Year: 1986
Type: report
Abstract: 6EO N-l was drilled in November, 1985 by GEO-Newberry Crater, Inc., under a cost-sharing agreement with DOE, at a surface altitude of 1783 m on the south flank of Newberry Volcano, Oregon.Drill core, drilling data, and geophysical data from the upper 1219 m of 6EO N-l are available to the public; maximum measured temperature for the released interval is 71°C at 1219 m.The drill core intercepted mostly andesitic to basaltic lava flows with interlayers of ash-flow tuffs, lithic tuffs, cinders, and flow breccias; core recovery was about 95 percent.Twelve basalt dikes intrude the flows between 622 and 719 m but there is little alteration at the contacts.Intense fracturing and vesiculation are common in the basal and upper portions of most flows whereas the flow interiors are generally very dense with few fractures.Very little evidence for hydrothermal alteration was found in the upper 500 m of drill core; however, pre-hydrothermal, low temperature, amorphous clay-like material and amorphous silica occur as fracture or vug fillings.Below 500 m, most ash-flow tuffs contain smectite, and, although the lavas generally show little alteration, many fractures and vesicles are lined with secondary minerals: hematite, smectite, and carbonates (siderite, kutnohorite, dolomite, rhodochrosite, calcite, and aragonite).Locally, small amounts of 8-cristobalite, chalcedonyC?),chabazite, phillipsite, okenite, illiteC?), and pyrite were identified.The hydrothermal minerals were probably deposited at the <71°C temperatures measured following drilling of GEO N-l.
DOI: 10.3133/ofr86440
Authors: K.E. Bargar, T.E. Keith
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W57409815