排序方式： 共有39条查询结果，搜索用时 15 毫秒
1.
2.
In the Sandıklı (Afyon) region, western Taurides, the Late Proterozoic rocks of the Sandıklı basement complex are composed of low-grade meta-sedimentary rocks (Güvercinoluk Formation) intruded by felsic rocks (Kestel Cayı Porphyroid Suite, KCPS). The KCPS is a deformed and highly sheared, dome-shaped rhyolitic body with a granitic core. Quartz porphyry dikes intrude both the slightly metamorphic igneous and the sedimentary rocks of the basement complex. Both the quartz porphyries and rhyolites were converted into mylonites with relict igneous textures. Geochemical data show that these felsic igneous rocks are subalkaline and mainly granitic in composition with SiO2 >72 wt% and Al2O3 >11.5 wt%. The chondrite-normalized incompatible trace element patterns are characterized by distinct negative Rb, Nb, Sr, P, Ti, and Eu with enrichment in Th, U, La, Ce, Nd, Sm, and Zr. The REE patterns of the felsic rocks indicate a strong enrichment in LREE but display slightly flat HREE patterns. According to geochemical characteristics and petrogenetic modeling, extrusive and intrusive rocks of the KCPS were probably derived from an upper continental crustal source (partial melting of granites/felsic rocks) by 18–20% fractional melting plus 18–20% Rayleigh fractional crystallization, which seems to be the most effective igneous process during the crystallization of the KCPS. Single zircon age data from the granitoids and fossils from the disconformably overlying sedimentary successions indicate that the metamorphism and the igneous event in the Taurides are related to the Cadomian orogeny. Based on the geological, geochemical and petrogenetic correlation of the post-collisional granitoids it is further suggested that the Tauride belt in western central Turkey was in a similar tectonic setting to the Gondwanan terranes in North Africa (Younger Granitoids) and southern Europe (Spain, France, Bohemia, Brno Massifs) during the Late Cadomian period. 相似文献
3.
4.
Oxygen and sulfur isotope systematics of sulfate produced by bacterial and abiotic oxidation of pyrite 总被引：4，自引：0，他引：4
Nurgul Balci Wayne C. Shanks III Kevin W. Mandernack 《Geochimica et cosmochimica acta》2007,71(15):3796-3811
To better understand reaction pathways of pyrite oxidation and biogeochemical controls on δ18O and δ34S values of the generated sulfate in acid mine drainage (AMD) and other natural environments, we conducted a series of pyrite oxidation experiments in the laboratory. Our biological and abiotic experiments were conducted under aerobic conditions by using O2 as an oxidizing agent and under anaerobic conditions by using dissolved Fe(III)aq as an oxidant with varying δ18OH2O values in the presence and absence of Acidithiobacillus ferrooxidans. In addition, aerobic biological experiments were designed as short- and long-term experiments where the final pH was controlled at ∼2.7 and 2.2, respectively. Due to the slower kinetics of abiotic sulfide oxidation, the aerobic abiotic experiments were only conducted as long term with a final pH of ∼2.7. The δ34SSO4 values from both the biological and abiotic anaerobic experiments indicated a small but significant sulfur isotope fractionation (∼−0.7‰) in contrast to no significant fractionation observed from any of the aerobic experiments. Relative percentages of the incorporation of water-derived oxygen and dissolved oxygen (O2) to sulfate were estimated, in addition to the oxygen isotope fractionation between sulfate and water, and dissolved oxygen. As expected, during the biological and abiotic anaerobic experiments all of the sulfate oxygen was derived from water. The percentage incorporation of water-derived oxygen into sulfate during the oxidation experiments by O2 varied with longer incubation and lower pH, but not due to the presence or absence of bacteria. These percentages were estimated as 85%, 92% and 87% from the short-term biological, long-term biological and abiotic control experiments, respectively. An oxygen isotope fractionation effect between sulfate and water (ε18OSO4-H2O) of ∼3.5‰ was determined for the anaerobic (biological and abiotic) experiments. This measured value was then used to estimate the oxygen isotope fractionation effects between sulfate and dissolved oxygen in the aerobic experiments which were −10.0‰, −10.8‰, and −9.8‰ for the short-term biological, long-term biological and abiotic control experiments, respectively. Based on the similarity between δ18OSO4 values in the biological and abiotic experiments, it is suggested that δ18OSO4 values cannot be used to distinguish biological and abiotic mechanisms of pyrite oxidation. The results presented here suggest that Fe(III)aq is the primary oxidant for pyrite at pH < 3, even in the presence of dissolved oxygen, and that the main oxygen source of sulfate is water-oxygen under both aerobic and anaerobic conditions. 相似文献
5.
