Peridotite Melting at 1 GPa: Reversal Experiments on Partial Melt Compositions Produced by Peridotite-Basalt Sandwich Experiments   总被引：3，自引：0，他引：3  

FALLOON  TREVOR J.; DANYUSHEVSKY  LEONID V.; GREEN  DAVID H. 《Journal of Petrology》2001,42(12):2363-2390

One of the goals of igneous petrology is to use the subtle andmore obvious differences in the geochemistry of primitive basaltsto place constraints on mantle composition, melting conditionsand dynamics of mantle upwelling and melt extraction. For thisgoal to be achieved, our first-order understanding of mantlemelting must be refined by high-quality, systematic data oncorrelated melt and residual phase compositions under knownpressures and temperatures. Discrepancies in earlier data onmelt compositions from a fertile mantle composition [MORB (mid-oceanridge basalt) Pyrolite mg-number 87] and refractory lherzolite(Tinaquillo Lherzolite mg-number 90) are resolved here. Errorsin earlier data resulted from drift of W/Re thermocouples at1 GPa and access of water, lowering liquidus temperatures by30–80°C. We demonstrate the suitability of the ‘sandwich’technique for determining the compositions of multiphase-saturatedliquids in lherzolite, provided fine-grained sintered oxidemixes are used as the peridotite starting materials, and thechanges in bulk composition are considered. Compositions ofliquids in equilibrium with lherzolitic to harzburgitic residueat 1 GPa, 1300–1450°C in the two lherzolite compositionsare reported. Melt compositions are olivine + hypersthene-normative(olivine tholeiites) with the more refractory composition producinga lower melt fraction (7–8% at 1300°C) compared withthe model MORB source (18–20% at 1300°C). KEY WORDS: mantle melting; sandwich experiments; reversal experiments; anhydrous peridotite melting; thermocouple oxidation; olivine geothermometry  相似文献   

Effect of Silica Activity on OH- IR Spectra of Olivine: Implications for Low-aSiO2 Mantle Metasomatism     

MATVEEV  S.; O'NEILL  H. ST. C.; BALLHAUS  C.; TAYLOR  W. R.; GREEN  D. H. 《Journal of Petrology》2001,42(4):721-729

Hydrogen solubility and hydroxyl substitution mechanism in olivineat upper-mantle conditions are not only a function of pressure,temperature, water fugacity and hydrogen fugacity, but are alsoinfluenced by silica activity. Olivine synthesized in equilibriumwith magnesiowüstite displays hydroxyl stretching bandsin the wavenumber range from 3640 to 3430 cm^–1. In contrast,olivine in equilibrium with orthopyroxene shows absorption bandsin a narrower wavenumber range from 3380 to 3285 cm^–1.The two fundamentally different spectra are assigned to hydroxylin tetrahedral and octahedral sublattices, respectively. Olivinein equilibrium with orthopyroxene is also less capable of incorporatinghydroxyl, relative to olivines in equilibrium with magnesiowüstite,by about a factor of ten. A comparison of spectra obtained aspart of this study with hydroxyl spectra of natural mantle olivinesshows that the latter display hydroxyl stretching patterns reminiscentof equilibrium with magnesiowüstite, although undoubtedlyolivine in the Earth’s mantle coexists with orthopyroxene.This may be attributed to a metasomatic overprint by a low-silicafluid and/or melt that was in reaction relationship with orthopyroxene.A likely metasomatic agent is a carbonatitic melt. When carbonatiticmelts decompose to oxides and CO₂, they may temporarily imposea low-aSiO₂ environment inherited by the olivine structure.If this suggestion proves true, Fourier transform IR spectroscopymay be used to fingerprint metasomatic episodes in the lithosphericmantle. KEY WORDS: FTIR spectrometry; olivine; mantle; metasomatism; water  相似文献   

THE EAEG'S CHOICE OF UNITS*     

R. GREEN 《Geophysical Prospecting》1968,16(1):1-3

The use of MKS system units in preference to the cgs system facilitates accurate numerical calculation in magnetostatic problems in geophysics and the practice of stating the precise dimensions of every unit guards against confusion. Suggestions are made for the unique definition of quantities such as magnetic potential, etc. for which the undesirable circumstance of arbitrary alternatives still persists.  相似文献   

Experimental Investigation of Eclogite Rheology and Its Fabrics at High Temperature and Pressure   总被引：7，自引：0，他引：7  

J. ZHANG  H. W. GREEN 《Journal of Metamorphic Geology》2007,25(2):97-115

Eclogite plays an important role in mantle convection and geodynamics in subduction zones. An improved understanding of processes in the deeper levels of subduction zones and collision belts requires information on eclogite rheology. However, the deformation processes and associated fabrics in eclogite are not well understood. Incompatible views of deformation mechanism have been proposed for both garnet and omphacite. We present here deformation behaviour of eclogite at temperatures of 1027–1427 °C, confining pressures of 2.5–3.5 GPa, and strain rates of 1 × 10^?5 s^?1 to 5 × 10^?4 s^?1. We obtained a power‐law creep for the high temperature and pressure deformation of a ‘dry’ eclogite (50 vol.% garnet, 40% omphacite and 10% quartz) with A = 10^{3.3 ± 1.0}, n = 3.5 ± 0.4, ΔE =403 ± 30 KJ mol^?1 and ΔV = 27.2 cm³ mol^?1. The two principal minerals of eclogite have greatly different strengths. Progressive increase of garnet results in a smooth increase in strength. Analysis by electron back‐scattered diffraction shows that: (1) garnet displays pole figures with near random distributions of misorientation angle under both dry and wet conditions; (2) omphacite shows pronounced lattice preferred orientations (LPOs), suggesting a dominant dislocation creep mechanism. Further investigation into the water effects on eclogite show: (3) water content does not influence the style of omphacite fabric but increases slightly the fabric strength; (4) grain boundary processes dominate the deformation of garnet under high water fugacity or high shear‐strain conditions, yielding a random LPO similar to that of non‐deforming garnet, despite the strong shape preferred orientation (SPO) observed. {110} [001] slip may dominate the deformation of rutile. Quartz displays complicated and inconsistent LPOs in eclogite. These results are remarkably similar to observations from deformed eclogites in nature.  相似文献   

