11111*11111 CA9700379 - Q 1 INIS- CSee RADIOGENIC AGE AND ISOTOPIC STUDIES: REPORT 9 1996 //?/§-€&•• ooof- GEOLOGICAL SURVEY OF CANADA CURRENT RESEARCH 1995-F RADIOGENIC AGE AND ISOTOPIC STUDIES: REPORT 9 1996 m 2 8 k 1 9 ©Her Majesty the Queen in Right of Canada, 1996 Catalogue No. M44-1995/6E ISBN 0-662-16431-0 Available in Canada from Geological Survey of Canada offices: 601 Booth Street Ottawa, Ontario K1A 0E8 3303-33rd Street N.W., Calgary, Alberta T2L 2A7 100 West Pender Street Vancouver, B.C. V6B 1R8 or from Canada Communication Group - Publishing Ottawa, Ontario K1A0S9 and through authorized bookstore agents and other bookstores A deposit copy of this publication is also available for reference in public libraries across Canada Price subject to change without notice Cover description Photograph of a dismembered mafic dyke in anorthositic gabbro, Uvauk Complex, District of Keewatin, Northwest Territories. The complex, located 100 km northwest of Chesterfield Inlet, is comprised of an Archean layered gabbro-mafic granulite-anorthosite suite which was deformed and metamorphosed at mid-crustal levels during Late Archean and Paleoproterozoic events. It forms a rootless, triangular segment (30 x 20 km) of straight gneisses, the boundaries of which are marked by granulite grade ultramylonites. Photo by S. Telia, GSC 1992-253 DD The concordia plot displays the geochronology, carried out by Chris Roddick, on a representative sample from the anorthositic gabbro ultramylonite. The data suggests that the 1936 + 8 Ma zircon age records a Paleoproterozoic, granulite grade, ductile event that overprinted an Archean (ca. 2.59 Ga), granulite grade mylonitic event. Titanite and rutile ages record post-mylonite, uplift and cooling events. Thermobarometric data suggests that the Paleoproterozoic event occurred at pressures in excess of 10 kbar, (30 km). CONTENTS Introduction R. R. Parrish ..............................................................................................................................................v 1. Efficient mass calibration of magnetic sector mass spectrometers J.C. Roddick.......................................................................................................................................... 1 2. U-Pb zircon age for a volcanic suite in the Rankin Inlet Group, Rankin Inlet map area, District of Keewatin, Northwest Territories S. Telia, J.C. Roddick, and O. van Breemen ...........................................................................11 3. Archean crustal evolution in the central Minto block, northern Quebec T. Skulski, J.A. Percival, and R.A. Stern..........................................................................................17 4. Geology and age of the Lac a la Perdrix fenite, southern Gatineau district, Quebec D.D. Hogarth and O. van Breemen .................................................................................................33 5. Preliminary chronostratigraphy of the Tetagouche and Fournier groups in northern New Brunswick R.W. Sullivan and C.R van Staal.......................................................................................................... 43 6. A compilation of 40Ar-39Ar and K-Ar ages: Report 25 P.A. Hunt and J.C. Roddick.....................................................................................................................57 Other publications containing geochronological data generated by the Geochronology Laboratory of the Geological Survey of Canada ............................................................................... 75 hext mmim S®ft BLANK RADIOGENIC AGE AND ISOTOPIC STUDIES REPORT 9 INTRODUCTION INTRODUCTION “Radiogenic Age and Isotopic Studies ” is an annual La publication intitulee Radiogenic age and isotope studies est un collection of research presentations containing U-Pb, recueil annuel d ’articles scientifiques contenant des resultats de Sm-Nd, Rb-Sr, and 40Ar-39Ar data generated by the datations U-Pb, Sm-Nd, Rb-Sr et 40Ar-39Ar, effectuees par le per­ Geochronology Laboratory under the auspices of the sonnel du laboratoire de geochronologie, sous les auspices de la of the Continental Geoscience Division, Geological Division de la geologic du continent (Commission geologique du Survey of Canada. Report 9 contains 5 papers from Canada, CGC). Le rapport 9 contient cinq articles sur des regions regions across Canada (see back cover), followed by d ’un peu partout au Canada (voir la couverture arriere), suivis d ’une a compilation of 40Ar-39Ar and K-Ar ages. Authors compilation d ’ages determines au moyen des methodes 40Ar-39Ar herein present data, relate results to field settings, and et K-Ar. Les auteurs presentent des donnees, etablissent des liens make brief interpretations. Readers