The Precambrian Metamorphic Complex in the Rhodope Massif – A Unified Stratigraphic System
Abstract:
The high-grade Precambrian metamorphic complex in the Rhodope Massif is a clearly stratified and unified lithological system, with a relatively well-preserved and recognizable primary sequence. It is divided into two groups with different age and petrographic composition named: Prarhodopian - a lower infracrustal gneiss formation and Rhodopian - an upper Neoproterozoic supracrustal variegated formation. An Ophiolitic association, consisting of serpentinites, amphibolites and metagabbros occupies the lower stratigraphic levels of the Rhodope Group. The dominant structural plan of the complex is folded. Linear and domed anticlinal folds are clearly outlined, which in the Central Rhodope block have a southern vergence. Local tectonic deformations, mainly along the lithological boundaries of the rocks, do not destructively disturb the general stratigraphic sequence. The rock complex underwent three metamorphic changes of different nature and age: 1. general Precambrian regional metamorphism, reaching amphibolite facies, T=480-580oC / P= 5-7 kbar; 2. local HTP geotribometamorphism (eclogitization) in paleoseismic friction zones, Т=800-1200оС / P=12-20 kblar and 3. Metasomatism, due to the penetration of pegmatite-aplite veins - derivatives of granitic magmas. The second and third types of metamorphism occur locally during the Precambrian and Phanerozoic.
