MSc lecture by Gaetan Sakindi

Gaetan Sakindi, M.Sc. Fellow in geophysics at the University of Iceland will give a lecture on his MSc project on Monday 18 May, 2015 at 14:00 at University of Iceland, Askja building, room 130.

The title of the project is:

Three-Dimensional Inversion of Magnetotelluric Data: Geological/Geothermal Interpretation of Asal Geothermal Field, Djibouti

Gaetan's supervisors are: 

Gylfi Páll Hersir and Knútur Árnason at ISOR. 
The external examiner will be Leó Kristjánsson, geophysicist at UI. 

Everyone's welcome to attend.

Abstract

In the thesis different ways of performing interpretation of MT data are discussed. Three dimensional inversion was carried out of a data set consisting of 105 MT soundings collected in the Asal geothermal area in Djibouti. The result was compared with previous results of one dimensional inversion. The same number of TEM soundings collected at nearby sites were used to allow the correction of static shift of the MT data.

The results of the interpretation shows four main resistivity structures below the geothermal area: A shallow laying thin high resistivity layer followed by low resistivity (conductive cap). Below there is a high resistivity layer (resistive core) underlain by a deep laying conductor. Lithology based on well data shows that the shallow thin high resistivity layer corresponds to dry basaltic rocks covering the surface, the conductive layer reflects saline fluids but correlates also with low temperature alteration (smectite and zeolites), the deep resistive core correlates with the high temperature alteration minerals (chlorite and epidote) whereas the deep seated conductive body is most likely connected to the heat source of the Asal geothermal system. At sea level the conductive cap covers the central part of the Asal rift including and Fiale explosion crater (Lava Lake). This is the same area where the fumaroles and hot springs in Asal rift are located. The NE part of the Asal rift is dominated by shallow high resistivity. Towards Lake Asal in the vicinity of Ardoukoba volcano and in the SE part of Asal rift around Baddikoma region, high resistivity is seen. An updoming conductive cap intersects the high resistivity, running NE-SW and reflects presumably alteration within the geothermal system.