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All ICDP Publications with Abstracts

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119.
Sakai, H.; Nomura, S.; Horii, M.; Kashiwaya, K.; Tanaka, A.; Kawai, T.; Kravchinsky, V.; Peck, J.
3 - Paleomagnetic and rock-magnetic studies on lake baikal sediments -BDP96 borehole at academician ridge-
In Koji Minoura, Editor , Lake Baikal Page 35-52 Publisher Elsevier Science B.V. , Amsterdam 2000 35-52
DOI:https://doi.org/10.1016/B978-044450434-0/50004-4
ISBN:
978-0-444-50434-0
118.
Kashiwaya, K.; Tanaka, A.; Sakai, H.; Kawai, T.
4 - Paleoclimatic signals printed in lake baikal sediments
In Koji Minoura, Editor , Lake Baikal Page 53-70 Publisher Elsevier Science B.V. , Amsterdam 2000 53-70
DOI:https://doi.org/10.1016/B978-044450434-0/50005-6
ISBN:
978-0-444-50434-0
117.
Karabanov, E.B.; Kuzmin, M.I.; Prokopenko, A.A.; Williams, D.F.; Khursevich, G.K.; Bezrukova, E.V.; Kerber, E.V.; N.}, Gvozdkov {A.; F.}, Gelety {V.; D., Weil; M., Schwab
5 - Glaciations of central asia in the late cenozoic according to the sedimentary record from lake baikal
In Koji Minoura, Editor , Lake Baikal Page 71-84 Publisher Elsevier Science B.V. , Amsterdam 2000 71-84
DOI:https://doi.org/10.1016/B978-044450434-0/50006-8
ISBN:
978-0-444-50434-0
116.
Demske, D.; Mohr, B.; Oberhänsli, H.
6 - Palaeoclimatic changes from 3.6 to 2.2 ma b.p. derived from palynological studies on lake baikal sediments
In Koji Minoura, Editor , Lake Baikal Page 85-89 Publisher Elsevier Science B.V. , Amsterdam 2000 85-89
DOI:https://doi.org/10.1016/B978-044450434-0/50007-X
ISBN:
978-0-444-50434-0
115.
Müller, J.; Kasbohm, J.; Oberhänsli, H.; Melles, M.; Hubberten, H.W.
7 - TEM analysis of smectite-illite mixed-layer minerals of core BDP 96 hole 1: Preliminary results
In Koji Minoura, Editor , Lake Baikal Page 90-100 Publisher Elsevier Science B.V. , Amsterdam 2000 90-100
DOI:https://doi.org/10.1016/B978-044450434-0/50008-1
ISBN:
978-0-444-50434-0
114.
Kawamuro, K.; Shichi, K.; Hase, Y.; Iwauchi, A.; Minoura, K.; Oda, T.; Takahara, H.; Sakai, H.; Morita, Y.; Miyoshi, N.; Kuzmin, M.I.
8 - Forest-desert alternation history revealed by the pollen-record in lake baikal over the past 5 million years
In Koji Minoura, Editor , Lake Baikal Page 101-107 Publisher Elsevier Science B.V. , Amsterdam 2000 101-107
DOI:https://doi.org/10.1016/B978-044450434-0/50009-3
ISBN:
978-0-444-50434-0
113.
Takahara, H.; Krivonogov, S.K.; Bezrukova, E.V.; Miyoshi, N.; Morita, Y.; Nakamura, T.; Hase, Y.; Shinomiya, Y; Kawamuro, K.
9 - Vegetation history of the southeastern and eastern coasts of Lake Baikal from bog sediments since the last interstade
In Koji Minoura, Editor , Lake Baikal Page 108-118 Publisher Elsevier Science B.V. , Amsterdam 2000 108-118
DOI:https://doi.org/10.1016/B978-044450434-0/50010-X
ISBN:
978-0-444-50434-0
112.
Eckert, C.; Veinberg, E.V.; Kienel, U.; Oberhänsli, H.
12 - A new preparation method for qualitative and quantitative analysis of fossil sponge spicules by light microscopy
In Koji Minoura, Editor , Lake Baikal Page 136-145 Publisher Elsevier Science B.V. , Amsterdam 2000 136-145
DOI:https://doi.org/10.1016/B978-044450434-0/50013-5
ISBN:
978-0-444-50434-0
111.
