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41.
Deep seismic reflection and refraction profiling along the Aquitaine shelf (Bay of Biscay) 总被引:2,自引:0,他引:2
Bertrand Pinet Lucien Montadert ECORS Scientific Party 《Geophysical Journal International》1987,89(1):305-312
Summary. The 300 km ECORS - Bay of Biscay profile was carried out along the Aquitaine shelf and comprised a complete set of experiments including zero-offset and 7.5 km constant offset vertical seismic reflection and six expanding spread profiles. Large offset recordings were fundamental for the definition of the layered lower crust and the Moho, while ESPs provided decisive complementary information for the geological interpretation. These data show a strong variation in crustal thickness from about 20 km beneath the rifted Parentis basin, a failed arm of the oceanic Bay of Biscay, up to 35 km to the north below the Armorican shelf, in the Hercynian domain, and to the south below the Cantabria shelf, in the vicinity of the Pyrenean deformation front. The results have important implications for the behaviour of the crust during the formation of rifted sedimentary basins and during continental collision. 相似文献
42.
Jean-Paul Montagner Phyllis Ho-Liu Hiroo Kanamori 《Geophysical Journal International》1990,103(3):757-758
Books Reviewed in this Article:
Seismic tomography and mantle circulation Eds O'Nions, R. K. & Parsons, B., Royal Society of London Special Publication , 1989, ISBN 0854 033823. 相似文献
Seismic tomography and mantle circulation Eds O'Nions, R. K. & Parsons, B., Royal Society of London Special Publication , 1989, ISBN 0854 033823. 相似文献
43.
44.
根据秦岭地区金矿床中黄铁矿特征,总结出典型的微细浸染型和含金石英脉型两种类型矿床特征。黄铁矿与金矿关系密切,含金黄铁矿多产于成矿的富集地段。通过对该区黄铁矿标型特征(晶形、粒级与热电性和微量元素)的系统研究,认为黄铁矿标型特征的研究,对深部找金矿与远景评价具有指导意义。 相似文献
45.
Jean-Paul Poirier 《Comptes Rendus Geoscience》2017,349(2):49-52
The strong earthquake that struck Shaanxi, Shanxi and several other Chinese provinces in 1556 is generally considered as the deadliest of all earthquakes. It is said that the Chinese annals reported 830,000 casualties. We give here a translation into French of the relevant passage of the annals, as well as of a testimony of a survivor Qin Keda, and of a text engraved on a stela. 相似文献
46.
Julien Berger Renaud Caby Jean-Paul Liégeois Jean-Claude C. Mercier Daniel Demaiffe 《Contributions to Mineralogy and Petrology》2011,162(4):773-796
We show here that the Amalaoulaou complex, in the Pan-African belt of West Africa (Gourma, Mali), corresponds to the lower
and middle sections of a Neoproterozoic intra-oceanic arc. This complex records a 90–130-Ma-long evolution of magmatic inputs
and differentiation above a subducting oceanic slab. Early c. 793 Ma-old metagabbros crystallised at lower crustal or uppermost
mantle depths (25–30 km) and have geochemical characteristic of high-alumina basalts extracted from a depleted mantle source
slightly enriched by slab-derived sedimentary components ((La/Sm)N < 1; εNd: +5.4–6.2; 87Sr/86Sr: 0.7027–0.7029). In response to crustal thickening, these mafic rocks were recrystallised into garnet-granulites (850–1,000°C;
10–12 kbar) and subject to local dehydration–melting reactions, forming trondhjemititic leucosomes with garnet–clinopyroxene–rutile
residues. Slightly after the granulitic event, the arc root was subject to strong HT shearing during partial exhumation (detachment
faults/rifting or thrusting), coeval with the emplacement of spinel- and garnet-pyroxenite dykes crystallised from a high-Mg
andesitic parental magma. Quartz and hornblende-gabbros (700–660 Ma) with composition typical of hydrous volcanic rocks from
mature arcs ((La/Sm)N: 0.9–1.8; εNd: +4.6 to +5.2; 87Sr/86Sr: 0.7028–0.7031) were subsequently emplaced at mid-arc crust levels (~15 km). Trace element and isotopic data indicate that
magmas tapped a depleted mantle source significantly more enriched in oceanic sedimentary components (0.2%). Exhumation occurred
either in two stages (700–660 and 623 Ma) or in one stage (623 Ma) with a final exhumation of the arc root along cold P-T
path (550°C, 6–9 kbar; epidote–amphibolite and greenschist facies conditions) during the main Pan-African collision event
(620–580 Ma). The composition of magmas forming the Cryogenian Amalaoulaou arc and the processes leading to intra-arc differentiation
are strikingly comparable to those observed in the deep section of exposed Mezosoic oceanic arcs, namely the Kohistan and
Talkeetna complex. This evolution of the Amalaoulaou oceanic arc and its accretion towards the West African craton belong
to the life and closure of the Pharusian Ocean that eventually led to the formation of the Greater Gondwana supercontinent,
a similar story having occurred on the other side of the Sahara with the Mozambique Ocean. 相似文献
47.
