Mineralization of gold, copper and associated metals in the northern Hired area, South Khorasan, East Iran

Introduction
Northern Hired mining area with an area of about 25 square kilometers is located in South Khorasan province and 140 kilometers south of Birjand city. In this area, intermediate to acidic intrusive masses with the composition of granodiorite to granite have infiltrated and affected the Tertiary volcanic-sedimentary sequence. In the studied area, mineralization is associated with siliceous, sericite, tourmaline, chlorite and carbonate alterations. The structure and texture of these deposits include planar veins and veins and rarely stockwork, scattered, sheared and massed.
 
Materials and Methods
The studied area is located in the southern part of South Khorasan province. This area is located 145 km south of Birjand city and north of Hired village. The way to access this mineral area is the paved road from Birjand to Khosf and then Hird or from Nehbandan to Hired. After reviewing the library studies, a field visit was made to the target area. According to the area, samples were taken from all existing lithological units, mineral mass and alteration around the mine. 57 samples were taken for ICP-MS and ICP-OES analysis. The characteristics of all collected samples and studied stations are carefully recorded. Then, the analysis results were analyzed in the relevant software.
 
Results and Discussion
In this range, intermediate to acidic intrusive masses with the composition of granodiorite to granite have infiltrated and affected the Tertiary volcanic-sedimentary sequence. According to the field observations, the most important changes that have been identified on the surface of the earth are: 1) quartz-tourmaline-sericite, 2) carbonate and 3) propylitic. In the samples, plagioclase crystals can be seen both in the background and as phenocrysts, which sometimes have zoning. A number of plagioclases have been dissolved and recrystallized. The mafic minerals in the rock are amphibole and pyroxene.
Amphiboles and plagioclase have generally changed to chlorite and sericite, which indicates the effect of atmospheric waters on the rocks of the region. Mineralization in the studied area can be seen in the form of veins with different thicknesses along fractures and fault zones, and most of the mineralization has occurred in the basalts and basaltic andesite of the area. Amphibole and plagioclase have generally changed to chlorite and sericite, which indicates the effect of atmospheric waters on the rocks of the region. Pyroxenes are also seen in the composition of the background. In the analyzed samples, 29 samples have values higher than one percent of copper, of which 18 samples have values higher than five percent of copper. The maximum amount of molybdenum in the obtained samples was equal to 1.1%. 30 samples have values higher than 0.12% of lead and 12 samples have values higher than 1% of lead and the maximum amount of lead measured in the samples of this area was higher than 3%. 28 samples have values higher than 0.2% of sulfur and 3 samples have values higher than 1% of sulfur and the maximum amount of sulfur measured in samples of this area was higher than 3%. By drawing correlation diagrams. Cu element also has a good correlation with Mo element. (Al, Ti, Cr, Ni) Al with Ti and Also, Cr has a strong correlation with Ni. The gold element is also strongly correlated with iron and arsenic.
Conclusion
Geochemical investigations of associated elements show that the source magma of the mineralization in the northern Hired area is the result of subduction and hence it is type I. These investigations show that the existing gold is placed within the pyrite structure and according to the paragenesis of copper and molybdenum and also the presence of copper in the form of chalcopyrite minerals, it can indicate that the mineralization of copper and molybdenum is near The thermal source is formed, while gold mineralization is of epithermal type. Based on the conducted studies and field observations, the North Hired gold-copper deposit is mainly in the form of veins, and due to the high anomaly of elements such as lead, zinc and molybdenum, the term multi-metallic can be used for the North Hired deposit. In this range, intermediate to acidic intrusive masses with the composition of granodiorite to granite have infiltrated and affected the Tertiary volcanic-sedimentary sequence. The outcrop of these intrusive masses can be seen in the south of the range. Generally, the host rock of the mineralization in the range is basic to moderate, but in some places rhyodacite outcrops have also been observed.