Khursevich, G.K.; Karabanov, E.B.; Williams, D.F.; Kuzmin, M.I.; Prokopenko, A.A.
13 - Evolution of freshwater centric diatoms within the Baikal rift zone during the late Cenozoic
In Koji Minoura, Editor , Lake Baikal Page 146-154 Publisher Elsevier Science B.V. , Amsterdam 2000 146-154
DOI:https://doi.org/10.1016/B978-044450434-0/50014-7
ISBN:
978-0-444-50434-0
110.
Mats, V.D.; Fujii, S.; Mashiko, K.; Osipov, E.Yu.; Yefrimova, I.M.; Klimansky, A.V.
2 - Changes in lake baikal water levels and runoff direction in the quaternary period
In Koji Minoura, Editor , Lake Baikal Page 15-34 Publisher Elsevier Science B.V. , Amsterdam 2000 15-34
DOI:https://doi.org/10.1016/B978-044450434-0/50003-2
ISBN:
978-0-444-50434-0
109.
Takamatsu, N.; Matsumoto, I.G.; Kato, N.; Kawai, T.
11 - Paleoenvironmental changes in the Eurasian continent interior inferred from chemical elements in sediment cores (BDP96/1, BDP96/2) from Lake Baikal
In Koji Minoura, Editor , Lake Baikal Page 127-135 Publisher Elsevier Science B.V. , Amsterdam 2000 127-135
DOI:https://doi.org/10.1016/B978-044450434-0/50012-3
ISBN:
978-0-444-50434-0
108.
Mapping the Hawaiian plume conduit with converted seismic waves
Li, X.; Kind, R.; Priestloy, K.; Sobolev, S.V.; Tilmann, F.; Yuar, X.; Weber, M.
Nature, 405 (6789) 938-941 2000
ISSN: 00280836
DOI:10.1038/35016054
Keywords:▾ crustal structure; hot spot; mantle plume; seismic velocity, air temperature; article; atmosphere; geography; plume; priority journal; sea; shear rate; United States; volcano, Pacific Ocean
Abstract: ▾ The volcanic edifice of the Hawaiian islands and seamounts, as well as the surrounding area of shallow sea floor known as the Hawaiian swell, are believed to result from the passage of the oceanic lithosphere over a mantle hotspot. Although geochemical and gravity observations indicate the existence of a mantle thermal plume beneath Hawaii, no direct seismic evidence for such a plume in the upper mantle has yet been found. Here we present an analysis of compressional-to-shear (P-to-S) converted seismic phases, recorded on seismograph stations on the Hawaiian islands, that indicate a zone of very low shear-wave velocity (< 4 km s-1) starting at 130-140 km depth beneath the central part of the island of Hawaii and extending deeper into the upper mantle. We also find that the upper-mantle transition zone (410-660 km depth) appears to be thinned by up to 40-50 km to the south-southwest of the island of Hawaii. We interpret these observations as localized effects of the Hawaiian plume conduit in the asthenosphere and mantle transition zone with excess temperature of ~300°C. Large variations in the transition-zone thickness suggest a lower-mantle origin of the Hawaiian plume similar to the Iceland plume, but our results indicate a 100°C higher temperature for the Hawaiian plume.
107.
Matsumoto, G.I.; Kosaku, S.; Takamatsu, N.; Akagi, T.; Kawai, T.; Ambe, Y.
10 - Estimation of paleoenvironmental changes in the Eurasian continental interior during the past 5 million years inferred from organic components in the BDP96 1
In Koji Minoura, Editor , Lake Baikal Page 119-126 Publisher Elsevier Science B.V. , Amsterdam 2000 119-126
DOI:https://doi.org/10.1016/B978-044450434-0/50011-1
ISBN:
978-0-444-50434-0
106.
A new estimate of the Holocene lowstand level of Lake Titicaca, central Andes, and implications for tropical palaeohydrology
Cross, Scott L.; Baker, Paul A.; Seltzer, Geoffrey O.; Fritz, Sherilyn C.; Dunbar, Robert B.
