All ICDP Publications with Abstracts
From parent-sysfolder "Publications" + 2 folder-levels deep
394.
Modeling of acoustic wave dissipation in gas hydrate-bearing sediments
Geochemistry, Geophysics, Geosystems,
6
(7)
2005
ISSN: 15252027Abstract: ▾ Recent sonic and seismic data in gas hydrate-bearing sediments have indicated strong waveform attenuation associated with a velocity increase, in apparent contradiction with conventional wave propagation theory. Understanding the reasons for such energy dissipation could help constrain the distribution and the amounts of gas hydrate worldwide from the identification of low amplitudes in seismic surveys. A review of existing models for wave propagation in frozen porous media, all based on Biot's theory, shows that previous formulations fail to predict any significant attenuation with increasing hydrate content. By adding physically based components to these models, such as cementation by elastic shear coupling, friction between the solid phases, and squirt flow, we are able to predict an attenuation increase associated with gas hydrate formation. The results of the model agree well with the sonic logging data recorded in the Mallik 5L-38 Gas Hydrate Research Well. Cementation between gas hydrate and the sediment grains is responsible for the increase in shear velocity. The primary mode of energy dissipation is found to be friction between gas hydrate and the sediment matrix, combined with an absence of inertial coupling between gas hydrate and the pore fluid. These results predict similar attenuation increase in hydrate-bearing formations over most of the sonic and seismic frequency range. Copyright 2005 by the American Geophysical Union.
393.
Microbial diversity in ultra-high-pressure rocks and fluids from the Chinese continental scientific drilling project in China
Applied and Environmental Microbiology,
71
(6)
3213 – 3227
2005
ISSN: 00992240Keywords:▾
Atmospheric Pressure; Bacteria; China; Crenarchaeota; Culture Media; DNA, Archaeal; DNA, Bacterial; DNA, Ribosomal; Ecosystem; Geologic Sediments; Geology; Minerals; Molecular Sequence Data; Phylogeny; Polymorphism, Restriction Fragment Length; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Asia; China; Eastern Hemisphere; Eurasia; Far East; World; Archaea; Bacteroidetes; Candidatus; Planctomycetes; Posibacteria; Proteobacteria; Sulfolobus solfataricus; Bacteria; Bioassay; Drilling; Fatty acids; High pressure effects; Iron; Magnetite; Phosphorus compounds; Porosity; RNA; Rocks; ferric ion; magnetite; nitrate; RNA 16S; sodium chloride; microbial community; alkalinity; article; bacterial flora; bacterial gene; Bacteriodetes; bacterium; Candidatus; China; controlled study; drill; gene sequence; geographic distribution; Gram positive bacterium; microbial diversity; nonhuman; nucleotide sequence; Planctomycetes; Proteobacteria; rock; Sulfolobus solfataricus; thermophilic bacterium; unindexed sequence; Gas inclusion; Microbial diversity; Prototypes; Ultra-high-pressure (UHP) rocks; Biodiversity
Abstract: ▾ Microbial communities in ultra-high-pressure (UHP) rocks and drilling fluids from the Chinese Continental Scientific Drilling Project were characterized. The rocks had a porosity of 1 to 3.5% and a permeability of ∼0.5 mDarcy. Abundant fluid and gas inclusions were present in the minerals. The rocks contained significant amounts of Fe2O3, FeO, P2O5, and nitrate (3 to 16 ppm). Acridine orange direct counting and phospholipid fatty acid analysis indicated that the total counts in the rocks and the fluids were 5.2 × 103 to 2.4 × 10 4 cells/g and 3.5 x 108 to 4.2 × 109 cells/g, respectively. Enrichment assays resulted in successful growth of thermophilic and alkaliphilic bacteria from the fluids, and some of these bacteria reduced Fe(III) to magnetite. 16S rRNA gene analyses indicated that the rocks were dominated by sequences similar to sequences of Proteobacteria and that most organisms were related to nitrate reducers from a saline, alkaline, cold habitat; however, some phylotypes were either members of a novel lineage or closely related to uncultured clones. The bacterial communities in the fluids were more diverse and included Proteobacteria, Bacteroidetes, gram-positive bacteria, Planctomycetes, and Candidatus taxa. The archaeal diversity was lower, and most sequences were not related to any known cultivated species. Some archaeal sequences were 90 to 95% similar to sequences recovered from ocean sediments or other subsurface environments. Some archaeal sequences from the drilling fluids were >93% similar to sequences of Sulfolobus solfataricus, and the thermophilic nature was consistent with the in situ temperature. We inferred that the microbes in the UHP rocks reside in fluid and gas inclusions, whereas those in the drilling fluids may be derived from subsurface fluids. Copyright © 2005, American Society for Microbiology. All Rights Reserved.
