if minor amounts of water or other volatile element or dry basalt are present in the upper mantle, melting of the subcontirfental mantle is very likely to occur for any geotherms constructed using surface heat flows > 30 mWm-2 . 相似文献
2.
The boundary between lithosphere and asthenosphere essentially represents a thermal boundary (the solidus).Temperature variation across this boundary can lead to the change of lithosphere thickness.In the case of elevated temperatures in a lithospheric layer above 1 200℃,partial melting will begin and the result of that is a thinned lithosphere.The other mechanism that can also thin lithosphere is extension. 相似文献
3.
The thermal structure and thickness of continental roots 总被引：19，自引：0，他引：19
We compare heat flow data from the Precambrian shields in North America and in South Africa. We also review data available in other less well-sampled Shield regions. Variations in crustal heat production account for most of the variability of the heat flow. Because of this variability, it is difficult to define a single average crustal model representative of a whole tectonic province. The average heat flow values of different Archean provinces in Canada, South Africa, Australia and India differ by significant amounts. This is also true for Proterozoic provinces. For example, the heat flow is significantly higher in the Proterozoic Namaqua–Natal Belt of South Africa than in the Grenville Province of the Canadian Shield (61 vs. 41 mW m−2 on average). These observations indicate that it is not possible to define single value of the average heat flow for all provinces of the same crustal age. Large amplitude short wavelength variations of the heat flow suggest that most of the difference between Proterozoic and Archean heat flow is of crustal origin. In eastern Canada, there is no good correlation between the local values of heat flow and heat production. In the Archean, Proterozoic and Paleozoic provinces of eastern Canada, heat flow values through rocks with the same heat production are not significantly different. There is therefore no evidence for variations of the mantle heat flow beneath these different provinces. After removing the local crustal heat production from the surface heat flow, the mantle (Moho) heat flow was estimated to be between 10–15 mW m−2 in the Archean, Proterozoic and Paleozoic provinces of eastern Canada. Estimates of the mantle heat flow in the Kaapvaal craton of South Africa may be slightly higher (≈17 mW m−2). Large-scale variations of bulk crustal heat production are well-documented in Canada and imply significant differences of deep lithospheric thermal structure. In thick lithosphere, surficial heat flow measurements record a time average of heat production in the lithospheric mantle and are not in equilibrium with the instantaneous heat production. The low mantle heat flow and current estimates of heat production in the lithospheric mantle do not support a mechanical (conductive) lithosphere thinner than 200 km and thicker than 330 km. Temperature anomalies with surrounding oceanic mantle extend to the convective boundary layer below the conductive layer, and hence to depths greater than these estimates. Mechanical and thermal stability of the lithosphere require the mantle part of the lithosphere to be chemically buoyant and depleted in radiogenic elements. Both characteristics are achieved simultaneously by partial melting and melt extraction. 相似文献
4.
依据236口井共2 706组的静温数据以及25口井的系统测温数据,分析计算了渤海盆地地温梯度及大地热流;建立地壳分层结构模型,利用回剥法计算现今地幔热流、深部温度以及岩石圈厚度;在此基础上,利用地球动力学方法恢复本区热流演化史。结果表明：渤海盆地背景地温梯度为322 ℃/km,热流值为648 mW/m2;盆地现今热岩石圈厚度在61~69 km之间,地幔热流占地表热流的比例在60%左右,属于“热幔冷壳”型岩石圈热结构,盆地地壳底部或莫霍面温度变动在548~749 ℃之间;热流演化的特征与盆地的构造演化背景吻合,新生代以来盆地经历了3期岩石圈减薄并加热的过程,在东营组沉积末期热流达到最高(70~83 mW/m2）,这期间盆地内产出多期碱性玄武岩,表明盆地经历了波及地幔的裂谷过程,随后进入热沉降期,热流逐渐降低,盆地向坳陷型转变。 相似文献
5.