Holocene, 10 (1) 21 – 32 2000
DOI:10.1191/095968300671452546
Keywords:▾ Bolivia; Lake Titicaca; Holocene; lake level; lowstand; paleohydrology
Abstract: ▾ New evidence from piston cores and high-resolution seismic reflection data shows that water levels in Lake Titicaca were as much as 100 m below the present level during the early to mid-Holocene (between >6 and 3.8 14C kyr BP). Climatological and modelling studies indicate that Lake Titicaca rainfall depends on convective activity in upwind Amazonia; the lake-level data therefore suggest a drier Amazon Basin during this time. This view is bolstered by an excellent match between the Titicaca lake-level curve and decreased methane concentrations in Greenland ice, previously ascribed to drying of low-latitude wetlands (Blunier et al., 1995). The postglacial history of Lake Titicaca fits a global pattern of lake-level change in the tropics, characterized by opposite phasing between the Southern and Northern Hemispheres. This pattern is most likely the result of orbital controls over the intensity of summer insolation.
105.
A new record of Holocene climate change from the bottom sediments of Lake Baikal
Karabanov, E.B.; Prokopenko, A.A.; Williams, D.F.; Khursevich, G.K.
Palaeogeography, Palaeoclimatology, Palaeoecology, 156 (3-4) 211 – 224 2000
DOI:10.1016/S0031-0182(99)00141-8
104.
Clay minerals in bottom sediments of Lake Baikal as indicators of climate change
Kuz'min, M.I.; Solotchina, E.P.; Vasilevskii, A.N.; Stolpovskaya, V.N.; Karabanov, E.B.; Geletii, V.F.; Bychinskii, V.A.; Anoshin, G.N.; Shul'zhenko, S.G.
Geologiya i Geofizika, 41 (10) 1347 – 1359 2000
ISSN: 00167886
Abstract: ▾ The mineral assemblage of Pliocene - Pleistocene bottom sediments of Lake Baikal, exposed by the deep-sea BDP-96-2 (Baikal Drilling Project) has been studied by the methods of XRD and IR spectroscopy. Complex XRD patterns of clay minerals have been modeled using an advanced algorithm based on calculation of interference function from one-dimensional disordered crystals of finite thickness. The modeling implies fitting of theoretical to observed patterns and optimization procedure by methods of nonlinear programming. It has been shown that major clay minerals in the sediments that formed for the past 2.5 Ma during cold stages are illite-illite-smectites with predominantly illite layers, and chlorite; the principal clay minerals in the sediments that formed during warm periods are smectite, illite-smectites with high contents of smectite layers, and chlorite-smectites. These data allow unravelling the climate history of Lake Baikal from biogenic silica record.
103.
Climate-induced fluctuations of 10Be concentration in Lake Baikal sediments
Horiuchi, K.; Kobayashi, K.; Oda, T.; Nakamura, T.; Fujimura, C.; Matsuzaki, H.; Shibata, Y.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 172 (1-4) 562 – 567 2000
ISSN: 0168583X Publisher: Elsevier
DOI:10.1016/S0168-583X(00)00100-2
Keywords:▾ Beryllium; Climate change; Erosion; Glacial geology; Lakes; Oxygen; Radioisotopes; Sediments; Stratigraphy; Watersheds; Weathering; Accelerated mass spectrometry; Marine oxygen isotope stages; Marine sediments; Mass spectrometry
Abstract: ▾ Sedimentary 10Be records covering the last 150 kyr were obtained from three cores collected at the Academician Ridge (BDP-96/hole2 core and VER96/st.3 core) and at the Buguldeika Saddle (BDP-93/hole2 core) in Lake Baikal. The 10Be concentrations of the three cores varied between 0.5 × 109 and 1.5 × 109 atoms/g, and coincidently dropped at the stratigraphic intervals of marine oxygen isotope stages (MIS) 2, 4, 5d and 6. The depositional fluxes of 10Be, on the other hand, generally rose in those stages having an increase in the dry bulk densities and sediment accumulation rates. These results are consistent with previous work (Horiuchi et al., 1999), suggesting that the dilution effects of low-10Beconcentration particles principally controlled the fluctuations of the 10Be concentrations of Lake Baikal sediments. Low-10Be-concentration particles have been intensively produced by mechanical weathering and physical erosion under the cold and dry climatic conditions during the peak glaciation period, and have been directly brought from the source areas into the lake as a result of the thin vegetative cover of the watershed. © 2000 Elsevier Science B.V. All rights reserved.
