Composition, origin, and potential industrial applications of REE-rich authigenic kaolinite separate from the Lower Cretaceous white sands, Saudi Arabia

Abdulrahman Aljabbab ¹ Ayman N Qadrouh ¹ Mamdoh S Alajmi ¹ Abdulrahman M. Alotaibi ^1* Hassan Baioumy ² Mazen M Alyousif ¹ Abdulrahman M Bin Rogaib ¹ Mokhtar Fal ¹ Sultan A Alkhammali ¹

• ¹ King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia
• ² Central Metallurgical Research and Development Institute (CMRDI), Cairo, Beni Suef, Egypt

The white sands from the Cretaceous Biyadh Formation, Saudi Arabia are exploited as raw material for glass sand industry and contain about 15wt. % kaolinite. SEM reveals that the kaolinite develops as a blocky, pore-filling cement of euhedral, pseudohexagonal plates ranging from 5-10 µm in width and 10-20 µm in length suggesting its authigenic origin during the late diagenesis.Anatase occurs as very fine grains interspersed among the kaolinite flakes.The authigenic kaolinite is associated with remarkably high concentrations of REEs (average 1126 ppm), Zr (average 1133 ppm), and Li (average 187 ppm). REEs occur as phosphate phase, while Zr is associated with the anatase, and Li is hosted bykaolinite. These high concentrations are probably due to the enrichments of these elements during the diagenesis of the studied kaolinite. . Alteration of the source minerals during periods of subaerial exposure and/or at shallow burial depths due to meteoric water influx is deduced as a possible mechanism for the formation of the studied kaolinite. The supergene origin of the kaolinite is confirmed by the relatively high concentrations of Ti and Ce+Y+La.The geochemistry and large crystal size suggest the potential application of the kaolinite in paper coating and filler. While the high Al2O3 and low SiO2 contents suggests its potential application in the super standard porcelain and sanitary ware. Partial removing of TiO2 will allow its application in the pharmaceutical and cosmetics industries. Additionally, REEs, Zr, and Li can be separated from the white sands as valuable byproducts along with the kaolinite.