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31.
A.H.F. Robertson 《Earth and Planetary Science Letters》1978,41(3):317-329
The Arakapas fault belt, southern Troodos Massif, which is interpreted as a fossil oceanic fracture zone, contains a sedimentary and volcanic “fill” including basaltic lava breccias, volcaniclastic sandstones, intercalated Fe-rich mudstones, and minor Cu sulphide mineralisation. The volcaniclastic sedimentary rocks were produced by submarine weathering and gravity redeposition of basalt within the transform zone. In contrast, the Fe-mudstones predominantly originated as chemical precipitates from hydrothermal solutions generated by hydrothermal leaching of basalt by seawater. The rare earth elements, and some trace metals, including Co, Ni, Pb, V and Zr, are thought to have been incorporated from seawater into the ferruginous precipitates. Unusually high Fe/Mn ratios of the Fe-mudstones relative to most modern ocean-ridge sediments may reflect deposition in relatively oxygen-depleted waters on the floor of a major bathymetric depression created by the transform faulting; release of acidic thermal waters would have further suppressed Mn precipitation. Contrary to recent suggestions of metallogenesis along oceanic fracture zones, none of the major Cyprus cupriferous sulphide bodies lie along the fossil Arakapas transform zone. 相似文献
32.
Spectroscopy of thez=2.0763 absorption line system in A2206-199N shows that it has a very large hydrogen column density (5×1020 cm–2) but extremely weak absorption due to heavy elements. We discuss the possibility that the gas cloud causing this absorption system may be exceptionally metal-poor.Paper presented at the IAU Thrid Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
33.
Survey and Geographic Information System (GIS) data analysis describes the relative influence of biophysical and human variables on site choices made by marine farmers in New Zealand. Community conflicts have grown in importance in determining farm location and different government planning strategies leave distinct signature patterns. Recent legislation empowers local governments to choose among three strategies for future regional aquaculture development. This paper suggests each strategy could result in different spatial outcomes. Simulation modelling of the type described here can provide a better understanding of farmer responses to management approaches and the range of futures that could result from planning choices made today. 相似文献
34.
A.H.F. Robertson 《地学学报》1990,2(4):333-339
In northern Euboea (Eastern Greece), Late Cretaceous platform carbonates of the Pelagonian Zone pass depositionally upwards into Maastrichtian hemipelagic limestones, possibly reflecting a rifting event in the adjacent Neotethys. This is followed by a c. 1 km-thick unit of siliciclastic turbidites, debris flows and detached limestone blocks. Thrust intercalations of ophiolitic rocks comprise altered pillow basalts and ultramafic rocks with ophicalcite. Calcite veins in sheared serpentinite contain planktonic foraminifera and the ophicalcite is directly overlain, with a depositional contact, by Globotruncana-bearing pelagic limestones and calciturbidites of Maastrichtian age. The ophiolitic rocks are interpreted as Late Cretaceous oceanic crust and mantle, that formed at a fracture zone, or rifted spreading axis within a Neotethyan, Vardar basin to the east. During the Early Tertiary (Palaeocene–Eocene), the Neotethyan basin began to close, with development of a subduction-accretion complex, mainly comprising sheared, trench-type sandstones, associated with ophiolitic slices. In response to trench/margin collision, the Pelagonian carbonate platform foundered and limestone debris flows and olistoliths were shed into a siliciclastic foreland basin. Suturing of the Neotethyan ocean basin then resulted in westwards thrusting of oceanic units over the foreland basin, thrusting of slices of inferred Late Cretaceous Pelagonian carbonate platform slope and large-scale recumbent folding. 相似文献
35.
Sgubin Giovanni Swingedouw Didier Drijfhout Sybren Hagemann Stefan Robertson Eddy 《Climate Dynamics》2015,45(5-6):1429-1450
Climate Dynamics - The response of the Atlantic meridional overturning circulation (AMOC) to an increase of radiative forcing (ramp-up) and a subsequent reversal of radiative forcing (ramp-down) is... 相似文献
36.