102.
Comparison of biogenic silica, Br and Nd distributions in the sediments of Lake Baikal as proxies of changing paleoclimates of the last 480 kyr
Phedorin, M.A.; Goldberg, E.L.; Grachev, M.A.; Levina, O.L.; Khlystov, O.M.; Dolbnya, I.P.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 448 (1) 400 – 406 2000
ISSN: 01689002 Publisher: Elsevier Science B.V.
DOI:10.1016/S0168-9002(99)00726-3
Keywords:▾ Bromine; Geochemistry; Lakes; Neodymium; Organic compounds; Sediments; Silica; Spectrum analysis; Synchrotron radiation; Biogenic silica; Lake Baikal; Paleoclimate indicators; Sedimentary geochemistry; X ray fluorescence analysis; X ray analysis
Abstract: ▾ The paper presents a comparison of the profiles of biogenic silica (BiSi), Br and Nd in the first 20 m of the BDP-96-2 core of sediments of Lake Baikal obtained on top of the underwater Akademichesky Ridge. The concentrations of the two elements mentioned were measured by X-ray fluorescent analysis with synchrotron radiation (SR-XFA) at 10 cm intervals. Br correlates positively, and Nd negatively with BiSi. Spectral analysis of the profiles revealed the 100, 41, 23 and 19 kyr major external forcing periods. We studied the elemental composition of extant diatom algae of Lake Baikal in order to find out whether any elements are bound by them specifically. SR-XFA revealed, among others that Br is accumulated by extant diatom algae of Lake Baikal, presumably due to incorporation into their organic matter. Br can be regarded as a new proxy of the paleo-productivity of Lake Baikal. The paper also considers arguments suggesting that the first 2 m of sediment are missing in the BDP-96-2 core.
101.
Comparison of elastic velocity models for gas-hydrate-bearing sediments
Lee, M.W.; Collett, T.S.
Geophysical Monograph Series, 124179-187 2000
ISSN: 00658448 Publisher: Blackwell Publishing Ltd
DOI:10.1029/GM124p0179
ISBN:
9781118668412; 9780875909820
Abstract: ▾ One of the distinct physical properties of gas-hydrate-bearing sediments is elevated seismic velocities. A number of velocity models and equations have been presented to describe the effect of gas hydrate on the seismic velocities; e.g., pore-filling model, cementation model, effective medium theory, a weighted equation, and time-average equation. The data set from Mallik 2L-38 gas hydrate research well drilled in northern Canada provided us a unique opportunity to test the velocity models for gas-hydrate-bearing sediments. Velocities predicted from an effective medium theory and those from a weighted equation are compared with observed well log velocities. In the case where there is no gas hydrate in the pore space, P-wave velocities predicted from the effective medium theory are lower than those from the weighted equation when porosity is less than about 30% and higher when porosity is higher than about 30%. For S-waves, effective medium theory predicts generally higher velocities than those from the weighted equation. Both theories predict similar increases in P- and S-wave velocities when gas hydrate occupies the pore space. Even though gas hydrate concentration in the pore space is not known accurately, analyses using both P- and S-wave velocities and their ratios enable us to test the validity of velocity models. Considering only P-wave velocities, there is not much difference between the effective medium and weighted equation. However, considering both P- and S-wave velocities and their ratios, the weighted equation is preferred to the effective medium theory in predicting elastic wave velocities for gas-hydrate-bearing sediments at the Mallik 2L-38 well. © 2001 by the American Geophysical Union.
100.
