Geochemical constraints on the provenance of Oligocene–Miocene siliciclastic deposits (Zivah Formation) of NW Iran: implications for the tectonic evolution of the Caucasus     

Mahdi Jafarzadeh  Reza Moussavi Harami  Abdolhossein Amini  Asadollah Mahboubi  Farzin Farzaneh 《Arabian Journal of Geosciences》2014,7(10):4245-4263

In this study, the whole-rock geochemistry of 35 Oligocene–Miocene sandstone and shale samples from the Zivah Formation, Moghan area (NW Iran) were collected and analyzed for evaluation of their provenance, tectonic setting and the intensity of paleo-weathering. Low to moderate values of the chemical index of alteration (mean CIA?=?53/68 for sandstones/shales) and relatively high values of index of compositional variability (mean ICV?=?1.23/1.08 for sandstones/shales) suggest weak chemical weathering and an immature source. These results support for the semi-arid and semi-humid paleoclimate conditions in the source area. The geochemistry results reveal that the sediments were deposited in a basin related to the island arc and active continental margin tectonic settings, probably indicating the time of initial collision between Arabia and Eurasia. The enrichment of Cr, Ni and V in the sandstone and shales are consistent with mafic input from the source area. However, La/Th vs. Hf and La/Sc vs. Co/Th plots reveal mixed source of felsic and intermediate volcanic rocks. The data indicate that the sediments most likely originated from a mixture of mafic, intermediate and felsic igneous source areas, possibly as the erosional products of localized topography of the Talysh and the Lesser Caucasus mountains (south to southwest), created by compression in the Moghan region during the syn-collisional development of the Caucasus.  相似文献   

Discontinuous Modelling of Stratum Cave-in in a Longwall Coal Mine in the Arctic Area   总被引：1，自引：1，他引：0  

Mahdi Shabanimashcool  Lanru Jing  Charlie C. Li 《Geotechnical and Geological Engineering》2014,32(5):1239-1252

This paper presents a discontinuous numerical approach for studying roof cave-in mechanisms and obtaining the required support capacity of longwall shields in a case study site, the Svea Nord coal mine in Svalbard. The block size in the roof strata and the mechanical parameters of the discontinuities for the numerical model were obtained through back-calculations. The back-calculations were conducted with a statistical method of design of experiment. Numerical simulations revealed that voussoir jointed beams are formed before the first cave-in occurs. The maximum deflection of a roof stratum in the study site prior to the first cave-in is about 70 % of the stratum thickness. The maximum span of the roof strata prior to the first cave-in depends upon the in situ horizontal stress state. The roof beams have a large stable span when they are subjected to high horizontal stress; but horizontal stress would increase the possibility of rock crushing in deflected roof beams. The simulations and field measurements show no periodic weighting on the longwall shields in the study site. Stiff and strong roof beams would result in large first and periodic cave-in distances. As a consequence of having large cave-in distances, the longwall shields must have high load capacity, which can be calculated by the presented numerical approach.  相似文献   

Analytical methods to estimate the hydraulic conductivity of jointed rocks     

Zoorabadi  Mahdi  Saydam  Serkan  Timms  Wendy  Hebblewhite  Bruce 《Hydrogeology Journal》2022,30(1):111-119

Hydrogeology Journal - The hydraulic conductivity of jointed rocks is one of the main input parameters to predict water inflow to engineering structures that are located in the jointed rocks....  相似文献   

Battered minipile response to low-frequency cyclic lateral loading in very dense sand     

Mondal  Sanchari  Disfani  Mahdi M. 《Acta Geotechnica》2022,17(9):4033-4050

Acta Geotechnica - This experimental study investigates the response of vertical and battered minipiles to two-way symmetrical low-frequency (0.1 Hz) cyclic lateral loading. Laboratory...  相似文献   

Structural Control on the Salmas Geothermal Region, Northwest Iran, from Fractal Analysis and Paleostress Data     

