Element abundances, loss on ignition, total analyzed abundances, CIA values, and Al-oxide/Ti-oxide ratios of sediment core CRP-2A (Table1)

The CRP-2/2A core, drilled in western McMurdo Sound in October and November 1998, penetrated 624 m of Quaternary. Pliocene, lower Miocene, and Oligocene glacigenic sediments. The palaeoclimatic record of CRP-2/2A is examined using major element analyses of bulk core samples of fine grained sediments (mudstones and siltstones) and the Chemical Index of Alteration (CIA) of Nesbitt & Young (1982). The CIA is calculated from the relative abundances of AI, K, Ca, and Na oxides, and its magnitude increases as the effects of chemical weathering increase. However, changes in sediment provenance can also affect the CIA, and provenance changes are recorded by shifts in the Al2O3/TiO2 ratios and the Nb contents of these CRP-2/2A mudstones. Relatively low CIA values (40-50) occur throughout the CRP-2/2A sequence, whereas the Al2O3/TiO2 ratio decreases upsection. The major provenance change is an abrupt onset of McMurdo Volcanic Group detritus at ~300 mbsf and is best characterized by a rapid increase in Nb content in the sediments. This provenance shift is not evident in the CIA record, suggesting that a contribution from the Ferrar Dolerite to the older sediments was replaced by an input of McMurdo Volcanic Group material in the younger sediments. If this is true, then the relatively uniform CIA values indicate relatively consistent palaeoweathering intensities throughout the Oligocene and early Miocene in the areas that supplied sediment to CRP-2/2A.

(Table 1) Determined and theoretical chemical composition of thaumasite of ODP Hole 135-841B

Hole 841B was drilled in the forearc region of the Lau Basin at a water depth of 4810 m. The hole penetrated a roughly 500-m-thick series of Miocene volcanic sediments with a number of basaltic to andesitic units (sills?) varying in thickness between 7 cm and 17 m. The volcanics are slightly to moderately altered and contain analcite, chabazite, natrolite-thompsonite, heulandite (?), prehnite, and quartz as secondary phases. In addition, thaumasite [Ca3Si(OH)6 * 12H2O](SO4)(CO3) was identified in the altered sequence. Sulfur isotope data of two thaumasite separates (+23.5 per mil and +21.1 per mil d34S) indicate a seawater origin of the sulfate sulfur. It is suggested that thaumasite is a product of low-temperature (<60 °C), seawater-derived CaCl2-rich fluids that were almost identical in composition to those presently circulating in the sub-seafloor.

Tab. 2: Geochemical composition of metasomatites and parent rocks from the Polar Urals

Rare-metal alkali (quartz-feldspathic) metasomatites are considered in terms of their geologic position, structure, and composition. Their petrochemical and geochemical characteristics are given. In the Polar Urals, the metasomatites occur as lenticular and tube-like bodies in the fault zones of the Cambrian basement within the Kharbey block. Three types of the metasomatites, dated at ~300 Ma, have been recognised: quartz-bifeldspathic (kvalmites), quarzt-albitic, and albitites. They belong to the formation of quartz-feldspathic metasomatites of the fault zones.

(Table 2, Page 275) Elemental concentrations in manganese nodules used in seawater contact experiments

The gross changes in concentrations of several trace elements in seawater after contact with ferro-manganese particle suspensions has been determined. Cobalt, Fe, and Zn concentrations in the seawater were greatly increased after contact with the par¬ticles. The concentrations of Rb, U, Cs, Sb, and Ag were altered to a lesser degree by this treatment. Similar results were observed where seawater was con¬tacted with suspensions of pelagic sediments. Of the trace elements measured, cobalt and iron appear to be the best elemental indicators of the presence of manganese mining effluents in the ocean. The addi¬tions of the essential elements Co, Fe and Zn toge¬ther with nutrients from the bottom waters may pro¬duce increased biological productivity. However, the toxic trace metals, such as Hg, Cu and Cd which could enter ocean water from the nodules and sedi¬ment and which may be high in effluent-affected areas should be investigated before conclusions as to the likely impact can be reached. Trace element analysis of seawater samples collected at a Pacific Ocean manganese nodule dredging site showed high t race element concentrations, but these are believed to have resulted from contamination during sample collection or storage rather than from the dredging operations.

