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.     

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.     

Kondensstreifen auf dem Radarschirm?

Zusammenfassung Es wird über einige Radarbeobachtungen berichtet, die den Schluß nahelegen, daß gelegentlich Kondensstreifen von Flugzeugen als meteorologische Radarechos sichtbar werden.

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Summary Several observations seem to indicate that occasionally condensation trails from aircraft may produce meteorological radar echo.

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Résumé L'auteur, se basant sur quelques observations faites au radar, rapporte que les traînées de condensation laissées derrière eux par les avions peuvent parfois apparaître sur les écrans sous forme d'échos météorologiques.

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Mit 2 Textabbildungen     

Étude du mouvement du sol au voisinage d'une faille: II

Resumo Ni modifiis la hipotezojn de antaùa noto por reprezenti eventualajan zonojn kun plasteca fluo en la Tero. La simpla modelo uzita por la antaùsisma deformigo permesas studi la liniojn kie elementaj sirplanoj estas paralelaj al fiksa plandirekto. Oni trovas por la responda sisma deformigo simplan proksimuman formulon. Aplikado al la fendego de San Francisco donas profundecon de nur 7 km.

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Summary The hypotheses of a previous note are modified to take into account eventual zones of plastic flow in the ground. A simple model of preseismical strain is used, which enables us to study the repartition of the elementary shear planes. It is possible to deduce the extent of faulting in depth from the combined preseismical and seismical strains. An application to the San Francisco earthquake gives a depth of 7 km only.

     

A condensation method particle size spectrometer

Summary A condensation method of measuring the size frequency distribution of Aitken nuclei is described. Making use of thePollak-Nolan photoelectric nucleus counter it is based on the removal of the nuclei activated at various overpressures from the counter by precipitation and the counting of those that remain. Various stored aerosols are investigated by means of it and the decay mechanisms of these aerosols discussed in the light of the results obtained. The value of the exhaustion method of finding diffusion coefficients is also examined.

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Zusammenfassung Es wird eine Kondensationsmethode zur Messung des Häufigkeitsspektrums der Größenverteilung von Aitken-Kernen beschrieben. Unter Benützung des photoelektrischen Kernzählers vonPollak undNolan beruht sie darauf, daß die aktivierten Kerne bei verschiedenen Überdrucken durch Ausfällung ausgeschieden und die übrigbleibenden ausgezählt werden. Mit dieser Methode wurden verschiedene gespeicherte Aerosole untersucht und auf Grund der Ergebnisse der Zerfallsmechanismus dieser Aerosole diskutiert; es wurde auch die Eignung der Evakuierungsmethode zur Bestimmung von Diffusionskoeffizienten untersucht.

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Résumé L'auteur décrit une méthode permettant de mesurer par condensation le spectre des fréquences de la répartition des grosseurs de noyaux d'Aitken. Cette méthode repose sur le principe suivant: On élimine les noyaux activés sous différentes pressions par sédimentations successives. Les noyaux restant sont alors dénombrés par le compteur photoélectrique de noyaux mis au point parPollak etNolan. L'auteur a étudié par cette méthode divers aérosoles conservés et il discute, sur la base des résultats obtenus, le mécanisme de désagrégation de ces aérosoles. Il a également étudié si la méthode par évacuation se prêtait à la détermination des coefficients de diffusion.

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With 1 Figure     

Measurements of radio noise at 0.700 mc and 2.200 mc from a high-altitude rocket probe

Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5₋₃⁺⁶) × 10⁻¹⁹ W m⁻²)(c/s)⁻¹ at 0·700 Mc and (1·8^+1.0_−0.5 × 10⁻¹⁹ W m⁻² (c/s)⁻¹ at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6₋₃⁺⁵) × 10⁻²⁰ W m⁻² (c/s)⁻¹ sr⁻¹b(2·200 Mc) = (1.4^+1.0_−0.5 × 10⁻²⁰ W m⁻² (c/s)⁻¹ sr⁻¹ The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed.     

