Oksanga jade mine, Chuncheon City, Gangwon Province, South Koreai

Regional Level Types
Oksanga jade mine	Mine
Chuncheon City	City
Gangwon Province	Province
South Korea	Country

Actively producing nephrite deposit. Unlike most nephrite jade deposits, which are serpentine-hosted, the Chuncheon deposits are related to dolomites.
Chuncheon nephrite deposit is the largest in South Korea with an estimated reserve of 300,000 tons. The deposit is in the form of lenses in the contact zone between dolomitic marble and amphibole schist in the upper part of a biotite schist.
Both the Yonduri Gneiss Group and the Gubongsan Group are intruded by the mesozoic Chuncheon granite and cut off by the northeast–southwest fault to the west. Furthermore, there is no direct contact between the granite and nephrite deposits. Chuncheon granite is a biotite granite that forms two extensive areas to the northwest and southwest of the mine area; however, immediately to the west of the mine, the granite crops out as an unusual vein-like body.
Based on the Th–U–Pb age dating of monazite, the metamorphic age of the northern part of the Gyeonggi Block (located ~30 km northwest of the Chuncheon nephrite mine) is Triassic (245 ± 3 Ma), when the Nangrim and Gyeonggi blocks collided. The K–Ar dating of the Chuncheon granite also suggests a Late Triassic intrusion age of 210.5 ± 5.0 Ma and a cooling age of 170 Ma below the Early Jurassic age of 300 °C. These age data confirm that the Chuncheon granite formed post-tectonically.
The nephrite belt and surrounding rocks are buried in the order (from bottom to top) of light gneiss, white mafic barite, calcite silicate belt, nephrite belt, chlorite belt, hornblende schist belt, biotite schist belt, and light gneiss. The nephrite occurs as lenses that are generally several meters long and up to 1 m thick. The lithologic contacts and the major schistosity trend are mainly east–west, with dips of 35°–50° toward the south.

Other Regions, Features and Areas containing this locality

References