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  • 1
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    Elsevier
    In:  Amsterdam, I-VII + 329 pp., Elsevier, vol. 1, no. Publ. No. 12, pp. 127, (ISBN 3-540-44363-0)
    Publication Date: 1980
    Keywords: Geothermics ; application ; and ; prospection ; Earthquake hazard ; nuclear ; power ; plants ; Earthquake risk ; solar ; Energy (of earthquakes) ; pollution ; FROTH ; pp. ; 1-81, ; 279-288
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  • 2
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    Elsevier
    In:  Amsterdam, 298 pp., Elsevier, vol. 70, no. Publ. No. 12, pp. 1039-1054, (ISBN 0-444-50971-2)
    Publication Date: 2001
    Keywords: Subduction zone ; Review article ; Hypocentral depth ; Fault plane solution, focal mechanism ; Seismicity ; Mineralogy ; Hilst ; triggering ; Stress ; Rheology ; Geochemistry ; Strength ; Fluids ; ConvolutionE
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  • 3
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    Elsevier
    In:  Amsterdam, Elsevier
    Publication Date: 1980
    Keywords: Seismology ; Seismics (controlled source seismology) ; Wave propagation ; Waves ; Textbook of geophysics
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  • 4
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    Elsevier
    In:  Amsterdam, 356 pp., Elsevier, vol. 2, no. XVI:, pp. 1-14, (ISBN: 0-387-30752-4)
    Publication Date: 2001
    Keywords: Textbook of engineering ; Textbook of geophysics ; Statistical investigations
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  • 5
    Publication Date: 2017-09-26
    Description: In order to develop the potential tool of diatom oxygen isotopes for paleoenvironmental studies we compared oxygen isotopes of natural marine diatoms sampled from ocean surface water, sediment traps and surface sediments with oxygen isotopic fractionations determined for laboratory diatom cultures. Freshly grown natural diatoms (phytoplankton samples and sediment trap material) and cultured diatoms reveal similar oxygen isotope fractionation factors. The fresh diatoms have 3 to 10 parts per thousand lower isotope fractionation factors than fossil (sedimentary) diatoms. A temperature-related oxygen isotope fractionation could not be established for the laboratory cultures (and the natural phytoplankton samples), and there is evidence that diatom growth rate until reaching the stationary growth state also controls the measured silica-water oxygen isotope fractionation factor. It is possible, however, that slow diatom growth in sea surface water may well lead to a temperature-dependent silica-water oxygen isotope fractionation which is the prerequisite for a use of diatom oxygen isotopes in palco-surface water studies. FTIR-spectroscopic analyses of various diatomaceous materials revealed that the ratio of integrated peak intensities for Si-O-Si/Si-OH correlates with the 3 to 10 parts per thousand delta O-18(silica) increase from fresh to fossil diatoms. Open-system (flow-through) silica dissolution experiments suggest that the diatom frustules are isotopically homogenous and that the increase in O-18 is therefore not due to dissolution of isotopically light surficial Si-OH groups. It is concluded that slow internal condensation reactions during silica maturation in surface sediments cause both an increase in the intensity ratio of Si-O-Si/Si-OH and the O-18 content of framework oxygen. These findings also indicate that the oxygen isotope compositions of marine sediment diatoms do not indicate sea surface water temperature but rather reflect variable O-18 contents of surface sediments. Copyright (C) 2001 Elsevier Science Ltd.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2017-12-11
    Description: ODP Leg 189 was designed to test the hypothesis that opening of the Tasmanian Seaway and initiation of circumpolar circulation contributed to the thermal isolation of Antarctica, leading to the development of initial ice-sheet and oceanic thermohaline circulation. The clay assemblages of the Tasmanian region contain the traces of two tectonic stages associated with ocean opening south of the south Tasman Rise near the Palaeocene–Eocene boundary and strike-slip activity between the western Tasmanian land-bridge and Antarctica during the Late Eocene. Earliest Oligocene clays indicate that cooling of Antarctic margins and activity of western boundary circulation progressed with the regional subsidence.
