515                 Detrital zircon geochronology and provenance of                 Devono-Mississippian strata in the nor...
516                                                                                              Can. J. Earth Sci. Vol. 4...
Lemieux et al.                                                                                                            ...
Fig. 2. Simplified geological map (modified after Hadlari et al. 2009) of southern Peel Plateau and Peel Plain, and the no...
Lemieux et al.                                                                                                            ...
520                                                                                            Can. J. Earth Sci. Vol. 48,...
Lemieux et al.                                                                                                            ...
522                                  Table 1. U–Pb data of detrital zircons.                                              ...
Lemieux et al.                                  Table 1 (continued).                                                      ...
524                                  Table 1 (continued).                                                         Isotopic...
Lemieux et al.                                  Table 1 (continued).                                                      ...
526                                  Table 1 (continued).                                                         Isotopic...
Lemieux et al.                                  Table 1 (continued).                                                      ...
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Lemieux et al 2011 devonian d zr peel
Upcoming SlideShare
Loading in...5
×

Lemieux et al 2011 devonian d zr peel

884

Published on

Detrital Zircon geochronology of the devonian clastic wedge of northern Canada.

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
884
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
2
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Lemieux et al 2011 devonian d zr peel

  1. 1. 515 Detrital zircon geochronology and provenance of Devono-Mississippian strata in the northern Canadian Cordilleran miogeocline1,2 Yvon Lemieux, Thomas Hadlari, and Antonio Simonetti Abstract: U–Pb ages have been determined on detrital zircons from the Upper Devonian Imperial Formation and Upper Devonian – Lower Carboniferous Tuttle Formation of the northern Canadian Cordilleran miogeocline using laser ablation – multicollector – inductively coupled plasma – mass spectrometry. The results provide insights into mid-Paleozoic sediment dispersal in, and paleogeography of, the northern Canadian Cordillera. The Imperial Formation yielded a wide range of de- trital zircon dates; one sample yielded dominant peaks at 1130, 1660, and 1860 Ma, with smaller mid-Paleozoic (*430 Ma), Neoproterozoic, and Archean populations. The easternmost Imperial Formation sample yielded predominantly late Neoproterozoic – Cambrian zircons between 500 and 700 Ma, with lesser Mesoproterozoic and older populations. The age spectra suggest that the samples were largely derived from an extensive region of northwestern Laurentia, including the Canadian Shield, igneous and sedimentary provinces of Canada’s Arctic Islands, and possibly the northern Yukon. The pres- ence of late Neoproterozoic – Cambrian zircon, absent from the Laurentian magmatic record, indicate that a number of grains were likely derived from an exotic source region, possibly including Baltica, Siberia, or Arctic Alaska – Chukotka. In contrast, zircon grains from the Tuttle Formation show a well-defined middle Paleoproterozoic population with dominant relative probability peaks between 1850 and 1950 Ma. Additional populations in the Tuttle Formation are mid-Paleozoic (*430 Ma), Mesoproterozoic (1000–1600 Ma), and earlier Paleoproterozoic and Archean ages (>2000 Ma). These data lend support to the hypothesis that the influx of sediments of northerly derivation that supplied the northern miogeocline in Late Devonian time underwent an abrupt shift to a source of predominantly Laurentian affinity by the Mississippian. ´ ´ ˆ ´´ ´ ´ ´ ` Resume : Des ages U–Pb ont ete determines par spectrometrie de masse a plasma inductif avec multicollecteur apres abla-` ´ ´ ´ tion au laser sur des zircons detritiques provenant de la Formation Imperial (Devonien superieur) et de la Formation Tuttle ´ ` ´ ´ ` ´ (Devonien – Carbonifere inferieur) du miogeoclinal de la Cordillere canadienne septentrionale. Les resultats fournissent des ´ ´ ¨ ´ ´ ` apercus de la dispersion des sediments au Paleozoıque moyen et de la paleogeographie de la Cordillere canadienne septen- ¸ ´ ´ ´ trionale. La Formation Imperial a donne une grande plage de dates sur des zircons detritiques; un echantillon a donne des´ ` ´ ¨ pics dominants a 1130, 1660 et 1860 Ma ainsi que des populations moindres datant du Paleozoıque moyen (*430 Ma), du ´ ´ ¨ ´ ´ ` ´ Neoproterozoıque et de l’Archeen. L’echantillon le plus a l’est de la Formation Imperial a donne des zircons datant surtout ´ ´ ¨ ´ du Neoproterozoıque tardif – Cambrien, soit entre 500 et 700 Ma, avec des populations moindres datant du Mesoprotero- ´ ¨ ˆ ` ´ ´ zoıque et plus anciennes. Les plages d’ages suggerent que les echantillons proviennent surtout d’une region extensive dans le nord-ouest de la Laurentie, incluant le Bouclier canadien, les provinces ignees et sedimentaires des ˆles de l’Arctique