Palygorskites formation

Sepiolite and palygorskite have a rather special composition and seem to be related to specific mineral parageneses. They appear to be stably associated with montmorillonite, corrensite, serpentine, chert, sulfates, carbonates and various salts. They are found in deposits typified by processes of chemical precipitation or solution-solid equilibria (Millot, 1964) and are therefore rarely associated in sediments with large quantities of detrital minerals. Their chemical environment of formation is in all evidence impoverished in alumina and divalent iron. Their frequent association with evaporites, carbonates and cherts indicate that they came from solutions with high chlorinity. 

Transformation and inheritance played important roles in the formation of some large palygorskite deposits of the world the major part of palygorskite was produced by Smectite Palygorskite transformation in shallow marine environment and the rest was detrital palygorskite from the eontinent. In some cases, palygorskite is neoformed by alteration of basalts in an alkaline environment. 

In what natural condition the formation of palygorskite and sepiolite takes place and why ... 

Heystek, H., and E. R. Schmidt, 1954. Palygorskite from Dornboom. Transac. Geol. Soc. 56 99-115. Kerr, F., 1957. Formation of Attapulgite. Amer. Mineral. 22 534-550. 

---