Groundwater Origin in Qanats,Chemo-Isotopic,and Hydrogeological Evidence

A systematic study of the chemo-isotopic characteristics and origin of the groundwater was carried out at six major qanats in the hyper-arid Gonabad area, eastern Iran. These qanats as a sustainable groundwater extraction technology have a long history, supporting human life for more than a thousand years in this region. The Gonabad qanats are characterized by outlet electrical conductivity (EC) values of 750 to 3900 µS/cm and HCO₃-Na-Mg and Cl-Na water types. The Gonabad meteoric water line (G_nMWL) was drawn at the local scale as δ²H = 6.32×δ¹⁸O + 8.35 (with R² = 0.90). It has a lower slope and intercept than the global meteoric water line due to different water vapor sources and isotope kinetic fractionation effects during precipitation in this arid region. The altitude effects on isotopic content of precipitation data were derived as δ¹⁸O = (−0.0031 × H_(m.a.s.l))−1.3). The δ²H and δ¹⁸O isotopes signatures demonstrate a meteoric origin of the groundwater of these qanats. The shift of the qanat's water samples from the local meteoric water line (LMWL) in a dry period with higher temperatures is most probably due to evaporation during the infiltration process and water movement in qanat gallery. Based on the isotopic results and mass balance calculations, the qanats are locally recharged from an area between 2000 to 2400 m.a.s.l of nearby carbonate formations and coarse alluvial sediments. The dissolution of evaporate interlayers in Neogene deposits deteriorates the groundwater quality, especially in Baidokht qanat.     

Dinoflagellate and foraminiferal biostratigraphy of the Gurpi Formation (upper Santonian–upper Maastrichtian), Zagros Mountains, Iran

A rich dinoflagellate cyst assemblage has been recovered from an outcrop of the Gurpi Formation, the hydrocarbon source rock in the South Iranian Basin. Key dinoflagellates recorded in the section studied provide a means of correlation with zonation schemes for Australasia and north-west Europe. These include Eucladinium kaikourense, Nelsoniella aceras, Odontochitina spp., Cannosphaeropsis utinensis, Palaeocystodinium denticulatum and Dinogymnium spp. The assemblage points to a late Santonian–late Maastrichtian age for the Gurpi Formation. Dinoflagellate and planktonic foraminiferal evidence indicates the presence of a hiatus spanning the uppermost Maastrichtian to at least the lowermost Danian at the base of a glaucony-rich layer separating the Gurpi Formation from the overlying Pabdeh Formation. Palynofacies and lithofacies profiles suggest that the sediments were deposited in an open, relatively deep marine outer ramp environment belonging to ramp facies 8 and 9.     

Un exemple de volcanisme calco-alcalin de type orogénique mis en place en contexte de rifting (Cambrien de l'oued Rhebar,Meseta occidentale,Maroc)

The Middle Cambrian calc-alkaline Oued Rhebar volcanic complex (western Meseta, Morocco) compares with rocks originated in orogenic contexts. The La/Nb ratios are relatively high (5.2), suggesting a lithospheric mantle origin. The La/Ta ratios, higher than 26, and the negative Nb anomaly indicate a lithospheric source contaminated by the continental crust. These rocks were generated in the Mesetian Mid-Cambrian rift and would have inherited their orogenic signature from the partial melting of a previously metasomatized mantle. To cite this article: H. El Hadi et al., C. R. Geoscience 338 (2006).     

An analytical solution to wave dissipation induced by interacting waves and currents with muddy deposits

Ocean Dynamics - The present study aims to provide a straightforward analytical solution to wave-current-mud interaction by considering the mean shear stress effects in the water layer. A direct...     

Geochemical and geochronological evidence for a Middle Permian oceanic plateau fragment in the Paleo-Tethyan suture zone of NE Iran

The mafic–ultramafic Fariman complex in northeastern Iran has been interpreted as a Paleo-Tethyan ophiolitic fragment with subduction- and plume-related characteristics as well as a basin deposit on an active continental margin. Contributing to this issue, we present geochemical, geochronological, and mineralogical data for transitional and tholeiitic basalts. Thermodynamic modeling suggests picritic parental magmas with 16–21 wt% MgO formed at plume-like mantle potential temperatures of ca. 1460–1600 °C. Rare pyroxene spinifex textures and skeletal to feather-like clinopyroxene attest to crystallization from undercooled magma and high cooling rates. Chromium numbers and TiO₂ concentrations in spinel are similar to those in intraplate basalts. ⁴⁰Ar–³⁹Ar dating of magmatic hornblende yielded a plateau age of 276?±?4 Ma (2σ). Transitional basalt with OIB-like trace element characteristics is the predominant rock-type; less frequent are tholeiitic basalts with mildly LREE depleted patterns and picrites with intermediate trace element characteristics. All samples show MORB-OIB like Pb/Ce, Th/La, and Th/Nb ratios which preclude subduction-modified mantle sources and felsic crustal material. Tholeiitic basalts and related olivine cumulate rocks show MORB-like initial ε_Nd values of +?9.4 to +?6.2 which define a mixing line with the data for the transitional basalts (ε_Nd ca. +?2.6). Initial ¹⁸⁷Os/¹⁸⁸Os ratios of 0.124–0.293 support mixed sources with a high proportion of recycled mafic crust in the transitional basalts. High concentrations of highly siderophile elements are in agreement with the high mantle potential temperatures and inferred high-melting degrees. It is argued that the Fariman complex originated by melting of a mantle plume component as represented by the OIB-like transitional basalt and entrained asthenosphere predominant in the MORB-like tholeiites. Two lines of evidence such as association of the Fariman complex with pelagic to neritic sedimentary rocks and the tectonic position at the boundary of two continental blocks defined by ophiolites and accretionary complexes of different ages suggest formation in an oceanic domain. Thus, we interpret it as a fragment of an oceanic plateau, which escaped subduction and was accreted as exotic block in the Paleo-Tethyan suture zone.     

