The Āhangarān lead-silver deposit, SE-Malāyer, West Central Iran

Abstract

The Āhangarān Pb-Ag deposit is located 20 km ESE of Malayer in West Central Iran. The area is covered by lower Jurassic slates, phyllites and quarzitic sandstones and lower Cretaceous carbonates. An important sedimentary hiatus (which occurs all over Central Iran) with a disconformity surface separates the Jurassic and Cretaceous sediments. The area is situated on the Sanandaj-Sirjan structural zone which is characterized by NW striking regional metamorphism and volcanism in Mesozoic to early Tertiary time, by plutonism in late Mesozoic to early Tertiary, and by Alpine tectonism in Tertiary to present times. The geometry and geochemistry of the ore bearing units in the Āhangarān area are reported. The ore matter occurs as scattered patches in flat and thin lenses of sandy-dolomite interbedded in the lower Cretaceous carbonates, and as fracture and karst fillings in the same lenses. The ore matter (Pb, Zn, Cu, Fe) may have originated from periodic exhalations, which may have entered the sea water contemporaneous with periodic volcanic activities in the early Cretaceous time (Golpāygān area). It may have been transported by means of sea water to the shore lines. Here the metallic ions were precipitated by biochemical agents as alternating flat sheets within carbonates. Later geologic evolution (tectonic and circulating groundwater etc....) may have recrystallized and/or remobilized locally some of the ore matter to its present position.