Mineralogy, geochemistry, and genesis of the Garak Baghi kaolin deposit in the northwest of Saveh, Iran

Abstract

The Garak Baghi kaolin deposit is located in Markazi province and in 75 km northwest of Saveh. It belongs to the Iranian central structural zone. Eocene-Miocene igneous rocks consist of dacite, andesite, tuff, and other pyroclastic rocks and acidic to intermediate intrusive rocks covered the area. Based on petrographic studies, the main minerals in the volcanic rocks are plagioclase, K-feldspar, and quartz. The tectonic processes have affected the area and formed the main faults and fractures that developed the hydrothermal alteration. Hydrothermal alteration has produced clay deposit. Clay deposits contain kaolinite, illite, and the residual materials of altered feldspar with impurity phase such as gypsum, calcite, anatase, and iron compositions. The quality of clay soils especially near the fault zones has been reduced by iron composition. Geochemical studies show that the rocks are medium-K calc-alkaline and meta-aluminous. Based on chemical index of alteration (CIA) and chemical index of weathering (CIW) standards, weathering in the Garak Baghi mine is low, and supergene processes have the main role in the formation of clay soils. The source rocks of clay minerals have been enriched with La, Ce, Th, U, and Rb and depleted of Ti, Nb, and Ba. Their geochemical features are strongly affected by parent magma and also the decomposition of feldspar during the alteration process. The chondrite-normalized rare earth element (REE) patterns display a steep decrease from light REE (LREE) to heavy REE (HREE) with Eu and Ce negative anomalies related to hydrothermal fluids. They show a positive anomaly in Tm because of oxidization conditions too. Geochemical studies demonstrate acidic volcanic rocks as a source of clay soils in the area.