ALBERT

Description: Accumulation rates of Mg, Al, Si, Mn, Fe, Ni, Cu, Zn, opal, and calcium carbonate have been calculated from their concentrations in samples from equatorial Deep Sea Drilling Project sites. Maps of element accumulation rates and of Q-mode factors derived from raw data indicate that the flux of trace metals to equatorial Pacific sediments has varied markedly through time and space in response to changes in the relative and absolute influence of several depositional influences: biogenic, detrital, authigenic, and hydrothermal sedimentation. Biologically derived material dominates the sediment of the equatorial Pacific. The distributions of Cu and Zn are most influenced by surface-water biological activity, but Ni, Al, Fe, and Mn are also incorporated into biological material. All of these elements have equatorial accumulation maxima similar to those of opal and calcium carbonate at times during the past 50 m.y. Detritus distributed by trade winds and equatorial surface circulation contributes Al, non-biogenic Si, Fe, and Mg to the region. Detrital sediment is most important in areas with a small supply of biogenic debris and low bulk-accumulation rates. Al accumulation generally increases toward the north and east, indicating its continental source and distribution by the northeast trade winds. Maxima in biological productivity during middle Eocene and latest Miocene to early Pliocene time and concomitant well-developed surface circulation contributed toward temporal maxima in the accumulation rates of Cu, Zn, Ni, and Al in sediments of those ages. Authigenic material is also important only where bulk-sediment accumulation rates are low. Ni, Cu, Zn, and sometimes Mn are associated with this sediment. Fe is almost entirely of hydrothermal origin. Mn is primarily hydrothermal, but some is probably scavenged from sea water by amorphous iron hydroxide floes along with other elements concentrated in hydrothermal sediments, Ni, Cu, and Zn. During the past 50 m.y. all of these elements accumulated over the East Pacific Rise at rates nearly an order of magnitude higher than those at non-rise-crest sites. In addition, factor analysis indicates that some of this material is carried substantial distances to the west of the rise crest. Accumulation rates of Fe in basal metalliferous sediments indicate that the hydrothermal activity that supplied amorphous Fe oxides to the East Pacific Rise areas was most intense during middle Eocene and late Miocene to early Pliocene time.

Description: Analyses of the total alpha radioactivity distribution in 31 North Pacific manganese nodules yield an average growth rate of 6.8 ( 2) mm /m.y. Samples from a single box core show almost identical total activity vs. depth profiles, regardless of nodule size or shape. A characteristic feature of many nodules examined is an apparent change (steepening) in slope of the alpha activity profile between depths of 0.5-1.5 mm. This feature may reflect a fundamental feature of nodule growth, possibly mobility of 230Th or its daughters in a regular way, interrupted growth, or nodule turnover. Near-surface decreases in total alpha activity probably result from 226Ra loss.

Description: The cores and dredges described are taken during the R/V New Horizon RISE III Expedition from April until May 1979 by the Scripps Institute of Oceanography. A total of 36 cores and dredges were recovered and are available at Scripps Institute of Oceanography for sampling and study. The goal of this expedition was to accomplish the field work of a combined field and laboratory study aimed at increasing the understanding of the origins and development of young oceanic volcanoes.

Description: Comparison of rates of accumulation of organic carbon in surface marine sediments from the central North Pacific, the continental margins off northwest Africa, northwest and southwest America, the Argentine Basin, and the western Baltic Sea with primary production rates suggests that the fraction of primary produced organic carbon preserved in the sediments is universally related to the bulk sedimentation rate. Accordingly, less than 0.01% of the primary production becomes fossilized in slowly accumulating pelagic sediments [(2 to 6 mm (1000 y)**-1] of the Central Pacific, 0.1 to 2% in moderately rapidly accumulating [2 to 13 cm (1000 y)**-1] hemipelagic sediments off northwest Africa, northwest America (Oregon) and southeast America (Argentina), and 11 to 18% in rapidly accumulating [66 to 140 cm (1000 y)**-1] hemipelagic sediments off southwest America (Peru) and in the Baltic Sea. The emiprical expression: %Org-C = (0.0030*R*S**0.30)/(ps(1-Theta)) implies that the sedimentary organic carbon content (% Org-C) doubles with each 10-fold increase in sedimentation rate (S), assuming that other factors remain constant; i.e., primary production (R), porosity and sediment density (ps). This expression also predicts the sedimentary organic carbon content from the primary production rate, sedimentation rate, dry density of solids, and their porosity; it may be used to estimate paleoproductivity as well. Applying this relationship to a sediment core from the continental rise off northwest Africa (Spanish Sahara) suggests that productivity there during interglacial oxygen isotope stages 1 and 5 was about the same as today but was higher by a factor of 2 to 3 during glacial stages 2, 3, and 6.

Description: Stable isotopic analyses of Middle Miocene to Quaternary foraminiferal calcite from east equatorial and central north Pacific DSDP cores have provided much new informatlon on the paleoceanography of the Pacific Neogene The history of delta18O change in planktonic foraminifera reflects the changing Isotopic composition and temperature of seawater at the time of test formation. Changes in the isotopic composition of benthonic foraminifera largely reflect changes m the volume of continental ice. Isotopic data from these cores indicates the following sequence of events related to continental glaciation (1) A permanent Antarctic ice sheet developed late in the Middle Miocene (about 13 to 11.5 m.y. ago) (2) The Late Miocene (about 11.5 to 5 m.y. ago) is marked by significant variation in delta18O of about 0.5‰ throughout, indicating instability of Antarctic ice cap size or bottom-water temperatures (3) The early Pliocene (5 to about 3 m.y. ago) was a time of relative stability in ice volume and bottom-water temperature (4) Growth of permanent Northern Hemisphere ice sheets is referred to have begun about 3 m.y. ago (5) The late Pliocene (3 to about 1.8 m.y. ago) is marked by one major glaciation or bottom-water cooling dated between about 2.1 to 2.3 m.y. (6) There is some evidence that the frequency of glacial-interglacial cycles increased at about 0.9 m.y. There is significant variation in delta13C at these sites but no geochemical interpretation is offered in this paper. The most outstanding feature of delta13C results is a permanent shift of about -0.8‰ found at about 6.5 m.y. in east equatorial and central north Pacific benthonic foraminifera. This benthonic carbon shift may form a useful marker in deep-sea cores recovering Late Miocene carbonates.