392.
Magnetization intensity mapping on Unzen Volcano, Japan, determined from high-resolution, low-altitude helicopter-borne aeromagnetic survey
Earth, Planets and Space,
57
(8)
743-753
2005
ISSN: 13438832
Publisher: Springer Berlin
Keywords:▾
aeromagnetic survey; cooling; lava flow; magnetic intensity; volcano, Asia; Eastern Hemisphere; Eurasia; Far East; Japan; Kyushu; Nagasaki [Kyushu]; Unzen Volcano; World
Abstract: ▾ On September 18, 2002, we conducted a high-resolution, low-altitude helicopter-bome aeromagnetic survey at two flight altitudes, using spiral trajectories for the first time, over Unzen Volcano in the framework of the Unzen Scientific Drilling Project (USDP). This study obtained more detailed and new information than the previous aeromagnetic studies in Unzen volcano about the geological features, for understanding the history and eruption mechanism of the Unzen volcano. Therefore, we conducted a magnetization intensity mapping on the volcano, on the assumption that the magnetic anomalies are caused by the terrain magnetized in the same direction as the present Earth's magnetic field and the magnetization intensity varies only laterally. This map shows good agreement with the geologic features, especially the hydrothermal alteration zone and the collapsed pyroclastic deposits. In addition, even in the area covered by lavas, the magnetization intensities show various values corresponding to each eruption event. It may be considered that the differences in magnetic properties reflect different oxygen fugacity in rocks during their cooling time period. Local magnetization lows on Heisei-Shinzan suggest that the Heisei lava produced by the 1991-1995 eruption has not yet been cooled enough. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.
391.
Lead isotopes reveal bilateral asymmetry and vertical continuity in the Hawaiian mantle plume
Nature,
434
(7035)
851-856
2005
ISSN: 00280836Keywords:▾
Composition; Geographical regions; Geophysics; Lead; Volcanoes, Isotopy; Lead isotopes; Mantle plume; Radiogenic isotopes, Radioisotopes, isotope; lead, isotopic composition; lava flow; lead; mantle plume, accuracy; article; chemical composition; evolution; geographic distribution; parameter; plume; priority journal; radioactivity; regression analysis; sampling; technique; theoretical model; United States; volcano, Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; Mauna Kea; Mauna Loa; North America; oceanic regions; Pacific islands; Pacific Ocean; United States; Western Hemisphere; World
Abstract: ▾ The two parallel chains of Hawaiian volcanoes ('Loa' and 'Kea') are known to have statistically different but overlapping radiogenic isotope characteristics. This has been explained by a model of a concentrically zoned mantle plume, where the Kea chain preferentially samples a more peripheral portion of the plume. Using high-precision lead isotope data for both centrally and peripherally located volcanoes, we show here that the 'two trends have very little compositional overlap and instead reveal bilateral, non-concentric plume zones, probably derived from the plume source in the mantle. On a smaller scale, along the Kea chain, there are isotopic differences between the youngest lavas from the Mauna Kea and Kilauea volcanoes, but the 550-thousand-year-old Mauna Kea lavas are isotopically identical to Kilauea lavas, consistent with Mauna Kea's position relative to the plume, which was then similar to that of present-day Kilauea. We therefore conclude that narrow (less than 50 kilometres wide) compositional streaks, as well as the larger-scale bilateral zonation, are vertically continuous over tens to hundreds of kilometres within the plume.
390.
Journey to the centre of a quake
New Scientist,
185
(2485)
42-45
2005
ISSN: 02624079Abstract: ▾ The San Andreas Fault Observatory at Depth (SAFOD) project to reveal various mysteries associated with an earthquake is discussed. By drilling directly into the fault, the researchers will be able to understand the causes of earthquakes. The results from SAFOD can help to refine the way scientists model earthquakes, and could even help determine the effective ways of predicting a quake's location, timing and size. All the activity is aimed at helping geophysicists understand the setting in which earthquakes develop and the factors that control them.
