detrital zircon geochronology of bonneville flood deposits along the ...

or in steeply dipping veins. These systems often produce economic Au-Agmineralization. They typically contain a base metal suite (such as Cu, Pb, and Zn) linkedto trace elements such as Au, Ag, Hg, As, Sb, Tl, etc. (White et al., 1992). Oxygenisotope ratios measured from epithermal minerals suggest they are derived from bothmagmatic sources as well as fluid interaction with the country rock (Faure and Mensing,2005). Heald et al. (1987) acknowledge the importance of caldera settings for youngerepithermal deposits because of extensive fracturing.Field AreaTuff of Sulphur Creek (TSC) is located on the northeast rim of the YellowstoneCaldera (Figures 2 and 3). Most of TSC was deposited inside the Yellowstone Caldera,although some of the tuff is located outside of the caldera. The field area for this studywas along the south fork of Sulphur Creek (Figure 5). Sulphur Creek is a tributary to theYellowstone River and flows from west to east, parallel to the caldera margin, into theGrand Canyon of the Yellowstone River. Sulphur Creek canyon, which has been (and isactively being) eroded by Sulphur Creek, slopes gently to the east, steepeningdramatically towards the confluence of the north and south forks (Figure 4). Outcrops inthe canyon consist of large, discontinuous whitish-yellow walls except for Outcrops 2and 5, which are small, grey, silicified outcrops (Figure 15).PurposeThere are two main purposes for studying Tuff of Sulphur Creek (TSC) in andadjacent to the Grand Canyon of the Yellowstone River. The first is to study a low δ 18 Opost-caldera pyroclastic flow from an unaltered deposit through hydrothermal alteration.2