Alteration, mineralization, geochemistry and fluid inclusion studies in Chah Noghreh Pb-Zn deposit, NW Birjand, Lut Block

The Chah Noghreh is a part of volcanic-intrusive zone of Lut block and is located in southwestern of Seh Qaleh city in South Khorasan province. The area comprises outcrops of Eocene volcanic rocks (rhyolitic to dacitic tuff breccia, andesitic tuff breccia and andesite), which was intruded by subvolcanic unit with pyroxene diorite porphyry composition. The mineralization as vein type (with trending NW-SE) with breccia and open space filling textures was formed in four stages, including: (1) quartz-sulfide, (2) barite-sulfide, (3) calcite-sulfide and (4) dolomite- sulfide. Alterations of argillic, silicification, calcite and dolomitization were formed in margins of vein with linear trend. Hypogene sulfide minerals in veins contain galena, sphalerite, fahlore and pyrite. Due to the influence of oxidation processes on the primary ore, secondary minerals of cerussite, anglesite, rhodochrosite, covellite, malachite, hematite and goethite are developed. Maximum geochemical anomalies of veins decrese from lead (158000 ppm) to zinc (25507 ppm) and copper (1295 ppm). Microthermometric measurements show temperatures of 210 to 281, 195 to 225 and 145 to 180ºC and salinity of 16.8 to 19.2, 11.7 to 17.2 and 13.4 to 15.8 NaCl wt. % equivalent, respectively. Temperature decreasing, mixing between magmatic derived hot and saline ore fluids with cold and low saline meteoric waters and boiling lead to the metal deposition. Based on evidences such as structurally controled mineralization, type of alterations and heir linear expansion, simple mineralogy of ore, depth of formation (700 meter) and thermometry data, Chah Noghreh deposit seem to be similar to lead-zinc epithermal deposits.