Abstract:

There are many intermediate-acid intrusive rocks in Quanji area. In order to better understand of the characteristics,
intrusion age, and formation environment, we have studied the geology, geochemistry, and geochronology of intermediate-acid intrusive
rocks in Quanji area. LA-ICP-MS zircon U-Pb results show that the intrusion age of granitoid rocks is 430~455 Ma, indicating that
magmatic intrusion took place in different phases during Late Ordovician to Early Silurian in the study area. U-Pb age data show that
the granodiorite was formed at 444±11 Ma, i.e., late Ordovician. Thus, the Balonggonggaer Formation should be earlier than the Late
Ordovician. Geochemical characteristics show that granitoid is rich in K and excessive in Al, enriched in LILE(Rb, K and Ba) ,
depleted in HFSE (Nb,Ti and P) with a weak negative europium anomaly. Diorites are rich in K, and quasi-aluminous and have a
negative europium anomaly that is not obvious. Granite and granodiorite have a weak europium negative anomaly. Quartz diorite is not

obvious. Intermediate-acid intrusive rocks have characteristics of continental collision in terms of formation environment. Based on
regional tectonic setting and previous research results, we infer that intermediate-acid intrusive rocks were produced in a subduction or
collision setting during the Caledonian orogeny from Late Ordovician to Early Silurian.

Key words: intermediate-acid intrusive rocks, LA-ICP-MS ziron U-Pb dating, geochemistry, geochronology, Quanji