Hydrothermal alteration in research drill hole Y-6, Upper Firehole River, Yellowstone National Park, Wyoming

Abstract

Bl Introduction ___________________________ 1 Acknowledgments _____________________ 2 Stratigraphy __________________________ 2 Glacial sediments _____________________ 2 Volcanic rocks _______________________ 2 Hydrothermal alteration ____________________ 4 Silica minerals ________________________ 4 «-and j8-cristobalite __________________ 4 Quartz and chalcedony _______________ 5 Potassium feldspar __________________ 6 Zeolite minerals ______________________ 7 Heulandite-group minerals ____________ 7

Geophysical imaging of shallow degassing in a Yellowstone hydrothermal system

“…Because seismic velocities and resistivity are sensitive to different physical properties, a comparison between them can provide insight into subsurface structure and gas/water content. The overall low V P and V S velocities observed along the line tend to agree with borehole observations of moderately cemented glacial tills in the upper 18 m [ Bargar and Muffler , ]. At shallow depths (<6 m) beneath the hill (from 70 to 220 m), high resistivity, low V P and V S , and low Poisson's ratio values can be explained by high‐porosity, unsaturated soils, as seen in the rock physics model.…”

“…For each point of our model with defined V P and V S values, we performed a grid search on porosities and saturations by using the Hertz‐Mindlin rock physics model and looked for the porosities and saturations best fitting both V P and V S . After trial and error tests and assuming an altered rhyolitic composition [ Bargar and Muffler , ], the elastic properties of the solid frame were modeled with 40% quartz, 10% feldspar, and 50% clay. Porosity and saturation ranged from 0 to 0.6 and from 0 to 1, respectively, both with a step of 0.025.…”

“…The Mud Volcano thermal area mainly consists of rhyolitic ash flow tuff covered with varying thicknesses of glacial silts, sand, and gravel [ Christiansen and Blank , ]. In the Y‐11 borehole drilled in the area by the U.S. Geological Survey, rhyolitic ash flow tuffs are covered with approximately 18 m of fluvial sediments and glacial tills, mostly of rhyolitic composition [ Bargar and Muffler , ]. The area is characterized by extensive diffuse degassing of CO 2 through soils [ Werner et al , ; Werner and Brantley , ] and hosts several isolated thermal features.…”

Modular Microporous Minerals: Cancrinite-Davyne Group and C-S-H Phases

“…Truscottite was also found in drill cores from hot spring and geyser areas of Yellowstone National Park (Bargar et al 1981); at Hishikani deposit, Kagoshima Prefecture, Japan (Izawa and Yamashita 1995); in deep drill hole at Kilauea Volcano (Grose and Keller 1976). Lachowski et al (1979) carried out a wide chemical and crystallographic study on specimens of natural and synthetic truscottite and, taking into account the results of the structural study of reyerite (Merlino 1972), defi nitely established the crystal chemical formula Ca 14 Si 24 O 58 (OH) 8 ·2H 2 O.…”

“…It was fi rst found in Skye, Scotland, by Anderson (1851), who indicated its approximate composition and was subsequently identifi ed in several other localities, generally in association with calcite, zeolites and other calcium silicate hydrates, as okenite, tacharanite, tobermorite, xonotlite. It mainly occurs in vugs and amygdules related to the latest crystallization stages of basaltic rocks; but it was also found within andesitic tuffs (Kobayashi and Kawai 1974); in drill cores from Yellowstone Park, USA, within hydrothermally altered sediments, pyroclastites and rhyolitic fl ows (White et al 1975;Bargar et al 1981) together with zeolites and calcium silicate hydrates; as very uncommon mineral in some ore deposits, as in the iron sulfi des ore deposit of Ortano, Island of Elba, Italy (Garavelli and Vurro 1984) and in hydrothermally metamorphosed limestone at Bingham copper mine, Utah, USA (Stephens and Bray 1973).…”