ANALYTICAL AERIAL TRIANGULATION BLOCK ADJUSTMENT; THE DIRECT HEIGHT SOLUTION INCORPORATING TIE-STRIPS

The historical development of analytical aerial triangulation block adjustment is mentioned by way of introduction. The advantages of separating the plan and height adjustments are given and the observation equations of a typical adjustment section are analysed to show that this convenient practice is justified in normal circumstances. The principles of a direct solution of the normal equations suitable for a moderate-sized computer, are explained and developed in detail for the height adjustment. The advantages of tie-strips in the height adjustment are demonstrated and the difficulties which then arise are discussed. An approximate method which overcomes these difficulties is developed. Details of the computer programmes used are given in Appendix B.     

Sur la présence de nickel dans un gisement de bauxite près de Mégare

Résumé L'exploitation récente d'un gisement de bauxite près de Mégare (Grèce) a fait apparaître sur les calcaires de base une concentration verte d'oxyde de nickel relativement élevée. La présence dans le gisement d'argiles rouges, renfermant de fortes proportions d'oxyde de fer avec des teneurs relativement faibles en alumine et des traces d'oxyde de nickel, induit à penser qu'il s'agit d'un produit latéritique dérivé d'une roche ultrabasique et transporté ultérieurement sur la région calcaire karstifiée avec ses remplissages bauxitiques. L'étude se termine par une hypothèse sur la genèse de ce gîte singulier.

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The recent mining of a bauxite deposit near Megara (Greece) has shown on the footwall limestone a relatively high concentration of a green nickel oxide. The occurrence in the same deposit of red clays with a rather high percentage of iron oxide and a low content of alumina, together with some traces of nickel, induces to think that this material is composed of a lateritic soil derived from an ultrabasic rock and subsequently transported on karstified limestone with its bauxitic fillings. — The study ends with an hypothesis on the genesis of this unusual deposit.

     

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Discussion of the Möller radiation chart

Summary M?ller's assumptions for the carbon dioxide-water vapor overlap region, which lead to the construction of his radiation chart, are reinvestigated in the light of modern theory. A new radiation chart, taking into account the carbon dioxide-water vapor overlap, is constructed using water vapor and carbon dioxide absorption data as furnished byM?ller andElsasser respectively. The results of the radiative fluxes computed from the new chart are compared with equivalent results using the original M?ller and the revised Elsasser radiation diagrams, as well as with measurements.

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Zusammenfassung Die Berechtigung derM?llerschen Annahme zur getrennten Behandlung von Kohlens?ure- und Wasserdampfabsorption zwecks Konstruktion eines atmosph?rischen Strahlungsdiagrammes wird im Lichte der modernen Theorie diskutiert. Ein neues Strahlungspapier wird vorgelegt, das die gleichzeitige Anwesenheit von Kohlens?ure und Wasserdampf im gleichen Spektralbereich berücksichtigt. Dieses beruht auf Wasserdampf- und Kohlens?uredaten, die vonM?ller undElsasser vorgegeben wurden. Nach dem neuen Strahlungsdiagramm berechnete Werte werden mit Me?werten und theoretischen Werten verglichen, die mit dem ursprünglichen M?llerschen und mit dem verbesserten Elsasserschen Strahlungspapier ermittelt wurden.

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Résumé Au vu des théories modernes, on discute l'hypothèse formulée parM?ller et sa justification, hypothèse selon laquelle il est nécessaire de traiter séparément l'absorption du dioxyde de carbone et celle de la vapeur d'eau lors de l'établissement d'un diagramme du rayonnement atmosphérique. On propose alors un nouvel abaque qui tient compte de la présence simultanée du dioxyde de carbone et de la vapeur d'eau dans la même région spectrale. Cet abaque s'appuie sur les valeurs données parM?ller et parElsasser, valeurs valables pour ces deux gaz. On compare le résultat de calculs effectués avec ce nouvel abaque à des mesures et à des valeurs théoriques ces dernières étant basées tant sur les travaux originaux deM?ller que sur l'abaque amélioré deElsasser.

