| Title | Updating of the Descrptive Conceptual Model of Paipa Geothermal System, Colombia |
|---|---|
| Authors | Claudia ALFARO, Jesús RUEDA, Camilo MATIZ, Gilbert RODRÃGUEZ, Carlos GONZÃLEZ, Miguel BELTRÃN, Gina RODRÃGUEZ and Jaison MALO |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Colombia, Paipa geothermal system, Paipa conceptual model |
| Abstract | Based on the integration of a 3D geological model constrained by potential fields geophysics, a magneotelluric 3D inverse model and, updated geological and geochemical information, a new descrptive geothermal model is proposed for Paipa geothermal system. The system is hosted in a sedimentary environment, where it coexists with a sodium sulfate saline water circulation circuit and with rocks enriched in radioactive elements. The sedimentary sequence is intruded by two dome complexes (Alto Los Volcanes and Alto Los Godos) and hypabyssal rocks and is partially covered by pyroclastics deposits from the volcanic activity. Sodium sulfate saline hot springs, with temperature up to 76°C, with abundant gas discharges are concentrated in two zones structurally controlled. The proposed conceptual model describes a main magmatic heat source and the possible radiogenic heat contribution from igneous rocks enriched in 238U, 232Th and 40K. The main recharge zone come from the outcrops of sandstones from a Cretaceous sedimentary formation (Une) from the east and southeast in the Tibabosa-Toledo Anticline. A deep recharge (to the basement) would occur towards the north from the circulating water through the Une formation, which in the valley where the system occurs underlies the younger sedimentary sequence, by following extensive structures as faults, crosses between faults and the contact planes of igneous intrusions with rocks from the basement and the sedimentary cover. A sedimentary reservoir is located in the Une formation from the geothermal fluid upflow, between the dome complexes. The proposed cap rocks consists of clayish levels from the sedimentary sequence. The discharges zones are known as La Playa and ITP-Lanceros sector. La Playa sector, consists of few low flowrate hot springs (~0.2 l/s), one of which has the highest temperature in the system, and one low pressure and low temperature (70°C) steam vent. The ITP-Lanceros is shaped by several springs of higher flowrate (up to 6 l/s) and temperature up to 72°C. Two sodium sulfate low temperature springs with the highest total dissolved solids concentration in the area represent the endmember of a the mixing process experienced by the hot water along its path to the surface. The mixing process causes a chemical and isotopic masking of the geothermal water composition. The alkaline geothermometers are not reliable. A simple enthalpy-silica model suggests a maximum temperature around 230°C. The hydrothermal alteration in xenolites points out temperatures up to 320°C. The high 3He/4He ratios suggest a high temperature reservoir. |