Trace element mobility during hydrothermal alteration of oceanic basalts   总被引：2，自引：0，他引：2  

Susan E. Humphris  Geoffrey Thompson 《Geochimica et cosmochimica acta》1978,42(1):127-136

Trace element analyses have been carried out on hydrothermally altered pillow basalts of greenschist facies dredged from the median valley of the Mid-Atlantic Ridge. Sr is leached from the rock, and its behavior is apparently controlled by the same reactions as Ca. Cu is also leached from the basalt, but often shows local precipitation in veins as sulfides. Fe, B, Li, Ba, Mn, Ni and Co show sufficient variations in concentration and location within the altered basalts to indicate that some mobilisation occurs, but there may be subsequent uptake or precipitation into the secondary mineral assemblages. V, Y, Zr and Cr do not appear to be affected by hydrothermal alteration.The production of a metal-enriched solution by hydrothermal alteration and subsequent precipitation of metal salts to form metalliferous sediments is indicated, as is precipitation of metal sulfides in the basaltic basement.  相似文献   

Temporal variability of microparticle properties in polar ice sheets     

L. G. Thompson  E. Mosley-Thompson 《Journal of Volcanology and Geothermal Research》1981,11(1):11-27

Four recent ice core studies reveal a consistently recurring temporal correlation between increased microparticle concentrations and lower global temperatures (more negative ¹³O/¹⁶O ratios). A continuous 900-year record of particle deposition from the 101-m South Pole core was obtained by analyzing 6218 samples. The concentration of insoluble particles with diameters >0.63 μm increases substantially between A.D. 1450 and 1850, a period of slightly reduced global temperatures encompassing the latest Neoglacial or Little Ice Age. There is evidence suggesting that some of the additional material may be volcanic, although further substantiation is required.The microparticle analyses of selected sections from three deep cores coupled with the respective σ¹⁸O measurements reveal that in all three cores the last glacial or Late Wisconsin ice contained great quantities of microparticles. The ratio of the average microparticle concentration in Wisconsin sections to that in Holocene sections is 6 for the 905-m Dome C, Antarctica core, 3 for the 2164-m Byrd Station, Antarctica core and 12 for the 1387-m Camp Century, Greenland core. Microparticle increases of this magnitude can not be accounted for merely by a reduction in net accumulation. These data suggest that the global atmosphere was heavily laden with suspended particulates near the end of the last major glaciation.  相似文献   

Toxicity testing of oil slick dispersants in Hong Kong     

G.B. Thompson  R.S.S. Wu 《Marine pollution bulletin》1981,12(7):233-237

In Hong Kong, the toxicity of oil spill dispersants was assessed in a preliminary screening test, based upon TD₅₀ values in samples of ten fish. Later, an improved test was introduced, based upon new procedures developed in the United Kingdom and modified to suit conditions in Hong Kong. Products approved elsewhere were usually, but not always, approved in Hong Kong. Further work is needed to relate the test results to oil-spill damage in local waters.  相似文献   

Primary basalts and magma genesis     

R. N. Thompson 《Contributions to Mineralogy and Petrology》1977,60(1):91-108

A representative Quaternary clinopyroxene leucitite lava from the Alban Hills, Roman comagmatic province, central Italy, has been subjected to anhydrous thermal experiments within its melting range at pressures up to 45 kb. The lava contains 2.2% of leucite and 1.4% of diopside phenocrysts in a fine-grained groundmass, suggesting that these phases were crystallizing on the liquidus of the magma immediately prior to its eruption. This situation is reproduced experimentally at 14 kb and 1260 °C. As there is no evidence that the H₂O content of this lava was appreciable, it is concluded that the anhydrous experimental results give a valid indication that this leucitite equilibrated with its phenocrysts at approximately 50 km depth, about 25 km into the upper mantle, before final rapid uprise. Comparison of the bulk compositions of Alban Hills mafic leucitites with that of the eutectic in the synthetic system Diopside-Leucite as a function of pressure confirms the conclusion of the high-pressure experiments. In contrast, the dilc ratios of other Roman province mafic leucitites indicate that they equilibrated within the upper crust prior to eruption. Published Sr and O-isotope studies show unequivocally that, when the Alban Hills mafic leucitites and their phenocrysts equilibrated, the magmas contained a substantial fraction of melt from crustal rocks. These data are reconciled with the experimental demonstration that the magmas evolved entirely within the upper mantle by postulating that their crustal components were derived from partial fusion of Tyrrhenian ocean-floor sediments, subducted beneath Italy during the anticlockwise rotation of the Corsica-Sardinia lithospheric microplate. The Roman province volcanics show considerable chemical similarities with lavas from converging plate margins elsewhere, together with substantial differences from other occurrences of strongly-potassic rocks. It is concluded that this magma type may be polygenetic.  相似文献   