ca- ´ ´ ı ´ ´ ´ ¨ nadien et possiblement du nord du Yukon. La presence de zircons datant du Neoproterozoıque tardif – Cambrien, lesquels ´ sont absents des donnees magmatiques laurentiennes, indique qu’un certain nombre de grains proviennent sans doute d’une ´ ´ region source exotique, possiblement de Baltica, de la Siberie ou du terrane Arctic Alaska – Chukotka. Cependant, les zir- ´ ´ ´ ¨ cons provenant de la Formation Tuttle montrent une population bien definie du Paleoproterozoıque moyen avec des pics de ´ ´ ¨ probabilite relative entre 1850 et 1950 Ma. D’autres populations dans la Formation Tuttle datent du Paleozoıque moyen ´ ´ ¨ ´ ´ ¨ ´ ´ (*430 Ma), du Mesoproterozoıque (1000–1600 Ma) ainsi que du Paleoproterozoıque inferieur et de l’Archeen (>2000 Ma). ´ ` ´ ´ Ces donnees supportent l’hypothese que l’influx de sediments provenant du Nord qui a fourni le miogeoclinal septentrional ´ ´ au Devonien tardif a subi un changement abrupt vers une source d’affinite surtout laurentienne vers le Mississippien. ´ [Traduit par la Redaction] Received 23 November 2009. Accepted 26 May 2010. Published on the NRC Research Press Web site at cjes.nrc.ca on 9 February 2011. Paper handled by Associate Editor W.J. Davis. Y. Lemieux and T. Hadlari.3,4 Northwest Territories Geoscience Office, Box 1500, 4601-B, 52 Avenue, Yellowknife, NT X1A 2R3, Canada. A. Simonetti.5 Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Building, Edmonton, AB T6G 2E3, Canada. 1This article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh. 2Northwest Territories Geoscience Office Contribution 0047. Geological Survey of Canada Contribution 20100432. 3Corresponding author (e-mail: thomas.hadlari@nrcan-rncan.gc.ca). 4Present address: Geological Survey of Canada, 3303, 33rd St. NW, Calgary, AB T2L 2A7, Canada. 5Present address: 156 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556.Can. J. Earth Sci. 48: 515–541 (2011) doi:10.1139/E10-056 Published by NRC Research Press
  2. 2. 516 Can. J. Earth Sci. Vol. 48, 2011Introduction folded miogeoclinal strata are exposed at the mountain front. The area preserves a relatively complete Cambrian to Dev- Despite an increasing number of U–Pb geochronology and onian, rift to post-rift passive-margin succession that liesNd isotopic studies that provided new perspectives on re- with a pronounced unconformity on a thick succession ofgional patterns of sediment dispersal in northwestern Canada Proterozoic sedimentary rock (Fig. 3; Aitken et al. 1982). Aand adjacent Arctic region in Paleozoic time (e.g., McNicoll wedge of Cretaceous siliciclastic strata, interpreted to haveet al. 1995; Garzione et al. 1997; Gehrels et al. 1999; Patch- been deposited in a foreland basin setting, overlies the Pale-ett et al. 1999; Miller et al. 2006), the tectonic setting and ozoic succession.paleogeography during deposition of the Devono-Mississip- In Cambrian to Middle Devonian time, the northern Cana-pian succession in the northern Canadian Cordilleran mio- dian Cordilleran miogeocline was a continental margingeocline is not well understood. marked by deposition of extensive carbonate platform and Prior to the late Devonian, the northern Cordilleran mar- minor associated siliciclastic rocks (Mackenzie Platform;gin was dominated by an extensive shallow-water carbonate Fritz et al. 1991), and, to the west, deeper water siliciclasticplatform thickening markedly westward toward a fine- and minor carbonate succession (Fig. 3; Pugh 1983). Detritalgrained basinal succession (e.g., Fritz et al. 1991). The plat- zircon ages from Cambrian sandstone in east-central Alaskaform was flanked to the east by the Laurentian Precambrian suggest provenance largely from regions of the CanadianShield, which provided most of the sediment for the clastic Shield (Gehrels et al. 1999).deposits (Gordey et al. 1991). By the late Devonian, an in- In the late Devonian, passive-margin sedimentation wasflux of fine siliciclastic sediment blanketed the northern interrupted by a major change in tectono-sedimentologicalshelf and platform, marking a profound change in depositio- elements with uplift of clastic sourcelands north and west ofnal regime and tectonic setting along the Cordilleran margin the platform and influx of thick wedges of coarse and fine(Morrow and Geldsetzer 1988). In northern Yukon and clastic sediments (Pugh 1983; Gordey et al. 1991). TheNorthwest Territories, the Middle Devonian to Early Car- Upper Devonian Imperial Formation (Bassett 1961), mark-boniferous Imperial Assemblage, including the Hare Indian, ing the transition from carbonate to sand-grade siliciclasticCanol, Imperial, Tuttle, and Ford Lake formations, was in- deposition in the northern miogeocline (e.g., Gordey et al.terpreted by Gordey et al. (1991) to have been derived from 1991), includes a thick sequence of marine shale, siltstone,an uplifted region in northern Yukon. On the basis of Nd and very fine- to fine-grained sandstone that overlies blackisotopic constraints, Garzione et al. (1997) and Patchett et siliceous shale of the Canol Formation. Within the studyal. (1999) argued that the Imperial Assemblage was likelyderived from Ordovician to Early Carboniferous orogenic area, the Imperial Formation has been interpreted as Fras-systems in Greenland and the Canadian Arctic, as proposed nian–Famennian shelf sandstones and basinal turbidites withby Embry and Klovan (1976). More recently, detailed sedi- an eastward or northeastward sediment source inferred frommentology of