Magnetite Chemistry in the Porphyry Copper Systems of Kerman Cenozoic Magmatic Arc, Kerman, Iran

Abstract

The present work attempts to characterize magnetite chemistry in some collisional (Chahfiruzeh and Keder; Miocene) and pre-collisional (Reagan and Daralou; Eocene–Oligocene) porphyry copper systems hosted in the Kerman Cenozoic Magmatic Arc (KCMA). EPMA results for magnetite samples show collisional deposits have higher average contents of Fe and Ca compared to those of pre-collisional systems. Nevertheless, magnetite samples of pre-collisional porphyry Cu systems contain elevated Si values. Highlightly, the frequency of V and Ca in magnetite have a direct relation with mineralization potential of studied deposits decreasing from Chahfiruzeh to Keder, Daralou and Reagan. V/Cr and V/Al in the analyzed magnetite samples show that Reagan porphyry system is quite different than other studied deposits. Moreover, average concentrations of Mo and Cu reach the highest in collisional and pre-collisional deposits, respectively. According to Fe/(V + Ti) diagram, most of the studied magnetite samples have re-equilibrated magmatic nature. Al + Mn versus V + Ti and Ni (Cr + Mn) versus Ti + V diagrams also confirmed that all magnetite samples from collisional and pre-collisional deposits are analogous to those reported previously for porphyry Cu systems. Regarding the condition of oxygen fugacity, based on Ni versus V diagram, the Reagan deposit (pre-collisional) has the highest oxygen fugacity, while the Daralou deposit (pre-collisional) and collisional deposits (Chahfiruzeh and Keder) exhibit moderate to high fugacity. Ti + V versus Al + Mn show that selected deposits were approximately formed in the same temperature conditions.