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S. J. RILEY 《水文科学杂志》2013,58(4):365-381
Abstract The large quantities of sediment eroded from the Sydney F3 Expressway extension and the lack of defined channels within the catchment presented several problems of discharge and sediment load sampling. The monitoring equipment at the catchment outlet, namely pump samplers and capacitance-based water level sensors, was computer controlled, but for partial area monitoring manual methods were used together with Gerlach traps and erosion pins. The monitoring at the catchment outlet was cost-effective because of the use of electronic equipment. The sampling strategies are described and recommendations for future sampling programs are presented. Coarse sand and silt-clay concentrations in many samples were more than 10 g 1?1 at the outlet. In some samples the silt-clay concentrations exceeded 30 g 1?1 and the coarse sand concentrations 100 g 1?1. 相似文献
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Episodic Silicic Volcanism in Patagonia and the Antarctic Peninsula: Chronology of Magmatism Associated with the Break-up of Gondwana 总被引:10,自引:2,他引:8
New SHRIMP UPb zircon, RbSr whole-rock, and 40Ar39Ardata are presented for the Jurassic silicic volcanic rocks andrelated granitoids of Patagonia and the Antarctic Peninsula.UPb is the only reliable method for dating crystallizationin these rocks; RbSr is prone to hydrothermal resettingand ArAr is additionally affected by initial excess 40Ar.Volcanism spanned more than 30 My, but three episodes are definedon the basis of peak activity: V1 (188178 Ma), V2 (172162Ma) and V3 (157153 Ma). The first essentially coincideswith the KarooFerrar mafic magmatism of South Africa,Antarctica and Tasmania. The silicic products of V1 are lower-crustalmelts that have incorporated upper-crustal material. The geochemistryof V2 and V3 ignimbrites is more characteristic of destructiveplate margins, but the presence of inherited zircon still pointsto a crustal source. The pattern of volcanism corresponds inspace and in time to migration away from the Karoo mantle plumetowards the proto-Pacific margin of Gondwana during riftingand break-up. The heat required to initiate bulk crustal fusionmay have been supplied by the spreading plume-head, but thinningof the crust during continental dispersion would also have facilitatedanatexis. KEY WORDS: Antarctic Peninsula; ignimbrites; Jurassic; Patagonia; UPb; zircon 相似文献
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S. J. RILEY 《水文科学杂志》2013,58(4):545-560
Abstract The bankfull cross-sectional geometry of a stream may be described by 18 variables, each of which significantly discriminates among stream sites. These variables may be reduced to four significant factors: (1) an index of channel capacity and efficiency, (2) an index of cross-sectional shape and mode of energy expenditure, (3) an index of bottom width and sediment load, and (4) an index of profile roughness. The four factors explain 84 per cent of the correlation matrix variance. 相似文献
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Origins of Large Volume Rhyolitic Volcanism in the Antarctic Peninsula and Patagonia by Crustal Melting 总被引:10,自引:1,他引:10
RILEY TEAL R.; LEAT PHILIP T.; PANKHURST ROBERT J.; HARRIS CHRIS 《Journal of Petrology》2001,42(6):1043-1065
Voluminous rhyolitic volcanism along the palaeo-Pacific marginof Gondwana was marked by three principal episodes of magmatism.The first of these ( V1) is essentially coincident with themain episode of KarooFerrar magmatism at 相似文献
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The optimum parameters of tuned mass dampers (TMD) that result in considerable reduction in the response of structures to seismic loading are presented. The criterion used to obtain the optimum parameters is to select, for a given mass ratio, the frequency (tuning) and damping ratios that would result in equal and large modal damping in the first two modes of vibration. The parameters are used to compute the response of several single and multi-degree-of-freedom structures with TMDs to different earthquake excitations. The results indicate that the use of the proposed parameters reduces the displacement and acceleration responses significantly. The method can also be used in vibration control of tall buildings using the so-called ‘mega-substructure configuration’, where substructures serve as vibration absorbers for the main structure. It is shown that by selecting the optimum TMD parameters as proposed in this paper, significant reduction in the response of tall buildings can be achieved. © 1997 John Wiley & Sons, Ltd. 相似文献
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Nine Namurian clay bands retrieved from boreholes in the northern part of the Pennine Basin are, on the basis of their petrography, mineralogy and geochemistry, shown to be volcanic in origin and are therefore bentonites. The bentonites, which have a fragmental texture, are normally graded and show rare preservation of shard textures, representing vitric tuff deposits that have been altered subsequently to clay-dominated horizons. Crystals are a minor component of the bentonites, but biotite, in particular, is concentrated at the base of the beds. A clay mineral assemblage of mixed-layer illite–smectite with subordinate kaolinite identifies most of the samples as K-bentonites, but kaolinite dominates two samples that can be classed as tonsteins. Temporal variation of salinity within the depositional basin is suggested to explain these different