the Upper Devonian Imperial Formation and outcrop studies (Braman and Hills 1992), and as a west- toTuttle Formation (Hadlari et al. 2009) indicated derivation southwestward-prograding submarine slope and fan complexfrom a northeastern and eastern source region. (Hadlari et al. 2009). To the north and west, the Imperial Formation is composed of turbidites interpreted to have Paleozoic sediment dispersal in the northern Cordillera been derived largely from northern source regions (Gordeycan be better constrained with detrital zircon geochronology et al. 1991; Braman and Hills 1992). Seventeen single zircondata. Few U–Pb detrital zircon studies have been carried out dates from the Imperial Formation in northwestern Yukonin strata of the miogeocline in the northern Canadian Cordil- (C. Garzione, G. Ross, J. Patchett, and G. Gehrels unpub-lera (e.g., Beranek et al. 2010). In this paper, we present lished data, discussed in Gehrels et al. 1999) indicated anew U–Pb detrital zircon dates obtained using laser ablation dominance of >1.8 Ga detritus, consistent with derivation– multicollector – inductively coupled plasma – mass spec- from Canadian Shield sources, with a subordinate populationtrometry (LA–MC–ICP–MS) from the Upper Devonian Im- of mid-Paleozoic (400–450 Ma) grains. Single zircon grainsperial Formation and Upper Devonian – LowerCarboniferous Tuttle Formation exposed in the northern from a Late Devonian sandstone-bearing unit in east-centralMackenzie Mountains (Figs. 1, 2). The purpose of the study Alaska yielded chiefly 430 Ma, Paleoproterozoic (>1.8 Ga),is to constrain the provenance of sandstones within these and Archean grains, consistent with an influx of detritus, intwo units to better understand regional patterns of mid-Pale- part, from Laurentian source regions (Gehrels et al. 1999).ozoic sediment dispersal in the northern Cordillera and to Similar results have been reported from Devonian to Car-draw conclusions regarding paleogeography of northern boniferous sandstones of northeastern Yukon Territory (Be-Laurentia. As our data indicate, the zircons from the Impe- ranek et al. 2010).rial and Tuttle formations were likely derived from an ex- East of Arctic Red River (see Fig. 2 for location), Impe-tensive region of northern Laurentia, including the rial Formation is unconformably overlain by wedge of Cre-northwestern Canadian Shield, provinces of Canada’s Arctic taceous clastic sediments deposited in a foreland basinIslands, and Greenland. setting (Aitken et al. 1982); west of Arctic Red River, how- ever, the Imperial Formation is conformably overlain by the Upper Devonian – Lower Carboniferous Tuttle Formation, aGeological setting thick succession of alternating conglomerate, coarse- to fine- The study area lies along the northern margin of the grained sandstone, siltstone, and shale. The contact with theMackenzie Mountains and encompasses the southern Peel Imperial Formation is interpreted as a facies boundary and,Plateau and Plain (Peel Region) of the northern Interior therefore, is diachronous (Pugh 1983). Hills and BramanPlains (Figs. 2); it occupies a region where imbricated and (1978) and Braman and Hills (1992) interpreted the Tuttle Published by NRC Research Press
  3. 3. Lemieux et al. 517Fig. 1. Tectonic assemblage map of Yukon Territory, Northwest Territories and Nunavut showing location of study area and Fig. 2. Geol-ogy after Wheeler et al. (1996), paleocurrent data from Embry and Klovan (1976) and Hadlari et al. (2009).Formation as a southward-advancing turbidite succession. In The sub-Cretaceous unconformity marks a hiatus in thecontrast, Pugh (1983) viewed the unit as a deltaic depositio- sedimentary record as Late Carboniferous to Jurassic stratanal system and interpreted the shale-out to the west as indi- are absent from the northern Interior Plains. The end of con-cating southwest-prograding deposition despite a progressive tinental margin sedimentation and beginning of widespreadsouthward decrease in grain size and trend to better sorting. compressional deformation in the northern Cordillera inBy the mid-Mississippian, marine clastic and carbonate dep- Mesozoic time (e.g., Berman et al. 2007) influenced the de-osition with sediment derivation from the craton to the east velopment of foreland basins adjacent to the mountain frontwas re-established (Gordey et al. 1991). (Dixon 1999). Clastic sedimentation in the northern Interior Published by NRC Research Press
  4. 4. Fig. 2. Simplified geological map (modified after Hadlari et al. 2009) of southern Peel Plateau and Peel Plain, and the northern Mackenzie Mountains showing seismic line traces and 518 clinoform progradation directions, turbidite paleocurrents, and locations of the detrital zircon samples. Geology after Wheeler et al. (1996).Published by NRC Research Press Can. J. Earth Sci. Vol. 48, 2011
  5. 5. Lemieux et al. 519Fig. 3. Schematic stratigraphic section for the southern Peel Plateau and Peel Plain and northern Mackenzie Mountains. Modified afterMorrow et al. (2006). Published by NRC Research Press
