First Identification of ∼2.65 Ga Tonalite in the Jiefangyingzi Area, Inner Mongolia.

The article offers a study on zircon U-Pb dating of finegrained tonalite in the Jiefangyingzi area of Chifeng from Silurian Badangshan Formation in order to provide petrologic and chronologic constraints in the Jiefangyingzi area, Mongolia. Topics include collection of samples of tonalite for zircon Laser ablation inductively coupled plasma mass spectrometry U-Pb dating in the area; and conclude that there is a Precambrian basement beneath the Bainaimiao arc belt.