Parameterization of melting phenomena in the upper mantle hasprimarily focused on two basic themes, namely the physical andchemical processes that govern partial melting. Parameterizationof physical processes mainly refers to establishing relationshipsbetween parameters such as the temperature, pressure, matrixand melt flow geometry, lithospheric stretching, and volumeof magma. By contrast, parameterization of chemical processeslargely implies unravelling the relationships between type anddegree of melting, and source and melt composition. Few attemptshave been made, however, to interrelate the two processes. Thepresent work is an effort to provide a link between physicaland chemical parameters associated with mantle melting and toallow in-depth modelling of partial melting processes in upwellingasthenosphere in a rigorous yet simplified manner. Several correlationsamong the most important physical parameters (e.g., equilibrationand extrusion temperature and pressure of magma, melt fractionand thickness, stretching factor, etc.) are explored. On thisbasis, a model for the compositional stratification of the lithosphereis proposed, and its bearing on the nature of intra-oceanicarc magmatism is emphasized. Trends of melting residues in termsof modal olivine and clinopyroxene are calculated for a widerange of possible potential temperatures that may be appliedto xenolith or abyssal peridotite suites to constrain furthertheir original depth of upwelling. Dry solidus equations fordepleted peridotite compositions are also derived that may beused to infer the effects of volatiles on the melting of refractorysupra-subduction zone mantle. The sensitivity of certain elementsto temperature variations during melting in a column of ascendingmantle is highlighted using Ni as an example, and the dangersof using single-value distribution coefficients to predict concentrationsof transition metals in magmas are emphasized. MORB-normalizedmulti-element profiles calculated using a variety of sources,mantle potential temperatures, and stretching factors are presented,and the differences between instantaneous and pooled melts arediscussed. A technique to calculate mineral proportions duringtransformation of garnet lherzolite to spinel lherzolite, togetherwith estimates of the modal composition of fertile spinel andgarnet lherzolite are included. Selected trace-element abundancesin various sources [bulk silicate Earth, depleted MORB (mid-oceanridge basalt) mantle, N-MORB) and distribution coefficientsfor common rock-forming minerals are also tabulated. 相似文献
6.
在大地热流密度分布的基础上,本文基于二维稳态热传导方程,根据研究区热导率、生热率等热物理性质参数,对横穿川东北地区、秭归盆地、黄陵穹窿和江汉盆地等几个构造单元的奉节（FJ）-观音垱（GYD）地学剖面进行了温度场数值模拟研究,获得了其深部热结构认识。模拟结果显示,地幔热流自西向东逐渐升高,变化范围约为25.3～34.7 mW/m2。莫霍面温度大约在380 ℃～450 ℃之间变化。热岩石圈厚度自西向东先稍微增厚,后逐渐变薄,变化范围约为115～171 km。江汉盆地中新生代的伸展作用使其地幔热流稍有升高,“热”岩石圈厚度相对较薄（约116 km）,而川东北地区则受到早期的挤压和晚期的抬升剥蚀作用,地幔热流相对较低,其深部“热”岩石圈厚度也相对较厚（约168 km）。 相似文献
7.
用玄武岩组成反演中-新生代华北岩石圈的演化 总被引：30，自引：3，他引：27
玄武岩的化学组成与地幔源区特征、部分熔融程度、地幔温度和岩石圈厚度等多个因素有关,因此可以用来反演深部地幔的演化。文中简要地阐述了用玄武岩组成获得岩石圈厚度及其变化的方法,并总结了有关华北中—新生代岩浆演化的两个最主要特征:(a)晚中生代岩浆活动经历了由早期的源自富集地幔的岩浆向后期亏损地幔起源岩浆的转变,而两个阶段为一岩浆间隙期(~10Ma)所分隔;(b)华北东、西部新生代玄武岩具有相反的碱性强度随时间的变化趋势。这些岩浆演化特征可以用岩石圈减薄过程中地幔地温梯度的逐渐升高、岩石圈地幔中富集组分在短时间内的不可再生以及岩石圈盖效应来解释。该认识为华北岩石圈减薄的时间尺度和机制以及减薄作用的时空不均一性提供了新的制约。 相似文献
8.
西北太平洋各边缘海及其相应俯冲系统受深部构造活动等地质条件的控制,热流变化较大。在收集整理该区域最新的热流数据基础上,重点探讨西北太平洋俯冲带热结构相关理论、边缘海大洋岩石圈热演化理论模型和局部高异常热流的影响因素,总结了西北太平洋边缘海热流所反映的地质意义。研究结果表明,在西北太平洋“沟-弧-海”体系中,从“沟”到“弧”再到“边缘海”,热流密度呈“低-高-较高”的变化趋势,弧后地区整体表现为“均一高热”特征;千岛海沟、日本海沟和琉球海沟热流密度值在30.0 mW/m2左右,而对应的岛弧值为其2~3倍。弧后热流大小受到汇聚型俯冲带热结构的影响,俯冲带脱水作用导致的弧后上地幔黏度变化,地震速度降低,岩石圈弹性厚度减薄,引起小尺度地幔对流,形成弧后“均一高热”的热状态。热流的时空分布与岩石圈年龄也有关,随着岩石圈年龄增大,地表热流密度值会随之降低,热流密度值大小和离散性与其形成时间大致呈负相关。鄂霍次克海形成时代(30~65 Ma)较早,其热流密度值(86.8 mW/m2)和离散性(标准差3.727)相对较低;冲绳海槽目前还处于扩张阶段,其热流密度值(139.0 mW/m2)和离散性(标准差7.001)较高。浅层的地下水循环、断裂活动,深层的地幔部分熔融岩浆活动、弧后小尺度地幔对流、俯冲带拐角流等对局部异常热流起到一定程度的控制作用。 相似文献
9.
