A Concentration Mechanism of Gold in Siliceous Deposits Formed from Geothermal Water

Abstract

To elucidate the concentration mechanism of gold into siliceous deposits formed fkom geothermal waters, behavior of AuCY was examined in the presence of aluminum hydroxide. In the presence of NaN03, most gold was taken up by aluminum hydroxide independent of NaN03 concentration. In the presence of NaC1, the amount of gold taken up by aluminum hydroxide decreased with an increase in NaCl concentration. This study indicates that the chemical species taken up by aluminum hydroxide were not AuCY but chloro-hydroxy species, AuCln(OH)4i (n= 1-3), and these were taken up due to the formation of A1-0-Au bonds. The Au(1II) ions taken up were spontaneously reduced to atomic gold. The size of the unit gold particle was in the range between 0.1-1p and the larger particles were formed by aggregation of the unit particles.