Description: The thermal structure of the Pacific Ocean between water depths of about 1 and 4.5 kilometers is estimated from the oxygen isotopic ratio of benthonic foraminifera from deep-drilled and piston cores of early Pliocene age (about 3 to 5 million years ago). The ratio of oxygen-18 to oxygen-16 in the early Pliocene at each site varies by an average of only ± 0.12 per mil (1 standard deviation). A plot of the oxygen isotopic ratio against modern bottom-water temperature is adequately fit by a line having a slope of - 0.26 per mil per degree Celsius (the equilibrium temperature dependence of calcite-water fractionation), suggesting that the temperature gradient of the Pacific Ocean during the early Pliocene was similar to that of today.

Description: Manganese rich polymetallic nodules are used for trace element removal from fresh-water. The theory of kinetics and mechanisms of reactions are discussed for manganese removal. The efficiency of nodules is higher than efficiency related to other manganese removal methods. Pilot units involving continuous processes are discussed.

Description: Titanomagnetites separated from 15 different rock samples (including ocean-floor basalts from DSDP Legs 37, 45 and 46) were analyzed together with whole-rock samples by instrumental neutron-activation analysis for Sc, Cr, Co, Zn, Hf, Ta, Th and the REE La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Tm, Yb and Lu. In titanomagnetities from ocean-floor basalts and some other rocks, REE are enriched with respect to the whole-rock composition by factors of between 1.5 and 3 for light REE and between 1.0 and 1.9 for heavy REE; that is, REE with larger ionic radii are preferentially incorporated into the magnetite lattice. Three magnetite samples are REE depleted. Their whole-rock samples contain P in appreciable amounts, so apatite, an important REE-accumulating mineral, could have captured REE to some extent. All titanomagnetites show a marked negative Eu anomaly, this is most probably caused by discrimination of Eu(2+) from the magnetite lattice. Co, Zn, Hf and Ta are significantly enriched in magnetites. The distribution behaviour of Sc and Cr is masked chiefly by the crystallization of clinopyroxene and therefore is not easy to estimate. Ulvöspinel contents of about 70% for the titanomagnetites from ocean-floor basalts were estimated from qualitative microprobe analysis. Ulvöspinel contents of all other samples varied in a wide range from 20% to about 90%. No correlation could be observed between this and the REE contents of the magnetites. Ilmenite exsolution lamellae could only be observed in titanomagnetites from a doleritic basalt from Leg 45.

Description: A detailed geochemical-petrological examination of layer 2 basalts recovered during Leg 37 of the DSDP has revealed that the original distribution, form and abundance of igneous sulfide have been profoundly altered during low-grade oxidative diagenesis. The net result appears to have been a rather pervasive remobilization of igneous sulfide to form secondary pyrite accompanied by a bulk loss of sulfur equivalent to about 50-60% of the original igneous value, assuming initial saturation. It is suggested that during infiltration of seawater into the massive crystalline rock, igneous sulfide has experienced pervasive oxidation, under conditions of limited oxidation potential, to form a series of unstable, soluble sulfur species, primarily in the form of SO3[2-] and S2O3[2-]. Spontaneous decomposition of these intermediate compounds through disproportionation has resulted in partial reconstitution of the sulfur as secondary pyrite and the generation of SO4[2-] ion, which, due to its kinetic stability, has been lost from the basalt system and ultimately transferred to the ocean. This model not only satisfies the geochemical and petrological observations but also provides a suitable explanation for the highly variable delta34S values which characterize secondary sulfides in deep ocean floor basalts.

Description: Oceanic crustal drilling by R. V. Glomar Challenger at 15 sites in the North Atlantic has led to a complex picture of the upper half kilometer of the crust. Elements of the picture include the absence of the source for linear magnetic anomalies, marked episodicity of volcanic activity, ubiquitous low temperature alteration and evidence for large scale tectonic disturbance. Comparison sections in the Pacific and much deeper crustal drilling are needed to attack problems arising from the North Atlantic results.

Description: The continental slope and rise, east of Newfoundland, accommodates two distinct gravel populations. The upper slope (300-700 m depth) population is characterized by unstained, granules to boulders of predominantly granitic and terrigenous sedimentary compositon that show affinity to Paleozoic and Proterozoic rocks of Newfoundland and areas further north. The rise (2,500-〉3,000 m depth) population consists of iron- and ferromanganese-stained granules to cobbles composed mainly of carbonate that presumably has been derived from the high Canadian Arctic. The rise clasts are further distinguished in that they are finer grained, slightly more rounded and more altered by solution and/or boring organisms than their shallower water counterparts. The upper slope gravel has been reworked from underlying sediments, and deposited from ice rafts, and both processes are probably continuing today. Gravel on the rise has been concentrated through winnowing of middle Holocene sediments by the Western Boundary Undercurrent which appears to have been operative as a winnowing agent since about 4,000 to 5,000 y BP. The undercurrent has also affected the distribution of stained gravel which is most common and most intensely stained beneath a fast-flowing undercurrent core where environmental conditions resemble those documented for deep-sea, ferromanganese nodule fields.

