Abundance and chemical and mineral compositions of nodules from the Pacific Ocean

The monograph highlights extensive materials collected during expeditions of P.P. Shirshov Institute of Oceanology. We consider facial conditions of nodule formation, regularities of their distribution, stratigraphic position, petrography, mineral composition, textures, geochemistry of nodules and hosting sediments. Origin of iron-manganese nodules in the Pacific Ocean is considered as well.

Rare earth and other chemical element contents and partitions in bottom sediments, micronodules, and nodules from the bioproductive zone of the Pacific Ocean

Concentrations and compositions of rare earth elements (REE) in three micronodule fractions (50-250, 250-500, and >500 ?m), coexisting macronodules, and host sediments were studied. Samples were collected at three sites (Guatemala Basin, Peru Basin, and northern equatorial Pacific) located in elevated bioproductivity zones of surface waters. Influence of micronodule size is dominant for REE compositions and subordinate for REE concentrations. For example, Ce concentration inversely correlates with micronodule size and drops to the lowest value in macronodules and host sediments. Decrease of Ce concentration is generally accompanied by Mn/Fe increase in micro- and macronodules. Hence, the role of diagenetic source of material directly correlates with micronodule sizes. Contribution of the diagenetic source is maximal for macronodules. REE composition distinctions for micronodules and macronodules can be attributed to variations of hydrogenic iron oxyhydroxides and diagenetic (hydrothermal) iron hydroxophosphates that are the major REE carriers in ferromanganese ore deposits. Relationship and general trend in chemistry of coexisting macronodules suggest that they can represent products of the initial stage of nodule formation.

Geochemistry on Yangla copper deposit, China

The Yangla copper deposit, situated in the middle section of Jinshajiang tectonic belt between Zhongza-Zhongdian block and Changdu-Simao block, is a representative and giant copper deposit that has been discovered in Jinshajiang-Lancangjiang-Nujiang region in recent years. There are coupled relationship between Yangla granodiorite and copper mineralization in the Yangla copper deposit. Five molybdenite samples yielded a well-constrained 187Re-187Os isochron age of 233.3±3 Ma, the metallogenesis is therefore slightly younger than the crystallization age of the granodiorite. S, Pb isotopic compositions of the Yangla copper deposit indicate that the ore-forming materials were derived from the mixture of upper crust and mantle, also with the magmatic contributions. In the late Early Permian, the Jinshajiang Oceanic plate was subducted to the west, resulting in the formation of a series of gently dipping thrust faults in the Jinshajiang tectonic belt, meanwhile, accompanied magmatic activities. In the early Late Triassic, which was a time of transition from collision-related compression to extension in the Jinshajiang tectonic belt, the thrust faults were tensional; it would have been a favorable environment for forming ore fluids. The ascending magma provided a channel for the ore-forming fluid from the mantle wedge. After the magma arrived at the base of the early-stage Yangla granodiorite, the platy granodiorite at the base of the body would have shielded the late-stage magma from the fluid. The magma would have cooled slowly, and some of the ore-forming fluid in the magma would have entered the gently dipping thrust faults near the Yangla granodiorite, resulting in mineralization.

Composition of minerals at DSDP Leg 67 Holes

During the Leg 67 drilling of the Middle America Trench (Guatemala transect), basalts were reached in Hole 495, 22 km seaward from the Trench axis, in Holes 500 and 500B at the foot of the continental slope, and at four other holes not sampled for this study. Only olivine-plagioclase phyric basalts are present in Hole 495, whereas in Holes 500 and 500B these rocks are associated with plagioclase phyric high-alumina basalts. As illustrated by the content of TiO2, Al2O3, and the K2O/K2O + Na2O ratio, some of the Middle America Trench basalts do not differ essentially from oceanic tholeiites, but others have a composition transitional to island-arc tholeiitic basalts. It is suggested that basalts transitional from oceanic to island-arc tholeiites are typical manifestations of magmatism in zones of convergence of the oceanic and continental or island-arc crust.

Composition of bottom sediments, rocks, and ores from the Tropical Atlantic

Geological features of some areas of the Tropical Atlantic (stratigraphy, tectonic structure, lithology, distribution of ore components in bottom sediments, petrography of bedrocks, etc.) are under consideration in the book. Regularities of concentration of trace elements in iron-manganese nodules, features of these nodules in bottom sediments, distribution of phosphorite nodules and other phosphorites have been studied. Much attention is paid to rocks of the ocean crust. A wide range of mineralization represented by magnetite, chromite, chalcopyrite, pyrite, pentlandite, and other minerals has been found.

