排序方式： 共有6条查询结果，搜索用时 78 毫秒
1
1.
Amel Derridj Khadidja Ouzegane Jean-Robert Kienast Djelloul Belhaï 《Journal of African Earth Sciences》2003,37(3-4):257
Garnet pyroxenite from high pressure granulite facies occurs with different mineral assemblages which involve garnet, clinopyroxene, orthopyroxene, plagioclase, amphibole and quartz with spinel developing as symplectite with orthopyroxene and plagioclase in large cracks. Three successive parageneses have been identified. The primary assemblage is characterised by the presence of quartz. The second assemblage involves orthopyroxene–plagioclase–hornblende symplectite, and the third assemblage is characterised by the development of spinel in symplectites with orthopyroxene and plagioclase. Using THERMOCALC (V2.7), a quantitative pseudosection in the system CaO–FeO–MgO–Al2O3–SiO2–H2O has been calculated. The assemblage involving quartz developed at high pressure, while the assemblage involving spinel developed at lower pressure. The peak of metamorphism in Tin Begane was calculated at 860 °C and 13.5 kb with aH2O=0.2. These conditions are followed by a decrease of pressure down to 4.8 kb. 相似文献
2.
RésuméLes formations méso-cénozoïques du Djurdjura (Algérie), élément important de la « Dorsale kabyle » de la chaîne des Maghrébides, sont classiquement subdivisées en trois « dorsales » : interne, médiane et externe. Cette subdivision calque, selon ses auteurs, des zones paléogéographiques s’approfondissant du Nord au Sud. Elle est basée sur la présence, l’absence et les variations d’épaisseur des formations allant du Paléozoïque à l’Éocène, considérées comme originelles. Une réinterprétation des levers géologiques existants ainsi que nos nouvelles observations structurales indiquent que les ablations, réductions et épaississements sont causés par des zones de cisaillement verticales. Ces couloirs de cisaillement (ductile à fragile) découpent les formations homogènes de la couverture de plateforme méso-cénozoïque et d’une partie de son substratum en lentilles verticales. Les cisaillements, leurs connections et la nature des déformations qu’ils causent permettent de distinguer la profondeur structurale et les différentes branches qui s’en détachent, délimitant ainsi des unités et sousunités tectoniques. Les unités tectoniques, souvent de forme lenticulaire très effilée en profondeur et vers le NE, s’épaississent vers le haut et le SW, constituant parfois des anticlinaux de rampe décro-chevauchante. Cette hétérogénéité semble être en rapport avec, d’une part, la déformation hétérogène transpressive et, d’autre part la présence de corps carbonatés basiques et éocènes découpés en amandes rigides moulées par les zones de fluage qui, par contre, se localisent essentiellement dans les niveaux marno-calcaires sénono-éocènes. L’ensemble des ces unités forme une structure globale de duplex transpressif en fleur acquise à la suite de la tectonique transcurrente fini-luté-tienne. Cette structure en fleur est le résultat de la lenticularisation d’une couverture méso-cénozoïque déformée dans une zone de collage transpressive dextre entre le cristallin kabyle interne et le domaine tellien externe de la chaîne des Maghrébides. Cette zone transcurrente se localise dans une aire de croûte probablement amincie, longeant le nord de la marge paléoafricaine, qui correspondrait à l’aire de sédimentation des flyschs crétacés. 相似文献
3.
AbstractThe first objective of this paper is to analyse the trends and change points in the hydroclimatic time series of five representative sub-catchments of the Macta basin, which lies in western Algeria. The second objective is to quantify the role of climate on the trends observed in annual flow time series. This is achieved using hydrological modelling at the multi-annual time step using the Schreiber formulation. The results showed no significant trends on annual rainfall in the 1975–2005 period, a significant increase of temperature and different flow responses to the latter, depending on the catchment considered. Two out of five catchments considered presented a significant flow decrease in the 1975–2005 period with a change point at the beginning of the 1990s. Modelling results suggest that the increase of air temperature is not the sole factor explaining the decrease of annual flow time series in these two catchments. 相似文献
4.
