Mineralogical Study And Original Analysis Of The Agalmatolite Deposits In Fujian, East China

Named as"Shoushanshi"in Chinese owing to its occurrence only in the Shoushan area of Fujian Province, East China, agalmatolite is a kind of famous jade consisting mainly of clay minerals and used to make handiworks by carving and signets by seal cutting. A detailed study has been carried out on the geological and mineralogical characteristics of the agalmatolite deposits in Fujian Province through field geological investigation, naked eye, micropolariscope and scanning electronic microscope observation, and advanced devices analysis. Based on this study, a discussion has been made on the genesis of the deposits.The following are major achievements obtained in this thesis.(1) The agalmatolite deposits in Fujian Province are mainly hosted in the surrounding rocks of rhyolitic crystal tuff lava and rhyolitic crystal tuff.(2) The primary agalmatolite ores can be divided into four main types including dickite, kaolinite, pyrophyllite and illite ones.(3) Microcryptocrystalline, platy and microcrystalline structures are generally observed in the ores. Agalmatolite grains usually occur as pseudohexagonal platy, irregular sheet and imbricate. The distribution of deuterogenic limonite grains in space among other minerals or along tiny cracks as spot or disseminated spot results in the occurrence of some areas of agalmatolite as red or brown purple lumps or patches, leading to increase their economic and aesthetic value.(4) Kaolinite and dickite from our samples have high degree of order, which supports their formation through crystallization of hydrothermal fluid at low temperature.(5) The four types of agalmatolite ores have obviously different loss weight value, temperature range and pattern of dehydroxy endothermic valley, and temperature range of exothermic peak, indicating that their major component is dickite, kaolinite, pyrophyllite and illite, respectively.(6) Silicon material for agalmatolite mineralization is from hydrothermally altered rhyolitic crystal tuff lava and rhyolitic crystal tuff. The hydrothermal fluid for mineralization is mainly from atmospheric water. The mineralogical and isotopic data are consistent with formation of the ore deposits in a reducing environment and at low temperature of 100～150℃.(7) In view of genetic type, the agalmatolite deposits are mainly volcanic hydrothermal deposit, and rarely weathering and sedimentary deposit. All of the data support multiple stages of mineralization for the formation of the deposits.