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Detrital zircon geochronology and provenance of Late Proterozoic and mid-Paleozoic successions outboard of the miogeocline, southeastern Canadian Cordillera Y. Lemieux, R.I. Thompson, P. Erdmer, A. Simonetti, and R.A. Creaser
Abstract: The Kootenay Arc has been interpreted as the western limit of autochthonous continental margin strata, west of which occur Paleozoic to Mesozoic rocks of uncertain paleogeographic origin. Recent mapping has demonstrated stratigraphic linkage between the Kootenay Arc strata and rocks farther west. A U–Pb study of detrital zircons using laser ablation – multicollector – inductively coupled plasma – mass spectrometry (LA–MC–ICP–MS) was undertaken in the upper succession of the Monashee complex mantling gneiss and in mid-Paleozoic strata of the Chase Formation exposed in the northern Kootenay Arc area and adjacent outboard strata. The predominance of >1.75 Ga zircon matches well with basement domains of the western buried North American craton and indicates that most of the grains were derived from a source of North American affinity. Zircon between 1.00 and 1.30 Ga demonstrates a Neoproterozoic source of possible “Grenville” affinity. Additional populations in the Chase Formation are mid-Paleozoic, Ediacaran, 800–1000 Ma, and 1400–1750 Ma. We interpret them to have been derived from exposed sources of Proterozoic continental crust and (or) proximal late Neoproterozoic and middle Paleozoic magmatic sources. The investigated Proterozoic and Paleozoic successions confirm sedimentologic and depositional relationships with the ancestral North American margin, and as such are interpreted to represent outboard extensions of the Cordilleran miogeoclinal succession. Résumé : L’arc de Kootenay a été interprété comme étant la limite occidentale des strates autochtones à la bordure du continent, à l’ouest duquel se retrouvent des roches paléozoïques à mésozoïques dont l’origine paléogéographique est incertaine. Une cartographie récente a démontré un lien stratigraphique entre les strates de l’arc de Kootenay et les roches plus à l’ouest. Une étude U–Pb sur des zircons détritiques par ablation au laser, de concert avec un instrument ICP–MS (plasma inductif – spectrométrie de masse) multicollecteur (LA–MC–ICP–MS) a été entreprise dans le haut de la succession du gneiss de recouvrement du complexe de Monashee, dans les strates de la Formation de Chase (Paléozoïque moyen), laquelle affleure dans le nord du secteur de l’arc Kootenay, et dans les strates extérieures adjacentes. La prédominance de zircon > 1,75 Ga concorde bien avec les domaines du socle du craton occidental enfoui de l’Amérique du Nord et indique que la plupart des grains proviennent d’une source d’affinité nord-américaine. Les zircons âgés de 1,0 à 1,3 Ga montrent une source néoprotérozoïque d’affinité possiblement « grenvillienne ». Des populations additionnelles dans la Formation de Chase datent du Paléozoïque moyen, de l’Édiacarien, 800–1000 Ma et 1400–1750 Ma. Nous interprétons ces populations comme provenant de sources exposées de croûte continentale protérozoïque et(ou) de sources magmatiques proximales du Néoprotérozoïque tardif ou du Paléozoïque moyen. Les successions protérozoïques et paléozoïques analysées confirment les relations de sédimentologie et de déposition avec la bordure nord-américaine ancestrale et, comme telles, elles représenteraient des extensions externes de la succession miogéoclinale de la Cordillère. [Traduit par la Rédaction]
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Introduction A number of detrital zircon U–Pb dates from the southeastern Canadian Cordillera strata have been reported (e.g., Gehrels et al. 1995; Gehrels and Ross 1998; Ross and
Villeneuve 2003). Only two studies, however, have focused on the detrital record in the northern Kootenay Arc region of southeastern British Columbia. Smith and Gehrels (1991) and Roback et al. (1994) suggested that the Laurentian continental margin contributed zircons to strata of the lower
Received 8 March 2007. Accepted 16 August 2007. Published on the NRC Research Press Web site at cjes.nrc.ca on 30 November 2007. Paper handled by Associate Editor B. Davis. Y. Lemieux,1,2 P. Erdmer, A. Simonetti, and R.A. Creaser. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada. R.I. Thompson. Pacific Division, Geological Survey of Canada, 9860 West Saanich Road, Sidney, BC V8L 4B2, Canada. 1 2
Corresponding author (e-mail:
[email protected]). Present address: Northwest Territories Geoscience Office, Geological Survey of Canada, 4601B 52 Avenue, Yellowknife, NT X1A 2R3, Canada.
Can. J. Earth Sci. 44: 1675–1693 (2007)
doi:10.1139/E07-048
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Paleozoic Lardeau Group and Mississippian Milford Group, respectively. Hence, the western limit of rocks with a conspicuous North American fingerprint could be extended west of the Kootenay Arc, into the Upper Arrow Lake area. Regional stratigraphic correlation from the Kootenay Arc west across the Columbia River and Upper Arrow Lake has been hampered by poor chronostratigraphic control and lack of systematic bedrock mapping. Correlations sought to equate Proterozoic and lower Paleozoic successions such as the Belt–Purcell, Horsethief Creek, Hamill, and Lardeau groups east of Upper Arrow Lake with lithologically similar rock units belonging to the Chase, Silver Creek, Tsalkom, Sicamous, and Eagle Bay formations west of the lake (Read and Wheeler 1976; Read 1979; Carr 1991; Thompson and Daughtry 1997). It is now established that most, and perhaps all, of the latter formations are Devonian and younger (Lemieux 2006; Thompson et al. 2006; this study). This paper presents new detrital zircon dates using laser ablation – multicollector – inductively coupled plasma – mass spectrometry (LA–MC–ICP–MS) from Proterozoic and midPaleozoic strata of the Upper Arrow Lake and northern Kootenay Arc areas. The purpose of the study was to test the hypothesis that deposition of strata having North American affinity extends west of previous interpretations, and possibly west of the Okanagan Valley (during the Devonian; Thompson et al. 2006). The results are discussed with respect to four criteria: (i) possible source regions, (ii) similarity with published dates for the Cordilleran miogeocline, (iii) the western limit of rocks having a North American affinity, and (iv) constraints on depositional age of the units. We conclude that strata (Proterozoic and mid-Paleozoic) having continental margin affinity extend far west of the Kootenay Arc.
Regional geology and tectonic setting The Kootenay Arc is a convex-east curvilinear belt comprising complexly deformed and regionally metamorphosed strata, extending from Revelstoke, British Columbia, south to Kootenay Lake and into the State of Washington (Hedley 1955) (Fig. 1). It is composed of greenschist- to loweramphibolite-facies, off-shelf, miogeoclinal strata of Neoproterozoic and lower Paleozoic age overlain by siliciclastic and volcanogenic strata of mid-Paleozoic through Late Triassic age. The area underwent widespread mid-Jurassic deformation and regional metamorphism (e.g., Archibald et al. 1983). Autochthonous strata in the Kootenay Arc include the upper Proterozoic Horsethief Creek Group (part of the Windermere Supergroup), the Lower Cambrian Hamill Group, and the Lower Cambrian Badshot Formation. The Horsethief Creek Group consists of metapelite, amphibolite, carbonate rocks, and meta-sandstone, derived from cratonic basement rocks to the east (Ross et al. 1989; Gehrels and Ross 1998) or alternatively from a continental source to the west (Thompson et al. 2006). It accumulated during a period of episodic rifting that culminated in continental fragmentation ca. 570 Ma, followed by the onset of passive margin subsidence by ca. 550 Ma (Bond and Kominz 1984; Erdmer et al. 2001; Colpron et al. 2002). The Hamill Group is a transgressive quartzite–pelite margin infill that eventually onlapped cratonic basement to the east. It is overlain by Lower Cambrian Badshot Formation
Can. J. Earth Sci. Vol. 44, 2007
limestone (Fyles and Eastwood 1962). Subsidence of the margin continued through the lower Paleozoic with deposition of carbonaceous siliciclastic and volcanic rocks belonging to the Lardeau Group, which locally are restricted to the east of Upper Arrow Lake (Fig. 2). The Mississippian Milford Group unconformably overlies the Lardeau Group (Read 1973, 1975; Lemieux et al. 2004). South of the study area, in the Goat Ranges, Klepacki and Wheeler (1985) subdivided the Milford Group into three temporally equivalent assemblages, each occupying elongate fault-bounded panels: from east to west, they are the Davis, Keen Creek, and McHardy assemblages. Only the McHardy assemblage is exposed in the present study area. Smith and Gehrels (1991) reported single-grain and multigrain zircon U–Pb dates from strata of the Horsethief Creek, Hamill, and Lardeau groups exposed in the vicinity of Trout Lake (see Fig. 3 for summary of results). Except for one single-grain analysis yielding a date of 703 Ma, the grains were between 1.76 and 2.69 Ga and interpreted to have been derived from miogeoclinal strata or adjacent portions of the craton presently beneath southern Alberta. Roback et al. (1994) analyzed individual detrital zircons from the McHardy assemblage in the Tenderfoot Lake area. The zircons yielded dates between 1.79 and 3.07 Ga (Fig. 3) and were interpreted to have been derived from reworked miogeoclinal strata and deposited along the western North American continental margin. Roback et al. also analyzed two boulders recovered from one of several conglomerates at the base of the McHardy assemblage (Cooper Conglomerate) and obtained two upper intercepts of 418 and 431 Ma (Fig. 3). The succession in the Upper Arrow Lake area was described by Lemieux et al. (2003) and Lemieux (2006) and is summarized here. The regional setting is on the east flank of the Shuswap metamorphic complex (SMC) and includes Paleoproterozoic to Mesozoic, amphibolite-facies metamorphic rocks of uncertain paleogeographic origin (Figs. 1, 2). The oldest and structurally lowest rock unit (unit 1) is primarily composed of paragneiss and schist of probable Neoproterozoic or early Paleozoic age. It is correlated with the upper part of the Monashee complex cover sequence of Reesor and Moore (1971, their map unit M9). Overlying unit 1, the mid-Devonian Chase Formation is composed of diopside-bearing calcareous quartzite with minor marble and calc-silicate gneiss. It is conformably overlain by the Silver Creek Formation, which includes schist with minor calcsilicate, marble, and quartzite. The Chase and Silver Creek formations have regional extent, from Tenderfoot Lake on the northeast margin of the Kuskanax batholith (i.e., western margin of Lardeau trough; see Thompson et al. 2006), across Upper Arrow Lake, and from there westward, beyond the Okanagan Valley, to the town of Chase, a distance of more than 150 km (see Fig. 1 for location). Rocks in the Upper Arrow Lake area experienced a complex history of burial, deformation, and metamorphism until the latest Cretaceous (e.g., see reviews by Parrish et al. 1988; Parrish 1995). Present tectonic models generally propose that deformation coincided temporally with crustal thickening and tectonic overlap of rocks of uncertain paleogeographic origin onto the cratonic margin along crustal-scale thrust faults (e.g., Brown et al. 1992; Price 1994; Brown 2004, and references therein). Alternatively, Thompson et al. (2006) suggested that Paleozoic and lower Mesozoic strata exposed here were © 2007 NRC Canada
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Fig. 1. Schematic tectonic assemblage map of southeastern British Columbia showing the study area (modified from Wheeler and McFeely 1991). Faults: BF, Beavan fault; CF, Cherry fault; CRFZ, Columbia River fault zone; ERF, Eagle River fault; OVF, Okanagan Valley fault. Basement culminations: FC, Frenchman Cap: TO, Thor–Odin. The inset shows the location of the study area and extent of the Cordilleran miogeocline.
