Geochemistry of ore facies and alteration zoning pattern of the Varandan Ba-Pb-Cu volconogenic massive sulfide deposit, southwest of Qamsar
Subject Areas :فایق هاشمي 1 , فردین موسیوند 2 , مهدی رضایی کهخائی 3
1 -
2 -
3 -
Keywords:
Abstract :
The Varandan Ba-Pb-Cu deposit is located in southwest of Qamsar which is part of Urumieh-Dokhtar magmatic-arc zone. Mineralozation occurred as four sub-horizons in the unit1 of volcaniclastics and volcanics (acidic tuff and andesite) of Middle-Late Eocene. Each sub-horizon consists of five ore facies including: 1) stringer zone, 2) vent complex zone, 3) massive zone, 4) bedded-banded zone and 5) hydrothermal-exhalative sediments of Fe and Mn bearing. Main wall rock alterations in the deposits include chloritic-quartz and quartz-sericitic. Alteration zoning is observed in the deposit as chloritic-quartz at the core and quartz-serisitic in the margins of the footwall of the ore sub-horizon. Electron microprob analysis (EPMA) on the chlorite in stringer zones of the second and third sub-horizons show that these chlorites are Fe-rich chlorite and close to the clinochlor field. Geochemical studies indicate that grades of Ag, As, Cu, Sb and Sr in the stratiform ore (bedded-banded and massive) of the third sub-horizon are much higher than the other sub-horizons, and are 41, 273, 1945, 390 and 1013 ppm, respectively. All geochemical studies show that metal zoning in this deposit is clear, this is characteristic of VMS deposits. Development of zone-refining and over refining processes caused leaching of Cu from the stringer zone and vent complex facies and its later precipitation in the bedded ore facies. Among across to different sub-horizons in the Varandan deposit, third sub-horizon is recognized as economic for Ag extraction .
