Precambrian to Early Cretaceous rocks of the Strandja Massif (northwestern Turkey): evolution of a long lasting magmatic arc

Abstract

The Strandja Massif, northwestern Turkey, forms a link between the Balkan Zone of Bulgaria, which is correlated with the Variscan orogen in Europe, and the Pontides, where Cimmerian structures are prominent. Five fault-bounded tectonic units form the massif structure. (1) The Kırklareli Unit consists of the Paleozoic basement intruded by the Carboniferous to Triassic Kırklareli metagranites. It is unconformably overlain by Permian and Triassic metasediments. (2) The Vize Unit that is made of Neoproterozoic metasediments, which are intruded by Cambrian metagranites, and overlain by the pre-Ordovician molasse. Unconformably laying the Ordovician quartzites pass upward into quartz schists and then to alternating marble and chert of, possibly, latest Devonian age. Rocks of the Vize Unit are intruded by the late Carboniferous metagranites. The Vize Unit may be correlated with the passive continental margin of the Istanbul Zone. (3) The Mahya accretionary complex and (4) the paired Yavuzdere magmatic arc were formed in the Carboniferous. (5) Nappes consisting of the Jurassic dolomites and marbles thrust to the north in late Jurassic – early Cretaceous time. They occupy the highest structural position on all above-mentioned tectonic units. Tectonic subdivision of the Strandja Massif is supported by new 18 ages of magmatic and detrital zircons. The long duration of subduction-related magmatism in the region and its continuity in the Triassic contradicts with the widely accepted ideas about the dominance of the passive continental margin settings in the tectonic evolution of the Strandja Massif. The massif is interpreted as a fragment of the long-lived, Cambrian to Triassic Silk Road magmatic arc. At least since the late Paleozoic this arc evolved on the northern side of Paleo-Tethys.

The phanerozoic palaeotectonics of Turkey. Part I: an inventory

“…The Strandja Mountains [westernmost Pontides (Ketin 1966a): northwestern Turkey and southeastern Bulgaria] Perhaps the most spectacular example of a Scythide/ Cimmeride suture in Turkey has recently been mapped in some detail by and Natal'in et al (2012Natal'in et al ( , 2016. The uniqueness of this suture stems from the fact that a continuous development from at least the late Palaeozoic into the early Cretaceous can be observed with a clarity that leaves little to be desired.…”

“…A Jurassic sequence following them sits on them across a mylonitic zone. Natal'in et al (2016) interpreted this boundary as a thrust, but we regard it as a low-angle normal fault, because it in places elides in the entire Triassic section. This normal fault may have been coeval with those that opened the Luda Kamčija Trough just to the north during the Pliensbachian-Toarcian interval in which deposition commenced with the Sinivir Formation (Tchoumatchenco et al 1992), although Elmas et al (2011) reported a considerable late Jurassic-early Cretaceous ( 40 Ar/ 39 Ar ages between 156 to 143 Ma) extension leading to the formation of an extensional metamorphic core complex in the northeastern Strandja.…”

“…This is similar to the probably Devonian or Triassic phyllitoid schists and diabases northwest of Gramatikovo (Kalvacheva and Čatalov 1974) and the 'Diabase-Phyllitoid' Formation, a part of the Sokol Formation, in Bulgaria (Chatalov 1985), although they are clearly younger than the Sokol Formation. Slightly farther to the northwest, in the Bay of Selvez, there is a lightly metamorphic wildflysch cut by late Cretaceous magmatic rocks belonging to the Alpide evolution (Natal'in et al 2016). The age of this wildflysch is unknown, but may be anywhere between the Carboniferous (Yavuzdere equivalent?)…”

“…For the locations of the sections, see Fig. 5 a basement containing Precambrian granitoids, but sparsity of outcrop does not allow the establishment of the structure of the country rock consisting mainly of phyllites (Natal'in et al 2016). This basement extends as far to the southeast as the Çatalca region (Şahin et al 2014) where there are no age data from the country rocks.…”

Two-Stage Late Jurassic to Early Cretaceous Hydrothermal Activity in the Sakar Unit of Southeastern Bulgaria

“…The Sakar Unit of the Strandja Zone [13], also known as the Strandja (Strandzha) Massif (SM; [14,15] and references therein) or Istranca Massif (IM; [16]), is located in the southeastern part of Bulgaria, close to the border with Turkey and Greece ( Figure 1A). It belongs to the East Srednogorie Zone of the Balkan Orogenic System [17,18].…”