University of Isfahan Journal of Stratigraphy and Sedimentology Researches 2008-7888 39 4 2023 12 22 Study of source geochemical effects on brine hydrogeochemical changes of the Bajestan Playa, northeast Iran Study of source geochemical effects on brine hydrogeochemical changes of the Bajestan Playa, northeast Iran 13 26 27833 10.22108/jssr.2023.137202.1257 FA Sedighe Haghighi Gorji Department of Geology, Mashhad Branch, Islamic Azad University, Mashhad, Iran Habib Alah Torshizian Associate Professor, Department of Geology, Mashhad Branch, Islamic Azad University, Mashhad, Iran Mohammad Javanbakht Associate Professor, Department of Geology, Mashhad Branch, Islamic Azad University, Mashhad, Iran Vahid Khdemi Ph.D. student in Tectonics, Department of Geology, Birjand University, Iran Journal Article 2023 03 28 This research aims to investigate the hydrogeochemical changes and brine evolution process in dry areas, using the Bajestan Playa as a case study. The Bajestan playa is one of the largest playas in the Middle East, located in northeastern Iran within the Central Iran Plate. The playa is surrounded by volcanoclastic rocks and has an arcuate shape with a gentle slope from the margins to the center. The climate of the region is arid and the area belongs to the “D” type in Geomorphological classification. We collected and analyzed 35 samples by the XRF method in September 1998. The results showed that group (1) potassium, calcium, sulfate and magnesium ions; Group (2) of chlorine and sodium ions and group (3) of carbonate and bicarbonate were formed. The spatial distribution of elements indicated that group (1) elements were more prevalent in the south and central parts of the area, group (2) elements were more abundant in the north and east parts, and group (3) elements were more dominant in the west part. The current facies of the playa brine is magnesium sulfate, and the possible evolution paths are I, II, IIIA, IIIB, IIIC. Therefore, we can expect sodium chloride facies for the playa brine in the future. We concluded that the origin and evolution of water resources were the main factors affecting the hydrogeochemical changes of the Bajestan Playa brine. This research aims to investigate the hydrogeochemical changes and brine evolution process in dry areas, using the Bajestan Playa as a case study. The Bajestan playa is one of the largest playas in the Middle East, located in northeastern Iran within the Central Iran Plate. The playa is surrounded by volcanoclastic rocks and has an arcuate shape with a gentle slope from the margins to the center. The climate of the region is arid and the area belongs to the “D” type in Geomorphological classification. We collected and analyzed 35 samples by the XRF method in September 1998. The results showed that group (1) potassium, calcium, sulfate and magnesium ions; Group (2) of chlorine and sodium ions and group (3) of carbonate and bicarbonate were formed. The spatial distribution of elements indicated that group (1) elements were more prevalent in the south and central parts of the area, group (2) elements were more abundant in the north and east parts, and group (3) elements were more dominant in the west part. The current facies of the playa brine is magnesium sulfate, and the possible evolution paths are I, II, IIIA, IIIB, IIIC. Therefore, we can expect sodium chloride facies for the playa brine in the future. We concluded that the origin and evolution of water resources were the main factors affecting the hydrogeochemical changes of the Bajestan Playa brine. https://jssr.ui.ac.ir/article_27833_f6fa184365fe8be9ad4ef82fd2d9a4e1.pdf