Deciphering Magmatic Evolution through Zoned Magmatic Enclaves and Composite Dikes: An Example from the Late Cretaceous Taejongdae Granite in Busan, Korea

Abstract

Late Cretaceous granitic intrusions are common in the southeastern Korean Peninsula. Most of these intrusions enclose abundant microgranular enclaves (MEs) and dikes of almost identical age to their plutons. The granitic intrusion in the Taejongdae area encloses a distinct type of enclave known as zoned MEs. The zoned MEs in this region are composed of multiple zones originated from different magmas that have the same origin and age. Several petrological, mineralogical, geochemical, SHRIMP U-Ph age dating, and Lu-Hf isotopic studies have been conducted for the Taejongdae granitoid to identify how different magmas have interacted and formed the zoned MEs. In this chapter, we reviewed previous studies and added some new data to give a comprehensive picture of the Taejongdae granite and emphasize the importance of zoned enclaves and composite dikes in determining the genesis and evolution of granitoids. We interpret that the MEs distributed in the southeastern part of the Korean Peninsula with the age of 75–70 Ma might be closely related to the breakdown of the subducted Izanagi oceanic slab under the Eurasian plate. This tectonic process enhanced the input of new primitive magma into granitic magma chambers and, therefore, restricted the mixing or mingling process, forming the zoned MEs.