The structural and geochemical evolution of the Singhbhum granite batholithic complex, India     

A.K. Saha  S.L. Ray 《Tectonophysics》1984,105(1-4)

The Singhbhum granite batholithic complex of eastern India is composed mainly of (a) the Older Metamorphic Group, tonalite (-trondhjemite) gneiss (OMTG, 3800 Ma old), whch intruded synkinematically into the enveloping Older Metamorphic Group (OMG, > 3800 Ma old) and (b) the Singhbhum granite (SBG) consisting of three distinct but closely related phases of at least twelve separate magmatic units of granodiorite-granite (2950 Ma old), and a number of patches of granitised OMG orthoamphibolites. Geochemical studies including REE and LIL elements suggest that (a) the OMG orthoamphibolites were derived either by re-melting of a K-poor basalt (LKT) or of mantle peridotite with high concentration of LIL elements, (b) the OMG tonalite was derived by partial melting of amphibolite and (c) the Singhbhum granite magmas appear to have formed in two distinct modes: (i) partial melting of amphibolite for the magmas of phases I and II and (ii) partial melting of a siliceous, garnet-bearing granulite for magmas of the phase III units.  相似文献   

An ion microprobe study of the partitioning of trace elements between clinopyroxene and liquid in the system diopside-albite-anorthite     

G.L. Ray  N. Shimizu  S.R. Hart 《Geochimica et cosmochimica acta》1983,47(12):2131-2140

The partitioning of trace elements (Sc, Ti, Sr and Sm) between diopsidic clinopyroxene and liquid was studied experimentally in the system diopside-albite-anorthite at 1250°C, 1300°C and 1345°C at 1 atm. Twelve different bulk compositions were selected to study the effects of temperature and chemical composition. A Cameca ion microprobe was used to determine trace element concentrations in both clinopyroxene and liquid. Experiments of different run duration $\text{1}\text{4}\text{8}\text{?}$ days) showed that equilibrium was approached in less than 4 days at 1275°C. Equilibrium was also evaluated by a reversal run. A series of runs of constant bulk composition but with variable trace element contents showed that Henry's Law was obeyed over concentration ranges of the trace elements similar to those encountered in natural systems. The partition coefficients show significant ranges: Sc, 0.345~2.61; Ti, 0.084~0.214; Sr, 0.075~0.136; Sm, 0.054~0.328; the values are comparable with those obtained experimentally by other investigators. The partition coefficients vary as a function of both temperature and chemical composition. The experimental results are discussed in terms of exchange equilibria using the Bottinga-Weill silicate melt model. It is demonstrated that analytical uncertainties of both major and trace elements play an important role in understanding trace element exchange equilibria; propagation of analytical errors in the thermodynamic treatment is equally important.  相似文献   

SH waves in an inhomogeneous complete or incomplete wedges,I     

S. Ray 《Pure and Applied Geophysics》1971,85(1):161-181

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Cadmium in tissues of lobsters captured near a lead smelter     

S. Ray  D.W. McLeese  L.E. Burridge 《Marine pollution bulletin》1981,12(11):383-386

Cadmium distribution among tissues of lobsters (Homarus americanus) from Belledune Harbour near a lead smelter was determined and compared with that of lobsters from uncontaminated areas of Stonehaven, N.B., Canada and from Maine, USA. The hepatopancreas contained more than 90% of the body burden of cadmium. High concentrations of cadmium were also present in green glands and gills. Cadmium concentrations in the hepatopancreas, gills, and green glands were correlated with the concentrations in most of the other tissues.  相似文献   

IIb trioctahedral chlorite from the Barberton greenstone belt: crystal structure and rock composition constraints with implications to geothermometry   总被引：3，自引：1，他引：3  

Xiaogang Xie  Gary R. Byerly  Ray E. Ferrell Jr. 《Contributions to Mineralogy and Petrology》1997,126(3):275-291