clay assemblages. The major element geochemistry of the bentonites reflects their clay mineralogy and the compositions of diagenetic minerals present, the latter including pyrite, carbonates and hydroxyapatite. Enrichment of the bentonites in some trace elements (including Ba, Sr, Pb, Cu and Ni) can be related to the presence of the diagenetic minerals, but the extent to which the elements are added from external sources as opposed to being redistributed within the ash is unclear. Immobile trace element systematics suggest a rhyodacite/dacite composition for the original ash and derivation from the collision of plates, this being supported by evidence provided by the rare earth elements (REE) in one group of samples. However, in another group of samples, variations in REE concentrations may be caused by mobility of these elements during alteration. The chemistry of the Namurian bentonites contrasts markedly with that of the local Carboniferous volcanics but is comparable, in some respects, with one group of Westphalian tonsteins, although the latter are more rhyolitic in character. It is suggested that the Namurian bentonites and the Westphalian tonsteins of acid affinities originated from volcanic activity associated with a destructive plate margin in the Variscan externides and that the observed compositional trend may reflect magma evolution possibly related to the progressive east–west closure. 相似文献
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RILEY T. R.; CURTIS M. L.; LEAT P. T.; WATKEYS M. K.; DUNCAN R. A.; MILLAR I. L.; OWENS W. H. 《Journal of Petrology》2006,47(3):541-566
A suite of mafic dykes from the Underberg region of southernKwaZulu-Natal (South Africa) were intruded at 178 Ma, coincidentin age with the major Okavango Dyke Swarm of Botswana, and alsocoincident with minor Karoo-related intrusions of the northernand central Lebombo. The dykes are all low-TiZr tholeiites,they trend NWSE and are presumed to continue into theKaroo central area of the Lesotho Highlands. In many respects,the Underberg dykes are similar to the majority of the low-TiZrvolcanic and subvolcanic intrusions of the Karoo; however, their87Sr/86Sr and Nd isotope ratios are either Ferrar-like(87Sr/86Sr 0·710; Nd < 3) or transitional betweenKaroo low-TiZr and Ferrar low-Ti magmas. A potentialFerrar source for at least some of the Underberg dykes is supportedby anisotropy of magnetic susceptibility analyses of the dykesuite, which demonstrate absolute flow direction from the SEto the NW, consistent with Gondwana reconstructions. The roleof crustal contamination and combined fractional crystallizationis also demonstrated to have played a key role in the petrogenesisof the Underberg dykes, involving a local upper crust contaminant.However, the composition of the Ferrar-like dykescannot be easily explained by AFC processes, but they do demonstratethat melting of a lithospheric mantle source enriched to a smalldegree by subduction-derived fluid was also important. KEY WORDS: dyke; basalt; crustal contamination; large igneous province 相似文献
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RILEY TEAL R.; LEAT PHILIP T.; CURTIS MICHAEL L.; MILLAR IAN. L.; DUNCAN ROBERT A.; FAZEL ADELA 《Journal of Petrology》2005,46(7):1489-1524
A suite of dolerite dykes from the Ahlmannryggen region of westernDronning Maud Land (Antarctica) forms part of the much moreextensive Karoo igneous province of southern Africa. The dykecompositions include both low- and high-Ti magma types, includingpicrites and ferropicrites. New 40Ar/39Ar age determinationsfor the Ahlmannryggen intrusions indicate two ages of emplacementat 178 and 190 Ma. Four geochemical groups of dykes have beenidentified in the Ahlmannryggen region based on analyses of60 dykes. The groups are defined on the basis of whole-rockTiO2 and Zr contents, and reinforced by rare earth element (REE),87Sr/86Sr and 143Nd/144Nd isotope data. Group 1 were intrudedat 190 Ma and have low TiO2 and Zr contents and a significantArchaean crustal component, but also evidence of hydrothermalalteration. Group 2 dykes were intruded at 178 Ma; they havelow to moderate TiO2 and Zr contents and are interpreted tobe the result of mixing of melts derived from an isotopicallydepleted source with small melt fractions of an enriched lithosphericmantle source. Group 3 dyke were intruded at 190 Ma and formthe most distinct magma group; these are largely picritic withsuperficially mid-ocean ridge basalt (MORB)-like chemistry (flatREE patterns, 87Sr/86Sri 0·7035, Ndi 9). However, theyhave very high TiO2 (4 wt %) and Zr (500 ppm) contents, whichis not consistent with melting of MORB-source mantle. The Group3 magmas are inferred to be derived by partial melting of astrongly depleted mantle source in the garnet stability field.This group includes several high MgFe dykes (ferropicrites),which are interpreted as high-temperature melts. Some Group3 dykes also show evidence of contamination by continental crust.Group 4 dykes are low-K picrites intruded at 178 Ma; they havevery high TiO2Zr contents and are the most enriched magmagroup of the KarooAntarctic province, with ocean-islandbasalt (OIB)-like chemistry. Dykes of Group 1 and Group 3 aresub-parallel (ENEWSW) and both groups were emplaced at190 Ma in response to the same regional stress field, whichhad changed by 178 Ma, when Group 2 and Group 4 dykes were intrudedalong a dominantly NNESSW strike. KEY WORDS: flood basalt; depleted mantle; enriched mantle; Ahlmannryggen; Karoo dyke 相似文献
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