Hydrothermal alteration in research drill hole Y-6, Upper Firehole River, Yellowstone National Park, Wyoming
Bargar KF and Beeson MH. 1984. Hydrothermal alteration in research drill hole Y-6, Upper Firehole River, Yellowstone National Park, Wyoming. U.S. Geological Survey (USGS) Professional Paper. 1054-B. Washington, D.C.
Y-6, a U.S. Geological Survey research diamond-drill hole in the upper Firehole River area of Yellowstone National Park, Wyoming, penetrated a surface covering of Pinedale glacial sediments and about 130 m of the Scaup Lake flow of the Upper Basin Member of the Pleistocene Plateau Rhyolite. The groundmass of the rhyolite flow has been extensively devitrified to *-cristobalite and sanidine, and vapor-phase zones contain granophyric quartz, alkali feldspar, and some magnetite and tridymite. Abundant fractures, possibly related to Mallard Lake resurgent doming, are mostly filled (self-sealed) by hydrothermal minerals, dominantly chalcedony. Other hydrothermal minerals deposited along fractures and in cavities in the drill core include quartz, zeolite minerals (clinoptilolite, dachiardite, intermediate heulandite, and mordenite), iron and manganese carbonate minerals (Mn-calcite, Ca- and Ferhodochrosite, rhodochrosite, and siderite), apatite, iron sulfides (pyrite and marcasite), iron oxides and hydroxides (goethite and hematite), clay minerals (iron-rich chlorite, kaolinite, mixed-layer illite-smectite and smectite) and a 10-A mica. There is some indication that the waters flowing through the Y-6 drill core previously were warmer and cooled to the present temperatures due to self-sealing coupled with the downward percolation of cold meteoric water. Adularia and bladed calcite in open-space deposits may have formed at an earlier time from boiling of the thermal water that led to a loss of CO2 and an increase in pH. Fluorite, which was deposited later than calcite, probably formed due to decreasing solubility as the temperature decreased. Fluid inclusion studies of four samples show a wide range of homogenization temperatures that are significantly warmer than the measured temperature curve.
- Type
- Published Report
- Authors
- Bargar, Keith; Beeson, Melvin
- Date of Issue
- 1984
- Units
- HIST , YELL
- Keywords
- 10-A mica, Apatite, Calcite, Carbonate minerals, chalcedony, chlorite, Clay and mica minerals, dachiardite, ehistory, fluorite, Geology, Glacial Deposits, Hematite and goethite, History, Hydrothermal Alteration, Illite-smectite, Iron oxides and suldifes, Kaolinite, Manganese-calcite, marcasite, mordenite, pyrite, Quarts, Rhodochrosite, siderite, silica minerals, Smectitie, Stratigraphy, Volcanic Rocks, Zeolite minerals