stratigraphically, rather than tectonically, emplaced in a continental marginal basin limited to the west by emergent North American crust. Although Mesozoic deformation and transposition masked primary structures within the succession (e.g., Lemieux et al. 2004; Lemieux 2006; Glombick et al. 2006), new evidence, such as the continuity of the Chase – Sliver Creek sequence without structural repetition or deletion across the area, supports a stratigraphic contact with the un-
derlying Paleoproterozoic metasedimentary succession (see reviews by Lemieux 2006; Thompson et al. 2006). Exhumation of the SMC has been attributed to regional extension in the early Tertiary (e.g., Parrish et al. 1988). The Columbia River fault zone (CRFZ; Figs. 1, 2) is one of several faults mapped in southern British Columbia interpreted to account for much of the extension, with previously proposed displacement in excess of 20 km (Read © 2007 NRC Canada
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Fig. 2. Geological map of the Upper Arrow Lake area (from Hyndman 1968; Carr 1991; Lemieux 2006). The map shows the location of samples used for the U–Pb detrital zircons (Zr) and (or) Nd isotopic study (Nd). CRFZ, Columbia River fault zone; RCF, Rodd Creek fault.
and Brown 1981; Parrish et al. 1988; Carr 1991). Recent mapping along the flanks of the SMC, however, showed that rocks of the same age and metamorphic grade occur in both hanging wall and footwall, i.e., contradicting the low-angle detachment fault model (Glombick et al. 2006; Lemieux 2006). The study area thus appears to be characterized by a coherent stratigraphic and metamorphic succession.
U–Pb geochronology Analytical procedures U–Pb zircon analysis was performed for six samples from two different stratigraphic units ranging in age from Proterozoic to Devonian (Fig. 3); their geographic location is shown in Fig. 2 and given in Table 1. Sample 02TWL225P (unit 1), coarse-grained quartz–feldspar–biotite schist, was collected © 2007 NRC Canada
Lemieux et al.
Fig. 3. Schematic stratigraphic columns of Upper Arrow Lake and northern Kootenay Arc areas. The figure shows the units sampled for detrital zircons. Results of selected detrital studies in strata of the Kootenay Arc are included. The histograms include 207Pb/206Pb ages. The vertical scale on the histograms shows the number of occurrences (one square is one occurrence) for each 50 Ma interval. Data for the Milford Group are from Roback et al. (1994), and data for the Horsethief Creek, Hamill, and Lardeau groups from Smith and Gehrels (1991). Only single-grain analyses are shown. Stratigraphic columns of the Upper Arrow Lake area are from Lemieux (2006), and stratigraphic columns of northern Kootenay Arc area are modified after Fyles and Eastwood (1962), Read (1973), Klepacki and Wheeler (1985), and Colpron and Price (1995). The asterisks (*) denote units from Read (1973). See Lemieux (2006) for a discussion of regional correlations.
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Table 1. U–Pb data of detrital zircons. Isotopic ratios Grain No.
206
206
Pb cps
204
Pb Pb
a
207
Pb U
235
Apparent ages (Ma) 206
±1σ
Pb U
238
±1σ
Error corr.b
206
Pb* U
238
207
±1σ
Pb* U
235
207
±1σ
206
Pb* Pb*
±1σ
Disc. (%)c
Sample 02TWL225P (5556302N, 436021E) 1 139 547 362 3.8650 0.058 2 187 239 581 3.8895 0.058 3 52 969 266 3.9343 0.059 4 94 380 554 4.3124 0.065 5 297 047 1 100 3.8293 0.058 6 38 746 338 4.5025 0.068 7 207 307 1 111 4.1307 0.062 8 216 698 1 361 4.4117 0.066 9 485 356 3 485 2.9127 0.044 10 295 990 1 728 4.1934 0.063 11 380 647 2 126 4.1664 0.063 12 161 950 737 4.4573 0.067 13 295 772 1 579 3.3775 0.051 14 98 018 450 4.6340 0.070 15 462 871 2 443 4.0791 0.061 16 183 650 1 161 4.1297 0.062 17 436 128 3 748 3.8538 0.058 18 48 543 303 4.5496 0.068 19 156 909 1 342 4.3505 0.065 20 71 839 437 4.3632 0.066 21 225 427 1 585 4.4067 0.066 22 115 734 1 165 4.2158 0.063 23 347 227 2 740 4.0767 0.061 24 122 106 967 4.6644 0.070 25 100 335 806 4.5185 0.068 26 158 870 882 4.6708 0.070 27 138 446 945 4.6589 0.070 28 128 675 1 638 4.5066 0.068 29 107 348 1 065 4.6259 0.069 30 214 575 1 385 4.7893 0.072 31 228 689 1 065 4.2368 0.064 32 145 642 1 373 4.5060 0.068 33 348 267 2 967 4.2666 0.064 34 173 545 1 314 4.8680 0.073 35 188 907 Infinite 4.4372 0.067 36 81 089 981 4.9263 0.074 37 177 523 1 297 5.6537 0.085 38 164 942 1 198 5.4707 0.082 39 117 308 673 4.9064 0.074 40 88 098 Infinite 6.3792 0.096 41 550 853 Infinite 9.4875 0.142 42 435 545 2 513 6.9450 0.104 43 614 602 5 004 9.7889 0.147 44 264 645 1 154 9.6642 0.145 45 464 362 3 090 10.6750 0.160 46 325 525 3 108 10.3650 0.156 47 118 873 895 11.8930 0.178 48 165 181 1 078 12.4010 0.186 49 100 954 1 221 12.4330 0.187
0.2888 0.2843 0.2873 0.3095 0.2710 0.3174 0.2806 0.2995 0.1971 0.2831 0.2812 0.3004 0.2277 0.3124 0.2725 0.2758 0.2572 0.3024 0.2883 0.2888 0.2911 0.2784 0.2672 0.3051 0.2951 0.3007 0.2995 0.2891 0.2968 0.3049 0.2694 0.2864 0.2709 0.3074 0.2792 0.3001 0.3365 0.3234 0.2833 0.3360 0.4243 0.3029 0.4154 0.4094 0.4423 0.4272 0.4680 0.4775 0.4682
0.005 0.005 0.005 0.005 0.004 0.005 0.005 0.005 0.003 0.006 0.005 0.005 0.004 0.005 0.004 0.004 0.004 0.005 0.005 0.005 0.005 0.004 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.004 0.005 0.004 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.007 0.005 0.007 0.007 0.007 0.007 0.008 0.008 0.008
0.76 0.92 0.52 0.84 0.94 0.74 0.93 0.94 0.94 0.99 0.94 0.57 0.94 0.87 0.95 0.93 0.95 0.95 0.93 0.85 0.93 0.92 0.95 0.89 0.93 0.93 0.84 0.89 0.91 0.93 0.95 0.95 0.94 0.92 0.94 0.89 0.92 0.93 0.94 0.93 0.95 0.94 0.95 0.95 0.95 0.95 0.95 0.94 0.95
1636 1613 1628 1738 1546 1777 1594 1689 1160 1607 1597 1693 1323 1753 1554 1570 1475 1703 1633 1636 1647 1583 1527 1717 1667 1695 1689 1637 1675 1716 1538 1623 1545 1728 1587 1692 1870 1806 1608 1868 2280 1706 2240 2212 2361 2293 2475 2516 2476
25 26 27 27 24 29 26 28 18 34 26 26 22 27 25 25 25 27 26 26 26 25 27 27 27 27 26 27 26 27 25 29 24 27 27 27 29 28 28 29 37 26 36 37 37 38 39 40 41
1606 1612 1621 1696 1599 1731 1660 1715 1385 1673 1667 1723 1499 1755 1650 1660 1604 1740 1703 1705 1714 1677 1650 1761 1734 1762 1760 1732 1754 1783 1681 1732 1687 1797 1719 1807 1924 1896 1803 2029 2386 2104 2415 2403 2495 2468 2596 2635 2638
24 24 24 25 24 26 25 26 21 25 25 26 23 26 25 25 24 26 26 26 26 25 25 26 26 26 26 26 26 27 25 26 25 27 26 27 29 28 27 30 36 32 36 36 37 37 39 40 40
