2007; Oh et al., 2005, 2006b; Seo et al., 2010). Previously, the GMhad been considered to be mainly composed of Paleoproterozoic andArchean metamorphic rocks, and there was no tectonic event after thePaleoproterozoic metamorphic events until the Jurassic Daebo orogeny,which is associated with the intrusion of Jurassic Daebo igneous rocksand local deposition of the Daedong system sedimentary rocks. However,recent studies have found the following new geological events and vari-ous rocks from the GM: an extensive distribution of the Paleoproterozoicigneous-origin granitoid was confirmed in various areas of the GM (Leeand Cho, 2012and references therein;Yengkhom et al., 2014a; Leeet al., 2014), and the Permo-Triassic igneous and metamorphic activitiesrelated to the continental collision event between the NCC and SCC werebroadly recognized in the northern GM (Choi et al., 2009; Kim et al.,2011c; Oh et al., 2005, 2006a, 2006b; Peng et al., 2008; Seo et al., 2010;Williams et al., 2009). Furthermore, igneous and metamorphic activitiesduring the Neoproterozoic and the middle Paleozoic were also confirmedin the GM (Kim et al., 2006, 2011b, 2013; Oh et al., 2009, 2014; Park et al.,2014a), and the existence of sedimentary rock from the middle Paleozoic(ca. 420–380 Ma) was suggested based on geochronological evidence(Cho, 2014; Choi et al., 2008; Jeon et al., 2007). The possibility that theGM was not a single block before the Permo-Triassic continental collisionis supported not only by the Permo-Triassic Hongseong–Odaesan colli-sion belt but also by the Neoproterozoic and middle Paleozoic geologicactivities in the arc tectonic setting reported from the GM.