Description: Mineralogical analysis of manganese nodules and crusts collected from Indian ocean aboard Marion Dufresne points to a depth and regional control upon the manganese oxide association: vernadite - birnessite and vernadite - todorokite. Moreover, progressive changes in the vernadite/birnessite ratio as a function of time is clearly seen. Magnetite and titano-magnetite in quantities similar to those of framboidal pyrite in manganese nodules are outlined for the first time. Study of the distribution of metals (Mn, Fe, Ni, Cu, Co) shows a strong latitudinal and regional dependence that may be connected to high productivity zones and to bottom water properties. The problem of mineralogical control on the chemical composition is approached. Finally, it results that any interpretations taking into account all these data haveway to give to the variability of sea-water properties (pH, oxygenation, motions) the prominent control upon manganese nodules composition.

Description: Surface sediments from 5 profiles between 30 and 3000 m water depth off W Africa (12-19° N) have been studied for their sand fraction composition and their total calcium carbonate and organic matter contents to evaluate the effect of climatic and hydrographic factors on actual sedimentation. On the shelf and upper slope (〈 500 m), currents prevent the deposition of significant amounts of fine-grained material. The sediments forming here are characterized by high sand contents (〉 60 %; in most samples 〉 89 %), low organic carbon contents (in most samples 〈 0.8 %), high median diameters of the sand fraction (120-500 µm), and by a predominance of quartz and biogenic relict shells (most abundant: molluscs and bryozoans) in the sand fraction. Median diameters of total sand fraction and of major biogenic sand fraction components (biogenic relict material, benthonic molluscs, benthonic and planktonic foraminifers) co-vary to some extent and show maximum values in 100-300 m water depth, reflectingthe sorting effect of currents (perhaps the northward flowing undercurrent). In this water depth, biogenic relict material is considerably enriched relative to wuartz, the second dominating sand fraction component on the shelf and upper slope, resulting in distinct calcium carbonate maxima of the bulk sediments. The influence of the undercurrent is also reflected in a northward transport of fine grained river load and perhaps in the distribution of the red stained, coarse silt and sand-size clay aggregates, which show maxima in 300-500 m water depth. They probably originate from tropical soils. Abundant coarse red-stained quartz on the shelf off Cape Roxo (12-130° N) suggests a southward extension of last glacial dune fields to this latitude. Below about 500 m water depth, current influence becomes negligible – as indicated by a strong decrease in sand content, a concomitant increase in sedimentary organic carbon contents (up to 2.5-3.5 %), and the occurence of high mica/quartz ratios in the sand fraction. Downslope transport, presumably due to the bioturbation mechanism, is indicated by the presence of coarse shelf-borne particles (glauconite, relict shells) down to about 1000 m water depth. The fine/coarse ratio (clay + silt/sand) of the sediments from water deoth 〉 500 m never exceed a value of 11 in northern latitudes (19° - 26° N), but shows distinct maxima, ranging from 50 to 120, at latitudes 18°, 17° 15°30', and 14° N in about 2000 m water depth. This distribution is attributed to the deposition of fine-grained river load at the continental slope between 18° and 14° N, brought into the sea by the Senegal and souther rivers and transported northward ny the undercurrent. Strong calcium carbonate dissolution is indicated by the complete disappearance of pteropodes (aragonite) and high fragmentation of the planktoic foraminifers (calcite) in sediments from water depth 〉 300-600 m. Fragmentation ratios of planktonic foraminifers were found to depend on the organic carbon/carbonate ratios of the sediment suggesting that calcite dissolution at the sea bottom may also be significant in shelf and continental slope water depths if the organic matter/carbonate ratio of the surface sediment is high and the test remain long enough within the oxidizing layer on the top of the sulfate reduction zone. The fact that in the region under study intensity and anual duration of upwelling decrease from north to south is neither reflected in the composition on the sand fraction (i.e. radiolarian and fish debris contents, radiolarian/planktonic foraminiferal ratios, benthos/plankton ratios of foraminifers), nor in the sedimentary organic carbon distribution. On the contrary, these parameters even show in comparable water depths a tendency for highest values in the south, partly because primary production rates remain high in the whole region, particularly on the shelf, due to the nutrient input by rivers in the south. In addition, several hydrographic, sedimentological and climatic factors severely affect their distribution – for example currents, dissolution, grain size composition, deposition of river load, and bulk sedimentation rats.

Description: A study of samples from DSDP Leg 47 shows that transformation of organic matter in deep sea sediments is completly analogous to evolution of organic matter in sedimentary sequences on continents and depends on the same factors. Crucial among these factors are: genesis of organic matter, nature of its diagenetic changes, and current stage of catagenesis.

Description: This report deals with results of the first stage of a complex study of the predominantly Lower Cretaceous sediments cored at Site 398 at depths from 945 to 1740 meters. The section studied is overlain by 35 meters of Cenomanian sediments, which are similar lithologically to the underlying sequence. In the upper part (Unit 3) a major rock-forming carbonate mineral is present in much of the section as calcite, often with distinct structural features indicative of a biogenic origin (nannofossils, skeletal detritus) and diagenetic recrystallization. Unit 3 is characterized by abundant authigenic minerals represented mainly by siderite and manganese-bearing carbonate minerals.

Description: 59 box and gravity cores from the MANOP cruise with RV KNORR in 1979 were described and alaysed.

Description: Regional variations in abundance, morphology, and chemical composition of Fe-Mn nodules have a zonal character. Due to circumcontinental zonality of terrigenous sedimentation the main mass of the nodules occurs in the pelagic part of the ocean, in areas of minimal sedimentation rates. In spatial variations in morphology and chemical composition of the nodules the latitudinal zonality is very clear and associated with latitudinal changes in facial conditions of sedimentation. Elevated contents of Mn, Ni, and Cu and of Mn/Fe ratio occur in nodules from the radiolarian belt. Changes of chemical composition of the nodules with depth (vertical zonality of mineralization) are confirmed. Local variations in abundance, morphology and chemical composition of the nodules are caused by ruggedness of relief and depth variations, variations in sedimentation rate, age of ore formation, intensity of diagenetic redistribution of metals.

