Rb-Sr and 40Ar/39Ar Ages of the Adamellite in Sanligang Area
湖北省随州三里岗地区二长花岗岩Rb-Sr、40Ar/39Ar同位素年龄

The Sanligang adamellite is one of the main tectonic blocks of the Huashan ophiolitic melange and has an intrusive contact with the basic volcanic rocks. The determination of the isotopic age of this adamellite can lead to determining the upper limit of the isotopic chronology of the Huashan ophiolitic melange. The ages of the adamellite in Sanligang area were measured by Sm-Nd, Rb-Sr and 40Ar/39Ar methods. The mean age of the model ages tDM determined by 3 samples is 1 064±105 Ma. 12 whole-rock samples present a Rb-Sr isochron age of 422±53(2o)Ma. Hornblende picked out from the adamellite gives an 40Ar/39Ar age of 141.4±0.3 Ma. The results indicate that the age of the volcanic rocks of the Huashan ophiolitic melange is older than 422 Ma.