碳酸岩的地质地球化学特征及其大地构造意义 总被引：20，自引：0，他引：20
从已知碳酸岩的地质产状、岩石学特征、Nd-Sr-Pb-O-C同位素及痕量元素地球化学特征数据,结合高温高压实验岩石学资料,论述了其地幔源区的物质成分、交代过程软流圈地幔部分熔融机制和碳酸岩岩浆的演化模型。碳酸岩既可以产生于拉张岩石圈构造背景,也能够产生于挤压而派生的引张岩石圈构造背景。前者以产于裂谷环境、与硅酸不饱和过碱性岩构成环状碳酸岩—碱性杂岩为特征,主要由起源于软流圈地幔的霞石质超基性—基性岩浆经液态不混溶作用而形成;后者产于碰撞造山过程中派生的引张岩石圈断裂带,以单一的透镜状、条带状和似层状碳酸岩体为标志,直接由导源岩石圈富集地幔的低程度部分熔融作用而产生的碳酸岩浆侵入或喷发所形成。 相似文献
10.
Nickolay L. Dobretsov Alexey A. Kirdyashkin Anatoliy G. Kirdyashkin Valery A. Vernikovsky Igor N. Gladkov 《Lithos》2008,100(1-4):66-92
Thermochemical plumes form at the base of the lower mantle as a consequence of heat flow from the outer core and the presence of local chemical doping that decreases the melting temperature. Theoretical and experimental modelling of thermochemical plumes show that the diameter of a plume conduit remains practically constant during plume ascent. However, when the top of a plume reaches a refractory layer, whose melting temperature is higher than the melt temperature in the plume conduit, a mushroom-shaped plume head develops. Main parameters (melt viscosity, ascent time, ascent velocity, temperature differences in the plume conduit, and thermal power) are presented for a thermochemical plume ascending from the core–mantle boundary. In addition, the following relationships are developed: the pressure distribution in the plume conduit during the ascent of a plume, conditions for eruption-conduit formation, the effect of the P–T conditions and controls on the shape and size of a plume top, heat transfer between a thermochemical plume and the lithosphere (when the plume reaches the bottom of a refractory layer in the lithosphere), and eruption volume versus the time interval t1 between plume formation and eruption. These relationships are used to determine thermal power and time t1 for the Tunguska syneclise and the Siberian traps as a whole.
The Siberian and other trap provinces are characterized by giant volumes of lavas and sills formed a very short time period. Data permit a model for superplumes with three stages of formation: early (variable picrites and alkali basalts), main (tholeiite plateau basalts), and final (ultrabasic and alkaline lavas and intrusions). These stages reflect the evolution of a superplume from the ascent of one or several independent plumes, through the formation of thick lenses of mantle melts underplating the lithosphere and, finally, intrusion and extrusion of differentiated mantle melts. Synchronous syenite–granite intrusions and bimodal volcanism abundant in the margins of the Siberian traps are the result of melting of the lower crust at depths of 65–70 km under the effect of plume melts. 相似文献
11.