Description: Deep sea photographs in the GH77-1 cruise were obtained by two methods, namely a one-shot 16 mm camera attached to the freefall (boomerang) type photo grab and an independent 35 mm deep sea camera.

Description: Phosphatized bioclastic limestones of Early Tertiary age have been dredged from the crest of a seamount in the equatorial Atlantic near 9°N, 21°W. The samples were recovered from water depths of 700 to 970 m but clearly were deposited in a high-energy reefal environment, thus indicating significant Tertiary subsidence. The vertical movement is beleived to reflect reactivation of an old structural line, the Guinée Fracture Zone, which may have had important effects on the transfer of bottom waters of polar origin between the Sierra Leone and Gambia basins. Examination of foraminiferal limestone coating the shallow water material suggests that deep-water conditions were established on the seamount by Middle Miocene time. All phosphatized samples are covered with a layer of ferromanganese oxides which, from textural and faunal evidence, is Palaeocene or Eocene in age and of shallow water origin. Pervasive phosphatization of the bioclastic limestones appears to have been accomplished before the end of the Eocene while the crest of the seamount was near sea level, because Upper Eocene limestone of shallow water facies is unaffected by such radical diagenesis. Phosphatization probably was associated with vigorous upwelling near the seamount and has been taken to an unusually advanced stage, resulting in a phosphoritesof high economic grade. P2O5 contents are in the range of 37 to 41%. The purity of the phosphorites may be related to the intensity of upwelling during the Early Tertiary, but other factors such as the paucity of terrigenous detritus, frequent reworking of the sedimentary capping of the seamount, and a high primary porosity of the limestones may have been important in their information. The Early Tertiary period of phosphorite deposition on the seamount and in northwest Africa ended before the close of Eocene time in both areas, while shallow water conditions prevailed. It is argued that the cessation of phosphorite formation reflects major changes in the surface circulation of the Atlantic during the Eocene.

Description: The rate of accumulation of a ferromanganese coating on a fragment of pillow basalt was estimated using a variety of techniques. Unsupported 230 Th activity decrease in the oxide layer, K/A dating of the basalt, fission tracks dating of the glassy layer around the basalt, thickness of the palagonitization rind, and integrated 230 Th activity give ages from approximately 3 x 10-6 years to 5 x 10-3 years. Data suggest that the ferromanganese material formed rapidly (33 mm/10-6 years) and by hydrothermal or volcanic processes.

Description: The volcanic deposits which surround Vulcano Island may be classified in four phases : a detritic phase, fed from the Island itself and from Sicily; a siliceous and carbonateous organic phase; a neogenesis mineral phase; a precipitation phase. The formation of clay and the mineralization of iron and manganese are the subject of particular study. A number of indications suggest the littoral neogenesis of kaolinite around hydrothermal issues, and the formation of smectite at greater depths. The distribution of iron mineralization in the Baie du Levant follows the physicochemical variations of the environment. Melnikovite, pyrite, marcassite and pyrrhotin are dispersed in aureoles around swallow emission points (fumaroles). Close to the hydrothermal spring, iron precipitates are found in the form of amorphous hydroxydes, while geothite and hematite characterize the deeper area as a whole. Manganese mineralizations are exclusively represented by hydroxides and oxides, locally (about - 250 m) organized as incrustations on. lapilli glasses (micronodules). These would appear to be related to the hydrothermal spring.

Description: The growth rate of a manganese nodule from the South Atlantic Ocean (Rio Grande Ridge) has been determined using a 10Be profile as measured with a Tandem Van de Graaff accelerator. This rate is 4.5 mm /My. A correlation may exist between the 10Be flux and the Mn flux to nodules.

Description: The suite of gabbroic rocks collected by the DSRV ALVIN in 1976 and 1977 from the walls of the Mid-Cayman Rise spreading center were studied in detail to provide the best available data on plutonic rocks sampled directly from the ocean floor. The rock types studied include variably deformed and altered gabbros, orthopyroxene gabbros, olivine gabbros and troctolites, and a few amphibolites. Mineral chemical analyses suggest that the various rock types are representative of a fractionation trend from magnesian troctolites through olivine and clinopyroxene gabbros to iron-enriched orthopyroxene gabbros. Within many individual samples, the primary mineral phases are apparently chemically homogeneous despite sometimes considerable alteration, which suggests reequilibration after original crystallization. Variation in mineral-chemistry across the suite is larger than previously reported for ocean-floor gabbros; this may be due to the larger population of this study. The primary or secondary nature of plagioclase and amphibole must be distinguished in discussions of the igneous processes involved in the genesis of these rocks. In this suite, textural evidence is often inconclusive, and although sodic chemistry is assumed to indicate a secondary origin for plagioclase, no chemical indicator was found to apply to amphiboles. Many different deformation textures are observed in the samples, indicating considerable variation in the conditions of deformation within this slowly accreting ridge environment. Ductile features range from mechanical twins and bent crystals (low strain) to complete recrystallization with a well-developed foliation (high strain). Textures suggestive of cataclasis include zones .1-10 mm wide containing very fine, irregular grains; kinked and cracked grains, usually very undulose; and crosscutting fractures. These textures may occur separately, or next to or overprinting each other. Of the variables controlling the formation of deformation features, temperature and water pressure are most easily estimated. Minimum temperature during deformation is suggested by minimum temperature of formation of mineral assemblages unaffected by this deformation. This temperature is greater than 550°C (epidote-amphibolite facies) for the majority of features observed, although sampling may have introduced a bias away from lower temperature features. Observations suggest enhanced recrystallization where the primary mineralogy has been hydrated to a greater extent. Theoretically, confining pressure for the gabbroic rocks in this suite may have varied from about .3-.9kb; fluid pressure should have been within these limits. Based on mineralogical evidence, cataclastic and ductile textures developed at both high and moderate temperatures. This suggests that strain rates and/or pressure vary considerably within regions where rocks are hot as well as where rocks are cooler, and that after high-temperature deformation some rocks cooled quickly enough to prevent significant recrystallization while others cooled more slowly. These interpretations indicate that the Cayman plutonics were raised to their present position by motions which varied from place to place and time to time, and suggests that the structural history of plutonic.rocks formed at slowly accreting plate boundaries is highly variable and complex.

