MINERAL CHARACTERIZATION OF KAOLINITE DEPOSITS AT NAGAR PARKAR, SINDH, PAKISTAN: A DISCOURSE ON THEIR ORIGIN AND USES

Abstract

The occurrence of kaolinite deposits is either in-situ or due to transportation on a local scale. The Nagar Parkar kaolinite deposits are of the first type and formed due to the alteration of acidic igneous rocks, especially in the low-lying areas. Though, the signatures of alteration have been observed throughout the area but at present the deposits have been reported and mined mostly from the surroundings of the villages namely Chanida-Dhanagaon, Dhedhvero, Parodharo, and Jodhe Jo Wandio. Open pit mining has been carried over decades and, in most cases, the deposits are very shallow occuring at depths of six to seven feet. The XRD results indicate that kaolinite (China clay) is the main mineral constituent of these deposits along with the quartz and minor calcite, goethite and illite. The presence of iron oxide at various zones suggests the oxidation environment. At places, the calcite is also associated with these clays, which indicates the chemical weathering of Ca-Feldspar. In terms of field features, the white colored kaolinite is normally associated with the angular and subhedral grains of quartz along with few strips of iron oxide and minor calcite at various depths and places which indicates that the kaolinite is either primary in origin or traveled a little distance from the source. In terms of origin, different hypotheses are proposed but based on field features and petrographic findings, it is concluded that the kaolinite deposits of Nagar Parkar area are the result of alteration of acidic igneous rocks, especially different varieties of granites and granodiorites rather than the basement rocks. The area covering china clay deposits is either surrounded or very near to the Runn of Kutch; therefore, chemical weathering and hydrothermal processes may be responsible for the formation of these clays. Although globally, there are different uses of kaolinite, but the indigenous deposits of Nagar Parkar are mostly being used for the manufacturing of pottery along with a few other uses