Franciscan eclogite revisited: Reevaluation of the P–T evolution of tectonic blocks from Tiburon Peninsula, California, U.S.A.     

T. Tsujimori  K. Matsumoto  J. Wakabayashi  J. G. Liou 《Mineralogy and Petrology》2006,88(1-2):243-267

Summary High-grade blocks in the Franciscan complex at Tiburon, California, record relatively low temperature eclogite-facies metamorphism and blueschist-facies overprinting. The eclogite-facies mineral assemblage contains prograde-zoned garnet + omphacite + epidote ± hornblende (katophoritic and barroisitic Ca–Na amphibole) ± glaucophane + phengite (∼3.5 Si p.f.u.) ± paragonite + rutile + quartz. The blueschist-facies mineral assemblage contains chlorite + titanite + glaucophane + epidote ± albite ± phengite (∼3.3 Si p.f.u.). Albite is not stable in the eclogite stage. New calculations based on garnet-omphacite-phengite thermobarometry and THERMOCALC average-P–T calculations yield peak eclogite-facies P–T conditions of P = 2.2–2.5 GPa and T = 550–620 °C; porphyroclastic omphacite with inclusions of garnet and paragonite yields an average-P–T of 1.8 ± 0.2 GPa at 490 ± 70 °C for the pre-peak stage. The inferred counterclockwise hairpin P–T trajectory suggests prograde eclogitization of a relatively “cold” subducting slab, and subsequent exhumation and blueschist-facies recrystallization by a decreasing geotherm. Although an epidote-garnet amphibolitic assemblage is ubiquitous in some blocks, P–T pseudosection analyses imply that the epidote-garnet amphibolitic assemblage is stable during prograde eclogite-facies metamorphism. Available geochronologic data combined with our new insight for the maximum pressure suggest an average exhumation rate of ∼5 km/Ma, as rapid as those of some ultrahigh pressure metamorphic terranes.  相似文献   

PRELIMINARY ANALYSIS OF THE ATMOSPHERIC RADIATIVE HEATING FIELDS IN AUTUMN IN THE MID LATITUDE ARID AREAS OF CHINA   总被引：1，自引：0，他引：1       下载免费PDF全文

Ji Guoliang  K. N. Liou  S. C. Ou  M. D. Chou 《Acta Meteorologica Sinica》1992,6(1):105-116

A parameterized radiation and cloud model developed at the University of Utah,U.S.A.has been used to computethe atmospheric radiative properties in Zhangye area during the pilot experiment of HEIFE in September of 1988.Somecharacteristics of atmospheric radiative heating fields during the autumn in Zhangye area have been analysed,and somequestions that merit attention in the future observation are also discussed in this paper.  相似文献   

The seasonal cycle of the global zonally averaged energy balance     

Szu-cheng S. Ou  K. N. Liou  W. J. Liou 《Theoretical and Applied Climatology》1989,40(1-2):9-23

Summary The annual and seasonal cycle of the global zonally averaged storage and transport of moist static energy (MSE), the surface eddy flux of MSE, and the radiation budget at the top of the atmosphere (TOA) and surface are investigated in this paper. We use the GFDL (Geophysical Fluid Dynamics Laboratory) zonal mean data to compute the storage rate, divergence, and poleward flux of MSE. Surface eddy fluxes are determined based on an empirical formula developed from available climatological data. Radiative fluxes at the TOA and surface are computed from a radiation model. A number of significant features are illustrated by the present analysis in regard to the global annual and seasonal energy balance of the earth-atmosphere system. The storage/release rate of MSE is greater in spring and autumn than in summer and winter. The rate of poleward transport of MSE has a maximum at ~40°N and ~35°S with a value of ~3 × 10¹⁵ W. In terms of the radiation budget, the persistent ITCZ minimum and subtropical maxima of the IR flux distribution are reproduced well in the radiation parameterization program. The incoming solar flux maximum shifts from ~20°N in spring to ~40°N in summer due to the poleward increase in the fraction of daytime. Finally, an examination of the global surface energy balance reveals that the surface net fluxes derived from parameterizations for eddy and radiative fluxes agree well with values derived from observations. This agreement appears to imply that on the global mean, the physical parameterizations used in the present study are reliable in modeling the seasonal surface flux components.