Description: Ranging in height from gentle hills of less than a meter to steep-sided giants of more than 20 m, the mounds of the Galapagos Rift are spectacular hydrothermal features. Their internal temperatures have been measured at up to 13°C above the bottom water temperature, and total heat flow (conducted plus convected) can be several hundred to several thousand times the normal oceanic values. Fluids, when they discharge from the mound, do so at a very slow rate and at temperatures probably quite near the bottom water temperature. The mounds are principally composed of iron silicates intermixed and incrusted with lesser amounts of manganese oxides. They are generally found in rows, in a uniformly sedimented area above faults or fractures in the crustal rocks which permit fluids to escape from a deep hydrothermal aquifer. The sediment blanket in some way alters the chemistry of the ascending thermal fluids and leads to the development of mounds. The mounds field, covering an area of at least 200 km2 and consisting of thousands of individual mounds, is probably less than 300,000 years old; and many of the mounds may be only a few tens of thousands of years old or less.

Description: Leg 43 was planned to examine a wide variety of geological problems at numerous sites in the deep western North Atlantic basin. A variety of objectives were to be addressed on Leg 43,among these: 1) to investigate the sedimentary development of the North American basin, 2) to recover sediments containing late Mesozoic and Cenozoic fossils for biostratigraphic, paleobiogeographic, and paleoceanographic studies 3) to recover samples of basaltic basement from the smooth crest of the basement ridge associated with the northern part of the New England seamounts, 4) To examine the age and nature of volcanism on Bermuda and along the New England seamount chain, in order to test ideas on volcanic* origin such as the "hotspot" hypothesis, and to examine volcaniclastic lithofacies and assess the role of volcanic sources for certain North Atlantic sediments.

Description: This paper summarizes the petrography and major element chemistry of basalt collected by R/V Atlantis II at 23 °N, and compare these data with published data for 22 °N and with the preliminary shipboard data for DSDP Sites 395 and 396, in order to define the regional petrologic setting of the Leg 45 basalts.

Description: A combined mineralogical, petrological, and geochemical study of altered basaltic rock samples of the upper oceanic crust from Hole 396B IPOD Leg 46. The hole was drilled on the west flank of the Mid-Atlantic Ridge, in anomaly 5 at about 23°N. The site is located in a sediment pond at a water depth of 4450 meters; 205 meters of pillow lavas intercalated with indurated ooze and one exceptionally thick lava unit (sill or flow?) were drilled.

Description: Leg 45 of the Deep Sea Drilling Project was the inaugural cruise of the International Phase of Ocean Drilling. Its primary scientific objective was to develop an understanding of the composition, structure, and origin of oceanic crust by drilling as deeply into it as technology would permit. The feasibility of drilling deep into the oceanic crust was demonstrated during Leg 37 when one hole was drilled 586 meters into basaltic volcanic rocks near the crest of the Mid-Atlantic Ridge at about 37 °N. The areas of principal interest for Leg 45 were survey areas AT-5, situated near 23 °N, 46 °W and AT-6 near 23 °N, 43°W. The two survey areas are on opposite sides of the Mid-Atlantic Ridge, south of the Kane fracture zone. During Leg 45, Holes 395 and 395A were drilled in survey area AT-5 and Hole 396, was drilled in survey area AT-6.

Description: Unlike many cruises of the Deep Sea Drilling Project, Leg 48 was scientifically planned to drill a number of sites to systematically address the problems of passive margin evolution. Site 400 was drilled at the foot of the Meriadzek Escarpment of North Biscay in 4399 meters depth. The site was located in a half-graben forming part of a succession of tilted and rotated fault blocks near the continent/ocean boundary. Site 401 was situated on the planated edge of a tilted fault-block underlying the southern edge of the Meriadzek Terrace on the north Biscay margin. Site 402 was located on the upper slope of the northern continental margin of the Bay of Biscay. The main objectives were to establish the presence or absence of shallow water Upper Cretaceous beds, and to penetrate pre-Aptian synrift sediments and the upslope equivalent of the deep water Albian-Aptian carbonaceous mudstones penetrated at Hole 400A.

Description: Leg 49 of the International Phase of Ocean Drilling (IPOD) was designed with a wide spectrum of problems in mind. Topics investigated were (1) variation with time of mantle sources of spreading-center magmas, (2) aging of the volcanic layer, (3) degree of hydrothermal alteration and metamorphism of the volcanic layer, (4) lateral and vertical variation of the petrochemistry, magnetic properties, and structure of the volcanic layer, (5) north-south variability of spreading-center magmas through the North Atlantic, (6) initiation of glaciation during the late Pliocene, and (7) the influence of bottom currents originating at the Iceland-Faeroes Ridge on sediments of the ridge flank province of the western North Atlantic.