Island-arc and Active Continental Margin Adakites from the Sabzevar Zone,Iran

Cretaceous to Eocene plutonic and volcanic rocks of the Sabzevar zone have an adakite characteristic with high Sr/Y ratio, depleted HFSE and enriched LILE features. Most of the Sabzevar adakites are high silica adakites with low Ni, Cr and Co contents. LREE/HREE ratio is high, while K₂O content is low to intermediate. Adakites in the Sabzevar zone are exposed in two areas, which are named southern and northern adakites here. The combination of Sr, Nd and Pb isotopic data with major and trace elements indicates that the adakitic rocks are formed by partial melting of the Sabzevar oceanic slab. Nb/Ta content of the samples indicates that the adakitic magmas were generated at different depth in the subduction system. Dy/Yb ratios of adakitic samples indicate positive, negative and roughly flat patterns for different samples, suggesting garnet and amphibole as residual phases during slab-derived adakitic magma formation. Sabzevar adakites emplaced during late to post-kinematic events. Sabzevar oceanic basin demised during a northward subduction by central Iranian micro-continents (CIM) and Eurasia plate convergence.     

The Influence of Shearing Velocity on Shear Behavior of Artificial Joints

In this paper, the effects of shear velocity on the shearing behavior of artificial joints have been studied at different normal stress levels. Here, artificial joints with planar and rough surfaces were prepared with the plaster (simulating soft rock joints) and concrete (medium-hard rock joints) materials. The rough joints had triangular shaped asperities with 10° and 20° inclination angles. Direct shear tests were performed on these joints under various shear velocities in the range of 0.3–30 mm/min. The planar plaster–plaster and planer concrete–concrete joints were sheared at three levels of normal stress under constant normal load boundary condition. Also, the rough plaster–plaster and concrete–concrete joints were sheared at one level of normal stress under constant normal stiffness boundary condition. The results of the shear tests show that the shearing parameters of joints, such as shear strength, shear stiffness and friction angle, are related to the shear velocity. Shear strength of planar and rough plaster–plaster joints were decreased when the shear velocity was increased. Shear strength of concrete joints, except for rough joints with 10° inclination, increased with increasing shear velocity. Regardless of the normal stress level, shear stiffness of both planar plaster–plaster and concrete–concrete joints were decreased when the shear velocity was increased.     

Relative performance of CMIP5 and CMIP6 models in simulating rainfall in Peninsular Malaysia

Theoretical and Applied Climatology - This study evaluated the skills of global climate models (GCMs) of the fifth and sixth Coupled Model Intercomparison Project (CMIP5 and CMIP6) in simulating...     

Geochemistry and geodynamics of the Mawat mafic complex in the Zagros Suture zone, northeast Iraq

The Iraqi Zagros Orogenic Belt includes two separate ophiolite belts, which extend along a northwest-southeast trend near the Iranian border. The outer belt shows ophiolite sequences and originated in the oceanic ridge or supra-subduction zone. The inner belt includes the Mawat complex, which is parallel to the outer belt and is separated by the Biston Avoraman block. The Mawat complex with zoning structures includes sedimentary rocks with mafic interbedded lava and tuff, and thick mafic and ultramafic rocks. This complex does not show a typical ophiolite sequences such as those in Penjween and Bulfat. The Mawat complex shows evidence of dynamic deformation during the Late Cretaceous. Geochemical data suggest that basic rocks have high MgO and are significantly depleted in LREE relative to HREE. In addition they show positive ? _Nd values (+5 to+8) and low 87Sr/86Sr ratios. The occurrence of some OIB type rocks, high Mg basaltic rocks and some intermediate compositions between these two indicate the evolution of the Mawat complex from primary and depleted source mantle. The absence of a typical ophiolite sequence and the presence of good compatibility of the source magma with magma extracted from the mantle plume suggests that a mantle plume from the D″ layer is more consistent as the source of this complex than the oceanic ridge or supra-subduction zone settings. Based on our proposed model the Mawat basin represents an extensional basin formed during the Late Paleozoic to younger along the Arabian passive margin oriented parallel to the Neo-Tethys oceanic ridge or spreading center. The Mawat extensional basin formed without creation of new oceanic basement. During the extension, huge volumes of mafic lava were intruded into this basin. This basin was squeezed between the Arabian Plate and Biston Avoraman block during the Late Cretaceous.