Timing of Igralishte pluton in Ograzhden Mountain, SW Bulgaria: implications for the tectono-magmatic evolution of the region

Pages: 
pp. 5-14
Geological Institute, Bulgarian Academy of Science, 1113 Sofia; Institute of Isotope Geochemistry and Mineral Resources, ETH-Zurich, 8092 Zurich
Institute of Isotope Geochemistry and Mineral Resources, ETH-Zurich, 8092 Zurich
Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Science, 1113 Sofia
Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Science, 1113 Sofia
Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Science, 1113 Sofia;
Institute of Geology, Ural Division, Russian Academy of Sciences, 167982 Syktyvkar, Russia
Abstract: 

U-Pb-zircon and monazite ID-TIMS and in-situ LA-ICP-MS and EPMA analyses are combined to define the magmatic age of the Igralishte granite, which is exposed over 32 km2 in the high-metamorphic rocks of the Serbo-Macedonian Massif (Ograzhden Mountain, SW Bulgaria). The granite is dated at 243.28 ± 0.84 Ma by concordant zircons (ID-TIMS data) and this intrusion age is confirmed also by in-situ LA-ICP-MS and EPMA monazite analyses. The intrusion of the Igralishte granite at middle Triassic time defines the age of the high-grade metamorphism in Ograzhden Mountain as Pre-Triassic. A tectonic and hydrothermal overprint is dated at 36.36 ± 0.56 Ma by the Rb-Sr whole-rock-biotite reference line. This age is considered as the youngest thermal event in the region of the Igralishte pluton that reached the 300 ± 50 °C closing temperature of the Rb-Sr isotope system in the biotite, but could not fully reset the Rb-Sr isotope system of the muscovite. The initial strontium ratio of 87Sr/86Sri = 0.7078 and the inheritance of old lead components in the zircons suppose crustal-dominated source of the magma. Preferred tectonic scenario suggests dehydration melting and granite formation in the middle/upper crust at the Permian-Triassic boundary and the Lower-Middle Triassic caused by mafic intrusions at the base of the crust.

Keywords: 

granite, Serbo-Macedonian Massif, Permian-Triassic, U-Pb, Rb-Sr, zircon, monazite

VOLUME 38 (1-3)/December 2009

Geological Institute, Bulgarian Academy of Science, 1113 Sofia; Institute of Isotope Geochemistry and Mineral Resources, ETH-Zurich, 8092 Zurich
|
Institute of Isotope Geochemistry and Mineral Resources, ETH-Zurich, 8092 Zurich
|
Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Science, 1113 Sofia
|
Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Science, 1113 Sofia
|
Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Science, 1113 Sofia;
|
Institute of Geology, Ural Division, Russian Academy of Sciences, 167982 Syktyvkar, Russia

Department of Geography & Climatology, Faculty of Geology & Geoenvironment, National & Kapodistrian University of Athens, University Campus (Panepistimiopolis), Zografou, ZC 15784, Athens, Greece
|
Department of Dynamic-Tectonic-Applied Geology, Faculty of Geology & Geoenvironment, National & Kapodistrian University of Athens, University Campus (Panepistimiopolis), Zografou, ZC 15784, Athens, Greece
|
Department of Geography & Climatology, Faculty of Geology & Geoenvironment, National & Kapodistrian University of Athens, University Campus (Panepistimiopolis), Zografou, ZC 15784, Athens, Greece

Institute of Botany, Bulgarian Academy of Sciences, Sofia 1113, Acad. G. Bonchev Str., Bl. 23
|
Institute of Botany, Bulgarian Academy of Sciences, Sofia 1113, Acad. G. Bonchev Str., Bl. 23

Department of Hydrogeology, Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
|
Department of Hydrogeology, Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
|
Hydrogeology Laboratory, Institute of Water Problems, Russian Academy of Sciences, 119991 Moscow, Russia

Sofia University, Dept. of Geology, Paleontology and Fossil Fuels, 15 Tsar Osvoboditel Blvd., 1504 Sofia, Bulgaria
|
Sofia University, Dept. of Geology, Paleontology and Fossil Fuels, 15 Tsar Osvoboditel Blvd., 1504 Sofia, Bulgaria