| Title | Characteristics of fluid inclusions in Menengai geothermal field, Kenya from wells MW-35, MW-28A & MW-10B. |
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| Authors | Marietta Mutonga, Thomas Tindell, Kotara Yonezu, Yasuhiro Fujimitsu |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | Fluid inclusions, Geothermal, Fluids, Menengai |
| Abstract | Menengai caldera located within the axis of the central segment in the Kenyan Rift is a major Quaternary central volcano. It hosts one of the high temperature geothermal fields located in the central Kenyan rift valley. Local temperature information can be obtained from fluid inclusions trapped in minerals if they contain hydrothermal fluids representative of the recent thermal conditions. Fluid inclusion studies have been carried out with a view to evaluate the evolution of thermal fluids in the Menengai geothermal field using fluid inclusions observed in quartz and calcite hydrothermal minerals. Inclusions were analyzed at varying depths between 1000-2000m in MW-20, MW-28A and MW-10B by micro-thermometry. Fluid inclusions in calcite occur in platy calcite crystals and the quartz crystals are mainly found in vesicles in some instances as prismatic euhedral crystals. The results indicate that we have two types of inclusions Type 1 fluid inclusions two-phase are (Liquid+ vapor) aqueous inclusions. Type 2 inclusions are monophase fluid inclusions (liquid or vapor). Type 1 are common in all samples and are forms either as primary isolated, clusters or randomly distributed inclusions or as secondary inclusions or as trails along annealed fractures in the grain. Type 2 are rare and are observed as isolated inclusions or in a cluster with other types (i.e., Type 1 and 2). The most predominant population throughout the different samples is two phase (Liquid + vapor) aqueous fluid inclusions (i.e., Type 1). Fluid inclusions vary in size from 0.5-5 µm, with inclusions that have less than 40% vapor volume homogenizing faster. The homogenization temperatures and salinities vary from 200-349oC and 0.27- 6.16 eq. wt % NaCl. |