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Terry E.C. Keith

Publications and source records attributed to Terry E.C. Keith.

15 recordsLinked to original sources
USGS2024

Zeolites in Eocene basaltic pillow lavas of the Siletz River Volcanics, Central Coast Range, Oregon

Zeolites and associated minerals occur in a tholeiitic basaltic pillow lava sequence that makes up part of the Eocene Siletz River Volcanics in the central Coast Range, Oregon. Regional zoning of zeolite assemblages is not apparent; the zeolites formed in joints, fractures, and interstices, although most occur in central cavities of basalt pillows. The zeolites and associated minerals identified, in general order of paragenetic sequence, are smectite, pyrite, calcite (small spheres), thomsonite, natrolite, analcime, scolecite, mesolite, stilbite, heulandite, apophyllite, chahazite, mordenite, calcite (scalenohedra and twinned rhombohedra), laumontite, and amethystine quartz. Common three-mineral assemblages are: natrolite-analcime-sfilbite, stilbite-heulandite-chabazite, stilbite-apophyllie-chabazite, and natrolite-mesolite-laumontite. Alteration of basaltic glass, which was initially abundant, appears to have been an important factor in formation of the zeolites. Isotopic data suggest that zeolitization occurred during a low-temperature (60 ~ 70°C submarine hydrothermal event, or by reactions of cold (~ 10°C meteoric water with basalt over a long time. The occurrence of different mineral assemblages in cavities of adjacent basalt pillows indicates that these minerals crystallized in dosed systems that were isolated as fractures and joints were sealed by deposition of smectite and early zeolites. Although the total chemical composition of the mineral assemblages in cavities is similar, different mineral species formed because of the sensitivity of zeolite minerals to slight variations in physical and chemical conditions within individual cavities.

Clays and Clay Minerals↗
USGS2010

Volcano collapse promoted by progressive strength reduction: New data from Mount St. Helens

Rock shear strength plays a fundamental role in volcano flank collapse, yet pertinent data from modern collapse surfaces are rare. Using samples collected from the inferred failure surface of the massive 1980 collapse of Mount St. Helens (MSH), we determined rock shear strength via laboratory tests designed to mimic conditions in the pre-collapse edifice. We observed that the 1980 failure shear surfaces formed primarily in pervasively shattered older dome rocks; failure was not localized in sloping volcanic strata or in weak, hydrothermally altered rocks. Our test results show that rock shear strength under large confining stresses is reduced ∼20% as a result of large quasi-static shear strain, as preceded the 1980 collapse of MSH. Using quasi-3D slope-stability modeling, we demonstrate that this mechanical weakening could have provoked edifice collapse, even in the absence of transiently elevated pore-fluid pressures or earthquake ground shaking. Progressive strength reduction could promote collapses at other volcanic edifices.

Washington↗
USGS2008

Database of the geology and thermal activity of Norris Geyser Basin, Yellowstone National Park

This dataset contains contacts, geologic units and map boundaries from Plate 1 of USGS Professional Paper 1456, 'The Geology and Remarkable Thermal Activity of Norris Geyser Basin, Yellowstone National Park, Wyoming.' The features are contained in the Annotation, basins_poly, contours, geology_arc, geology_poly, point_features, and stream_arc feature classes as well as a table of geologic units and their descriptions. This dataset was constructed to produce a digital geologic map as a basis for studying hydrothermal processes in Norris Geyser Basin. The original map does not contain registration tic marks. To create the geodatabase, the original scanned map was georegistered to USGS aerial photographs of the Norris Junction quadrangle collected in 1994. Manmade objects, i.e. roads, parking lots, and the visitor center, along with stream junctions and other hydrographic features, were used for registration.

Data Series↗
USGS1996

Hydrothermal alteration mineralogy of SOH drill holes, Kilauea East Rift Zone geothermal area, Hawaii

Thirty-eight hydrothermal minerals were identified from 356 drill-core specimens that were obtained from three Scientific Observation Holes (SOH-1, SOH-2, and SOH-4) drilled along the lower East Rift Zone (ERZ) of Kilauea Volcano, Hawaii. The minerals formed during alteration of basaltic rocks and glass by hot, circulating, waters in aquifers consisting of variable mixtures of meteoric water and sea water. Several zeolites, hydrated calcium silicates, carbonates, clays, silicates, sulfates, sulfides, and other minerals were found filling open spaces of vesicles, fractures, and between breccia fragments of the recovered drill core; many specimens that originally consisted of glass are completely altered to some of these minerals, especially clays. Several hydrothermal minerals (erionite, mordenite, truscottite, smectite, chlorite-smectite, chalcedony, anhydrite, and hematite), occur in the SOH drill holes at higher measured temperatures than the same minerals are found in geothermal drill holes of Iceland or other geothermal areas, suggesting that temperatures within the ERZ geothermal system have increased since the minerals formed. Fluid-inclusion freezing data for quartz, anhydrite, and calcite from the three SOH holes show that composition of the inclusion fluids ranges from dilute meteoric water to highly modified sea water concentrated by boiling. Comparison of measured drill-hole temperatures with fluid-inclusion homogenization-temperature data indicates that only about 15% of the fluid inclusions could have formed under the present thermal conditions. The majority of fluid inclusions studied apparently formed during one or more temperature fluctuations associated with the emplacement of nearby dikes and their subsequent cooling. Bacteria-like particles at 1734.6 m depth in SOH-4 could be very significant because the particles occurred at much hotter temperatures (about 265°C) than the generally accepted 110°C limit for survival of bacteria. The presence of Cl in the particles suggests that they might have lived in a saline environment and did not result from contamination by the fresh water drilling fluids. We reccomend that future drilling and subsequent handling of drill hole specimens in the ERZ and elsewhere employ controls to minimize and(or) recognize bacterial contamination.

