2:30 PM - 2:45 PM
[HRE11-03] Application of thermoluminescence of calcite and feldspars for geothermal exploration. Case study: Santa Rosa de Lima, El Salvador.
Keywords:Geothermal exploration, Calcite, Feldspars, Thermoluminescence, El Salvador
Thermoluminescence (TL) is a thermally stimulated emission of light exhibited by crystals, such as quartz, feldspars, and calcite, when energy from radiation is absorbed in crystalline lattice imperfections and re-emitted by heating; TL measurements are made by use of a stationary equipment composed by a heater enclosed in dark room, photomultiplier tube (Hamamatsu Photonics R374), heater control and luminous intensity data logging system. Sample is heated from room temperature to 400°C at 0.5 °C/sec for TL measurement. Thermoluminescence of quartz has been previously applied for geothermal exploration successfully; in this study, the use of calcite and feldspars TL for geothermal exploration is proposed. El Salvador is located in Central America along the Middle American Trench (Fig. 1a), volcanic rocks contain mainly feldspars; however, calcite and low amount of quartz is also found in the northern part of the country. Rock samples from Santa Rosa de Lima at NE of El Salvador, mainly ignimbrites, tuff, lavas, and veins, were analyzed; minerals from rocks were collected by hand pick up and characterized using X-ray diffraction (XRD). A direct relation between the TL intensity of these minerals and the hot up flow location of geothermal fluids is expected.
TL measurements results showed a glow-curve with two peaks of high TL intensity around 260°C and 340°C corresponding to calcite and a single peak of low intensity around 270℃ corresponding to albite (Fig. 1b); deconvolution of calcite glow-curve was performed, and results will be shown in this study. Spatial distribution of TL intensity of feldspar and calcite from rocks and veins suggests the most probable hotter zone of geothermal reservoir is located at the NW area of Santa Rosa de Lima (Fig. 1a), associated with lower values of TL intensity, and correlated with hot springs location and fault system preferential pattern. From these results, calcite and feldspars TL could be applied for geothermal exploration to improve the knowledge of geothermal activities.
TL measurements results showed a glow-curve with two peaks of high TL intensity around 260°C and 340°C corresponding to calcite and a single peak of low intensity around 270℃ corresponding to albite (Fig. 1b); deconvolution of calcite glow-curve was performed, and results will be shown in this study. Spatial distribution of TL intensity of feldspar and calcite from rocks and veins suggests the most probable hotter zone of geothermal reservoir is located at the NW area of Santa Rosa de Lima (Fig. 1a), associated with lower values of TL intensity, and correlated with hot springs location and fault system preferential pattern. From these results, calcite and feldspars TL could be applied for geothermal exploration to improve the knowledge of geothermal activities.