Triggering of hydrothermal ore mineralization in the Central Rhodopean Core Complex (Bulgaria) ― Insight from isotope and geochronological studies on tertiary magmatism and migmatization

摘要

Ore deposits in the Central Rhodopes typically occur in the vicinity of silicic dike swarms at the most intensively "stretched" sections of the extensional system. The beginning of the extensional stage is marked by the intrusion of early-stage non-penetratively deformed granite bodies at 53 (Pripek granites, U-Pb on single Zr and Mnz) and 42-43 Ma (Smilian and Yugovo granite). During the extensional stage, commenced the exhumation of the migmatites in the core part of the dome (36-37 Ma), followed by cooling (35Ma), extrusion of the felsitic rhyolites (30-32 Ma) and ore mineralization (29-30 Ma). Rhyolite magmatism thus postdates the extensional movement by about 3-6 Ma while the hydrothermal mineralization commenced soon after silicic magmatism. The possible trigger for the dynamic development of the hydrothermal system is the beginning of the migmatization, followed by formation of shallow rhyolitic magma chambers resulting in regional heating and increase of the thermal gradient.