DISTRIBUTION OF GOLD AND SILVER IN THE GREENSCHIST METAMORPHICS OF ZERAVSHAN-GISSAR ZONE (SOUTH TIEN SHAN)

Abstract

We have attempted to study the greenschist rocks of the ZGSFZ in the Tagobikul-Uch Kado-Kumarkh, Sardai Miena-Yagnob-Unzud, Barzangi-Zakhob, Barzangi-Kanyaz, and Dashtikhirson river basins. Au and Ag were determined using atomic-absorption spectroscopy and spectrochemical methods with detection limits of 1 × 10-8 and 5 × 10-8 percent respectively. The control samples analyzed in different laboratories show good reproducibility of results. The results of the analysis show that the concentrations of Au and Ag in the rocks from different areas in the ZGZFZ but practically similar in composition, age and degree of metamorphism are different. The distribution of Au and Ag in the metamorphic rocks of the ZGSFZ indicates that during metamorphism, Au and Ag were removed from the older volcanics and redeposited in the overlying schists of the lower Yagnob formation, which were metamorphosed to the epidote-chlorite-muscovite subfacies of the greenschist facies. But this greenschist reworking of the rocks was not strong enough to remobilize sufficient Au and Ag to form a deposit, but was able to generate some enhanced background values of Au and Ag in the schists of the lower Yagnob formation.