  6. 6. 520 Can. J. Earth Sci. Vol. 48, 2011Plains in the Late Cretaceous was controlled largely by, and large enough (i.e., > 40 mm across, see as follows) for laserderived from, the active Cordillera to the south and west ablation analyses. In contrast, the much finer grained Impe-(Dixon 1999). rial samples yielded a smaller fraction of zircons that were sufficiently large for analysis. Selected grains were, asU–Pb geochronology much as possible, free of fractures, inclusions, and altera- tion. U–Pb geochronology of zircons was conducted bySample description and analytical procedures LA–MC–ICP–MS at the Radiogenic Isotope Facility at the This study presents U–Pb geochronological results for University of Alberta, Edmonton, Alberta, using analyticalfour samples from the Devono-Mississippian clastic succes- procedures described by Simonetti et al. (2005). The analy-sion in the Peel Region, two from the Imperial Formation ses involved ablation of zircons using a 40 mm diameter la-(samples 07TH33B and 07WZ020A), and two from the Tut- ser spot size for 30 s. A ‘‘standard-sample-standard’’ methodtle Formation (samples 07WZ019A and 06YHL046B); their was used to correct instrumental drift during a single lasergeographic locations are shown in Fig. 2 and given in ablation session and involved analysis of an internal stand-Table 1. ard after every 12 unknown grains; this protocol was devel- Sample 07TH33B was collected at the type section of Im- oped for provenance studies focusing on the dating of aperial Formation (Fig. 2). Located near the eastern erosional large number of detrital zircon grains (Simonetti et al.edge of Imperial Formation, the type section preserves the 2005) The collector configuration allows for the simultane-oldest strata of Imperial Formation, which were deposited ous measurement of ion signals ranging in mass from 238Uas a shallow shelf-like accumulation of sediment that pro- to 203Tl. Periodically, a 30 s blank measurement was per-graded southwestward into a generally westward-deepening formed, which included correction for the 204Hg contribu-basin (Hadlari et al. 2009). The sampled interval consists of tion; ion-counter bias was also determined using a mixedfine-grained cross-stratified sandstone from the locally de- solution of Pb and Tl. Common Pb correction was appliedveloped shallow-marine facies. using an initial Pb composition taken from Stacey and West of Imperial River, the Imperial Formation is inter- Kramers (1975).preted as a succession of submarine fan and slope sand-stones and shales exceeding 500 m in thickness that, based Results of U–Pb analysisupon paleocurrent and seismic data, are interpreted to have The results are presented in Table 1 (with uncertainties atbeen deposited by a system that prograded in a west-south- the 2s level) and shown in relative age–probability diagramswest direction (Hadlari et al. 2009). Tuttle Formation is gen- (from Ludwig 2003) in Fig. 5. The diagrams present the sumerally Famennian to Tournasian in age (Allen et al. 2009), of all ages from a sample as a normal distribution based onoverlies the Imperial Formation, is partly defined by me- the age and uncertainty of each analysis, the areas underdium sand and coarser grain sizes, and represents a rejuve- each curve are equal. Interpretations for <1000 Ma grainsnation of sand-grade siliciclastic input to the basin from the are based on 206Pb/238U ages, which yield more precise re-northeast (Hadlari et al. 2009). Based upon the depositional sults given the low concentration of 207Pb in younger zir-system, the three remaining samples are significantly cons. For grains >1000 Ma, analyses are based on 207Pb/younger than 07TH33B because they are located over 206Pb ages. To reduce the effect of discordance, possibly re-100 km west of Imperial River. Considering their mutual sulting from isotopic disturbance and (or) inheritance, analy-proximity, we have placed the three western samples in or- ses that are >5% discordant or >5% reverse discordantder by the stratigraphic level that was sampled within the (italics in Table 1) have been excluded from further consid-combined Imperial–Tuttle formation section. Sample eration.07WZ020A, a massive fine-grained sandstone, was collected A total of 67 zircons were analyzed from samplea few metres above the Canol–Imperial contact along a trib- 07TH33B (Imperial Formation), of which 54 were consid-utary of the Snake River near the western edge of the study ered (Fig. 5; Table 1). A significant number of zirconsarea. From the middle part of the section, sample yielded age clusters between 380 and 711 Ma (n = 26),06YHL046B was collected from a *150 m high bluff of with peaks evident at 390, 555, and 670 Ma. Twenty-fiveconspicuously hard and massive, medium- to coarse-grained, zircons yielded Proterozoic dates, with the most dominantquartz-rich sandstone sharply overlying shale and siltstone peaks at 1100, 1350, 1670, and 1950 Ma; only one zirconwest of Cranswick River (Fig. 4). Although the bluff was falls in the interval 2100–2500 Ma. Three Archean zirconsmapped as Imperial Formation by Norris (1982), the grain were documented (i.e., 2625, 2796, and 2820 Ma).size is clearly atypical of Imperial Formation, and is inter- Ninety-one zircons extracted from the westernmost sam-preted here as part of Tuttle Formation. Sample 07WZ019A ple of the Imperial Formation (07WZ020A) were analyzed,is conglomerate of Tuttle Formation from the top of the Im- of which 61 are within 5% of the concordia. This sampleperial–Tuttle section at Flyaway Creek; the section exposes has a dominant zircon age population (n = 46) betweena thin interval, *50 m thick, of sandstone and conglomerate *1000 and 2100 Ma, with major peaks at 1130, 1660, andoverlying *600 m in thickness of Imperial Formation (Ha- 1860 Ma, and subordinate age groups at 1300–1550, 1730–dlari et al. 2009). The entire sample of quartz clast conglom- 1800, 1900–2100 Ma. The sample also includes (i) fourerate with sandstone matrix was crushed for analysis. lower Paleozoic zircons at 424, 432, 438, and 505 Ma; (ii) Each sample yielded euhedral to anhedral, colourless to four Neoproterozoic grains at 570, 597, 645, and 855 Ma;pink or yellow, generally well-rounded zircons consistent and (iii) seven Archean zircons between 2614 and 2806 Ma.with a detrital origin. Samples from the Tuttle Formation There is a gap between 2100 and 2600 Ma.were sufficiently coarse grained to yield abundant zircons Ninety-one zircon were analyzed from sample Published by NRC Research Press
