Pb-Zn deposit، North of Damghan، Iran

The petrographical studies of carbonate rocks of Jurassic Dalichai and Lar Formations in Ahvanu region (North of Damghan) resulted in recognition and separation of five different types of dolomite including 1- Fine to medium planar dolomite rhombs،scattered in matrix; Rd1; 2- Coarse crystalline، euhedral mosaic dolomite، Rd2; 3- Medium to coarse crystalline، anhedral mosaic dolomites، Rd3; 4- Coarse-crystalline، euhedral to subhedral dolomite cements، Cd1; and 5- Coarse to very coarse crystalline، saddle dolomite cements، Cd2. Rd1، Rd2 and Rd3 dolomite textures are replaced in origin، whereas Cd1 and Cd2 dolomites are commonly as cements. Thin and polished section studies along with field observation indicated that ore is hosted by Rd3 dolomite. δ18O (PDB) and δ13C (PDB) values vary from -4. 95 to -5. 95% (average -5. 53%) and 2. 32 to 1. 68% (average 0. 072%)، respectively. Considering petrography، paragenesis and stableisotope data، the dolomites in the Dalichai Formation of Ahvanu area are interpreted to have been formed in the subsurface during mechanical compaction at shallow to intermediate burial depths. Also، based on minor elements study، calcite is the primary mineral in the studied carbonates.