Mineralogy and trace elements geochemistry of the RoudMajan kaolin deposit, northwest of Torbat-e Heydarieh, NE Iran

The RoudMajan kaolin deposit is located about 35 km northwest of Torbat-e- Heydarieh city, Khorasan Razavi Province, in the Great Kavir Block subzone. Field evidence and laboratories results indicate that this deposit is genetically associated with the alteration of basaltic andesite rocks (Lower Eocene). According to the microscopic evidence and various analytical techniques (XRD, SEM-EDS, FE-SEM, DTA and TGA), kaolinite, illite, haloysite, quartz, alunite and muscovite are the major mineralogical phases and hematite, pyrite, rutile, galena, barite, calcite, biotite, apatite, titanomagnetite and titanium augiteare the minor minerlogical phases in this deposit. Calculations of mass balance of elements with the assumption of Al, as a monitor immobile element, reveal that the development of the kaolinization process of andesi-basaltic rocks in the RoudMajan  has been accompanied with the enrichment of Pb, leaching of elements such as Cs, Rb, Cu, Zn and Sr and leaching and fixation of elements such as Hf, Ba, Zr, V, Th, Ta, Nb, Ga, Cr, Co and Ni. Among the lanthanides, only Ce experienced mass decrease, while others exhibit both incremental and decremental behavior during kaolinization processes. The distribution pattern of normalized REE to chondrite indicates the differentiation and enrichment of LREE from HREE. The obtained results reveal that the behavior of trace elements during the formation of the RoudMajan kaolin deposit is a function of factors such as changes temperature and mineralizing fluid chemistry, differences in alteration intensity, adsorption, scavenging, mineralogical control, and abundance of complexing ions. Correlation coefficients between elements indicate the role of clay minerals, secondary phosphates, rutile, manganese oxides, muscovite and illite in the distribution and fixation of lanthanides. The occurrence of negative anomalies of Eu and Ce in kaolin samples indicates the alteration of plagioclase minerals of primary basaltic andesite rocks by high-temperature fluids and reduction of oxygen fugacity during the development of the RoudMajan kaolin deposit.