ANALYSES OF PALYGORSKITES AND ASSOCIATED CLAYS FROM THE JBEL RHASSOUL(MOROCCO) - CHEMICAL CHARACTERISTICS AND ORIGIN OF FORMATION

The ''Formation Rouge'' from the Jbel Rhassoul in Morocco is composed of detrital sediments which have a lacustrine origin. The clays contai ned in the less than 2 mum fraction of the sediments are detrital phen gites and illites, illite/smectites or smectites, and palygorskite. Du e to the presence of well preserved long fibers, the palygorskite coul d not have been transported. They are authigenic and must have formed directly by precipitation from solutions rich in Mg and Al. The detrit al illites are impoverished in K and tetrahedral Al. The illite/smecti tes or smectites, on the contrary, are K-rich but have a low tetrahedr al charge. They are also richer in Mg and Fe and have a different crys tal size, composition, and crystallinity from the illites. They most p robably formed by crystallization, similar to the palygorskites, direc tly from the solution. The Al could have been provided by the detrital illite, which may have been unstable in an alkaline environment and r eleased K and Al to the solutions.