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- MakaleAçık Erişim2023Scopus SJRQ3Correlations between seismic b-value and heat flow density in Vlora-Lushnja-Elbasani-Dibra Fault Zone in Elbasani area, central Albania
Ormeni, Rrapo; Hasimi, Albana; Öztürk, Serkan; Çomo, Ervin
In this study, the correlations between the heat flow density and seismotectonic b-value in the El-basani area of Albania were investigated to understand the how low-velocity layers underneath the Elbasani area in central Albania struggling the large-scale Vlora-Lushnja-Elbasani-Dibra Fault Zone affect the heat flow data. For this purpose, the heat flow and regional distribution of b-value were imaged for different locations and depths. To achieve the analysis, the Albanian Seismological Catalogue for the period between 1 July 1968 and 26 December 2022, including 1830 earthquakes with a local magnitude of 0.5 ≤ Ml ≤ 5.2 that occurred at the depths below 70 kilometres, was considered. The b-value was calculated as 1.03 ± 0.06 by considering the magnitude of the completeness value as Mc-value = 2.6. This result shows that the b-value of earthquake distribution in the Vlora-Lushnja-Elbasani-Dibra (VLED) fault zone is well represented by the Gutenberg and Richter (G-R) scaling law with the b-value close to 1.0. The regional variations of the b-value show that b-values smaller than 0.9 were observed in the western and south-western parts of the Llinxha-Kozan thermal water belt. The depth distribution of the b-value indicates that there exists a sharp decrease in the b-values from 1.15 to 0.7 in the depths varying from 5 to 20 km. The highest heat flow values were observed on the Dumrea diapiric dome and in the central part of the Elbasani area. Thus, our analysis indicates significant and robust correlations between the geothermal and earthquake distribution. The discontinuity of Moho interface is deep in the regions where high b-values were observed. Low b-values are found at the depths ranging from 20–25 km and 35–40 km in the Dumrea evaporite massif area. We have evidence that high b-values and large heat flow values are related to the low seismic velocity layers underneath the Elbasani area. The low-velocity zone (LVZ) in Albania occurs in the Earth’s crust and in the upper mantle. It is characterized by an unusu-ally low seismic shear wave velocity compared to the surrounding depth intervals. It is well known that the low-velocity layers in the Elbasani area are determined in the upper crust, at shallow depths of 2–4 km, and in the middle crust at a 10–14 km depth. Hence, it is suggested that the Moho interface in the eastern part of the Elbasani area is relatively deep (45 km) compared to the western part of Albania (35 km), and the magnitude of earthquakes is smaller where the high heat flow values were observed.
AtıfScopus7WoS4İncele - MakaleAçık Erişim2013Scopus SJRQ1The genesis of the slab window-related Arzular low-sulfidation epithermal gold mineralization (eastern Pontides, NE Turkey)
Akaryali, Enver; Tüysüz, Necati
The Arzular mineralization is one of the best examples of epithermal gold deposits in the eastern Pontides orogenic belt. The mineralization is hosted by the subduction-related basaltic andesites and is mainly controlled by E-W and NE-SW trending fracture zones. The main ore minerals are galena, sphalerite, pyrite, chalcopyrite, tetrahedrite and gold. Homogenization temperatures of fluid inclusions are between 130 and 295 C for quartz and between 90 and 133 C for sphalerite. Sulphur isotope values obtained from pyrite, galena and sphalerite vary between -1.2‰ and 3‰, indicating that sulphur belongs to magmatic origin and was derived from the Lutetian non-adakitic granitic intrusions in the region. Oxygen isotope values are between 15.0‰ and 16.7‰, and hydrogen isotope values are between -87‰ and -91‰. The sulphur isotope thermometer yielded temperatures in the range of 244-291 C for the ore formation. Our results support the hypothesis that the Arzular mineralization is a low-sulfidation epithermal gold deposit associated with non-adakitic subduction-related granitic magmas that were generated by slab window-related processes in a south-dipping subduction zone during the Lutetian.
