The Sedimentary Environment of Attapulgite Clay Deposits on the Border of Jiangsu and Anhui Provinces

Key words: 
• attapulgite clay /
• sedimentary environment /
• medium condition

Abstract: The Sedimentary attapulgite clay deposit on the boder of Jiangsu and Anhui Provinces is an important producing area of attapulgite clay in China. Ore-bearing Series is a set of sedimentary clastic rocks of shallow lake. The sedimentary medium features are as follows: 1) Various attapulgite clays have different pH values, all of them are formed in an alkalic condition; 2) According to the features and Ceanom calculated values of variant clays, the attapulgite clays are formed in a reducing condition, and part of montmorillonite clay is formed in a weak oxido-condition; 3) On the basis of stable isotopic compositions of opal and dolomite, opal-forming temperature is 71℃ 81℃ and dolomite-forming temperature is 29℃ 74℃.These features with other geochemical characteristics infered that the forming temperature of attapulgite clays is higher than the normal sedimentary temperature; 4) MgO/Al ₂O ₃ Sr/Ba Rb/K ratios of variant attapulgite clays showed that the forming salinity of dolomite attapulgite clay, siliceous attapulgite clay and attapulgite clay is higher than that of montmorillonite clay. To sum up, the study indicated that under the conditions of alkalic, reducing conditions and low salinity of water medium, attapulgite clay deposits could be formed in a shallow lacustrine basin. The hydrothermal solution being related to volcanic action is of certain significance to mineralization of attapulgite clay deposits.