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21.
W.?SiebelEmail author A.?K.?Schmitt E.?Kiemele M.?Dani?ík F.?Aydin 《Contributions to Mineralogy and Petrology》2011,162(6):1233-1247
The Acigöl rhyolite field erupted the most recent high-silica rhyolites within the Cappadocian Volcanic Province of central Anatolia, Turkey. It comprises two sequences of domes and pyroclastic rocks with eruption ages of ~150–200 ka (eastern group) and ~20–25 ka (western group). Compositionally, the eastern rhyolite group lavas are less evolved (SiO2 = 74–76 wt%), whereas the western group has higher silica abundance (SiO2 = ~77 wt%) with extremely depleted feldspar-compatible trace elements. Within each group, compositional variability is small and 143Nd/144Nd (0.51257–0.51265) and Pb isotope compositions (206Pb/204Pb = 18.87–18.88, 207Pb/204Pb = 15.65–15.67 and 208Pb/204Pb = 38.94–38.98) are homogeneous. The western group rhyolites have δ18O(zircon) overlapping mantle values (5.7 ± 0.2‰), whereas eastern group rhyolites are enriched in δ18O by ~0.5‰, consistent with a tendency to lower εNd values. By contrast, western group rhyolites have markedly more radiogenic 87Sr/86Sr ratios (0.7065–0.7091) compared to those of the eastern group (0.7059–0.7065). The presence of angular granitic xenoliths and a correlation between hydration (based on loss on ignition data) and 87Sr/86Sr in the western lavas, however, indicates that Sr was added during the eruption or post-eruption alteration. Isotope constraints preclude the possibility that the rhyolite magmas formed by partial melting of any known regional crystalline basement rocks. Basalts and andesites erupted in the periphery of the Acigöl field are characterised by 87Sr/86Sr ratios between 0.7040 and 0.7053, 143Nd/144Nd = 0.51259–0.51300, 206Pb/204Pb = 18.85–18.87, 207Pb/204Pb = 15.646–15.655, 208Pb/204Pb = 38.90–38.97. The isotopic and trace element data favour an origin of the rhyolites by mixing of basaltic/andesitic magmas with minor amounts of crustal melts and followed by extensive fractional crystallization. 相似文献
22.
In this paper, an experimental study on the cut depth, which is an important cutting performance indicator in the abrasive waterjet (AWJ) cutting of rock, was presented. Taguchi experimental design of an orthogonal array was employed to conduct the experiments. A variety of nine types of granitic rocks were used in the cutting experiments. The experimental data were used to assess the influence of AWJ operating variables on the cut depth. Using regression analysis, models for prediction of the cut depth from the operating variables and rock properties in AWJ machining of granitic rocks were then developed and verified. The results indicated that the cut depths decreased with increasing traverse speed and decreasing abrasive size. On the other hand, increase of the abrasive mass flow rate and water pressure led to increases in the cut depths. Additionally, it was observed that the standoff distance had no discernible effects on the cut depths. Furthermore, from the statistical analysis, it was found that the predictive models developed for the rock types had potential for practical applications. Verification of the models for using them as a practical guideline revealed a high applicability of the models within the experimental range used. 相似文献
23.
Selahattin Kadir A. Piril Önen-Hall S. Nihal Aydin Cengiz Yakicier Nurten Akarsu Murat Tuncer 《Environmental Geology》2008,54(2):391-409
The Cretaceous-Eocene volcano-sedimentary units of the Zonguldak region of the western Black Sea consist of subalkaline andesite
and tuff, and sandstone dominated by smectite, kaolinite, accessory chlorite, illite, mordenite, and analcime associated with
feldspar, quartz, opal-CT, amphibole, and calcite. Kaolinization, chloritization, sericitization, albitization, Fe–Ti-oxidation,
and the presence of zeolite, epidote, and illite in andesitic rocks and tuffaceous materials developed as a result of the
degradation of a glass shards matrix, enclosed feldspar, and clinopyroxene-type phenocrysts, due to alteration processes.
The association of feldspar and glass with smectite and kaolinite, and the suborientation of feldspar-edged, subparallel kaolinite
plates to fracture axes may exhibit an authigenic smectite or kaolinite. Increased alteration degree upward in which Al, Fe,
and Ti are gained, and Si, Na, K, and Ca are depleted, is due to the alteration following possible diagenesis and hydrothermal
activities. Micromorphologically, fibrous mordenite in the altered units and the presence of needle-type chrysotile in the
residential buildings in which cancer cases lived were detected. In addition, the segregation pattern of cancer susceptibility
in the region strongly suggested an environmental effect and a genetic influence on the increased cancer incidence in the
region. The most likely diagnosis was Li-Fraumeni syndrome, which is one of the hereditary cancer predisposition syndromes;
however, no mutations were observed in the p53 gene, which is the major cause of Li-Fraumeni syndrome. The micromorphology
observed in the altered units in which cancer cases were detected may have a role in the expression of an unidentified gene,
but does not explain alone the occurrence of cancer as a primary cause in the region. 相似文献
24.
