Detrital zircon U–Pb ages along the Yarlung-Tsangpo suture zone, Tibet: Implications for oblique convergence and collision between India and Asia

Age-dating of detrital zircons from 22 samples collected along, and adjacent to, the Yarlung-Tsangpo suture zone, southern Tibet provides distinctive age-spectra that characterize important tectonostratigraphic units. Comparisons with data from Nepal, northern India and the Lhasa and Qiangtang terranes of central Tibet constrain possible sources of sediment, and the history of tectonic interactions.Sedimentary rocks in the Cretaceous–Paleogene Xigaze terrane exhibit strong Mesozoic detrital zircon peaks (120 and 170 Ma) together with considerable older inheritance in conglomeratic units. This forearc basin succession developed in association with a continental volcanic arc hinterland in response to Neotethyan subduction under the southern edge of the Eurasia. Conspicuous sediment/source hinterland mismatches suggest that plate convergence along this continental margin was oblique during the Late Cretaceous. The forearc region may have been translated > 500 km dextrally from an original location nearer to Myanmar.Tethyan Himalayan sediments on the other side of the Yarlung-Tsangpo suture zone reveal similar older inheritance and although Cretaceous sediments formed 1000s of km and across at least one plate boundary from those in the Xigaze terrane they too contain an appreciable mid-Early Cretaceous (123 Ma) component. In this case it is attributed to volcanism associated with Gondwana breakup.Sedimentary overlap assemblages reveal interactions between colliding terranes. Paleocene Liuqu conglomerates contain a cryptic record of Late Jurassic and Cretaceous rock units that appear to have foundered during a Paleocene collision event prior the main India–Asia collision. Detrital zircons as young as 37 Ma from the upper Oligocene post-collisional Gangrinboche conglomerates indicate that subduction-related convergent margin magmatism continued through until at least Middle and probably Late Eocene along the southern margin of Eurasia (Lhasa terrane).Although the ages of detrital zircons in some units appear compatible with more than one potential source with care other geological relationships can be used to further constrain some linkages and eliminate others. The results document various ocean closure and collision events and when combined with other geological information this new dataset permits a more refined understanding of the time–space evolution of the Cenozoic India–Asia collision system.     

A Metamorphic Core Complex Model for the Host of Uranium Mineralization in the Khoshoumi Mountain,Central Iran

A metamorphic core complex model is proposed for Khoshoumi Mountain uranium mineralization located in the Bafq–Saghand metallogenic zone of central Iran. Uranium mineralization occurred in the Chapedoni metamorphic complex. Detailed structural analysis of the complex leads to the interpretation that the mineralization is spatially concentrated in a low angle shear zone of mylonitized migmatite, the lower ductile part of the Chapedoni metamorphic complex. The shear zone that has top to the NE sense of shear in the northeastern and southeastern parts of the mountain and top to the WNW sense of shear in the southwestern part is a detachment zone to the Chapedoni Metamorphic Core Complex (CMCC). The Eocene granite is the plutonic core to the CMCC. The shear zone is cut by several NE‐trending left‐lateral strike‐slip faults. This later faulting is interpreted to account for the significant enrichment of uranium in the southern part of the mountain. The bimodal distribution of radiometric data gathered from exploratory drill holes in this part of the mountain constrains this interpretation. That is, the lower value is from the shear zone across the area but the higher value is from the places that the shear zone is cut by the transverse faults.     

Helium measurements of pore fluids obtained from the San Andreas Fault Observatory at Depth (SAFOD, USA) drill cores

⁴He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4?C6 times on each sample, and indicate a bulk ⁴He diffusion coefficient of 3.5?±?1.3?×?10^?C8 cm²?s^?C1 at 21°C, compared to previously published diffusion coefficients of 1.2?×?10^?C18 cm²?s^?C1 (21°C) to 3.0?×?10^?C15 cm²?s^?C1 (150°C) in the sands and clays. Correcting the diffusion coefficient of ⁴He_water for matrix porosity (??3%) and tortuosity (??6?C13) produces effective diffusion coefficients of 1?×?10^?C8 cm^2?s^?C1 (21°C) and 1?×?10^?C7 (120°C), effectively isolating pore fluid ⁴He from the ⁴He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8?±?0.4% (SD, n?=?4) and mudstones 3.1?±?0.8% (SD, n?=?4).     

