Geochemical and Sr–Nd isotopic constraints on the genesis of the Soheyle-PaKuh granitoid rocks (central Urumieh-Dokhtar magmatic belt,Iran)     

Fatemeh Sarjoughian  Somayeh Javadi  Hossein Azizi  Wenli Ling  Yoshihiro Asahara  David Lentz 《International Geology Review》2020,62(13-14):1769-1795

ABSTRACT

Soheyle-Pakuh granitoid rocks, with a variety of quartz diorite, quartz monzodiorite, granodiorite, tonalite, and granite, have been emplaced into the Tertiary volcanic rocks in the Urumieh-Dokhtar magmatic arc in central Iran. Zircon U–Pb dating yields an age of 39.63 ± 0.93 Ma for the crystallization of this body. Whole-rock compositions show that SiO₂ changes from 52.31 to 65.78 wt.% and Al₂O₃ varies from 15.54 to 18.24 wt.%, as well as high concentrations of large-ion lithophile elements (LILE, e.g. Cs, Rb, Ba, and K) and quite low contents of high field strength elements (HFSE, e.g. Nb, Ti, P), as expected in I-type arc granitoids formed in an active continental margin setting. Initial ratios of ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd exhibit ranges 0.7043–0.7047 and 0.51284 to 0.51287, respectively, with positive εNd_(t) from +4.9 to +5.5 with a young TDM1 age (483–674 Ma); this tracer isotopic data suggesting that the SPG originated from juvenile basaltic crust derived from depleted mantle (~90%) with variable contributions from undepleted mantle and approximately 10% old lower crust, despite diverse processes (e.g. magma mixing and fractional crystallization) during their evolution and emplacement into a local extensional setting within the continental margin arc. The isotopic data are similar to those of other Phanerozoic granitoids of the Central Asian Orogenic Belt and corroborate melting of predominantly mantle-derived juvenile crustal protoliths and indicating extensive addition of new continental crust, during Cambrian-Neoproterozoic time, in the suprasubduction zone beneath the central Urumieh-Dokhtar magmatic arc. Generation of these types of granitoids favours a model whereby rollback and (or) break-off of a subducted slab with subsequent lithospheric extension triggered by mantle upwelling, heat advection, and underplating resulting in melting of the central UDMA mantle-derived juvenile lower continental crust in the Late Eocene.  相似文献   

Spatial distribution,variation and trend of five-day antecedent rainfall in Singapore     

Harianto Rahardjo  Mărgărit-Mircea Nistor  Nurly Gofar  Alfrendo Satyanaga  Qin Xiaosheng  Sabrina Ip Chui Yee 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2020,14(3):177-191

ABSTRACT

This paper presents the spatial distribution, variation and trend of 5-day antecedent rainfall in Singapore based on rainfall data from 22 meteorological stations. The effect of climate was analyzed by dividing the study period into three decades i.e. Decade 1: 1982–1991, Decade 2: 1992–2001 and Decade 3: 2002–2011. Kriging interpolation was used for rainfall mapping. The results show that spatial distribution of 5-day antecedent rainfall does not coincide with that of the annual rainfall. The maximum annual rainfall occurred in the northwestern side of Singapore. On the other hand, the maximum 5-day antecedent rainfall occurred in the north and northeastern sides. The results of this study suggest that the climate change has increased the amount of 5-day antecedent rainfall quite significantly, i.e. from 420.5 (1987) to 592.9 mm (2006), thus affecting the vulnerability of the area with respect to rainfall-induced slope failure. The analyses also showed that most of slope failures were located in the north and northeast of Singapore between December and earlier March. More slope failures were observed in Decade 3 as compared to Decades 1 and 2. In other words, the analysis confirmed that 5-day antecedent rainfall had affected the slope stability in Singapore.  相似文献   

Landslide phenomena in the area of Pomarico (Basilicata–Italy): methods for modelling and monitoring     

F Bozzano  C Cherubini  M Floris  M Lupo  F Paccapelo 《Physics and Chemistry of the Earth》2002,27(36):1601-1607

This paper takes into consideration landslide phenomena in the clayey slopes facing the built-up area of Pomarico which is situated in the southern part of the “Fossa Bradanica”, in Basilicata (Italy). Based on the great number of geologic, geomorphologic and historic informations a geotechnical model of the slope was built. Particular attention has been paid to define the geotechnical parameters of the soil and which mechanical models are to be used. The studies point out a correlation between the water level in the detritus cover and the stability condition of the slope showing that phenomena at first located at the foot of the slope spread quickly towards its summit as the piezometric height increases.  相似文献   

Les rhyolites hyperalcalines (pantellérites) du lac Tchad. Composition et signification tectonomagmatiqueThe peralkaline rhyolites (pantellerites) of the Lake Chad. Composition and tectonomagmatic significance     

Jean-Paul Vicat  André Pouclet  Yves Bellion  Jean-Claude Doumnang 《Comptes Rendus Geoscience》2002,334(12):885-891

Remnants of rhyolite lava-dome and of alkaline microgranite extrusions emerge, as inselbergs, in the alluvial plain, south of Lake Chad. The peralkaline, arfvedsonite- and acmite-bearing rhyolites are determined as pantellerites. They can be related to a tectonomagmatic stage, dated of the Late Cretaceous, of the western central Africa rift system. They may constitute the NNE extension of a N50° to 30° elongated succession of small alkaline complexes, from the Gulf of Guinea to the North-Cameroon, which initiated the magmatic activity of the Cameroon Line. To cite this article: J.-P. Vicat et al., C. R. Geoscience 334 (2002) 885–891.  相似文献   

La vague de chaleur de l'été 2003 et sa prévision saisonnière     

Jean-Claude André  Michel Déqué  Philippe Rogel  Serge Planton 《Comptes Rendus Geoscience》2004,336(6):491-503

