The time of the onset and the nature of the extension in the Aegean area have been problematic owing to the confusion of neotectonic replacement structures with neotectonic revolutionary structures. This paper concerns two rift systems of different ages and orientations in the Gokova region of southwestern Anatolia. The first system has a northwest-southeast trend with a Middle to Upper Miocene infill, whereas the second system is orientated in an east-west direction and filled with Plio-Quaternary rocks. Structural and palaeomagnetic data indicate that the first system originally had a north-south trend, and then bodily rotated anticlockwise to its present orientation before the end of the Miocene. Both the orientations and the structural patterns of these cross-cutting rift systems suggest that they resulted from two different and successive tectonic regimes. Regional geology suggests that the generative regime of the older system was characterized by north-south compression and related to the palaeotectonic evolution of southwestern Anatolia, whereas that of the younger system is characterized by north-south extension and relates to the neotectonic evolution of this region. This inference contradicts, at least in southwestern Anatolia, some recent claims that the extensional tectonics and the related rift formation in the Aegean region began in the early Miocene, with the alleged demise of the compressional palaeotectonics during the late Oligocene, but is consistent with older views that placed the onset of north-south extension into the later middle Miocene. The formation of the Aegean Sea seems to be the result of these two complicated and contrasting, succesive tectonic regimes that have affected this region since middle Miocene times.
ÖZ Bu çalışmada, Türkiye'nin en büyük ve en eski maden atık sahası Balıkesir Balya Pb-Zn maden atık sahasının biyojeokimyası ve asidik maden drenajı (AMD) oluşumuna etkileri jeokimyasal, moleküler ve mikrobiyolojik teknikler birlikte kullanılarak araştırılmıştır. Balya atık sahasında Pb-Zn madencilik aktivitelerinden geride kalan sülfürce zengin pasaların/atıkların atmosferle teması sonucunda düşük pH'lı (2.7) ve yüksek metal içerikli (1.88 mg/L Pb, 24 mg/L Zn, 2.5 mg/L As ve 17 mg/L Cu) asidik sularoluşarak ortamın kontamine olmasına neden olmaktadır. Maden atığı, sediman, asidik ve yüzey suyu örneklerinde gerçekleştirilen jeokimyasal ve mikrobiyolojik analizler çevre açısından zararlı metallerin taşınmasında ve dağılımında sülfürce zengin atıkların ayrışmasından kaynaklanan asidik suların (pH 2.7) birincil etken olduğunu göstermiştir. Balya atık sahasında gelişen ve asidik drenaj suyu içeren göletlerde gerçekleştirilen kultivasyon temelli mikrobiyoloji çalışması sonucunda asidik suların ortalama asidofilik sülfür oksitleyen (aSOB) ve asidofilik Fe oksitleyen bakteri (aFeOB) miktarları sırası ile 8.4x10 8 cell/ ml ve 9.6 x10 7 cell/ml'dir. Aynı değerler, atıkların ulaştığı Maden deresi yüzey su örneklerinde 3.8 x10 6 cell/ml ve 5.7x10 3 cell/ml olarak asidik sulara oranla daha düşük saptanmıştır. Maden deresi ve asidik gölet sedimanları üzerinde gerçekleştirilen 16S rDNA dizi analizine göre Balya atık sahasında Fe ve S döngüsünde Acidithiobacillus spp. grubuna bağlı prokaryotların dominant olduğu ortaya konmuştur. Bunun yanısıra, daha az oranda S oksidasyonunda etkili Sulfobacillus spp. populasyonuda tespit edilmiştir. Ayrıca, asidik suların ve atıkların ulaştığı daha düşük asidik karakter gösteren Maden Deresi sediman örneklerinde indirgenmiş sülfür türlerini (örn. kükürt) oksitleyen Thiobacillus spp. ve Thiovirga spp. cinsine bağlı mikroorganizmalar tespit edilmiştir. Bu türlerin tespiti, sahada değişen jeokimyasal
The chain of Late Subhercynian granitoids can be traced along the Srednogorie-lstranca-Pontid belt. The Demirk6y pluton outcrops in the Istranca segment. The rocks of the pluton range from diorite through grandiorite to perthite granite with granodiorite predominating. On the basis of 25 chemical analyses, the intrusive setting of the granitoid has been investigated. Calcic to calc-alkaline and peraluminous to metaluminous character indicate a subduction-related origin. Low to moderate concentrations of the large-ion lithophiles (LIL), high field strength elements (HFS), light rare earth elements (La, Ce) and low HFS/LIL ratios indicate a mantle-derived magma with subduction-related enrichment. Trace element discrimination diagrams such as Rb/Zr-Nb, Rb/Zr-Y, Rb-SiO2 and Rb-(Nb + Y), are particularly indicative of normal arc-setting for the samples.The Demirk6y granitoid is chemically indistinguishable from the Upper Cretaceous granitoids of Strednogorie to the west and the Pontids to the east. This extensive maximum of plutonism can be considered as a time marker in the northern Tethys subduction system.
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