Submarine and coastal karstic groundwater discharges along the southwestern Mediterranean coast of Turkey

A 120 km-long part of the southwestern coast of Turkey, with well-developed karst terrain in contact with the sea, has been investigated by systematic diving surveys to determine the submarine groundwater discharges (SGDs). The physical, chemical and isotopic data have been used to determine the rate of the fresh groundwater end member (FEM) and its temporal dynamics. About 150 SGDs have been detected by diving surveys employed mostly up to a depth of 30 m below sea level (bsl). Among those, 15 SGDs are in the form of coastal or submarine caves with entrances ranging between sea surface and 40 m bsl. The FEM contribution in SGDs ranges from a few percent to more than 80%. Stable isotope data suggest a range of mean recharge area elevations extending from the coast to more than 1,000 m inland. In many of the SGDs, the FEMs are characterized by tritium-based residence times ranging from recent to several decades. Hypothetical geochemical calculations of mixing between freshwater and seawater end members reveal that more than 45% of freshwater contribution is required for karst development in the SGDs. Models suggest a threshold pH of 7.6 or lower for the carbonate rock dissolution.     

Numerical investigation of undrained cavity expansion in fine-grained soils

Based on the spherical cavity expansion (SCE) problem, Cudmani and Osinov (Can Geotech J 38:622–638, 2001), Osinov and Cudmani (Int J Numer Anal Method Geomech 25:473–495, 2001) developed a semi-empirical method of interpretation of CPT for coarse-grained soils (sand, gravel) using a hypoplastic constitutive model. Using a material-independent shape factor, the cone penetration resistance was related to the limit pressure required to expand a spherical cavity. The shape factor was observed to be a function of the soil state only, in particular the pressure-dependent relative density. This paper presents an analogous interpretation technique for CPT in fine-grained soils using the shape factor concept, Cavity Expansion approach, and a hypoplastic constitutive model. Relations for the shape factor and the limit pressure have been proposed based on the parameters affecting these quantities. A validation of the proposed interpretation technique with experimental results has also been performed.     

Costs related to drowning and near drowning in northern Iran (Guilan province)

In Iran and many other low- and middle-income countries, few studies have been carried out in order to assess which cost analysis methods should be undertaken at the household and community level in relation to incidences of drowning. In this study, we have attempted to develop a model for estimating the impact of the economic burden that drowning and near drowning events incur for victims’ families in the Guilan province in the north of Iran by using an incidence approach. During the financial year of March 2007 to 2008, the following cost-related aspects of drowning episodes were evaluated: (note: main cost elements were income adjusted by family and years) medical costs, productivity loss costs and death costs. A total of 137 drowning fatalities and 104 near drowning incidents were recorded. Males in the age span of 10-29 years constitute a majority of the epidemiology and economy data. When the number of variables included in cost analysis was expanded, the estimated burden of economic duress increased dramatically; however, drowning cost for one drowned victim was equivalent to 17 times the country’s gross domestic product(GDP) per capital. Identification of injured person-based costs in this study will enable development of more effective prevention programs and provide indicators of other costs related to drowning episodes such as property damage and the impact of these accidents on community services and the public health care system.     

Integrated coastal management plan in free trade zones, a case study

Free Trade Zones (FTZs) around the world offer special advantages to investors and facilitate import/export of goods in order to boost the regional economy. Integrated coastal management in these areas faces special challenges in addition to what ordinary ICZMs usually encounter. For a successful ICZM plan, the very strong business orientation in FTZs has to be taken into account, while other important aspects such as environmental, social, and cultural issues should not be overlooked. The problem becomes more difficult where the free zone is situated in sensitive and valuable environmental circumstances.Kish Island, a free trade zone in the Persian Gulf region, has recently been the focus of a major ICZM study. In order to address the different needs of various stakeholders in the island, four strategic management plans are prepared. The investigations carried out in the course of this study indicated that the required management plans for this free trade zone should be provided with a spatial-plan-oriented approach, otherwise the integration can hardly be achieved and implemented.This article describes Kish FTZ characteristics and problems that required ICZM initiatives, the methodology for ICZM study, the preparation and implementation of strategic management plans considering the free zone obligations, and the need for a spatial umbrella plan to facilitate the integration among different plans in the implementation process.     

