Abstract:

Honghuapu intrusions in the west segment of Northern Qinling Mountains are dominated by tonalite with medium-fine-granular structure, which carry the geochemic characteristics of subduction-related granitic rocks. Zircons obtained from Honghuapu intrusions can be divided into three groups according to the shapes and CL images. Based on the results of LA-ICPMS dating of zircon U-Pb isotope, we get three ages of (1,765-1±8-4）Ma, (450.5±1.8）Ma and (413.5±1.3）Ma, these ages indicate different formation age of hereditary zircons, magmatic crystallization zircons and metamorphic zircons, which may represent three tectonic-thermal events coincide to Lüliang Movement and Caledonia Movement respectively. Whereas, the age of (450.5±1.8）Ma is the formation age of Honghuapu intrusions and also implies the formation age of Early Paleozoic island arcs in Northern Qinling. These new LA-ICPMS datings of zircon U-Pb have great significance to the study of Proterozoic and Early Paleozoic tectonic framework, evolution and dynamic mechanism of Qinling Mountains.

Key words: Northern Qinling Mountains, Honghuapu intrusions, LA-ICPMS dating, tectonic significance