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Article History Published Online: 25 July 2020 The article consists of two parts. In the first part of the article the geological Structure of the Jalalabad tectonic block is shortly discussed, and the second part covers the geological structure, mineralogy of the country rocks, geochemical characteristics of the talc and its country rock and the genesis of the Khogyani talc deposits in Nangarhar Province have been studied and researched. The talc deposits under investigation are located approximately 75Km southeast of Jalalabad city in Khogyani district of Nangarhar Province. In order to achieve the aim of the research, in addition to field observations and measurements, numerous samples from talc and its country rocks were collected from the study area. These samples were analyzed, using the lab facilities in the Afghanistan Geological Survey, Isan laboratory in Turkey and Shikozan laboratory in Japan. The samples were analyzed for their petrographic, mineralogical and geochemical characteristics and their trace elements’ composition; and bases on these characteristics the quality of the talc has been evaluated. The results show that Talc formation is genetically related to carbonate rocks especially dolomite marble, resulting from the activity of hydrothermal solution and their subsequent metamorphism. The results also show that all talc samples have a monomineralic composition with talc contents approximately 99.1 percent; the presence of harmful and foreign minerals is often counted as nothing. The structure and texture of the majority of studies samples are similar; the structure is massive and the texture is lepidoblastic, which indicate the high pressure in the process of metamorphism. The petrographic and geochemical analysis (using XRF and XRD) of the collected samples suggest that the quality of Khogyani talc is very high, due to its monomineralic composition, brightness, greasy and some other chemical-physical characteristics. As talc is genetically linked to the marble, there are some of the good quality marble deposits in the region. In addition to talc and marble, the area is also rich in magnesite’ deposits, and in some places their reserves has the mining and industrial potential, therefore the area is also rich and interesting for magnesite’ deposits as well.

Mineralogy and Geochemistry of talc deposits in the Khogyani district of the Nangarhar province, Afghanistan