Age and Chemistry of Miocene Volcanic. Rocks from the Kiraz Basin of the Küçük Menderes Graben: Its Significance for the Extensional Tectonics of Southwestern Anatolia,Turkey'

Neogene volcanic rocks and granitoid plutons are among the most important geological components of western Turkey. Although they are voluminous north of the Gediz Graben, they are very scarce to the south, where volcanic rocks occur as isolated small exposures in a small number of localities. The Kiraz Basin of the Küçük Menderes Graben is a key locality, in which Tertiary volcanic rocks crop out at three locations. These rocks have been chemically analysed and dated (³⁹Ar-⁴⁰Ar whole rock and biotite analyses) in order to understand their tectonic setting of emplacement and its relation to the wider structure of western Anatolia. Whole rock and biotite ³⁹Ar-⁴⁰Ar ages vary between 13.9 ± 0.2 Ma and 14.6 ± 0.2 Ma.

The Kiraz volcanic rocks are calc-alkaline, with a compositional range from basaltic andesite to dacite. They are strongly enriched in the light ion lithophile elements (LILE) and have chemistries typical of lavas erupted in subduction-related settings. Their close association with rift-bounding faults suggests eruptions via conduits flanking grabens in an extensional environment. The difference in chemical composition and age between the Kiraz volcanic rocks and the slightly older calc-alkaline volcanic rocks north of the Gediz Graben is attributed to their relatively younger ages and greater proximity to the Aegean Arc. Their calc-alkaline chemistry reflects magma generation influenced by the slab descending beneath this arc and eruption/emplacement in an extensional setting.     

Teshima pyroclastics: Onset of characteristic Setouchi magmatism induced by slab melting at 14.8 Ma

Ar-Ar ages, and petrographical and geochemical characteristics of pyroclastics and an overlying lava from Teshima Island, southwest Japan are presented. Although previous geological and age data suggested Teshima pyroclastics were products of magmatism > 3 my prior to lava flows of Setouchi volcanic rocks generated in association with southward migration of the southwest Japan arc sliver during opening of the Sea of Japan backarc basin at ~ 15 Ma, the present results led to the conclusion that a sequence of Setouchi volcanism, induced by slab melting and subsequent melt-mantle reactions, produced both pyroclastics and lava at 14.6–14.8 Ma. This age is oldest among those reported so far and may represent the timing of onset of characteristic Setouchi magmatism immediately posterior to and hence as a result of the mega-tectonic event including rotation of the southwest Japan arc sliver.     

Chemical composition of sediments from the subducting Cocos Ridge segment at the Southern Central American subduction zone

Subducted sediments play an important role in the magmatism at subduction zones and the formation of mantle heterogeneity, making them an important tracer for shallow crustal processes and deep mantle processes.Therefore, ascertaining the chemical compositions of different subduction end-members is a prerequisite for using subducted sediments to trace key geological processes. We reports here the comprehensive major and trace element analyses of 52 samples from two holes（U1414 A and U1381 C） dri...     

Coexistence of lawsonite‐bearing eclogite and blueschist: phase equilibria modelling of Alpine Corsica metabasalts and petrological evolution of subducting slabs

In Alpine Corsica (France), deeply subducted metabasalts are well preserved as lawsonite‐bearing eclogite (Law‐Ecl), occurrence of which is restricted to ～10 localities worldwide. The Corsican Law‐Ecl, consisting of omphacite + lawsonite + garnet + phengite + titanite, occurs as both single undeformed metabasaltic pillows surrounded by lawsonite blueschist (Law‐Bs), and carbonate‐bearing eclogitic veins. Law‐Bs are found as variably deformed metabasaltic pillows locally cross‐cut by eclogitic veins and consist of glaucophane + actinolite + lawsonite + garnet + phengite + titanite. Field evidence and microstructures reveal that both Law‐Ecl and Law‐Bs are stable at the metamorphic peak in the lawsonite‐eclogite stability field. Isochemical phase diagrams (pseudosections) calculated for representative Law‐Ecl and Law‐Bs samples indicate that both lithologies equilibrated at the same conditions of ～520 ± 20 °C and 2.3 ± 0.1 GPa. Therefore, the coexistence at the same peak metamorphic conditions of Law‐Ecl and Law‐Bs implies that different portions of deeply subducted oceanic crust may store significantly different H₂O contents, depending on bulk‐rock chemical composition. In addition, thermodynamic modelling of phase equilibria indicates that the occurring progressive dehydration reactions, which are significantly depending on bulk‐rock chemical composition, strongly influence rock densification and eclogite formation in subducting slabs.     

