Geochemistry in the Development of Geothermal Resources

Dear Colleagues,

Geothermal energy usually refers to the heat stored beneath the Earth's surface, which can be harnessed for electricity generation or direct use in heating and cooling applications. The exploitation of such resources needs a deep understanding of the chemical characteristics of geothermal fluids (both waters and gases) and associated rocks that host the fluids’ circulation pathways.

In this view, geochemistry plays a crucial role in both the geothermal resource exploration and exploitation by providing valuable insights into the composition, and origin of fluids and rocks within the Earth's crust, and their variations following interaction processes.

This information helps in identifying potential geothermal reservoirs even when no obvious manifestations occur at the surface (i.e., hidden or blind systems), evaluating their productivity, and assessing the long-term sustainability of geothermal systems.

Geothermal fluids usually carry dissolved elements and gases derived from the surrounding rocks with which they interact. By analyzing the concentration and isotopic composition of these elements, geoscientists can determine the source of the fluid, its temperature at depth, and the mineral reactions it has undergone which are crucial parameters for estimating the exploitability and sustainability of a geothermal resource.

Geochemical techniques such as water sampling, chemical analysis, and stable isotope analysis are used to characterize the composition of such geothermal fluids. The presence of certain elements and isotopes, such as silica, sodium, potassium, and helium, can provide valuable clues about the geothermal system's maturity, heat source, and fluid-rock interactions.

Another important aspect of geochemistry in geothermal exploration is the study of rock geochemistry. Rocks associated with geothermal systems often undergo alteration due to the circulation of hot fluids. Geochemical analysis of altered rocks helps identify mineralogical changes, such as the formation of clay minerals and zeolites, which can indicate the presence of a geothermal reservoir. Understanding the extent and nature of rock alteration is crucial for predicting the permeability and fluid flow pathways within a geothermal system.

Furthermore, geochemical studies also aid in monitoring the environmental impact of geothermal operations. By analyzing the composition of geothermal fluids before and after energy extraction, potential contamination risks can be assessed, and appropriate mitigation measures can be implemented to minimize any adverse effects on water quality or ecosystems.

This special issue aims at collecting scientific contributions relating to the application of geochemical studies to geothermal systems. The papers can be related to both the fluid or rock/mineral matrixes and should focuse on the exploration, exploitation or monitoring phases of the development of a geothermal system. Multi/inter-disciplinary studies are also strongly encouraged. 

Dr. Giovanni Vespasiano
Dr. Marco Taussi
Dr. Carmine Apollaro
Dr. Ilaria Fuoco
Guest Editors

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• geothermal energy
• geochemical analysis
• fluid chemistry
• isotopic composition
• geothermal fluids
• rock geochemistry
• alteration minerals
• geothermal reservoirs

Title: Biogenic Origin of Fe-Mn Crusts from Hydrothermal Fields of the Mid-Atlantic Ridge, Puy de Folles Volcano Region
Author: Sergienko
Highlights: Chemical and mineral composition of Fe-Mn crusts was determined. IR and GC-MS analysis showed the presence of alkanes, alkenes, gopanes. Magnetically, the material has a high coercivity with a phase transition temperature of 12 K; main carriers of magnetism are ultrafine particles about 10 nm in size. Ferromanganese crusts were formed as a result of bacterial mineralization processes.