    Type: Article , PeerReviewed
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  • 7
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    Elsevier
    In:  Journal of Volcanology and Geothermal Research, 7 (1-2). pp. 107-137.
    Publication Date: 2016-09-12
    Description: Glass separates from 115 ash layers derived from the Kamchatkan (DSDP Site 192; 34 layers), the eastern Aleutian (DSDP Site 183; 56 layers) and the Alaska Peninsula (DSDP Site 178; 25 layers) volcanic arcs have been analyzed for up to 28 elements. In addition, the abundance and diversity of associated mafic phenocrysts have been evaluated. The resulting data set has made possible an evaluation of the late Miocene to Recent changes in composition of ashes derived from North Pacific volcanic arcs and of the factors controlling the evolution of highly siliceous magmas. We find no evidence for a general transition from arc tholeiite to calc-alkalic magma parentage of ashes derived from the volcanic arcs during the last 10 m.y., but instead find 0.1- to 0.5-m.y. intervals during which particular types of volcanism are prevalent. Most convincing is the transition from arc tholeiite to calc-alkalic for ashes derived from Kamchatka during the last 0.8 m.y., a change believed to be associated with a landward shift in the site of magma generation. Considered together, ashes derived from North Pacific volcanic arcs have been becoming more siliceous during the last 1.5 m.y. and may be associated with accelerated subduction during the same time interval. Hydrous phenocrysts (e.g., biotite) are typically associated with low-silica deep-sea ashes, but not with terrestrial volcanic rocks of comparable silica contents, suggesting the important role of water in the evolution of siliceous magma. REE patterns and relative abundances of mafic phenocrysts demonstrate the importance of fractional crystallization in controlling the evolution of highly siliceous arc magmas. REE increase with increasing silica, but become less concentrated in ashes with SiO2 〉 64%. Eu anomalies increase throughout the SiO2 range. Initial fractionation is dominated by clinopyroxene and plagioclase with amphibole strongly influencing fractionation above 64% SiO2.
    Type: Article , PeerReviewed
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  • 8
    Publication Date: 2020-08-05
    Description: As part of the OMEX I project, nutrient determinations were made on 17 cruises in the region of the Goban Spur and La Chapelle Bank between 46 and 51°N, in all seasons of the year, between 1993–1995. Over this period no change was detectable in the structure of the water masses below the deep winter mixed layer. The N : P (dissolved nitrate-to-phosphate) ratio changed from 16 at 100-m depth to less than 15 at 3300-m depth. At intermediate depths nutrient and oxygen data indicate the presence of Mediterranean Outflow water overlying Labrador Sea Water at its most eastern extension. Estimated maximum levels of production in the spring bloom are the total N-limited new primary production equivalent between 24 and 41 gC m−2, the equivalent maximum diatom production is 11 gC m−2. Measurements during the spring bloom suggest a conversion factor of 1 μM nitrate to 1 μg l−1 chlorophyll, at the shelf break, which is consistent with other recent measurements in European shelf seawaters. Sediment trap data suggest that 80% (5.4 g m−2) of the opal produced in the spring bloom dissolved before reaching the sediment trap at 600 m. A comparison of the winter and summer profiles for dissolved silicon suggests a similar dissolution of 9±3 g opal m−2 above 300-m depth. Measurements of dissolved organic carbon (DOC) in September 1994 show an enrichment of 7 μM-C above the seasonal thermocline relative to the winter values (52±4 μM). In winter dissolved organic nitrogen represents 40% of the pool of total dissolved nitrogen. There is no consistent evidence of an increase in the concentration of DON during summer. Measurements of nitrate in surface waters in January 1994 show that concentrations off-shelf vary with the temperature of the water and are related to the depth of winter mixing. Mixing in surface waters is discontinuous at the shelf break, demonstrating the degree to which exchange across the shelf break is limited even in winter. OMEX winter measurements of nitrate concentrations can be used to estimate the flow of water across the shelf break that would be required to maintain the nitrogen balance in the North Sea at a steady state. The estimate is 0.6 Sv (1 Sv=106 m3 s−1), which is similar to an earlier estimate of a total flow of 1.7 Sv based on salt budgets (cf. Huthnance, Deutsche Hydrographische Zeitschrift, 49 (1997) 153).