Dynamic response of double beam rested on stochastic foundation under harmonic moving load

This paper deals with the dynamic response of infinite double Euler–Bernoulli beam supported by elastic foundation with stochastic stiffness subjected to an oscillating moving load, which is the first research in relevant literature review. In this matter, equations of motion for double beam are formulated in a moving frame of reference. Moreover, by employing the first order perturbation theory and calculating contour integration, the response of double beam is obtained analytically and validated by a stochastic finite element model. Sensitivity analyses on the various parameters of closed form solution such as velocity, load frequency, coefficient of variation of soil foundation and rail and slab bending stiffness show the significant effect of load frequency on the dynamic response of the doubled beam. From practical point of view, the obtained results of the present study can be utilized efficiently in analysis and design of slab track systems. Copyright © 2013 John Wiley & Sons, Ltd.     

莺歌海—琼东南盆地构造-地层格架及南海动力变形分区

通过对盆地地震剖面构造-地层的详细解释,在莺歌海盆地和琼东南盆地(简称莺-琼盆地)古近纪同裂陷充填序列中识别出一条区域性的构造变革界面——T70,该界面在地震剖面上表现为显著的下削上超的地震反射结构特征,发育的时代为32～30 Ma,与南海海底扩张起始和红河断裂带左旋走滑的时间一致;T70界面将莺-琼盆地的同裂陷期地层...     

Hysteretic behavior and strength capacity of shallowly embedded steel column bases with SFRCC slab

A series of shallowly embedded steel column bases consisting of an exposed column base and a floor slab is tested under horizontal cyclic loading to very large deformation. The effects of floor slabs on strength and ductility are examined using concrete and Steel fiber‐reinforced cementitous composites (SFRCC) for the floor slab. The elastic stiffness, maximum strength, and dissipated energy of the column bases when they include SFRCC increase by 40, 70, and 70% over those of corresponding column bases with concrete floor slab. Better bonding behavior is notable for SFRCC, and the maximum strength and dissipated energy further increase by 15–30% and 70–90%, respectively, owing to the careful arrangement of reinforcing bars. Numerical models are developed to enhance the understanding the behavior of shallowly embedded column bases. Procedures for estimating the elastic stiffness and maximum strength of shallowly embedded column bases with conventional concrete are calibrated for their applicability to those with SFRCC slab. Copyright © 2011 John Wiley & Sons, Ltd.     

Grain-growth kinetics in wadsleyite: Effects of chemical environment

Grain-growth kinetics in wadsleyite was investigated using a multianvil high-pressure apparatus. Fine-grained wadsleyite aggregates were synthesized by isostatic hot-pressing and were subsequently annealed under high pressure and temperature in a controlled chemical environment. Wadsleyite samples show normal grain-growth characterized by a log-normal grain-size distribution following the relation, where n is a constant, L the grain-size at time t, L₀ the grain-size at time t = 0 and k is a rate constant that depends on temperature T and chemical environments (fO₂: oxygen fugacity in Pa, C_OH: water content in H/10⁶Si) as:

     

Estimation of the Effect of Lateral Flow on Piled Bridge Abutments in Soft Ground Considering Piled Slabs as a Countermeasure of the Abutments

The effectiveness of a simple method to estimate the lateral movement of piled bridge abutments due to lateral flow from the safety factor (Fs) of slope stability analysis was studied. This was accomplished through the construction and measurement of actual piled bridge abutments and its backfill, with and without piled slabs as a countermeasure. To do this, a computer program SLOPILE (VER 3.0) considering the lateral earth pressure acting on a row of piled bridge abutment was developed. SLOPILE (VER 3.0) can calculate the slope stability for both planar failure surfaces in infinite slopes and arc failure surfaces based on Fellenius or Bishop simplified methods. SLOPILE (VER 3.0) was utilized to design the piled bridge abutment reinforced by a piled slab at a real site. The piled slab can effectively prevent the lateral flow of soft ground and satisfy not only the safety factor of a slope but also the allowable bearing capacity of piles. To verify the design method, an instrumentation system was adapted. The instrumentation results from a case study clearly showed that the piled slab effectively resisted the lateral movement of a bridge abutment due to placement of backfill. Also, the surcharge loads due to backfill were supported by the piled slab and transmitted to the bedrock through the piled slab.