389.
Late Maastrichtian and K/T paleoenvironment of the eastern Tethys (Israel): Mineralogy, trace and platinum group elements, biostratigraphy and faunal turnovers
Bulletin de la Societe Geologique de France,
176
(1)
37-55
2005
DOI:10.2113/176.1.37
Abstract: ▾ The late Maastrichtian to early Danian at Mishor Rotem, Israel, was examined based on geochemistry, bulk rock and clay mineralogies, biostratigraphy and lithology. This section contains four red clay layers of suspect impact or volcanic origin interbedded in chalk and marly chalks. PGE anomalies indicate that only the K/T boundary red layer has an Ir dominated PGE anomaly indicative of an impact source. The late Maastrichtian red clays have Pd dominated PGE anomalies which coincide with increased trace elements of terrigenous and volcanogenic origins. Deccan or Syrian-Turkey arc volcanism is the likely source of volcanism in these clay layers. Glauconite, goethite and translucent amber spherules are present in the clay layers, but the Si-rich spherules reported by Rosenfeld et al. [1989] could not be confirmed. The absence of Cheto smectite indicates that no altered impact glass has been present. The red layers represent condensed sedimentation on topographic highs during sea level highstands. In the Negev area, during the late Maastrichtian, the climate ranged from seasonally wet to more arid conditions during zones CF3 and CF2, with more humid wet conditions in the latest Maastrichtian zone CF1 and in the early Danian, probably linked to greenhouse conditions. Planktic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids. Times of intensified stress are indicated by the disaster opportunist Guembelitria blooms, which can be correlated to central Egypt and also to Indian Ocean localities associated with mantle plume volcanism. Marine plankton thus support the mineralogical and geochemical observations of volcanic influx and reveal the detrimental biotic effects of intense volcanism.
388.
Principal features of impact-generated hydrothermal circulation systems: Mineralogical and geochemical evidence
Geofluids,
5
(3)
165-184
2005
Abstract: ▾ Any hypervelocity impact generates a hydrothermal circulation system in resulting craters. Common characteristics of hydrothermal fluids mobilized within impact structures are considered, based on mineralogical and geochemical investigations, to date. There is similarity between the hydrothermal mineral associations in the majority of terrestrial craters; an assemblage of clay minerals-zeolites-calcite-pyrite is predominant. Combining mineralogical, geochemical, fluid inclusion, and stable isotope data, the distinctive characteristics of impact-generated hydrothermal fluids can be distinguished as follows: (i) superficial, meteoric and ground water and, possibly, products of dehydration and degassing of minerals under shock are the sources of hot water solutions; (ii) shocked target rocks are sources of the mineral components of the solutions; (iii) flow of fluids occurs mainly in the liquid state; (iv) high rates of flow are likely (10-4 to 10-3 m s-1); (v) fluids are predominantly aqueous and of low salinity; (vi) fluids are weakly alkaline to near-neutral (pH 6-8) and are supersaturated in silica during the entire hydrothermal process because of the strong predominance of shock-disordered aluminosilicates and fusion glasses in the host rocks; and (vii) variations in the properties of the circulating solutions, as well as the spatial distribution of secondary mineral assemblages are controlled by temperature gradients within the circulation cell and by a progressive cooling of the impact crater. Products of impact-generated hydrothermal processes are similar to the hydrothermal mineralization in volcanic areas, as well as in modern geothermal systems, but impacts are always characterized by a retrograde sequence of alteration minerals. © 2005 Blackwell Publishing Ltd.
387.
