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The Bangong Lake ophiolite is located in the westernmost part of the Bangong Lake-Nujiang River suture zone. It is a tectonic mélange consisting of numerous individual blocks of peridotite, pillowed and massive lavas and mafic dykes with SSZ-type ophiolitic geochemical affinity formed at the end of a Wilson circle. The SHRIMP U-Pb ages of the co-magmatic zircon domains from one gabbroic dyke (Sample 01Y-155) range from 162.5±8.6 Ma to 177.1±1.4 Ma with an average of 167.0±1.4 Ma (n = 12, MSWD = 1.2), suggesting that the subduction of the Bangong Lake Neo-Tethyan Ocean started before the Middle Jurassic. It is inferred that the tectonic transform from spreading to subduction of the Neo-Tethyan Ocean began before the Middle Jurassic in the Bangong Lake area. [ABSTRACT FROM AUTHOR]

Presents an analyzation about the use of the in situ zircon U-Pb dating method of LA-ICPMS. Consideration of the investigation of a 31 Ma old SHRIMP U-Pb age of the Yongsheng nepheline syenite from southern Jilin Province under different spot sizes; Reference to how the obtained ages are comparable with that of SHRIMP in both accuracy and precision; Findings that the age is also identical to that of the Yinmawanshan gabbro from the Liaodong Peninsula within error; Trend for both the Yongsheng nepheline syenite and the Yinmawanshan gabbro to represent the youngest known exposed intrusions in northeastern and even eastern China; Indication from the results that the Eocene mantle-derived magmatic underplating, and the rapid crustal uplifting of this region since 30 Ma; How the analyses also document extremely high LREE concentrations and relatively flat REE patterns for the zircons from the Yongsheng nepheline syenite, which represent a new type of zircon REE pattern.