Fluid history of UHP metamorphism in Dabie Shan, China: A fluid inclusion and oxygen isotope study on the coesite-bearing eclogite from Bixiling
Xiao, Yilin; Hoefs, Jochen; Van Den Kerkhof, Alfons M.; Fiebig, Jens; Zheng, Yongfei
Contributions to Mineralogy and Petrology, 139 (1) 1 – 16 2000
ISSN: 00107999 Publisher: Springer Verlag
DOI:10.1007/s004100050570
Keywords:▾ Bixiling; China; Dabie Shan; coesite; eclogite; fluid composition; fluid inclusion; isotopic composition; oxygen; ultrahigh pressure metamorphism
Abstract: ▾ The coesite-bearing eclogites and associated ultramafic rocks of Bixiling form the largest metamorphic complex in the Dabie-Sulu ultrahigh-pressure (UHP) metamorphic belt. They mainly consist of 'fresh' eclogite, kyanite-rich eclogite, retrograded eclogite and garnet peridotite. Fluid inclusion and oxygen isotope studies have been carried out on the different types of eclogite and peridotite in order to identify the role of fluids during the metamorphic evolution culminating in UHP metamorphism. Five types of fluid inclusions were distinguished based on textural criteria and fluid compositions: (1) primary Ca-rich brines in quartz blebs in kyanite; (2) primary NaCl-dominated high-salinity inclusions in omphacite and kyanite; (3) primary NaCl-dominated medium- to high-salinity inclusions in matrix quartz; (4) carbonic inclusions in omphacite and matrix quartz; (5) secondary low-salinity aqueous (or pure water) inclusions in matrix quartz. The Ca-rich fluid inclusions in quartz blebs in kyanite represent the earliest recognizable fluids (prograde metamorphism) as they largely escaped late re-equilibration. Fluid inclusions in omphacite and kyanite may have been trapped during peak metamorphic conditions, whereas low-salinity aqueous inclusions in matrix quartz were trapped during the latest stage of uplift. UV-laser oxygen isotope measurements show that garnet and clinopyroxene from the 'fresh' eclogite, kyanite-rich eclogite and garnet peridotite have narrow δ18O values ranging from 3.0 to 3.9‰. In contrast, garnet and omphacite in retrograded eclogite have δ18O values of -1.8 to -1.2 and of -1.1 to -0.6‰, respectively. The difference in oxygen isotope composition is interpreted to result from partial oxygen isotope exchange between the UHP complex and retrograde fluids during late exhumation. Fluids derived from the surrounding gneiss were probably responsible for the low-salinity solutions found in secondary fluid inclusions and the lowering of the δ18O values of the retrograded eclogite.
99.
High precision lead isotope systematics of lavas from the Hawaiian Scientific Drilling Project
Abouchami, W.; Galer, S.J.G.; Hofmann, A.W.
Chemical Geology, 169 (1-2) 187 – 209 2000
ISSN: 00092541
DOI:10.1016/S0009-2541(00)00328-4
Keywords:▾ United States; geochemistry; hot spot; lava; lead isotope
Abstract: ▾ We report Pb isotopic compositions for 35 samples of the volcanoes Mauna Loa and Mauna Kea from the Hawaiian Scientific Drilling Project (HSDP-1) core at Hilo. These data were obtained with an external precision of ~ 100 ppm (2σ(ext.)) on the ratios 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb by using a Pb triple spike to correct for instrumental mass fractionation. The Pb isotopic compositions in the lower section (1200 to 280 m) of the core sample 200 to 400 ka-old Mauna Kea lavas, and display two well-defined linear arrays in 207Pb/204Pb-206Pb/204Pb and 208Pb/204Pb-206Pb/204Pb isotope spaces. There is a suggestion that Mauna Loa (0 to 280 m depth) also displays such linear array(s). However, analysis of the Mauna Loa samples is complicated by residual contamination and/or sample heterogeneity. While these latter data exhibit a satisfactory array in 208Pb/204Pb vs. 206Pb/204Pb, there still remains scatter in 207Pb/204Pb-206Pb/204Pb space, making it difficult to assess the true Pb isotope systematics of Mauna Loa. The presence of two linear Pb isotopic arrays in Mauna Kea can be interpreted as either reflecting two parallel isochrons or in terms of binary mixing. If interpreted as isochrons, the 207Pb/204Pb-206Pb/204Pb systematics correspond to an age of ~ 1.9 Ga. Comparison of measured Th/U ratios in the lavas and those inferred from Pb isotope systematics strongly suggest that the Pb isotopic arrays reflect binary