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Jacques Kornprobst Jean-Robert Kienast Jean-Claude Vilminot 《Contributions to Mineralogy and Petrology》1979,69(1):49-63
Metamorphic rocks at Milos are known in small outcrops beneath the volcanic formations, as xenoliths in the Traphores volcanic breccia and as pebbles in the Paleochora Quaternary deposits. These rocks seem to belong to three different metamorphic units which probably have intricate relationships in the basement: — the eclogites unit shows garnetjadeite or garnet-omphacite primary associations, with apparently late crystallization of lawsonite phenoblasts an recrystallization features at relatively low temperatures; — the glaucophane schist unit exhibits Jadeite+quartz or glaucophane+lawsonite primary mineralogy; — the greenschist facies unit shows low-pressure main assemblages, most generally developed after high-pressure events. The two former units involve tholeiitic meta-igneous rocks, having been spilitized before metamorphism; they generally suffered more or less advanced recrystallization features in the low-pressure field of the greenschist facies. The third unit shows only meta-sedimentary rocks, with the sole exception of one single meta-doleritic pebble having calk-alkaline affinities.Petrological and mineralogical studies, based upon 15 bulk-rock compositions and 178 probe-analysed data points, lead to suspect at least 2, perhaps 3, different metamorphic events rather than one single metamorphic evolution, to account for the 3 U distinguished. From the observation of the mineralogical assemblages and their evolution, the former events (stages 1 and 2) could be related to rapid subduction of ocean-floor or back-arc basalts, whereas, during the latter event (stage 3), the rocks experienced crystallization conditions involving both decreasing pressures and increasing temperatures. 相似文献
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Jacques Kornprobst 《Contributions to Mineralogy and Petrology》1977,61(3):267-277
A very uncommon garnet-zoning—Ca poor centre and Ca rich margin—has been observed, in a granulite facies rock. Calculation of equilibrium at each stage of the garnet growth led to apply in this particular case, as well as for the most garnet-zoning instances, the Rayleigh fractionation model, the fractionation factor Ca being less than 1 at the beginning of the crystallization. Subsequent coronitisation, at lower P and/or higher T, involved the development of orthopyroxene and plagioclase in equilibrium with a thin (15 thick) Ca-Mg poor and Fe rich outer cuticle of the garnet: thus the garnet lattice appears to be not so refractory as previously admitted, and in most coronitisation processes involving garnet such an outer cuticle must be considered as a component of the new mineral assemblage. 相似文献
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G.?Dubosclard F.?DonnadieuEmail author P.?Allard R.?Cordesses C.?Hervier M.?Coltelli E.?Privitera J.?Kornprobst 《Bulletin of Volcanology》2004,66(5):443-456
Besides their common use in atmospheric studies, Doppler radars are promising tools for the active remote sensing of volcanic eruptions but were little applied to this field. We present the observations made with a mid-power UHF Doppler radar (Voldorad) during a 7-h Strombolian eruption at the SE crater of Mount Etna on 11–12 October 1998. Main characteristics of radar echoes are retrieved from analysis of Doppler spectra recorded in the two range gates on either side of the jet axis. From the geometry of the sounding, the contribution of uprising and falling ejecta to each Doppler spectrum can be discriminated. The temporal evolution of total power backscattered by uprising targets is quite similar to the temporal evolution of the volcanic tremor and closely reproduces the overall evolution of the eruption before, during and after its paroxysm. Moreover, during the sharp decrease of eruptive activity following the paroxysm, detailed analysis of video (from camera recording), radar and seismic measurements reveals that radar and video signals start to decrease simultaneously, approximately 2.5 min after the tremor decline. This delay is interpreted as the ascent time through a magma conduit of large gas slugs from a shallow source roughly estimated at about 500 m beneath the SE crater. Detailed analysis of eruptive processes has been also made with Voldorad operating in a high sampling rate mode. Signature of individual outburst is clearly identified on the half part of Doppler spectra corresponding to rising ejecta: temporal variations of the backscattered power exhibit quasi periodic undulations, whereas the maximum velocity measured on each spectrum displays a sharp peak at the onset of each outburst followed by a slow decay with time. Periodicity of power variations (between 3.8 and 5.5 s) is in agreement with the occurrence of explosions visually observed at the SE vent. Maximum vertical velocities of over 160 m s–1 were measured during the paraoxysmal stage and the renewed activity. Finally, by using a simplified model simulating the radar echoes characteristics, we show that when Voldorad is operating in high sampling rate mode, the power and maximum velocity variations are directly related to the difference in size and velocity of particles crossing the antenna beam.Editorial responsibility: A. Woods 相似文献