The main features of the heat wave that has affected western Europe during the summer 2003 are first recalled, with particular concern to analogies and differences with previous warm-summer episodes. The skills of the various operational and pre-operational seasonal forecasting models in use at that time are evaluated. None of them has been able to consistently forecast the heat wave three month in advance. The meteorological and climatic situation prevailing during spring 2003 is then analysed. A strong sea-surface-temperature (SST) anomaly is found to have developed over North Atlantic a few months before the heat wave. The particular mechanism at work to explain the occurrence of the heat wave is not a ‘simple downwind influence’ of the SST anomaly. It very likely involves complex ocean–atmosphere interaction phenomena of a kind that is not properly taken into account in today's seasonal forecasting models. To cite this article: J.-C. André et al., C. R. Geoscience 336 (2004).  相似文献   

Diachronisme des bassins turbiditiques d'avant-pays méso/néocrétacés du pays de Sault (Aude,Pyrénées françaises)     

Marie-José Fondecave-Wallez  Bernard Peybernès 《Comptes Rendus Geoscience》2004,336(15):1391-1400

The cartographic, sedimentological and micropalaeontological analysis of remnants of Middle–Upper Cretaceous turbiditic basins from the ‘Pays de Sault’ (Aude, French Pyrenees) shows their diachronism (interpreted on a wider scale) and their sequence diversity. The ‘Gesse breccias’ are regarded as the proximal deposits of a Turonian narrow foreland basin, principally supplied by the erosion of the Jurassic–Lower Cretaceous cover of the High Primary Range to the south, induced by a strike-slip and overthrusting faulting within the en-échelon North-Pyrenean Fault Zone. More to the north, the North-Pyrenean ‘Axat Basin’ consists of two successive backstepping turbiditic wedges, respectively corresponding to an Upper Albian distal flysch and to a Middle–Upper Cenomanian more proximal flysch, all the series unconformably overlying structures that were folded then eroded before the Upper Albian. The previous concept of carbonate olistoliths included within the Axat Cenomanian flysch is also refuted: these large-size blocks are now interpreted as belonging to a tectonic slice destroyed and partly collapsed on the southern slope of the Rebenty Valley during the Quaternary. To cite this article: M.-J. Fondecave-Wallez, B. Peybernès, C. R. Geoscience 336 (2004).  相似文献   

Failles normales Paléocène à Lutétien en zone sud-pyrénéenne (Aragon,Espagne) et flexuration de la plaque ibérique     

Yves Hervouët  Nicolas Espurt  Damien Dhont 《Comptes Rendus Geoscience》2005,337(3):385-392

Close to the South Pyrenean thrust front, synsedimentary normal faults develop in the ‘Garumnian’ continental deposits (Maastrichtian to Palaeocene) and in the carbonate platform during the Lutetian. During the Lutetian, this deformation is accompanied by a change in the sedimentation characterized by the deposit of two series of laminated limestones associated to monogenetic breccias. These normal faults would have formed at the bending of the Iberian plate subducting under Europe. They may also be considered as the starting point for the megaturbidites that deposited further north in the Eocene turbiditic basin. To cite this article: Y. Hervouët et al., C. R. Geoscience 337 (2005).  相似文献   

Effets de la vitesse d'écoulement sur le transport et la cinétique de dépôt de particules en suspension en milieu poreux saturé     

Ahmed Benamar  HuaQing Wang  Nasre-dine Ahfir  Abdellah Alem  Nicolas Masséi  Jean-Paul Dupont 《Comptes Rendus Geoscience》2005,337(5):497-504

We study in this paper the transport and deposition of suspended particles in saturated porous media. Some chromatographic short-pulse tests were performed in a laboratory column with a tracer and two types of suspended particles. A mathematical model was used to determine the hydrodispersive parameters and deposition rates from the breakthrough curves. The results show that the fitted parameters obtained vary with the flow rate and the characteristics of the suspended particles. We also observe, at high flow rates, that particles have a migration velocity higher than that of the conservative tracer. To cite this article: A. Benamar et al., C. R. Geoscience 337 (2005).  相似文献   

Relation entre évolution de la matière organique et caractéristiques géostructurales : exemple du bassin yprésien en Tunisie centro-septentrionale     

Adel Arfaoui  Mabrouk Montacer 《Comptes Rendus Geoscience》2006,338(10):683-692

The geochemical analysis of the organic-rich facies from the Ypresian basin in central–northern Tunisia shows that the organic matter is marine originated (type II) and displays a low thermal maturity level in outcropping samples. This study proves that the distribution, conservation and, therefore, the composition of the organic matter have been controlled by the dynamic of the Ypresian basin. The Ypresian period corresponds to an anoxic event, which led to the accumulation and preservation of good quantities of organic matter derived from a high primary production. To cite this article: A. Arfaoui, M. Montacer, C. R. Geoscience 338 (2006).  相似文献   

北澜沧江缝合带白济汛堆晶岩的初步研究     

魏君奇  王晓地 《华南地质与矿产》2006,(3):37-40

北澜沧江缝合带白济汛堆晶岩由吉岔镁铁-超镁铁岩和俄咱辉长岩组成.吉岔镁铁-超镁铁岩由蛇纹岩-辉长岩-斜长花岗岩以构造岩片的形式组合在一起,形成于澜沧江洋盆扩张期,是澜沧江洋的洋壳残片,属蛇绿岩的组成单元.俄咱辉长岩则不属于澜沧江蛇绿岩带的组成单元,岩体具就地分异现象,边缘相中见辉长岩-闪长岩-斜长花岗岩堆晶系列,是澜沧江洋盆闭合、陆-陆碰撞后(燕山晚期),在板内拉张环境下侵位的基性岩体.  相似文献