Sm-Nd dating and Nd-Sr isotopic characteristics of the Shimian ophiolite suite, Sichuan Province

By measuring the Sm-Nd and Rb-Sr isotopic compositions of harzburgite and gabbro from Shimian ophiolite suite, we got the whole rock Sm-Nd isochron age of (938±30) Ma (2σ), and the ε_Nd of 7.6±0.8 (2σ), which shows that the ophiolite was formed at the Early Neoproterozoic. The obvious change (0.70209–0.70708) of I_Sr values of the ophiolite is caused by the meteoric hydrothermal alteration. The high ε_Nd values indicate that the primitive magma was derived from the intense depleted mantle reservoir. It is suggested that this area was in a back-arc basin environment during the Early Neoproterozic.