The Role of Carbonate-Host Rocks on the Genesis of Pb-Zn Deposits, Northern Thrust Zone, Kurdistan Region, Iraq .

摘要

Pb-Zn deposits in the Kurdistan Region, northern Iraq, have occurred mainly as a stratabound and open-space filling ore bodies. They are hosted by dolostone and dolomitic-limestone of platform carbonates. The ore deposits at the studied Dure and Lefan areas are respectively hosted by Kurra Chine (upper Triassic) and Bekhme (upper Cretaceous) formations. Pyrite, sphalerite and galena are the major sulfides minerals, but the mineral paragenesis and relative proportions of these sulfides vary from deposit to other. They have commonly been deposited through dissolution/replacement process and/or through void infilling. Homogenization temperatures of primary and secondary fluid inclusions in Dure and Lefan deposits range from 45 oC to 183 oC and from 68 oC to 284 oC, respectively. The salinity is ranging from 13.93 wt% NaCl equiv. to >23 wt% NaCl equiv. in Dure deposit, and from 3.06 wt% NaCl equiv. to 14.57 wt% NaCl equiv. in Lefan deposit. The average δ34S‰ values for sulfide minerals (pyrite, sphalerite and galena) of the Dure and Lefan deposits are -0.8 ‰ and 1.8 ‰, respectively. Sulfur isotope analysis implies that the sulfur in sulfide deposits is originated from a mixture of different sources. The δ13C and δ18O values of carbonate host rocks fall in the range of marine carbonates. Petrographic evidence and stable isotope data with fluid inclusions suggest that Pb-Zn mineralization was caused by deeply circulating high temperature mineralizing fluids (brines) within the source basin or by tectonic processes, which possibly leached metals from either the diagenesis of host rocks and/or the dewatering of deeper buried siliciclastic beds. The studied carbonate-hosted Pb-Zn deposits share many similarities with the Mississippi Valley Type (MVT) deposit.