Tritium-Verteilung,Durchmischungsverhältnisse und Altersstruktur der Wassermasse im Vierwaldstättersee     

Frau Dr. M. M. Bezzegh  Prof. Dr. H. L. Le Roy  K. Steiner 《Aquatic Sciences - Research Across Boundaries》1977,39(2):201-225

Tritium of thermonuclear origin was measured in four different depth profiles in the Lake of Lucerne. Its concentration distribution yielded information on the mixing within the water mass under observation. A simple model was established for approximating the age structure of the water layers.  相似文献   

Refractory megacrysts and magnesium-rich melt inclusions within spinel in oceanic tholeiites: Indicators of magma mixing and parental magma composition     

Colin H. Donaldson  Roy W. Brown 《Earth and Planetary Science Letters》1977,37(1):81-89

Refractory megacrysts of olivine, plagioclase, chromian diopside and Cr-Al spinel, which were not in equilibrium with the host oceanic tholeiite on eruption, are present in samples from several dredge sites and DSDP drill sites in the Atlantic and Pacific Oceans. They have multiple origins: (1) cognate or accidental mantle fragments; (2) relict fragments from fractional crystallization of parental liquids considerably more primitive than oceanic tholeiite; and most commonly (3) the fractional crystallization products of such liquids mixed with oceanic tholeiite magma. Melt inclusions in chrome-spinel phenocrysts provide evidence for this postulated Mg- and Ca-rich magma which has counterparts in the Scottish Tertiary Province and in west Greenland.  相似文献   

Kinetics and mechanism of the epimerization and decomposition of threonine in fossil foraminifera     

Roy A. Schroeder  Jeffrey L. Bada 《Geochimica et cosmochimica acta》1977,41(8):1087-1095

Determination of alloThr/Thr ratios in foraminiferal tests ranging in age from Recent to ～ 700,000 yr B.P. has shown that threonine epimerization ratios approach a steady-state value of ～0.2. This is well below the equilibrium ratio of ～0.9 as measured in buffered aqueous solutions. It has also been found that the initial rate of decomposition of threonine in fossil foraminfera is about an order of magnitude faster than would be predicted on the basis of extrapolation from high temperature kinetic studies on free threonine in buffered aqueous solution. These results are apparently a consequence of metal cation catalysis of both the decomposition and the epimerization of free threonine, which is being continually released by the slow hydrolysis of peptide and proteinaceous material present in the fossil shells.  相似文献   

Geochemistry and petrology of dredged basalts from the Bouvet triple junction,South Atlantic     

John S. Dickey  Frederick A. Frey  Stanley R. Hart  E.Bruce Watson  Geoffrey Thompson 《Geochimica et cosmochimica acta》1977,41(8):1105-1118

Basalts dredged from the Bouvet triple junction (South Atlantic), from the Mid-Atlantic Ridge near the triple junction, and from a spreading center east of Bouvet Island differ from normal mid-ocean ridge tholeiites by having higher concentrations of K and other large-ion-lithophile elements, higher ${}^{87}\text{Sr}\text{:}{}^{86}\text{Sr}$ ratios, and rare earth element distributions which show relative enrichment in the lighter rare earths. The basalts are more fractionated than typical oceanic tholeiites, however, fractional crystallization does not fully account for their chemical characteristics, and it appears that they were derived from special source materials, contaminated perhaps by a mantle plume rising beneath Bouvet Island.  相似文献   

Ground-Water Tracers — A Short Review     

Stanley N. Davis  Glenn M. Thompson  Harold W. Bentley  Gary Stiles 《Ground water》1980,18(1):14-23

  相似文献   

Seasonal growth in the bivalveMacoma balthica near the southern limit of its range     

Frederic H. Nichols  Janet K. Thompson 《Estuaries and Coasts》1982,5(2):110-120

Shell-length growth inMacoma balthica from San Francisco Bay, California, as measured on living animalsin situ, is highly seasonal despite a mild Mediterranean climate: a long period of near non-growth from May to the following February is followed by a short period of rapid growth between March and May. The rapid-growth period follows the spawning period during January/February and ends as water temperature rises above about 15°C. Despite the shortness of the growth period,M. balthica grows larger at a given age in San Francisco Bay than is recorded elsewhere in the world. Application of a model, developed elsewhere from these same field measurements, shows that (1) measurable growth occurs during the summer/autumn/early winter “nongrowth” period, (2) there is an autumn recruitment, and (3) both spring and autumn recruits combine to form a single “one-year-old” size grouping. None of these features is detectable through growth-ring analysis of field samples, apparently because of indistinct climatic seasons, or through size-frequency histogram analysis because of the combined effects of slow growth and intermittent recruitment.  相似文献