LA-ICP-MS Zircon U-Pb Isotopic Dating: Constraints on the Time of the Daoxiang Formation in North Fujian Province

Although there is poor outcrop in the area, the Daoxiang formation exposed in North Fujian has unique rock assemblage and metamorphism, and deformation characteristics show that the Daoxiang group does exist, and belongs to metamorphic rock of the Cambrian period in previous research with Sm-Nd model age as (500±35) Ma. However, the limitations of the test method, adversly influence the the reliability of the formation age. LA-ICP-MS U-Pb dating provides reliable and precise evidence of the formation age of the rocks. Zircon LA-ICP-MS U-Pb data of basalt and siliceous rocks carried out by this group show that the newest age of basalt is (111.4±2.0) Ma, i.e. belonging to Early Cretaceous, which represents the lower limit of the formation age. The result is consistent with that of siliceous rocks, the newest of which is 124 Ma. The inherited zircon ages indicate proterozoic-paleozoic-mesozoic materials may be included in the source region, so the Daoxiang formation should be further disintegrated, the Vesicular basalt and Siliceous rocks which formed at Mesozoic should be separated from the Daoxiang formation. The discovery of all these ages enriches research work of tectonic evolution of Daoxiang formation and provides valuable data of the isotopic geochronological age.