AtıfScopus25WoS19OpenAlex29İncele - MakaleYalnız künye2011Scopus SJRQ1Crystal fractionation of adakitic magmas in the crust-mantle transition zone: Petrology, geochemistry and U-Pb zircon chronology of the Seme adakites, eastern Pontides, NE Turkey
Eyuboglu, Yener; Santosh, M.; Chung, Sun-Lin
Plutonic and porphyritic intrusions of adakitic rocks are widely distributed in the southern part of the eastern Pontides orogenic belt in Turkey. Ranging in age from late Paleocene to early Eocene, these intrusions provide critical information to evaluate the early Cenozoic geodynamic evolution of the eastern Mediterranean region. Here we report the results from our field, petrologic, geochemical and zircon U-Pb geochronological studies on adakitic intrusions in the Seme area from the southern part of eastern Pontides belt. The Seme granitoid, Daldibi dacite and Aslanca dacite porphyry from this region carry abundant plagioclcase, amphibole and biotite phenocrysts and have geochemical affinities typical of adakites including high SiO2 (58.48-75.6wt.%), Al2O3 (15.78-18.28wt.%), Na2O (3.94-5.08wt.%), Sr (506-1413ppm), and La (12.6-52.9ppm), moderate K2O (1.77-2.76wt.%), and low Y (4.7-14.2ppm) and Yb (0.28-1.29ppm). The early Eocene intrusions in the Seme area have compositional similarities with high-slica adakites, and their geochemical features suggest the involvement of slab-derived melts. The zircons separated from these rocks show euhedral crystal shapes with oscillatory cores typical of crystallization from magmas, as also confirmed by their high Th/U ratios (0.78 to 1.15). U-Pb analyses of zircons from the quartz diorite yielded a weighted mean 206Pb/238U age of 53.16±0.45Ma. Zircon grains from the Aslanca dacite porphyry occurring as a late phase within the Seme body show U-Pb isotopic ages of 53 and 52Ma concordant with U-Pb ages of zircons from quartz diorite. Based on major, trace and rare earth element data, we present a model suggesting crystal fractionation and/or differentation processes of subduction-related adakitic magmas stored in the crust-mantle transition zone, and their transfer into shallow depths of the overriding continental lithosphere.
AtıfScopus104WoS99OpenAlex100İncele - MakaleYalnız künye2011Scopus SJRQ1Late Triassic subduction-related ultramafic-mafic magmatism in the Amasya region (eastern Pontides, N. Turkey): Implications for the ophiolite conundrum in Eastern Mediterranean
Eyuboglu, Yener; Santosh, M.; Bektas, Osman; Chung, Sun-Lin
The eastern Pontides orogenic belt of northeastern Turkey offers critical clues on convergent margin tectonics associated with the late Mesozoic-early Cenozoic geodynamic evolution of the eastern Mediterranean region. Here we report the geology, petrology, geochemistry, Nd-Sr-Pb isotopes and U-Pb zircon ages from a ultramafic-mafic complex in Aksalur which forms part of a series of Alaskan-type ultramafic-mafic bodies in the Amasya region located at the south-western corner of the eastern Pontides orogenic belt. These ultramafic-mafic intrusions occur as minor (30-300m in diameter), scattered, roughly circular bodies within the low-grade metamorphic rocks of the Tokat metamorphic massif. Petrographic studies characterise the rock types as gabbro and wehrlite, with the latter showing typical cumulate texture and mainly comprising serpentinized olivine, clinopyroxene, hornblende, mica and opaque minerals. The gabbroic rocks are characterized by relatively high initial ratios of 143Nd/144Nd (0.512618-0.512633) and low initial ratios of 87Sr/86Sr (0.70420-0.70435). Their initial Pb isotope ratios range from 17.306 to 17.771. The gabbros and cumulate wehrlites display geochemical distribution patterns analogous to the Alaskan-type intrusions that were derived from a subduction-related, high-alumina, hydrous basaltic parental magma in a convergent plate setting. LA-ICPMS analyses of zircons separated from the gabbros show high Th/U ratios (1.35-5.26) typical of magmatic origin. The U-Pb isotopic data define a weighted mean 206Pb/238U age of 203.3±4.9Ma. Detailed evaluation of the magma tectonics suggests that the Alaskan-type Aksalur ultramafic-mafic intrusions were accumulated in magma chamber(s) located at relatively shallow crustal levels. Two distinct magmatic pulses are identified: the first phase produced the gabbroic intrusions and the second phase was characterized by numerous small-scale werhlitic cumulate intrusions. In contrast to the previous models which assigned a mid-oceanic ridge-derived ophiolite affinity for ultramafic-mafic complexes in the eastern Pontides orogenic belt, our study reveals that these intrusions were derived from subduction-related high-alumina hydrous basaltic magmas transferred into the overlying relatively thin continental crust along deep-seated fractures.
