Structural Modelling of Mouil Graben, Sabalan Geothermal Field, NW Iran
Mahnaz REZAEIAN, Mohsen ELYASI, Mohammad FARIDI, Isa KARAMI, Hasan MOGHIMI
[Institute for Advanced Studies in Basic Sciences, Iran]
The Plio-Quaternary strata-volcano of Sabalan in Arabian-Eurasian collision zone, shows a meaningful structural control on the configuration of the geothermal field in the area. In NW of the volcanic cone, the location of highly potential geothermal field in Mouil graben is bounded by first order longitudinal Mouil and Dizu oblique normal faults. The area has been investigated structurally through a detail field observation in order to extract the maximum horizontal stress orientation and corresponding volcanic structure. Temporal pattern of maximum horizontal stress orientation in the time of eruption and after that correlate with structural evolution of the volcanic cone. By applying multi-inversion method, we show that magma ascending induced a major radial pressure distributed around the injection axis and caused formation of syn-eruption structures. The trace of radial pressure has been tracked in Sabalan by the inversion analysis of faults geometry data in those reverse faults are the most important product of this phenomena. The analyses correspond to an estimated stress ratio of n =0.9 where sigma3 stress axis is vertical. The normal faults those formed in the same stress field have caused subsidence in the caldera area. Radial extension with estimated stress ratio of n =0.1 where sigma1 stress axis is vertical. Post-eruption stress regime, in last 149 ka, has been identified in kinematic analysis of the structural data. There is a good correlation between the current stress regime in NW Iran and the results in which dominant stress regime is strike slip with stress ratio of n=0.5 where sigma2 stress axis is vertical. An anticlockwise rotation is tentatively implied from syn- to post-eruption maximum horizontal stress orientation in last 4.5 MY.
|        Topic: Geology||Paper Number: 12158|