  7. 7. Lemieux et al. 521Fig. 4. (a) Field photograph showing the contact between the Imperial Formation and overlying Tuttle Formation in the Cranswick Riverarea. The bluff (in the middle ground) was mapped as Imperial Formation by Norris (1982). View to northeast; field of view in middleground is *4 km. (b) Close-up of approximate contact (dashed line) between the Imperial and Tuttle formations. Geologist for scale. SeeFig. 2 for location of photographs.06YHL046B (Tuttle Formation); 18 zircon have not been 1512 Ma (n = 2), and 1597–1731 Ma (n = 5). One grainconsidered further. A 440 Ma Silurian-age peak is evident, yielded a Neoproterozoic date (940 Ma).represented by seven grains between 428 and 444 Ma. The A total of 112 zircons were analyzed from samplesample yielded 45 grains between *1800 and 2800 Ma, 07WZ019A (Tuttle Formation), of which 99 were consid-with dominant age peaks at 1860 and 2780 Ma, and subordi- ered. A 1937 Ma Paleoproterozoic age peak is evident innate age groups between *2000 and 2700 Ma. Twenty zir- the zircon population, with 50 grains falling in the intervalcons fall in the intervals 1038–1366 Ma (n = 13), 1494– 1792–2000 Ma; a subordinate age cluster occurs at 430 Ma, Published by NRC Research Press
  8. 8. 522 Table 1. U–Pb data of detrital zircons. Isotopic ratios Apparent ages (Ma) 206Pb 206 Pb 207 Pb 206 Pb Err. 206 Pbà ± 207 Pbà 207 Pbà Disc. Grain # (cps) 204 Pb 235 U ± (2s) 238 U ± (2s) corr. 238 U (2s) 235 U ± (2s) 206 Pbà ± (2s) (%) Sample 07TH33B (UTM ZONE 9N, N7221831, E553690) 1 217352 Infinite 0.4578 0.012 0.0607 0.002 0.96 380 15 383 10 368 25 –3.1 2 266037 29559.7 0.4382 0.008 0.0585 0.001 0.92 366 13 369 7 370 32 0.8 3 97534 Infinite 0.4601 0.006 0.0600 0.001 0.93 376 12 384 5 393 27 4.3 4 141527 Infinite 0.4855 0.010 0.0629 0.001 0.91 393 14 402 8 409 34 3.8 5 105463 Infinite 0.4873 0.009 0.0629 0.001 0.90 393 13 403 7 409 34 3.8 6 116583 Infinite 0.4960 0.012 0.0644 0.001 0.95 402 15 409 10 413 27 2.6 7 87935 Infinite 0.4998 0.014 0.0649 0.002 0.91 405 15 412 11 416 37 2.6 8 57814 Infinite 0.5677 0.013 0.0724 0.002 0.94 451 16 457 10 422 29 -6.8 9 57549 Infinite 0.5629 0.011 0.0716 0.001 0.93 446 15 453 9 425 29 –4.8 10 191304 Infinite 0.5751 0.009 0.0734 0.001 0.95 457 15 461 7 451 23 –1.2 11 204407 Infinite 0.4615 0.013 0.0582 0.002 0.95 365 15 385 11 476 29 23.4 12 325769 Infinite 0.6521 0.015 0.0809 0.002 0.95 501 19 510 12 518 26 3.3 13 61741 Infinite 0.7202 0.019 0.0883 0.002 0.96 545 22 551 15 521 26 –4.6 14 193746 Infinite 0.7096 0.016 0.0863 0.002 0.94 533 20 544 12 556 29 4.0 15 109660 Infinite 0.7400 0.016 0.0897 0.002 0.96 554 20 562 12 559 24 1.0 16 202468 Infinite 0.7514 0.022 0.0907 0.003 0.97 560 24 569 17 564 24 0.8 17 340492 Infinite 0.7230 0.014 0.0878 0.002 0.93 542 19 552 11 567 28 4.3 18 141712 4571.37 0.6721 0.039 0.0810 0.004 0.92 502 30 522 30 575 57 12.7 19 134699 33674.67 0.7638 0.021 0.0917 0.002 0.94 565 22 576 16 584 29 3.3 20 296319 Infinite 0.7744 0.014 0.0931 0.002 0.95 574 20 582 10 593 24 3.2 21 229189 Infinite 0.7777 0.017 0.0931 0.002 0.95 574 21 584 13 596 25 3.6 22 278753 25341.2 0.6959 0.020 0.0830 0.002 0.93 514 20 536 15 605 32 15.0 23 417489 Infinite 0.7199 0.016 0.0863 0.002 0.96 534 20 551 12 606 23 11.9 24 365918 Infinite 0.9035 0.017 0.1043 0.002 0.94 640 22 654 12 670 25 4.5 25 203291 Infinite 0.8012 0.020 0.0918 0.002 0.93 566 21 598 15 670 30 15.5 26 100302 Infinite 0.9362 0.022 0.1071 0.002 0.94 656 24 671 16 675 29 2.8 27 273595 Infinite 0.9270 0.025 0.1091 0.003 0.96 667 27 666 18 677 23 1.4 28 188263 Infinite 0.9401 0.020 0.1078 0.002 0.95 660 24 673 14 679 25 2.8 29 227461 10831.45 0.9981 0.052 0.1146 0.005 0.91 699 39 703 37 684 54 –2.2 Can. J. Earth Sci. Vol. 48, 2011 30 278435 Infinite 0.9515 0.017 0.1096 0.002 0.96 670 23 679 12 698 22 4.0Published by NRC Research Press 31 312369 Infinite 0.8629 0.033 0.0991 0.004 0.97 609 30 632 24 702 24 13.2 32 165271 Infinite 0.9856 0.026 0.1107 0.003 0.96 677 27 696 18 707 24 4.3 33 217427 Infinite 1.0312 0.015 0.1166 0.001 0.91 711 23 720 11 717 29 0.9 34 227825 28478.1 0.9579 0.023 0.1031 0.002 0.94 633 24 682 16 819 28 22.8 35 71442 Infinite 1.6142 0.031 0.1607 0.003 0.93 961 33 976 19 953 27 –0.8 36 102579 Infinite 1.9582 0.060 0.1866 0.006 0.97 1103 47 1101 34 1059 21 –4.2 37 725341 Infinite 1.4684 0.041 0.1403 0.004 0.93 846 33 917 26 1084 31 21.9 38 259436 Infinite 1.9815 0.037 0.1867 0.003 0.95 1103 39 1109 21 1095 22 –0.8 39 198957 Infinite 1.9575 0.051 0.1833 0.005 0.96 1085 43 1101 28 1097 21 1.1