Petrogenesis of UHP metamorphic rocks from Qinglongshan, southern Sulu, east-central China
Lithos,
81
(1-4)
189 – 207
2005
ISSN: 00244937Keywords:▾
Asia; China; Donghai; Eastern Hemisphere; Eurasia; Far East; Jiangsu; Sulu Belt; World; metamorphism; petrogenesis; petrology; ultrahigh pressure metamorphism
Abstract: ▾ Five kinds of UHP metamorphic rocks, including eclogite, orthogneiss, paragneiss, schist and quartzite are exposed in the Qinglongshan roadcut, southern Sulu orogenic belt of eastern central China. They comprise metamorphic supracrustal rocks with bimodal volcanic characteristics and continental affinity, and granitic intrusive associations. The preservation of coesite inclusions and/or its pseudomorphs in eclogite and other rocks indicate that they have been subjected to in-situ UHP metamorphism. Four stages of metamorphism were recognized by combining petrographic observations and compositions of minerals from various UHP rocks. Prograde epidote-amphibolite facies, UHP coesite-eclogite facies, post UHP quartz-eclogite facies, and retrograde amphibolite facies assemblages delineate an inferred P-T path with a clockwise trajectory and a retrograde event characterized by the coupling of decompression with a temperature decrease. Garnet porphyroblasts in UHP eclogites display a complex growth zoning and mineral distribution, and record a crucial segment of the prograde and retrograde metamorphic evolution. The preservation of growth zoning in eclogitic and gneissic garnets suggests that the UHP rocks had a short residence time before retrograde metamorphism and a very high uplift rate in order to preserve the prograde growth zoning. © 2004 Elsevier B.V. All rights reserved.
386.
The Expedition El'gygytgyn Lake 2003 (Siberian Arctic)
Berichte zur Polar-und Meeresforschung (Reports on Polar and Marine Research),
509
2005
385.
Quantitative reconstruction of the last interglacial vegetation and climate based on the pollen record from Lake Baikal, Russia
Climate Dynamics,
25
(6)
625 – 637
2005
ISSN: 14320894Keywords:▾
Eurasia; Lake Baikal; Russian Federation; Coniferophyta; climate change; Last Interglacial; pollen; reconstruction; vegetation history; vegetation type
Abstract: ▾ Changes in mean temperature of the coldest (Tc) and warmest month (Tw), annual precipitation (Pann) and moisture index (α) were reconstructed from a continuous pollen record from Lake Baikal, Russia. The pollen sequence CON01-603-2 (53°57′N, 108°54′E) was recovered from a 386 m water depth in the Continent Ridge and dated to ca. 130-114.8 ky BP. This time interval covers the complete last interglacial (LI), corresponding to MIS 5e. Results of pollen analysis and pollen-based quantitative biome reconstruction show pronounced changes in the regional vegetation throughout the record. Shrubby tundra covered the area at the beginning of MIS 5e (ca. 130-128 ky), consistent with the end of the Middle Pleistocene glaciation. The late glacial climate was characterised by low winter and summer temperatures (Tc ∼ -38 to -35°C and Tw∼11-13°C) and low annual precipitation (Pann∼300 mm). However, the wide spread of tundra vegetation suggests rather moist environments associated with low temperatures and evaporation (reconstructed α∼1). Tundra was replaced by boreal conifer forest (taiga) by ca. 128 ky BP, suggesting a transition to the interglacial. Taiga-dominant phase lasted until ca. 117.4 ky BP, e.g. about 10 ky. The most favourable climate conditions occurred during the first half of the LI. Pann reached 500 mm soon after 128 ky BP. However, temperature changed more gradually. Maximum values of Tc ∼-20°C and Tw ∼16-17°C are reconstructed from about 126 ky BP. Conditions became gradually colder after ca. 121 ky BP. Tc dropped to ∼ -27°C and T w to ∼15°C by 119.5 ky BP. The reconstructed increase in continentality was accompanied by a decrease in Pann to ∼400-420 mm. However, the climate was still humid enough (α∼0.9) to support growth of boreal evergreen conifers. A sharp turn towards a dry climate is reconstructed after ca. 118 ky BP, causing retreat of forest and spread of cool grass-shrub communities. Cool steppe dominated the vegetation in the area between ca. 117.5 ky and 114.8 ky BP, suggesting the end of the interglacial and transition to the last glacial (MIS 5d). Shift to the new glaciation was characterised by cool and very dry conditions with Tc ∼ -28 to -30°C, Tw ∼14-15°C, Pann ∼250 mm and α∼0.5. © Springer-Verlag 2005.
384.