Mahdi BEHYARI  Javad NOURALIEE  Davar EBRAHIMI 《《地质学报》英文版》2018,92(5):1728-1738

The Salmas geothermal field is located in NW Iran. Subduction of Neo-Tethys oceanic crust beneath the Iranian microcontinent caused to propagation of the magmatic-Arc. Fractures and faults in the convergent zone have created path-ways for the circulation of geothermal fluid. Fracture concentration in the Salmas geothermal field has been characterized using of the fractal method and creation of a fracture density map that shows the highest concentration in the central part of the study area. The permeability of fractures has been evaluated by analyzing their orientation in respect to the paleostress axes. Also, the fractal analyzing result indicates the maximum fractal dimension (1.96) is around the thermal spring outlet. Paleostress analyzing revealed that in the central part of the study area, σ1 axes orientation is S90°W/10° and the σ2 dip is near to the vertical in this stress field, where strike slip faults can be propagated. In the SE part near the recharge of the thermal springs, the σ3 plunge increases to 70? and σ1 orientation is N15°E/20°, in this local tectonic regime thrust fault developed. Fractures have an important role in the circulation of fluid and the fractal dimension increases near the thermal springs in the Salmas geothermal field. Regarding the paleostress data fracture with N-S direction such as the F1 fault zone (parallel to the σ1 axes), a suitable pathway for deep circulation of geothermal fluid flow has been created.  相似文献   

Development of dangerous geological processes in the Hankaisky Region of Primorskiy Krai （Russian Far East）     

Tafiana V. Selivanova 《东北亚地学研究》2006,9(2):176-179

Hankaisky Region is the most densely populated and economic developed part of the Primorskiy Krai.It is promoting development of dangerous geological processes there.In the article the reasons of formation and intensive development in Hankaisky Region of the following dangerous geological processes lateral,winder and ground erosive,sill,floods,taluses,bogging,slope wash,karts,rebound of ground are considered.  相似文献   

Gold and tin of fluid-magmatic systems:causes of combination-separation of concentration elements     

I.I. Fatyanov  V.G. Khomich 《东北亚地学研究》2009,(3)

The aim of the investigation is to reveal possible causes of isolation and co-occurrence of the economically significant concentrations of gold and tin. Comparative analysis of the different-rank factors that influenced migration and concentration of these elements show that different geochemical properties of Au and Sn are responsible for isolation of their big concentrations giving rise to independent metallogenic provinces, zones, and ore nodes. These differences resulted in individualization of the elem...  相似文献   

Guest editorial to the special issue modelling of river hazards     

Tew-Fik Mahdi  Samir Hamdi 《Natural Hazards》2010,55(1):1

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Unsupported advance length in tunnels constructed using New Austrian Tunnelling Method and ground surface settlement     

Ali Nemati Hayati  Mohammad Mehdi Ahmadi  Mahdi Hajjar  Aliakbar Kashighandi 《国际地质力学数值与分析法杂志》2013,37(14):2170-2185

Tunnels constructed using New Austrian Tunnelling Method (NATM) are always based on certain round (unsupported) advance lengths, after which, the temporary lining is placed. The settlement of the ground surface resulting from such construction is of high significance in design and practice. The existing data in this respect, however, is scarce. It is the aim of this paper to propose a semi‐analytical procedure based on three‐dimensional finite element analyses to predict the maximum surface settlement of the ground in NATM tunnels under different combinations of tunnel diameter, overburden depth, round length and soil and lining properties. The comparison of the results with three case histories of real tunnels reveals reasonable accuracy of the present solution. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Study of pore pressure variation during liquefaction using two constitutive models for sand   总被引：1，自引：0，他引：1  

Mahdi Taiebat  Hadi Shahir  Ali Pak 《Soil Dynamics and Earthquake Engineering》2007,27(1):60-72

Numerical analyses of liquefiable sand are presented in this paper. Liquefaction phenomenon is an undrained response of saturated sandy soils when they are subjected to static or dynamic loads. A fully coupled dynamic computer code is developed to predict the liquefaction potential of a saturated sandy layer. Coupled dynamic field equations of extended Biot's theory with u–P formulation are used to determine the responses of pore fluid and soil skeleton. Generalized Newmark method is employed for integration in time. The soil behavior is modelled by two constitutive models; a critical state two-surface plasticity model, and a densification model. A class ‘B’ analysis of a centrifuge experiment is performed to simulate the dynamic response of level ground sites. The results of the numerical analyses demonstrate the capability of the critical sate two-surface plasticity model in producing pore pressures that are consistent with observations of the behavior of liquefiable sand in the centrifuge test.  相似文献