اندازه گيري مغناطيس سنجي زميني براي اكتشاف طلا در منطقه اكتشافي هيرد، خراسان جنوبي

Ground Magnetic Survey for Gold Exploration at Hired rospect Area, South khorasan

Hired gold mineralization area is located at 160 Km to the south of Birjand(air distance) and 80 Km to the north of Nehbandan in south Khorasan province. Mineralization in the Hired prospecting area is observed in 4 targets named target 1 to 4. Intrusive rocks associated with mineralization are illmenite-type granite, granodiorite and monzonite with low magnetic susceptibility and are post Eocene. Mineralization type at Hired is reduced intrusion-related gold system because of reduced source rocks and mineral assemblages such as pyrrhotite & arsenopyrite. Detailed mineralogical studies indicate that sulfide mineralization along with gold have pyrrhotite only in the eastern part of target 1. Mineralogical studies, magnetic susceptibility measurements on drilled cores and ground magnetic data confirm the presence of pyrrhotite on the eastern part of target 1. Based on detailed drilled core studies, there is relatively good correlation between the increase of pyrrhotite(to 6 %) and the amount of gold(to 5 ppm) in the eastern part of target 1. Total Magnetic Intensity(TMI) of the surveyed profiles and contour map from this part of the mineralization reveal obvious anomalies in the eastern part of target 1 that the causative sources of them are pyrrhotite along with mineralization. Mineralogical studies, magnetic susceptibility measurements from bore holes and ground magnetic survey on the western part of target 1 and target 3 indicate no pyrrhotite along with mineralization. The amount of gold on these areas is much less than the eastern part of target 1. Based on the presence of pyrrhotite along with gold mineralization on the eastern part of target 1, magnetic method is used as a useful geophysical method for the determination of drilling location and consequently access to gold mineralization in the eastern part of target 1.