DISTRIBUTION AND GENESIS OF SOME EPIZONAL ZN-PB AND AU PROVINCES IN THE CARPATHIAN-BALKAN REGION

Zn-Pb-rich low-sulphidation epizonal vein and replacement deposits in the Drina-Rhodope and Inner Carpathian mineral provinces of central an d eastern Europe coincide with belts of predominantly calc-alkaline an desitic rocks. The generation of these volcanic rocks in continental m argin or island arcs by the subduction of oceanic lithosphere can expl ain the major palaeomagnetic rotations of Tertiary age in the region a nd the sinuous shape of the Carpathian chain. The world-class Au-rich South Apuseni epizonal district is best regarded as part of the Inner Carpathian are but with an ophiolitic rather than a metamorphic 'conti nental' basement. Recent age determinations and geophysical data from the Baia Mare district of the Inner Carpathian are suggest that minera lization succeeded volcanism by one to two million years and accompani ed crustal extension and cooling of a large, mushroom-shaped pluton, t he boundaries of which define the mineral district. In the South Apuse ni Au district, as in most of the Pacific margin arcs, the epizonal Au mineralization can be speculatively explained by mixing of meteoric w ith low-salinity metamorphic water that was expelled during the intrus ion of mafic rocks in the lower or middle crust. In the Drina-Rhodope and Inner Carpathian provinces the abundance of Zn-Pb relative to Au i s best explained by the cratonic nature of the underlying crust, which precluded an input of low salinity, Au-bearing metamorphic water. The Zn-Pb deposits formed where convecting meteoric water mixed with sali ne water that was possibly introduced through carbonate rocks in the b asement. The more continental or cratonic crust in the Drina-Rhodope a nd Inner Carpathian arcs relative to that in the Pacific margins and, hence, the much greater proportion of Pb + Zn to Au within the epizona l systems reflect the successive detachment of continental margin arcs from the former cratonic interior of northern Gondwanaland and their accretion to Eurasia.