[en] Prismatic zircons and rounded and anhedral sphenes in gneissic and granitic rocks make linear array in ²⁰⁶Pb/²⁰⁴Pb-²³⁸U/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb-²³⁵U/²⁰⁴Pb, ²⁰⁸Pb/²⁰⁴Pb-²³²Th/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb, and modified (²⁰⁶Pb/²³⁸U)-(²⁰⁷Pb/²³⁵U) isochron diagrams. The average initial Pb isotopic compositions determined on these isochrons are ²⁰⁶Pb/²⁰⁴Pb = 16.93 +- 0.88, ²⁰⁷Pb/²⁰⁴Pb = 15.71 +- 0.15, and ²⁰⁸Pb/²⁰⁴Pb = 39.60 +- 0.87. The ages calculated from the slopes of these isochrons are from 239 +- 3 m.y. to 228 +- 3 m.y. which signify and early stage of metamorphism probably related to granite activity. The multi-stage evolution calculation (up to five stages) of the lead isotopic compositions based on Pb and Sr isotope data supports the idea that the ultimate source materials of granitic rocks are basic volcano-sedimentary materials. The remelting of once formed crystal materials is also a possible mechanism to produce granitic rocks. (J.P.N.)