World Geothermal Congress 2020+1
March - October, 2021

Geochemistry of Hydrothermal Alteration Zone, Sabalan, Iran


[University of Tehran, Iran]

Sabalan geothermal prospect situated in the Azerbaijan Plateau, part of Alpine- Hymalayan orogenic belt. MT survey established the existence of a significant zone of associated low resistivity at depth. Exposed at the surface in the Moiel valley are altered Pleistocene volcanics The wells has altered Peliocene to Pleistocene volcanics, terrace deposits and a Pleistocene trackydacite dome. Sabalan geothermal system has been cooling since the alteration mineral formed. Comparision of formation and alteration temperatures of the wells was done by plotting the downhole temperature logs and the inferred alteration temperatures of different mineral encountered in the wells. There are complex alteration patterns produced by hydrothermal events associated with the monzonite and the two phase of dyke intrusion. The main emphasis of this paper is to elucidate the nature of chemical transport in hydrothermal alteration by correlating the bulk composition of rock samples with their petrographical characteristics and results of ICP-MS analysis. We will show that it possible to assess the amount of chemical dilution that has taken place. This allows the deduction of the primary concentration of the immobile elements in the altered rocks, and by correlating these with the relatively fresh volcanic, also using the isocon method for determining mass transport. Four alteration zones including phyllic, argilic, propillitic and calcitic identified. The results demonstrate notable differences in the REE behavior in the different alteration zones, Accordingly, comparision with the fresh rocks, in the phyllic alteration, LREEs are enriched, but HREE expect Yb which enriched, unchanged. In the argilic and propylitic alteration zones, all REEs are depleted. The main objective of this study of wells is gain Subsurface geoscientific information on geology and geochemistry, behaviour of Rare Earth Elements (REEs) in hydrothermal alteration zones. In this field maximum temperature is 240°C at 3197m in 7 well . The distribution and abundance of the hydrothermal minerals were obtained from petrographic and XRD analysis of the drill cutting samples taken after every 2m.

        Topic: Geochemistry Paper Number: 14001

         Session 8P: Poster 2 [Tuesday 11th May 2021, 11:00 pm] (UTC-8)
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