Ugur Kagan Tekin Cengiz Okuyucu Kaan Sayit Yavuz Bedi Paula J. Noble Leopold Krystyn Mehmet Cemal Gncüoglu 《Island Arc》2019,28(2)
Blocks and tectonic slices within the Mersin Mélange (southern Turkey), which are of Northern Neotethyan origin (Izmir–Ankara–Erzincan Ocean (IAE)), were studied in detail by using radiolarian, conodont, and foraminiferal assemblages on six different stratigraphic sections with well‐preserved Permian succesions. The basal part of the Permian sequence, composed of alternating chert and mudstone with basic volcanics, is assigned to the late Asselian (Early Permian) based on radiolarians. The next basaltic interval in the sequence is dated as Kungurian. The highly alkaline basic volcanics in the sequence are extremely enriched, similar to kimberlitic/lamprophyric magmas generated at continental intraplate settings. Trace element systematics suggest that these lavas were generated in a continental margin involving a metasomatized subcontinental lithospheric mantle source (SCLM). The middle part of the Permian sequences, dated by benthic foraminifera and conodont assemblages, includes detrital limestones with chert interlayers and neptunian dykes of middle Wordian to earliest Wuchiapingian age. Higher in the sequence, detrital limestones are overlain by alternating chert and mudstone with intermittent microbrecciated beds of early Wuchiapingian to middle Changhsingian (Late Permian) age based on the radiolarians. A large negative shift at the base of the Lopingian at the upper part of section is correlated to negative shifts at the Guadalupian/Lopingian boundary associated with the end‐Guadalupian mass extinction event. All these findings indicate that a continental rift system associated with a possible mantle plume existed during the late Early to Late Permian period. This event was responsible for the rupturing of the northern Gondwanan margin related to the opening of the IAE Ocean. When the deep basinal features of the Early Permian volcano‐sedimentary sequence are considered, the proto IAE oceanic crust formed possibly before the end of the Permian. This, in turn, suggests that the opening of the IAE Ocean dates back to as early as the Permian. 相似文献
6.
Nurgul Celik Balci 《Environmental Earth Sciences》2010,60(3):485-493
A series of experiments was conducted to better understand the bacterial influence on the release of trace metals during oxidation
of sphalerite mineral and element cycles in acid mine drainage (AMD) systems. Batch experiments were carried out as biotic
and abiotic control at pH 3. Acidithiobacillus ferrooxidans, sulfur and Fe(II) oxidizer, was used in the biotic sphalerite experiment. The abiotic control experiment was run without
adding the bacteria. The release behavior of six trace metals (As, Cd, Co, Pb, Cu and Mn), Fe and Zn were determined during
the period of 54 days. Compared to the abiotic experiments, enhanced oxidation of sphalerite by bacteria produced high sulfate
(~2,000 mg/L) and Fetot (139 mg/L) along with the low pH (<2.3). Consistent with this, the concentration of trace metals (As, Cd, Co, Pb, Cu and
Mn) was significantly higher in the biotic experiments than those in the abiotic experiments. Results indicate that the distributions
of Co and Cd in both biotic and abiotic experiments are directly related to the sphalerite dissolution whereas Pb, Cu distribution
shows no strong relation to sphalerite dissolution especially in the abiotic experiments. Pb distribution in the solution
appears to be controlled by pH-dependent solubility. Approximately 80% of the trace metals were removed from the solution
at the end of the biotic experiments along with biologically induced Fe precipitation. Experimental results showed that bacteria
play major role not only in the release of trace metal from sphalerite but also in controlling concentration of the metals
in the solution by producing Fe-oxyhydroxides. The study suggest that in order to develop an effective rehabilitation strategy
for AMD, it is necessary to understand bio/geochemical processes governing mobilization and deposition of trace metals in
the environment. 相似文献
7.