Following the major contributions of Wegener and Argand (Part 1), it was the work of synthesis carried out by R. Staub that
represented the major contribution Alpine geology made with respect to that heritage. The research work of young scientists
(Gagnebin, Juvet, Wavre, Leuba) who had been influenced by Argand was of lesser importance. Ampferer’s ground breaking contribution,
coming along with illuminating graphic illustrations, was all but ignored. Although remaining fairly popular, the theory of
continental drift found itself under the heavy fire of criticism from influential geologists in the USA and in Europe. In
order to test the validity of the idea, C.E. Wegmann suggested linking geological field work with oceanographic research.
He showed that the trajectories of drifting had to be conceived as following the small circles of the sphere. With regard
to Alpine geologists of the time, they were renowned for the high quality of their geological mapping. This remained the very
special activity in which they excelled, but they focused on topics that were becoming narrower and narrower, and increasingly
specialised. The new avenues for research that Holmes and Hess opened up had but little impact on Alpine geologists. In fact,
they apparently remained unaware of a note by Holmes written in German and published in a Swiss journal. On the eve of the
Second World War, the meeting of the Geologische Vereinigung devoted to the origin of the Atlantic Ocean confirmed that continental drift was being seriously challenged, although a few
papers pointed to new developments, e.g. that in Iceland extensional tectonics had been active for the last 5,000 years. Most
Alpine geologists were either highly critical of the theory of plate tectonic when it arrived or expressed serious reservations
towards the idea. Of the exceptions, first Laubscher and then Bernoulli showed very clearly how important the new theory could
be for understanding the evolution of Alpine orogeny. Continental drift and plate tectonics were very much the product of
the creative imagination of human minds. Whereas Wegener used a broad range of confirmed results, plate tectonics sprang out
of the new research being carried out in the domain of oceans. Graphic illustration was one of the favourite vehicles used
to put across these new perspectives. Sometimes their impact remained alive long after their author had withdrawn his backing
for the idea (as was the case for Argand’s “embryonic tectonics”); sometimes, even in spite of their very high standard, they
were just ignored (which was the case for Ampferer). 相似文献
48.
Preface: Proceedings of the 5th International Symposium on Lithographic Limestone and Plattenkalk 总被引:1,自引:0,他引:1
Daniel Marty Jean-Paul Billon-Bruyat Christian A. Meyer Loïc Costeur Basil Thüring 《Swiss Journal of Geoscience》2011,104(1):1-29
Magmatic rocks from the pre-Mesozoic basements of the Sambuco and Maggia nappes have been dated by U–Pb zircon ages with the LA-ICPMS technique. Several magmatic events have been identified in the Sambuco nappe. The mafic banded calc-alkaline suite of Scheggia is dated at 540 Ma, an age comparable to that of mafic rocks in the Austroalpine Silvretta nappe. The Sasso Nero peraluminous augengneiss has an age of 480–470 Ma, like many other “older orthogneisses” in Alpine basement units. It hosts a large proportion of inherited zircons, which were dated around 630 Ma, a Panafrican age indicating the Gondwanan affiliation of the Sambuco basement. The calc-alkaline Matorello pluton yielded ages around 300 Ma, similar to numerous Late Carboniferous intrusions in other basement units of the Lower Penninic (Monte Leone, Antigorio, Verampio) and Helvetic domains (Gotthard and other External Crystalline Massifs). Associated lamprophyric dykes are slightly younger (300–290 Ma), like similar dykes sampled in gneiss blocks included in the sedimentary cover of the underlying Antigorio nappe (290–285 Ma). The Cocco granodiorite and Rüscada leucogranite, both intruding the basement of the neighbouring Maggia nappe, yielded ages of ca. 300–310 Ma, identical within errors to the age of the Matorello pluton. They are significantly older than former age determinations. This age coincidence, coupled with remarkable petrologic similarities between the Cocco and Matorello granodiorites, strongly suggests paleogeographic proximity of the Sambuco and Maggia nappes in Late Carboniferous times. In recent publications these two nappes have been interpreted as belonging to distinct Mesozoic paleogeographic domains: “European” for Sambuco and “Briançonnais” for Maggia, separated by the “Valais” oceanic basin. In this case, the similarity of the Matorello and Cocco intrusions would demonstrate the absence of any significant transcurrent movement between these two continental domains. Alternatively, according to a more traditional view, Sambuco and Maggia might belong to a single large Alpine tectonic unit. 相似文献
49.