are thus entre les resultats et les milieux etablis a l’aide des travaux sur le reminded that much of the research encompassed terrain, en plus de donner de courtes interpretations. Les lecteurs represents “work-in-progress" and that more exten ­ doivent cependant garder en memoire qu’une bonne partie des sive publications may follow at a later date. Listed at recherches citees sont «en cours» et que des publications plus the end of the report are additional publications con ­ detaillees pourraient suivre. A la fin du rapport se trouve une liste taining data produced by the CGD lab, mostly in de publications, pour la plupart dans des revues scientifiques ne outside journals. relevant pas de la CGC, dans lesquelles on fajt reference a des donnees produites par le laboratoire de geochronologie. L’annee 1995 en a ete une d ’attentes et de tragedie pour le Forthe Geochronology Laboratory, 1995 wasayear laboratoire de geochronologie. Chris Roddick est decede acciden- of expectations and tragedy. On February 23, 1995, tellement le 23 fevrier 1995. Du point de vue scientifique, il a fourni Chris Roddick ’s accidental death left not only a scien ­ un apport qui a marque profondement la Commission geologique tific legacy which has been profound for the Geological du Canada et des collegues de partout dans le monde. Son depart Survey of Canada and scientists around the world, but represente une perte de competences qui sera fortement ressentie au also an expertise that will be deeply missed in the laboratoire de geochronologie. Geochronology Laboratory. Chris Roddick a beaucoup apporte a la methode isotopique. II a Chris Roddick made a substantial mark on isotope contribue de fagon continue aux ouvrages scientifiques par son geoscience. He contributed consistently careful and travail soigne et meticuleux, en particulier dans le domaine de la meticulous scientific work to the literature, particu ­ geochronologie basee sur les methodes 40Ar-39Ar, Rb-Sr et U-Pb, larly in the fields of 40Ar-39Ar, Rb-Sr, and U-Pb geo­ sans oublier son apport aux techniques de mesure isotopique faisant chronology, and to the art of isotopic measurement appel aux spectrometres de masse modemes. Chris a congu l’utili- using modem mass spectrometers. Chris conceived the sation du diagramme de correlation avec 1’argon, qui permet 1’iden ­ use of the argon correlation diagram, which allows tification de composantes etrangeres contenant de l’argon a identification of extraneous argon components within I’interieur d ’echantillons de mineraux chauffes par etapes, une step-heated mineral samples, a method of argon data methode d ’analyse des donnees relatives a cet element qui est analysis that is a standard procedure today. During the d ’usage courant aujourd ’hui. Au cours des quelques demieres last few years, efforts by Chris and colleagues in the annees, les efforts de Chris et de ses collegues du laboratoire ont argon laboratory were focused on modernizing first the vise a moderniser d ’abord la methode K-Ar, puis la methode 40Ar- K-Ar, and later the 40Ar-39Ar methodologies using a 39Ar, en utilisant un four a double vide et a faible degre de contami ­ low-blank double vacuum furnace and spot fusion nation et en effectuant des analyses par fusion ponctuelle a l’aide analyses with a laser. Chris was also the backbone of du laser. Chris a aussi joue un role de pilier dans le domaine des computation and data management within the labora­ calculs et de la gestion des donnees au sein du laboratoire, concevant tory, designing and writing computer code not only to et ecrivant des programmes informatiques, non seulement pour efficiently collect and store isotopic data in 40Ar-39Ar, recueillir et stocker efficacement des donnees isotopiques d ’analyse U-Pb, Rb-Sr, and Sm-Nd methods, but also to facilitate par les methodes 40Ar-39Ar, U-Pb, Rb-Sr et Sm-Nd, mais aussi pour tabulation and presentation of isotopic analytical data faciliter la mise en tableaux et la presentation de donnees iso­ in a system that ranks among the best. He was also the topiques dans un systeme qui figure parmi les meilleurs. II etait aussi source of definitive advice and information on princi ­ une source d ’avis formel et d ’informations concernant les principes ples of measurement and interpretation of radiogenic de mesure et d ’interpretation pour ce qui est de la methode basee v isotope science and its related uncertainties. For these sur les isotopes radiogeniques et des incertitudes qui s’y rattachent. contributions and his generosity and enthusiasm, he Son absence sera profondement ressentie pour toutes ces raisons, will be dearly missed. mais aussi parce qu’il savait etre generaux et transmettre son enthousiasme. D’autres transitions ont eu lieu, notamment les departs de Other