Magnetite geochemistry an approach to determining the physicochemical conditions of Alam- Kandy iron skarn formation, West Mahneshan, Zanjan province

Alam-Kandy iron skarn lies at the contact margin of a granodiorite stock with limestone and dolomites of Soltanieh Formation. Anhydrous prograde calc-silicate assemblages (garnet, diopside, wollastonite) were replaced by a series of hydrous calc-silicates (serpentine, epidote, tremolite-actinolite) and/or quartz, calcite, magnetite, hematite, and pyrite. During this event, magnetite lenses (±hematite and pyrite) are formed with various textures such as massive, banded, scattered grains and veins at the vicinity of the intrusion body and the contact zones. According to this study, The geochemistry of trace elements of magnetite is variable under the influence of progressive and regressive stages of skarn formation and wall rock composition, and consistant with the indicators of magnetite formation in the (magnesium) skarn environment. These include factors such as: 1) high concentration of Mg (1 to 1.5 %), low values of Cr (<10 ppm), Ti (<0.01%) and insignificant incompatible elements such as Ag (0.5 ppm) 1 <), Rb (ppm 1 <), Sb (ppm 1 <) and Na (less than 0.1%) in magnetite; 2) significant positive correlation between Ti and V and the position of the samples in the Ti+V versus Ca+Al+Mn and Ni/(Cr + Mn) diagrams. High temperature vein-veinlet magnetites have more cobalt content than the replacement magnetites syn-deposited by sulfide minerals (retrograde stage), indicating that in the Alam Kennedy skarn system, the concentration of cobalt in the magnetite is controlled by the abundance of sulfide mineral deposits.