Cenozoic intraplate alkaline volcanism of Western Bohemia

Three independent volcanic suites have been recognised in W Bohemia: (i) th e old unimodal alkaline ol. nephelinite-tephrite (29-19 Ma) in the Ohre Rif t, (ii) two contemporaneous weakly (trachybasalt/trachyandesite-trachyte/rh yolite; 13-11 Ma) and strongly (ol, nephelinite-tephnte/basanite; 12-8 Ma) alkaline series in the flank of the Cheb-Domazlice Graben formed by the Tep la Highland and (iii) the young unimodal ol. melilitite/ol. nephelinite alk aline suite (2.0-0.12 Ma) at the intersection of the above mentioned struct ures in the Cheb Bask. The magmas of all the suites are mantle-derived and, in the case of the Cheb-Domazlice Graben series, associated with the AFC p rocess. Two main fault systems: (i) ENE-WSW and (ii) NNW-SSE are del eloped in W Bohemia, corresponding to the directors of the two prominent taphroge nic structures. The southwesterly continuation of the Ohre Rift across the Marianske Lazne Fault is marked by volcanics only.