MINERALOGY AND GEOCHEMISTRY OF TURQUOISE FROM TIANHU EAST , CHINA

The Tianhu East turquoise deposit is located 180 km southeast of the city of Hami (also known as Kumul) in the Xinjiang Uyghur Autonomous Region of China. This deposit has been mined since as early as 1279-379 BCE. New mining activity took place around 2015, and some of the production emerged briefly on the Chinese market. Mining was subsequently prohibited because of the location's protected status as an archaeological site. The geology of Tianhu East turquoise as well as updated reports and field exploration are systematically summarized in this study. The turquoise usually occurs as blue and bluish green veins in the fissures and shear zones of quartzite in the Cambrian Pochengshan Formation. It is characterized by high lithium, vanadium, chromium, strontium, and gallium concentrations and low barium content. Multiple associated minerals (e.g., quartz, apatite, goethite, hematite, jarosite, bonattite, muscovite, atacamite, svanbergite, and gypsum) were identified using Raman spectroscopy and electron probe microanalysis. This study contains the first report of atacamite in Chinese turquoise. Petrography, mineralogy, and geochemistry of the bedrock as well as the crystallization sequences of the associated minerals are highlighted. Based on the results, the authors propose a supergene weathering origin and elemental derivation for Tianhu East turquoise. Black shale was likely the main original source of the aluminum, phosphorus, and copper necessary for formation, while quartzite provided enough space for precipitation.