3: Geochronology and geodynamics of Late Cretaceous magmatism and Cu–Au mineralization in the Panagyurishte region of the Apuseni–Banat–Timok–Srednogorie belt, Bulgaria

Abstract: The Apuseni–Banat–Timok–Srednogorie (ABTS) belt, Europe''s most extensive belt of calc–alkaline magmatism and Cu–Au mineralization, is related to the subduction of the Tethys ocean beneath the European continental margin during the Late Cretaceous phase of the Alpine–Himalayan orogeny. Economic deposits are restricted to certain segments along the belt, and all major porphyry-style and high-sulphidation ore deposits in Bulgaria are aligned on the Panagyurishte corridor, a narrow zone obliquely crossing the ABTS belt. This paper reviews the geology, geochemistry and geochronology of igneous and hydrothermal events along this corridor, in a profile extending from the European continental basement in the north to the accretionary complex of the Rhodopes in the south. Extensive U–Pb dating of zircons from subvolcanic intrusions and major plutons, supplemented by published age data for magmatic rocks and hydrothermal ore deposits obtained by other methods, reveals a general younging of magmatism from ca. 92 Ma in the north (Elatsite) to ca. 78 Ma in the south (Capitan Dimitrievo). Cu–Au deposits are restricted to the northern and central parts of the profile (ranging in age from ∼92 to ∼86 Ma), while the southernmost part exposes more deeply eroded mid-crustal plutons devoid of economic mineralization. The age progression correlates with a north-to-south geochemical trend of decreasing crustal input into mantle-derived magmas. Magmatism and ore formation in individual magmatic–hydrothermal complexes along the profile is much shorter lived. For example, subvolcanic intrusions and porphyry Cu–Au mineralization at the Elatsite deposit and andesitic volcanism and high-sulphidation Au–As–Cu mineralization at Chelopech all occurred within a time span of about 1 million years. The age progression of calc–alkaline magmatism within the Panagyurishte region, Bulgaria, from north to south is explained as a consequence of slab retreat during oblique subduction. This led to transtensional block faulting and subsidence, and thus to the preservation of near-surface magmatic–hydrothermal products, including economic Cu–Au deposits. Accretion of continental fragments in the Rhodopes south of the ABTS belt led to greater uplift of the youngest Late Cretaceous intrusions. This removed any ore deposits that might have been formed in this area. [Copyright &y& Elsevier]