Structural and geochemical studies on amphibolite and greenschist-facies rocks in the Kulidjik river valley, eastern Rhodope, Bulgaria: preliminary results

摘要

The paper provides preliminary structural and geochemical data on high-grade basement and low-grade Mesozoic rocks that crop out along the Kulidjik river valley in the eastern Rhodope, southern Bulgaria. Structural analysis highlights separate tectonic events. An early event in greenschist facies with top-to-the NE ductile shear is recorded in low-grade rocks, followed by amphibolite facies top-to-the SW ductile shear in structurally overlying basement allochthon of the Kulidjik nappe. This shear deformation is attributed to the mid-Late Cretaceous, southward and synmetamorphic thrust stacking in the Rhodope, whereas deformation of low-grade rocks reflects NE-directed tectonic emplacement during a Late Jurassic-Early Cretaceous subduction-accretion processes. Petrologic and geochemical data indicate that greenschists have bimodal IAB and MORB or at least transitional to MORB affinities with strong are imprint. This suggests their origin in suprasubduction arc/back-arc tectonic setting.