Propagating rift tectonics of a Caledonian marginal basin: Multi-stage seafloor spreading history of the Solund-Stavfjord ophiolite in western Norway

The Late Ordovician Solund-Stavfjord ophiolite in western Norway represents a remnant of the Iapetus oceanic lithosphere that developed in a Caledonian marginal basin. The ophiolite contains three structural domains that display distinctively different crustal architecture that reflects the mode and nature of magmatic and tectonic processes operated during the multi-stage seafloor spreading evolution of this marginal basin. Domain I includes, from top to bottom, an extensive extrusive sequence, a transition zone consisting of dike swarms with screens of pillow breccias, a sheeted dike complex, and plutonic rocks composed mainly of isotropic gabbro and microgabbro. Extrusive rocks include pillow lavas, pillow breccias, and massive sheet flows and are locally sheared and mineralized, containing epidosites, sulfide-sulfate deposits, Fe-oxides, and anhydrite veins, reminiscent of hydrothermal alteration zones on the seafloor along modern mid-ocean ridges. A fossil lava lake in the northern part of the ophiolite consists of a >65-m-thick volcanic sequence composed of a number of separate massive lava units interlayered with pillow lavas and pillow breccia horizons. The NE-trending sheeted dike complex contains multiple intrusions of metabasaltic dikes with one- and two-sided chilled margins and displays a network of both dike-parallel normal and dike-perpendicular oblique-slip faults of oceanic origin. The dike-gabbro boundary is mutually intrusive and represents the root zone of the sheeted dike complex. The internal architecture and rock types of Domain I are analogous to those of intermediate-spreading oceanic crust at modern mid-ocean ridge environments. The ophiolitic units in Domain II include mainly sheeted dikes and plutonic rocks with a general NW structural grain and are commonly faulted against each other, although primary intrusive relations between the sheeted dikes and the gabbros are locally well preserved. The exposures of this domain occur only in the northern and southern parts of the ophiolite complex and are separated by the ENE-trending Domain III, in which isotropic to pegmatitic gabbros and dike swarms are plastically deformed along ENE-striking sinistral shear zones. These shear zones, which locally include fault slivers of serpentinite intrusions, are crosscut by N20°E-striking undeformed basaltic dike swarms that contain xenoliths of gabbroic material. The NW-trending sheeted dike complex in the northern part of Domain II curves into an ENE orientation approaching Domain III in the south. The anomalous nature of deformed crust in Domain III is interpreted to have developed within an oceanic fracture zone or transform fault boundary.REE chemistry of representative extrusive and dike rocks from all three domains indicates N- to E-MORB affinities of their magmas with high Th/Ta ratios that are characteristic of subduction zone environments. The magmatic evolution of Domain I encompasses closed-system fractional crystallization of high-Mg basaltic magmas in small ephemeral chambers, which gradually interconnected to form large chambers in which mixing of primary magmas with more evolved and fractionated magma caused resetting of magma compositions through time. The compositional range from high-Mg basalts to ferrobasalts within Domain I is reminiscent of modern propagating rift basalts. We interpret the NE-trending Domain I as a remnant of an intermediate-spread rift system that propagated northeastwards (in present coordinate system) into a pre-existing oceanic crust, which was developed along the NW-trending doomed rift (Domain II) in the marginal basin. The N20°E dikes laterally intruding into the anomalous oceanic crust in Domain III represent the tip of the rift propagator. The inferred propagating rift tectonics of the Solund-Stavfjord ophiolite is similar to the evolutionary history of the modern Lau back-arc basin in the SW Pacific and suggests a complex magmatic evolution of the Caledonian marginal basin via multi-stage seafloor spreading tectonics.     

Geochemistry and geochronology of the Neoproterozoic Pan-African Transcaucasian Massif (Republic of Georgia) and implications for island arc evolution of the late Precambrian Arabian–Nubian Shield