APPLICATION OF A HILBERT TRANSFORM METHOD TO THE INTERPRETATION OF SURFACE-VEHICLE MAGNETIC DATA*     

R. GREEN  J. M. STANLEY 《Geophysical Prospecting》1975,23(1):18-27

The development of an alkali vapour vehicle borne magnetometer providing very high resolution and a high sampling rate has called for reconsideration of interpretation procedures. With continuous profiling at ground level, the close proximity to near surface structures requires that the precise interpretation of geological boundaries be of paramount importance. Rapid digital recording also demands efficient data processing. Both these requirements can be met by the method described. Essentially the method reduces to a simple Hilbert transform of the magnetic profile. The calculation provides an extremely well defined position of the contact and accurate specification of the dip, strike, depth of overburden, and magnetic susceptibility parameters. Particular advantages are tolerance to high frequency noise, independence from a predetermined origin and baseline, and freedom from subjective judgements.  相似文献   

FIELD PROCESSING OF MAGNETIC DATA*     

R. GREEN 《Geophysical Prospecting》1980,28(3):384-391

This paper deals with the practical problem of processing magnetic data in the field, and it shows how the parameters describing a geological contact can be obtained quickly and conveniently on the basis of five measurements. The complete interpretation can be performed in the field using a programmable calculator. For a small ground-party the method greatly improves the quality of the field-work and the interpretation of the magnetic data. The method has been applied to the data from a magnetic survey over the Mooki Fault (Gunnedah-Manilla, N.S.W.), and the results are discussed as an illustration of the efficacity of the method as a field procedure.  相似文献   

Experimental Petrology of a Highly Potassic Magma   总被引：3，自引：0，他引：3  

EDGAR  A. D.; GREEN  D. H.; HIBBERSON  W. O. 《Journal of Petrology》1976,17(3):339-356

The melting behaviour of a highly potassic biotite mafuriteof the Central African olivine leucitite kindred has been studiedexperimentally as a function of pressure (to 30kb) temperature,and water content (0%, 5%, 15%, 25%, and 40% H₂O). Olivine isthe liquidus phase up to 30 kb for all water contents studiedexcept for anhydrous (clinopyroxene on the liquidus) and 15%H₂O (phlogopite on the liquidus) conditions. Analyses of phasescrystallizing from the biotite mafurite show that pressure hasvery little effect on the composition of clinopyroxene whichis extremely calcium-rich, and low in Al₂O₃ and TiO₂ for allconditions investigated. Phlogopite has low TiO₂ content andtitanphlogopite cannot be a refractory phase in the upper mantlecausing Ti-depletion in partial melts in equilibrium with titanphlogopite.There are apparently no conditions where the extremely potassicbiotite mafurite could be a partial melt from pyrolite but derivationfrom an olivine+clinopyroxene+phlogopite+ilmenite assemblageoccurring as ‘enriched’ patches in the upper mantle,is possible. Liquids in equilibrium with phlogopite as a residualphase at 30 kb would be olivine nephelinites with approximately5% K₂O, Na₂O/K₂O 1 and TiO₂ > 5+. Crystal elutriation withtransported residual phlogopite reacting (phlogopite+liquid1 olivine+liquid 2) at lower pressures provides a mechanismfor K-enrichment and generating Na₂O/K₂O < 1.  相似文献   

REMANENT MAGNETIZATION AND THE INTERPRETATION OF MAGNETIC ANOMALIES     

R. GREEN 《Geophysical Prospecting》1960,8(1):98-110

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Cooperation in Africa     

DEREK GREEN 《Geology Today》1988,4(5):163-163

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Temporal Evolution and Petrogenesis of an Archaean Crustal Segment at Yellowknife, N.W.T., Canada     

GREEN  D. C.; BAADSGAARD  H. 《Journal of Petrology》1971,12(1):177-217

Geochronology of several Archaean rock units in the Slave Provinceestablishes a sequence of events which may be treated as a singletectonic cycle, approximately 75 m.y. in duration, leading tothe formation of a new crustal segment. The oldest rocks (2650m.y.) are basic metavolcanics with largely calc-alkaline characteristics.Metamorphic adjustment to greenschist facies conditions is largelyisochemical but departures from regular serial variation inalkalis are noted. Comparison with experimental studies suggeststhat the basalt-dacite volcanic association is probably theearly extrusive expression of the subcrustal processes whichled to the intrusion of calc-alkaline batholiths into the deformingvolcanic-sedimentary pile. Zircon U-Pb and whole rock Rb-Sr isochron ages of 2620–2640m.y. are recorded for the syn-kinematic quartz diorite batholithsand 2590–2610 m.y. for the major late-kinematic bodies.Pegmatitic adamellites (2575±25 m.y.) are the youngestplutonic units. Regional metamorphism of the andalusite-sillimanitefacies series reflects the relative unimportance of load pressurein the thin-crustal Kenoran deformation. Comparison of the resultsobtained by the three radiometric methods confirms that an intervalof over 100 m.y. may elapse between the time of emplacementof a given rock unit and the subsequent closure of the biotiteK-Ar system. The sequence of K-Ar mineral dates is in accordwith the relative argon retentivities of the various minerals.  相似文献