Rb–Sr Isotopic Systematics of the Foot Bay Gneiss, Donaldson Lake Gneiss, and Pegmatite Dikes from the Fay Mine, NW Saskatchewan

Sassano, G. P.; Baadsgaard, H.; Morton, R. D.

doi:10.1139/e72-124

Cited by 7 publications

(2 citation statements)

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“…Several workers (Krogh & Davis, 1973;Faure & Powell, 1972, pp. 100;Hughes & Malpas, 1971;Sassano, Baadsgaard & Morton, 1972) have demonstrated that rocks may show a significant degree of 'open system' behaviour (with respect to Rb and Sr) during metasomatism, mineralization and metamorphism. If the following assumptions are valid, that: (1) there was complete or at least partial isotopic homogenisation during 'spilitization'; and (2) the system has remained closed since the end of 'spilitization'; then, the age of 1872 ± 10 ma may represent the time of spilitization.…”

Section: Isotopic Data and The Nature And Timing Of Spillitizationmentioning

confidence: 99%

Trace-element and isotopic data and their bearing on the genesis of Precambrian spilites from the Athapuscow aulacogen, Great Slave Lake, Canada

Olade

1975

Geol. Mag.

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The nature and timing of 'spilitization', and the original composition of 'spilitized' Precambrian lavas fron the Athapuscow aulacogen, Great Slave Lake (Canada) are investigated, using geochemical and Rb/Sr isotopic methods. Relationships and abundances of trace elements of petrogenetic significance suggest that the spilites were not derived from alkaline basaltic magmas, but show petrogenetic affinity with tholeiitic basalts from continental or volcanic island environments. This new interpretation conforms well with the supposed tectonic and geologic environment in which the lavas and pyroclastics were erupted. Assuming an 'open system' behaviour for Rb and Sr during intense metasomatism, the isochron age of 1872 Ma obtained for the lavas is considered as the time of 'spilitization'. This age, when compared with geochronometric data obtained by other techniques, suggests that the time interval between initial volcanism and subsequent 'spilitization' event was brief, and probably related to diagenesis or burial metamorphism during rapid subsidence and sedimentation commonly associated with rifting within aulocogens. A relatively low initial 87 Sr/ 86 Sr ratio of 0-7018 ± 00005 obtained for the lavas either reflects the low Sr isotope values characteristic of diagenetic pore fluid in Precambrian seas, or suggests that the original 'primitive' initial ratio was not adversely affected by the 'spilitization' process.

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Section: Isotopic Data and The Nature And Timing Of Spillitizationmentioning

confidence: 99%

Trace-element and isotopic data and their bearing on the genesis of Precambrian spilites from the Athapuscow aulacogen, Great Slave Lake, Canada

Olade

1975

Geol. Mag.

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“…The Rb/Sr age of 1860 (1 975) f 20 Ma for discordant pegmatites (Sassano et al 1972) in the Martin Lake area, may provide evidence of the late stages of Hudsonian regional metamorphism and provide an upper limit for deposition of the Martin. Sassano et al (1974) have subsequently obtained a Rb/Sr isochron age of 1675 (1780) f 72 Ma on lamprophyre dikes that cut the pre-Martin basement. These dikes are probably pre-Martin (L. P. Tremblay, personal communication 1974), and provide a maximum age for Martin volcanism and sedimentation.…”

Section: Kaminak Paleomagnetic Data-local Signijicancementioning

confidence: 98%

The Paleomagnetism of Kaminak Dikes—No Evidence of Significant Hudsonian Plate Motion

Christie¹,

Davidson²,

Fahrig³

1975

Can. J. Earth Sci.

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A paleomagnetic study was done on 28 diabase and 6 lamprophyre dikes from the vicinity of Kaminak Lake in the District of Keewatin. These dikes are Proterozoic and cut across an area of Archean rocks. Their metamorphic grade within this region varies from nil to amphibolite facies. Two stable magnetization directions were obtained from the diabase on AF demagnetization; one from 3 unmetamorphosed diabase dikes of D = 205", I = 3", %, =24", with a corresponding pole position at 23.8'S, 122.3" W, a,, = 16.5"; the other from the metamorphosed diabase of D = 176", I = 65", %, = 4", with pole position at 20.4' N, 92. l o W, %, = 6.1". The first is believed to be thermoremanent and approximately 2300 Ma old, while the second is a metamorphic direction of approximately 1800 Ma. The six lamprophyres give a stable remanence of D = 174", I = 78", a,, = loo, with a pole position at 40.9"N, 92.8"W, %, = 17", essentially the same as the metamorphosed diabase.A number of samples were also thermally demagnetized. Most of the results obtained were the same as those obtained from the A F treatment. However, one diabase site gave adirection similar to that obtained from the 3 unaltered dikes, and one of the lamprophyres showed a reversal.The pole position of the altered Kaminak diabase relative to that for the unconformably overlying Dubawnt Group suggests that the polar wandering curve for this part of the Aphebian may be more complex than previously thought. It is quite probable that the earlier Aphebian pole positions (Matachewan, Nipissing), as usually plotted, are actually antipodal points in terms of the polar wandering curve.Une etude paleohagnetique fut poursuivie sur des dykes de diabase (28) et de lamprophyre (6) dans la region du Lac Kaminak dans le District de Keewatin. Ces dykes proterozoiques traversent des roches archeennes. Leur degre de metamorphisme dans cette region varie de nu1 afacies d'amphibolites. Deux directions stables de magnetisation ont Cte obtenues des diabases par la methode de demagnetisation S.F.; une des directions provient de 3 dykes non metamorphises de D = 205", I = 3", a,, = 24"avec la position du p81e correspondant a 23.8"S, 122.3" W, = 16.5" I'autre direction provient des diabases metamorphises de D = 176", I = 65", a95 = 4" avec la position du p8le a 20.4" N, 92. l o W, orgS = 6. lo. On croit que la premiere magnetisation est de type thermoremante et date de 2.300 Ma, la seconde est une direction magnttique datant d'environ 1.800 Ma. Les six lamprophyres donnent une remanence stable de D = 174", I = 78", = 10" avec la position du p6le a 40.9" N, 92.8" W, = 17' essentiellement la mbme que celle des diabases metamorphises.Un certain nombre d'echantillons avaient subi une demagnetisation thermique. La plupart des resultats obtenus etaient les mbmes que ceux de la mkthode AF. Cependant, I'un des diabases donnait une direction semblable a celle obtenue pour les trois diabases non alteres et un des lamprophyres montrait un magnetisme inverse.Les donnkes paleomagnetiques favorisent I'hypothese de ...

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Thermotectonic evolution of the churchill province in Northern Saskatchewan

1980

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Rb–Sr Isotopic Systematics of the Foot Bay Gneiss, Donaldson Lake Gneiss, and Pegmatite Dikes from the Fay Mine, NW Saskatchewan

Cited by 7 publications

References 0 publications

Trace-element and isotopic data and their bearing on the genesis of Precambrian spilites from the Athapuscow aulacogen, Great Slave Lake, Canada

Trace-element and isotopic data and their bearing on the genesis of Precambrian spilites from the Athapuscow aulacogen, Great Slave Lake, Canada

The Paleomagnetism of Kaminak Dikes—No Evidence of Significant Hudsonian Plate Motion

Thermotectonic evolution of the churchill province in Northern Saskatchewan

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