Relationship between Granite and Eclogite on the Southern Margin of the Qilian Mountains: Evidence from Zircon SHRIMP Agesof the Aolaoshan Granite

摘要

Zircon SHRIMP ages of the Aolaoshan granite on the south margin of the Qilian Mts. Range from 445?15.3 to 496?7.6 Ma (averaging 473 Ma), belonging to the Early Ordovician. Geochemically, the granite is similar to I-type granite and, tectonically, was formed in an island-arc environment based on relevant diagrams for structural discriminations. Considering also the regional geology, the authors suggest that the granite is part of an ultrahigh-pressure belt on the south margin of the Qilian Mts. And that its formation bears a close relationship to this belt.