Sivas Basin is the easternmost and third largest basin of the Central Anatolian Basins. In this study, gravity, aeromagnetic and seismic data are used to investigate the deep structure of the Sivas Basin, together with the well seismic velocity data, geological observations from the surface and the borehole data of the Celalli-1 well. Basement depth is modeled three-dimensionally (3D) using the gravity anomalies, and 2D gravity and magnetic models were constructed along with a N–S trending profile. Densities of the rock samples were obtained from the distinct parts of the basin surface and in-situ susceptibilities were also measured and evaluated in comparison with the other geophysical and geological data. Additionally, seismic sections, in spite of their low resolution, were used to define the velocity variation in the basin in order to compare depth values and geological cross-section obtained from the modeling studies. Deepest parts of the basin (12–13 km), determined from the 3D model, are located below the settlement of Hafik and to the south of Zara towns. Geometry, extension and wideness of the basin, together with the thickness and lithologies of the sedimentary units are reasonably appropriate for further hydrocarbon exploration in the Sivas Basin that is still an unexplored area with the limited number of seismic lines and only one borehole. 相似文献
25.
Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in urban air samples of Konya, Turkey between August 2006 and May 2007. The concentrations of pollutants in both the gas and particulate phase were separately analysed. The average total (gas + particulate) concentrations of PAHs, PCBs and OCPs were determined as 206 ng m− 3, 0.106 ng m− 3, 4.78 ng m− 3 respectively. All of the investigated target compounds were dominantly found in the gas phase except OCPs. Higher air concentrations of PAHs were found at winter season while the highest concentrations of PCBs were determined in September. The highest OCPs were detected in October and in March. In urban air of Konya, PCB 28 and PCB 52 congeners represent 46% and 35% of total PCBs while Phenanthrene, Fluoranthene, Pyrene accounted for 29%, 13%, 10% of total PAHs. HCH compounds (α + β + γ + δ-HCH), total DDTs (p,p′-DDE, p,p′-DDD, p,p′-DDT), Endosulfan compounds (Endosulfan I, Endosulfan II, Endosulfan sulfate) were dominantly determined as 30%, 21%, 20% of total OCPs respectively. Considering the relation between these compounds with temperature, there was no significant correlation observed. Despite banned/restricted use in Turkey, some OCPs were determined in urban air. These results demonstrated that they are either illegally being used in the course of agricultural activity and gardens in Konya or they are residues of past use in environment. According to these results, it can be suggested that Konya is an actively contributing region to persistent organic pollutants in Turkey. 相似文献
26.
Orhan Karsli Abdurrahman Dokuz İbrahim Uysal Faruk Aydin Raif Kandemir Jan Wijbrans 《Lithos》2010,114(1-2):109-120
Early Cenozoic (48–50 Ma) adakitic volcanic rocks from the Eastern Pontides, NE Turkey, consist of calc-alkaline and high-K calc-alkaline andesite and dacite, with SiO2 contents ranging from 56.01 to 65.44 wt.%. This is the first time that Early Eocene volcanism and adakites have been reported from the region. The rocks are composed of plagioclase, amphibole, quartz, and Mg-rich biotite. They have high and low-Mg# values ranging from 55 to 62 and 13 to 42, respectively. High-Mg# rocks have higher Ni and Co contents than low-Mg# samples. The rocks exhibit enrichments in large ion lithophile elements including the light rare earth elements, depletions in Nb, Ta and Ti and have high La/Yb and Sr/Y ratios. Their relative high ISr (0.70474–0.70640) and low εNd (50 Ma) values (? 2.3 to 0.8) are inconsistent with an origin as partial melts of a subducted oceanic slab. Combined major- and trace element and Sr–Nd isotope data suggest that the adakitic magmas are related to the unique tectonic setting of this region, where a transition from a collision to an extension stage has created thickening and delamination of the Pontide mafic lower crust at 50 Ma. The high-Mg adakitic magmas resulted from partial melting of the delaminated eclogitic mafic lower crust that sank into the relatively hot subcrustal mantle, and its subsequent interaction with the mantle peridotite during upward transport, leaving garnet as the residual phase, elevates the MgO content and Mg# of the magmas, whereas low-Mg# magmas formed by the melting of newly exposed lower crustal rocks caused by asthenospheric upwelling, which supplies heat flux to the lower crust. The data also suggest that the mafic lower continental crust beneath the region was thickened between the Late Cretaceous and the Late Paleocene and delaminated during Late Paleocene to Early Eocene time, which coincides with the initial stage of crustal thinning caused by crustal extensional events in the Eastern Pontides and rules out the possibility of an extensional regime before ~ 50 Ma in the region during the Late Mesozoic to Early Cenozoic. 相似文献
27.