The Transcaucasian Massif (TCM) in the Republic of Georgia includes Neoproterozoic–Early Cambrian ophiolites and magmatic arc assemblages that are reminiscent of the coeval island arc terranes in the Arabian–Nubian Shield (ANS) and provides essential evidence for Pan-African crustal evolution in Western Gondwana. The metabasite–plagiogneiss–migmatite association in the Oldest Basement Unit (OBU) of TCM represents a Neoproterozoic oceanic lithosphere intruded by gabbro–diorite–quartz diorite plutons of the Gray Granite Basement Complex (GGBC) that constitute the plutonic foundation of an island arc terrane. The Tectonic Mélange Zone (TMZ) within the Middle-Late Carboniferous Microcline Granite Basement Complex includes thrust sheets composed of various lithologies derived from this arc-ophiolite assemblage. The serpentinized peridotites in the OBU and the TMZ have geochemical features and primary spinel composition (0.35) typical of mid-ocean ridge (MOR)-type, cpx-bearing spinel harzburgites. The metabasic rocks from these two tectonic units are characterized by low-K, moderate-to high-Ti, olivine-hypersthene-normative, tholeiitic basalts representing N-MORB to transitional to E-MORB series. The analyzed peridotites and volcanic rocks display a typical melt-residua genetic relationship of MOR-type oceanic lithosphere. The whole-rock Sm–Nd isotopic data from these metabasic rocks define a regression line corresponding to a maximum age limit of 804 ± 100 Ma and εNd_int = 7.37 ± 0.55. Mafic to intermediate plutonic rocks of GGBC show tholeiitic to calc-alkaline evolutionary trends with LILE and LREE enrichment patterns, Y and HREE depletion, and moderately negative anomalies of Ta, Nb, and Ti, characteristic of suprasubduction zone originated magmas. U–Pb zircon dates, Rb–Sr whole-rock isochron, and Sm–Nd mineral isochron ages of these plutonic rocks range between  750 Ma and 540 Ma, constraining the timing of island arc construction as the Neoproterozoic–Early Cambrian. The Nd and Sr isotopic ratios and the model and emplacement ages of massive quartz diorites in GGBC suggest that pre-Pan African continental crust was involved in the evolution of the island arc terrane. This in turn indicates that the ANS may not be made entirely of juvenile continental crust of Neoproterozoic age. Following its separation from ANS in the Early Paleozoic, TCM underwent a period of extensive crustal growth during 330–280 Ma through the emplacement of microcline granite plutons as part of a magmatic arc system above a Paleo-Tethyan subduction zone dipping beneath the southern margin of Eurasia. TCM and other peri-Gondwanan terranes exposed in a series of basement culminations within the Alpine orogenic belt provide essential information on the Pan-African history of Gondwana and the rift-drift stages of the tectonic evolution of Paleo-Tethys as a back-arc basin between Gondwana and Eurasia.     

Late Oligocene–early Miocene olistostromes (sedimentary mélanges) as tectono-stratigraphic constraints to the geodynamic evolution of the exhumed Ligurian accretionary complex (Northern Apennines,NW Italy)

In the Northern Apennines of Italy, mud-rich olistostromes (sedimentary mélanges) occur at different stratigraphic levels within the late Oligocene–early Miocene sedimentary record of episutural/wedge-top basins. They are widely distributed along the exhumed outer part of the Ligurian accretionary complex, atop the outer Apenninic prowedge, over an area about 300 km long and 10–15 km wide. Olistostromes represent excellent examples of ancient submarine mass-transport complexes (MTCs), consisting of stacked cohesive debris flows that can be directly compared to some of those observed in modern accretionary wedges. We describe the internal arrangement of olistostrome occurrences in the sector between Voghera and the Monferrato area, analysing their relationships with mesoscale liquefaction features, which are commonly difficult to observe in modern MTCs. Slope failures occurred in isolated sectors along the wedge front, where out-of-sequence thrusting, seismicity, and different pulses of overpressured tectonically induced fluid flows acted concomitantly. Referring to the Northern Apennines regional geology, we also point out a gradual lateral rejuvenation (from late Oligocene to early Miocene) toward the SE and an increasing size and thickness of the olistostromes along the strike of the frontal Apenninic prowedge. This suggests that morphological reshaping of the outer prowedge via mass-transport processes balanced, with different pulses over a short time span, the southeastward migration and segmentation of accretionary processes. The latter were probably favoured by the occurrence in the northwestern part of the Northern Apennines of major, inherited palaeogeographic features controlling the northward propagation of the prowedge. Detailed knowledge of olistostromes, as ancient examples of MTCs related to syn-sedimentary tectonics and shale diapirism, and of their lateral variations in term of age and size, provides useful information in regard to better understanding of both the tectono-stratigraphic evolution of the Apenninic prowedge and the submarine slope failures in modern accretionary wedges.     

Molecular approach to the chemical characterization of fish-exuded kairomone: a Fourier transform infrared spectroscopic study

Diel vertical migration (DVM) bioassay-guided Fourier transform infrared spectroscopy can be a prominent non-destructive and innovative approach for ecological studies. During the characterization of the nature of the fish-exuded kairomone, the peak area results from the spectroscopic analysis of the control, fish-conditioned (F) and temperature incubated fish-conditioned (IF) treatments of the DVM bioassays demonstrated that there was a strong correlation between the alterations of the amine N–H, amide II, amide IV and CH₃ asymmetric vibrations, suggesting that both N–H and CH₃ molecules may be main components of the fish-exuded kairomone cocktail. The IF treatment, which showed similar results with the control treatment, supported that the kairomone is inactivated by bacterial biodegradation. The seasonal variations in the peak areas of the N–H and CH₃ bands suggested that DVM response varied seasonally, where migration response developed quickly in warmer seasons. The peak area of the amine N–H band of the F and IF treatments relative to control conditions can be used as an ideal indicator of the absence or presence and the promptness of migration, at all seasons.     

