Physical and hydraulic properties of modern sinter deposits: El Tatio, Atacama

Abstract

Sinters are siliceous, sedimentary deposits that form in geothermal areas. Formation occurs in two steps. Hot water circulates in the subsurface and dissolves silica from the host rock, usually rhyolites. Silica then precipitates after hot water is discharged and cools. Extensive sinter formations are linked to up-flow areas of fluids originating from high temperature (>175 °C) deep reservoirs. Fluid geochemistry, microbial communities, and environmental conditions of deposition determine the texture of sinter and pore framework. Porosity strongly influences physical and hydraulic properties of rocks. To better understand the properties controlling the transport of fluids, and interpret geophysical observations in geothermal systems, we studied 17 samples of modern geyserite sinter deposits (<10 ka) from the active El Tatio geothermal field in northern Chile. We measured the physical properties (hydraulic, seismic, and electrical), and internal microstructure (using μX-Ray computed tomography). We find that the pore structure, and thus hydraulic and physical properties, is controlled by the distribution of microbial matter. Based on velocity-porosity relationships, permeability-porosity scaling, and image analysis of the 3D pore structure; we find that the physical and hydraulic properties of sinter more closely resemble those of vesicular volcanic rocks and other

Geometry of Geyser Plumbing Inferred From Ground Deformation

“…The basins containing the geysers are filled with Miocene ignimbrites, andesitic volcanic agglomerates, and Plio‐Holocene dacitic and rhyolitic ignimbrites, and lavas (Marinovic & Lahsen, ). Glacial and alluvial deposits, and locally derived silica sinter deposits from the geysers, define the shallowest geology (e.g., Fernandez‐Turiel et al, ; Marinovic & Lahsen, ; Munoz‐Saez et al, ; Nicolau et al, ). Permeable ignimbrites host the geothermal reservoir feeding the geysers, which are underlain by low permeability andesitic rocks and capped by low permeability silica sinter deposits (Cusicanqui et al, ; Giggenbach, ).…”

The Fascinating and Complex Dynamics of Geyser Eruptions

“…The diagenesis, morphology, biota, and chemical composition of sinter deposits from many active thermal fields were summarized by Renaut & Jones (2011) and Campbell et al (2015). Physical properties of sinter, including porosity, permeability, seismic velocity and electrical conductivity, were reported by Munoz-Saez et al (2016). Siliceous sinter is absent around the geyser vents along the shores of Lake Bogoria because the discharged waters are undersaturated with respect to amorphous silica ( Table 1) (Renaut & Owen 2005).…”

An experimental study of the role of subsurface plumbing on geothermal discharge

“…The major geyser fields of Yellowstone, Geyser Valley, Kamchatka, Russia, and El Tatio, Chile are located on volcanic deposits with high permeability [e.g., Lahsen , ; Belousov et al ., ; Hurwitz and Lowenstern , ]. Although sinter precipitation might make permeability lower near the conduit [ Munoz‐Saez et al ., ], the high permeability of surrounding rocks should contribute to both removing heat from steam and interaction with cold water. The condensed water erupting onto the surface can drain into the subsurface by permeable flow, and cool surrounding rocks.…”