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Zusammenfassung Der jährliche und jahreszeitliche Gang der globalen Zonenmittel der Speicherung und des Transports von latenter Energie (MSE), des Oberflächen-Eddy-Flusses der MSE und des Einstrahlungsbudgets an der Atmosphärengrenze (TOA) als auch auf der Erdoberfläche werden untersucht.Wir verwenden die GFDL Zonenmitteldaten, um die Ladung, Divergenz und den polgerichteten Fluß der MSE zu errechnen. Die Oberflächen-Eddy-Flüsse werden aufgrund einer empirischen Formel bestimmt, die mittels verfügbarer klimatologischer Daten erstellt wurde. Strahlungsflüsse auf der Oberfläche und der Atmosphärengrenze werden mittels eines Einstrahlungsmodells errechnet. Eine Reihe signifikanter Erscheinungen werden in der vorliegenden Analyse dargestellt mit Hinblick auf das globale jährliche und jahreszeitliche Energiegleichgewicht des Erde-Atmosphäre-Systems. Die Ladungs- und Entladungsrate des MSE ist im Frühjahr und Herbst größer als im Sommer und Winter. Die Spitzen des polgerichteten Transports der MSE liegen bei 40° N und 35° S mit einem Wert von ca. 3 × 10¹⁵ W. In bezug auf das Einstrahlungsbudget werden die persistenten ITKZ-Minima und die subtropischen Maxima der IR-Flußverteilung gut von dem Einstrahlungsparameterisierungsprogramm dargestellt. Die Sonneneinstrahlungsflußspitzen verschieben sich von 20° N im Frühjahr nach 40° im Sommer aufgrund der gegen den Pol hin zunehmenden Tageslänge. Zuletzt zeigen die Untersuchungen des globalen Oberflächenenergiegleichgewichts auf, daß die Oberflächennettoflüsse, abgeleitet von der Parameterisierung für Eddy- und Einstrahlungsflüsse, mit den beobachteten Werten gut übereinstimmen. Diese Übereinstimmung impliziert offensichtlich, daß im globalen Durchschnitt die physikalische Parametrisierung, die in dieser Studie angewendet wurde, verläßliche Modelle der jahreszeitlichen Oberflächenflußkomponenten liefern kann.

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With 8 Figures  相似文献   

An experimental investigation of heulandite-laumontite equilibrium at 1000 to 2000 bar P fluid     

M. Cho  S. Maruyama  J. G. Liou 《Contributions to Mineralogy and Petrology》1987,97(1):43-50

The univariant reaction governing the upper stability of heulandite (CaAl₂Si₇O₁₈·6H₂O), heulandite=laumontite+3 quartz+2H₂O (1), has been bracketed through reversal experiments at: 155±6° C, 1000 bar; 175±6° C, 1500 bar; and 180±8° C, 2000 bar. Reversals were established by determining the growth of one assemblage at the expense of the other, using both XRD and SEM studies. The standard molal entropy of heulandite is estimated to be 783.7±16 J mol^–1 K^–1 from the experimental brackets. Predicted standard molal Gibbs free energy and enthalpy of formation of heulandite are –9722.3±6.3 kJ mol^–1 and –10524.3±9.6 kJ mol^–1, respectively. The reaction (1), together with the reaction, stilbite=laumontite+3 quartz+3 H₂O, defines an invariant point at which a third reaction, stilbite=heulandite+ H₂O, meets. By combining the present experimental data with past work, this invariant point is located at approximately 600 bar and 140° C. Heulandite, which is stable between the stability fields of stilbite and laumontite, can occur only at pressures higher than that of the invariant point, for = P _total.These results are consistent with natural parageneses in low-grade metamorphic rocks recrystallized in equilibrium with an aqueous phase in which is very close to unity.  相似文献   

