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Fluid-inclusion evidence for past temperature fluctuations in the Kilauea East Rift Zone geothermal area, Hawaii Fluid-inclusion evidence for past temperature fluctuations in the Kilauea East Rift Zone geothermal area, Hawaii

Heating and freezing data were obtained for fluid inclusions in hydrothermal quartz, calcite, and anhydrite from several depths in three scientific observation holes drilled along the lower East Rift Zone of Kilauea volcano, Hawaii. Compositions of the inclusion fluids range from dilute meteoric water to highly modified sea water concentrated by boiling. Comparison of measured drill-hole
Authors
Keith E. Bargar, Terry E.C. Keith, Frank A. Trusdell

San Andreas fault zone drilling project: scientific objectives and technological challenges San Andreas fault zone drilling project: scientific objectives and technological challenges

We are leading a new international initiative to conduct scientific drilling within the San Andreas fault zone at depths of up to 10 km. This project is motivated by the need to understand the physical and chemical processes operating within the fault zone and to answer fundamental questions about earthquake generation along major plate-boundary faults. Through a comprehensive program of...
Authors
S.H. Hickman, L.W. Younker, Mark D. Zoback

Roof-rock contamination of magma along the top of the reservoir for the Bishop Tuff Roof-rock contamination of magma along the top of the reservoir for the Bishop Tuff

The Bishop Tuff, a Quaternary high-silica rhyolite in east-central California, is widely considered the type example of a vertically and monotonically zoned pyroclastic deposit that represents zoning in the source magma reservoir, inverted during the process of pyroclastic emplacement. However, the deposit of plinian pumice, which forms the base of the Bishop Tuff and represents the...
Authors
W. A. Duffield, J. Ruiz, J.D. Webster

Decadal and annual changes in biogenic opal and carbonate fluxes to the deep Sargasso Sea Decadal and annual changes in biogenic opal and carbonate fluxes to the deep Sargasso Sea

Analyses of samples from a 14-year series of sediment-trap deployments in the deep Sargasso Sea reveal a significant trend in the ratio of the sinking fluxes of biogenic calcium carbonate and silica. Although there are pronounced seasonal cycles for both flux components, the overall opal/CaCO3 ratio changed by 50% from 1978 to 1991 (largely due to a decrease of opal flux), while total...
Authors
W.G. Deuser, T.D. Jickells, Judith A. Commeau

Inclusions in Mount St. Helens dacite erupted from 1980 through 1983 Inclusions in Mount St. Helens dacite erupted from 1980 through 1983

Inclusions of plutonic, metavolcanic and volcanic rocks are abundant in dacite pumice and lava from the 1980–1986 eruption sequence at Mount St. Helens. Point counts of inclusions exposed in talus blocks from the dome from 1980 through 1983 show that inclusions form approximately 3.5 vol% of the lava. Eighty-five percent of the inclusions are medium-grained gabbros with an average...
Authors
C. Heliker

Cooling, degassing and compaction of rhyolitic ash flow tuffs: A computational model Cooling, degassing and compaction of rhyolitic ash flow tuffs: A computational model

Previous models of degassing, cooling and compaction of rhyolitic ash flow deposits are combined in a single computational model that runs on a personal computer. The model applies to a broader range of initial and boundary conditions than Riehle's earlier model, which did not integrate heat and mass flux with compaction and which for compound units was limited to two deposits. Model...
Authors
J.R. Riehle, T.F. Miller, R. A. Bailey

Factors influencing the height of Hawaiian lava fountains: implications for the use of fountain height as an indicator of magma gas content Factors influencing the height of Hawaiian lava fountains: implications for the use of fountain height as an indicator of magma gas content

The heights of lava fountains formed in Hawaiian-style eruptions are controlled by magma gas content, volume flux and the amounts of lava re-entrainment and gas bubble coalescence. Theoretical models of lava fountaining are used to analyse data on lava fountain height variations collected during the 1983–1986 Pu'u 'O'o vent of Kilauea volcano, Hawaii. The results show that the variable...
Authors
E.A. Parfitt, L. Wilson, C.A. Neal
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