A DISCUSSION ON GEOCHRONOLOGY OF THE PROTEROZOIC OPHIOLITE

The best method for determinating the rock-forming age of the Proterozoic ophiolite is isotopic geochronology. The Proterozoic ophiolite may be mostly affected by multistage thermal-tectonic events. The study of geochronology must be based on the single-grain zircon UPb dilution or Pb-Pb evaporation method, and must distinguish the zircons between magmatic crystallization and metamorphic re-crystallization on the concrete operation. Multiexplanation is characteristic of Sin-Nd, Rb-Sr and Pb-Pb isochron ages. So they are unsuitable for studying the geochronology of the Proterozoic ophiolite. The explanation of their geological significances must rely on the tectonics and geological-geochemical characteristics of the Proterozoic ophiolite.