Mineralogy, geochemistry and conditions of formation of The Abri and Rahbari Copper deposit, N-W of Daroneh

The sulphide deposits of stratabound and stratiform are one of the largest sulphide deposits for copper mineralization. by examining and comparing the deposits and mineral signment discovered in the Eocene volcanics with Mantle type deposits in Chile, they concluded that the Manto deposits were formed in the uppermost porphyry andesitic lavas of Eocene Iran and can be considered as a metallogenic unit to explore this type of mineralization. In Iran, Manto type deposits have been reported just in Urumieh -Dokhtar zone, Sanandaj-Sirjan zone and Sabzevar sub-zone. Abari and Rahbari deposits are among the Manto type deposits in the volcanic-intrusive belt, Khaf- Darooneh and the southern part Sabzevar sub-zone. In this research, mineralogy, geochemistry and formation pattern of Abari and Rahbari copper deposit were discussed and investigated.

In this research, 100 thin and polished sections were prepared and studied, and the studies of fluids inclusion were done by preparing and studying 3 double-polished sections from surface samples. In order to identify minerals and complete alteration studies, 6 samples were analyzed by XRD method and for geochemical studies, 22 samples of ore and volcanic-sedimentary rocks were analyzed by XRF and ICP-MS methods in Binalud deposits Laboratory and Iran mineral processing Research Center.

According to the diagenetic-epigenetic model, the stages of mineralization and formation processes can be described in three stages: the first stage: initial diagenesis, the second stage: the burial diagenesis stage, and the third stage: the uplift stage (hydrothermal activities). Initial diagenesis stage: after extensive volcanic activities, during the diagenesis stage, in this stage, seawater sulfate regenerating bacteria were present in the environment, and their activity has caused regeneration conditions in the basin. As a result, the resulting sulfur with the available iron causes the deposition of pyrite in the form of scattered grains and fills the empty spaces in the rock background. Secondary diagenesis stage: from the stage of diagenesis onwards, burial occurs as a result of the deposition of newer sediments on them. the hydrothermal fluid carries the copper released from the conversion of iron hydroxide minerals into iron oxides, as well as the copper released in the network of feldspar minerals in the transformed volcanic units due to the high environment temperature and circulation in the volcanic and pyroclastic units and then turning up in the rock units, it reached the pyroclastic unit with high porosity and permeability, and chalcocite and chalcopyrite minerals were formed in the burial diagenesis stage. upwelling Stage (hydrothermal activities): at the end of the burial process and with the beginning of the uplift of the area and faulting, the open spaces increase by Darooneh and Binalood faults, which ultimately causes the activity and concentration of sulfide and copper oxide mineralization will start again along the faults, cracks, and even the empty spaces of the pyroclastic units.

The Eocene volcanic rocks of the magmatic belt in the north of the structural zone of central Iran are the host of Abari and Rahbari copper deposits with the dominant composition of andesite and basaltic andesite. The effective factors copper mineralization in the study areas including: 1) The lithology of host rocks, 2) structural controls, 3) hydrothermal fluids and 4) The presence of intrusive rocks at depth and basaltic dykes. The controllers play a significant role in the transfer of hydrothermal fluids and their accumulation and deposition. Mineralization is formed in three stages: initial diagenesis, burial diagenesis and uplift stage (hydrothermal activities). The dispersed pyrites is source of sulfur in reducing conditions (resulting from the activity of seawater sulfate reducing bacteria). Based on the studies of intermediate fluid loads, the processes of dilution with surface fluids, mixing with isothermal fluid, cooling and pressure reduction can be considered responsible for the changes created in the fluid. So that mineralization in the Abri and Rahbari area is epigenetic, strata bound that is similar to the manto type copper deposits.