Study On The Chuncheon Nephrite Deposit,Korea

The Korean Chuncheon nephrite from mountain area of Chuncheon in Gangwonprovince, South Korea is a new kind of nephrite that appeared in China market recently.It is usually called ‘the Korean nephrite’ or ‘Chuncheon jade’, and is often referred toas ‘Han Guo Liao’in the Chinese Jade market.In order to find out mineralogical and gemological characteristics、the mineralizations、paragenetic relationship of associated minerals and the genesis, thesystematic study was conducted by using the conventional methods. About16polishedthin sections that have a different color and the distinct mineralized zones were used formicroscopic observation、EPMA works and Infrared spectroscopic measurements. Theresults of study on the Chuncheon nephrite are briefly summarized as follows.The Chuncheon nephrite mainly consists of an aggregate of cryptocrystalline andfine-crystalline tremolite, followed by diopside、serpentine、clinochlore、dolomite、calcite、apatite and iron oxide mineral. The content of tremolite is about98%。Under the polarizing microscope, the main texture is crystalloblastic texture such asmicroaphanitic felt-like ballistic texture、fibrous texture、sheaf texture、radial blastictexture、leaflike texture、porphyritic texture and mixed texture. In addition, themetasomatic pseudomorphic texture、secondary filling texture、cataclastic texturegenerally exist in the Chuncheon nephrite samples.The Chuncheon nephrite belongs to the contact metasomatic deposit of intermediate-acid granite and dolomitic marble. The process of mineralization is divided intothree stages, that is, the depositional stage of dolomite�'the regional metamorphicstage of dolomite�'the thermal metasomatic stage of dolomitic marble which isdivided into three sub-stages. Under the influence of these mineralization, Chuncheonnephrite deposit had district zoning structure. The mineralized zone is grouped intomarble zone/coarse-grained and fine-grained calc-silicate zone/nephrite zone. Thenephrite zone is formed by three sub-stages of polymetasomatism. Overall, the paragenetic minerals are formed under the process of retrogressive transition fromdiopside via tremolite and serpentine up to clinochlore. The paragenetic associationand sequence of paragenetic and associated minerals is as follows.(1) The formation of granular dolomite、early stage of calcite、unknown mineraland apatite.(2) The formation of phaneritic diopside、phaneritic tremolite or serpentine withlate stage of calcite. (3) The formation of fine-grained diopside、fine-grained tremolite or serpentinetogether with minor amounts of calcite and clinochlore(4) The formation of microaphanitic tremolite with minor amounts of diopside、the last stage of calcite、clinochlore and iron oxide mineral.In comparison with several nephrites from different provenances, the geological background and genesis of Korean Chuncheon nephrite is very close to the nephrites fromHetian(Xinjiang Province), Geermu(Qinghai Province), Liyang(Jiangsu Province) andXiuyan(Liaoning Province), which belong to the contact metasomatic deposit with taking dolomitic marble as a parent rock. Absence of talc that is easily found in the metasomatic nephrite deposits resulted from a rapid diffusion of Mg-rich fluid. The enrichment and activation of Mg2+and Al3+in the fluid resulted in the crystallizaion of clinochlore.