San Francisco Coastal System grain size and geochemical data for sand provenance study

Over 150 million cubic meter of sand-sized sediment has disappeared from the central region of the San Francisco Bay Coastal System during the last half century. This enormous loss may reflect numerous anthropogenic influences, such as watershed damming, bay-fill development, aggregate mining, and dredging. The reduction in Bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches, wetlands, and submarine environments. A unique, multi-faceted provenance study was performed to definitively establish the primary sources, sinks, and transport pathways of beach sized-sand in the region, thereby identifying the activities and processes that directly limit supply to the outer coast. This integrative program is based on comprehensive surficial sediment sampling of the San Francisco Bay Coastal System, including the seabed, Bay floor, area beaches, adjacent rock units, and major drainages. Analyses of sample morphometrics and biological composition (e.g., Foraminifera) were then integrated with a suite of tracers including 87Sr/86Sr and 143Nd/144Nd isotopes, rare earth elements, semi-quantitative X-ray diffraction mineralogy, and heavy minerals, and with process-based numerical modeling, in situ current measurements, and bedform asymmetry to robustly determine the provenance of beach-sized sand in the region.

Geochemical composition of sulfide and oxide minerals from ODP Sites 193-1188 and 193-1189, PACMANUS field

Ocean Drilling Program (ODP) Leg 193 recovered core from the active PACMANUS hydrothermal field (eastern Manus Basin, Papua New Guinea) that provided an excellent opportunity to study mineralization related to a seafloor hydrothermal system hosted by felsic volcanic rocks. The purpose of this work is to provide a data set of mineral chemistry of the sulfide-oxide mineralization and associated gold occurrence in samples drilled at Sites 1188 and 1189. PACMANUS consists of five active vent sites, namely Rogers Ruins, Roman Ruins, Satanic Mills, Tsukushi, and Snowcap. In this work two sites were studied: Snowcap and Roman Ruins. Snowcap is situated in a water depth of 1670 meters below sea level [mbsl], covers a knoll of dacite-rhyodacite lava, and is characterized by low-temperature diffuse venting. Roman Ruin lies in a water depth of 1693-1710 mbsl, is 150 m across, and contains numerous large, active and inactive, columnar chimneys. Sulfide mineralogy at the Roman Ruins site is dominated by pyrite with lesser amounts of chalcopyrite, sphalerite, pyrrhotite, marcasite, and galena. Sulfide minerals are relatively rare at Snow Cap. These are dominated by pyrite with minor chalcopyrite and sphalerite and traces of pyrrhotite. Native gold has been found in a single sample from Hole 1189B (Roman Ruins). Oxide minerals are represented by Ti magnetite, magnetite, ilmenite, hercynite (Fe spinel), and less abundant Al-Mg rich chromite (average = 10.6 wt% Al2O3 and 5.8 wt% MgO), Fe-Ti oxides, and a single occurrence of pyrophanite (Mn Ti O3). Oxide mineralization is more developed at Snowcap, whereas sulfide minerals are more extensive and show better development at Roman Ruins. The mineralogy was obtained mainly by a detailed optical microscopy study. Oxide mineral identifications were confirmed by X-ray diffraction, and mineral chemistry was determined by electron probe microanalyses.

Chemical composition of nodules from two locations in the Pacific Ocean using different methods

Manganese nodules recovered in the Pacific Ocean by the U. S. Bureau of Mines and by DeepSea Ventures Ltd. are studied for their chemical composition using X microprobe and X-ray fluorescence methods.