1568 1610 1611 1644 1670 1676 1745 1746 1752 1757 1757 1759 1759 1759 1775 1776 1778 1785 1790 1792 1796 1797 1810 1814 1817 1842 1845 1849 1849 1863 1865 1866 1868 1878 1884 1942 1984 1996 2037 2198 2478 2521 2566 2570 2606 2615 2692 2728 2764
12 18 23 16 16 22 19 23 16 49 18 10 24 15 21 19 27 20 17 20 19 17 31 15 18 18 13 20 16 17 22 32 9 12 27 17 16 14 28 13 21 10 18 24 14 22 17 15 22
–4.9 –0.2 –1.2 –6.5 8.4 –6.9 9.7 3.7 36.9 9.7 10.3 4.2 27.4 0.4 14.0 13.1 19.0 5.2 9.9 9.9 9.4 13.4 17.6 6.1 9.4 9.1 9.6 13.0 10.7 9.0 19.7 14.7 19.4 9.1 17.8 14.6 6.6 10.9 23.8 17.3 9.5 36.7 15.0 16.4 11.2 14.6 9.7 9.4 12.5
Sample 02TWL307 (5556107N, 1 29 186 783 2 156 076 Infinite 3 117 188 Infinite
0.1626 0.1977 0.1745
0.003 0.003 0.003
0.74 0.92 0.93
971 1163 1037
15 18 16
980 1126 1060
15 17 16
1000 1054 1109
13 12 15
3.1 –11.3 7.0
419098E) 1.6254 0.024 2.0301 0.031 1.8417 0.028
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Table 1. (continued). Isotopic ratios 206
a
207
Apparent ages (Ma) 206
Pb U
±1σ
3.4891 3.8344 3.6640 3.6789 3.7235 4.1454 4.1660 3.7753 4.0089 4.4470 4.4272 4.4219 4.5933 4.2196 4.6652 4.2068 4.8401 4.6746 2.4543 4.9018 3.7473 5.0295 5.2059 4.8838 5.0403 5.4178 5.2339 5.2059 4.7524 4.4104 3.6042 6.2043 5.9917 8.7007 7.1505 9.7597 10.3420 9.7460 10.7010 12.0080 10.6370 12.5190 12.5500
0.052 0.058 0.055 0.055 0.056 0.062 0.063 0.057 0.060 0.067 0.066 0.066 0.069 0.063 0.070 0.063 0.073 0.070 0.037 0.074 0.056 0.076 0.078 0.073 0.076 0.081 0.079 0.078 0.071 0.066 0.054 0.093 0.090 0.131 0.107 0.146 0.155 0.146 0.161 0.180 0.160 0.188 0.188
Sample 02TWL225 (5556302N, 436021E) 1 114 765 1 099 0.8874 0.013 2 133 431 1 069 1.4405 0.022 3 344 404 1 941 1.4058 0.021 4 152 379 1 360 1.4598 0.022 5 75 350 833 1.6455 0.025 6 239 480 1 622 1.5785 0.024 7 166 165 1 570 1.8158 0.027 8 145 493 821 1.7639 0.027 9 298 343 3 674 1.9535 0.029 10 59 256 413 1.8505 0.028
Grain No. 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
206
Pb cps
76 242 91 859 204 207 191 961 204 907 54 203 176 957 241 772 351 085 56 417 167 246 96 074 93 325 184 722 38 123 95 323 91 286 89 361 235 347 148 730 73 334 81 249 145 702 92 400 310 010 287 041 204 159 99 477 171 349 229 877 175 792 83 971 118 039 107 348 452 952 128 824 153 312 77 508 170 784 148 272 319 817 126 124 218 877
204
Pb Pb
Infinite Infinite Infinite 2 778 Infinite 1 032 Infinite Infinite 2 644 338 Infinite 1 968 1 847 536 648 439 2 884 Infinite 3 071 3 488 1 154 93 Infinite Infinite Infinite Infinite Infinite 180 1 773 240 1 788 Infinite Infinite Infinite 10 276 2 257 Infinite 1 237 262 2 079 1 787 2 950 Infinite
235
Pb U
206
Pb* U
207
Pb* U
207
±1σ
Error corr.b
0.2822 0.2965 0.2626 0.2589 0.2618 0.2868 0.2844 0.2564 0.2716 0.2997 0.2932 0.2919 0.3020 0.2761 0.3030 0.2715 0.3104 0.2990 0.1555 0.3075 0.2349 0.3129 0.3195 0.2989 0.3039 0.3258 0.3136 0.3110 0.2798 0.2583 0.2108 0.3425 0.3305 0.4141 0.3184 0.4286 0.4470 0.4112 0.4434 0.4734 0.4164 0.4785 0.4757
0.004 0.005 0.004 0.004 0.005 0.005 0.005 0.004 0.005 0.005 0.005 0.005 0.005 0.004 0.005 0.005 0.005 0.005 0.003 0.005 0.004 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.004 0.005 0.004 0.005 0.005 0.006 0.005 0.007 0.007 0.007 0.007 0.007 0.007 0.008 0.007
0.88 0.92 0.93 0.94 0.99 0.93 0.94 0.94 0.95 0.93 0.93 0.93 0.93 0.94 0.92 0.71 0.93 0.92 0.96 0.93 0.94 0.93 0.94 0.94 0.94 0.93 0.94 0.94 0.94 0.95 0.97 0.93 0.94 0.93 0.95 0.94 0.93 0.95 0.94 0.94 0.94 0.94 0.94
1603 1674 1503 1484 1499 1625 1614 1471 1549 1690 1657 1651 1701 1572 1706 1549 1743 1687 932 1729 1360 1755 1787 1686 1711 1818 1758 1746 1591 1481 1233 1899 1841 2234 1782 2299 2382 2220 2366 2499 2244 2521 2509
25 27 23 23 30 26 26 24 26 26 26 26 26 24 28 27 27 26 16 27 22 28 28 28 26 28 28 28 24 26 24 30 29 35 28 37 37 38 37 39 35 39 39
1525 1600 1564 1567 1576 1663 1667 1588 1636 1721 1717 1716 1748 1678 1761 1675 1792 1763 1259 1803 1582 1824 1854 1799 1826 1888 1858 1854 1777 1714 1550 2005 1975 2307 2130 2412 2466 2411 2498 2605 2492 2644 2646
23 24 23 24 24 25 25 24 25 26 26 26 26 25 26 25 27 26 19 27 24 27 28 27 27 28 28 28 27 26 23 30 30 35 32 36 37 36 37 39 37 40 40
0.0988 0.1573 0.1531 0.1548 0.1732 0.1650 0.1785 0.1709 0.1831 0.1715
0.002 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003 0.003
0.92 0.95 0.95 0.92 0.94 0.94 0.95 0.91 0.95 0.86
608 942 918 928 1030 985 1059 1017 1084 1020
11 17 16 15 18 17 19 16 19 19
645 906 891 914 988 962 1051 1032 1100 1064
10 14 13 14 15 14 16 16 17 16
238
238
±1σ
235
±1σ
Pb* Pb*
±1σ
Disc. (%)c
1418 1504 1646 1680 1681 1712 1736 1746 1750 1760 1792 1797 1804 1813 1826 1838 1850 1854 1872 1889 1891 1904 1929 1934 1960 1965 1972 1977 2003 2012 2015 2116 2118 2373 2486 2509 2536 2576 2606 2689 2701 2740 2754
14 20 6 8 45 19 17 19 25 13 12 14 12 13 20 17 13 9 28 11 22 18 15 24 11 14 16 16 9 32 39 15 13 12 15 17 12 26 14 12 15 14 12
–14.7 –12.8 9.7 13.0 12.1 5.7 8.0 17.6 12.9 4.5 8.5 9.2 6.5 15.0 7.5 17.7 6.6 10.3 53.9 9.7 31.1 8.9 8.4 14.6 14.5 8.6 12.4 13.3 23.2 29.5 42.6 11.8 15.0 6.9 32.3 9.9 7.3 16.3 11.0 8.5 20.0 9.7 10.7
778 820 825 880 896 910 1035 1064 1130 1153
33 37 33 22 33 30 33 14 31 41
23.0 –16.0 –12.2 –5.8 –16.1 –8.8 –2.5 4.8 4.4 12.4
206
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Table 1. (continued). Isotopic ratios 206
a
207
Apparent ages (Ma) 206
Pb U
±1σ
1.9685 2.0522 2.2412 2.0028 2.6293 2.6523 2.8796 3.5437 3.5304 2.8828 4.0666 4.2706 3.5659 5.1120 3.6541 4.5893 5.7624 6.2559 8.0170 9.8918 9.7641 11.2000 11.4580 14.4490 18.2660
0.030 0.031 0.034 0.030 0.040 0.040 0.043 0.053 0.053 0.043 0.061 0.064 0.054 0.077 0.055 0.069 0.087 0.094 0.120 0.148 0.147 0.168 0.172 0.217 0.274
Sample 02TWL313 (5557777N, 418909E) 1 221 151 Infinite 0.5427 0.008 2 83 152 Infinite 0.5983 0.009 3 438 052 3 149 1.3902 0.021 4 133 187 Infinite 1.7759 0.027 5 240 721 2 120 2.0351 0.031 6 125 599 585 1.8228 0.027 7 304 421 1 982 2.2298 0.034 8 100 766 Infinite 1.5406 0.023 9 98 856 Infinite 2.4581 0.037 10 87 948 Infinite 2.2816 0.034 11 140 252 Infinite 2.6254 0.040 12 153 318 Infinite 2.9867 0.045 13 207 012 1 424 3.1103 0.047 14 692 462 Infinite 3.4026 0.051 15 416 997 4 559 3.3496 0.050 16 194 096 Infinite 3.5173 0.053 17 261 642 Infinite 3.4568 0.052 18 198 486 Infinite 3.8810 0.058 19 266 978 Infinite 4.1207 0.062 20 751 679 Infinite 4.5948 0.069 21 269 940 Infinite 4.2397 0.064 22 189 166 Infinite 4.7010 0.071 23 170 138 Infinite 4.7914 0.072 24 220 175 Infinite 4.7805 0.072 25 54 448 Infinite 5.0757 0.076 26 506 889 3 153 4.9933 0.075 27 404 117 Infinite 5.9551 0.089 28 162 244 Infinite 11.239 0.169
Grain No.