  9. 9. Lemieux et al. Table 1 (continued). Isotopic ratios Apparent ages (Ma) 206Pb 206 Pb 207 Pb 206 Pb Err. 206 Pbà ± 207 Pbà 207 Pbà Disc. Grain # (cps) 204 Pb 235 U ± (2s) 238 U ± (2s) corr. 238 U (2s) 235 U ± (2s) 206 Pbà ± (2s) (%) 40 802664 21693.62 1.9697 0.045 0.1865 0.004 0.93 1102 40 1105 25 1106 28 0.3 41 224638 1936.534 1.8174 0.064 0.1809 0.006 0.92 1072 47 1052 37 1118 36 4.1 42 1011788 2007.516 2.4696 0.224 0.2155 0.019 0.98 1258 119 1263 114 1272 33 1.1 43 243064 Infinite 2.1622 0.178 0.1784 0.014 0.97 1058 91 1169 96 1330 38 20.4 44 607082 530.203 2.5457 0.133 0.2178 0.010 0.91 1270 71 1285 67 1333 49 4.7 45 522574 Infinite 2.6736 0.083 0.2244 0.007 0.97 1305 56 1321 41 1341 20 2.6 46 1073922 Infinite 2.6708 0.062 0.2241 0.005 0.96 1304 49 1320 31 1345 20 3.1 47 114935 Infinite 2.8172 0.049 0.2294 0.004 0.93 1332 45 1360 24 1374 25 3.1 48 385586 16764.6 2.7961 0.049 0.2198 0.003 0.91 1281 42 1355 24 1452 27 11.8 49 1398896 Infinite 3.3621 0.044 0.2658 0.003 0.95 1519 50 1496 20 1487 19 –2.1 50 1668858 Infinite 2.6855 0.035 0.1994 0.002 0.93 1172 38 1324 17 1555 22 24.6 51 505990 Infinite 4.3155 0.105 0.3056 0.007 0.97 1719 66 1696 41 1659 19 –3.6 52 1627787 Infinite 3.9893 0.076 0.2831 0.005 0.96 1607 57 1632 31 1670 19 3.8 53 630839 Infinite 4.2327 0.086 0.2952 0.006 0.96 1668 60 1680 34 1688 19 1.2 54 488924 Infinite 4.6379 0.339 0.3078 0.021 0.94 1730 129 1756 128 1727 51 –0.2 55 840928 Infinite 4.6572 0.069 0.3100 0.005 0.95 1741 58 1760 26 1779 19 2.1 56 200124 939.5515 5.5286 0.415 0.3341 0.025 0.97 1858 148 1905 143 1893 33 1.8 57 481859 Infinite 5.7437 0.120 0.3505 0.007 0.96 1937 71 1938 40 1929 19 –0.4 58 673729 2029.306 5.7164 0.107 0.3497 0.006 0.95 1933 68 1934 36 1935 20 0.1 59 933238 Infinite 5.6258 0.080 0.3369 0.005 0.95 1872 62 1920 27 1968 18 4.9 60 966251 Infinite 6.2317 0.095 0.3725 0.006 0.95 2041 69 2009 31 1976 18 –3.3 61 1716228 17693.07 6.2476 0.108 0.3704 0.006 0.94 2031 69 2011 35 2011 22 –1.0 62 883413 Infinite 5.9951 0.114 0.3495 0.007 0.96 1932 68 1975 37 2021 18 4.4 63 322605 1097.296 7.6982 0.196 0.3990 0.010 0.95 2164 83 2196 56 2206 22 1.9 64 1093494 Infinite 11.6411 0.170 0.4771 0.007 0.95 2515 84 2576 38 2625 17 4.2 65 1548221 30964.42 14.8244 0.277 0.5507 0.010 0.96 2828 100 2804 52 2796 17 –1.1 66 390767 Infinite 15.4936 0.348 0.5625 0.013 0.96 2877 108 2846 64 2820 17 –2.0 67 3034842 35704 10.4927 0.353 0.3826 0.013 0.97 2089 94 2479 83 2832 17 26.2 Sample 07WZ020A (UTM Zone 9N, N7277599, E308503) 1 126733 Infinite 0.5336 0.015 0.0693 0.002 0.96 432 18 434 12 420 25 –2.8 2 340726 Infinite 0.5227 0.008 0.0679 0.001 0.95 424 14 427 6 441 23 3.9Published by NRC Research Press 3 259160 Infinite 0.5501 0.011 0.0703 0.001 0.96 438 16 445 9 454 24 3.6 4 297800 Infinite 0.4928 0.007 0.0623 0.001 0.94 390 13 407 6 483 24 19.3 5 699418 Infinite 0.4709 0.012 0.0584 0.001 0.94 366 14 392 10 516 30 29.1 6 357235 238.9533 0.6515 0.083 0.0815 0.010 0.97 505 64 509 65 525 70 3.8 7 371429 Infinite 0.5386 0.013 0.0664 0.002 0.94 414 16 437 10 529 28 21.7 8 256729 Infinite 0.7658 0.016 0.0925 0.002 0.96 570 21 577 12 582 24 1.9 9 109026 Infinite 0.8092 0.018 0.0970 0.002 0.94 597 22 602 13 587 28 –1.6 10 433467 Infinite 0.6441 0.012 0.0775 0.001 0.96 481 17 505 9 595 23 19.2 11 181581 Infinite 0.9039 0.011 0.1052 0.001 0.95 645 21 654 8 656 23 1.7 523
  10. 10. 524 Table 1 (continued). Isotopic ratios Apparent ages (Ma) 206Pb 206 Pb 207 Pb 206 Pb Err. 206 Pbà ± 207 Pbà 207 Pbà Disc. Grain # (cps) 204 Pb 235 U ± (2s) 238 U ± (2s) corr. 238 U (2s) 235 U ± (2s) 206 Pbà ± (2s) (%) 12 1016871 3697.711 1.3405 0.048 0.1418 0.005 0.96 855 39 863 31 887 26 3.6 13 158487 Infinite 1.6375 0.030 0.1613 0.003 0.95 964 34 985 18 996 22 3.2 14 753417 39653.5 1.7187 0.044 0.1676 0.004 0.96 999 39 1016 26 1044 23 4.3 15 972131 Infinite 1.8740 0.032 0.1789 0.003 0.96 1061 37 1072 18 1091 20 2.7 16 555233 Infinite 1.8900 0.064 0.1790 0.006 0.96 1061 47 1078 36 1097 25 3.3 17 1298874 4071.706 1.8714 0.132 0.1781 0.012 0.94 1056 76 1071 75 1101 53 4.1 18 202173 Infinite 2.0020 0.037 0.1871 0.003 0.94 1106 38 1116 21 1115 24 0.8 19 334811 Infinite 2.0319 0.042 0.1902 0.004 0.96 1122 41 1126 23 1115 21 –0.6 20 85633 Infinite 2.0206 0.036 0.1856 0.003 0.93 1097 37 1122 20 1130 25 2.9 21 433460 Infinite 2.0282 0.043 0.1890 0.004 0.96 1116 41 1125 24 1134 21 1.6 22 135092 Infinite 2.0534 0.056 0.1873 0.005 0.95 1107 44 1133 31 1154 25 4.1 23 393360 19668 2.1728 0.042 0.1995 0.003 0.92 1173 40 1172 23 1161 28 –1.0 24 158101 Infinite 2.2812 0.022 0.2067 0.001 0.93 1211 37 1206 11 1166 24 –3.9 25 457060 Infinite 1.6001 0.087 0.1451 0.008 0.97 874 54 970 53 1168 27 25.2 26 1110968 Infinite 1.6735 0.014 0.1527 0.001 0.94 916 28 999 8 1185 21 22.7 27 1177595 Infinite 2.1699 0.054 0.1985 0.005 0.97 1167 45 1171 29 1185 20 1.5 28 260928 Infinite 2.2472 0.063 0.2032 0.006 0.96 1192 49 1196 33 1186 22 –0.5 29 1078929 Infinite 2.3740 0.104 0.2117 0.009 0.97 1238 64 1235 54 1228 27 –0.8 30 166663 Infinite 2.3208 0.038 0.2022 0.003 0.95 1187 40 1219 20 1237 22 4.0 31 241826 Infinite 2.3165 0.064 0.2031 0.006 0.97 1192 48 1217 34 1243 21 4.1 32 393935 Infinite 2.2663 0.169 0.1945 0.013 0.92 1146 86 1202 90 1279 62 10.4 33 376764 1638.1 2.3487 0.076 0.1995 0.006 0.94 1173 50 1227 40 1304 30 10.0 34 395046 Infinite 2.5778 0.049 0.2173 0.004 0.94 1268 44 1294 25 1330 24 4.7 35 127330 Infinite 2.8597 0.065 0.2341 0.005 0.94 1356 50 1371 31 1366 24 0.8 36 236473 Infinite 2.5301 0.068 0.2065 0.005 0.96 1210 48 1281 34 1383 23 12.5 37 230817 Infinite 3.0753 0.044 0.2455 0.003 0.94 1415 47 1427 21 1402 21 –0.9 38 344399 Infinite 2.9715 0.050 0.2393 0.004 0.94 1383 47 1400 24 1411 22 2.0 39 441807 14726.89 3.2392 0.066 0.2544 0.004 0.91 1461 50 1467 30 1465 29 0.3 40 147977 Infinite 3.2981 0.066 0.2546 0.004 0.91 1462 50 1481 30 1474 28 0.8 41 669286 Infinite 3.3311 0.059 0.2585 0.005 