PT Paths from modal proportions: application to the Koralm Complex,Eastern Alps     

Kurt Stüwe  Roger Powell 《Contributions to Mineralogy and Petrology》1995,119(1):83-93

Thermodynamic pseudosections portray those parts of a petrogenetic grid that are relevant to a given bulk composition and the reactions appearing on them can therefore be used directly to infer the PT path that the rock followed. However, for many ‘normal’ bulk compositions the use of pseudosections is hampered by the fact that they display only few large fields of high thermodynamic variance in the PT range of interest. Here it is discussed how modal information on reaction progress within these fields can be used to determine PT path information for thermodynamically high variant metamorphic assemblages. We use this information on reaction progress to contour pseudosections for modal proportions of minerals using the software package THERMOCALC. The approach is applied to di- tri- and quadrivariant assemblages from the Koralm complex in the eastern Alps. A PT path for these rocks is derived from modal considerations and compared with interpretations of mineral composition contours on the same pseudosection and with conventional thermobarometry. It is shown that at least part of the complex must have cooled initially near isobarically from prevalent peak conditions around 700°C and 14 kbar before the rocks commenced a Barroviantype decompression path.  相似文献   

Erratum: Solar cosmic-ray-produced radionuclides in meteorites     

R. Michel  G. Brinkmann  R. Stück 《Earth and Planetary Science Letters》1983,64(1):174

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Interpretation of spectra of geomagnetic pulsations as a spectrum of modulated oscillations     

Jaroslav Střeštík  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1985,29(4):362-373

Summary The analysis of spectra of modulated oscillations is used to show how these oscillations are distorted when recorded by an instrument whose characteristics depend on frequency, and under what conditions the parameters of the original modulated oscillations can be derived directly from the record. Geomagnetic Pc3 and Pi2 pulsations, recorded at the Budkov Observatory, are discussed; these can be interpreted as amplitude or frequency modulated oscillations.

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Wadi Onib: A dismembered Pan-African ophiolite in the Red Sea Hills of the Sudan   总被引：1，自引：0，他引：1  

I.M. Hussein  A. Kroner  St. Durr 《Precambrian Research》1982,16(4):A52-A53

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Deep crustal reflections from a Vibroseis survey in northern Switzerland     

P. Finckh  J. Ansorge  St. Mueller  Chr. Sprecher 《Tectonophysics》1984,109(1-2)

In 1982 a Vibroseis^® survey comprising 180 km of reflection profiles was run in northern Switzerland in order to investigate the suitability of the crystalline basement for the deposition of highly radioactive waste. A configuration was chosen with 144 channels, 25 m of geophone spacing, 20 s sweeps ranging from 11 to 61 Hz and stacking of 4 or 8 sweeps of 3 simultaneous vibrators at twice the geophone spacing. The listening time was generally 4 s and at 4 sites it was extended to 11s for the detection of deeper crustal reflectors. This survey unravelled the complicated fault and thrust system beneath the Swiss folded Jura mountains.The stack from 4 s to 11 s reveals clearly a strong sloping reflector between 3.0 and 3.5 s which is strong evidence for a pronounced differentiation in the upper crust. A series of reflections is observed between 5.8 and 7.2 s the top of which can be correlated with the Conrad discontinuity.A strong “layered” signal between 9.0 and 9.5 s is interpreted as reflections from the M-discontinuity. The main features are compatible with results from nearby refraction surveys in the southern Rhinegraben rift system which show a distinct velocity increase of about 0.5 km/s in the lower crust at a depth ranging from 15 to 20 km, followed by an inversion zone or a laminated structure before reaching the Moho at about 27 km depth.The correlation of the field recordings with the first 10 s of the up-sweep only, shows some loss of resolution in the uppermost 3 s because of the lower frequency content of the signal. However, the lower parts of the sections are nearly identical. The fact that the deeper reflectors in the sections can consistently be traced laterally is a strong argument for using this processing technique. Thus high-coverage Vibroseis surveys utilizing up-sweep can be processed for deep crustal reflections even if the recording time is restricted to the standard 4 s, provided the surface static corrections are carried out with high precision.  相似文献   

Gold in BHVO-1, BIR-1, DNC-1 and BCR-1 by Fire-Assay Preconcentration Neutron Activation Analysis: Sample Size vs. Accuracy     