The chemical structure of the Hawaiian mantle plume
Nature,
436
(7052)
837-840
2005
ISSN: 00280836Keywords:▾
Crystallization; Geochemistry; Olivine; Thermal plumes, Lithospheres; Mantle plumes; Olivine phenocryst; Volcanic islands, Volcanic rocks, trace element, chemical composition; mantle chemistry; mantle plume; melt inclusion; seamount, article; chemical composition; geochemistry; geography; geology; heat; island (geological); lava; lithosphere; mantle plume; priority journal; rock; thermal structure; United States; volcano, Hawaiian Islands; oceanic regions; Pacific islands; Pacific Ocean; World
Abstract: ▾ The Hawaiian-Emperor volcanic island and seamount chain is usually attributed to a hot mantle plume, located beneath the Pacific lithosphere, that delivers material sourced from deep in the mantle to the surface. The shield volcanoes of the Hawaiian islands are distributed in two curvilinear, parallel trends (termed 'Kea' and 'Loa'), whose rocks are characterized by general geochemical differences. This has led to the proposition that Hawaiian volcanoes sample compositionally distinct, concentrically zoned, regions of the underlying mantle plume. Melt inclusions, or samples of local magma 'frozen' in olivine phenocrysts during crystallization, may record complexities of mantle sources, thereby providing better insight into the chemical structure of plumes. Here we report the discovery of both Kea- and Loa-like major and trace element compositions in olivine-hosted melt inclusions in individual, shield-stage Hawaiian volcanoes-even within single rock samples. We infer from these data that one mantle source component may dominate a single lava flow, but that the two mantle source components are consistently represented to some extent in all lavas, regardless of the specific geographic location of the volcano. We therefore suggest that the Hawaiian mantle plume is unlikely to be compositionally concentrically zoned. Instead, the observed chemical variation is probably controlled by the thermal structure of the plume.
383.
[English]
Using openhole and cased hole resistivity logs to monitor gas hydrate dissociation during a thermal test in the Mallik 5L-38 research well, Mackenzie Delta, Canada
Publisher
Society of Petrophysicists and Well-Log Analysts (SPWLA)
2005
Schlumberger, United States; U.S. Geological Survey, United States382.
[English]
Shear wave anisotropy observed in VSP data at the San Andreas Fault Observatory at Depth
Page 174-177
Publisher
Society of Exploration Geophysicists
2005
Duke University, United States; Schlumberger-Doll Research, United StatesKeywords:▾
Anisotropy; Deformation; Observatories; Plates (structural components); Seismic prospecting; Seismology; Shear flow; Shear waves; Strike-slip faults, Monitoring equipment; San andreas fault observatory at depth projects; Shear-wave anisotropy; Structural interpretation; Subsurface monitoring; Subsurface structures; Tectonic deformations; Vertical seismic profiling, Transform faults
ISBN:
9781604236101
381.
[English]
Drill hole logging with infrared spectroscopy
Volume 29
,
Page 565-568
2005
Geological Sciences, Great Basin Center for Geothermal Research, University of Nevada - Reno, Reno, NV, United States; U. S. Geological Survey, Earthquake Hazards Team, Menlo Park, CA, United States380.
[English]
Drill bit seismic imaging of the San Andreas Fault System at SAFOD
Page 2657-2660
Publisher
Society of Exploration Geophysicists
2005
Duke University, United States; Schlumberger-Doll Research, United States; WesternGeco, United KingdomKeywords:▾
Bits; Boreholes; Drills; Geophysical prospecting; Infill drilling; Observatories; Seismic waves; Strike-slip faults, San Andreas fault; Seismic imaging; Seismic information; Seismic studies; Subsurface source; US Geological Survey; Vertical component; Vertical seismic profiles, Seismology
ISBN:
9781604236101
379.
Topography over the Chicxulub impact crater from Shuttle Radar Topography Mission data
Special Paper of the Geological Society of America,
384141-146
2005
Abstract: ▾ Shuttle Radar Topography Mission (SRTM) data over the Chicxulub impact crater are imaged and compared to previously available topography data. While the two data sets contain different biases related to variations in terrain and vegetation cover, the correspondence of the two sets supports earlier interpretations that the complex structure of the buried crater is expressed in the topography of the northwestern Yucatán Peninsula, México. © 2005 Geological Society of America.
378.
