Lithology, mineralogy and geochemistry of ODP Hole 118-735B and 176-735B respectively

Ocean Drilling Program (ODP) Hole 735B, located on Atlantis Bank on the Southwest Indian Ridge, penetrated 1508 meters below seafloor with an average recovery of 87%, providing a nearly continuous sample of a significant part of oceanic Layer 3. Based on variations in texture and mineralogy, 12 major lithologic units are recognized in the section, ranging from 39.5 to 354 m thick. The principal lithologies include troctolite, troctolitic gabbro, olivine gabbro and microgabbro, gabbro, gabbronorite and Fe-Ti oxide gabbro, gabbronorite, and microgabbro. Highly deformed mylonites, cataclasites, and amphibole gneisses are locally present, as are small quantities of pyroxenite, anorthositic gabbro, and trondhjemite. Downhole variations in mineral composition, particularly for olivine and clinopyroxene, show a number of cyclic variations. Plagioclase compositions show the widest variations and correspond to different degrees of deformation and alteration as well as primary processes. Downhole chemical variations correspond reasonably well with variations in mineral compositions. Iron and titanium mainly reflect the presence of Fe-Ti oxide gabbros but show some cyclical variations in the lower part of the core where oxide gabbros are sparse. CaO is highly variable but shows a small but consistent increase downhole. MgO is more uniform than CaO and shows a very small downward increase. Sulfur and CO2 contents are generally low, but S shows significant enrichment in lithologic Unit IV, which consists of Fe-Ti oxide gabbro, reflecting the presence of sulfide minerals in the sequence. The lithologic, mineralogical, and geochemical data provided here will allow detailed comparisons with ophiolite sections as well as sections of in situ ocean crust drilled in the future.

(Table T1) Mineralogy and geochemistry of ODP Hole 192-1183A and Hole 192-1186A sediments, Ontong Java Plateau

Boron, Ca, Na, and Gd concentrations and H intensity in sediments obtained during Ocean Drilling Program Leg 192 were determined by prompt gamma neutron activation analysis. The results show strong positive correlation between B content and H intensity in carbonate samples; chalk samples have higher B contents than limestone samples. Average B content is 9.1 ppm for the chalk and 5.2 ppm for the limestone. When chert blocks or clay minerals are present in the carbonate samples, B content increases (up to 91 ppm).

Clay mineralogy and shear strength of subglacial and glaciomarine sediments in the southern Bellingshausen Sea

The Belgica Trough and the adjacent Belgica Trough Mouth Fan in the southern Bellingshausen Sea (Pacific sector of the Southern Ocean) mark the location of a major outlet for the West Antarctic Ice Sheet during the Late Quaternary. The drainage basin of an ice stream that advanced through Belgica Trough across the shelf during the last glacial period comprised an area exceeding 200,000 km**2 in the West Antarctic hinterland. Previous studies, mainly based on marine-geophysical data from the continental shelf and slope, focused on the bathymetry and seafloor bedforms, and the reconstruction of associated depositional processes and ice- drainage patterns. In contrast, there was only sparse information from seabed sediments recovered by coring. In this paper, we present lithological and clay mineralogical data of 21 sediment cores collected from the shelf and slope of the southern Bellingshausen Sea. Most cores recovered three lithological units, which can be attributed to facies types deposited under glacial, transitional and seasonally open-marine conditions. The clay mineral assemblages document coinciding changes in provenance. The relationship between the clay mineral assemblages in the subglacial and proglacial sediments on the shelf and the glacial diamictons on the slope confirms that a grounded ice stream advanced through Belgica Trough to the shelf break during the past, thereby depositing detritus eroded in the West Antarctic hinterland as soft till on the shelf and as glaciogenic debris flows on the slope. The thinness of the transitional and seasonally open-marine sediments in the cores suggests that this ice advance occurred during the last glacial period. Clay mineralogical, acoustic sub-bottom and seismic data furthermore demonstrate that the palaeo-ice stream probably reworked old sedimentary strata, including older tills, on the shelf and incorporated this debris into its till bed. The geographical heterogeneity of the clay mineral assemblages in the sub- and proglacial diamictons and gravelly deposits indicates that they were eroded from underlying sedimentary strata of different ages. These strata may have been deposited during either different phases of the last glacial period or different glacial and interglacial periods. Additionally, the clay mineralogical heterogeneity of the soft tills recovered on the shelf suggests that the drainage area of the palaeo-ice stream flowing through Belgica Trough changed through time.

Beryllium-10, mineralogy and grain size distribution of DSDP Hole 68-502B (Table 1)

We present a high-resolution 10Be profile from deep sea sediments (sampled from Hole 502B in the Caribbean sea) that strongly resembles the 10Be record in ice core profiles, particularly the Vostok core from Antarctica. This high-resolution profile revealed occurrences of enhanced 10Be concentrations at about 23-24, 37-39 and 60-65 ka. The excellent match between these peaks appearing in a georeservoir profile other than in polar ice, strengthens the implications that can be inferred from 10Be and provide global markers for chronological correlation of climatic events. The position at low latitude of the studied sediment section is, unlike the case with the high latitude polar regions, excellent for exposing causes of modulation in 10Be production. We interpret the source of the pattern and enhancements, particularly the 37-39 ka peak, of 10Be to be global and do not strictly relate to climatic conditions and/or production rates specific to the polar regions.

Life of Benjamin Silliman, M.D., LL.D., late professor of chemistry, mineralogy, and geology in Yale college. Chiefly from his manuscript reminiscences, diaries, and correspondence.

