| Abstract |
A conceptual model for Fly Ranch hot springs suggests that fractures held open near an active fault intersection provided the pathway for initial circulation of water deep into the thinning hot crust. Competing fault offsets jammed the intersection, locking movement, such that remnant extensional stresses, not released in fault offset, hold the cracks open to depth. Recent and glacial-age cold waters organized to flow down some of these open cracks and buoyantly rise in others in a single-pass circulation pattern. Circulating water gains heat at depth while cooling and shrinking the rock, causing further opening of deep fractures. Hot water dissolves limestone along fracture pathways as it rises, charging the water with calcium and carbonate ions. These ions subsequently re-deposit as travertine in spires at a cluster of hot water vents near the summit of a broad travertine mound about 1 km in diameter and 40 meters thick. The upflow feeds a shallow hot aquifer underlying the travertine mound and extending to the southwest (SW). Other hot aquifers may occur at greater depth. Fractures held open by active stresses and deep-water circulation resulted in hydrothermal permeability feedbacks that support long-lived hot water flow to the surface. The consistent flow of heat and water in turn supports a vibrant and consistent living habitat. The surface springs and poolside evaporative zones are also open to cosmic fallout and solar energy. This combination of hot spring habitat and cosmic input may have nurtured the beginning of life in volcanic zones in the early earth. |