The extent of inter-mineral isotope equilibrium; a systematic bulk U-Pb and Pb step leaching (PbSL) isotope study of individual minerals from the Tertiary granite of Jerissos (northern Greece)

Pb isotope equilibrium was reached and retained in the magmatic rock-forming silicates (titanite, allanite, epidote, apatite) in the Jerissos granite. Disequilibrium between the primary minerals and late-stage secondary biotite and K-feldspar implies that fluids accompanying potassic alteration were contaminated by Pb from an external source. It seems likely that host country rocks (ophiolites and metasediments) were assimilated and hydrothermally leached at depth after emplacement of the granite. Titanite gave a near-perfect PbSL isochron, its age of 51 + or - 16 m.y. corresponding with the intrusion age of the Sithonia plutonic complex to the S, and is in line with the conventional U-Pb date of 53.6 + or - 6.2 m.y. from uranothorite.