كانه زايي منگنز لايه اي شكل گراب (تيپ كوبا) در واحدهاي آتشفشاني - رسوبي اليگو- ميوسن در شمال خاور طالقان (البرز مركزي )

Garab Stratiform Manganese Deposit in the Oligo - Miocene Volcano - Sedimentary Sequence, Northeast of Taleghan(Central Alborz)

Garab manganese deposit is located at a distance of 185 km, northwest of Tehran (32 km, northeast of Taleghn town) in Central Alborz zone. The Eocene and Oligo-Miocene volcano-sedimentary rocks have a considerable extent in the study area that are restricted to a NW-SE trending belt . With respect to host rock, texture, structure and position in stratigraphic column, manganese mineralization occurs in three horizons in Oligo-Miocene volcano-sedimentary sequence : Stratiform manganese hosted by red lithic tuff (main horizon of Garab manganese- horizon I). Lenticular manganese hosted by tuffic limestone (Garab mine district - horizon II). Laminated and disseminated manganese hosted by reddish-brown lithic tuff (Dehdar horizon- horizon II). Mineralization occurs in stratiform-lenticular orebodies stretching out for about 25 km and showimg massive, banded, laminated, disseminated, colloform, botryoidal and open space filling textures. The ore paragenesis consists predominantly of psylomelane, braunite, pyrolusite, cryptomelane and hausmannite. Fluid inclution studies reveal that homogenization temperatures range between 180 to 190 °C and salinity changes from 18.6 to 23.4 %wt NaCl equivalent. Garab deposit, in comparison with different types of volcano- sedimentary manganese deposits shows broad similarities with the Cuban-type deposits such as tectonic, geological environment, host and associated rock types, geometry, textures, structure and mineralogy. Based on geometry, texture, structure, host rock, ore forming environment, geochemistry and fluid incluion, manganese mineralization in Oligo-Miocene volcano-sedimentary sequence occurs in continental rifting environment and is attributed to volcano-sedimentary activities.