Hypogene kaolin deposits from felsic intrusive rocks (Peninsular Malaysia) with special reference to rare earth elements and stable isotopes geochemistry

Abstract

Clay fractions of the hypogene kaolin deposits from Ipoh granite and Jerai pegmatite are composed of kaolinite, while the greenish kaolin horizon of Ipoh area comprises of illite and kaolinite. Al2O3 and SiO2 are the main constituents in the studied kaolins with very low concentrations of other oxides. K2O occurs in relatively high contents in the illite-rich kaolin that formed by hydrothermal alteration of biotite-granite of the greenish kaolin horizon of Ipoh area. The higher contents of Ba, Cr, Cs, Ga, Rb, Sc, and Sn in the illite-rich horizon are inherited from its source rock. The relative enrichment of light rare earth elements (LREE) over heavy rare earth elements (HREE) as indicated from the high (La/Yb)n ratios and positive correlations between ΣREE and P2O5 in the studied kaolins suggest the occurrence of REE as authigenic florencite, churchite and/or rhabdophane and, therefore, reflect the kaolinitization process rather than the parent rocks. δH and δO values are similar in both Ipoh and Jerai kaolins with dH values range from −84 to −99‰ and positive δO values varying between 0.95 and 5.47%. H- and O-isotopes data fall close to the left side of the kaolinite line in equilibrium with meteoric water at temperatures of > 100 °C. The pronounced negative Eu anomalies, absence of positive Ce anomaly and high crystallization temperature (94–113 °C) indicate the hydrothermal (hypogene) origin of the studied kaolins as a result of the Triassic post-magmatic hydrothermal activities in Peninsular Malaysia. Mineralogical and geochemical variations among the studied deposits although they formed by the same kaolinitization process, suggest a significant role of parent rocks in their compositions.