Fault Zones Intersections and High-Temperature Geothermal Exploration: 3D Modeling of the Chaudes-Aigues Area (French Massif Central)
Résumé
This study investigates the role of fault zone intersections in enhancing geothermal potential, focusing on the Chaudes-Aigues hydrothermal system in the French Massif Central. Located at the intersection of major Variscan fault zones, the site hosts over 30 hot springs, including the Par Spring (82 °C). Despite the low natural permeability of crystalline rocks, intersecting fault zones are thought to significantly increase fluid flow and heat transport. To assess this, we conducted a series of 3D numerical models simulating different fault zone configurations (single fault zone, X-shaped, and Y-shaped geometries), varying intersection angles and permeability values. Results reveal that fault intersections facilitate thermal convection at lower permeabilities than single fault zones. X-shaped and Yshaped configurations enhance flow compared to isolated fault zones, although they may lead to cooler surface temperatures at the extremities due to dominant cold inflows at higher permeabilities at the intersection. Back to the Chaudes-Aigues case, the Y-shaped model explains the spring emergence location but underestimates surface temperatures and flow rates. Our findings highlight the structural influence of fault intersections on geothermal systems and offer new insights for targeting high-temperature resources in amagmatic, crystalline settings.
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