mixing, and this bears directly on the question of how many distinct components are present in the Hawaiian plume. Most of the new Mauna Kea data lie well outside the mixing-component triangle defined in the literature by the 'Kea', 'Loihi', and 'Koolau' components. On the basis of the relationships between Pb isotope ratios in 3D and a principal component analysis of the Mauna Kea Pb isotope dataset, we show here that a three-component mixing model can in principle explain both mixing lines. However, such an explanation requires a highly specific set of mixing conditions in order to produce parallel arrays in Pb isotope space (2D and 3D). Therefore, our preferred interpretation is that the two arrays reflect binary mixing, with four discrete source components involved in the generation of the Kea lavas. Comparison of the Pb isotope characteristics of these lavas with those of East Pacific Rise (EPR) MORB glasses further suggests that EPR-type Pacific lithosphere does not contribute to the source of Kea lavas. The position of samples along the mixing lines does not correlate with stratigraphic height in the core, and therefore the age of the lavas. Rather, it appears as though the relative proportions of the endmembers are controlled by the spatial configuration of these endmembers, and by melting and transport processes in the source itself. The stratigraphic fluctuations of Pb and Sr isotopes contrast with the monotonic decrease of ε(Nd) and ε(Hf) values as a function of age. This may in part be explained by differences in analytical precision of isotope measurements relative to the total range of values observed. This analytical resolution is far higher for Pb than for the other radiogenic isotopes. Alternatively, the observed fluctuation may be caused by the mobility of lead (as well as Rb and/or Sr) during the ancient differentiation process that created the differences in parent-daughter ratios. (C) 2000 Elsevier Science B.V. All rights reserved.
98.
High-Si phengite, mineral chemistry and P-T evolution of ultra-high-pressure eclogites and calc-silicates from the Dabie Shan, eastern China
Schmid, Robert; Franz, Leander; Oberhnsli, Roland; Dong, Shuwen
Geological Journal, 35 (3-4) 185 – 207 2000
ISSN: 00721050 Publisher: John Wiley and Sons Ltd
DOI:10.1002/gj.863
Keywords:▾ China; Dabie Shan; eclogite; metamorphism; P-T conditions; ultrahigh pressure metamorphism
Abstract: ▾ A suite of coesite-eclogites and associated calc-silicate rocks from the ultra-high-pressure (UHP) belt in the Dabie Shan (eastern China) was investigated petrologically. Field relations and the presence of UHP minerals such as coesite, omphacite and high-Si phengite in the eclogites and the enclosing calc-silicates testify to a common metamorphic evolution for these two lithologies. Except for one sample, all bear phengite with unusually high silica contents (Si up to 3.7 per formula unit). Phengite occupies various textural positions indicating that different metamorphic stages are reflected by these white micas, which correlate with distinct mineral zonation patterns. Using the latest thermobarometric calibrations for eclogite-facies rocks, maximum pressure-temperature (P-T) conditions of 40-48 kbar at < 750°C were estimated for the peak-metamorphic mineral assemblages. These P-T conditions were calculated for both eclogitic garnet porphyroblasts with diffusion-controlled zoning as well as garnet porphyroblasts with prograde growth zonation patterns. Most samples were affected by a strong retrograde overprint mainly under eclogite- and amphibolite-facies conditions. Thermobarometry using mineral sets from different textural positions reveals cooling and decompression of the UHP rocks down to < 20 kbar at < 600°C for the bulk of the samples. Decompression and heating indicated by a few samples is interpreted to result from mineral chemical disequilibrium or late thermal influence. These new data show that subduction of continental crust in the Dabie Shan was deeper than previously thought, and also that some cooling and decompression took place at upper-mantle depths. Copyright © 2000 John Wiley and Sons, Ltd.
97.
JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well, Mackenzie Delta, N.W.T.: overview of field operations
Ohara, T.; Dallimore, S.R.; Fercho, E.