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2016-05-11
    Description: Ultramafic, mafic and sedimentary xenoliths have been recovered from a recently erupted, shoshonitic submarine cinder cone (Tubaf and Edison volcanoes) from the Tabar–Lihir–Tanga–Feni island arc, located in the New Ireland basin of Papua New Guinea. These samples represent a proxy drill hole that can be re-assembled into an ‘ophiolite-type’ model of oceanic lithosphere. Petrographic and geochemical examination of the gabbroic and depleted mantle xenoliths indicates that the New Ireland fore-arc lithosphere is a fragment of ancient Pacific Plate generated at a mid-ocean ridge spreading centre and transported to the Pacific–Australian Plate margin. Convergent margin processes subjected the harzburgitic mantle wedge to hydrofracturing and hydration metasomatism at T=790–1030°C as a consequence of dewatering of a subducted slab. Advection of a high-density, H2O-rich fluid containing a substantial dissolved component (alkali aluminosilicate melt and aqueous carbon and sulphur species) through these mantle fractures caused a net transfer of soluble elements from the lower to upper mantle wedge and created a network of oxidised (ΔFMQ≈1.8–2.0) metasomatised peridotite enriched in orthopyroxene, clinopyroxene, phlogopite, amphibole, magnetite, and Fe–Ni sulphides. The vein mineral assemblage magnetite+sulphide indicates precipitation from a hydrous fluid with high SO2/H2S, consistent with the hydrous fluid being derived from dehydration of subducted, altered oceanic crust. Preferential partial melting of these metasomatically enriched mantle wedge regions could account for the highly oxidised, sulphur- and alkali-rich nature of the high-K calc-alkaline volcanoes of the Tabar–Lihir–Tanga–Feni island chain.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2018-01-02
    Description: High-temperature (250°C) hydrothermal vents and massive anhydrite deposits have been found in a shallow water, sediment-filled graben near 66°36′N in the Tjornes Fracture Zone north of Iceland. The site is located about 30 km offshore, near the small island of Grimsey. The main vent field occurs at a depth of 400 m and consists of about 20 large-diameter (up to 10 m) mounds and 1–3 m chimneys and spires of anhydrite and talc. A north–south alignment of the mounds over a 1-km strike length of the valley floor suggests that their distribution is controlled by a buried fault. Widespread shimmering water and extensive white patches of anhydrite in the sediment between the mounds indicates that the entire 1-km2 area occupied by the vents is thermally active. A 2-man research submersible JAGO was used to map the area and to sample vent waters, gases, and chimneys. Actively boiling hydrothermal vents occur on most of the mounds, and extensive two-phase venting indicates that the field is underlain by a large boiling zone (200×300 m). The presence of boiling fluids in shallow aquifers beneath the deposits was confirmed by sediment coring. The highest-temperature pore fluids were encountered in talc- and anhydrite-rich sedimentary layers that occur up to 7 m below the mounds. Baked muds underlie the talc and anhydrite layers, and pyrite is common in stockwork-like fractures and veins in the hydrothermally altered sediments. However, massive sulfides (pyrite–marcasite crusts) were found in only one relict mound. Subseafloor boiling has likely affected the metal-carrying capacity of the hydrothermal fluids, and deposition of sulfides may be occurring at greater depth. Although the mounds and chimneys at Grimsey resemble other deposits at sedimented ridges (e.g. Middle Valley, Escanaba Trough, Guaymas Basin), the shallow water setting and extensive boiling of the hydrothermal fluids represent a distinctive new type of seafloor hydrothermal system.
    Type: Article , PeerReviewed
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