Possible depth limit for underplating by a seamount     

Shigenori Maruyama  J.G. Liou 《Tectonophysics》1989,160(1-4):327-337

The Cazadero metabasite allochthon is located within the central melange belt of the northern California Coast Ranges, U.S.A. It composed mainly of pillowed and massive mafic flows, hyaloclastite and minor pelagic sediments. It is about 3 × 15 km² in extent, and is in fault contact with Late Mesozoic fore-arc flysch deposits of the Great Valley sequence. Three metamorphic zones were mapped in the allochthon, as follows-in order of increasing metamorphic grade: the lawsonite, the pumpellyite and the epidote zone. Ca---Na pyroxenes are ubiquitous; they were used to estimate the P-T path, together with the oxygen isotope geothermometry of Taylor and Coleman. The result shows a bending point in the P-T path for blueschist facies metamorphism of the Cazadero allochthon. At shallow depths, lower grade metamorphism proceeded under predominant pressure-increase from 4 to 7 kbar at nearly constant T of about 150–200 °C, whereas after passing the bending point higher-grade metamorphism occurred with increasing temperature from 200 to 350 °C at nearly constant P of about 7–8 kbar.

The bending point reflects the depth of transfer of underplating materials from the oceanic lithosphere and its overlying sediments to the hanging wall plate. Either seamount volcanics and pelagic sediments, or mixed packages of fragmented oceanic crust with trench-fill turbidites, were subducted beneath the North American plate. They were subjected to early lawsonite- and pumpellyite-zone metamorphism with very low geothermal gradient. We infer that when they reached about 20 km depth, underplating occurred and the metamorphosed rocks became part of the hanging wall. Heat conduction from the overlying hydrated mantle wedge caused a temperature increase at nearly constant depth. The earlier recrystallized seamount volcanics and pelagic sediments were then metamorphosed at a much higher geothermal gradient. The Cazadero allochthon has suffered extremely high P/T subduction zone metamorphism and it preserves very well the record of Cretaceous subduction-underplating processes.  相似文献   

Discussion on a paper by D. D. liou     

A. G. Collings  E. R. Johnson  D. D. Liou 《地震工程与结构动力学》1983,11(3):437-438

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Analytic solutions for soil-structure interaction in layered media     

Gin-Show Liou 《地震工程与结构动力学》1989,18(5):667-686

The total system studied in this paper is a layered soil stratum with a rigid bedrock and a cylindrical cavity on the surface. Analytic solutions for the layered medium with prescribed harmonic displacement time history on the surface of the cylindrical cavity are presented. The whole soil domain is divided into interior and exterior domains. The interior domain is the projection of the cylindrical cavity down to the rigid bedrock, whereas the exterior domain is then the soil medium complement to the interior domain. The displacement and stress fields in both domains are expanded as an infinite series of Fourier components with respect to the azimuth. For each Fourier component in the infinite series, the solutions for both domains are found independently by solving the general differential equations of wave propagation satisfying the boundary conditions of the top surface and the lower rigid boundary. Displacement and stress continuity conditions are then imposed on the vertical interface between the two domains using the formulation of a weighted residual. For the soil-structure interaction problem, the impedance matrix at the interface between the structure and the soil medium can be easily generated using the analytic solutions, which can then be combined with the finite element model of the structure. A simple example is presented to demonstrate the effectiveness of the procedure presented.  相似文献   

Ultrahigh-pressure metamorphism and tectonics   总被引：11，自引：0，他引：11  

J. G. Liou  S. Banno  W. G. Ernst 《Island Arc》1995,4(4):233-239

Abstract Recognition of several ultrahigh-pressure (UHP) metamorphic terranes in continental collision belts has revolutionized the concept of geodynamic processes. In order to facilitate better communication and focus among active investigators, the Task Group III-6 of the International Lithosphere Program'Ultrahigh-Pressure Metamorphism and Geodynamics in Collision-type Orogenic Belts'held the first two day workshop at Stanford University in December, 1994. Petrotectonic settings, mineral paragenesis, geochronoldgy, and geochemical characteristics of UHP rocks from several recognized and suspected UHP terranes were addressed. This special issue presents 11 papers from the more than 50 contributions from the 88 participants representing 15 countries. Many challenging petrotectonic and petrochemical problems remain to be investigated. These include detailed P-T time paths for both the UHP unit and adjacent units, the role of fluids at mantle depths, deep seismic profiles and mechanisms and rate of exhumation of the UHP unit.  相似文献   