Biomonitoring of heavy metals by <Emphasis Type="Italic">Pseudevernia furfuracea</Emphasis> (L.) Zopf in Ankara (Turkey)

The objective of this study was to determine the air pollution level of Ankara and to generate the air pollution map of this city by using Pseudevernia furfuracea (L.) Zopf as a biomonitor. Lichen samples were collected from unpolluted area at Yaprakli Mountains, Cankiri in November 2002 and transplanted to 27 localities in Ankara. Lichen samples were retrieved following an exposure of 3 and 6 months. Heavy metal, Cu, Mn, Ni, Pb and Zn, contents were determined by using inductively coupled plasma spectrometry (ICP). The chlorophyll a and b contents were determined by using DMSO method. The increase in Ni, Pb, Zn and chlorophyll a content of the specimens were statistically important. All the increases and decreases in the variables could be explained by the environmental stress like pollution, but it is hard to say that this is the only reason of these changes, also climatic conditions, seasons, strength of the light and the physiological status of the plant itself effective on these changes. According to the results of heavy metal analysis Pseudevernia furfuracea continued to accumulate heavy metals and worked well as a biomonitor. The air pollution level of Ankara shows great variations because of the great area of the city.     

Magnesium recovery from magnesite tailings by acid leaching and production of magnesium chloride hexahydrate from leaching solution by evaporation

The recovery of magnesium from magnesite tailings in aqueous hydrochloric acid solutions by acid leaching was studied in a batch reactor using hydrochloric acid solutions. Subsequent, production of magnesium chloride hexahydrate (MgCl₂.6H₂O) from leaching solution was also investigated. The effects of temperature, acid concentration, solid-to-liquid ratio, particle size and stirring speed on the leaching process were investigated. The pseudo-second-order reaction model seemed to be appropriate for the magnesium leaching. The activation energy of the leaching process was estimated to be 62.4 kJ mol^− 1. Finally, MgCl₂.6H₂O in a purity of 91% was produced by evaporation of leaching solution obtained at a temperature of 40 °C, 1.0 M acid, solid-to-liquid ratio of 10 g/L, particle size of 100 µm, stirring speed of 1250 rpm and leaching time of 60 min.     

Effects of Fenton Pre‐Treatment on Waste Activated Sludge Properties

Fenton process was investigated for the purpose of biological sludge disintegration. The Box–Wilson experimental design was employed to evaluate the effects of major process variables (Fe(II) and H₂O₂ concentrations) on both disintegration and dewatering performance of sludge. Results showed that 4 g Fe(II)/kg total solids (TSs) and 60 g H₂O₂/kg TS are efficient for floc disintegration. Fenton pre‐treatment enhanced the biodegradability of sludge. For 4 g Fe(II)/kg TS and 60 g H₂O₂/kg TS, 19.4% higher methane production was achieved compared to raw sludge in biochemical methane potential assay. Fenton pre‐treatment resulted in the release of organic sludge components into the liquid phase. For 4 g Fe(II)/kg TS and 60 g H₂O₂/kg TS, dissolved organic carbon and total nitrogen in sludge's supernatant increased by 75.74 and 60.60%, respectively. Fenton pre‐treatment enhanced the filterability of sludge and it can be applied for conditioning purpose before mechanical dewatering units.     

Comparison of Extraction Procedures for Assessing Soil Metal Bioavailability of to Wheat Grains

Agricultural soils have been analyzed to elucidate whether the trace metal distribution changes in relation to agricultural activities and to predict environmental risk. In addition to the extractability of Cu, Mn, Ni, Pb, and Zn in soils was compared by single extraction (hydrochloric acid (HCl), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), calcium chloride (CaCl₂), water (H₂O)), and sequential extraction procedures. The modified Community Bureau of Reference (BCR) sequential extraction procedure (three‐step) used to extraction of metals in soil samples. The extraction capacity of the analyzed metals was found by using single extraction procedures in the order: HCl > EDTA > DTPA > CaCl₂ > H₂O. A single correlation analysis was used to investigate the relationship between extractable metal concentrations in soil solutions and metal accumulation in wheat grains. Simple correlation analyses indicated that the extractable Pb and Ni of soils by HCl, EDTA, and DTPA single extraction procedures were significantly correlated with the metal contents of wheat grains. For CaCl₂, H₂O, and BCR extraction procedures there was a relatively poor correlation between the extractable Cu, Mn, Ni, Pb, and Zn of soils and metal contents of wheat grains.