Speculations on the nature and cause of mantle heterogeneity 总被引：8，自引：0，他引：8
Don L. Anderson 《Tectonophysics》2006,416(1-4):7
Hotspots and hotspot tracks are on, or start on, preexisting lithospheric features such as fracture zones, transform faults, continental sutures, ridges and former plate boundaries. Volcanism is often associated with these features and with regions of lithospheric extension, thinning, and preexisting thin spots. The lithosphere clearly controls the location of volcanism. The nature of the volcanism and the presence of ‘melting anomalies’ or ‘hotspots’, however, reflect the intrinsic chemical and lithologic heterogeneity of the upper mantle. Melting anomalies—shallow regions of ridges, volcanic chains, flood basalts, radial dike swarms—and continental breakup are frequently attributed to the impingement of deep mantle thermal plumes on the base of the lithosphere. The heat required for volcanism in the plume hypothesis is from the core. Alternatively, mantle fertility and melting point, ponding and focusing, and edge effects, i.e., plate tectonic and near-surface phenomena, may control the volumes and rates of magmatism. The heat required is from the mantle, mainly from internal heating and conduction into recycled fragments. The magnitude of magmatism appears to reflect the fertility, not the absolute temperature, of the asthenosphere. I attribute the chemical heterogeneity of the upper mantle to subduction of young plates, aseismic ridges and seamount chains, and to delamination of the lower continental crust. These heterogeneities eventually warm up past the melting point of eclogite and become buoyant low-velocity diapirs that undergo further adiabatic decompression melting as they encounter thin or spreading regions of the lithosphere. The heat required for the melting of cold subducted and delaminated material is extracted from the essentially infinite heat reservoir of the mantle, not the core. Melting in the upper mantle does not requires the instability of a deep thermal boundary layer or high absolute temperatures. Melts from recycled oceanic crust, and seamounts—and possibly even plateaus—pond beneath the lithosphere, particularly beneath basins and suture zones, with locally thin, weak or young lithosphere. The characteristic scale lengths—150 to 600 km—of variations in bathymetry and magma chemistry, and the variable productivity of volcanic chains, may reflect compositional heterogeneity of the asthenosphere, not the scales of mantle convection or the spacing of hot plumes. High-frequency seismic waves, scattering, coda studies and deep reflection profiles are needed to detect the kind of chemical heterogeneity and small-scale layering predicted from the recycling hypothesis. 相似文献
12.
大陆岩石圈有效弹性厚度与有关地球物理参数的关系--以泉州-黑水地学断面为例 总被引：1，自引：0，他引：1
大陆岩石圈有效弹性厚度(Te)是反映岩石圈综合强度的参数,它反映了岩石圈的整体特征。分析岩石圈有效样性厚度与反映深部地质特征的有关地球物理参数之间的关系,对研究控制Te的因素、各因素之间的关系以及探索大陆构造与大陆动力学等具有重要意义。泉州一黑水地学断面Te与地壳厚度、热岩石圈厚度、均衡重力异常、磁性构造层底面深度、上地幔低速层顶界面深度、上地幔低阻层顶面深度之间的关系研究表明：Te与大地热流关系密切的“热”地球物理参数磁性构造层底面深度、热岩石圈厚度相关性好;与地壳厚度有一定的相关性;上地幔低速层顶界面深度和上地幔低阻层顶面深度与大陆岩石圈Te相关性均较差。 相似文献
13.
Geotherm families in which surface heat flow is the principal independent variable have been constructed for continental and oceanic lithospheres. The continental model is characterized by geotherms in which surface heat flow is in equilibrium with heat flowing into the lithosphere at its base plus heat generated by radioactive decay within the lithosphere. The model accommodates the regional variation of the surface heat flow with proportional variations in the radioactivity of the surficial enriched zone and in the deeper heat flow. The proportionality is dictated by a new and general linear relationship between reduced heat flow and mean heat flow for a region (
), which enables both q* and the mean heat production of the enriched zone to be estimated from knowledge of the mean surface heat flow of a province. The oceanic model is characterized by the transient cooling of a semi-infinite medium with an initial temperature gradient and some near-surface radiogenic heat production. The model yields a heat flow in satisfactory agreement with observations in the oldest ocean basins. The depth at which both the oceanic and continental geotherms reach ~0.85 of the melting temperature is shown to be a consistent estimator of the depth to the top of the low-velocity channel, or the thickness of the high-velocity lid overlying the channel. We identify the lid as synonymous with the lithosphere, and produce a global map of lithospheric thickness based on the regional variation of surface heat flow. The lithosphere is less than 100 km thick over most of the globe, but thickens appreciably and becomes more viscous beneath the Precambrian shields and platforms, regions of low heat flow. These characteristics of shields are consistent with recently reported models of the driving mechanisms of the plate system, which require greater retarding forces beneath plates with large continental areas. 相似文献
14.
