The Petite Anse-Diamant Geothermal System (Martinique Island, Lesser Antilles): Results of the 2012-2013 Exploration

A 2012-2013 additional and combined – geological, hydrogeological, geochemical, geophysical -surface exploration results in a new insight of the Martinique geothermal systems, including Petite Anse – Diamant area. The Petite Anse – Diamanthot spring is located at the foot of a small volcano -Morne Jacqueline – part of a NW-SE volcano-tectonic corridor. The Southern flank of this volcano collapsed leading to the outcrop: 1) A previous neutral, high temperature hydrothermal activity corresponding to a MT conductive layer interpreted as a clay cap of the present geothermal system. The bottom of the conductive layer displays also a doming shape, characterizing the top of geothermal system; 2) A dyke of diorite coinciding with the top of a huge MT resistive body, following the volcanic corridor, and interpreted as a magma intrusion; it generates several on and off-shore spots of magmatic degassing; this intrusive gas –rock may act as a heat source and interact with the geothermal fluid. The Petite Anse spring water is of Na-Cl type due to a seawater contribution. The associated geothermal reservoir temperature is estimated at 190-210°C. The recharge of the system is likely to be low, because of both a bad permeability resulting from the extensive acidic alteration related to previous fumarolic expression, and limited rainfalls. An exploration drilling area is proposed at the North of the Petite Anse village.