ABSTRACT
The Sukkari gold deposit has a simple mineralogy with major pyrite and arsenopyrite, and minor sphalerite, chalcopyrite and galena. Three generations of pyrite are recognized; large anhedral As-poor pyrite (PI), large euhedral arsenian pyrite (PII) and fine-grained euhedral As-poor pyrite (PHI). Gold occurs either as; 1) anhedral grains (GI) at the contact between As-rich zones within the arsenian pyrite; 2) randomly distributed anhedral grains and along cracks in arsenian pyrite (GII) and 3) large gold grains interstitial to fine-grained PIII pyrite and arsenopyrite. The textural positions of gold indicate strong relationship with arsenic concentration in the environment. At early stage, Au and As were incorporated in the pyrite structure. When the ore fluids attained As and Au saturation, gold was contemporaneously deposited with arsenopyrite. It is suggested that the concentration of arsenic in the ore forming fluids plays an important role in gold deposition in hydrothermal systems.
