Precambrian crust growth and reworking of the eastern Yangtze Craton: insights from xenocrystic zircons in the lamprophyres from the Middle–Lower Yangtze Belt, China

Abstract

Continental mafic igneous rocks and their xenocrysts provide information on the evolution of deep continent. Here we present new in situ U–Pb and Hf–O isotopes data for xenocrystic zircons discovered from the Late Mesozoic ultrapotassic to K-rich lamprophyres (150 ~ 140 Ma) in the eastern Yangtze Craton to address the poorly understood yet critical issue about the nature, age and evolution of the regional continental crust. The zircon xenocrysts define episodic distribution of Precambrian ages at 2.61 ~ 2.50 Ga, 2.47 ~ 1.63 Ga, 1.13 ~1.00 Ga and 0.88 ~ 0.73 Ga, with two-stage model ages of Hf isotopes ranging from 3.19 to 1.61 Ga. The presence of Archean and Paleoproterozoic xenocrystic zircons reveal that the deep crust is probably older than the surface exposures (≤ 1.0 Ga) and the Archean–Paleoproterozoic crustal materials maybe widespread in the eastern Yangtze Craton. Hf–O isotopes of the studied Paleoproterozoic and Neoproterozoic xenocrystic zircons, as well as other contemporary xenocrystic zircons from late Mesozoic igneous rocks in the literatures, record the important crust growth and reworking in the eastern Yangtze Craton. The lamprophyres and their xenocrysts provide an important proxy archive of the history of deep continental crust in the eastern Yangtze Craton.