0.95 1482 51 1488 26 1505 20 1.5 42 1296589 Infinite 3.4601 0.056 0.2636 0.004 0.96 1508 51 1518 24 1533 19 1.6 Can. J. Earth Sci. Vol. 48, 2011 43 491753 1576.13 3.0343 0.278 0.2285 0.019 0.92 1327 118 1416 130 1548 73 14.3Published by NRC Research Press 44 131575 Infinite 4.1502 0.081 0.2915 0.006 0.95 1649 59 1664 32 1649 20 0.0 45 228486 337.4977 4.3403 0.233 0.3062 0.015 0.94 1722 101 1701 91 1653 38 –4.2 46 321559 Infinite 3.9912 0.130 0.2809 0.009 0.97 1596 71 1632 53 1660 19 3.9 47 1031062 Infinite 4.0686 0.081 0.2883 0.006 0.96 1633 59 1648 33 1664 19 1.9 48 528558 Infinite 4.3359 0.084 0.3050 0.006 0.96 1716 61 1700 33 1669 19 –2.8 49 590211 Infinite 3.0786 0.314 0.2133 0.022 0.99 1246 132 1427 146 1684 30 26.0 50 600365 Infinite 4.3516 0.116 0.3040 0.008 0.97 1711 69 1703 45 1701 19 –0.6 51 593925 Infinite 3.8213 0.069 0.2633 0.005 0.96 1507 53 1597 29 1710 19 11.9
  11. 11. Lemieux et al. Table 1 (continued). Isotopic ratios Apparent ages (Ma) 206Pb 206 Pb 207 Pb 206 Pb Err. 206 Pbà ± 207 Pbà 207 Pbà Disc. Grain # (cps) 204 Pb 235 U ± (2s) 238 U ± (2s) corr. 238 U (2s) 235 U ± (2s) 206 Pbà ± (2s) (%) 52 728551 3223.678 4.3360 0.792 0.2943 0.053 0.99 1663 306 1700 310 1747 41 4.8 53 386808 16817.72 4.6421 0.095 0.3115 0.006 0.93 1748 62 1757 36 1748 24 0.0 54 624037 Infinite 4.6055 0.058 0.3077 0.004 0.95 1729 56 1750 22 1766 19 2.1 55 2324654 36899.3 4.0873 0.067 0.2723 0.004 0.95 1553 53 1652 27 1793 20 13.4 56 775421 2959.62 4.6605 0.150 0.3029 0.010 0.97 1706 75 1760 57 1825 20 6.5 57 456978 Infinite 4.2560 0.077 0.2740 0.005 0.96 1561 55 1685 31 1832 18 14.8 58 1267941 4103.37 3.6877 0.111 0.2384 0.007 0.95 1378 57 1569 47 1841 23 25.2 59 640904 Infinite 5.2003 0.111 0.3332 0.007 0.96 1854 68 1853 39 1848 18 –0.3 60 842510 Infinite 5.0816 0.084 0.3242 0.005 0.96 1810 62 1833 30 1854 18 2.4 61 449007 Infinite 5.2542 0.072 0.3332 0.005 0.95 1854 61 1861 26 1860 18 0.3 62 178341 Infinite 5.5673 0.102 0.3465 0.006 0.96 1918 67 1911 35 1870 19 –2.6 63 462742 Infinite 5.1635 0.121 0.3234 0.007 0.93 1807 66 1847 43 1875 26 3.7 64 2906290 10416.8 3.8769 0.187 0.2447 0.012 0.98 1411 80 1609 78 1892 18 25.4 65 878581 2670.46 4.1829 0.112 0.2585 0.006 0.93 1482 57 1671 45 1913 27 22.5 66 1133511 4048.255 5.6088 0.427 0.3423 0.023 0.90 1898 141 1917 146 1919 64 1.1 67 954093 Infinite 5.7962 0.078 0.3545 0.005 0.95 1956 64 1946 26 1931 18 –1.3 68 125954 Infinite 5.7371 0.118 0.3456 0.007 0.95 1914 68 1937 40 1934 21 1.0 69 276151 Infinite 5.8263 0.112 0.3524 0.007 0.96 1946 69 1950 37 1937 19 –0.5 70 661599 2584.37 4.8255 0.262 0.2931 0.014 0.91 1657 95 1789 97 1964 46 15.6 71 641871 Infinite 4.9901 0.230 0.2908 0.013 0.98 1646 90 1818 84 2005 19 17.9 72 628332 Infinite 6.2959 0.131 0.3659 0.008 0.96 2010 73 2018 42 2022 18 0.6 73 1454081 Infinite 5.8633 0.124 0.3421 0.007 0.96 1897 69 1956 41 2026 19 6.4 74 569035 Infinite 6.8134 0.148 0.3905 0.008 0.96 2125 79 2087 45 2041 18 –4.1 75 540218 13505.46 6.4420 0.141 0.3624 0.007 0.93 1994 72 2038 45 2072 24 3.8 76 2375359 Infinite 5.9257 0.104 0.3289 0.006 0.96 1833 64 1965 35 2117 18 13.4 77 763478 21813.7 7.6396 0.276 0.3721 0.013 0.97 2039 95 2190 79 2330 19 12.5 78 261215 4213.14 7.7344 0.778 0.3480 0.034 0.97 1925 197 2201 221 2442 42 21.2 79 1196610 10978.1 8.7709 0.263 0.3711 0.011 0.95 2035 85 2314 69 2576 21 21.0 80 1757086 Infinite 10.8700 0.261 0.4452 0.011 0.97 2374 91 2512 60 2607 17 9.0 81 593333 7510.545 12.4287 0.219 0.5121 0.007 0.90 2666 88 2637 46 2614 25 –2.0 82 662851 12747.13 12.1365 0.259 0.5015 0.010 0.95 2620 95 2615 56 2616 20 –0.2 83 416360 Infinite 12.9122 0.260 0.5159 0.010 0.96 2682 97 2673 54 2657 17 –0.9Published by NRC Research Press 84 252375 Infinite 13.1744 0.276 0.5171 0.011 0.96 2687 98 2692 56 2676 17 –0.4 85 208645 Infinite 11.6138 0.424 0.4548 0.016 0.97 2416 114 2574 94 2678 18 9.8 86 1148347 Infinite 7.6352 0.513 0.3010 0.020 0.99 1696 124 2189 147 2685 20 36.8 87 1089764 6263.011 13.2524 0.216 0.5143 0.008 0.96 2675 91 2698 44 2720 17 1.7 88 808986 3595.492 13.2011 0.297 0.5020 0.011 0.96 2622 98 2694 61 2743 18 4.4 89 2297798 10687.43 14.0788 0.229 0.5194 0.008 0.95 2697 92 2755 45 2806 17 3.9 90 2196173 Infinite 11.3921 0.208 0.4155 0.008 0.96 2240 78 2556 47 2827 17 20.7 91 2605994 Infinite 14.3094 0.171 0.5033 0.006 0.94 2628 84 2770 33 2886 18 8.9 525
  12. 12. 526 Table 1 (continued). Isotopic ratios Apparent ages (Ma) 206Pb 206 Pb 207 Pb 206 Pb Err. 206 Pbà ± 207 Pbà 207 Pbà Disc. Grain # (cps) 204 Pb 235 U ± (2s) 238 U ± (2s) corr. 238 U (2s) 235 U ± (2s) 206 Pbà ± (2s) (%) Sample 06YHL046B (UTM Zone 9N, N7272396, E343816) 1 306103 21864.5 0.4471 0.011 0.0586 0.001 0.90 367 13 375 9 412 38 10.8 2 143296 Infinite 0.5353 0.013 0.0686 0.002 0.96 428 16 435 11 439 25 2.6 3 267931 Infinite 0.5415 0.008 0.0698 0.001 0.95 435 15 439 7 449 24 3.1 4 269063 Infinite 0.5246 0.009 0.0667 0.001 0.95 416 14 428 7 450 23 7.5 5 305544 25462.04 0.5388 0.011 0.0690 0.001 0.91 430 15 438 9 452 33 4.8 6 191005 Infinite 0.5527 0.010 0.0706 0.001 0.95 440 15 447 8 452 24 2.8 7 117843 Infinite 0.5512 0.010 0.0696 0.001 0.94 434 15 446 8 453 27 4.3 8 87963 Infinite 0.5519 0.008 0.0697 0.001 0.94 435 14 446 6 457 24 4.9 9 273721 Infinite 0.5580 0.010 0.0712 0.001 0.94 444 15 450 8 461 27 3.8 10 244012 Infinite 0.5268 0.010 0.0673 0.001 0.96 420 15 430 8 464 23 9.4 11 157050 6828.25 0.5478 0.008 0.0693 0.001 0.94 432 14 444 7 476 25 9.3 12 250449 Infinite 0.5569 0.012 0.0701 0.001 0.96 437 16 450 9 488 23 10.5 13 90322 Infinite 0.5830 0.009 