AtıfScopus56WoS53İncele - MakaleAçık Erişim2011Scopus SJRQ1Transition from shoshonitic to adakitic magmatism in the eastern Pontides, NE Turkey: Implications for slab window melting
Eyuboglu, Yener; Chung, Sun-Lin; Santosh, M.; Dudas, Francis O.; Akaryali, Enver
The formation of the eastern Pontides orogenic belt has been widely assigned to a northward subduction of the Neotethyan oceanic slab during the late Mesozoic-Cenozoic. Here we provide an alternate model based on new geological, geochemical and isotopic data. The magmatic activity in the far south of the belt started in the early Campanian with shoshonitic trachyandesites and associated pyroclastics. This sequence is covered by the late Campanian-early Maastrichtian reefal limestones and another stage of high-K volcanism represented by analcimized leucite-rich ultrapotassic rocks of the Maastrichtian-early Paleocene (?) ages. The shoshonitic and ultrapotassic rocks, with K2O contents ranging from 0.26 to 6.95 wt.%, display broadly similar rare earth and multi-element distribution patterns. Both rock types are enriched in LILE and LREE and depleted in HFSE (Nb,Ta and Ti), suggesting a subduction-enriched mantle source for the magma generation. Subsequently, during the late Paleocene, a stage of acidic magmatism (SiO2 of 53.25-73.61 wt.%) that shows adakitic geochemical characteristics including high Sr/Y (46-416) and La/Yb (11-51) and low Y (2.6-12.2 ppm), is documented characterized by melting of a mafic source such as the MORB crust with garnet in the residue. The adakitic magmatism began at similar to 56 Ma and migrated toward the north through time, culminating with porphyritic andesites (similar to 47 Ma) that were emplaced in the Gumushane-Bayburt line and its vicinity. North of this line, coeval magmas show typical calc-alkaline nature and continued to develop toward further north until the middle to late Eocene. Based on the spatial and temporal variations in the magmas generated in the eastern Pontides orogenic belt, we propose a new geodynamic model to explain the tectonomagmatic evolution of these rocks and correlate the adakitic magmatism to ridge subduction and slab window process within a south-dipping subduction zone. Our model is in contrast to the previous proposals which envisage partial melting or delamination of thickened lower continental crust due to the collision in the south during the Paleocene-Eocene. (C) 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
AtıfScopus172WoS166OpenAlex176İncele - MakaleAçık Erişim2010Scopus SJRQ1Structure and geochemistry of an Alaskan-type ultramafic-mafic complex in the Eastern Pontides, NE Turkey
Eyuboglu, Yener; Dilek, Yildirim; Bozkurt, Erdin; Bektas, Osman; Rojay, Bora; Sen, Cuneyt
The Karayasmak ultramafic-mafic association (KUMA) in NE Turkey represents an Alaskan-type, pre-Liassic intrusion in the Pulur metamorphic massif and is one of many such intrusive complexes that were emplaced into the continental basement of the Eastern Pontides belt during the pre-Liassic. Its main lithological units include plagioclase peridotite, melagabbronorite, banded gabbro and anorthosite (Phase-I), gabbro-pegmatite dikes (Phase-II), unmetamorphosed banded gabbro (Phase-III), cumulate olivine gabbronorite (Phase-IV), and non-cumulate gabbroic dikes and stocks (Phase-V). The contact relations between these units are gradational or intrusive, with the peridotites (Phase-I) enveloping the cumulate gabbronorites (Phase-IV) in the center of the elliptical body, displaying a concentric reverse-zoning pattern. Cr-Al spinel, plagioclase, and olivine are the first crystallizing phases in all cumulate rocks, whereas pyroxene, hornblende, phlogopite, magnetite, and ilmenite represent the intercumulus phases. The existence of hornblende and phlogopite, the high Wo and Cr2O3 contents of clinopyroxene, and the high Fo and NiO contents of olivine indicate that the KUMA units were the near-liquidus fractional crystallization products of hydrous basaltic magma. The Phase-I and Phase-III cumulates are slightly enriched in LILE and LREE, depleted in HFSE and HREE with respect to chondrite and primitive mantle, and show negative Nb, Zr, Hf and Ti anomalies. The Phase-IV cumulate gabbronorites are even more enriched in LILE and LREE and show less depletion in HFSE and HREE in comparison to the earlier phases. The KUMA units formed from high-Al hydrous basaltic magmas, which were derived from partial melting of a previously subduction-metasomatized subcontinental-lithospheric mantle. These magmas underwent crystal fractionation and mineral concentration processes in small magma chamber(s) at shallow crustal levels (< 5 kbar).
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