A study and review on the hydrothermal and geochemical alteration patterns of copper porphyry area of Abrisham Rood

The geochemical alteration index plays a vital role in recognizing, classifying, and quantifying alterations. It is an essential exploration guide for hydrothermal mineral deposits. Qualitative and quantitative studies help to classify alteration mineral assemblages based on field and petrographic observations. Spectroscopy, X-ray diffraction, and scanning electron microscope (SEM) are non-invasive advanced techniques for the same. Since alteration processes cause enrichment of certain elements over others, it provides clues for alterations' degree and type. Geochemical alteration indexes, norms, and mass balance calculations are examples of quantitative alteration studies. Among them, the geochemical alteration index is commonly practised for rapid evaluations, compared to other petrographic observations. It provides various alteration trends and relationship between mineralogy, litho-geochemistry, and alteration intensity in zoned alteration systems (VHMS deposits) and other hydrothermal deposits. In this study, the zonality method has been used to separate geochemical anomalies and to calculate erosional levels in the regional scale for porphyry-Cu deposit, Abrisham-Rud (Semnan province, East of Iran). In geochemical maps of multiplicative haloes, the co-existence of both the supra-ore elements and sub-ore elements local maxima implied blind mineralization in the northwest of the study area. Moreover, considering the calculated zonality indices and two previously presented geochemical models, E and NW of the study have been introduced as ZDM and BM, respectively. For comparison, the geological layer has been created by combining rock units, faults, and alterations utilizing the K-nearest neighbor (KNN) algorithm. The rock units and faults have been identified from the geological map; moreover, alterations have been detected by using remote sensing and ASTER images

کلیدواژه ها:

porphyry-Cu deposit ، vertical zonality index ، geological layer ، alteration ، K-nearest neighbor.