Description: 35 km either side of the Pacific-Cocos spreading axis at 846'N, on crust 0.6 x 10SUP-6 years old, a pair of small seamounts rises 1.4 km above the faulted terrain of young abyssal hills. A high-resolution traverse made with the sonars and cameras of a deeply towed vehicle shows that the seamounts are inactive volcanoes, with concave side slopes that steepen upwards to 30, and then abruptly flatten at 2-4 km wide summits. Ledges of pillow basalt outcrop on the lower slopes, and form some talus slopes, but the superficial rock of the upper slopes appear to be mainly hyaloclastite. A transponder-navigated deep-tow survey at the summit area of the eastern seamount mapped an asymmetric caldera containing 3 pit craters, which have vertical walls and flat floors. Dredging across the caldera floor recovered hyaloclastite, angular fragments of primitive tholeiite, and manganese nodules. The paired seamounts probably had a common origin at a 'hot spot' on the spreading axis; continued to grow after they were split by sea-floor spreading; and became extinct and suffered summit collapse after they spread too far from their magma source.

Description: In Costa Rica the manganese deposits are an integral part of the Nicoya ophiolite complex. They contain both primary mineralization and, due to weathering, small residual concentrations. The most common manganese minerals in surface outcrops are psilomelane and pyrolusite. Most of them exist in jasper bodies often in a form of breccia in contact with underlaying basalt. In some instances stratiform manganese-oxide crusts and nodule deposits cap jasper bodies and stratabound deposits being overlain by radiolarites.

Description: One of the main objectives of the International Phase of Ocean Drilling (IPOD) of the Deep Sea Drilling Project was to determine the geological, geochemical, and geophysical character of ocean crust formed at mid-ocean spreading ridges. A series of drill holes along the Mid-Atlantic Ridge (MAR), from near Iceland south to approximately 22°N latitude, was planned to compare the crust being generated near an anomalous ridge (Iceland) with that originating near a normal slow-spreading ridge (22°N). At the same time, a series of holes in near zero-age crust at 22 °N was planned along a "flow line" (a transect parallel to local fracture zones) trending west into increasingly older crust, eventually extending the sampling to crust of apparent Jurassic date off the eastern United States coast. This age-transgressive transect was designed to test the evolution of crust formed at one point in the spreading ridge. The intersection of these two series of holes was designated Atlantic Site 5 and was positioned on the upper western flank of the Mid Atlantic Ridge near 22 °N latitude, as close as possible to the spreading ridge crest. The R/V Kana Keoki conducted a detailed 22-day survey of Atlantic Site 5 during Cruise 74-01-01, Leg 7 prior to the DSDP Leg45 was conducted.

Description: In surface sediment at the three DOMES sites in the equatorial North Pacific, the percentage of reworked fauna and the thickness of the acoustically transparent uppermost layer increases from east to west (Sites C to B to A) and the percentage of volcanogenic products decreases. On the basis of lithology and acoustic signature (3.5 kHz) this sediment can be correlated with surface sediment recovered in Deep Sea Drilling Project cores from this same area. It has been assigned to the radiolarian ooze unit of the Clipperton Ocean Formation. The underlying Marquesas Oceanic Formation, well documented in DSDP cores, was not observed in DOMES cores but was identified in the acoustic records as an acoustically transparent to weakly reflective unit. In the study area, the Clipperton Formation is commonly deeply eroded and unconformable with the sea-floor surface, but the Marquesas Formation is present everywhere and has a fairly uniform thickness.

Description: Recent study of many box cores and deep sea photographs from DOMES Sites A, B, and C throws new light on the mode or occurrence of manganese nodules in the Horn Region o f the Pacific. Most bos cores from which the supernatant water has been carefully removed show nodules resting on a relatively firm mud surface, and deep imbedding is rare except for very large nodules; yet many bottom photographs from sites nearby show nodules well-imbedded in what appears to be soft muddy sediment. Observations of nodules still covered by sea water in box cores and experiments designed to preserve the natural relationships between nodules and sediment may explain this paradox. We conclude that at least the upper part of the original sediment, which we call the sediment-water interface "boundary layer", collapses when de-watered to form a wet mud only a fraction the thickness of the material on the sea bed. The relatively firm mud upon which nodules rest in many box cores is thought to underlie the boundary layer at a fairly abrupt contact, but the boundary layer proper probably grades upward, becoming progressively more water-rich, to a diffuse contact with sea water. Small nodules tend to be suspended in the boundary layer and grow largely or totally surrounded by it. As nodules grow, they may reach a size which permits anchoring in the firmer mud below by growth o f oxide dendrites downward, with the result that morphology becomes more asymmetrical as overall growth proceeds. Nodules grow by adding the crystalline manganese oxides todorokite and birnessite where they are in contact with sediment or sediment rich water and iron-rich amorphous oxides where they are in contact with the sea water above. Nodules which show alternating Mn-rich and Fe-rich internal layers may owe this pattern to long-continued sedentary growth during which periods of exposure to sea water alternated with periods during which the upper nodule surface was covered by the boundary layer. Similar nodule structures may also result from periodic overturn of nodules, and many nodules probably experience both kinds of events. The long-standing problem of concentration of manganese nodules at the present deep sea sediment-water interface may be partly explained by the unusual properties of the boundary layer. Although it appears to be both fragile and mobile, it also seems to have a cohesiveness or strength which permits it to hold nodules in suspension in spite of the relatively high density or most nodules. The presence o f organic material (mucoprotein) may contribute to the special properties of the boundary layer. There is photographic evidence that the boundary layer may hide small nodules from view in camera surveys, but the layer is so mobile that even bottom organisms can remove it. The use o f some kind of simple "cleaning" device during camera surveys may produce photographs which give a more accurate record o f nodule distribution than is presently possible.

Description: Cores, submarine photography and dredges described in this report were taken during the R/V Knorr Cruise K79-05 in 1979. Cores and dredges were recovered for 43 stations.

