Study of the environment and how to form The Zavarian gold occurrence, southwest of Salafchegan
Executor of project: Dr. Seyed Mehran Heidari
Project Associates: Eng. Elnaz Zahmatkesh
2019
The Zavrian gold ocurence located in 60 kilometers southwest of Qom and some 5 kilometers of Salafchegan, northwest-west of Urumieh-Dokhtar magmatic belt. Geodynamic setting of the region is an active continental margin which consist of Zagros orogenic belt. Mostly of litology unit outcrops in this area related to a sequence of sedimentary units to the Oligo-miocene age, which are cut by volcanic complexes. Tectono-magmatic phases in the region are including of the continuous spectrum of subduction to post collision magmatic activities. Between the broad spectrums of magmatic phases, mainly of gold deposits are related to the lower Miocene (Touzlar, Zavarian, Dalli) and Middle-late Miocene (Sari Gunay, Chah Zard, Bazman).
The Lower Miocene magmatic in the Salafchegan area, developed with extrusive volcano-subvolcano complexes such as strtovolcane and has created conditions for forming magmatic-hydrothermal potential in this area (such as Zavarian and Dalli). Between them, the Au-Cu mineralization formed due the hydrothermal activity that occurred concomitantly with the lower Miocene at 21 Ma. The mineralization is located within calc-alkaline volcanic complex (stratovolcano) and occurs in relation with fractures and faults resulting from Oligo-Miocene. Although mostly of fractures and faults trend in this area are NW-SE, but the mineralization trend is related to subvolcanic intrusives and NE-SW tend. The hydrothermal alteration, propylitic, argillic and phyllic alteration, silicification associated with hydrothermal brecciation and precipitation of sulfides, is similar to the high sulfidation deposits in volcanic settings. The mineralization took place under relatively high temperatures at around 220-350°C from intermediate saline fluids (10-15 equiv % NaCl) which expresses the high temperature of the formation of mineralization in this event, as well as its relationship with subvolcanic intrusive. Low and falling pressures throughout the hydrothermal history suggested deposition of gold and rapid reduction of temperature and phases separation. Low pressures of formation are in agreement with the geological environment of the ore formation within a volcanic to subvolcanic complex at shallow depths. Gold in this mineralization occurs as solid solution in pyrite grains and other sulfide ores.
Although the mineral specification, fluids, all suggest the similarity of this ore with high sulfidation deposits, but considering that hydrothermal deposits are integral range of porphyry to epithelium and even geothermal deposits. According and considering the formation environment of this ore formation, which is a shallow intermediate extentional environment, the choice of the word intrusion related epithermal deposit, is more suitable for Zavarian deposit.