Petrogenesis of post-collisional Middle Eocene volcanism in the Eastern Pontides (NE,Turkey): Insights from geochemistry,whole-rock Sr-Nd-Pb isotopes,zircon U-Pb and 40Ar-39Ar geochronology

The debate about whether Eocene magmatism is considered to be post-collisional or subduction-related or not still continues. Here we offer new ⁴⁰Ar-³⁹Ar ad U-Pb zircon geochronology, mineral chemistry, bulk rock and Sr-Nd-Pb isotope geochemistry data obtained from the southern dike (SD) suite, in comparison with the northern dike (ND) suite, from the Eastern Pontides. The geochronological data indicate that the SD suite erupted between 45.89 and 45.10 Ma corresponding to the Lutetian (Middle Eocene). The magmas of the ND suite are characterised by slightly more alkaline affinity compared to the SD suite. The trace and rare earth element (REEs) content of the SD suite is characterised by large ion lithophile element (LILEs; Sr, K₂O, Ba, Rb) enrichment and depletion of Nb, Ta, and TiO₂ elements to different degree with high Th/Yb ratios, which indicate that the magmas forming the SD and ND suites were derived from lithospheric mantle sources enriched by mostly slab-derived fluids in the spinel stability field. The Sr, Nd and Pb radiogenic isotope ratios of the dikes support the view that the magma for the hydrous group (H-SD) was derived from a relatively more enriched mantle source than the other SD and ND suites. The ND suite and the anhydrous group (A-SD) display similar geochemical features characterised by moderate light earth element (LREE)/heavy rare earth element (HREE) ratios, while the H-SD group has respectively lower LREE/HREE ratios indicating higher melting degree. Detailed considerations of the alkalinity, enrichment and partial melting degree for the source of the studied volcanic rocks indicate that the magmas of the northern dike suite are characterised by slightly more alkaline affinity, whereas the magmas throughout the southern dike suite show increments in the enrichment rate and melting degree. In light of the obtained data and comparative interpretations, the geodynamic evolution and differences in petrogenetic character of the Lutetian magmas from both the northern and southern parts of the Eastern Pontides may be explained by different degrees of melting of a net veined mantle source initially metasomatized by mostly subduction fluids during asthenospheric upwelling due to fragmented asymmetric delamination in a post-collisional extensional tectonic environment.     

Selective Separation and Preconcentration of Fe(III) and Zn(II) Ions by Solvent Extraction Using a New Triketone Reagent

A simple, rapid, and accurate method was developed for separation and preconcentration of trace levels of iron(III) and zinc(II) ions in environmental samples. Methyl‐2‐(4‐methoxy‐benzoyl)‐3‐(4‐methoxyphenyl)‐3‐oxopropanoylcarbamate (MMPC) has been proposed as a new complexing agent for Fe(III) and Zn(II) ions using solvent extraction prior to their determination by flame atomic absorption spectrometry (FAAS). Fe(III) and Zn(II) ions can be selectively separated from Fe(II), Pb(II), Co(II), Cu(II), Mn(II), Cr(III), Ni(II), Cd(II), Ag(I), Au(III), Pd(II), Cr(VI), and Al(III) ions in the solution by using the MMPC reagent. The analytical parameters such as pH, sample volume, shaking time, amount of MMPC reagent, volume of methyl isobutyl ketone (MIBK), effect of ionic strength, and type of back extractant were investigated. The recovery values for Fe(III) and Zn(II) ions were greater than 95% and the detection limits for Fe(III) and Zn(II) ions were 0.26 and 0.32 µg L^?1, respectively. The precision of the method as the relative standard deviation changed between 1.8 and 2.1%. Calibration curves have a determination coefficient (r²) of at least 0.997 or higher. The preconcentration factor was found to be 100. Accuracy of the method was checked by analyzing of a certified reference material and spiked samples. The developed method was applied to several matrices such as water, hair, and food samples.     

Determination of Cu,Fe, and Ni in Spices after Preconcentration on Diaion‐HP 20 Resin as Their Zincon Complexes

In this work, a new separation–preconcentration method was developed for the determination of trace amounts of Cu(II), Ni(II), and Fe(III) by flame atomic absorption spectrometry (FAAS). Analytes were complexed by using zincon (2‐[2‐[alpha(2‐hydroxy‐5‐sulfophenylazo) benzylidene] hydrazino] benzoic acid sodium salt). The analyte ions were quantitatively adsorbed on a Diaion HP‐20 resin at pH 5. The retained metal ions on the resin were eluted by acetone. The analytical parameters such as pH of the sample, eluent type and volume, sample volume, and flow rates of the solution and the eluent were investigated. The influences of concomitant ions on the recoveries of the analytes were also examined. The instrumental detection limits for the analytes after application of the presented solid‐phase extraction procedure were in the range of 0.72–1.41 µg/L. The validation of the presented procedure was checked by analyzing certified reference material of SRM1515 Apple Leaves. The procedure was performed by analyzing some spice samples.     

