Granitoid formation time in the Main Kolyma Batholith Belt: Coordination of geological data and isotopic dating results (Northeast Asia)

Resumo

It is shown that the granitoids of the Main Kolyma Batholith Belt do not penetrate into the Upper Jurassic deposits of the Yana–Kolyma mesozoids. The applicability of U–Pb SHRIMP zirconometry to the Mesozoic period of geological history is subject to critical analysis. It is concluded that analytical limitations preclude the solution of the concordance–discordance alternative of the obtained datings in the Mesozoic U–Pb isotopic systems by computational approaches. The U–Pb isotopic system is established as highly sensitive to the superimposed processes. Based on the reconciliation of the U–Pb, Rb–Sr, Ar–Ar, and K–Ar geochronometric data, the granitoids of the Kolyma Main Batholith Belt intruded 170–160 Ma ago, while their isotopic systems were transformed 150–140, 135–125, and 100–80 Ma ago. The local SHRIMP zirconometry combined with other isotopic methods can be applied to date igneous rocks by the relic dates, to set the time of intrusion into their isotopic systems, and to predict thermal events not identified yet. The U–Pb SHRIMP zirconometry should not be considered as arbitrary.