The granitic gneiss and amphibolite are well exposed in the northeastern Hannan massif, such as the Xijiaba and Jinpen areas. Zircons from these rocks have high Th/U ratios and show oscillatory zoning in the CL images, indicating a typical magmatic origin. Here, we present LA-ICP-MS zircon U-Pb age data for the three plutons, which show crystallization ages of 846±3 Ma, 800±3 Ma and 815±3 Ma, respectively. The situ zircon Hf isotopic analysis demonstrates that the three plutons have significantly variable Hf isotopic compositions with respective εHf（t）ranges at -23～-13, -1～+12 and +6～+10. The zircons from the Xijiaba granitic pluton show Archean Hf two stages model ages（TDM2）at 3.43～2.56 Ga. In contrast, the zircons from the Xijiaba amphibolitic pluton have much younger zircon TDM1 ages between 1.41 Ga and 0.88 Ga. For the Jinpen granitic pluton, the zircon grains also give young TDM2 ages at 1.31～1.11 Ga. The depleted Hf isotopic compositions of zircons from the Xijiaba and Jinpen granitic plutons indicate a significant Neoproterozoic crustal growth developed in this region. Based on Ti-in-zircon thermometer, the crystallization temperature of zircons from the studied granitic plutons ranges from 610 ℃ to 790 ℃. Together with the published data in this region, whole-rock Zr saturation temperatures of granitic magmatic rocks indicate that the formation temperatures of these rocks show a regular variation after time. Three high-temperature magmatic events can be distinguished from this variation. The first event occurred at 897～887 Ma and was recorded by the Xixiang rhyolite and the Xishenba granitic pluton. It was likely related to the underplating of the coeval Liushudian ocean island basalt, which was possibly produced by a ca. 900 Ma mantle plume. The second event happened at 817～760 Ma and was recorded by the Hongmiao granitic pluton and Tiechuanshan rhyolite. This high-temperature magmatic event was likely corresponding to the 820～750 Ma basic intrusions in the Hannan area. It was most likely formed by stretching of a new back arc basin. The third event took placed at ca.707 Ma and verified by the Xixiang syenogranite. The contemporaneous basic intrusions were also exposed at the northwestern margin of Yangtze block. They were all generated in an extension setting after arc-continent collision in the Micangshan and Hannan regions.
Zhu Xi Long Xiaoping Yang Xiaoxiao Wang Jingyu. The formation temperature of Neoproterozoic magmatic intrusions in the Hannan area and its geological significance[J]. Chinese Journal of Geology, 2018, 53(3): 1000-1026.