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分析了全球一些有代表性的上地幔尖晶石橄榄岩和斜长石橄榄岩中各矿物的化学成分变化特征。发现在斜长石橄榄岩中，尖晶石和斜方辉石富Ｔｉ，且Ｔｉ含量随Ｃｒ／（Ｃｒ＋Ａｌ）的增大而增大；单斜辉石富Ｔｉ贫Ｎａ，其Ｔｉ含量随Ｎａ含量的增大而减少。据此，结合实验结果，可以肯定世界各地大多数斜长石二辉橄榄岩在斜长石相域内未经受部分熔融。岩体所曾经受的部分熔融只发生在尖晶石或石榴石相。它们的相对熔融度可以用下面两个指标来估计：（１）最贫Ｔｉ尖晶石的Ｃｒ／（Ｃｒ＋Ａｌ）；（２）单斜辉石的最高Ｎａ含量。对于尖晶石橄榄岩，从二辉橄榄岩、方辉橄榄岩到纯橄榄岩，其尖晶石和斜方辉石的Ｃｒ／（Ｃｒ＋Ａｌ）逐渐增大，而含量很低的Ｔｉ或Ｎａ在尖晶石、斜方辉石及单斜辉石中保持不变或趋向逐渐减小。尖晶石橄榄岩的相对熔融度可据尖晶石的Ｃｒ／（Ｃｒ＋Ａｌ）和单斜辉石的Ｎａ含量来判断。 相似文献
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J. Kornprobst 《Contributions to Mineralogy and Petrology》1969,23(4):283-322
The ultrabasic rocks which form the Beni Bouchera massif are schistose and folded isoclinally. They outcrop at the center of a late formed anticline under a series of granulite facies precambrian or lower paleozoic rocks. The ultrabasic rocks appear to have been in situ during the major structural development of the series and were emplaced at the time of metamorphism. The massif itself is essentially a peridotite, apparently layered, which contains pyroxenite bands (about 3% of the total volume of the massif). The peridotites are olivinerich containing two aluminous pyroxenes and spinel. The pyroxenites are however quite varied. They are frequently banded themselves and in several centimeters thickness can vary from enstatite rocks at the exterior of the layers to garnet clinopyroxenites at the center with websterite and garnet websterite as intermediate rock type. They are also present as monofacies bands of enstatite or garnet clinopyroxenite rock. Occasionally the minerals in these bands show exsolution features.Thirty six new rock and mineral chemical analyses are presented here. An attempt is made to use these data correlated with abundant bibliographic material in order to evaluate the conditions of formation of the rock types. The temperature range is estimated to be 1100–1200° C, pressures between 15 and 20 kbs in the latest facies and 1400°C and 25 kbs for a primary phase represented by the pyroxenites showing marked exsolution features. Various arguments lead to the conclusion that the pyroxenite bands crystallized from a liquid which was in equilibrium with the solid lherzolite.One sees in the Beni Bouchera the results of anatectic melting of an aluminous peridotite which originated in the upper mantle. This partial fusion was caused by the adiabatic upward movement of the mantle material toward the lower crust where tangential tectonic movements emplaced it as a solidified mass in an orogenic root zone under granulite facies conditions.
Equipe de recherches associée au C.N.R.S.: Pétrogenèse des roches éruptives et métamorphiques
Plusieurs missions sur le terrain ont été effectuées avec le concours du Service Géologique du Maroc et grâce, particulièrement, à G. Choubert, M. Diouri, Y. Ennadifi et A. FaureMuret. Les études pétrographiques ont été poursuivies à la Sorbonne sous la direction de J. Jung et de J. Ravier. Une aide inestimable m'a été apportée par M. J. O'Hara pour la rédaction de ce mémoire. A divers titres j'ai largement bénéficié des conseils et critiques de B. Azambre, F. Conquere, M. Durand-Delga, M. Fonteilles, J. R. Kienast, B. Velde, D. Velde et J. C. Vilminot 相似文献
Equipe de recherches associée au C.N.R.S.: Pétrogenèse des roches éruptives et métamorphiques
Plusieurs missions sur le terrain ont été effectuées avec le concours du Service Géologique du Maroc et grâce, particulièrement, à G. Choubert, M. Diouri, Y. Ennadifi et A. FaureMuret. Les études pétrographiques ont été poursuivies à la Sorbonne sous la direction de J. Jung et de J. Ravier. Une aide inestimable m'a été apportée par M. J. O'Hara pour la rédaction de ce mémoire. A divers titres j'ai largement bénéficié des conseils et critiques de B. Azambre, F. Conquere, M. Durand-Delga, M. Fonteilles, J. R. Kienast, B. Velde, D. Velde et J. C. Vilminot 相似文献
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Ocean-continent boundary off the Iberian margin: A serpentinite diapir west of the Galicia Bank 总被引：1，自引：0，他引：1
G. Boillot S. Grimaud A. Mauffret D. Mougenot J. Kornprobst J. Mergoil-Daniel G. Torrent 《Earth and Planetary Science Letters》1980,48(1):23-34
A serpentinite diapir made of altered plagioclase-bearing lherzolites, has been emplaced west of the Galicia Bank at the boundary between oceanic crust and the probable thinned continental crust, that underlies the Iberian margin. 相似文献
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橄榄岩中尖晶石化学成分分带的机理及其地质意义 总被引：1，自引：1，他引：1
橄榄岩中尖晶石的化学成分分带显示，在由温度降低引起的亚固相平衡过程中，与橄榄石及斜方辉石相邻的尖晶石边缘贫Mg和Al、富Fe和Cr，而与单斜辉石相邻的尖晶石边线相反。尖晶石的Fe和Mg分带为其他矿物的粒间Fe－Mg离子扩散所致；尖晶石中的Cr和Al分带则是尖晶石晶体内部Cr－Al离子的交互扩散所致。本文从热力学理论角度说明了尖晶石晶体内部的Cr－Al交互扩散受其Fe－Mg分带的控制；从热力学计算证明了尖晶石内Al必须从富Fe处向富Mg处扩散，解释了尖晶石中Mg和Al及Fe和Cr分带的一致性。 相似文献
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The emplacement of Pyrenean lherzolites is a fascinating problem to tackle because of the unusual location of the lherzolites within sediments and the numerous constraints which are currently available on the Pyrenean belt (plates kinematics, petrology, structural geology, geochemistry, geophysics). Our model [1] represents an attempt to integrate the emplacement of lherzolites within the geodynamic evolution of the Pyrenees. However, on the basis of imprecise statements and observations, and neglecting or quoting incorrectly several previous works. Fischer [2] considers that we failed to address a number of problems relevant to the evolution of the North Pyrenean Fault Zone. Most of his comments find an answer in a careful reading of our article; nevertheless the following points must be clearly emphasized. 相似文献