Nature and significance of the Early Cretaceous giant igneous event in Eastern China

Mesozoic igneous rocks are widespread throughout eastern China, but precise geochronological constraints were previously lacking. Thirty-two samples, including dolerite, diorite and granite, from the Liaodong Peninsula in northeastern China were chosen for zircon U-Pb SHRIMP (5 samples), laser ablation (LA) ICP-MS (22 samples) and TIMS (5 samples) dating. The ages range from 131 ± 2 to 117 ± 7 Ma, which establishes that the Early Cretaceous was a significant period of igneous activity in the Liaodong Peninsula, with a duration of about 10 Ma. A similar magmatic age pattern is identified in other areas of northern and eastern China, and elsewhere in southeast Asia. These rocks were all emplaced in an extensional setting, as indicated by the occurrence of A-type granite, dolerite dyke swarms and metamorphic core complexes. It is proposed that this giant igneous event was related to coeval lithospheric delamination in eastern China, which resulted from Kula-Pacific Plate subduction, possibly aided by major superplume activity associated with global-scale mantle upwelling.