Importance of clay minerals in Jordan case study : volkonskoite as a sink for hazardous elements of a high ph plume

الملخص EN

Among the most potential clay deposits in Jordan are kaolinite, bentonite, and palygoskite, volkonskoite, illite, and black mud.

A novel geopolymerization process has been recently developed by activating local raw kaolinite to produce green building materials.

The clay mineral volkonskoite, a unique green earthy smectite, is widely distributed in central Jordan and is associated with yellow uranium vanadate minerals.

Volkonskoite is hosted by altered marble and quaternary thick travertine and recent calcrete deposits.

The green clay occurs as thin layers, encrustations and fillings in voids and cavities.

The Cr2O3 content of the ignited smectites in the new localities ranges between 18.88 % and 28.28 %.

The following are the structural formulae (oxygen = 11) calculated from the microprobe spectral results with the highest and lowest Cr+3 content : Ca0.22Na0.03 (Cr0.8Al0.89Mg0.3) (Si3.92Al0.08) O10 (OH) 2 and Ca0.22Na0.12 (Cr1.35Al0.4Mg0.25) (Si3.68Al0.32) O10 (OH)2.

The green clay has uninterrupted continuous flaky texture that confirms their chemical origin.

Most of the travertine caps the varicolored marble zones that were discharged of hyperalkaline ground waters in the past.

The varicolored marble (combusted bituminous marl) from central Jordan was altered by the circulating hyperalkaline waters that dissolved Cr3+ with other redox sensitive elements, and that was immobilized in Cr-rich smectite–volkonskoite solid solution series.

Such waters are similar to the present day active hyperalkaline seepages (pH ~ 12.7) in Maqarin area, north Jordan.

The authigenic volkonskoite was formed at a pH similar to the alkali disturbed zone expected at radioactive waste repositories.

The Jordanian sites provide the best currently known localities to examine the processes associated with the long-term behavior of radwaste repository sites.