D.H. Chung 《Tectonophysics》1977,42(1):T35-T42
The seismologically observed Pn velocity anomalies in the conterminous United States are restricted to the lithosphere, but the observed teleseismic delay-time variations are due principally to the regional variations in the physical state (i.e., thickness of lowvelocity zone and/or percent melt, etc.) of the asthenosphere. The observed low Pn velocity has been attributed to partial melting in the upper mantle, but it is shown that the partial-melting model alone cannot explain the seismologically observed Pn velocities in such an anomalous region as the Basin and Range Province. The present structure of the Basin and Range Province is possibly a result of rifting in the western conterminous United States; under it there may lie a mixed structure of old crust and mantle materials. The low-velocity zone under the Basin and Range Province would then be caused by downward chemical transition from the sub-Moho pyrolitic mantle material into a plagioclase-rich ophiolitic (old oceanic crust and upper mantle) composition and associated meltingand then into a peridotitic composition at the bottom of the lowvelocity zone. This mixed material model, with partial melting, would explain the low Pn velocity and low seismic Q in the region, as well as other geophysical observations. 相似文献
15.
为了探讨东海陆架盆地西湖凹陷岩石圈热流变性质,本文以实测地温数据为依据,模拟西湖凹陷岩石圈热结构,在此基础上,应用流变学原理模拟确定西湖凹陷岩石圈流变性质。结果表明,西湖凹陷岩石圈为一个冷地壳-热地幔、强地壳-弱地幔的"奶油蛋糕"型岩石圈。西湖凹陷平均地表热流密度为71 m W/m~2,地幔热流密度为40~65 m W/m~2,对地表热流密度的贡献度达73%~79%,地表热流受地幔热流控制,莫霍面温度在700℃左右,热岩石圈平均厚度为66 km。西湖凹陷岩石圈流变分层明显,上、中地壳基本为脆性层,下地壳和岩石圈上地幔为韧性层,岩石圈总流变强度平均约为2.65′10~(12) N/m,其中地壳流变强度为2.12′10~(12) N/m,地幔流变强度为5.29′10~(11) N/m,有效弹性厚度为11.7~14.5 km,地壳的流变性质控制了岩石圈的流变行为。此外,西湖凹陷岩石圈总强度较低,在构造应力作用下易于变形,且存在壳幔解耦现象。西湖凹陷岩石圈热状态及流变性质决定了西湖凹陷东部地区主要以浅部地壳的断层滑动和地层破裂来调节深部的构造应力。 相似文献
16.
大陆伸展盆地岩浆与伸展作用的定量关系分析及其初步应用 总被引：3，自引：1，他引：3
通过对无水石榴石橄榄岩地幔的绝热减压部分熔融模型进行详细的数学推导,本文建立了准确的数学表达式以定量描述伸展因子、地幔部分熔融系数以及熔融体厚度之间的动力学关系。在详细的地球化学研究基础上,认为软流圈的部分熔融是济阳坳陷新生代火山岩的来源,并利用该模型对济阳坳陷新生代伸展裂陷阶段形成的熔融体厚度进行了预测,取得了与深部地球物理探测较为接近的结果。认为中下地壳中赋存的高导低速体是软流圈熔融体释放气体后聚集的结果,是盆地内分布的火山岩的直接源区。 相似文献
17.
甘肃龙首山岩带西井镁铁质岩体成因及其构造意义 总被引：2，自引：0，他引：2
西井岩体位于北祁连造山带以北,阿拉善地块西南缘的龙首山隆起带。以往的研究多以沿龙首山断裂分布的镁铁-超镁铁质岩带作为和金川岩体相关的岩浆事件进行,而本次选择西井镁铁质岩体进行了精确的地质年代学和地球化学研究,确定了西井岩体岩性主要为橄榄辉石岩和辉长岩,成岩时代为 (421.0±9.0) Ma,可以和北祁连高压变质带榴辉岩年龄相对应;εNd(t)为4.06~5.52,(87Sr/86Sr)i为0.704 548~0.707 575,具有地幔岩石圈特征;微量元素及其同位素计算表明西井岩体经历了约10%的下地壳物质混染。据此得出西井岩体及其龙首山岩带早志留世镁铁质侵入岩体成因模式为:祁连洋壳连续俯冲过程中洋壳与陆壳分离,热的软流圈物质持续冲击地幔岩石圈的底部;由于热传导效应,大地热流沿着地幔岩石圈上升,使得80 km深度的湿的橄榄岩层发生熔融,产生玄武质岩浆作用,玄武质岩浆上升过程中与下地壳物质发生约10%混染,形成西井岩体及其龙首山镁铁超镁铁质岩带。 相似文献
18.