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With 4 Figures     

A Study of the Strathcona Mine and Its Bearing on the Origin of the Nickel-Copper Ores of the Sudbury District, Ontario

The Strathcona iron-nickel-copper sulfide ore deposit lies atthe base of the Sudbury Nickel Irruptive along the north rimof the Sudbury basin. In the vicinity of the deposit the mainbody of the Nickel Irruptive consists of an upper unit of 3700ft (1200 m) of granophyre (the ‘micropegmatite’)and a lower unit of 1500 ft (500 m) of augite norite (the ‘felsicnorite’) separated by 300 ft (100 m) of transitional rock(the ‘transition zone’). Two augite norite intrusions(the ‘mafic norite’ and the ‘xenolithic norite’)that are younger than the felsic norite occur along its lowercontact. The xenolithic norite is relatively rich in xenolithsand grades downwards into a unit known as the ‘hanging-wallbreccia’. The breccia resembles the xenolithic noritebut contains a higher proportion of xenoliths. A quartz-plagioclase-augite gneiss (the ‘footwall gneiss’)underlies all units of the Nickel Irruptive. A cataclastic breccia(the ‘footwall breccia’) which formed as a resultof comminution of both gneiss and overlying Irruptive rocksis present in most areas between the gneiss and the Nickel Irruptive.The ore body occurs partly as a dissemination of sulfides inthe matrix of the hanging-wall breccia (‘hanging-wallore’), partly as a fine dissemination and massive stringersof sulfide in the footwall breccia matrix (‘main-zoneore’), and partly as massive stringers of sulfide in thefootwall gneiss (‘deep-zone ore’). Xenoliths in the xenolithic norite and hanging-wall brecciarange from dunite to olivine gabbro. Olivine in the xenoliths(composition estimated by an X-ray method) varies from Fo73to Fo85, and hypersthene and augite (composition estimated byelectron microprobe analysis) vary from Fs25 to Fsi3, and Fsi3to Fs5, respectively. The iron content of the mafic mineralsshows a positive correlation with the proportion of felsic mineralsin the xenoliths, suggesting that the xenoliths have been derivedfrom a cryptically layered body of mafic and ultramafic rock.The wide distribution of xenoliths around the margin of theNickel Irruptive coupled with the absence of any obvious externalsource is strong evidence that the xenoliths are cognate, supportingWilson's (1956) proposal that the Irruptive is a funnel-shapedintrusion with a zone of ultramafic rocks towards its base. Hypersthene ranges from Fs33 to Fs28 in the felsic norite, fromFs28 to Fs22 in the mafic norite, and from Fs28 to Fs20 in thexenolithic norite. Augite ranges from Fsl6 to Fs14 in the felsicnorite and from Fs14 to Fsn in both the mafic and xenolithicnorites. The distribution coefficient for iron and magnesiumbetween coexisting augite and hypersthene ranges from 1-0 insome of the xenoliths to 1-5 in some samples of felsic norite,indicating that the two pyroxenes equilibrated at, or near,magmatic temperature. The composition of plagioclase in thefelsic norite, mafic norite, and xenolithic norite is aroundAn65-70 but decreases to An44 in those Irruptive rocks closestto the footwall breccia. The composition of plagioclase withinthe breccia varies between An32 and An43. Sodium metasomatismappears to have affected the breccia and to have spread outto affect adjacent rocks. The concentration of nickel and copper in the sulfides variessystematically across the ore deposit. The nickel content ofiron-nickel sulfides varies between 2-5 and 3 per cent in thehanging-wall ore but increases regularly from 3 per cent to5 or 5-5 per cent from hanging wall to footwall across the main-zoneore. Copper concentration shows a similar but more erratic variation.The variation is attributed to thermal diffusion of nickel andcopper within the main-zone ore along a gradient induced bythe overlying, hot, Nickel Irruptive. The principal opaque minerals in the ore body are, in the orderof their abundance, pyrrho-tite of at least two types, magnetite,pentlandite, chalcopyrite, and pyrite. All of the sulfides inthe hanging-wall ore are the result of exsolution from a high-temperature,pyrrhotite solid solution. Pyrite started to exsolve below 700C, chalcopyrite below 450 C, and pentlandite below 300 C.Monoclinic pyrrhotite formed from the host hexagonal pyrrhotiteprobably between 300 and 250 C. The temperature of formationof the sulfides in the main-zone ore has been obscured by reworkingof the ore after its first emplacement. The principal ore sulfides, pyrrhotite and pentlandite, arecommon throughout the mafic norite, xenolithic norite, and hanging-wallbreccia, occurring in amounts around 5 per cent in most samples.Pyrrhotite and pentlandite are extremely rare in the overlyingfelsic norite where pyrite is the most common sulfide. It occursin amounts between 01 and 0-5 per cent, commonly together withsecondary amphibole after pyroxene. The sulfides in the maficand xenolithic norites and in the hanging-wall breccia occupyspaces interstitial to the silicates, and little or no replacementof silicates by sulfides has occurred. In the main-zone ore,evidence of small-scale replacement of silicates by sulfidesis common. The high percentage of pyrrhotite and pentlandite in the maficand xenolithic norites in contrast to the felsic norite, texturalrelations between sulfides and silicates, and the high temperaturesindicated by the pyroxene distribution coefficients lead tothe conclusion that the hanging-wall sulfides (including thehanging-wall ore) at Strathcona were introduced with these youngernoritic intrusions. Data on the solubility of sulfides in silicatemagmas rule out the possibility that the bulk of the sulfideswere in solution in the noritic magmas; the data support thehypothesis that during intrusion the sulfides were held in suspensionin the in the magmas as droplets of immiscible sulfide-oxideliquid. Calculations on the rate of settling to be expectedfor such sulfide droplets are consistent with this hypothesis.The manner of emplacement of the main-zone ore is less certain;our explanation is that this ore consists of sulfides that originallysettled out of, or collected along, the base of the hanging-wallbreccia zone and were subsequently incorporated in the brecciationthat gave rise to the footwall breccia. The origin of the sulfides at Strathcona is clearly connectedclosely with the origin of the younger noritic intrusions. Asimilar connexion exists between sulfides and young marginalintrusions at many other Sudbury deposits. Jt is possible thatboth sulfides and intrusions are portions of the Nickel Irruptivemagma that lagged behind the main body of magma and were intrudedat a later stage. Alternatively, the young intrusions may haveassimilated sulfides from a sulfide-rich zone within or at themargin of the deeper layers of the Irruptive.     

