Triassic rift-related meta-granites in the Internal Hellenides, Greece

Abstract

AbstractThe Serbo-Macedonian Massif is a basement complex in the Internal Hellenides of northern Greece, situated between the Vardar Zone to the west and the Rhodope Massif to the east. The Serbo-Macedonian Massif comprises several distinct basement units interpreted as terranes, the largest of which is the Gondwana-derived Vertiskos Terrane in the northwestern and central parts of the massif. A series of leucocratic meta-granites intrude the Silurian orthogneiss basement of the Vertiskos Terrane. No similar granites are found in any of the other units of the Internal Hellenides. The meta-granites have a pronounced crustal within-plate signature which is visible in lithology, major- and trace-element geochemistry and the Sr isotopic compositions. These intrusions were dated using the Pb–Pb single-zircon evaporation method, and yielded a Triassic age of between 240.7 ± 2.6 Ma and 221.7 ± 1.9 Ma on 17 samples, with a mean age of 228.3 ± 5.6 Ma. The zircons are purely magmatic, indicating that ages are primary crystallization ages. A Rb–Sr errorchron of the whole-rock samples of the Arnea granite yielded an age of 231.6 ± 9.9 Ma (MSWD = 82), and a mean 87Sr/86Sr initial ratio is 0.7142, indicating a crust-dominated source, and suggesting an A-type origin for the granites. The A-type meta-granites together with mafic intrusive bodies (amphibolites) in the Vertiskos Terrane may be evidence of Triassic rifting that led to the formation of a branch of Neotethys (Vardar–Meliata Ocean). Similar rock associations are also exposed in the Cyclades, and in massifs of the wider eastern Mediterranean realm related to the Gondwana-derived Hun Terrane, indicating that the Arnea-type granites are representatives of a major regional rifting event in Triassic times.