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

The new SHRIMP rircon U-Pb isotopic study Suggests that the Crystallization age of a highlyfractionated magma in the NE Jianxi ophiolite suite is 968±23 Ma. Re-caiculated Sm-Nd isochronage of 955±44 Ma is within analytical ermrs, consistent with the rircon U-Pb age’ Wth the excep-hon of two anomalous Sm-Nd data, the remaining 15 analyses so far obtained for the ophiolitegave swn (T) values falling into a limited range from +4’3 to + 6.7, indicahng that the ophiolitewas derived from a reatively strongly depleted rnanue source. Sm-Nd isotopic systematics in somesamples may have been strongly affected by post-magmatic events, such as alterahon, defonnaonand metamrphism, resuhng in anomalous sNd (T) vafues. Combined with published 40Ar-39Ar agedata, it can be concluded that the collision between the Yangtze and South China Blocks occundduring 0.97- 0.80 Ga.