D.A. Robertson 《新西兰海洋与淡水研究杂志》2013,47(2):129-136
Frostfish spawning, as indicated by the presence of planktonic eggs, was observed mainly in north‐eastern, but also in south‐western, New Zealand waters in spring to autumn. Spawning takes place in the afternoon in outer shelf waters 50–200 m deep, with surface temperatures and salinities between 17.5 and 22.0°C and 35.3 and 35.6‰ respectively. Egg and oil droplet diameters ranged from 1.65 to 1.75 mm and 0.40 to 0.43 mm respectively. 相似文献
37.
A drift and pumpback experiment was conducted in a brackish water sandfill. The sandfill was reclaimed from the sea in the eastern part of Singapore and contains sands with low organic and clay/silt contents. The high salinity in the ground water precludes the use of chloride and bromide as tracers in such an environment, and a field experiment was conducted to assess the viability of using fluorescein as a tracer in brackish water aquifers. Nitrate was used as a second tracer to serve as a check. Initial laboratory studies showed that fluorescence was unaffected over the range of electrical conductivity and pH of the ground water. Results from the field experiment show that fluorescein appears to behave conservatively. 相似文献
38.
Morgan Robertson 《Geoforum》2010,41(1):7-10
This essay reflects on issues of researcher positionality within participant observation and action research, and the specific methodological issues surrounding research on neoliberal governance strategies, using my experience at the US Environmental Protection Agency as case material. Although I was initially concerned about participating with the anti-progressive Bush Administration, I attempted to adopt the interests and subjectivity of an environmental bureaucrat. Doing so proved to be an extremely effective way of exploring the multi-vocality and cross-cutting interests constituting the state, which often appears from the outside to be a policy monolith. Participant research among elites in the neoliberal state is an effective way to observe such complexity. It became apparent that, because mainstream economics tends to adopt a totalizing epistemology, both its casual and dogmatic adherents usually do not conceive of a coherent external critique. This often means that researchers of any theoretical background can be quite frank concerning their purposes, background, and interests, even as participants. 相似文献
39.
Fiona?V.?FoleyEmail author Simon?Turner Tracy?Rushmer John?T.?Caulfield Nathan?R.?Daczko Paul?Bierman Matthew?Robertson Craig?D.?Barrie Adrian?J.?Boyce 《Contributions to Mineralogy and Petrology》2014,168(3):1048
Subduction-related Quaternary volcanic rocks from Solander and Little Solander Islands, south of mainland New Zealand, are porphyritic trachyandesites and andesites (58.20–62.19 wt% SiO2) with phenocrysts of amphibole, plagioclase and biotite. The Solander and Little Solander rocks are incompatible element enriched (e.g. Sr ~931–2,270 ppm, Ba ~619–798 ppm, Th ~8.7–21.4 ppm and La ~24.3–97.2 ppm) with MORB-like Sr and Nd isotopic signatures. Isotopically similar quench-textured enclaves reflect mixing with intermediate (basaltic-andesite) magmas. The Solander rocks have geochemical affinities with adakites (e.g. high Sr/Y and low Y), whose origin is often attributed to partial melting of subducted oceanic crust. Solander sits on isotopically distinct continental crust, thus excluding partial melting of the lower crust in the genesis of the magmas. Furthermore, the incompatible element enrichments of the Solander rocks are inconsistent with partial melting of newly underplated mafic lower crust; reproduction of their major element compositions would require unrealistically high degrees of partial melting. A similar argument precludes partial melting of the subducting oceanic crust and the inability to match the observed trace element patterns in the presence of residual garnet or plagioclase. Alternatively, an enriched end member of depleted MORB mantle source is inferred from Sr, Nd and Pb isotopic compositions, trace element enrichments and εHf ? 0 CHUR in detrital zircons, sourced from the volcanics. 10Be and Sr, Nd and Pb isotopic systematics are inconsistent with significant sediment involvement in the source region. The trace element enrichments and MORB-like Sr and Nd isotopic characteristics of the Solander rocks require a strong fractionation mechanism to impart the high incompatible element concentrations and subduction-related (e.g. high LILE/HFSE) geochemical signatures of the Solander magmas. Trace element modelling shows that this can be achieved by very low degrees of melting of a peridotitic source enriched by the addition of a slab-derived melt. Subsequent open-system fractionation, involving a key role for mafic magma recharge, resulted in the evolved andesitic adakites. 相似文献
40.