Geochronology, magma source, and geochemistry of igneous rocks in the northern Taebaeksan metallogenic region, South Korea

Abstract

Cretaceous igneous rocks are concentrated in the northern Taebaeksan metallogenic region of South Korea, some of which are related to Fe skarns and/or hydrothermal vein Au–Ag deposits. However, detailed studies on the emplacement age and magma source of igneous rocks supplying this metallogenic area are lacking. In this study, we investigated the emplacement age, magma sources, and geochemical characteristics of seven Cretaceous igneous rocks around the ore deposit, comparing them with previous studies. Zircon U–Pb and mica K–Ar age dating indicated that two magmatism events occurred in the Early Cretaceous (~113.7 ± 0.2 to 104.7 ± 0.5 Ma) and the Late Cretaceous (~85.8 ± 1.1 to 77.6 ± 0.4 Ma). Negative ɛHf(t) values (−2.57 to −22.05 approx.) and the calculated (2.55–1.33 Ga) suggested that the magma source of these igneous rocks was derived from the Proterozoic crust. Whole‐rock geochemical data indicated that the northern Taebaeksan igneous rocks are mostly high‐K calc‐alkaline series, enriched in light rare‐earth elements (LREEs) and large‐ion lithophilic (LIL) elements but depleted in high‐field‐strength (HFS) elements. Although igneous rocks in the northern Taebaeksan metallogenic region have broadly similar magma source characteristics, they can be classified into two groups: one comprises Early Cretaceous intermediate rocks, some of which are related to Au–Ag mineralization, whereas the other includes Late Cretaceous intermediate to felsic rocks, related to Au–Ag or Fe mineralization.