0.0726 0.001 0.94 452 15 466 8 488 26 7.4 14 75488 Infinite 0.5878 0.009 0.0735 0.001 0.93 457 15 469 7 489 27 6.5 15 258727 Infinite 0.5517 0.014 0.0694 0.002 0.94 433 17 446 11 489 29 11.6 16 540430 24565 0.4523 0.009 0.0569 0.001 0.91 357 12 379 8 505 33 29.3 17 667919 Infinite 0.5657 0.017 0.0701 0.002 0.97 437 19 455 14 514 23 15.0 18 61977 Infinite 0.5407 0.008 0.0656 0.001 0.91 410 13 439 6 553 30 25.9 19 667782 897.556 1.2921 0.107 0.1382 0.011 0.97 835 72 842 70 946 40 11.7 20 554178 Infinite 1.5739 0.027 0.1571 0.003 0.96 940 32 960 16 987 21 4.7 21 1153240 31168.66 1.7696 0.026 0.1748 0.002 0.93 1038 34 1034 15 1045 24 0.7 22 53008 Infinite 1.9203 0.040 0.1822 0.004 0.95 1079 39 1088 23 1067 24 –1.2 23 827576 Infinite 1.9780 0.036 0.1875 0.003 0.96 1108 39 1108 20 1106 20 –0.2 24 48901 Infinite 2.1117 0.041 0.1952 0.004 0.94 1149 40 1153 23 1106 25 –3.9 25 276073 21236.4 1.8961 0.045 0.1767 0.004 0.93 1049 39 1080 26 1121 28 6.4 26 493272 Infinite 2.0163 0.038 0.1879 0.003 0.96 1110 39 1121 21 1138 21 2.4 27 385501 Infinite 2.1941 0.027 0.2006 0.002 0.95 1179 38 1179 15 1168 20 –0.9 28 391950 23055.89 2.1692 0.031 0.1970 0.002 0.92 1159 37 1171 17 1178 26 1.6 29 862341 16908.65 2.1118 0.040 0.1932 0.003 0.90 1139 38 1153 22 1181 30 3.6 Can. J. Earth Sci. Vol. 48, 2011 30 329913 Infinite 2.2349 0.035 0.2006 0.003 0.95 1179 40 1192 19 1198 21 1.6Published by NRC Research Press 31 1542492 23022.28 2.2253 0.039 0.2020 0.003 0.93 1186 40 1189 21 1215 26 2.4 32 963785 19669.07 2.3924 0.042 0.2128 0.003 0.92 1244 41 1240 22 1243 27 –0.1 33 183429 Infinite 2.5816 0.025 0.2189 0.002 0.93 1276 40 1295 13 1302 22 2.0 34 805537 44752.06 2.6900 0.056 0.2234 0.005 0.96 1300 47 1326 28 1366 21 4.9 35 387711 Infinite 2.9232 0.053 0.2292 0.004 0.95 1330 46 1388 25 1468 20 9.4 36 184140 Infinite 3.3213 0.085 0.2559 0.006 0.93 1469 56 1486 38 1494 27 1.7 37 582297 Infinite 3.4728 0.046 0.2661 0.003 0.95 1521 50 1521 20 1512 20 –0.6 38 283821 Infinite 3.1801 0.065 0.2393 0.005 0.95 1383 50 1452 30 1525 21 9.3 39 98480 Infinite 3.8013 0.085 0.2746 0.006 0.95 1564 58 1593 35 1597 22 2.0
  13. 13. Lemieux et al. Table 1 (continued). Isotopic ratios Apparent ages (Ma) 206Pb 206 Pb 207 Pb 206 Pb Err. 206 Pbà ± 207 Pbà 207 Pbà Disc. Grain # (cps) 204 Pb 235 U ± (2s) 238 U ± (2s) corr. 238 U (2s) 235 U ± (2s) 206 Pbà ± (2s) (%) 40 534604 Infinite 4.1880 0.070 0.2967 0.005 0.96 1675 57 1672 28 1650 19 –1.5 41 774143 3351.27 4.0421 0.059 0.2841 0.004 0.95 1612 54 1643 24 1679 19 4.0 42 271748 Infinite 4.2425 0.065 0.2948 0.004 0.95 1665 56 1682 26 1683 19 1.1 43 1049121 2149.839 4.4244 0.111 0.3093 0.008 0.96 1737 68 1717 43 1731 20 –0.4 44 1083148 16924.2 5.2375 0.104 0.3449 0.006 0.93 1910 67 1859 37 1807 24 -5.7 45 345860 Infinite 5.1241 0.078 0.3283 0.005 0.95 1830 61 1840 28 1837 19 0.4 46 87174 Infinite 5.0542 0.081 0.3175 0.005 0.94 1777 60 1828 29 1844 21 3.6 47 908076 Infinite 4.8886 0.093 0.3145 0.006 0.96 1763 62 1800 34 1848 19 4.6 48 160593 Infinite 5.1285 0.074 0.3232 0.005 0.95 1806 60 1841 27 1850 19 2.4 49 158205 Infinite 5.2452 0.144 0.3314 0.009 0.96 1845 74 1860 51 1855 21 0.5 50 217662 Infinite 5.1917 0.104 0.3269 0.006 0.96 1823 65 1851 37 1855 19 1.7 51 286154 Infinite 5.1969 0.118 0.3299 0.007 0.96 1838 69 1852 42 1858 19 1.1 52 908503 Infinite 5.1060 0.101 0.3245 0.006 0.96 1812 65 1837 36 1881 18 3.7 53 380632 Infinite 5.2275 0.092 0.3266 0.006 0.96 1822 63 1857 33 1882 18 3.2 54 547020 30390.02 5.4287 0.102 0.3397 0.006 0.95 1885 66 1889 36 1884 20 0.0 55 418269 Infinite 5.1815 0.097 0.3247 0.006 0.96 1813 64 1850 35 1886 19 3.9 56 547155 Infinite 5.3779 0.100 0.3358 0.006 0.96 1867 66 1881 35 1887 18 1.1 57 383706 Infinite 5.2456 0.106 0.3247 0.006 0.93 1813 64 1860 37 1899 24 4.5 58 823007 39190.81 5.5397 0.101 0.3455 0.006 0.95 1913 67 1907 35 1905 19 –0.4 59 227125 Infinite 5.7988 0.144 0.3527 0.009 0.97 1948 76 1946 48 1927 18 –1.1 60 415084 29648.85 5.5268 0.086 0.3346 0.005 0.95 1860 62 1905 30 1937 20 3.9 61 863196 Infinite 5.4964 0.070 0.3343 0.004 0.95 1859 61 1900 24 1943 18 4.3 62 568320 33430.6 5.6318 0.112 0.3386 0.006 0.95 1880 67 1921 38 1945 21 3.3 63 301989 Infinite 5.9578 0.228 0.3544 0.013 0.94 1956 91 1970 75 1981 30 1.3 64 1654832 7576.821 5.9299 0.170 0.3536 0.010 0.97 1952 81 1966 56 1989 18 1.9 65 134120 Infinite 6.3813 0.096 0.3660 0.005 0.95 2011 67 2030 30 2014 20 0.2 66 453298 11928.89 6.4458 0.162 0.3719 0.009 0.93 2038 77 2039 51 2028 26 –0.5 67 213612 Infinite 6.2961 0.073 0.3578 0.004 0.95 1972 63 2018 23 2042 18 3.4 68 340590 Infinite 6.9231 0.087 0.3816 0.005 0.95 2084 68 2102 27 2103 18 0.9 69 169094 Infinite 7.2633 0.110 0.3982 0.006 0.95 2161 72 2144 32 2108 18 –2.5 70 254999 1432.578 7.0782 0.224 0.3826 0.011 0.92 2088 86 2121 67 2132 31 2.1 71 288084 10288.7 7.7350 0.149 0.4007 0.006 0.91 2172 74 2201 42 2218 25 2.1Published by NRC Research Press 72 243308 Infinite 8.2218 0.117 0.4142 0.005 0.92 2234 72 2256 32 2259 22 1.1 73 713263 3114.684 7.9414 0.163 0.4009 0.007 0.91 2173 75 2224 46 2274 26 4.4 74 297895 Infinite 9.1338 0.172 0.4395 0.008 0.96 2349 83 2351 44 2334 18 –0.6 75 627237 36896.29 8.9794 0.166 0.4289 0.008 0.95 2301 81 2336 43 2369 18 2.9 76 588155 Infinite 9.5616 0.116 0.4463 0.005 0.95 2379 77 2393 29 2396 17 0.7 77 744871 Infinite 9.5427 0.175 0.4456 0.008 0.96 2376 83 2392 44 2404 17 1.2 78 688756 Infinite 10.3881 0.132 0.4568 0.006 0.95 2426 79 2470 31 2500 17 3.0 79 315734 Infinite 11.5054 0.202 0.4803 0.008 0.96 2529 88 2565 45 2578 17 1.9 527

×