Gold exploration in granitoid rocks Taroum area
|Category||Economic geology & mineral exploration|
|Location||21th symposium on geosciences|
|Holding Date||21 May 2008|
The studied area includes part of mountains that situated between Zanjan and Taroum plains. This area has been situated in Taroum 1:100000 sheet and north of Zanjan. Volcanic rocks include the surface of area. Volcanic rocks divided into Kordkandi and Amand member, and batholitic intrusive body have been divided this area in two part, concordance with common trend (NW-SE). Monzonit, granite and granodiorite rocks this area have been situated in the western Alborz from the point of structural geology and sedimentary basins. Oldest sediments in this area belong to the Eocene and Karaj formation, which outcrop more than 400 meters. Youngest sediments have gypsiferous, incompact conglomeratic facies those include the north east of area. Advanced alteration has been observed around batholitic intrusive body, which consists of sericitic, argillic and silliceous alteration. Alteration zones are seen within pyroclastic rocks and intrusive body as sporadic, irregular and small forms. Host rock of batholitic body consists of tuff and lava, that lava compositions are dacitic latite, quartz latite, rhyolite and andesite, those are equivalent with intrusive body. Ore mineralization consists of copper, iron, lead and gold which appear as vein, lenticular and porphyry forms. In the study area have been observed more than 35 copper index and deposit (Cu grade 600ppm ?%18), grade of Pb and Zn more than % 5 grade of gold 500ppb-75ppm and grade of Fe more than % 60 (iron deposits have %8 phosphate that showed rare earth element (REE) anomalies). Gold mineralization source in siliceous vein is related to granite. Paragenesis of gold is chalcopyrite, chalcosine, covelite, malachite, pyrite and iron-dioxide. Gold particle more observed in siliceous gang and chalcopyrite mineral. These particles are amorphous with dimension 1 to 30 micron; meanwhile numbers of gold particles in polished sections are from 1 to 20 particles.