CONSTRAINTS ON THE TIMING OF EVENTS IN THE MULTI-EPISODIC HISTORY OF THE TEPLA-BARRANDIAN COMPLEX, WESTERN BOHEMIA, FROM INTEGRATION OF DEFORMATIONAL SEQUENCE AND RB-SR ISOTOPIC DATA

Rb-Sr isotopic systems of muscovite-plagioclase pairs and of biotite f rom a pegmatite emplaced into polyphase deformed schists showing Barro vian-type mineral assemblages yield ages that constrain the timing of three episodes in the Tepla-Barrandian complex in the Bohemian Massif of the western Czech Republic. (1) Muscovite-plagioclase ages of 502 /- 4, 501 +/- 4 and 500 +/- 3 Ma are considered to represent cooling t hrough ca. 500 degrees C after a rapid crystallization of pegmatite wh ich is part of widespread granitic magmatism in late Cambrian times; a ges of 492 +/- 3 and 491 +/- 3 Ma are interpreted as reflecting very l imited opening of the isotopic systems. (2) A biotite age of ca. 373 M a is interpreted as giving a mid-Devonian (Givetian) time of foliation development in the pegmatite, and foliation reactivation in the host rocks, during a tectonothermal event at an early stage of the Hercynia n episode. (3) The age of pegmatite emplacement gives an upper (younge r) age limit for the polyphase tectonothermal episode (interpreted as the Cadomian episode) during which the regionally expressed Barrovian zones in the Tepla-Barrandian complex were developed. The ages are lin ked to specific events in the field-based structural-metamorphic-igneo us sequence of events that constrains their relative order of formatio n in the overall geological history of the Bohemian Forest tectonic do main.