IIb trioctahedral chlorite in the Barberton greenstone belt (BGB) metavolcanic rocks was formed during pervasive greenschist metamorphism. The chem‐ical composition of the chlorite is highly variable, with the Fe/(Fe+Mg) ratio ranging from 0.12 to 0.8 among 53 samples. The chemical variation of the chlorite results from the chemical diversity of the host rock, especially the MgO content of the rock, but major details of the variation pattern of the chlorite are due to the crystal structure of the chlorite. All major cation abundances in the chlorite are strongly correlated with each other. Sil‐icon increases with Mg and decreases with Fe, while Al^IV and Al^VI decrease with Mg and increase with Fe²⁺. A complex exchange vector explains over 90% of the chlorite compositional variation: Mg₄SiFe²⁺ ₋₃Al^VI ₋₁ Al^IV ₋₁, which has 3 parts Fe-Mg substitution coupled with one part tschermakite substitution. This ratio is required to maintain the charge and site balances and the dimensional fit between the tetrahedral and octahedral sheets. The subtle change in Al substitution in chlorite implies that Al^VI is preferentially ordered in the M(4) site, and about 84% of the Al^VI present is in the M(4) sites when they are nearly filled with Al^VI. Based on 47 analyzed chlorite-bearing rock samples, chlorite (Chl) composition is strongly correlated with the MgO content of the host rock. Calculated correlation coefficients are +0.91 for SiO_2Chl-MgO_Rock, −0.87 for Al₂O_3Chl-MgO_Rock, +0.89 for MgO_Chl-MgO_Rock, and −0.85 for FeO_Chl-MgO_Rock. Only weak correlations have been found between chlorite oxides and other oxides of rock (between same oxides in chlorite and rock: SiO₂−0.67, Al₂O₃ + 0.59, FeO −0.41). However, MgO_Chl is saturated at about 36 wt% in rocks that have MgO above 22 wt%.The MgO_Chl is about 5 wt% when the host rock approaches 0 wt% of MgO. This implies that Mg substituting into the chlorite is approximately limited to 1.5–9.2 Mg atoms per formula unit and 1.0–3.2 Al^IV. Chlorite geothermometers can not be applied to all BGB samples. However, the empirical chlorite geothermometer based on Al^IV of chlorite may be applicable to chlorites formed under metamorphic conditions because it can predict the chemical composition of the chlorite from basaltic and dacitic samples in this study. An estimated temperature of about 320°C for the greenschist metamorphism of the greenstone belt through this geothermometer is consistent with that obtained by other geothermometers. Received: 22 January 1996 / Accepted: 15 August 1996  相似文献   

On the habitability of Europa     

Ray T. Reynolds  Steven W. Squyres  David S. Colburn  Christopher P. McKay 《Icarus》1983,56(2):246-254

It has recently been suggested that tidal and radiogenic heating of Europa has led to formation and maintenance of a liquid water ocean overlain by a thin ice crust (S. W. Squyres, R. T. Reynolds, P. M. Cassen, and S. J. Peale (1983). Nature301, 225–226). The present work examines the environmental consequences of such a model with regard to the possible existence on Europa of regions that could satisfy the basic requirements for the survival of known organisms. Appropriate temperatures and long-term environmental stability are implied by the ocean model. The presence of necessary biogenic elements is assumed based on the expected origin of the ocean. The availability of biologically useful energy is assumed to be the principal limiting factor for life on Europa. Possible electrical, thermal, and chemical energy sources are discussed. Calculated resurfacing rates for the active crust model are used to estimate the quantity of photosynthetically active radiation that might reach the proposed ocean through crustal fractures. The amount of biomass that this energy could support, based on Antartic microorganism analogs, is estimated and discussed. Although these calculations cannot determine whether life forms exist or could exist on Europa, they do suggest that there may be regions on Europa, very limited on both space and time, with physical conditions that are within the range of adaptation of life on Earth.  相似文献   

Defining success in fisheries and conflicts in objectives     

Ray Hilborn 《Marine Policy》2007

The traditional fisheries management objectives of maximizing yield and employment lead to heavily exploited stocks. Many current high-profile disputes arise from conflicting objectives, and the proposed solutions to “the fisheries problem” are primarily particular stakeholders’ efforts to have managers implement their own objectives. I suggest many “failures” are in fact successes for other objectives. Fisheries objectives, as reflected in management actions, are changing. Two current trends are the acceptance of objectives that value less disturbed ecosystems and acceptance of fisheries allocation through dedicated access to improve the fisheries’ economic efficiency. I suggest that increased use of dedicated access will result in more congruent objectives and less conflict.  相似文献   

Surface manifestation of internal tides in the deep ocean: observations from altimetry and island gauges   总被引：3，自引：0，他引：3  

Richard D. Ray  Gary T. Mitchum 《Progress in Oceanography》1997,40(1-4)