The use of field dependence of AC susceptibility for the interpretation of magnetic mineralogy and magnetic fabrics in the HSDP-2 basalts, Hawaii
Earth and Planetary Science Letters,
238
(1-2)
110 – 129
2005
ISSN: 0012821XKeywords:▾
Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands; North America; oceanic regions; Pacific islands; Pacific Ocean; United States; Western Hemisphere; World; Basalt; Composition effects; Grain size and shape; Magnetic susceptibility; Magnetite; Mineralogy; Oxidation; Field dependence; Magnetic fabrics; Magnetic mineralogy; Titanomagnetite; basalt; magnetic field; magnetic susceptibility; titanomagnetite; Geochemistry
Abstract: ▾ We applied the field dependence parameter χHd (%) = [(k300A/m-k30A/m)/k300A/m] × 100 given by de Wall for the subaerial and submarine basalts drilled by the 3109 m deep HSDP-2 borehole on Hawaii in order to verify the hypothesis that mainly composition controls the field dependence of AC susceptibility in titanomagnetite of natural occurrences. When we used this parameter, our data showed a significant scattering compared to data presented in earlier studies. In addition to composition, the effect of measurement temperature, grain size and anisotropy on the field dependent susceptibility were examined and found to be critical. The impact of grain size is weaker than the other effects. It cannot be totally excluded that the observed effects arise indirectly through an overlap of the other effects for the investigated basalts. The most important factor for the variation of field dependence is the degree of oxidation, causing a modification of the titanomagnetite composition or formation of titanomaghemite, and the mixing of Ti-rich with Ti-poor titanomagnetites, which strongly reduces the χHd parameter. Field dependence is not only related to titanomagnetite composition, especially for intermediate titanomagnetites with TCs between 100 and 300 °C. Temperature dependent susceptibility measurements at different field amplitudes for these intermediate types showed at constant geometry of the k(T) curve great differences in susceptibility, resulting in significant changes of the field dependence parameter over the temperature interval from - 100 to 260 °C. herefore variations of the ambient measurement temperatures are able to influence the field dependence. The second important effect is the degree of particle shape and alignment, which controls the field dependence in different orientations especially for the intermediate titanomagnetite, which is intensively intergrown with elongated hemoilmenite grains. As a consequence, samples with higher degrees of anisotropy exhibit differences of the field dependence parameter if measured parallel to kmax or kmin axis. Therefore, in addition to compositional effects and the temperature dependence, the magnetic fabric has to be considered for the interpretation of field dependent susceptibility measurements. The influence of intrinsic (Ti-content, magnetocrystalline anisotropy), and extrinsic (shape and alignment of grains) factors for the interpretation of the degree of anisotropy has to be kept in mind when interpreting AMS data in terms of strain rates experienced by moving lava during emplacement. © 2005 Elsevier B.V. All rights reserved.
377.
The outline of mallik 2002 gas hydrate production research well program
Nihon Enerugi Gakkaishi/Journal of the Japan Institute of Energy,
84
(2)
88-92
2005
ISSN: 09168753Abstract: ▾ It is estimated that significant amount of methane hydrate resources are deposited offshore Japan and the Research Consortium of Methane Hydrate Resources in Japan (MH21 Research Consortium) was established to undertake the "Japan's Methane Hydrate Exploitation Program" which was prepared by the Ministry of Economy, Trade and Industry and announced in 2001. MH21 Research Consortium planned onshore tests of gas production from gas hydrate reservoir and the Mallik 2002 Gas Hydrate Production Research Well Program was formed in which eight bodies participated from five countries. The test site was located in onshore Mackenzie delta of Northwestern Canada. The swamp feature of the site restricted the whole test operation only in winter when frozen firm ground and transportation road are formed. From December 25th 2001 to March 14th 2002, one gas production test well and two observation wells were drilled. Pressure draw down test using MDT and a hot water circulation test were tried , and the latter test yielded 468m3 dissociated gas from the hydrate reservoir, which was the first success of gas production from naturally deposited gas hydrate reservoir. In December 2003, Mallik International Symposium was held in Chiba, Japan with more than 200 researchers' participation from thirteen countries. The success of the Mallik Program was officially announced for the first time at the Symposium.
376.
The Iceland Deep Drilling Project: A search for deep unconventional geothermal resources
Geothermics,
34
(3)
269 – 285
2005
375.
The ICDP lake Bosumtwi drilling project: A first report
Scientific Drilling,
123 – 27
2005
ISSN: 18168957
Publisher: Copernicus GmbH
Keywords:▾
Coremaking; Lakes; Continental scientific drillings; Core material; Drilling projects; Impact craters; Scientific results; Infill drilling
Abstract: ▾ The 10.5 -km-diameter, 1.07-Ma Bosumtwi impact crater was the subject of a multi-disciplinary and international drilling effort of the International Continental Scientific Drilling Program (ICDP) from July to October 2004. Sixteen different holes were drilled at six locations within the lake, to a maximum depth of 540 m. A total of about 2.2 km of core material was obtained. Despite some technical and logistical challenges, the project has been very successful and it is anticipated that the first scientific results will be available in late 2005. © 2005 Copernicus GmbH.
