Document Type : Original Research Paper
Authors
Assistant Professor, Department of Geology, Faculty of Science, Urmia University, Urmia, Iran
Abstract
Issiso hot springs are located 70 km of North of Urmia, within the northernmost part of the Sanandaj–Sirjan zone. The basement of study area is comprised by precambrian metamorphic rocks that consist of gneiss, schist and amphibolite are overlain by younger sediments. The boron concentration in the study area thermal waters is up to 451 mg/l. The warm waters of the region belong to the type of Na-(SO4)-HCO3. The Na/Cl ratio is more than 1 and B/Cl ratio is 0.37. It reflects the impact of specific geological phenomena in formation of rocks. Up to now there is no any geological study of the origin boron in this area. The main aim of this study is to determine geological factor(s) creating this high concentration which caused many environmental problems in the region. In this study it is determined that penetration meteoric water, heated by the deep intrusive magmatic bodies and then rises up with magmatic waters. At high levels, these waters collect in reservoirs including metamorphic host rocks and caused leaching of boron bearing mineral phases. The boron bearing water reaches the surface through faults. Part of the contamination water appears in the form of hot springs and another part through the faults caused spread contamination around the areas. This study shows that high boron contents in the Issiso thermal waters can be attributed to: 1) unstable boron bearing mineral phases same of muscovite, tourmaline, biotite and hornblende in the metamorphic rocks such as gneiss and mica schist, and 2) input of boron-bearing magmatic fluids, related to young volcanic activities. Due to the high temperature play a large role in leaching the boron from the path rocks, it is estimated that high content of boron in Issiso springs may indicate the presence high potential of reservoirs of hot water in depths of earth and also the presence of rocks with high boron content in the path of rising waters.
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