206
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
92 148 181 497 213 725 65 025 189 198 175 385 272 679 122 715 78 003 101 568 73 346 144 581 314 733 71 905 1 125 166 384 990 580 042 1 131 490 123 751 320 177 72 959 104 047 50 351 382 843 347 161
Pb cps
204
Pb Pb
580 1 609 2 185 Infinite 1 144 2 018 736 919 857 933 Infinite 473 3 184 611 8 682 3 594 4 462 7 947 95 Infinite 637 763 744 6 521 Infinite
235
Pb U
206
Pb* U
207
Pb* U
207
±1σ
Error corr.b
0.1825 0.1861 0.1944 0.1703 0.2226 0.2191 0.2356 0.2747 0.2716 0.2218 0.2828 0.2952 0.2450 0.3281 0.2344 0.2830 0.3464 0.3611 0.4473 0.4034 0.3954 0.4525 0.4615 0.5276 0.5766
0.003 0.003 0.004 0.003 0.004 0.004 0.004 0.005 0.004 0.004 0.005 0.005 0.004 0.006 0.004 0.004 0.006 0.006 0.007 0.007 0.007 0.008 0.008 0.009 0.009
0.89 0.94 0.94 0.89 0.91 0.94 0.92 0.95 0.92 0.90 0.93 0.96 0.95 0.94 0.94 0.91 0.96 0.96 0.96 0.96 0.96 0.96 0.94 0.94 0.95
1080 1100 1145 1014 1296 1277 1364 1565 1549 1291 1606 1667 1413 1829 1357 1607 1918 1987 2383 2185 2148 2406 2446 2731 2935
19 20 21 17 21 24 22 27 25 23 27 31 24 32 21 25 34 35 37 38 40 43 41 44 46
1105 1133 1194 1116 1309 1315 1377 1537 1534 1377 1648 1688 1542 1838 1561 1747 1941 2012 2233 2425 2413 2540 2561 2780 3004
17 17 18 17 20 20 21 23 23 21 25 25 23 28 23 26 29 30 34 36 36 38 38 42 45
0.0681 0.0666 0.1450 0.1727 0.1924 0.1672 0.2025 0.1372 0.2081 0.1887 0.2116 0.2336 0.2431 0.2591 0.2545 0.2530 0.2470 0.2713 0.2773 0.3066 0.2803 0.3041 0.3071 0.3048 0.3231 0.2839 0.3380 0.4707
0.001 0.001 0.002 0.003 0.004 0.003 0.004 0.002 0.004 0.003 0.004 0.004 0.004 0.004 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.006 0.006 0.005 0.006 0.009
0.93 0.92 0.93 0.92 0.96 0.93 0.98 0.94 0.85 0.94 0.98 0.93 0.94 0.94 0.98 0.96 0.97 0.98 0.95 0.94 0.95 0.91 0.95 0.96 0.95 0.91 0.95 0.85
424 415 873 1027 1135 997 1189 829 1219 1114 1237 1353 1403 1485 1462 1454 1423 1547 1578 1724 1593 1712 1727 1715 1805 1611 1877 2487
7 7 14 17 21 17 23 14 20 19 25 23 24 22 27 27 26 31 26 28 26 28 28 32 34 26 32 45
440 476 885 1037 1127 1054 1190 947 1260 1207 1308 1404 1435 1505 1493 1531 1517 1610 1658 1748 1682 1767 1783 1781 1832 1818 1969 2543
7 7 13 16 17 16 18 14 19 18 20 21 22 23 22 23 23 24 25 26 25 27 27 27 28 27 30 38
238
238
±1σ
235
±1σ
Pb* Pb*
±1σ
Disc. (%)c
1153 1196 1284 1322 1330 1378 1397 1499 1513 1513 1702 1713 1724 1848 1849 1920 1966 2038 2098 2633 2645 2648 2653 2815 3050
32 37 34 22 20 40 21 31 20 32 27 36 27 29 13 10 30 29 13 28 33 30 24 18 15
6.8 8.7 11.8 25.2 2.8 8.1 2.7 –4.9 –2.7 16.2 6.4 3.0 20.1 1.2 29.4 18.4 2.8 2.9 –16.3 20.0 22.1 10.9 9.4 3.6 4.7
523 780 915 1057 1113 1173 1193 1232 1331 1376 1426 1483 1484 1533 1537 1639 1652 1692 1762 1777 1794 1834 1851 1860 1863 2065 2068 2589
15 22 22 20 36 24 45 29 25 28 45 25 26 5 38 38 34 44 25 19 23 23 21 36 36 20 25 33
19.5 48.2 4.9 3.1 –2.1 16.2 0.4 34.9 9.3 20.7 14.5 9.7 6.1 3.5 5.5 12.6 15.5 9.6 11.8 3.4 12.6 7.6 7.7 8.9 3.6 24.8 10.6 4.8
206
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Table 1. (continued). Isotopic ratios Grain No. 29 30 31
206
206
Pb cps
86 472 341 054 494 485
204
Pb Pb
a
Infinite Infinite Infinite
207
Pb U
235
12.664 13.589 13.718
Apparent ages (Ma) 206
±1σ
Pb U
238
±1σ
Error corr.b
206
Pb* U
238
207
±1σ
Pb* U
235
207
±1σ
206
Pb* Pb*
±1σ
Disc. (%)c
0.190 0.204 0.206
0.4679 0.4957 0.4945
0.008 0.009 0.008
0.95 0.96 0.95
2475 2595 2590
42 45 44
2655 2721 2730
40 41 41
2795 2817 2836
24 26 23
13.8 9.6 10.5
Sample 04TWL025 (5602850N, 435683E) 1 134 876 904 0.4886 0.007 2 68 214 1 273 0.5026 0.008 3 199 321 1 793 0.5210 0.008 4 179 450 2 625 0.7439 0.011 5 110 180 455 0.6532 0.010 6 214 108 2 047 1.9851 0.030 7 96 374 1 090 1.8131 0.027 8 112 859 666 2.8820 0.043 9 183 502 Infinite 2.9728 0.045 10 192 759 1 605 3.0437 0.046 11 112 414 1 518 3.4637 0.052 12 697 186 5 114 2.9343 0.044 13 107 712 707 3.8426 0.058 14 224 729 1 520 3.7763 0.057 15 153 241 2 214 3.9848 0.060 16 201 659 2 864 3.9970 0.060 17 289 034 3 517 3.7584 0.056 18 1 668 365 4 218 4.5407 0.068 19 253 166 1 675 4.9841 0.075 20 644 810 2 569 5.5438 0.083 21 409 209 5 542 4.8527 0.073 22 422 747 2 114 5.0396 0.076 23 256 533 3 228 5.6987 0.086 24 154 043 666 6.0942 0.091 25 207 011 1 699 8.6568 0.130 26 94 882 1 217 11.4660 0.172 27 129 520 1 090 12.3890 0.186 28 187 889 1 322 12.6040 0.189
0.0644 0.0659 0.0655 0.0910 0.0744 0.1835 0.1501 0.2346 0.2301 0.2332 0.2620 0.2149 0.2758 0.2668 0.2773 0.2762 0.2589 0.2894 0.3049 0.3365 0.2934 0.2991 0.3323 0.3315 0.4103 0.4575 0.4744 0.4575
0.001 0.001 0.001 0.002 0.001 0.003 0.004 0.004 0.004 0.004 0.004 0.004 0.005 0.004 0.004 0.005 0.004 0.005 0.005 0.005 0.005 0.005 0.006 0.005 0.006 0.008 0.008 0.007
0.95 0.71 0.88 0.73 0.84 0.90 0.93 0.80 0.94 0.94 0.92 0.95 0.88 0.93 0.94 0.94 0.93 0.95 0.93 0.94 0.80 0.95 0.93 0.94 0.94 0.94 0.95 0.94
403 412 409 561 462 1086 902 1359 1335 1351 1500 1255 1570 1525 1578 1572 1484 1639 1716 1870 1658 1687 1850 1846 2216 2428 2503 2428
8 6 6 9 9 18 23 21 21 21 23 20 25 24 25 26 23 27 27 30 25 27 32 30 35 40 43 38
404 413 426 565 510 1110 1050 1377 1401 1419 1519 1391 1602 1588 1631 1634 1584 1738 1817 1907 1794 1826 1931 1989 2303 2562 2634 2650
6 6 6 9 8 17 16 21 21 21 23 21 24 24 24 25 24 26 27 29 27 27 29 30 35 38 40 40
412 443 516 579 732 1159 1374 1406 1502 1522 1546 1606 1644 1672 1701 1714 1719 1861 1934 1949 1956 1989 2020 2142 2380 2669 2737 2825
39 10 14 24 41 25 70 10 18 15 10 22 20 17 19 21 12 23 14 17 9 20 27 20 15 23 25 14
2.4 7.3 21.3 3.2 38.2 6.9 36.8 3.7 12.3 12.4 3.3 24.1 5.1 9.9 8.2 9.3 15.3 13.5 12.8 4.7 17.2 17.3 9.7 15.9 8.1 10.8 10.3 16.8
Sample 04TWL072 (5587206N, 1 43 037 Infinite 2 106 347 Infinite 3 116 147 1 205 4 151 560 2 151 5 163 966 Infinite 6 31 816 Infinite 7 155 855 Infinite 8 36 085 Infinite 9 190 344 3 001 10 83 135 Infinite 11 92 798 Infinite 12 66 386 Infinite 13 176 868 Infinite 14 118 286 1 459 15 69 697 1 614 16 72 805 Infinite 17 35 610 1 116 18 103 132 4 769 19 37 435 78 20 178 449 Infinite
0.1704 0.1925 0.2915 0.3008 0.2959 0.3028 0.2594 0.2988 0.2807 0.2939 0.2551 0.3266 0.3047 0.2615 0.2991 0.3183 0.3250 0.3110 0.3173 0.3259
0.003 0.003 0.005 0.005 0.005 0.005 0.004 0.005 0.005 0.005 0.004 0.005 0.005 0.004 0.005 0.005 0.005 0.005 0.005 0.005
0.85 0.94 0.94 0.94 0.95 0.84 0.94 0.88 0.96 0.94 0.94 0.92 0.94 0.95 0.92 0.94 0.92 0.94 0.92 0.94
1014 1135 1649 1695 1671 1705 1487 1685 1595 1661 1465 1822 1715 1498 1687 1781 1814 1746 1776 1818
16 19 27 28 28 28 24 28 28 28 24 29 28 25 28 29 28 29 28 29
1040 1153 1648 1690 1690 1724 1603 1720 1675 1717 1617 1830 1773 1648 1762 1817 1836 1806 1843 1870
16 17 25 25 25 26 24 26 25 26 24 27 27 25 26 27 28 27 28 28
1095 1189 1648 1683 1714 1747 1760 1763 1776 1786 1822 1838 1842 1845 1852 1859 1862 1876 1919 1928
21 26 23 22 23 21 21 21 30 24 19 16 19 25 24 22 14 23 17 20
8.0 5.0 –0.1 –0.8 2.8 2.7 17.4 5.0 11.5 8.0 21.9 1.0 7.9 21.1 10.1 4.8 3.0 7.9 8.5 6.5
474868E) 1.7857 0.027 2.1142 0.032 4.0706 0.061 4.2812 0.064 4.2840 0.064 4.4628 0.067 3.8496 0.058 4.4420 0.067 4.2037 0.063 4.4233 0.066 3.9167 0.059 5.0605 0.076 4.7303 0.071 4.0674 0.061 4.6701 0.070 4.9889 0.075 5.1018 0.077 4.9214 0.074 5.1416 0.077 5.3065 0.080
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Table 1. (concluded). Isotopic ratios Grain No. 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49
206
206
Pb cps
67 492 95 186 39 896 214 494 16 805 103 556 320 832 45 212 156 033 115 255 96 576 50 071 46 721 21 071 174 065 230 530 116 988 132 634 47 647 161 970 71 849 27 871 21 696 44 816 119 542 47 078 21 320 56 663 78 811
204
Pb Pb
a
Infinite Infinite Infinite 1 419 Infinite 422 121 Infinite 2 692 Infinite 1 104 Infinite 293 Infinite Infinite 2 217 4 896 2 628 Infinite Infinite 383 Infinite 541 185 885 Infinite Infinite 688 542
207
Apparent ages (Ma) 206
Pb U
±1σ
5.4277 5.1148 6.0491 6.8562 6.9234 8.9225 8.0148 8.4854 8.3391 9.5636 9.6713 8.4546 10.8830 10.2560 9.3184 9.2027 11.4730 8.5150 11.7700 12.0310 11.9790 11.8030 12.7520 12.7440 12.6320 13.3040 16.9940 24.4300 27.9380
0.082 0.077 0.091 0.103 0.104 0.134 0.120 0.127 0.125 0.144 0.145 0.127 0.163 0.154 0.140 0.138 0.172 0.128 0.177 0.181 0.180 0.177 0.191 0.191 0.190 0.200 0.255 0.367 0.419