Imene Meriem Benbakhti Said Maouche Djelloul Belhai Assia Harbi Jean-François Ritz Ghilles Rabai Ahmed Rezouk Fawzi Doumaz 《Journal of Seismology》2018,22(6):1549-1561
In this work, we reappraise the seismogenic potential of the geologic structures in the western Tell Atlas of Algeria, considered active host to moderate to low magnitude earthquakes. The direct identification of active faults is generally a difficult task in northern Algeria. The active tectonics in the Oran Plio-Quaternary age basin (Northwestern Algeria) is analyzed and characterized through a morpho-structural study combining topographic, geomorphologic, geological, and neotectonic data. Folds and fault scarps affecting Quaternary deposits show that the region is affected by compressional deformation still active nowadays, as shown by the recorded seismic activity. Our new observations enable a better understanding of the present seismotectonic context of the Oran region, particularly with regard to the magnitude and source of the 1790 Oran damaging event. The obtained result helps to shed some light on the elusive active tectonics characterizing this coastal area, and to assess regional seismic hazard, particularly in coastal zones where large seismogenic areas straddle the onshore–offshore zones. 相似文献
5.
The fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV), April 9–12, 2017, Algiers (Algeria) 
下载免费PDF全文
下载免费PDF全文 D. Belhaï H. Chennaoui‐Aoudjehane D. Baratoux L. Ferrière A. Lamali R. Sahoui P. Lambert A. Ayadi 《Meteoritics & planetary science》2017,52(9):2067-2071
We present a report about the fourth Arab Impact Cratering and Astrogeology Conference (AICAC IV) that took place in Algiers at the USTHB (Université des Sciences et Technologie Houari Boumedienne, Algiers, Algeria) in the presence of the presidents of the USTHB and Boumerdès Universities, the Director of CRAAG (Centre de Recherche en Astronomie, Astrophysique et Géophysique), and the General Director of the National Administration for Scientific Research (NASR/DGRSDT). This series of conferences aims to promote research interest for impact cratering in the Arab world and beyond, including for instance in African countries. In spite of persistently restraining travel measures to Algeria, the fourth edition held in Algiers was marked by continuous international participation, with participants from seven different countries. This conference focused on presentations of scientific results in the research fields related to planetology, meteorites, and impact craters. In particular, the Algerian impact structures were under the spotlights during both oral and poster sessions. During this conference, the presence of freshly graduated Ph.D. students and new Ph.D. projects related to impact cratering or meteoritic science was a positive sign for the consolidation of research groups in this domain in the Arab world and Africa. Therefore, international cooperation or external support and funding are still needed to ensure the development of this scientific discipline in this part of the world. 相似文献
6.
A shallow moderate (M
s=5.7) but damaging earthquake shook theregion of Beni-Ourtilane located about 50 km NW of Setif and 390 kmNE of Algiers (Central Eastern Algeria). The main shock caused the deathof 2 peoples, injured 50 and caused sustainable damage to about 3000housing units. The main shock was preceded by 2 foreshocks and followedby many aftershocks which lasted for many days. Analysis of historicalseismicity including the localisation of epicenters, the trend of isoseismalmaps of some historical events, the localisation of the November 10, 2000main shock (M
s=5.7) and the November 16, 2000 aftershock(M
s=4.5) as well as the shape of the area of maximum intensity ofthe November 10, 2000 earthquake suggest that the Tachaouaft fault of20 km of length is the activated geological structure. Although, there isno clear surface breaks associated with this earthquake, the localisation ofgeological disorders, such as ground fissures, during the Beni-Ourtilaneearthquake, which are remarkably located near the fault, may have atectonic meaning. Geomorphological analysis through Digital ElevationModels (DEMs) allowed us to identify a clear fault scarp related likely tostrong earthquakes occurred in the past. Among geomorphologicalevidences of this active fault there are the uplift and tilt of alluvial terraceson the hanging wall and the diversion of the drainage pattern. Based onthe quality of constructions and field observations an intensity I
0 = VII (MSK scale) is attributed to the epicentral area,which is striking NE-SW in agreement with the focal mechanism solutionand the seismotectonic observations. In the other hand the amount ofdamage is due rather to the bad quality of constructions than to theseverity of ground motion. The Tachaouaft fault with the Kherrata fault isthe main source of seismic hazard in the Babors region. 相似文献
1