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Geochemistry and Petrogenesis of Permo–Triassic Silicic Volcanic Rocks from the Circum-Rhodope Belt in the Vardar/Axios Zone, Northern Greece: An Example of a Post-Collision Extensional Tectonic Setting in the Tethyan Realm
The western side of the Vertiskos Unit crystalline basement in northern Greece is fringed by a Permo–Triassic low-grade metamorphic volcano-sedimentary complex that belongs to the Circum-Rhodope Belt (CRB), which is an important part of the Vardar/ Axios oceanic suture zone. The silicic volcanic rocks from the CRB are mainly rhyolitic to rhyodacitic lavas with aphyric and porphyritic textures as well as pyroclastic deposits. In this study, geochemical data obtained with X-ray fluorescence (XRF) for the CRB silicic volcanic rocks are reported and discussed to constrain their petrogenesis and tectonic setting. The rocks are peraluminous and show enrichment in K, Rb, Th, Zr, Y, and Pb while being depleted in Ba, Sr, Nb, P, and Ti, and they have Zr + Nb + Y + Ce > 350 ppm, which are characteristic features of anorogenic A-type granites. They have a Y/Nb ratio > 1.2 and belong to A2-subtype granitoids, implying crust-derived magma in a post-collisional tectonic setting. The high Rb/Sr ratio (3.45–39.14), the low molar CaO/(MgO + FeOt) ratio, and the CaO/Na2O ratio (
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