Mineralogy,diagenesis and hydrochemical evolution in a probertite–glauberite–halite saline lake (Miocene,Emet Basin,Turkey)

The Emet basin is one of the Neogene basins in western Turkey containing significant amounts of borate minerals, mainly colemanite. The petrologic study of core samples from two exploratory wells in the Do?anlar sector, under optic and electron microscopy, reveals a complex mineral association in which probertite, glauberite, and halite constitute the major primary phases (without mineral precursors) precipitated in a saline lake placed in a volcano-sedimentary context. Other sulfates (anhydrite, gypsum, thenardite, celestite and kalistrontite), borates (colemanite, ulexite, hydroboracite, tunellite, kaliborite and aristarainite), and sulfides (arsenopyrite, realgar and orpiment) are attributed to early diagenesis. So far, the Do?anlar deposit is the most important deposit of probertite known up to now.Chemical changes in the groundwater inflow led to the precipitation of Ca-bearing borates (colemanite) in the tuff-flat environment surrounding the lake, while Na–Ca sulfates and borates (glauberite and probertite) precipitated in the center of the lake. Fluid inclusion compositions in halite indicate that the advanced brines correspond to the Na-K-Cl-SO₄ type. During restricted stages of the saline lake, the residual brines seeped through the tuff-flat sediments, leading to transformations of previous precipitates that resulted in the formation of K-bearing minerals.The abundance of coccoid-like biogenic dolomite, colloidal arsenopyrite and the isotopic composition of sulfates are indicative of bacterial sulfate reduction. In contrast, arsenic sulfides are attributed to acidophilic micro-organisms in oxidizing conditions. Fluctuations of redox conditions in both free and interstitial brines control the biological influence in some diagenetic transformations.     

New paleomagnetic constraints on the late Cretaceous and early Cenozoic tectonic history of the Eastern Pontides

The Pontides are characterized by a series of Mesozoic-Cenozoic fold belts comprising a N-vergent foreland fold and thrust belt in the Western Pontides and a concave, upward-shaped fold belt in the Eastern Pontides. The curvature of the fold belt follows the Caucasus which may imply a phase of oroclinal bending. In order to test whether the fold curvature represents a phase of oroclinal bending, a paleomagnetic study has been carried out in the Eastern Pontides on late Cretaceous and middle Eocene volcanic and sedimentary rocks from 29 sites. Rock magnetic studies reveal medium-temperature components with an unblocking temperature of 400–580 °C, indicating pseudo-single domain titanomagnetite as the most abundant carrier of magnetic remanence in the middle Eocene rocks studied here. In the upper Cretaceous rocks, a high-temperature component with an unblocking range of 580–650 °C was isolated. Stepwise thermal and alternating field demagnetization isolated two components of remanent magnetization in middle Eocene rocks comprising a low unblocking temperature/coercivity component near the present field direction and a characteristic remanent magnetization (ChRM) component of D_s = 332.3°, I_s = 49.9° (k = 33.3, α₉₅ = 9.2°, N = 15 sites). A positive fold test at a 95% confidence level and a reversal test indicate a primary magnetization. Component analysis of the upper Cretaceous rocks identifies a stable ChRM D_s = 160.3°, I_s = −45.0°, (k =  85.6, α₉₅ = 6.0°, N =  8 sites) following removal of secondary remanence. Their ChRM direction passes fold and reversal tests at a 95% confidence level. Both the upper Cretaceous and middle Eocene paleomagnetic data from the Eastern Pontides and the Lesser Caucasus clearly demonstrate evidence of oroclinal bending that occurred contemporaneouslywith the convergence between Arabia and Eurasia in the Paleocene.     

How does the Red Sea outflow water interact with Gulf of Aden Eddies?

As the Red Sea overflow water (RSOW) enters the Gulf of Aden (GOA), it interacts with a sequence of nearly barotropic, mesoscale eddies originating in the Indian Ocean. To investigate how these eddies impact the dispersal and eastward transport of the RSOW toward the Indian Ocean, a high resolution 3D regional model is employed to explore systematically the interaction between the RSOW and mesoscale eddies. Two types of experiments are conducted. In the first set, we simulate the behavior of RSOW in the presence of an idealized cyclone and an idealized anticyclone. The second type of simulation involves nesting of the regional model (ROMS) within a data-assimilating global model (HYCOM), in which a sequence of mesoscale eddies entering the Gulf of Aden is realistically captured. This simulation is integrated for one year, and includes a simple representation of the seasonality of the RSOW.Bower et al. (2002) suggest that the Red Sea overflow might be a western boundary undercurrent. Consistent with these expectations, the idealized simulations show that the preferred pathway of the RSOW in the absence of eddies is along the coast of Somalia (southern continental shelf) as a western boundary undercurrent. Simultaneously, a cyclonic circulation is generated in the far western GOA due to vortex stretching by the descending outflow. The presence of a cyclone in the western GOA increases the peak RSOW transport, but the cyclone itself rapidly loses its coherence after interacting with the rough topography in the western GOA. The presence of an anticyclone tends to block the preferred boundary pathway and inhibits the eastward transport of the RSOW. The eddies also result in substantially increased mixing of the RSOW in the western GOA.On the basis of the more realistic ROMS experiment, it is found that the modeled RSOW leaves the western part of the Gulf of Aden in short episodic bursts with transports that are an order of magnitude greater than that associated with the quasi-steady RSOW inflow into GOA. Such enhancement in RSOW transport is shown to be induced by cyclonic eddies that cause a rapid discharge of RSOW from the western part of the GOA. We conclude that mesoscale eddies play a key role in the transport and mixing of the RSOW within GOA.     

An energy budget for the subtidal bivalve Modiolus barbatus (Mollusca) at different temperatures

Clearance rates, respiration rates and food absorption efficiencies of the commercially interesting subtidal bivalve Modiolus barbatus were measured at different temperatures under laboratory conditions and scope for growth calculated. Clearance rates were highest at temperatures from 20 °C to 28 °C, whereas respiration rate was maximal at 9 °C and minimal at 26 °C. Highest mean values of absorbed energy occurred at 20 °C and 26 °C. Scope for growth trend had negative values at 9 °C, 15 °C and 28 °C and positive values at temperatures 20 °C and 26 °C. The profitable thermal window for M. barbatus to have energy sufficient for growth and reproduction corresponded to <5 months per year. Seawater temperature increases will potentially impact the eco-physiological responses of subtidal M. barbatus causing life history traits to change with important repercussions for subtidal biodiversity in the Mediterranean.