Geochemistry and Alteration Mineralogy of Well NWS-10, Mt. Sabalan Geothermal Field, NW-Iran

摘要

The town of Meshkin Shahr is located in N W-Iran and has a population of 164,000. Mount Sabalan is stratovolcano, located southeast of Meshkin Shahr. The Sabalan geothermal prospect lies in the Moeil valley on the western slopes of Mt. Sabalan, approximately 16 km southeast of Meshkin Shahr, well NWS10D is the 10th geothermal well drilled at the Northwest Sabalan Geothermal Project. It is collared at Pad D and deviated towards the eastern quadrant to a target azimuth of 94°. This study considers geothermal conceptual modeling as an important tool in exploration and exploitation of geothermal resources. The main objective is to use thermal fluids and hydrothermal alteration mineral geothermometry to develop a conceptual model of the Sabalan Geothermal Field. Hydrothermal alteration mineralogy and thermal fluid chemistry are important sources of useful information in geothermal conceptual modeling. Alteration minerals can be used to infer subsurface formation temperatures and also reconstruct the thermal history of a geothermal field. Chemical and solute geothermometers from thermal fluid analysis on the other hand help in the calculation of subsurface temperatures. The approach pursued in the study included; (1) The chemical analysis of major elements in the thermal fluids from geothermal field, in order to calculate subsurface temperatures using geothermometric equations by Foumier (1979), Arnosson et al. (1983) and Giggenbach (1988). (2) The use of lithological log from well NWS 10D drilled in the afore mentioned subfields to reconstruct lithostratigraphy and hydrothermal alteration zona-tion. Results from calculated temperature on fluid chemistry and inferred temperatures from alteration minerals, indicate an high subsurface temperature in Sabalan Geothermal Field.