374.
The 40Ar/39Ar dating of core recovered by the Hawaii Scientific Drilling Project (phase 2), Hilo, Hawaii
Geochemistry, Geophysics, Geosystems,
6
(4)
2005
ISSN: 15252027Abstract: ▾ The Hawaii Scientific Drilling Project, phase 2 (HSDP-2), recovered core from a ∼3.1-km-thick section through the eastern flanks of Mauna Loa and Mauna Kea volcanoes. We report results of 40Ar/39Ar incremental heating by broad-beam infrared laser of 16 basaltic groundmass samples and 1 plagioclase separate, mostly from K-poor tholeiites. The tholeiites generally have mean radiogenic 40Ar enrichments of 1-3%, and some contain excess 40Ar; however, isochron ages of glass-poor samples preserve stratigraphic order in all cases. A 246-m-thick sequence of Mauna Loa tholeiitic lavas yields an isochron age of 122 ± 86 kyr (all errors 2<r) at its base. Beneath the Mauna Loa overlap sequence lie Mauna Kea's postshield and shield sequences. A postshield alkalic lava yields an age of 236 ± 16 kyr, in agreement with an age of 240 ± 14 kyr for a geochemically correlative flow in the nearby HSDP-1 core hole, where more complete dating of the postshield sequence shows it to have accumulated at 0.9 ± 0.4 m/kyr, from about 330 to <200 ka. Mauna Kea's shield consists of subaerial tholeiitic flows to a depth of 1079 m below sea level, then shallow submarine flows, hyaloclastites, pillow lavas, and minor intrusions to core bottom at 3098 m. Most subaerial tholeiitic flows fail to form isochrons; however, a sample at 984 m yields an age of 370 ± 180 kyr, consistent with ages from similar levels in HSDP-1. Submarine tholeiites including shallow marine vitrophyres, clasts from hyaloclastites, and pillow lavas were analyzed; however, only pillow lava cores from 2243, 2614, and 2789 m yield reliable ages of 482 ± 67, 560 ± 150, and 683 ± 82 kyr, respectively. A linear fit to ages for shield samples defines a mean accumulation rate of 8.6 ± 3.1 m/kyr and extrapolates to ∼635 kyr at core bottom. Alternatively, a model relating Mauna Kea's growth to transport across the Hawaiian hot spot that predicts downward accelerating accumulation rates that reach ∼20 m/kyr at core bottom (DePaolo and Stolper, 1996) is also consistent with all reliable ages except the deepest. Copyright 2005 by the American Geophysical Union.
373.
Radiolytic H2 in continental crust: Nuclear power for deep subsurface microbial communities
Geochemistry, Geophysics, Geosystems,
6
(7)
2005
ISSN: 15252027Abstract: ▾ H2 is probably the most important substrate for terrestrial subsurface lithoautotrophic microbial communities. Abiotic H2 generation is an essential component of subsurface ecosystems truly independent of surface photosynthesis. Here we report that H2 concentrations in fracture water collected from deep siliclastic and volcanic rock units in the Witwatersrand Basin, South Africa, ranged up to two molar, a value far greater than observed in shallow aquifers or marine sediments. The high H2 concentrations are consistent with that predicted by radiolytic dissociation of H2O during radioactive decay of U, Th, and K in the host rock and the observed He concentrations. None of the other known H2-generating mechanisms can account for such high H2 abundance either because of the positive free energy imposed by the high H2 concentration or pH or because of the absence of required mineral phases. The radiolytic H 2 is consumed by methanogens and abiotic hydrocarbon synthesis. Our calculations indicate that radiolytic H2 production is a ubiquitous and virtually limitless source of energy for deep crustal chemolithoautotrophic ecosystems. Copyright 2005 by the American Geophysical Union.
372.