Untersuehungen an den Sedimenten der Tongrube von Willershausen

Zusammenfassung Nach der Profilaufnahme sind die Sedimente der Tongrube der Ziegelei von Willershausen in zwei Gruppen einzuteilen : A. Die unteren hellen Schichten, B. die oberen dunklen Schichten.Die unteren hellen Schichten bestehen aus Sandsteinen, Sanden, tonigen Sanden und Grobtonen, welche Quarz, Feldspäte und Glimmer als Hauptminerale und in geringeren Mengen Illit, Chlorit und manchmal Montmorillonit füren. Als Schwerminerale dieser Sande und Sandsteine treten der Häufigkeit nach Apatit, Zirkon, Granat, Anatas, Rutil, Turmalin und Opakminerale auf.Die oberen dunklen Schichten bestehen hauptsächlich aus mm-rhythmisch geschichteten Tonen mit Einschaltung einzelner Mergelbänke und toniger Sandschichten. Dioktaedrischer Illit ist das häufigste Tonmineral, dann folgen Chlorit und in geringeren Mengen in feinen Fraktionen Montmorillonit. Die Chlorit-Reflexe verschwinden bereits bei Erhitzung auf 450° C. Chemisch handelt es sich um die dem Pennin naheliegenden Diabantite.Die Unterschiede in Beschaffenheit und Menge der Quarze, Feldspäte und Glimmer, die unterschiedliche Verteilung der Schwerminerale sprechen dafür, daß die hellen Schichten wahrscheinlich zum Mesozoikum, vielleicht zum Buntsandstein gehören.Von der Mathematisch-Naturwissenschaftlichen Fakultät der Georg-August-Universität zu Göttingen genehmigte Dissertation.     

Petrogenesis of Glaucophane Schists

Some glaucophane schists are chemically indistinguishable fromgreenschists and epidote amphibolites. Provided all three rocktypes represent equilibrium assemblages, they must have formedunder differing physical conditions. The mineralogy of suchglaucophane schists taken in conjunction with experimental evidencesuggests that these rocks formed at low temperatures and atrelatively elevated pressures. The relatively high-pressure,low-temperature phases lawsonite, jadeitic pyroxene, and metamorphicaragonite are diagnostic of physical conditions attending thismetamorphism. Differential stress may aid in the attainmentof the appropriate mean pressure necessary for the productionof these phases. Graphic analysis and approximated thermodynamic calculationsindicate that relatively elevated pressures, or relatively lowtemperatures, or both, promote the formation of glaucophanein rocks of a wide range of bulk compositions while restrictingthe compositional range of albite-bearing rocks. It is concludedthat the coexistence of glaucophane with carbonate, calcium-aluminumsilicate or paragonite results from such physical conditions,and it is on the basis of these associations or, equally well,the presence of lawsonite, jadeitic pyroxene, or metamorphicaragonite that the blueschist facies should be defined. High pressures are not required for the production of glaucophaneitself. It is stable under physical conditions present in thegreenschist and epidote amphibolite facies in rocks deficientin CaO and rich in Na₂O and MgO relative to A1₂O₃. Such bulkcompositions might result from exchange of material betweenserpentinite and albite-bearing country rocks, and could accountfor glaucophane aureoles around, and inclusions of glaucophanerock within, some serpentinites.     

Röntgenmikroanalytische untersuchungen an titanomagnetiten tertiärer eflfusiva zur lösung gesteinsmagnetischer fragen

Zusammenfassung Gesteinsmagnetische Studien haben gezeigt, daß für das Verstandnis des jeweiligen magnetischen Verhaltens von Gesteinen u. a. detaillierte mineralogischoptische und nicht zuletzt chemische Untersuchungen nötig Bind. Zum Studiurim der Verteilung der Elemente im Erzkorn wurde die Röntgenmikroanalyse benutzt.Die Methode der Röntgenmikroanalyse wird beschrieben. Die Ergebnisse der Untersuchungen an Titanomagnetiten tertiärer Effusiva kennzeichnen die Inhomogenität der chemischen Verteilung im Erzkorn und lassen die Klärung von Phänomenen zu, die mit Hilfe der durchschnittlichen chemischen Analyse Bowie magnetothermischen u. a. Untersuchungen nicht möglich war.

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Studies on magnetic rocks have demonstrated that detailed informations on composition within ore-particles are needed in order to understand the respective magnetic behaviour. For studying such compositions microanalytic X-ray methods are used.The applied microanalyser is described.Results, gained on this way with tertiary effusiva, let recognize the inhomogenity of composition e.g. within titanomagnetites. They allow clarifying of phenomena, which cannot be understood on another way.