Description: Manganese nodules and associated sediment from the equatorial North Pacific have been examined to ascertain relations between nodule abundance, texture, and composition, and sediment composition, lithology and acoustic stratigraphy. Nodules are most abundant in areas where the uppermost acoustically transparent layer of sediment is less than approximately 15 m thick. Abundance drops off sharply in areas where this acoustic unit is thicker than 20 m. Nodules have average Zn/Mn and Co/Mn ratios which are approximately the same as these ratios for the component of sediment soluble in hydroxylamine hydrochloride-acetic acid. The relations between Cu and Mn and Ni and Mn in the sediment are also approximately the same as in nodules, but only for those nodules which have a smooth surface texture. Granular nodules have relatively more Ni and Cu. Antimony in nodules, similar to Ni, Cu, and Zn, is strongly correlated with Mn, whereas Co, Hf, Th, and U are strongly correlated with Fe. The insoluble component of sediment has a uniform composition which is similar to the composition of terrigenous shale. This similarity holds for the major oxides as well as for Co, Cr, Zn, Hf, Sb, Th, U, Sc, Cs, Rb, and Ta.

Description: Shebandowan Lakes, Ontario, are the site of at least 49 shallow (2-12 m) ferromanganese concretion deposits, widely distributed throughout the 48 km of the watercourse. X-ray diffraction and Mossbauer methods have revealed the presence of goethite in some of the concretions. Chemical analyses of the acid soluble portions of 72 samples gave an average composition of 43.1% Fe and 5.65% Mn with a low content of trace elements. The Shebandowan concretions are among the richest in iron of lake concretions reported, possibly because only the acid soluble portion was analysed. Their low content of trace elements suggests rapid growth rates and a relatively young age. A positive correlation was found between Mn and K, Ca, Mg, Cu, Ni, and Co and the relationship between the last three and Mn was deemed significant. Zn was independent of association with either Mn and Fe, probably due to the presence locally of zinc sulphide deposits. Analyses of lake bottom and influent waters suggested that frequent resampling of the sites would be required throughout the year to permit meaningful interpretation of the effect of water composition of concretions. Analyses of sediment cores from 20 concretion sites indicated an upward increase in Fe and Mn and in the Mn/Fe ratio, consistent with the model of upward migration of the elements, where Mn is more mobile than Fe. This study concludes that a considerable proportion of the elements have been supplied to the Shebandowan concretions via the diagenetic process; generally a minor fraction of the elements has been abstracted directly from the superjacent water.

Description: Information on possible resource value of sea floor manganese nodule deposits in the Pacific has been assessed by Deepsea ventures Inc, from the collection of manganese nodules and crusts obtained during past research vessels' cruise from the Scripps Institution of Oceanography.

Description: Mineralogical and chemical analysis of an Eastern Pacific core has been conducted in the context of a study of mineralisations in pelagic sediments; the data point out the relations between thin (2-100 m) manganese oxyhydroxide concretions and volcano-sedimentary environments. Between Clarion and Clipperton Islands, the polymetallic precipitates are precocious and they are due to the submarine volcanic activity of this spreading zone; in spite of their small size, all the elements are concentrated in the precipitates: Mn (9-46%), Fe (0.2-11%), Ni (0.1-3.4%), Cu (0.1-1.7%), Co (0.1-0.8%). The high internal structuration of micromineralisations, the splitting up of the elements in the laminations, the variability of contents according to the state of crystallinity can be explained by diagenetic processes at the scale of the grain. The contrast between the degree of evolution of these mineralisations and the situation of the area, that was submitted to important terrigenous and volcanic sedimentary inputs, lead to consideration of the micronodules as 'blocked structures', precursors of nodules, developed from diagenetic reactions of the micro-environment.

Description: Manganese nodules from six Pacific Ocean sites contain two chief oxide components which can be distinguished by both optical and X-ray diffraction methods. Optically coordinated electron microprobe spot analyses reveal that copper and nickel are concentrated in the manganese-rich crystalline oxides (birnessite and todorokite) while cobalt is concentrated in the iron-rich amorphous oxides. In the nodules studied the maximum nickel content in the crystalline material is 3.6%, while the maximum copper content is 2.95%. The highest cobalt content found in the amorphous material was 0.74%. Large variations in concentrations were found within individual nodule layers as well as from one layer to another. Most of the variations cannot be accounted for by admixed nodule components. The variations cannot be distinguished by any optical or X-ray diffraction criteria and are probably controlled by the availability of the elements during primary deposition. There does not appear to be any linear interelement relationship between concentrations of the major elements (Mn and Fe) and the minor elements (Ni, Cu and Co). Linear relationships that have been reported in the past must be interpreted with care, for crystalline oxides and amorphous oxides may have been mixed in varying amounts during the sampling. In view of the different element associations in the crystalline and the amorphous oxides, the main factor for controlling bulk chemical analysis of a particular nodule appears to be the ratio of crystalline to amorphous material in the nodule. NSF-IDOE support of this research is acknowledged with thanks.

Description: In the GH77-1 cruise, manganese nodules were obtained from 31 stations among 37 total ones. Here are reported the preliminary results of the observation mainly done on-board. Special attention was paid to confirming the applicability of the nodule type classification tentatively established in the previous GH76-1 cruise and to delineating the pattern of the nodule distribution and clarifying its relation to the geological factors, such as topography, surface sediment types, and substrate stratigraphy. In addition, a short description of the obtained rock samples from a few stations is included in this chapter.

