Mineralogical and Chemical Mass Changes in Granitoids, Monzonite and Dioritic Rocks from the Pasa Kuh Ore Deposit

Mineralogical, petrological and geochemical investigations of rock samples from the Pasa Kuh ore deposits reveal a large variety of mineralization styles. The deposit is characterized by magnetite and hematite concentrations with distinctly low titanium contents (<2% TiO,) and contain copper sulfide minerals (e.g. pyrite and chalcopyrite). The mineralization at Pasa Kuh field is a combination of melt/rock interactions, intermediate intrusions plus interaction of hot hydrothermal fluids. These processes lead to significant gains and losses of major and trace elements. Due to the formation of clinopyroxene, dioritic intrusions act as a sink for MgO during alteration. Interaction between diorites and hydrothermal fluids leads to significant redistribution of SiO2, TiO2, CaO, and Na2O as well as numerous trace and rare elements. The different kinds of alteration and their associated element changes reveal that samples from the Pasa Kuh field have been influenced by some hydrothermal fluids. Therefore, the hydrothermal fluid-dominated alteration of the intermediate rocks is a sink for many trace and rare elements which were provided by intermediate intrusions and mobilized by hydrothermal fluids and melt-rock interaction. The mineralogical and petrological studies have revealed four major factors which appear to control the polymetallic mineralization in the Pasa Kuh ore deposits: I) magmatic emplacement involving immiscible iron-rich melts, II) syngenetic exhalations, III) hydrothermal activities and IV) faulting. Hydrothermal circulation has taken place throughout faults and joints, altered the rocks and formed some hydrothermal deposits.

Keywords:

Pasa Kuh ore deposits , polymetallic mineralization , immiscible iron-rich melts , hydrothermal activities