235
Pb U
238
0.3235 0.3012 0.3476 0.3868 0.3673 0.4467 0.3954 0.4060 0.3956 0.4418 0.4348 0.3730 0.4759 0.4404 0.3909 0.3823 0.4688 0.3465 0.4712 0.4751 0.4721 0.4644 0.4999 0.4940 0.4892 0.4829 0.5426 0.6537 0.6630
±1σ
Error corr.b
0.005 0.005 0.006 0.006 0.006 0.007 0.007 0.007 0.006 0.007 0.007 0.007 0.008 0.007 0.006 0.006 0.008 0.005 0.008 0.008 0.007 0.009 0.008 0.008 0.008 0.008 0.009 0.010 0.012
0.94 0.93 0.93 0.94 0.88 0.94 0.96 0.95 0.93 0.95 0.94 0.95 0.67 0.89 0.91 0.95 0.95 0.94 0.94 0.95 0.94 0.97 0.89 0.90 0.82 0.95 0.92 0.94 0.95
206
Pb* U
238
1807 1697 1923 2108 2017 2380 2148 2197 2149 2359 2327 2044 2509 2352 2127 2087 2478 1918 2489 2506 2493 2459 2613 2588 2567 2540 2794 3243 3279
207
±1σ 30 29 31 34 33 39 37 38 34 39 38 36 40 37 33 34 41 29 40 41 39 46 42 42 40 40 47 51 57
Pb* U
235
1889 1839 1983 2093 2102 2330 2233 2284 2269 2394 2404 2281 2513 2458 2370 2358 2562 2288 2586 2607 2603 2589 2661 2661 2653 2701 2934 3286 3417
207
±1σ 28 28 30 31 32 35 34 34 34 36 36 34 38 37 36 35 38 34 39 39 39 39 40 40 40 41 44 49 51
206
Pb* Pb*
1981 2002 2046 2078 2186 2286 2311 2364 2379 2424 2470 2501 2516 2547 2586 2602 2630 2636 2664 2686 2689 2692 2698 2717 2718 2825 3032 3312 3499
±1σ 25 26 21 20 21 19 28 26 16 22 22 28 19 14 13 18 21 10 18 20 15 35 18 19 12 15 23 15 26
Disc. (%)c 10.1 17.3 6.9 –1.7 9.0 –4.9 8.3 8.3 11.4 3.2 6.9 21.3 0.3 9.1 20.8 23.1 6.9 31.4 7.9 8.1 8.8 10.4 3.8 5.8 6.7 12.2 9.6 2.7 8.0
Note: Universal transverse Mercator (UTM) coordinates (northing and easting) in North American datum of 1983 are given in parentheses after the sample number. Decay constants 235U = 9.8485 × 10–10, 238U = 1.55125 × 10–10. 238U/235U = 137.88. Preferred ages are based on 207Pb/206Pb for >1000 Ma grains and on 206Pb/238U for 1000 Ma grains and on 206Pb/238U for grains younger than 1000 Ma because they yield more pre© 2007 NRC Canada
Lemieux et al.
1685
Fig. 4. U–Pb age spectra of single detrital zircon grains from the Upper Arrow Lake and northern Kootenay Arc areas. Plot includes concordant and slightly discordant (2.00 Ga, with dominance at -2.70 Ga; and (iii) the occurrence of two mid-Paleozoic zircons.
Discussion Unit 1 The population of the two Proterozoic samples mimics the bimodal distribution of Archean and Paleoproterozoic dates from Neoproterozoic Cordilleran miogeoclinal strata and the Mesoproterozoic Purcell Supergroup (Fig. 5) (Ross and Parrish 1991; Gehrels and Ross 1998; Ross and Villeneuve 2003). The bimodal distribution and virtual absence of grains between 2.00 and 2.50 Ga were interpreted by Ross and Parrish (1991) to characterize a provenance from an exposed shield in western Canada. The zircon age distribution from this study matches well with basement domains in the subsurface of southern Alberta, specifically the Rimbey (1.79–1.85 Ga), Thorsby (1.91–2.38 Ga), and Hearne (2.50– 4.00 Ga) provinces (Fig. 6). If the craton beneath southern Alberta had been the sediment source, however, the 1.91– 2.38 Ga Thorsby domain (and the 2.32 Ga Wabamun domain) should have also provided zircons between 2.00 and 2.40 Ga, but our record contains none from that interval (Fig. 4). Similarly, because of the lack of zircons between 1460 and 1920 Ma, and in particular from 1500 and 1610 Ma, the North American magmatic gap of Ross and Villeneuve (2003), the age spectrum for unit 1 suggests that there was no significant input from the Mesoproterozoic Belt Basin to the south (Fig. 6). In a reconstruction of basement domains beneath the southern Canadian Cordillera, Ross and Parrish (1991) postulated
that the 1.84–1.87 Ga Fort Simpson domain extended to the west of our study area along the present-day coordinates of the Monashee complex. The complex was interpreted by Loveridge et al. (1981) as a potential source for a 1781 Ma outsized granitic clast from the Neoproterozoic Toby Formation (Windermere Supergroup, eastern side of the Rocky Mountain Trench). Crowley (1997) recovered zircons from deformed orthogneiss and paragneiss of the Monashee complex ranging from 1.73 to 2.04 Ga. This interval is consistent with the dominant population of zircons recovered from unit 1 and supports derivation of sediments from a Monashee-like source. Additional data are required to determine whether this source was located to the east (e.g., Brown 2004) or west (e.g., Thompson et al. 2006) of our study area in Late Proterozoic. Although based on two grains, the “Grenvillian”-aged zircons are unique relative to the Neoproterozoic and Cambrian age spectra presented in Fig. 5 for miogeoclinal strata, and at the very least demonstrate that a source terrain of that age was exposed. The nearest presently exposed region with Grenville-aged zircons is in the southwestern United States more than 1500 km to the south, where Neoproterozoic and Cambrian strata are dominated by 1.00–1.30 Ga zircons derived from local granitic sources (particularly 1.10 Ga; Gehrels et al. 1995; Gehrels and Stewart 1998; Gehrels 2000). Other possible distant sources are located in northwestern Canada, where Neoproterozoic strata are dominated by 1.00–1.30 Ga zircons (Rainbird et al. 1992, 1996). Growing evidence indicates that proximal 1.00–1.30 Ga sources were present along and outboard of the Canadian Cordilleran margin. Parrish and Reichenbach (1991, p. 1237) documented Grenville-aged zircon in Mesozoic diatremes in southern British Columbia and postulated the existence of “… yet undiscovered intrusions within the distal part of the crystalline basement of western Canada.” Numerous studies (Ross et al. 1991, 2005; Gehrels et al. 1995; Roback and Walker 1995; Gehrels and Ross 1998) have suggested the presence of Grenville-aged plutonic and magmatic rocks along and (or) outboard of the Cordilleran margin. Erdmer et al. (2002) recovered a cobble-sized igneous clast -1 kg in mass from metaconglomerate in the Nicola horst that yielded a concordant zircon date of 1038 ± 9 Ma (see Fig. 6 for location); they proposed a nearby source on the basis of the size of the clast. They also reported -996, 1030, and 1058 Ma zircons from the same metaconglomerate and hypothesized that rocks in the Nicola horst, part of the proposed Quesnellia terrane, were © 2007 NRC Canada
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Fig. 5. U–Pb date spectra of single detrital zircon grains from this study compared with data from miogeoclinal strata in southern British Columbia. Compilation from Ross and Bowring (1990), Ross and Parrish (1991), Smith and Gehrels (1991), Ross et al. (1993, 1997), and Gehrels and Ross (1998) for miogeoclinal strata in southern British Columbia and Alberta.
part of more ancient continental crust. Although that interpretation remains to be tested, it challenges paleogeographic models based on biogeographic and paleomagnetic indicators which suggest that Quesnellia underwent substantial north (and east?) translation prior to its accretion to the margin and is, therefore, allochthonous (e.g., Monger et al. 1982). Recent geochemical and isotopic data, however, support a pericratonic origin for Quesnellia (Unterschutz et al. 2002; Peterson et al. 2004). Thus, given the absence of 1.00–1.30 Ga magmatism to the east of the present study area, it is possible that -1.00 Ga zircons in unit 1 were derived from an exposed “outboard” source of Proterozoic continental crust. In summary, the zircon population in unit 1 shows affinity with North American continental crust; however, additional data are required to determine whether the zircons were derived from an outboard and (or) an eastern source. The data also indicate that the upper part of unit 1 cannot be older than Neoproterozoic. Since the sampled intervals occur stratigraphically above an amphibolite within the Monashee complex cover sequence dated at 541 Ma (Parrish 1995), unit 1 is probably of early Paleozoic age. We know that it is older than the overlying mid-Devonian Chase Formation (see the next section). Our data are insufficient to further constrain the age of the upper part of unit 1.