ABSTRACT We propose a thermo-mechanical model and a new interpretation of heat flux data for the Ligurian basin that may be a key to understanding the evolution of the NW Mediterranean. The model incorporates the removal of a portion of mantle lithosphere to explain the heat-flux and subsidence anomaly of the eastern (Corsican) margin of the basin. This process is envisaged as a result of eastward asthenosphere flow induced by the Apennines subduction system. After a heating phase, time-dependent conductive cooling and re-thickening of the lithosphere result in re-equilibrium of the thermal gradient to its initial value. Such a rifting mode can account for the asymmetric heat-flux and subsidence pattern observed across the basin and the present-day lithospheric thickness. 相似文献
19.
中国大陆岩石圈厚度分布研究 总被引：11，自引：1，他引：10
利用不同物理性质所估计的岩石圈厚度可能具有不同的地球动力学意义。大陆岩石圈等效弹性厚度往往只与岩石圈内部的某些岩层相关,因此它可能不代表一般意义上的岩石圈厚度。地震学岩石圈厚度虽然有较高的精度,但依赖于人为地对岩石圈的定义;并且其具有的短时间尺度效应决定了它与长时间尺度的岩石圈概念不一致。热学岩石圈厚度体现了长时间尺度上的岩石圈热学作用,因此其厚度定义的标准是较合理的。地震-热学岩石圈厚度研究利用地震波速反演得到的温度数据按照热学岩石圈标准来对岩石圈厚度进行研究,具有地震学和热学岩石圈厚度两者的优点,是较合理的对岩石圈厚度的估计。中国大陆地震-热学岩石圈厚度分布有如下特点:(1)中国东部岩石圈较薄,厚度约100 km,其中包括中国东北、中朝克拉通、扬子克拉通东部和华南造山带;(2)青藏高原和塔里木克拉通以南地区的厚度变化较大,厚度约在160~220 km;(3)三大克拉通的岩石圈厚度有较大区别,扬子克拉通的核心最厚达约170 km,塔里木克拉通的核心厚度约140 km,中朝克拉通的厚度约100 km;(4)昆仑秦岭造山带的岩石圈上地幔内部较复杂,可能有大面积的部分熔融;(5)整个大陆岩石圈厚度分布并没有显示出与地壳年龄的线性相关关系,却表现出了与大地构造格局的直接关系。受板块碰撞强烈影响的地区,岩石圈较厚;受大洋俯冲带影响较强的地区,岩石圈较薄。 相似文献
20.
托云盆地新生代幔源岩浆源区起止深度的限定 总被引：2，自引：0，他引：2
在详细介绍了地幔熔融柱模型原理(Langmuir et al., 1992)的基础上,基于平衡熔融和分离熔融模型分别计算获得了上地幔橄榄岩源区在不同初始压力条件下发生绝热减压部分熔融时熔体相中FeO-MgO和FeO-Na2O成分的演化轨迹。依据深源岩石包体与托云玄武岩之间的寄主关系将本次研究的16件托云火山岩样品划分成Group-1(深源岩石包体寄主岩)和Group-2(非寄主岩)两群,将收集前人的40件样品依据是否测试获得FeO的质量百分含量划分成Group-3群(具有实测的FeO质量百分含量)和Group-4群(无实测FeO质量百分含量数据)。分别对以上四群样品运用地幔熔融柱模型进行反演获得上地幔部分熔融源区的起止深度范围：Group-1和Group-3样品具有相同的初始熔融深度113.2km (34.1kbar),但它们的部分熔融作用终止深度分别为110.1km (33.1kbar) 和88.4km (26.2kbar);Group-2样品数据所反演的岩浆起源的初始深度和终止深度分别为111.6km (33.6kbar)和84.3.1km(24.9kbar);Group-4样品反演所获得的岩浆源区的起止深度分别为121.7km(36.8kbar)和106.0km(31.8kbar)。依据实测FeO百分含量的样品群反演的结果,将托云火山岩部分熔融源区的深度限定在113.2 km至84.3km,即48.1Ma前托云盆地所处的岩石圈厚度为84.3km,对梁涛(2005)运用熔融柱模型反演的托云盆地岩石圈深度进行了修正。此外,由地幔熔融柱模型反演获得的托云火山岩部分熔融源区熔体的温度压力条件与基于玄武岩中高压巨晶所反演的岩浆演化温压轨迹具有十分吻合的继承演化关系。地球物理探测表明现今西南天山岩石圈的厚度为71km,区域岩石圈演化历程中深度上13.3km的差异足以证明岩石圈拆沉这一地球动力学过程的存在,为由宽SHRIMP年龄谱识别出的岩石圈拆沉作用提供了另一个有力的证据。 相似文献