Petrology and retrograde P-T path for eclogites of the Maksyutov Complex, Southern Ural Mountains, Russia     

R. J. Beane    J. G. Liou    R. G. Coleman  M. L. Leech 《Island Arc》1995,4(4):254-266

Abstract The Maksyutov Complex, situated in the southern Ural Mountains of Russia, is the first location where quartz aggregates within garnets exhibiting radial fractures were identified as coesite pseudomorphs (Chesnokov & Popov 1965). The complex consists of two tectonic units: a structurally lower eclogite-bearing schist unit and an overlying meta-ophiolite unit. Both units show evidence for multiple stages of metamorphism and deformation. The high-pressure metamorphism of the eclogite-bearing schist unit, discussed in this report, is suspected to be related to a collision between the Russian platform and a fragment of the Siberian continent during the early Cambrian. At least three stages of metamorphism (M_1-3) and two stages of deformation (S₁ and S₂) were observed in thin sections: M₁) garnet (Alm_55-60, Prp_22-28, Grs_16-20) + omphacite (Jd_46-56) + phengite (Si ≅ 3.5) + rutile; M₂) garnet + glaucophane ± lawsonite + white mica; and M₃) epidote + chlorite ± albite ± actinolite + white mica. Observed mineral parageneses define a retrograde P-T path for the eclogite. Mineral assemblages within the most representative eclogite from the lower unit of the Maksyutov Complex indicate minimum peak pressures of 15 kbar at temperatures of approximately 600°C. If the presence of coesite pseudomorph is confirmed, the peak ultrahigh-pressure metamorphism may be as high as 27 kbar at 615°C.  相似文献   

Titanium solubility in coexisting garnet and clinopyroxene at very high pressure: the significance of exsolved rutile in garnet   总被引：3，自引：0，他引：3  

R.Y. Zhang  S.M. Zhai  J.G. Liou 《Earth and Planetary Science Letters》2003,216(4):591-601

Exsolution microstructures including ilmenite±garnet in clinopyroxene and rutile in garnet are common in clinopyroxenite and eclogite from the Sulu ultrahigh-pressure (UHP) terrane. In order to understand the phase relations and Ti solubility in both garnet and clinopyroxene in a natural TiO₂-bearing system, several experiments at 5-15 GPa, 1000-1400°C were carried out using the multianvil high-pressure apparatus. The Hujianlin ilmenite-rich garnet clinopyroxenite showing exsolution microstructure was selected as starting material, because it closely approaches a composition lying in the TiO₂-CaO-MgO-FeO-Al₂O₃-SiO₂ system. Except for minor melt in one experiment at 1400°C and 5 GPa, other run products contain majoritic garnet+clinopyroxene±ilmenite (or rutile) and exhibit neoblastic texture. With increasing pressure, Ti and Ca, Mg and Si contents of neoblastic garnet increase with decreasing Al. The principal coupled substitutions are Ca²⁺Ti⁴⁺→2Al³⁺ and Si⁴⁺Mg²⁺→2Al³⁺ responding to majorite component increase. Titanium solubility (0.8-4.5 wt% as TiO₂) in garnet and Grt_Ti/Cpx_Ti ratio have a pronounced positive correlation with pressure between 5 and 15 GPa. On the other hand, the coexisting clinopyroxene contains low Ti (0.17-0.53 wt% as TiO₂), and shows no significant pressure effect. Rutile exsolution in garnet is coupled to that of pyroxene exsolution; both are exsolved from majoritic garnet on decompression. Therefore, the amount of such exsolved lamellae is a potential indicator of high-pressure metamorphism in exhumed rocks, whereas the TiO₂ content of clinopyroxene coexisting with garnet is not sensitive to pressure change.  相似文献