Mineralogical Studies of the Hydrothermal System in Newberry Volcano Drill Hole 2, Oregon

Abstract

Studies of secondary mineral distribution, whole rock chemical compositions, isotopes, and fluid inclusions are being conducted on the core from Newberry Volcano drill hole 2. Rocks from the drill core are divided into 3 major intervals on the basis of their alteration pattern, which is controlled by rock permabilities, primary lithologies, and temperatures. Incomplete alteration of pumice rick lithic tuff layers in the upper part of the altered section and lack of self sealing in fractures of most lava flows suggest that the hydrothermal system is young. Most of the secondary minerals could have been formed at temperatures near those present today; maximum measured temperature was 265°C at the bottom of the hole. Fluid inclusions indicated that past temperatures in the deeper part of the drill hole may have been as much as 100°C hotter than presently measured temperatures.