Genesis of the Songhung gold-polymetallic deposit in the Hoechang district, the Democratic People’s Republic of Korea: Constraints from Geology, Petrochemistry and Pb–S–C–O isotope geochemistry

Abstract

The Songhung deposit is located in the southwestern part of the Yangdok Uplift Zone (YUZ) in the northern part of the Pyongnam Basin in the Sino–Korean Craton. Most of large– and small–scale gold deposits and occurrences were discovered and exploited in the western part of the YUZ. Several tectonic events in this area are the key to understanding the gold and polymetallic mineralization in the Sonhung deposit. The YUZ comprises the Neoarchean Rangnim Metamorphic Belt, Proterozoic and Early Paleozoic rocks in the central domain, and granitoid intrusions of crustal and mantle derivation (Yangdok granitoid intrusions). Two extensive NNE–trending fault zones with mylonitized rocks are interpreted to represent detachment fault and two NE–SW–trending regional rift structures represent zones of subsidence (e.g., the Tokchon–Maengsan to the west, the Kowon to the east) and the Junghwa–Samdung subsidence to the south. It is suggested that the YUZ is a metamorphic core complex (MCC), similar to those in the North China Craton (NCC).Polymetallic mineralization in the Songhung deposit is divided into early and late stages. The early mineralization was formed during compressional deformation in the Triassic accompanied by low–grade metamorphism of the sedimentary host rocks. Variations in Pb, S, C and O isotope ratios indicate that the ore–forming fluids and metals were derived from the country rocks. The Au grade is insignificant in this style of mineralization. The main gold–polymetallic mineralization in the Songhung deposit is related to tectonic extension of the region; the Pb, S, C and O isotope data indicate that these elements, as well as ore–forming fluids, could be derived from both the granitic intrusion (Yangdok granitoid) and the Proterozoic and Paleozoic country rocks.