Effect of environmental factors on photodegradation of polycyclic aromatic hydrocarbons (PAHs) in the water-soluble fraction of Kuwait crude oil in seawater

Photodegradation of PAHs in the water-soluble fraction of Kuwait crude oil in seawater was investigated under various environmental factors (temperature, light intensity, oxygen levels and presence of a sensitizer) in laboratory conditions. All factors investigated had significant effect on the degradation rates of PAHs. At 15 °C almost all PAHs optimally degraded at an oxygen level of 4 ppm. For lower molecular weight PAHs a light intensity of 500 W/m² in the presence of the sensitizer worked well. Higher molecular weight PAHs degraded at faster rates at a light intensity 750 W/m². At 30 °C, most of the PAHs degraded optimally at an oxygen level of 0 ppm and light intensity of 500 or 750 W/m² in presence of the sensitizer. At 40 °C, most of PAHs degraded optimally at low oxygen concentrations (0 and 4 ppm) and a light intensity of 500 W/m² in the presence of the sensitizer. Linear regression indicated that for most of the compounds, light intensity had the greatest effect on degradation rates.     

Appraisal of relative tectonic activity along the Kazerun Fault Zone,Zagros Mountains,Iran: insight from spatial analysis of geomorphic indices

This paper investigates the impact of active tectonics on the geomorphic processes and landscape evolution along the Kazerun Fault Zone (KFZ) in the Zagros Mountains of Iran using spatial analysis of geomorphic indices. We document how topography and morphology are influenced by active tectonic deformation. The Zagros fold–thrust belt is an area of active crustal shortening where northwest–southeast oriented fault‐related folds become younger from north to south and from southeast to northwest. This temporal and spatial evolution of the belt was tested using geomorphic indices of active tectonics that include mountain front sinuosity index (Smf), the valley width/height ratio (Vf), drainage basin asymmetry factor, hypsometric integral, drainage basin shape ratio and mean axial slope of the channel. Change in the geomorphic indices is the result of active fold growth and change in the uplift rate. Decreasing Smf and Vf values from north (Smf = 2.01; Vf = 0.5) to south (Smf = 1.12; Vf = 0.2) and from southeast (Smf = 1.84; Vf = 0.8) to northwest (Smf = 1.54; Vf = 0.1) points to a migration of the active crustal shortening towards W–SW. The combined geomorphic (field evidences) and morphometric data (quantitative analysis of geomorphic indices) provide evidence of relative variation in the tectonic activity along the Kazerun Fault Zone and related landforms. The utilization of geomorphic parameters with comparison to the field observations exhibits change in relative tectonic activities mostly corresponding to the change in mechanism of the prominent fault zones in the study area. Copyright © 2014 John Wiley & Sons, Ltd.     

Helical Eruptive Prominence Associated with a Pair of Overlapping CMEs on 21 April 2001

The eruption of limb prominence on 21 April 2001 associated with two coronal mass ejections (CMEs) is investigated. Hα images reveal two large-scale eruptions (a prominence body and a southern foot-point arch), both showing helical internal structure. These two eruptions are found to be spatially and temporally associated with the corresponding CMEs. The kinematics and the study of geometrical parameters of the prominence show that the eruption was quite impulsive (with peak acceleration ≈470 m s⁻²) and has taken place for relatively low pitch angle of helical threads, not exceeding tan θ≈1.2. The stability criteria of the prominence are revisited in the light of the model of Vršnak (1990, Solar Phys. 129, 295) and the analysis shows that the eruption violates the instability criteria of that model. Finally, the energy stored in the prominence circuit and the energies (kinetic, potential, and magnetic) of the associated CMEs are estimated and it is found that there was enough energy stored in the prominence to drive the two CMEs. S.S. Ali is on leave from Aligarh Muslim University, Aligarh, 202 002, India.