Variations in exospheric density at heights near 1100km, derived from satellite orbits

In an earlier paper, values of exospheric density were obtained from the orbit of Echo 2 for the years 1964–1965. The results indicated a semi-annual variation in density by a factor of between 2 and 3, considerably larger than predicted by existing atmospheric models.

These studies have now been extended to the beginning of 1967, using both Echo 2 and Calsphere 1, to show how the density is responding to increasing solar activity. Variations in density during 1964 have been analysed in more detail. The long-term variation associated with the solar cycle and the short-term variations associated with magnetic and solar disturbances agree with the variations expected on the basis of current models. The semi-annual variation is persisting to higher levels of solar activity, and although its amplitude is diminishing the factor of variation was still 1.6 in 1966.     

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On the basic principles of geophysical radioactive measurements

Summary The process of radon diffusion in space and time through rocks is treated in detail from the point of view of radiometric prospecting for oil. Taking into account the depth and diffusivity conditions encountered in nature it is stated that vertical radon diffusion reaching from the oil deposits up to the surface cannot be expected. Time intervals as required for setting in of a stationary concentration state and decay conditions of the radon lead to the conclusion that the penetration of emanometric measurements seldom exceeds the depth of 5–10 m.     

Prediction of the field strength fading forms by means of weather situations

Summary In this study the different forms of the electromagnetic field strength recordings at the Thera-Crete microwave line of link are examined, in comparison with the corresponding weather situations prevailing over that area. According to the amplitude of fluctuations, the different forms of recordings have been classified in three basic typesA, B, C and the annual frequency of the appearance of these types has been observed. Finally, the influence of weather situations on radio wave propagation was examined and it has been found that in most cases a close relationship exists between weather situations and the different fading forms of the electromagnetic field so that a prediction of the fading form be possible by means of the weather forecast.This study was sponsored by a research grant from NATO's Scientific Committee.     

On the frequency equation for love waves due to abrupt thickening of the crustal layer

Summary The effect of thickening of the crustal layer in mountainous region on the dispersion curve of Love waves has been studied. Perturbation method has been applied to obtain the modified frequency equation for Love waves through the surface of separation between a semi-infinite material and a layer the thickness of which abruptly increases throughout a certain length of the path. The effect is to decrease the phase velocity of the waves particularly in the low period range. It has been pointed out that by proper study, the amount of thickening may be obtained.