RésuménDans certaines régions où les sédiments récents (plio-quaternaires) sont rares ou inutilisables comme enregistreurs de déformations, seule l’analyse morpho-strcturale peut mettre en évidence des indices de néotectonique. Deux types d’objets morphologiques se révèlent particulièrement utiles : les surfaces (d’érosion et de comblement) et le réseau hydrographique. Leur prise en compte et leur analyse s’effectuent essentiellement à partir des cartes topographiques à différentes échelles (de 1/50 000 à 1/500 000).* La démarche est la suivante: 1 – Des traitements appropriés sont développés, mettant en évidence des discontinuités et des anomalies au sein des surfaces enveloppes et du réseau hydrographiques; 2 – Ces discontinuités sont analysées puis interprétées afin de déterminer les causes de leur existence dans le cadre d’un modèle d’évolution du relief qui tient compte de facteurs internes (la lithologie, la structure), et de facteurs externes (le climat, la végétation et les actions humaines); 3 – Des travaux de terrain confirment et précisent les caractéristiques de ces facteurs (nature et quantification de la déformation : âge. amplitude, sens des mouvements). * Les principaux résultats de cette démarche appliquée à l’Kst du Bassin parisien sont les suivants: 1 – Les cuestas orientales du Bassin parisien apparaissent structurées par des accidents NK-SW (prolongement du fossé de Sarre Nahe) et NNW-SSK ( Argonne-Bar-le-Due); 2 – Les discontinuités morpho-structurales sont localisées et caractérisées par des mouvements récents. 相似文献
50.
Megatidal estuaries such as the Seine and the Somme (North-Western France) are rather well delimited and human impacts on them are well understood. Since the middle of the 19th Century, there has been a slow but irreversible degradation of the state of these English Channel estuaries. However, current conservation and restoration strategies tend to freeze habitats in a particular state, their status being defined, most often, through a patrimonial or utilitarian approach. Connectedness between biotopes (sensu habitat+community) has a tendency to be neglected, especially with regard to main ecological gradients, i.e., salinity. In this paper, evaluation methodologies are proposed with the intention of assessing changes to ecosystem functions, under anthropogenic disturbance, controlled or otherwise. The Seine (a heavily industrialised ecosystem) is compared to the Somme (considered here for its pseudo-natural features) in order to discriminate between oceanic processes (siltation and plugging of estuaries) and anthropogenic influences. Preservation and restoration of habitats rely on a robust scientific methodology. The multi-scale approach adopted in the projects presented here relies on sensitive socio-ecological assessment procedures, tools for evaluating ecological quality, and well-built monitoring programmes based upon pertinent indicators. Such managerial tools were used to refine strategies and make them compatible with the sustainable co-development of resources in a European context. This paper demonstrates how scientists were able to acquire and apply knowledge in the field of rehabilitation and restoration. Jointly with managers and policy-makers, they have brought scientific information and socio-economics together in order to answer questions about the restoration of sites or habitats and to anticipate future propositions in the spirit of Integrated Coastal Zone Management (ICZM). 相似文献