The sea-surface height signatures of internal tides in the deep ocean, amounting to a few centimeters or less, are studied using two complementary measurement types: satellite altimetry and island tide gauges. Altimetry can detect internal tides that maintain coherence with the astronomical forcing; island gauges can monitor temporal variability which, in some circumstances, is due to internal tides varying in response to changes in the oceanic medium. This latter mechanism is at work at Hilo and other stations on the northern coasts of the Hawaiian Islands. By detecting spatially coherent low-frequency internal-tide modulations, the tide gauges, along with inverted echo sounders at sea, suggest that the mean internal tide is also spatially coherent; satellite altimetry confirms this. At Hawaii and in many other places, Topex/Poseidon altimetry detects mean surface waves, spatially coherent and propagating great distances (> 1000 km) before decaying below background noise. When temporal variability is small, the altimetry (plus information on ocean density) sets useful constraints on energy fluxes into internal tides. At the Hawaiian Ridge, 15 GW of tidal power is being converted from barotropic to first-mode baroclinic motion. Examples elsewhere warn that a simplistic interpretation of the altimetry, without regard to variability, noise, or in situ information, may be highly misleading. With such uncertainties, extension of the Hawaiian results into a usefully realistic estimate of the global internal-tide energy balance appears premature at this time.  相似文献   

On the comparative evolution of Ganymede and Callisto     

Patrick Cassen  Stanton J. Peale  Ray T. Reynolds 《Icarus》1980,41(2):232-239

Differences in the apparent ages of the surfaces of Ganymede and Callisto, as revealed by Voyager images, could be due to the persistence of tectonic activity on Ganymede beyond the time of early, heavy bombardment. The slightly greater radioactive content expected in Ganymede could prolong such activity by as much as 0.5 billion years beyond the cessation of endogenic surface activity on Callisto. Tidal dissipation could not have been important for Ganymede for more than 10⁸ years, and it was never important for Callisto.  相似文献   

Internal stratigraphic architecture of the komatiitic dunite-hosted MKD5 disseminated nickel sulfide deposit,Mount Keith Domain,Agnew-Wiluna Greenstone Belt,Western Australia     

N. M. Rosengren  B. A. Grguric  S. W. Beresford  M. L. Fiorentini  R. A. F. Cas 《Mineralium Deposita》2007,42(8):821-845

The MKD5 nickel deposit is hosted by the Mount Keith Ultramafic Complex (MKUC), a dunite body of komatiitic affinity located in the Agnew-Wiluna Greenstone Belt, Western Australia. The internal architecture of the MKUC comprises seven distinct internal units that range from extreme adcumulate dunite to relatively fractionated pyroxenitic and gabbroic horizons. The MKUC is divided into three packages of units. The main adcumulate domain (MAD), which is situated in the lower portion of the complex, contains the bulk of disseminated nickel sulfide and is dominated by coarse adcumulate olivine textures. Overlying the MAD is an upper fractionated zone, which is dominated by mesocumulate-to-orthocumulate peridotite with domains containing oikocrystic pyroxenite and gabbroic lenses. An aerially restricted unit comprising texturally and chemically distinct olivine cumulate rocks is known as the western mineralized zone (WMZ). The fractionation trend between the MAD and UPZ indicates a westerly facing for the MKUC, conformable with the bounding stratigraphy. In the MKUC, truncation of some of the uppermost internal stratigraphic units by the hangingwall contact indicates that the unit has undergone structural modification since its emplacement and suggests that a proportion of the upper section has been removed by faulting. Furthermore, vertical and lateral textural transitions within the internal stratigraphy suggest that the MKUC (excluding the WMZ) was emplaced from an essentially continuous magma flow, with the MAD representing the period of highest magma flux and the major constructional period of emplacement. Conversely, the WMZ is interpreted to represent a later pulse of ultramafic magma, emplaced stratigraphically above the main MKUC. Comparison of the MKUC with other komatiitic dunites from both within the Agnew-Wiluna Greenstone Belt and worldwide indicates that despite apparent geometrical differences between lens and sheet komatiitic dunites, a broad facies architecture can be defined. We suggest that the differences in geometry are related to differing degrees of flow localization within dunitic units and are a function of both differences in the thermal characteristics and the degree of litho-facies heterogeneity of the enclosing lithologies.  相似文献