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As gold is precious and usually occurs in very small quantities as primary gold in mineralized quartz veins and secondary gold in alluvial deposits, the EPMA turn out to be the perfect tool for characterizing the primary and secondary gold by utilizing the BSE and SE images, EDS and WDS scans, X-ray maps and geochemical datas. The Selinsing Gold mine is one of the most important gold mining areas in Peninsular Malaysia and lies in the western side of the Second Gold Belt of Peninsular Malaysia. This area is an elongated hill that measures 800 m by 400 m and around 150 m high. The central and western parts of this area are composed of tuffaceous metasediments comprising intercalations of calcareous phyllite and quartz mica schist. These calcareous rocks are normally weathered. They are foliated and show green to silky green colours. Bands of conglomerate and limestone are also observed in this metasedimentary sequence. The eastern part of the mine is underlain by dark grey limestone. The rocks are generally striking at 340° to 350° and dipping to the east averaging from 60° to 78°. A large proportion of the rocks have been deformed in shear zones. Gold mineralization take the form of auriferous quartz filling of fracture; parallel, oblique and transverse to the strike of the shear direction of 340° to 350°. As primary gold, they show angular to sub angular roundness and discoidal to sub prismoidal sphericity. Gold (as electrum) in quartz veins are mainly associated with pyrite (FeS2), arsenopyrite (FeAsS), rutile (TiO2), scheelite (CaWO4), PbAs mineral and iron oxides. Gold (Au) composition together with variable quantities of Ag, Te, Cu, Al, Fe and Si shows some variation in this area. The gold (Au) composition from Selinsing Mine tailings ranges slightly from 75.37 wt% to 80.19 wt%. There are two distinctive modal fineness values for tailings gold in this area, namely, 796 and 756. These distinctive modal fineness values suggest at least two different episodes of gold mineralization in the Selinsing Area.
Keywords: EPMA, primary gold, roundness, sphericity, fineness values.
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