Geodynamic Implications of Jurassic Ophiolites Associated with Island-Arc Volcanics, South Apuseni Mountains, Western Romania

The South Apuseni Mountains are located in the inner zone of the Carpathian belt. This area is characterized by a complex assemblage of nappes, in which Jurassic igneous associations are well represented. New geological and geochemical data on these igneous associations document the occurrence of Middle Jurassic ophiolites overlain by Late Jurassic calc-alkaline volcanic rocks. The ophiolite sequence is characterized by: (1) an intrusive section mainly represented by small gabbroic bodies showing both layered and isotropic textures, as well as scarce ultramafic cumulates, melagabbros, gabbronorites, and ferrogabbros; (2) a basaltic sheeted dike complex; (3) a volcanic sequence including massive and pillow-lava basalts and rare pillow breccias; and (4) very rare Callovian-Oxfordian radiolarian cherts. Although chemically variable, gabbros show a clear high-Ti magmatic affinity. Basaltic rocks display N-MORB-normalized incompatible-element patterns consistent with the compositions of present-day mid-ocean r...