Introduction Kaolin has been one of the important industrial minerals and is frequently utilized in many aspects of our lives (Bundy, 1993). Kaolin, which comprises predominantly kaolinite, has unique properties such as crystalline morphology, natural whiteness, fine particle size, nonabrasiveness, low surface area, cation exchange capacity, softness, and chemical stability (Kuşcu and Yıldız, 2016). Kaolin deposits have been extracted and mined historically. Kaolin is used as a raw material in the ceramic, paper, paint, rubber, abrasive, and pharmaceutical industries (Murray, 1991; Manju, 2002). Kaolin quality changes from one deposit to another. In this regard, utilization potentials of a kaolin deposit depend on factors such as chemical composition (Al, Si, and iron oxide concentrations) and the color index. Kaolin deposits are found in primary (residual) and secondary (sedimentary) types (Prasad et al., 1991; Murray and Keller, 1993). The kaolin resources of Iran have a wide distribution throughout the country. Hydrothermal kaolin deposits are found at many points, such as the northwest and southeast of the Iranian plateau, while sedimentary kaolin deposits are seen in central Iran and associated with huge sedimentary basins. Hydrothermal alterations caused by Tertiary volcanic activities are observable in many parts of NW Iran (Figure 1). For example, the Tarom-Hashtjin alteration zone is considered as one of the most significant mineralized zones in Iran. This altered zone, which has experienced Tertiary magmatism and volcanism, has a high distribution of metallic mineralizations such as Cu, Pb, Zn, Fe, Au, and Ag and nonmetallic deposits such as kaolin, bentonite, zeolite, and perlite. There are some kaolinized spots in the Tarom-Hashtjin altered zone, with the Kejal kaolin deposit being the most important one having medium-to high-quality kaolin Abstract: The Kejal kaolin deposit, situated in the northwest of Iran, is considered a small part of the Hashtjin hydrothermal zone. The kaolinization process in this deposit has occurred in ignimbritic and volcanic tuff parent rocks in different grades such that severely kaolinized samples can be found in the middle section of the kaolinization profile. Kaolinite is the most abundant clay mineral in the studied samples. Quartz and cristobalite are the main minerals while anatase is the minor mineral of the kaolin samples. Among the major oxides, SiO 2 , Al 2 O 3 , and TiO 2 show the highest concentrations in kaolin samples. The mass change calculations based on Ti show enrichment of Si, Al, Sr, and LREEs and depletion of alkali and alkali earth elements, HREEs, and HFSEs. The evaluation of REEs normalized to chondrite represents the higher concentration of LREEs comparing to HREEs. A remarkable positive Gd anomaly is seen in spider diagrams, which can be attributed to the primary CaO in the composition of ignimbritic precursor and also the Gd release due to the decomposition of Gd complexes and adsorption by clay minerals. The Eu negative anomaly is the other obvi...

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Abstract-We propose a swarm-based optimization algorithm inspired by air currents of a tornado. Two main air currentsspiral and updraft -are mimicked. Spiral motion is designed for exploration of new search areas and updraft movements is deployed for exploitation of a promising candidate solution. Assignment of just one search direction to each particle at each iteration, leads to low computational complexity of the proposed algorithm respect to the conventional algorithms. Regardless of the step size parameters, the only parameter of the proposed algorithm, called tornado diameter, can be efficiently adjusted by randomization. Numerical results over six different benchmark cost functions indicate comparable and, in some cases, better performance of the proposed algorithm respect to some other metaheuristics.