Pyrite Formation in Amir-kalaye marsh in the north of Iran

H. Torabi-Golsefidi

hossien_t@yahoo.com

Faculty of Agriculture, Department of Soil Science, Shahed University, Tehran, Iran.

Abstract

The majority of wetlands in Iran are inland. Several types of wetlands have been described in the north of Iran located in the West part of Southern Caspian Sea. There are two important marshes (Anzali and Amir-kalayeh) in Guilan Province in the north of Iran. The objective of this study was to determine the Eh value in Amir-kalayeh marsh by permanent installation an platinum electrode in 2003. Mineralogy and micro-morphological studies were determined by x-ray diffraction and preparation of thin section respectively. The maesuring of the redox parameter (pe + pH) in subsurface horizon showed that pyrite (α-FeS₂) was formed. Redox parameter in this soil was 3.2 in some times of year. Results showed that in Amir-kalaye submerged soils sulphate (SO₄^2-) concentration and CO₂ (g) pressure were 10^-2.54 M and less than 10^-3.5 atom respectively. Therefore, in this condition, pyrite can be formed thermodynamically. Pyrite was observed in micro-morphological study and incident light. The pyrite was observed in x-ray diffractometer study. Results showed the soil of Amir-kalaye marsh would be considered as a potential acid sulfate soil.

Keywords: Wetland, Pyrite formation, Guilan, Iran.