Chase Formation In contrast with Neoproterozoic and Cambrian miogeoclinal units in southern British Columbia, middle to late Paleozoic miogeoclinal strata display a wide range of detrital zircon dates, reflecting likely derivation from different source regions (Fig. 5). The detrital distribution of the Chase Formation matches with distributions in Paleozoic miogeoclinal strata in the following ways: (i) mid-Paleozoic zircons are found in Pennsylvanian miogeoclinal strata, (ii) Grenville-aged zircons occur in Ordovician and Pennsylvanian strata, (iii) the interval between -1.75 and 2.00 Ga is generally well represented, and (iv) >2.0 Ga zircons are common. However, there are also noticeable disparities: (i) the subordinate population between -0.85 and 0.95 Ga is unmatched anywhere in miogeoclinal strata from Alaska to the southwestern United States (Figs. 5, 7), and (ii) the subordinate group of zircons between 1.30 and 1.55 Ga is more abundant in our study. The predominance of >1.75 Ga zircons here matches well with basement domains of the buried western craton. Figure 6 shows that most of the >1.40 Ga zircons could have been transported from proximal basement domains or recycled from local sedimentary successions (e.g., miogeocline, Kootenay Arc, Belt Basin), i.e., within 400–500 km of the study area. The buried craton in southern Alberta includes © 2007 NRC Canada
Lemieux et al.
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Fig. 6. Schematic map of the basement domains of the western Canadian Shield and buried craton, the Canadian Cordilleran miogeocline, the Belt Basin, and gneiss complexes in southern British Columbia and northwestern United States. The heavy dashed line marks the Fort Simpson magnetic trend (FSMT) (Cook et al. 1992). Complexes: FC, Frenchman Cap; GC, Grand Forks complex; MG, Malton gneiss; OD, Okanagan dome; PC, Priest River complex; TO, Thor–Odin; VC, Valhalla complex; VG, Vaseaux gneiss. Basement provinces of the Canadian Shield and buried craton: 1, Fort Simpson; 2, Hottah; 3, Great Bear; 4, Coronation; 5, Slave; 6, Nahanni; 7, Nova; 8, Kiskatinaw; 9, Buffalo Head, Chinchaga, Thorsby, and Wabamun; 10, Rimbey and Taltson; 11, Rae; 12, Lacombe; 13, Hearne. Other features: GSL, Great Slave Lake; NH, Nicola horst. Modified from Gehrels and Ross (1998) and Ross and Villeneuve (2003).
crustal domains between 1.78 and 4.00 Ga. The -1.40– 1.75 Ga zircons may have been recycled from Mesoproterozoic Belt–Purcell Supergroup strata of the Belt Basin, which include abundant zircons between 1460 and 1920 Ma (Ross and Villeneuve 2003). The Salmon River – Priest River region of Idaho and eastern Washington is also characterized by 1.36–1.62 Ga zircon (Gehrels and Ross 1998). Whether these sources were exposed in mid-Devonian time along “Montania” arch (e.g., Porter et al. 1982), however, is uncertain.
Figure 7 compares our results with those from Devonian miogeoclinal strata along the western margin of North America as a means of addressing the influence of longshore sediment transport from remote regions or possible sediment influx from areas dominated by igneous suites not recognized locally. Detrital zircon populations in Devonian miogeoclinal strata in east-central Alaska and northern British Columbia are dominated by dates >1.80 Ga, with several occurrences between -1.80 and 2.00 Ga and at -2.70 Ga © 2007 NRC Canada
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Fig. 7. U–Pb date spectra of single detrital zircon grains for Devonian miogeoclinal strata along the North American Cordilleran margin. Data for east-central Alaska reported in Gehrels et al. (1999); data for northern British Columbia reported in Gehrels and Ross (1998) and Ross et al. (1993); data for Nevada reported in Gehrels and Dickinson (1995); and data for Sonora reported in Gehrels and Stewart (1998). Data for the Chase Formation are from this study.
(Fig. 7), consistent with derivation from adjacent basement rocks of the buried craton. These ages are rare in the southwestern United States. Strata from east-central Alaska also yielded several -430 Ma zircons, likely shed from an igneous source along or outboard of the margin (Gehrels et al. 1999). Zircons between 1.00 and 1.80 Ga were also recovered. In strata from northern British Columbia, no zircons younger than Paleoproterozoic have been documented. Compiled detrital zircon dates of Paleozoic miogeoclinal strata in western Nevada and northern California are dominated by 1.70 Ga zircons, and such dates are virtually absent in strata to the south; and (ii) 1.00–1.20 Ga zircons are present in both the Chase Formation and strata in east-central Alaska. On the basis of similarities between the zircon dates in Devonian miogeoclinal strata and the ages of adjacent basement domains, Gehrels et al. (1995) ruled out significant (1000 km scale) longshore transport along the Cordilleran margin in Devonian time. An exposed middle Paleozoic source is indicated by the Devonian zircons in the Chase Formation. Except for the 368 Ma Ice River alkaline intrusive complex in the southern Rocky Mountains (Parrish et al. 1987), mid-Paleozoic magmatic activity in the Cordillera is unknown to the east but is documented west of our study area (e.g., Okulitch 1985). Erdmer et al. (2002) recovered middle Paleozoic zircons from metaconglomerate (described earlier) and schist in the Nicola horst and suggested derivation from a proximal source. The © 2007 NRC Canada
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two Silurian clasts recovered by Roback et al. (1994) (Fig. 3) also support the hypothesis of a proximal source. The 561 Ma zircon from the Chase Formation has magmatic counterparts in southern British Columbia; Colpron et al. (2002) obtained a concordant zircon date of 569 Ma from volcanic rocks of the Hamill Group in the northern Selkirk Mountains. Erdmer et al. (2001, p. 1014) dated several Ediacaran (U–Pb upper intercept of 555 Ma) zircons in a metaconglomerate from the Spa Creek assemblage, approximately 20 km west of the Okanagan Valley, and concluded that the “… clasts are too large and too numerous and the spectrum of zircon ages too limited to support the possibility of a distal, intercratonic source.” The Chase Formation also includes a number of zircons between -1000 and 1300 Ma. Evidence presented earlier leads us to suggest local derivation from exposed Proterozoic continental crust. The origin of -0.85–0.95 Ga zircons, essentially absent from the Cordilleran stratigraphic record, remains elusive: one explanation is a local magmatic source. Gehrels and Ross (1998; see also Cook et al. 1992) suggested that plutons related to 1.30–0.80 Ga orogenic activity in northwestern Canada (Fort Simpson magnetic trend in Fig. 6) provided zircon of these ages. That hypothesis, however, implies significant (>1200 km) southerly longshore transport for which there is little evidence (Gehrels et al. 1995). If this area was the source, 0.80–1.30 Ga zircons would have likely populated Devonian miogeoclinal strata in present-day northern British Columbia, but no zircons younger than Paleoproterozoic have been reported there (Fig. 7). Thus, although the Chase Formation is characterized by a broad spectrum of ages, it includes abundant zircon compatible with North American continental margin strata. Comparison with Nd isotopic data If the Chase Formation was ultimately derived from North America, matches should exist between data from this study and Nd isotopic ratios from miogeocline strata (e.g., Boghossian et al. 1996) (Fig. 8). A total of 10 samples from the Chase Formation were analyzed for Sm–Nd isotopes; sample location is shown in Fig. 2 and listed in Table 2 (analytical procedures in Appendix A). For the purpose of εNd(T) calculation, a depositional age of 380 Ma was assumed. The samples show a limited range of εNd(T) values from –10.8 to –6.7. In miogeoclinal strata, Nd-isotope data record a major shift in εNd(T) from –22.0 to –14.0 in pre-Devonian strata to –9.5 to 6.5 in younger strata (Boghossian et al. 1996) (Fig. 8). By comparison with the miogeoclinal strata, the Nd data from the Chase Formation are consistent with a Devonian miogeoclinal signature. There is also a positive correlation between whole rock Nd depleted mantle model ages (TDM) and U–Pb results from zircons. The TDM model age of a clastic sedimentary rock is generally interpreted to represent the average crustal residence age of the source region (McLennan and Hemming 1992; Yamashita et al. 2000). Except for one sample with the highest Sm/Nd ratio (sample 02TWL225), which yielded a TDM of 2.26 Ga, the Chase Formation samples have TDM model ages between 1.54 and 1.91 Ga (Table 2). This range matches well the dominance of U–Pb zircon dates between 1.60 and 1.95 Ga.
1689 Fig. 8. Comparative plot showing εNd values for samples from Upper Arrow Lake and the Canadian Cordilleran miogeocline in Alberta (from Boghossian et al. 1996).