Mode of access: Internet.

Narrative of discovery and adventure in Africa, from the earliest ages to the present time: with illustrations of the geology, mineralogy and zoology.

Added t.-p., illus.

Narrative of discovery and adventure in Africa : from the earliest ages to the present time with illustrations of the geology, mineralogy and zoology /

Added t.-p., illus.

Narrative of discovery and adventure in Africa : from the earliest ages to the present time : with illustrations of the geology, mineralogy and zoology /

Includes bibliographical references.

The Mineralogy and Strength Characteristics of Selected Glaciolacustrine Clays in the Puget Sound Region

The combination of rainy climate, glaciolacustrine clays, and steep topography of the Puget Lowland creates slope stability issues for the regional population. Several glaciolacustrine deposits of laminated silt and clay of different ages contribute to the likelihood of slope failure. The glaciolacustrine deposits are generally wet, range in thickness from absent to >30m, and consist of laminated silt and clay with sand interbeds at the tops and bottoms, sandy laminae throughout the deposits, occasional dropstones and shear zones. The glaciolacustrine deposits destabilize slopes by 1) impeding groundwater flow percolating through overlying glacial outwash sediments, 2) having sandy laminae that lower strength by increasing pore pressure during wet seasons, and 3) increasing the potential for block-style failure because of secondary groundwater pathways such as laminae and vertical fractures. Eight clay samples from six known landslide deposits were analyzed in this study for their mineralogy, clay fraction and strength characteristics. The mineralogy was determined using X-ray Diffractometry (XRD) which revealed an identical mineralogic suite among all eight samples consisting of chlorite, illite and smectite. Nonclay minerals appearing in the X-ray diffractogram include amphibole and plagioclase after removal of abundant quartz grains. Hydrometer tests yielded clay-size fraction percentages of the samples ranging from 10% to 90%, and ring shear tests showed that the angle of residual shear resistance (phi_r) ranged from 11° to 31°. Atterberg limits of the samples were found to have liquid limits ranging from 33 to 83, with plastic limits ranging from 25 to 35 and plasticity indices ranging from 6 to 48. The results of the hydrometer and residual shear strength tests suggest that phi_r varies inversely with the clay-size fraction, but that this relationship was not consistent among all eight samples. The nature of the XRD analysis only revealed the identity of the clay minerals present in the samples, and provided no quantitative information. Thus, the extent to which the mineralogy influenced the strength variability among the samples cannot be determined given that the mineral assemblages are identical. Additional samples from different locations within each deposit along with quantitative compositional analyses would be necessary to properly account for the observed strength variability.

Morphology and crystallography of Mg24Y5 precipitate in Mg-Y alloy

Orientation relationships between Mg24Y5 precipitates and matrix in a Mg-Y alloy were accurately determined using Kikuchi line diffraction. The Burgers relationship with habit planes of {10 (1) over bar0}(H) and {31 (4) over bar0}(H) were observed for all precipitates. Compared with the Mg17Al12 precipitate in AZ91, the precipitation hardening effect in this alloy was significantly increased. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.

Investigation of a binding model for anti-cancer cyclohexadienones by computational chemistry and crystallography

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Mineralogy and petrology of Black Sea Basin sediments

The origin and modes of transportation and deposition of inorganic sedimentary material of the Black Sea were studied in approximately 60 piston, gravity, and Kasten cores. The investigation showed that the sediment derived from the north and northwest (especially from the Danube) has a low calcite-dolomite ratio and a high quartz-feldspar ratio. Rock fragments are generally not abundant; garnet is the principal heavy mineral and illite is the predominant clay mineral. This sedimentary material differs markedly from that carried by Anatolian rivers, which is characterized by a high calcite-dolomite ratio and a low quartz-feldspar ratio. Rock fragments are abundant; pyroxene is the principal heavy mineral and montmorillonite is the predominant clay mineral. In generel, the clay fraction is large in all sediments (27.6-86.9 percent), and the lateral distributian indicates an increase in clay consent from the coasts toward two centers in the western and eastern Black Sea basin. Illite is the most common clay mineral in the Black Sea sediments. The lateral changes in composition of the clay mineral can easily be traced to the petrologic character of northern (rich in illite) and southern (rich in montmorillonite) source areas. In almost all cores, a rhythmic change of the montmorillonite-illite ratio with depth was observed. These changes may be related to the changing influence of the two provinces during the Holocene and late Pleistocene. Higher montmorillonite content seems to indicate climctic changes, probably stages of glaciation end permafrost in the northern area, at which time the illite supply was diminished to a large extent. The composition of the sand fraction is relatad to the different petrologic and morphologic characteristics of two major source provimces: (1) a northern province (rich in quartz, feldspars, and garnet) characterized by a low elevation, comprising the Danube basin area and the rivers draining the Russian platform; and (2) a southern province (rich in pyroxene and volcanic and metamorphic rocks) in the mountainous region of Anatolia and the Caucasus, characterized by small but extremely erosive rivers. The textural properties (graded bedding) of the deep-sea send layers clearly suggest deposition from turbidity currents. The carbonate content of the contemporary sediments ranges from 5 to 65 percent. It increases from the coast to a maximum in two centers in the western and eastern basin. This pattern reflects the distribution of the <2-µm fraction. The contemporary mud sedimentation is governed by two important factors: (1) the deposition of terrigenous allochthonous material of low carbonate content originating from the surrounding hinterland (northern and southern source areas), and (2) the autochthonous production of large quantities of biogenic calcite by coccolithophores during the last period of about 3,000-4,000 years.