K Ar isochron study of the Tudor Gabbro,Grenville Province,Ontario |
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| Authors: | A Hayatsu HC Palmer |
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| Institution: | Department of Geophysics, University of Western Ontario, London, Ont. Canada |
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| Abstract: | Ten whole-rock samples from the Tudor Gabbro, Grenville Province, Ontario, Canada have been dated by the KAr method. The ages calculated by the conventional method range from 900 m.y. to 2040 m.y. On an isochron plot, three samples from a sampling site near the northern border of the gabbro lie along a 670-m.y. isochron with an initial40Ar/36Ar ratio of about 17,300 whereas all other samples lie along another 670-m.y. isochron with an initial ratio of about 5000. Although it is not certain yet as to what geological event the isochron age represents, the results clearly demonstrate that the effect of initial argon can be significant even on old samples such as these. |
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