Robert M. St. LOUIS 《Geostandards and Geoanalytical Research》1987,11(2):151-157

Four mafic USGS rock standards (BHVO-1, BIR-1, DNC-1, BCR-1) were analyzed at three sample sizes (1, 5, and 10 g) for gold by neutron activation analysis subsequent to fire-assay concentration. The results indicate that large samples, in the order of 10 g, are required to produce consistent results, although analyses of variance indicate that sample sizes of 5 g may be used effectively. The analysis of 1 g samples resulted in a large range of values and high standard deviations. BCR-1 was found to be the most homogeneous of the four standards for gold, followed in decreasing order by BIR-1, DNC-1, and BHVO-1. Data for Ir in BIR-1 and DNC-1 are also presented.  相似文献   

Empirical metallogeny. Depositional environments, lithologic associations and metallic Ores. Vol. 1: Phanerozoic environments, associations and deposits, part A and B: P. Laznicka. (Developments in Economic Geology, 19) Elsevier, Amsterdam, 1985, xxxvi+1758 pp., US $ 176.00/Dfl. 455.00 (hardback, in 2 parts)     

Kurt Von Gehlen 《Ore Geology Reviews》1987,2(4)

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An experimental study of Fe-Mg partitioning between garnet and olivine and its calibration as a geothermometer   总被引：4，自引：0，他引：4  

Hugh St. C. O'Neill  B. J. Wood 《Contributions to Mineralogy and Petrology》1979,70(1):59-70

The partitioning of Fe and Mg between coexisting garnet and olivine has been studied at 30 kb pressure and temperatures of 900 ° to 1,400 °C. The results of both synthesis and reversal experiments demonstrate that K _D (= (Fe/Mg)_gt/(Fe/Mg)_OI) is strongly dependent on Fe/Mg ratio and on the calcium content of the garnet. For example, at 1,000 °C/30 kb, K _D varies from about 1.2 in very iron-rich compositions to 1.9 at the magnesium end of the series. Increasing the mole fraction of calcium in the garnet from 0 to 0.3 at 1,000 ° C increases K _D in magnesian compositions from 1.9 to about 2.5.The observed temperature and composition dependence of K _D has been formulated into an equation suitable for geothermometry by considering the solid solution properties of the olivine and garnet phases. It was found that, within experimental error, the simplest kind of nonideal solution model (Regular Solution) fits the experimental data adequately. The use of more complex models did not markedly improve the fit to the data, so the model with the least number of variables was adopted.Multiple linear regression of the experimental data (72 points) yielded, for the exchange reaction: 3Fe₂SiO₄+2Mg₃Al₂Si₃O₁₂ olivine garnet 2Fe₂Al₂Si₃O₁₂+3Mg₂SiO₄ garnet olivine H ° (30kb) of –10,750 cal and S ° of –4.26 cal deg^–1 mol^–1. Absolute magnitudes of interaction parameters (W _ij ) derived from the regression are subject to considerable uncertainty. The partition coefficient is, however, strongly dependent on the following differences between solution parameters and these differences are fairly well constrained: W _FeMg ^ol -W _FeMg ^gt 800 cal W _CaMg ^gt -W _CaFe ^gt 2,670 cal.The geothermometer is most sensitive in the temperature and composition regions where K _D is substantially greater than 1. Thus, for example, peridotitic compositions at temperatures less than about 1,300 ° C should yield calculated temperatures within 60 °C of the true value. Iron rich compositions (at any temperature) and magnesian compositions at temperatures well above 1,300 °C could not be expected to yield accurate calculated temperatures.For a fixed K _D the influence of pressure is to raise the calculated temperature by between 3 and 6 °C per kbar.  相似文献   

New calibrating functions for short-period body waves of Friuli earthquakes     

Jaroslava Plomerová  Libuše Ruprechtová  Bernd Tittel  Joachim Weyrauch  Kurt Wylegalla  Reviewer A. Zátopek 《Studia Geophysica et Geodaetica》1979,23(2):189-196

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Paleomagnetism in Greece: Indications for relative block movement     

Rudolf Pucsher  Dieter Bannert  Kurt Fromm 《Tectonophysics》1974,22(1-2)

There is a difference of 120° between the strike of the Pindos mountain chain and that of the Argolis peninsula. Both consist of rocks of the same age (Triassic Jurassic).Samples were collected to see if paleomagnetic data also exhibited this difference in angle. 23 samples from two sites and four lava strata of the Pindos resulted in normal and reversed directions with a mean direction D = 334°, I = 22° with α_95° = 9°, and 24 samples from four sites of the Argolis peninsula in a mean direction of D = 82°, I = 19° with α_95° = 17°. This is a declination difference of D = 108°. Therefore, a relative rotational block movement with an angle of about 110° could be assumed. The result depends to a great extent on the dip correction of the lava flows.  相似文献