Structure and stress state of Hawaiian island basalts penetrated by the Hawaii Scientific Drilling Project deep core hole
Journal of Geophysical Research: Solid Earth,
110
(7)
1 – 8
2005
ISSN: 21699313
Publisher: Blackwell Publishing Ltd
Keywords:▾
Hawaiian Islands; oceanic regions; Pacific islands; Pacific Ocean; World; ocean island basalt; stress field; structural geology; volcanic island
Abstract: ▾ As part of the Hawaii Scientific Drilling Project (HSDP), an exploratory hole was drilled in 1993 to a depth of 1056 meters below sea level (mbsl) and a deeper hole was drilled to 3098 mbsl in 1999. A set of geophysical well logs was obtained in the deeper hole that provides fundamental information regarding the structure and the state of stress that exist within a volcanic shield. The acoustic televiewer generates digital, magnetically oriented images of the borehole wall, and inspection of this log yields a continuous record of fracture orientation with depth and also with age to 540 ka. The data depict a clockwise rotation in fracture strike through the surficial Mauna Loa basalts that settles to a constant heading in the underlying Mauna Kea rocks. This behavior reflects the depositional slope directions of lavas and the locations of volcanic sources relative to the drill site. The deviation log delineates the trajectory of the well bore in three-dimensional space. This path closely follows changes in fracture orientation with depth as the drill bit is generally prodded perpendicular to fracture strike during the drilling process. Stress-induced breakouts observed in the televiewer log identify the orientations ot the maximum and minimum horizontal principal stresses to be north-south and east-west, respectively. This stress state is attributed to the combination of a sharp break in onshore-offshore slope that reduces stress east-west and the emergence of Kilauea that increases stress north-south. Breakouts are extensive and appear over approximately 30% of the open hole. Copyright 2005 by the American Geophysical Union.
371.
Stable isotope record of post-impact fluid activity in the core of the Yaxcopoil-1 borehole, Chicxulub impact structure, Mexico
Special Paper of the Geological Society of America,
384223-238
2005
Abstract: ▾ Carbon, oxygen, and hydrogen isotope results from carbonate and silicate fractions of altered core samples from the Yaxcopoil-1 borehole drilled into the 65 Ma Chicxulub impact crater provide constraints on the physico-chemical parameters of the hydrothermal solutions, and their likely origin. Yaxcopoil-1 impactites were initially permeated with calcite and halite at ambient temperature. This was followed by thermal metamorphism (diopside after igneous augite) and widespread Na-K metasomatism (feldspar after igneous plagioclase), which were overprinted by abundant lower-temperature clay and calcite. Silicate fraction isotopic values have δ 18O SMOW values between 10 and 23% indicating important isotopic exchange between impact melt (∼8%) and Cretaceous limestone (∼26%). Heavier δ 18 O values occur over depth intervals with intense feldspar alteration (813-833 m and 864-872 m). The δD SMOW values (-34 to -54%) are chiefl y infl uenced by smectite abundance and roughly mirror δ 18 O values. Carbonate fraction δ 18 O SMOW values (22-30%) are controlled by calcite contents, and several exceed the limestone signature. Most δ0.13C PDB (-1 to +2%) values also cluster around that of local limestone, but a number are signifi cantly lighter (down to -7%). Isotopic and fluid inclusion results indicate hydrothermal fluid temperatures between 270 and 100 °C, high salinities (∼20%), and minor kerogen contents. These data are compatible with mineralogical constraints, which further support an increase in oxidation state with decreasing temperature. Isotopic data point to a saline CO 2 -bearing fluid mixed with small amounts of reduced carbon, and decarbonation and infi ltration processes. Combined results are most consistent with a basinal oilfi eld saline brine that was driven by impact-induced heat. © 2005 Geological Society of America.
370.
Spinel-bearing spherules condensed from the Chicxulub impact-vapor plume
Geology,
33
(4)
293-296
2005
DOI:10.1130/G21136.1
Abstract: ▾ Formation of the giant Chicxulub crater off Mexico's Yucatan Peninsula coincided with deposition of the global Ir-rich Cretaceous-Tertiary (K-T) stratigraphic boundary layer ca. 65 Ma. The boundary is marked most sharply by abundant spherules containing un-altered grains of magnesioferrite spinel. Here we predict for the first time the sequential condensation of solids and liquids from the plume of vaporized rock expected from oblique K-T impacts. We predict highly oxidizing plumes that condense silicate liquid droplets bearing spinel grains whose compositions closely match those marking the actual boundary. Systematic global variations in spinel composition are consistent with higher condensation temperatures for spinels found at Atlantic and European sites than for those in the Pacific. © 2005 Geological Society of America.