The Role of Neogene Magmatism on Alteration Zones and Supergene Enrichment Porphyry Copper In Darreh Zereshk,Yazd-Iran

Darreh Zereshk site is located about 60 km SW of Yazd.The highest point near this area is the Shirkuh mountain (4060 m) high, a granitic and granodioritic batholith 60-km long and 25 km wide. Mesozoic sedimentary rocks (massive limestones, from Taft formation that cover concordantly the Conglomerate and sandstones from Sangestan formation) have covered it. The intrusive body in the Darrah –Zereshk (Oligocene–Miocene age) is younger than the surrounding metamorphosed rockes and based of its mineralogy has granitic composition. Granitoid rocks alteration let appear the classical zonation of porphyry copper deposit with siliceose and Fe oxid breccia.

The fracturs of metamorphose rocks filled by volcanic dacitic rocks in Neogen.

The amount of Cu in dacitic rocks far from intrusive body is normal average (47& 34 ppm) but it reaches to 6794 ppm, near the intrusive body. Malachite, azurite and chrysocolla, observed on the surface of dacitic rocks also propylitic alteration has spread inside them and considering of Cu amounts seems to be related of absence supergene enrichment. Eruption of Neogene dacitic meanwhile the supergene zone, bring out the metal bearing minerals especially copper and Fe oxids and has destroyed The supergene enrichment.

Also it caused the potasic zone disapear upward and poropylitic alteration expend in volcanic rocks. phylic and argilic alteration spread over a large area and Cu mineralization appear on them. Chalcopyrite have been found as essential mineral of Cu.