On mass transport in deep water waves

Summary Various formulations of the mass-transport problem are compared for progressive waves in deep water. In order to calculate the mass-transport velocity as a function of depth in the main body of the fluid, it is necessary to include the effect of viscous wave attenuation. It is shown that the usual assumptions of periodicity in distance and attenuation with time or periodicity in time and attenuation with distance, are both physically unsatisfactory. The first does not specify a unique solution, and the second is incompatible with the assumption of zero surface stress. A certain critical constant tangential wind stress will maintain strictly time-periodic deep water waves. The corresponding attenuation with distance is then calculated to order ³. A constant tangential stress greater or less than the critical causes waves, necessarily decaying with distance, to grow or decay with time.     

Petrogenesis of oceanic granites from the Aves Ridge in the Caribbean Basin

A genetic model proposed for granitic rocks dredged from the Aves Rise involves a sodium-enriched hydrothermal fluid phase, shallow emplacement, and significant derivation of components from the upper mantle. Megascopic observations of serially slabbed sections of the rock samples show that aggregates of plagioclase phenocrysts concentrate into channel-like mats. The presence of a late-stage, hydrothermal fluid is suggested by crystal-lined cavities in the plagioclase aggregates.     

The Broken Hill ore body,Australia

The paper reviews recent works on the Broken Hill ore body to see what data is available on the origin and history of the ore. A high grade metamorphism is recognizable (the Willyama Metamorphism) and this was followed by a number of retrograde metamorphic events. The characteristics of these events is described and this is followed by an analysis of the hypothesis that there is a stratigraphic control of Broken Hill type mineralization. It is concluded that any control that does exist is of a regional nature and that the evidence is equally as good for a restriction of mineralization to areas of high grade metamorphism. Many of the isotopic and geochronological results for Broken Hill are not diagnostic as far as ore genesis is concerned. They do present an internally consistent set of data that records three major events, the Willyama Metamorphism and introduction of the Broken Hill type mineralization at 1700 m. y., the intrusion of the Mundi Mundi Granite and cross cutting pegmatites at 1560 m. y., and retrograde metamorphism and introduction of the Thackaringa Mineralization at or prior to 500 m.y. The sulphides have been deformed in the retrograde schist zones and the ore therefore predates this event. But there is no evidence at the moment that unambiguously establishes that the sulphides were present prior to the Willyama Metamorphism. If it was present prior to or during the Willyama Metamorphism and there is no period of deformation prior to the first recognizable folds at Broken Hill, then the sulphide mass was initially grossly discordant with bedding.

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Zusammenfassung Die Arbeit bringt Ergebnisse der neuesten Untersuchungen über die Broken-Hill-Lagerstätte anschließend an einen Überblick früherer Arbeiten. Der intensiven Willyama-Metamorphose folgen verschiedene retrograde Vorgänge, über die Einzelheiten mitgeteilt werden. Ferner wird die Hypothese einer stratigraphischen Kontrolle der Vererzung einer Prüfung unterzogen und festgestellt, daß die maßgeblichen Frakturen regionaler Natur sein müssen und daß die Beobachtungen somit eine Annahme der Vererzung der hochmetamorphen Gebiete ebenso stark stützt. Viele Resultate von Isotopenzusammensetzungen und geochronologischen Untersuchungen sind für Broken Hill nicht diagnostisch, wenigstens was die Erzgenese betrifft. Sie belegen 3 Hauptereignisse: die Willyama-Metamorphose und den Beginn der Vererzung um 1700.10⁶a, die Intrusion des Mundi Mundi Granits und querschlägiger Pegmatite um 1560.10⁶a und eine retrograde Metamorphose und den Eintritt der Thackaringa-Vererzung um oder vor 500.10⁶a. Die Sulfide sind in der Zone der retrograden Schiefer deformiert worden, was beweist, daß die Vererzung älter ist als dieses Ereignis. Es gibt aber z. Z. keinen Beweis, daß die Sulfide vor der Willyama Metamorphose vorhanden gewesen sind. Wenn sie vor oder während dieses Ereignisses vorhanden gewesen sind und wenn vor der Zeit der ersten deutlichen Falten in Broken Hill keine Deformation stattgefunden hat, dann war die Sulfidmasse ursprünglich in der Schichtung stark diskordant.

     

Darkening of silicate rock powders by solar wind sputtering

Hydrogen ion irradiation of powdered igneous rocks, including Apollo rocks, has been observed in the laboratory to darken the powders and to make their optical properties similar to the Moon's. An extensive series of investigations shows that this darkening is not spurious. These results are consistent with those of other investigators, including Nash (1967). Darkening of lunar igneous rock powders by the formation of solar wind-sputtered glass films is a real process which occurs on the Moon. The time scale for darkening of undisturbed lunar soil is of the order of 50000–100000 yr. Comparison of the rates of the formation of glasses on the lunar surface by solar wind sputter-deposition, meteorite impact melting and impact vaporization-deposition indicates that these processes are of comparable importance under the present flux of meteorites. Thus the formation of glass by sputter-deposition must be regarded as a major process on the lunar surface.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.     

The opacity of some local Martian dust storms observed by the Viking IRTM

In this paper we analyze some Viking infrared thermal mapping (IRTM) measurements of local Martian dust storms observed in the southern tropical region of the planet between L_s=225 and 262°. The derived opacities of these storms show that in the most opaque regions of the cloud, the optical thickness may be ≈6. Away from the individual clouds, the opacity is ≈2, which is still about four times the background level of dustiness in the Martian atmosphere. We find considerable structure in the derived opacity which will create corresponding variations in the atmospheric heating, which in turn may have an important feedback upon the local winds.     

Influence of wind upon water quality in Liverpool Bay

Comprehensive distribution patterns of physical and chemical characteristics have been obtained from a series of cruises in Liverpool Bay. The marked feature of these distributions was their temporal variability, suggesting that the surface residual circulation is also temporally variable. The influence of wind stress upon the circulation pattern and hence water quality of this sea area is illustrated.