Composition of hydrothermal manifestations in the World Ocean

The monograph summarizes results of studies of hydrothermal fields on the ocean floor, hydrothermal plumes and metalliferous sediments. Hydrothermal ore manifestations formed in different geodynamic settings, with different character of volcanism in different facial conditions of deposition are described. Causes of non-uniformity of hydrothermal system functioning in different parts of the ocean and therefore variability of hydrothermal deposits are under consideration. On the base of found relationships of these irregularities with geodynamics, volcanism and sedimentation a new classification of hydrothermal processes and genetic models of hydrothermal ore formation in the ocean have been created. Regularities of hydrothermal sedimentary material dispersion in bottom waters are discussed.

Geochemistry and granulometry of sediments obtained during R/V Professor Logachev cruise PL28, Mid Atlantic Ridge

The lithological-facies, biostratigraphic, and geochemical studies of ore-bearing and metalliferous sediments were carried out using original material from six cores taken in the MAR 16°38' N area during 28th Cruise of the R/V Professor Logachev.

Composition of bottom sediments and serpentinites from Core PS-846

A core of foraminiferal-coccolithic oozes filling a valley of the transform fault located at 29°40'S on the South Atlantic Ridge contains layers composed of angular fragments of igneous and metamorphic rocks. They include many serpentinites deriving from serpentinized ultrabasic rocks, probably exposed on the lower section of the southern slope of the fault valley. A mineral and chemical description of these serpentinites is given.

Properties, sedimentation and accumulation rates, and chemical composition of bottom sediments from the Deryugin Basin, Sea of Okhotsk

Results of a study of contents and accumulation rates of Fe, Mn, and some trace elements in Upper Quaternary sediments of the Deryugin Basin are presented. Maps of average contents and accumulation rates of excessive Fe, Mn, Zn, Ba, Ni, Pb, Cu, and Mo in sediments of the first oxygen isotope stage (OIS) have been plotted. Anomalous contents and accumulation rates are confined to peripheral zones of the Deryugin sedimentary basin and large fracture zones. Different mechanisms of influence of fluid-dynamic processes on rate of hydrogenic and biogenic accumulation of ore elements are assumed.

Chemical and mineral compositions of sulfide deposits from the Snake Pit hydrothermal field, Mid-Atlantic Ridge rift zone

The Snake Pit hydrothermal field is located on the top of a neovolcanic rise on the Mid-Atlantic Ridge at sea depths between 3460 and 3510 m. It was surveyed during several oceanological expeditions including DSDP Legs. Additional scientific materials were obtained in 2002 and 2003 during expedition onboard R/V Akademik Mstislav Keldysh with two Mir deep-sea manned submersibles. Three eastern hydrothermal mounds (Moose, Beehive, and Fir Tree) are located on the upper part of the eastern slope of the rise over a common fractured pedestal composed of fragments of massive sulfides. The western group of hydrothermal deposits is encountered on the western slope of the axial graben. Within this mature hydrothermal field, which was formed over the past 4000 years, we studied morphology of the hydrothermal mounds, chemistry and mineralogy of hydrothermal deposits, chemistry of sulfide minerals, and isotope composition of sulfur in them.

Composition and age of bottom sediments from the Southern Ocean

Geomorphology, geology, stratigraphy, lithology and geochemistry of bottom sediments in the South Ocean are under consideration. Regularities of distribution of iron-manganese nodules, features of occurrence of ore components in the nodules, nodule abundance in bottom sediments have been studied.

Composition of standard reference samples of Fe-Mn nodules and bottom sediments

The first series of Soviet standard reference samples of composition of ore materials and ocean pelagic sediments has been created. It includes iron-manganese nodules (SDO-4, SDO-5 and SDO-6), ore crusts (SDO-7) diatomaceous ooze (SDO-8), and deep-sea red clays (SDO-9). The standards are intended to serve as a metrologic basis for physical, physicochemical and chemical analyses of iron-manganese minerals and ocean sediments. The standards are provided with certified analyses of rock-forming components and certain trace elements. Certified characteristics are based on statistical analysis of data obtained from an inter-laboratory experiment involving analysis of the standard reference samples by a variety of methods.