SHRIMP Ion Microprobe Zircon U—Pb Age and Sm—Nd Isotopic Characteristics oof the NE Jiangxi Ophiolite and Its Tectonic Implications

摘要

The new SHRIMP zircon U-Pb isotopic study suggests that the crystallization age of a highly fractionated magma in the NE Jiangxi ophiolite suite is 968±23Ma,Re-calculated Sm-Nd isochron age of 955±44Ma is within analytical errors,consistent with the zircon U-Pb age.With the exception of two anomalous Sm-Nd data,the remaining 15 analyses so far obtained for the ophiolite gave εNd(T) values falling into a limited range from +4.3to+6.7,indicating that the ophiolite was derived from a felatively strongly depleted mantle source.Sm-Nd isotopic systematics in some samples may have been strongly affected by post-magmatic events.such as alteration,deformation and metamorphism,resulting in anomalous εNd(T)values.Combined with published 40Ar-39Ar age data,it can be concluded that the collision between the Yangtze and South China Blocks occurred during 0.97-0.80Ga.