The polarization direction or 'sign’ of reflected converted P–S waves depends upon the angle of incidence of the incident P-wave. Sign reversal due to reversal of the angle of incidence is often encountered and is an impediment to P–S wave processing and imaging, because when P–S events or P-S migrated images with mixed signs are stacked, destructive interference occurs. We have created and demonstrated a means of correcting for this reversal. To do this, a P-wave angle of incidence is calculated for every point in the image space. This is done by calculating a P–S reflected waveform for every point, by extrapolating the reflected S-wavefield backwards from the receiver line, and then cross-correlating this waveform with the S-wave reflections observed at the receiver line. A multiplier, (sgn α) is assigned to each point in the image space, where α is the angle of incidence of the P-wave. The multiplier was applied to a set of prestack reverse time migration images derived from a cross-borehole physical elastic model data set. The improvement in the stacked image when the sign correction is applied is spectacular. The P-S image quality is comparable to, or better than, stacked migrated P-P images. The method appears to be applicable to all reflection modes and to all recording geometries. 相似文献
8.
Serhat?K?ksal Rolf?L.?Romer M.?Cemal?G?ncüoglu Fatma?Toksoy-K?ksalEmail author 《International Journal of Earth Sciences》2004,93(6):974-989
The last stages of the continental collision during the closure of the Neotethyan ocean in central Anatolia are characterized by post-collisional H- and A-type granitoids intruding both the metamorphic country rocks and allochthonous ophiolitic rocks of the central Anatolian crystalline complex. Available Rb–Sr and K–Ar whole-rock and mineral age data on the H- and A-type granitoids in central Anatolia are inconsistent. To better constrain the geological relevance and the timing of the change in the chemical character of magmatism in the wake of the Alpine orogeny in Anatolia, we re-evaluated the geochemical characteristics and dated titanite from representative H- (Baranadag quartz-monzonite: BR) and A-type (Çamsari quartz-syenite: CS) granitoids by the U–Pb method. BR is a high-K calc-alkaline intrusion with mafic microgranular enclaves and shows enrichment of LILE relative to HFSE. The alkaline CS displays higher SiO2, Na2O+K2O, Fe/Mg, Rb, Th and HFSE with corresponding depletion in CaO, MgO, Fe2O3tot, P2O5, Ba, Sr, and Ti. Chondrite-normalized REE patterns of the BR and CS samples have LREE-enriched and flat HREE patterns, whereas CS differs from BR by higher LREE enrichment and lower MREE and HREE contents. Mineralogical and geochemical characteristics suggest that BR and CS were not products of the same magma source. BR was derived from a subduction-modified depleted hybrid-source and CS had an enriched mantle source with significant crustal contribution. The U–Pb titanite ages of the H-type central Anatolian granitoids (BR) and the A-type granitoids (CS) are 74.0±2.8 and 74.1±0.7 Ma, respectively. The coeval evolution of post-collisional/calc-alkaline H- to A-type magmatism was possibly associated with source heterogeneity and variable involvement of continental materials during the evolution of these granitoids. These new age data constrain the timing of the onset of a post-collision extensional period following the Alpine thickening within the passive margin of the Tauride–Anatolide platform, which occurred before the opening of the latest Cretaceous central Anatolian basins.An erratum to this article can be found at 相似文献
9.
10.
In the Sandıklı-Afyon area, the very low-grade metamorphic Sandıklı Basement Complex with clastic sediments and Late Neoproterozoic felsic igneous rocks are unconformably overlain by a cover succession with red continental clastic rocks, tholeiitic basalts and siliciclastic rocks with Early Cambrian trace fossils. Illite crystallinity studies reveal that both the basement and cover units were metamorphosed at high anchizonal to epizonal conditions ( 300 °C). Textural data together with the detailed evaluation of the P–T–b0 grid, however, indicate that this thermal event has multiple phases. The first tectonothermal event was realized at pressures of 4.2 kb on the basis of b0-data and resulted in development of blastomylonites. This is supported by the presence of dynamo-metamorphosed pebbles within the basal conglomerates of the Lower Paleozoic cover series. The second event is post-Ordovician–pre-Jurassic in age, occurred at lower pressures 3.2 kb and produced a weakly developed cleavage in the siliciclastic rocks of the cover. The mineralogical/textural data across the basement-cover boundary therefore indicate the removal of an entire metamorphic zone and thus a metamorphic hiatus.
These data suggest that the Taurides were affected by a Late Neoproterozoic event as part of the peri-Gondwana during the Cadomian orogeny. 相似文献