Deposits and occurrences of turquoise and variscite in the Republic of Tajikistan

   Background. Turquoise is known to occur in Northern Tajikistan, while variscite is found in Central Tajikistan. Turquoise mineralization is represented by Biryuzakan deposit and four occurrences: Biryuzasay, Shorbulak, Karamazar, Kyzyltash, which are located in the center of the largest mining district Karamazar, on the southern slope of the Qurama Mountains. The turquoise occurrences of Samarkandek and Isfara are situated in the northern branches of the Turkestan Range. Variscite mineralization is located in Central Tajikistan, on the northern slope of the Zarafshan Range, in the upper reaches of the Shing River, on its left side, in the area of a small gold-antimony deposit Chorraga and in the area of a large deposit of Jijikrut. Formation of turquoise and variscite has many common features, thereby allowing them to be considered together as hydrothermal-metasomatic minerals.   Aim. To summarize geological materials, taking into account new data obtained regarding turquoise and variscite in the territory of the Republic of Tajikistan, and to analyze the processes of their formation.   The study focuses on the Biryuzakan deposit and six occurrences of turquoise as well as two occurrences of variscite.   Materials and methods. Rock samples were collected at the Biryuzakan and Chorraga deposits in 2022—2023. Photographic documentation of mine workings and a major regional fault — Biryuzovy Fault — was conducted. A tectonic map of turquoise and variscite occurrences was compiled using literature data. Cartographic, structural, and mineralogical methods were employed for this purpose.   Results. For the first time, the study introduced a geological summary of all known deposits and occurrences of turquoise and variscite in the territory of the Republic of Tajikistan and a tectonic map of their location. A new, hydrothermal-metasomatic formation mechanism is proposed, whereinthe substances for turquoise and variscite (copper, aluminum, and phosphorus) were sourced from host volcanic and siliceous rocks through a lateral-secretion process.   Conclusion. The proposed hypothesis regarding the formation of turquoise and variscite serves as an alternative to existing views shared by many prominent specialists in the field of gemstone geology.

turquoise, variscite, Biryuzakan, Karamazar, volcanic rocks, jasper, lateral-secretion process, hydrothermal-metasomatic genesis