Emanuel J.M. Willemse David C.P. Peacock Atilla Aydin 《Journal of Structural Geology》1997,19(12):1461-1477
Small-scale structures along strike-slip fault zones in limestones exposed around the Bristol Channel, U.K., suggest that pressure solution plays a key role during fault nucleation and growth. Incipient shear zones consist of enéchelon veins. The first generation of solution seams form due to bending of the intact rock (bridge) between overlapping veins. As the bridge rotates, slip occurs along the seams, linking the veins, causing cm-scale calcite-filled pull-apart structures to form and allowing fault displacement to increase. A second generation of solution seams forms at the tip of the sliding seams. As displacement increases further, causing larger rotation, slip also can occur along these second-generation solution seams, producing the third generation of solution seams as well as tail cracks (pinnate veins) at their tips. These three generations of solution seams all contribute to the formation of individual fault segments. Fourth and fifth generations of solution seams occur within larger-scale contractional oversteps between side-stepping fault segments. The oversteps are breached by slip along these localized solution seams, eventually leading to the formation of a distinct through-going fault with several metres of displacement.The initial enéchelon veins, solution seams of various generations and tail cracks progressively fragment the fault-zone material as fault slip accumulates. Slip planes nucleate on these pre-existing discontinuities, principally along the clay-enriched, weaker solution seams. This can be observed at a variety of scales and suggests that Mode II shear fracturing does not occur as a primary fracture mechanism, but only as a macroscopic phenomenon following Mode I (veins and tail cracks) and anti-mode I (solution seams) deformation. It appears that solution seams can play a similar role to microcracks in localizing a through-going slip plane. This micromechanical model of faulting may be applicable to some other faults and shear zones in host rocks which are prone to pressure solution. 相似文献
28.
29.
We have studied a few optical spectra of the symbiotic star CH Cygni obtained in the period January 1990-June 1991, which indicate that a mild increase of activity occurred between July and December 1990. This increase of activity is confirmed by the IUE observations made in the same period. In fact, in this period of time, we have observed an increase of intensity of all the emission lines both in the optical and ultraviolet ranges and of the continuous ultraviolet flux.Based on observations obtained at the Observatory of Haute Provence (OHP) and on observations by the International Ultraviolet Explorer (IUE) collected at the Villafranca Satellite Tracking Station. 相似文献
30.
I. Uysal M. B. Sadiklar M. Tarkian O. Karsli F. Aydin 《Mineralogy and Petrology》2005,83(3-4):219-242
Summary A large number of podiform chromitite bodies of massive, disseminated and nodular type have been located in ultramafic units, composed of depleted mantle harzburgite and dunite of the Marmaris Peridotite from Ortaca (Mula, SW Turkey). The chromite ore bodies are surrounded by dunite envelopes of variable thickness, exhibiting transitional boundaries to harzburgite host rocks. Chromitites, containing a large number of inclusions, i.e. silicates, base metal sulphides and alloys, and platinum-group minerals (PGM) have a wide range of chemical composition. The Cr# [Cr/(Cr+Al)] values of most chromitites are high (0.61–0.81) and Mg# [Mg/(Mg+Fe2+)] values range between 0.65 and 0.71 with TiO2 content lower than 0.24wt.%, which may reflect the crystallization of chromites from boninitic magmas in supra-subduction setting environment.Platinum-group minerals (PGM) such as laurite, erlichmanite and Os–Ir alloys, silicates such as olivine, clinopyroxene and amphibole, and base metal sulphides (BM-S), alloys (BM-A) and arsenides (BM-As) are found as inclusions in chromite or in the serpentine matrix. Platinum-group element (PGE) concentrations of the Ortaca chromitites (OC) are low in all samples. Total PGE (Ir+Ru+Rh+Pt+Pd) ranges from 63ng/g to 266ng/g and Pd/Ir ratios range between 0.23 and 4.75. PGE content is higher and the Pd/Ir ratio lower in Cr-rich chromitites compared to Al-rich ones. There is a strong negative correlation between the Cr# and Pd/Ir ratios (r=–0.930). The PGE patterns show a negative slope from Ru to Pt and a positive slope from Pt to Pd. The low PGE content in the majority of the OC may reflect a lack of sulphur saturation during an early stage of their crystallization. The laurite compositions show a wide range of Ru–Os substitution caused by relatively low temperature and increasing f(S2) during the chromite crystallization. The high Cr# of and hydrous silicate mineral inclusions in chromite imply that chromite crystallized in a supra-subduction setting. 相似文献