Mineral chemistry and Chlorite thermometry of late dykes in Sungun Cu-Mo deposit, North West of Iran

Chlorite group minerals have a wide range of chemical composition that reflect their physical and chemical conditions of crystallization. In this research, the chlorite mineral geothermometry method has been used to determine the alteration temperature of delay dykes in Sungun copper-molybdenum porphyritic deposit, located in the northwest Iran. Based on the microprobe data, the compositional changes of chlorite reflect a large differences in the content of silicon, aluminum, iron and magnesium elements in these dykes. The chemical composition of the chlorites in quartz diorite porphyry (DK1a, DK1b), diorite porphyry (DK3) and microdioritic (MDI) dykes placed in picnochlorite range of type clinochlor and quartz- dioritic dykes (DK1c) are in the penin range type of chamosite. Chlorite in quartz diorite porphyry (DK1a, DK1b, and DK1c) and diorite porphyry (DK3) dykes enrichment in the Mg-chlorite and microdioritic (MDI) dykes enrichment in the Fe-chlorite and are classified as trioctahedral chlorites. According to different geothermometric methods, chlorite minerals in quartz diorite porphyry (DK1a, DK1b, and DK1c), diorite porphyry (DK3) and microdioritic (MDI) dykes, have formed at temperatures of 237°C, 217°C, 115°C, 276°C and 247 °C respectively. These temperatures show the effect of hydrothermal fluids in the formation of chlorite and show that the chlorites of the studied area can be related to the effect of hot fluids originating from magma. The relationships between the SiO2 content and the crystallization temperature in Sungun late dykes show an inverse and strong correlation; so that high temperature chlorites in these dykes have lower Si content than chlorites crystallized at low temperatures. Therefore, the silica chlorite content of these dykes can be an indicator of their crystallization temperature. Chlorites have specific compositional changes and atomic substitutions that reflect their crystallization temperature.