Tectonic implications Most units exposed in the northern part of the Kootenay Arc and along Upper Arrow Lake have been interpreted as part of the pericratonic Kootenay terrane (e.g., Wheeler et al. 1991). Colpron and Price (1995) proposed links between North American miogeoclinal strata and the outboard Paleozoic rocks of the Kootenay Arc (i.e., Lardeau and Milford groups). Smith and Gehrels (1991) postulated that the boundary between rocks of North American affinity and allochthonous units must be located outboard of the Milford Group, i.e., west of the Kootenay Arc. Recent field study in the northwest Kootenay Arc region and along Upper Arrow Lake, i.e., where the transition between autochthonous and allochthonous crust was inferred, has demonstrated the persistence of a coherent stratigraphic succession and the absence of a crustal break (e.g., terrane boundary; see Lemieux et al. 2003, 2004; Lemieux 2006). These observations are supported by the detrital zircon distribution in unit 1 and in quartzite of the Chase Formation and make an accreted origin for these two units unlikely. Deposition of both units as part of the North American margin succession is therefore implied. Thompson et al. (2006, p.437) proposed a model in which a block of North American crust “… defined the outboard (western) side of the continental margin during the Neoproterozoic and early Paleozoic” and noted that the suggestion of an outer high along the western margin of North America is not new (e.g., Roback et al. 1994; Ferri 1997). In the model of Thompson et al., the crustal block remained relatively high, standing from Paleoproterozoic through early Paleozoic time, and allowed for the accumulation of a continental margin prism between it and the craton, which leads to the suggestion that unit 1 would represent an outboard equivalent of the miogeocline. Our data neither rule out nor support that model but do support the existence of a nearby exposed source of continental affinity during the Neoproterozoic and (or) early Paleozoic. The broad spectrum of detrital zircon dates in the Chase Formation makes it difficult to single out potential source regions. Given the stratigraphic and depositional relationships linking unit 1 and the Chase Formation, however, we infer that this Devonian quartzite was deposited in close proximity to an outboard block of continental crust. The data support sediment dispersal from nearby source(s); that these sources were to the west remains to be tested. That interpretation applies to the entire Chase Formation between Upper © 2007 NRC Canada
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Can. J. Earth Sci. Vol. 44, 2007 Table 2. Nd and Sm concentrations and isotopic data. UTM coordinates Sample No.
Northing
Easting
Sm (ppm)
02TWL225 02TWL226 02TWL260 02TWL306 02TWL307 02TWL316 02TWL358 02TWL365 03TWL448 04TWL025
5556302 5554295 5558632 5556993 5556107 5555316 5549759 5549958 5560722 5602850
436021 431546 427687 422856 419098 420126 434951 436650 426234 435683
0.74 2.77 1.46 1.11 0.69 1.67 1.03 1.81 1.07 2.02
Nd (ppm)
147
Sm 144 Nd
143
3.34 15.21 7.78 5.97 3.76 8.80 5.52 9.42 5.71 11.95
0.1339 0.1102 0.1138 0.1122 0.1118 0.1149 0.1132 0.1163 0.1130 0.1022
0.511974±16 0.511998±4 0.511993±7 0.512096±6 0.511884±6 0.512012±6 0.511949±5 0.512045±6 0.511899±13 0.512036±13
144
Nd (±2SE) Nd
TDM (Ga)
εNd(380)
2.26 1.71 1.78 1.60 1.91 1.77 1.83 1.74 1.91 1.54
–10.1 –8.5 –8.8 –6.7 –10.8 –8.5 –9.6 –7.9 –10.6 –7.4
Fig. 9. U–Pb age spectra of single detrital zircon grains for the interpreted Slide Mountain and Quesnellia terranes in the southern Cordillera. Data for Quesnellia terrane reported in Roback and Walker (1995); data for Slide Mountain terrane reported in Roback et al. (1994). Data for the Chase Formation are also shown (this study).
Arrow Lake and the town of Chase, west of the Okanagan Valley. The western limit of rocks with established North American affinity thus lies west of the Okanagan Valley and supports the hypothesis that the Chase Formation is an outboard equivalent of the Cordilleran miogeocline. In light of other isotopic data from the southern Canadian Cordillera, the heterogeneously extended former margin might reach even farther west. Data from adjacent crustal domains (terranes) in southeastern British Columbia are scarce (Fig. 9); detrital zircons from the Mississippian McHardy assemblage and Permian to Lower Triassic Mount Roberts Formation included in the Slide Mountain and Quesnellia terranes, respectively, support sedimentologic ties with the North American craton (Roback et al. 1994; Roback and Walker 1995). Similarly, Triassic and Jurassic strata included in the Quesnellia terrane in south-central British Columbia have been interpreted to have been deposited onto the continental margin and (or) influenced by continent-derived material (Unterschutz et al. 2002; Peterson
et al. 2004); the notion of additional outboard continental crust is also inferred from the presence of Proterozoic continental rocks beneath the Triassic Nicola arc succession in the Nicola horst (Erdmer et al. 2002).
Conclusions U–Pb geochronological analysis of detrital zircon in Proterozoic and mid-Paleozoic successions of southeastern British Columbia suggests that both units were derived from source regions dominated by >1.75 Ga zircon populations. This is consistent with derivation mostly from sources with North American affinity. Evidence suggests that unit 1 was derived from an exposed source of Proterozoic continental crust. The mid-Devonian Chase Formation detrital signature records mid-Paleozoic, Ediacaran, 850–1300 Ma, and 1400– 1750 Ma source rocks. This age spectrum prevents further discrimination of potential source regions, but we propose that the Chase Formation was deposited in close proximity © 2007 NRC Canada
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to a source of North American continental crust. Nd isotopic characteristics of the Chase Formation also support derivation from proximal North American sources. On the basis of these interpretations (i) Proterozoic and mid-Paleozoic zircons show affinity with rocks of the ancient North American margin; (ii) unit 1 and the Chase Formation represent outboard extensions of the Cordilleran miogeoclinal succession, i.e., significantly extend the known surface area of the ancient margin; and (iii) Proterozoic to Mesozoic rocks of North American affinity likely extended yet farther west of the study area.
Acknowledgments This work was supported by Natural Sciences and Engineering Research Council of Canada (NSERC) graduate scholarships awarded to Y. Lemieux, NSERC research grants to P. Erdmer, and funding of the Geological Survey of Canada Ancient Pacific Margin National Mapping Program (NATMAP). The radiogenic isotope facility at the University of Alberta is supported by an NSERC Major Facility Access grant. M. Colpron, G. Gehrels, and associate editor B. Davis reviewed the manuscript and offered constructive comments. The first author acknowledges support from the University of Alberta Graduate Students’ Association Professional Development Grant. T. Chacko, J. Waldron, and M. Unsworth reviewed an earlier version of this manuscript.
References Archibald, D.A., Glover, J.K., Price, R.A., Farrar, E., and Carmichael, D.M. 1981. Geochronology and tectonic implications of magmatism and metamorphism. Southern Kootenay arc and neighbouring regions, southeastern British Columbia. Part I: Jurassic to mid-Cretaceous. Canadian Journal of Earth Sciences, 20: 1891–1913. Ashton, K.E., Heaman, L.M., Lewry, J.F., Hartlaub, R.P., and Shi, R. 1999. Age and origin of the Jan Lake Complex: a glimpse at the buried Archean craton of the Trans-Hudson Orogen. Canadian Journal of Earth Sciences, 36: 185–208. Boghossian, N.D., Patchett, P.J., Ross, G.M., and Gehrels, G.E. 1996. Nd isotopes and the source of sediments in the miogeocline of the Canadian Cordillera. Journal of Geology, 104: 259–277. Bond, G., and Kominz, M.A. 1984. Construction of tectonic subsidence curves for the early Paleozoic miogeocline, southern Rocky Mountains: Implications for subsidence mechanisms, age of breakup, and crustal thinning. Geological Society of America Bulletin, 95: 155–173. Brown, R.L. 2004. Thrust-belt accretion and hinterland underplating of orogenic wedges — An example from the Canadian Cordillera. In Thrust tectonics and hydrocarbon systems. Edited by K.R. McClay. American Association of Petroleum Geologists, Memoir 82, pp. 51–64. Brown, R.L., Carr, S.D., Johnson, B.J., Coleman, V.J., Cook, F.A., and Varsek, J.L. 1992. The Monashee décollement of the southern Canadian Cordillera: a crustal-scale shear zone linking the Rocky Mountain Foreland belt to lower crust beneath accreted terranes. In Thrust tectonics. Edited by K.R. McClay. Chapman and Hall, London, UK. pp. 357–365. Carr, S.D. 1991. Three crustal zones in the Thor–Odin–Pinnacles area, southern Omineca Belt, British Columbia. Canadian Journal of Earth Sciences, 28: 2003–2023.
