Latest Zircon U-Pb Geochronology of the Qingshan Group Volcanic rocks along the Tan-Lu Fault Zone of Shandong Province, Eastern China

Objective Shandong Province is divided into two parts by the Tan -Lu fault zone： the western part （Luxi） and the eastern part （Jiaodong）. Large-scale volcanic activity occurred during the Late Mesozoic in Shandong Province, eastern China （Fig. lb）, and was controlled by the Tan-Lu fault zone and its secondary faults. Mesozoic volcanic rocks in Shandong Province mainly occur within the Cretaceous Qingshan group, overlying the Laiyang group and underlying the Wangsi group. The Qingshan group has been divided into four volcanic cycles, i.e., the Houkuang, Bamudi, Shiqianzhuang and Fanggezhuang formations from the oldest to the youngest. Although geochronology data indicate the volcanic activity occurred during the Early Cretaceous, the starting time and duration of volcanic activity are still equivocal. Two zircon U-Pb ages of volcanic rocks from strata at the lower base of the volcanic sequence along the Tan-Lu fault zone were reported in this paper, which provide new evidence for the discussion of the geological age.