The orogenic gold deposit of Tamilouw – Haya is hosted by slate and metapelitic rocks within Tehoru metamorphic complex. Gold and polymetallic sulfides mineralization at study area is predominantly formed in the form of veins, stockwork and breccia although minor dissemination is slightly appeared in the rock float samples. They are trapped and controlled by NE-SW and NNE-SSW trending geologic structure occurred during orogeny process from Late Miocene to Pliocene. The common ore minerals assemblage at Tamilouw – Haya deposit are dominated by native gold, chalcopyrite, pyrite, sphalerite, galena, pyrrhotite, tetrahedrite-tennantite (sulphosalt), marcasite,realgar, kalininite and arsenopyrite as hypogene minerals and accompanied by covellite, hematite, goethite and malachite as the supergene minerals.
Ore genesis and minor elements study of pyrite, galena, and sphalerite at Tamilouw – Haya was done using 3 methods approach. There were 46 samples used for ore microscopy analysis and 10 samples for SEM-EDX and Micro-XRF analyses to obtain their mutual relationship interpretation and paragenetic sequence. Ore mineral textures showed disseminated textures, simultaneous crystallization (intergrowth), inclusions, replacements, and exsolutions-decomposition textures.
Average content of Co is 0.21 wt. % and Ni is 0.10 wt. % which may reflect the Co : Ni ratio is 2.86 in pyrite. It means that Co content is higher than Ni and indicates that pyrite origin may be related to volcano-hydrothermal, metamorphosed and skarn-hydrothermal type. In comparison with pyrite, the average contents of minor elements in sphalerite shows Fe content is 9.16 wt.%, Ga is 0.99 wt.%, Ge is 0.12 wt.% and log Ga/Ge ranging from < 0.36 to 2.27 wt.%. Moreover, average precious metal contents within galena shows that Au contents
Ore genesis and minor elements of orogenic gold
is < 0.01 – 2.78 wt.% and Ag is 0.12-0.31 wt.%. On the basis of the previous descriptions, high content of Fe in pyrite and sphalerite, Ga > Ge, Co > Ni in pyrite and low content of Ag in Galena indicated that pyrite, galena, and sphalerite from Tamilouw – Haya were formed under high to moderate temperature condition at 5.1-7.6 km paleodepth.