Description: Basalts from the base of a small seamount on ~1.5-m.y.-old crust west of the East Pacific Rise (EPR) at 9°N are intermediate in chemical and isotopic composition between light-rare-earth-element-depleted tholeiite (normal midocean ridge basalt (MORB)) and alkali basalt. Like oceanic alkali basalt, these rocks contain significantly more Ba, K, P, Sr, Ti, U, and Zr than normal MORB. Since the absolute abundances of these elements are still well below alkali basalt levels, the label transitional is adopted for these basalts. A series of fractionated MORB also occurs in this area, northwest of the Siqueiros Fracture Zone - Transform Fault. The normal tholeiites are either olivine-plagioclase or plagioclase-clinopyroxene phyric, while the transitional basalts are spinel-olivine phyric. Fractional crystallization quantitatively accounts for the chemical variability of the tholeiitic series but not for the transitional basalts. The tholeiitic series probably evolved in a crustal magma chamber ~4 km below the crest of the East Pacific Rise. 143Nd/144Nd and other chemical data suggest that the large-ion-lithophile-enriched transitional basalts may represent a hybrid of normal MORB and Siqueiros area alkali basalt. Incompatible element plots of K, P, and U indicate possible derivation of the transitional basalts by magma mixing. Magma mixing of unfractionated normal MORB and Siqueiros alkali basalt has been quantified. Derivation of the transitional basalts from a 1:1 mixture is supported by all available chemical data, including Cr, Cu, Nd, Ni, Sm, Sr, U, and V. This magma mixing apparently occurred at ?〈~30 km depth within a few tens of kilometers from the EPR axis. These Siqueiros area EPR transitional basalts are compared with Mid-Atlantic Ridge (MAR) transitional basalts from the Iceland and Azores areas. The Siqueiros area basalts reflect a profound chemical and isotopic heterogeneity in the upper mantle, similar to that found along the MAR. Unlike the MAR, the EPR shows no evidence of plumelike bulges and associated large-scale outpourings of nonnormal MORB resulting from these mantle heterogeneities. Siqueiros alkali basalt and MORB, as well as transitional basalt and MORB, were recovered from single dredge hauls. Such close spatial and temporal proximity of the inferred mantle sources places severe constraints on geometric and physicochemical upper mantle models.

Description: Manganiferous soil concretions have been located in pineapple and sugar cane plantations of the Schofield Plateau, Oahu, and black manganiferous coatings on the surface of soils have been observed on the crests of embankments next to pineapple plantations on Oahu, Molokai, and Lanai. The concretions and coatings are found inoxisols derived from volcanic parent material. The moisture regime of the soils is characterized by alternate wet and dry periods. This alternation facilitates remobilization and reprecipitation of manganese and to a much lesser extent iron and associated trace metals in the soils. Optimum conditions for manganiferous soil concretion development are encountered on the Schofield Plateau, where mean annual rainfall exceeds 1000 mm/year but where there is a net evaporation loss from the soils during the dry period (May through October). Remobilization of manganese is less pronounced in the oxisols of Molokai and Lanai, where mean annual rainfall is lower. Thin manganiferous coatings rather than concretions therefore form in these islands. The contents of Mn, Fe, Cu, and Ni of the soils on which Hawaiian concretions form are higher than those of New Zealand soils in which manganese soil concretions are found. This is reflected by the much redder color of the Hawaiian concretion-bearing soils compared with their New Zealand counterparts. Rare earths show an enrichment sequence: parent rock ---+ soil ---+ soil concretion. A small positive Ce anomaly is noted in the soil and is more marked in the concretions. This may be due to the increasing oxidation of Ce in the concretions relative to the soil, although contamination of the soil by concretionary material may also playa role. The parent rock shows no Ce anomaly. Barium and Pb are enriched in concretions relative to the surrounding soil, whereas D, Th, Hf, Nb, Zr, and As are present in similar or higher concentrations in the soil relative to the concretions. Arsenic may follow Fe in the soils. Todorokite is the predominant manganese mineral in the Hawaiian soil concretions, not pyrolusite as previously reported. Scanning electron microscope studies show the crystalline nature of the manganese oxide minerals in the concretions.

Description: This report presents the preliminary results of the study of rocks and sediments obtained by dredging during four cruises of the R/V Jean Charcot and R/V Le Suroit during a cooperative program between CNEXO and CEPM (CH 58: April 1975; SU 01: December 1975; CH 66: February 1976; and CH 67: March 1976). Several dredges on the continental slope of the Goban Spur recovered "granitic" rocks on two morphological structures, Granite Cliff and "Menez Bihan" (Pautot et al., 1976), in water depths ranging from 3200 to 4200 meters. According to the radiometric age and petrology, the granodiorite appears to have a close affinity with similar igneous facies which have been described in Iberia (Capdevilla et al., 1973) and attributed to the Variscan intrusive episode which is also found in the nearby continental area (southwest Great Britain and Brittany, France). They often are coated by a centimeter-thick layer of ferromanganiferous deposits (Shaaf et al., 1977).

Description: The purpose of this volume, the ninth in a series of similar publications (Goodell, 1964, 1965, 1968; Frakes 1971, 1973 ; Cassidy et al., 1977), is to continue a presentation to the research community of sediment core descriptions and attendant data of cored and otherwise obtained sediments retrieved in waters of the Southern Ocean aboard the research vessel, ARA Islas Orcadas (formerly, USNS Eltanin), as a part of the circumpolar survey begun by Eltanin in 1962 (see issue of Antarctic Journal of the United States, Vol. 8, No. 3, 1973). The data presented herein are concerned with the results of coring activities aboard cruise 1277 of Islas Orcadas, the third marine geology coring cruise of this vessel under the terms of the present United States-Argentine agreement. The core descriptions are organised as follows: 1) a brief summary of the coring objectives of the cruise, together with a discussion of core recovery; 2) a table and map of station location data for materials retrieved; 3) a table of tentative age-dates for each piston core; 4) an explanation of the laboratory procedures and descriptive criteria used in the description of the sediments, and 5) lithologic descriptions of the piston and trigger cores, and the piston and trigger core bag samples.