Open-File Report↗
USGS1988

The Geology and Remarkable Thermal Activity of Norris Geyser Basin, Yellowstone National Park, Wyoming

Norris Geyser Basin, normally shortened to Norris Basin, is adjacent to the north rim of the Yellowstone caldera at the common intersection of the caldera rim and the Norris-Mammoth Corridor, a zone of faults, volcanic vents, and thermal activity that strikes north from the caldera rim to Mammoth Hot Springs. An east-west fault zone terminates the Gallatin Range at its southern end and extends from Hebgen Lake, west of the park, to Norris Basin. No local evidence exists at the surface in Norris Basin for the two oldest Yellowstone volcanic caldera cycles (~2.0 and 1.3 m.y.B.P.). The third and youngest cycle formed the Yellowstone caldera, which erupted the 600,000-year-old Lava Creek Tuff. No evidence is preserved of hydrothermal activity near Norris Basin during the first 300,000.years after the caldera collapse. Glaciation probably removed most of the early evidence, but erratics of hot-spring sinter that had been converted diagenetically to extremely hard, resistant chalcedonic sinter are present as cobbles in and on some moraines and till from the last two glacial stages, here correlated with the early and late stages of the Pinedale glaciation <150,000 years B.P.). Indirect evidence for the oldest hydrothermal system at Norris Basin indicates an age probably older than both stages of Pinedale glaciation. Stream deposits consisting mainly of rounded quartz phenocrysts of the Lava Creek Tuff were subaerial, perhaps in part windblown and redeposited by streams. A few small rounded pebbles are interpreted as chalcedonic sinter of a still older cycle. None of these are precisely dated but are unlikely to be more than 150,000 to 200,000 years old. ...Most studies of active hydrothermal areas have noted chemical differences in fluids and alteration products but have given little attention to differences and models to explain evolution in types. This report, in contrast, emphasizes the kinds of changes in vents and their changing chemical types of waters and then provides models for explaining these differences. Norris Basin is probably not an independent volcanic-hydrothermal system. The basin and nearby acid-leached areas (from oxidation of H2S-enriched vapor) are best considered as parts of the same system, extending from Norris Basin to Roaring Mountain and possibly to Mammoth. If so, are they parts of a single large system centered within the Yellowstone caldera, or are Norris Basin and the nearby altered areas both parts of one or more young independent corridor systems confined, at least in the shallow crust, to the Norris-Mammoth Corridor? Tentatively, we favor the latter relation, probably having evolved in the past ~300,000 years. A model for large, long-lived, volcanic-hydrothermal activity is also suggested, involving all of the crust and upper mantle and using much recent geophysical data bearing on crust-mantle interrelations. Our model for large systems is much superior to previous suggestions for explaining continuing hydrothermal activity over hundreds of thousands of years, but is less attractive for the smaller nonhomogenized volcanic system actually favored here for the Norris-Mammoth Corridor.

Professional Paper↗
USGS1988

Hydrothermal alteration patterns in the Breitenbush Hot Springs area, Cascade Range, Oregon

Rocks of early Miocene age in the Breitenbush Hot Springs area have been affected by at least two major episodes of hydrothermal alteration, one of which had temperatures in excess of 200??C. Alteration minerals in younger Tertiary rocks are characteristic of temperatures below 100??C. The most important factor in controlling alteration is fracture permeability. The best guide to interpreting alteration is secondary mineralogy of volcaniclastic and pyroclastic rocks, flow breccia, and vesiculated or fractured lavas; alteration effects in interbedded massive lava flows are much more subtle.

Conference Paper↗
USGS1984

MINERALOGICAL STUDIES OF THE HYDROTHERMAL SYSTEM IN NEWBERRY VOLCANO DRILL HOLE 2, OREGON.

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 permeabilities, primary lithologies, and temperatures. Incomplete alteration of pumice-rich 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 degree C at the bottom of the hole. Fluid inclusions indicate that past temperatures in the deeper part of the drill hole may have been as much as 100 degree C hotter than presently measured temperatures.

Conference Paper↗
USGS1974

Ultramafic rocks of the Eagle quadrangle, east-central Alaska

More than 97 separate occurrences of ultramafic rocks, some of which are included in a north west-trending zone of alpine-type ultramafic rocks, have been mapped in the Eagle quadrangle, east-central Alaska. They are divided into three groups primarily on the basis of degree of serpentinization. Group I consists of lens-shaped bodies of serpentinite 1 m 2 (10 ft 2 ) to several 100 m 2 (1,000 ft 2 ) in area. Relict textures and presence of bastite indicate that the original rock was harzburgite and dunite. Group II consists of bodies composed of partially serpentinized harzburgite and dunite and includes the large Mount Sorenson and American Creek bodies. Group III is dominantly hornblendite and pyroxenite, probably intrusive and not genetically related to groups I and II. The authors believe that the ultramafic bodies of groups I and II are alpine-type peridotites and may include dismembered ophiolitc. The Tintina fault system could have provided a zone of weakness along which mantle material was tectonically emplaced or it may have been a plate boundary in late Paleozoic time. If it represents a plate boundary, the metamorphic terrane which lies between the Tintina and Denali fault systems would have to be allochthonous, perhaps originating as a northward-moving slice of continental crustal material. During the course of the movement as the two continental masses approached and perhaps collided, mantle peridotite and oceanic crustal material were squeezed up along the continental margin onto the continental slice.

Alaska↗