Skarn zonation and rock physical properties of the Wondong Fe-Pb-Zn polymetallic deposit, Korea

Abstract

The Wondong Fe-Pb-Zn polymetallic skarn deposit is located in the Taebaeksan Basin, South Korea. This deposit is associated with the Paleocene quartz porphyry and characterized by abundant exoskarn and subordinate endoskarn. A general zonation pattern is developed comprising a proximal reddish-brown garnet-rich zone, a distal greenish garnet ± pyroxene zone, and a wollastonite-rich zone at the marble front. The mineralization is characterized by Fe in the proximal garnet-rich zone and Pb-Zn within and beyond the garnet ± pyroxene zone. In general, skarn deposits show complex geophysical signatures in their rock properties in relation to metasomatism. Garnet-rich and garnet ± pyroxene skarns accompanying Fe-oxides and sulfides are significantly denser (3.3–3.4 g/cm3) than the other rocks (2.5–3.0 g/cm3) such as quartz porphyry, wollastonite-rich skarn, and silicic hornfels. Reactions related to creating garnet may increase porosity, which promotes further infiltration and reaction to produce garnet growth. The porosity of skarn rocks (1.8–8.4%) has a broad range and is generally higher than the other rocks (0.8–3.3%). In contrast, most skarn rocks show a remarkably low electrical resistivity (mostly 211–848 Ωm) than the other rocks (1,815–8,601 Ωm). Magnetic susceptibilities of skarn rocks (15–140 × 10–5 SI) are higher than quartz porphyry and siliceous hornfels (<25 × 10–5 SI). P wave velocities in the garnet ± pyroxene zone at the skarn front show lower values (1,487–3,674 m/s) than the other rocks (2,902–5,590 m/s), which is likely related to the porosity of the rocks. Thus, in general, the physical properties of rocks as exampled above from the skarn environment reflect their mineral assemblages and can be used for mineral exploration of skarn deposits.