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Paper Information

Journal:   AMIRKABIR   Summer 2003 , Volume 14 , Number 55-C; Page(s) 865 To 877.
 
Paper: 

INTRODUCING THE SPECIFIC PHYSICO-CHEMICAL CONDITIONS IN "450 C", AS PREVENTORS TO CHALCOPYRITE DEPOSITION IN THE SUNGUN PORPHYRY COPPER DEPOSIT, IRAN

 
 
Author(s):  HEZARKHANI A.*
 
* Department of Mining, Metallurgy and Petroleum Engineerin Amirkabir Universi
 
Abstract: 

Copper mineralization at Sungun porphyry copper deposit is essentialy associated with potassic and less sericitic alteration. Fluid inclusion and isotopic data from oxygen and sulfer, show that main copper mineralization at Sungun occurred in the temperature range of 300-400 °C (with the mode of 360 °C). These data also indicate that the hydrothermal system involved both magmatic and meteoric waters, and boiled extensively. In this research, thermodynamic data are used to delineate the stability fields of alteration and ore assemblages as a function of fs2, fO2, aCl and pH (in the fixed temperature of 450 °c and the pressure of 500 bars) for the chalcopyrite dissolution and deposition.
During critical fluid conditions in higher the temperature (>450 °C), copper solubility is Calculated to have been >100,000 ppm, whereas the copper content of the initial fluid responsible for ore deposition is estimated from fluid inclusion data to have been maximum 3800 ppm. This indicates that the fluid was initially undersaturated with respect to chalcopyrite, which agrees with the observation that veins formed at T>400 °c and contain rare chalcopyrite. Copper solubility drops rapidly with decreasing temperature, and at 400 °c is approximately 1000 ppm, within the range estimated from fluid inclusion data. At temperatures less than 350 or 360 °C, the solubility drops to<25 ppm. These calculations are consistent with observations that the bulk of the chalcopyrite deposited at Sungun is hosted by veins formed at approximate temperatures of 360
± 60 °C. Other factors that may reduce chalcopyrite solubility are increases in pH, and decreases in F02 and aCl. Based on the calculations done in this paper, it is proposed that the Sungun deposit formed partly in response to the sharp temperature decrease and pH increase. In high temperatures (450 °C) chalcopyrite dissolved rapidly and as it is shown later on, the high temperature could be a very important factor to prevent copper depositition in an economic level within the Sungun system

 
Keyword(s): SUNGUN THERMODYNAMIC, CHALCOPYRITE, DISSOLUTION, DEPOSITION, PORPHYRY
 
References: 
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