1D inversion of magnetotelluric data from Mainit geothermal area, Phlippines

Abstract

Mainit geothermal project is one of the geothermal prospects located in Surigao del Norte, Philippines. Aside from hosting several warm springs, the province is also rich in minerals with abundant deposits of silver, copper, gold and nickel. Several studies have been conducted in the area to confirm the viability and feasibility of a geothermal system, the most recent one was undertaken in 2012 by Energy Development Corporation (EDC). Magnetotelluric (MT) survey was conducted in 2012 to determine the subsurface resistivity structure of the area. Based on the result of the 1D inversion, three significant findings were observed: 1) A shallow, high-resistivity layer of the PacoManiayao Volcanic Complex (PMVC) is associated with the Young Paco-Maniayao volcanics; 2) A low-resistivity layer outcropping in the west and northwest of the PMVC is generally characterized by Tugunan sedimentary formations; and 3) A high-resistivity layer at depth, northeast of the area is believed to be an intrusive body which could be a heat source which is also responsible for the mineralization processes as manifested by mineral deposits. However, since the MT data were obtained close to the coast, the surrounding conductive sea makes interpretation difficult, especially the deep part of the subsurface which might give a different response in the inversion due to the effect of the sea.