SPE Proceedings - Gas Technology Symposium 733-742 2000
DOI:10.2523/59795-ms
Keywords:▾ Additives; Gas hydrates; Heat exchangers; Mud logging; Natural gas well drilling; Oil field development; Organic polymers; Petroleum industry; Petroleum prospecting; Potassium compounds; Sediments; Societies and institutions, Chemical mud additive; Coring; Coring gas hydrate bearing strata; Polymer drilling mud; Potassium chloride drilling mud, Natural gas fields
ISBN:
9781555633493
Abstract: ▾ The Mallik 2L-38 well was drilled in February and March, 1998 to a depth of 1150m at a site located in the Mackenzie Delta, N. W. T., Canada. Undertaken as a collaborative agreement between the Japan National Oil Corporation and the Geological Survey of Canada, the well was conducted as a research and development project with engineering goals to evaluate various technologies for drilling and coring gas-hydrate-bearing strata. The Mallik site was chosen as it had favorable logistics and was though to contain a thick interval of gas hydrates between 897 and 1110 m depth. Drilling operation included a surface hole (with 8 coring runs) to 687m for installation of a 340mm surface casing, and a main hole (with 16 coring runs) to the target depth of 1150m. The drilling system utilized a KCl/polymer drilling mud that was cooled to 2°C using a plate type heat exchanger. Drilltreat, a chemical mud additive was used in the main hole to stabilize the hydrate within drill cuttings and formation sediments. Drilling operations were conducted without any serious hole problems, accidents, or mishaps. However, delays were caused by adverse weather and mechanical problems, causing adjustments in the overall program. Coring in the main hole was particularly successful allowing evaluation of four different core barrels. Gas-hydrate-bearing core was collected in a variety of sediments between 886 and 952m. The excellent condition of the core samples, controlled gas hydrate dissociation within the mud column, and near-gauge hole, confirmed that the combination of chilled mud with Drilltreat performed extremity well.
96.
Dissociation of natural gas hydrates observed by X-ray CT scanner
Mikami, J.; Masuda, Y.; Uchida, T.; Satoh, T.; Takeda, H.
Annals of the New York Academy of Sciences, 9121011-1020 2000
ISSN: 00778923 Publisher: New York Academy of Sciences
DOI:10.1111/j.1749-6632.2000.tb06856.x
Keywords:▾ methane; natural gas, computer assisted tomography; conference paper; dissociation; gas; gas flow; pressure; sand; temperature; X ray analysis
Abstract: ▾ Core samples containing pore-spare gas hydrate within granular sands were collected from 913.76 m of the research well named JAPEX/JNOC/GSC Mallik 2L-38. X-ray CT images of the core were acquired while warming from -18 to 4°C, and subsequently during stepped decreases of 0.1 MPa in the chamber pressure below the methane hydrate equilibrium pressure. Discharged gas flows and sample temperatures were monitored continuously. Changes in CT values indicated that gas hydrate dissociated simultaneously both on the exposed surfaces and within the pore spaces of the sample in response to pressure changes. This suggested that pressure reductions were effectively transmitted through the sample most likely because the samples contained some amount of fluids. The result of gas flow measurements indicated that a larger pressure drawdown caused a higher dissociation rate.
95.
Multi-wavelength synchrotron radiation XRF determination of U and Th in sedimentary cores from Lake Baikal
Phedorin, Michael A.; Goldberg, Evgeny L.; Bobrov, Vladislav A.; Khlystov, Oleg M.; Grachev, Michael A.
Geostandards Newsletter, 24 (2) 217 – 226 2000
ISSN: 01505505
DOI:10.1111/j.1751-908X.2000.tb00773.x
Abstract: ▾ A new technique for the determination of uranium and thorium in lacustrine sediments is based on non-destructive synchrotron radiation X-ray fluorescence analysis (SR-XRF) of sediment samples using monochromatic beams of different energies as excitation sources, with the recording and subsequent iterative processing of the X-ray fluorescence spectra. The technique has a multielement capability and enables fast, simultaneous analysis of a few tens of elements. The proposed SR-XRF technique was tested against INAA and ICP-MS methods and showed a number of advantages with a generally good correlation of results by the three methods. Uranium and Th profiles have been measured at a time resolution of 2 kyr in a drill core (BDP-96) from Lake Baikal bottom sediments deposited between 780 and 40 kyr BP. During this time span, peaks in the U and U/Th concentration marked "warm" climates. Oscillations of U and U/Th in Baikal bottom sediments during the Brunhes chron reflect climate-induced global change in the volume of polar ice, controlled by long-term cyclicity of the Earth's orbital parameters. The response of these "warm" periods is similar to that observed earlier in shorter cores that span the two last interglacials (220-0 kyr BP).