| Abstract |
The appropriate paragenetic sequence of hydrothermal minerals in the Y-3 U.S. Geological Survey research diamond rill hole in Lower Geyser Basin, Yellowstone National Park, Wyoming, is: hydrothermal chalcedony, hematite, pyrite, quartz, clay minerals (smectite and mixed layer illite-smectite), calcite, chlorite, fluorite, pyrite, quartz, zeolite minerals (analcime, dachiardite, laumontite, stilbite?, and yugawarlite), and clay minerals (smectite and mixed layer illite-smectite). A few hydrothermal mineral that were identified in drill core Y-3 (lepidolite, aegirine, pectolite, and truscottite) are rarely found in modern geothermal areas. The alternation minerals occur primarily as vug and fracture fillings that were deposited from cooling thermal water. |