Mineralogy and geochemistry of Nodoushan Zn-Pb deposit: A transitional deposit in UDMA, Central Iran

Abstract

Eocene magmatism with intermediate-acid tuffs and volcanic rocks, the host to the Nodoushan deposit in Yazd province, intruded by Oligocene early diorite and later granite plutonic rocks. The former involved in iron skarn (containing epidote and euhedral grossularite) to the north and northern part of the deposit, the latter contributed to fault-controlled Zn-Pb deposit. The structural features controlled both the mineralization and consequent alterations which ranged from silicification (central) to argillic (northern). Propylitic alteration and dolomitization considered the minor ones, the iron contamination of which could be provided by earlier iron mineralization. Sulfide minerals dominantly pyrite, sphalerite and galena followed by chalcopyrite and late stage copper minerals such as covellite, digenite, bornite, chalcocite. Oxide minerals developed to the depth of 40m as a result of faults. Sphalerite which is of high-Fe type was characterized by extensive chalcopyrite disease, the iron content of which provided by earlier iron concentration. The concentration of chalcopyrite exsolution along sphalerite margins as well as galena veinlets is due to the thermal shock of later stage hydrothermal fluids that deposited galena and chalcopyrite. Negligible fossil replacements indicate both mineralization and alteration. It was concluded that the Zn-dominant mineralization was deposited under the structural controlling faults which reflects part of its earlier iron mineralization.