1691 Colpron, M., and Price, R.A. 1995. Tectonic significance of the Kootenay terrane, southeastern Canadian Cordillera: An alternative model. Geology, 23: 25–28. Colpron, M., Logan, J.M., and Mortensen, J.K. 2002. U–Pb zircon age constraint for late Neoproterozoic rifting and initiation of the lower Paleozoic passive margin of western Laurentia. Canadian Journal of Earth Sciences, 39: 133–143. Cook, F.A., Dredge, M., and Clark, E.A. 1992. The Proterozoic Fort Simpson structural trend in northwestern Canada. Geological Society of America Bulletin, 104: 1121–1137. Crowley, J.L. 1997. U–Pb geochronologic constraints on the cover sequence of the Monashee complex, Canadian Cordillera: Paleoproterozoic deposition on basement. Canadian Journal of Earth Sciences, 34: 1008–1022. Erdmer, P., Heaman, L., Creaser, R.A., Thompson, R.I., and Daughtry, K.L. 2001. Eocambrian granite clasts in southern British Columbia shed light on Cordilleran hinterland crust. Canadian Journal of Earth Sciences, 38: 1007–1016. Erdmer, P., Moore, J.M., Heaman, L., Thompson, R.I., Daughtry, K.L., and Creaser, R.A. 2002. Extending the ancient margin outboard in the Canadian Cordillera: record of Proterozoic crust and Paleocene regional metamorphism in the Nicola horst, southern British Columbia. Canadian Journal of Earth Sciences, 39: 1605–1623. Ferri, F. 1997. Nina Creek Group and Lay Range Assemblage, north-central British Columbia: remnants of late Paleozoic oceanic and arc terranes. Canadian Journal of Earth Sciences, 34: 854–874. Fyles, J.T., and Eastwood, G.E.P. 1962. Geology of the Ferguson area, Lardeau District, British Columbia. British Columbia Department of Mines and Petroleum Resources, Bulletin 45. Gehrels, G.E. 2000. Introduction to detrital zircon studies of Paleozoic and Triassic strata in western Nevada and northern California. In Paleozoic and Triassic paleogeography and tectonics of western Nevada and northern California. Edited by M.J. Soreghan and G.E. Gehrels. Geological Society of America, Special Paper 347, pp. 1–17. Gehrels, G.E., and Dickinson, W.R. 1995. Detrital zircon provenance of Cambrian to Triassic miogeoclinal and eugeoclinal strata in Nevada. American Journal of Science, 295: 18–48. Gehrels, G.E., and Ross, G.M. 1998. Detrital zircon geochronology of Neoproterozoic to Permian miogeoclinal strata in British Columbia and Alberta. Canadian Journal of Earth Sciences, 35: 1380–1401. Gehrels, G.E., and Stewart, J.H. 1998. Detrital zircon geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico. Journal of Geophysical Research, 103: 2471– 2487. Gehrels, G.E., Dickinson, W.R., Ross, G.M., Stewart, J.H., and Howell, D.G. 1995. Detrital zircon reference for Cambrian to Triassic miogeoclinal strata of western North America. Geology, 23: 831–834. Gehrels, G.E., Johnsson, M.J., and Howell, D.G. 1999. Detrital zircon geochronology of the Adams Argillite and Nation River Formation, east-central Alaska, U.S.A. Journal of Sedimentary Research, 69: 135–144. Glombick, P., Thompson, R.I., Erdmer, P., and Daughtry, K.L. 2006. A reappraisal of the tectonic significance of early Tertiary low-angle shear zones exposed in the Vernon map area (82 L), Shuswap metamorphic complex, southeastern Canadian Cordillera. Canadian Journal of Earth Sciences, 43: 245–268. Hedley, M.S. 1955. Lead–zinc deposits of the Kootenay Arc. Western Miner, July 1955, pp. 31–35. © 2007 NRC Canada
1692 Hyndman, D.W. 1968. Petrology and structure of Nakusp map-area, British Columbia. Geological Survey of Canada, Bulletin 161. Klepacki, D.W., and Wheeler, J.O. 1985. Stratigraphic and structural relations of the Milford, Kaslo and Slocan groups, Goat Range, Lardeau and Nelson map area, British Columbia. In Current research, part A. Geological Survey of Canada, Paper 85-1A, pp. 277–286. Lemieux, Y. 2006. Structure, geochronology and thermobarometry of the eastern flank of the Shuswap metamorphic complex in the Upper Arrow Lake area, southeastern British Columbia. Ph.D. thesis, University of Alberta, Edmonton, Alta. Lemieux, Y., Thompson, R.I., and Erdmer, P. 2003. Stratigraphy and structure of the Upper Arrow Lake area, southeastern British Columbia: new perspectives for the Columbia River Fault Zone. In Current research. Geological Survey of Canada, Paper 2003-A7. Lemieux, Y., Thompson, R.I., and Erdmer, P. 2004. Stratigraphic and structural relationships across the Columbia River fault zone, Vernon and Lardeau map areas, British Columbia. In Current research. Geological Survey of Canada, Paper 2004-A3. Loveridge, W.D., Leech, G.B., Stevens, R.D., and Sullivan, R.W. 1981. Zircon and monazite age of a granitic clast in Toby conglomerate (Windermere Supergroup), Canal Flats, British Columbia. In Rb–Sr and U–Pb isotopic age studies, Report 4. Geological Survey of Canada, Paper 81-1C, pp. 131–134. McLennan, S.M., and Hemming, S. 1992. Samarium/neodymium elemental and isotopic systematics in sedimentary rocks. Geochimica et Cosmochimica Acta, 56: 887–898. Monger, J.W.H., Price, R.A., and Tempelman-Kluit, D.J. 1982. Tectonic accretion and the origin of the two major metamorphic and plutonic welts in the Canadian Cordillera. Geology, 10: 70–75. Okulitch, A.V. 1985. Paleozoic plutonism in southeastern British Columbia. Canadian Journal of Earth Sciences, 22: 1409–1424. Parrish, R.R. 1995. Thermal evolution of the southeastern Canadian Cordillera. Canadian Journal of Earth Sciences, 32: 1618–1642. Parrish, R.R., and Reichenbach, I. 1991. Age of xenocrystic zircon from diatremes of western Canada. Canadian Journal of Earth Sciences, 28: 1232–1238. Parrish, R.R., Heinrich, S., and Archibald, D. 1987. Age of the Ice River Complex, southeastern British Columbia. In Radiogenic age and isotopic studies, Report 1. Geological Survey of Canada, Paper 87-2, pp. 33–37. Parrish, R.R., Carr, S.D., and Parkinson, D.L. 1988. Eocene extensional tectonics and geochronology of the southern Omineca Belt, British Columbia and Washington. Tectonics, 7: 181–212. Peterson, N.T., Smith, P.L., Mortensen, J.K., Creaser, R.A., and Tipper, H.W. 2004. Provenance of Jurassic sedimentary rocks of south-central Quesnellia, British Columbia: implications for paleogeography. Canadian Journal of Earth Sciences, 41: 103–125. Porter, J.W., Price, R.A., and McCrossan, R.G. 1982. The Western Canada Sedimentary Basin. Philosophical Transactions of the Royal Society of London, Series A, Mathematical and Physical Sciences, 305: 169–192. Price, R.A. 1994. Cordilleran tectonics and the evolution of the Western Canadian Sedimentary Basin. In Geological atlas of the Western Canada Sedimentary Basin. Edited by G.D. Mossop and I. Shesten. Canadian Society of Petroleum Geologists, Calgary, Alta., and Alberta Research Council, Edmonton, Alta., pp. 13–24. Rainbird, R.H., Heaman, L.M., and Young, G.M. 1992. Sampling Laurentia: Detrital zircon geochronology offers evidence for an extensive Neoproterozoic river system originating from the Grenville orogen. Geology, 20: 351–354.
Can. J. Earth Sci. Vol. 44, 2007 Rainbird, R.H., Jefferson, C.W., and Young, G.M. 1996. The early Neoproterozoic sedimentary Succession B of northwestern Laurentia: Correlations and paleogeographic significance. Geological Society of American Bulletin, 20: 454–470. Read, P.B. 1973. Petrology and structure of Poplar Creek map-area, British Columbia. Geological Survey of Canada, Bulletin 193. Read, P.B. 1975. Lardeau Group, Lardeau map-area, west half (82K west half), British Columbia. In Current research, part A. Geological Survey of Canada, Paper 75-1A, pp. 29–30. Read, P.B. 1979. Relationship between the Shuswap Metamorphic Complex and the Kootenay Arc, Vernon east-half, southern British Columbia. In Current research, part A. Geological Survey of Canada, Paper 79-1A, pp. 37–40. Read, P.B., and Brown, R.L. 1981. Columbia River fault zone: southeastern margin of the Shuswap and Monashee complexes, southern British Columbia. Canadian Journal of Earth Sciences, 18: 1127–1145. Read, P.B., and Wheeler, J.O. 1976. Geology, Lardeau west-half, British Columbia. Geological Survey of Canada, Open File 432. Scale 1 : 250 000. Reesor, J.E., and Moore, J.M. 1971. Petrology and structure of Thor–Odin gneiss dome, Shuswap metamorphic complex, British Columbia. Geological Survey of Canada, Bulletin 195. Roback, R.C., and Walker, N.W. 1995. Provenance, detrital zircons U–Pb geochronometry, and tectonic significance of Permian to Lower Triassic sandstone in southeastern Quesnellia, British Columbia and Washington. Geological Society of America Bulletin, 107: 665–675. Roback, R.C., Sevigny, J.H., and Walker, N.W. 1994. Tectonic setting of the Slide Mountain terrane, southern British Columbia. Tectonics, 13: 1242–1258. Ross, G.M., and Bowring, S.A. 1990. Detrital zircon geochronology of the Windermere Supergroup and the tectonic assembly of the southern Canadian Cordillera. Journal of Geology, 98: 879–893. Ross, G.M., and Parrish, R.R. 1991. Detrital zircon geochronology of metasedimentary rocks in the southern Omineca Belt, Canadian Cordillera. Canadian Journal of Earth Sciences, 28: 1254–1270. Ross, G.M., and Villeneuve, M.E. 2003. Provenance of the Mesoproterozoic (1.45 Ga) Belt basin (western North America): Another piece in the pre-Rodinia paleogeographic puzzle. Geological Society of America Bulletin, 115: 1191–1127. Ross, G.M., McMechan, M.E., and Hein, F.J. 1989. Proterozoic history: the birth of the miogeocline. In Western Canada sedimentary basin, a case history. Edited by B.D. Rickets. Canadian Society of Petroleum Geologists, Calgary, Alta., pp. 79–104. Ross, G.M., Parrish, R.R., Villeneuve, M.E., and Bowring, S.A. 1991. Geophysics and geochronology of the crystalline basement of the Alberta Basin, western Canada. Canadian Journal of Earth Sciences, 28: 512–522. Ross, G.M., McNicoll, V.J., Geldsetzer, H.H.J., Parrish, R.R., Carr, S.D., and Kinsman, A. 1993. Detrital zircon geochronology of Siluro-Devonian sandstones, Rocky Mountains, northeastern British Columbia. Bulletin of Canadian Petroleum Geology, 41: 349–357. Ross, G.M., Gehrels, G.E., and Patchett, P.J. 1997. Provenance of Triassic strata in the Cordilleran miogeocline, western Canada. Bulletin of the Canadian Society of Petroleum Geologists, 45: 461–473. Ross, G.A., Friedman, R., and Mortensen, J.K. 2005. Detrital zircon and monazite from the Hyland Group (northern Canadian Cordillera and Alaska): Evidence for intraCordilleran “Grenville” basement. Geological Society of America, Abstracts with Programs, Cordilleran Section, 37: 56. © 2007 NRC Canada
Lemieux et al. Simonetti, A., Heaman, L.M., Hartlaub, R.P., Creaser, R.A., McHattie, T.G., and Böhm, C. 2005. U–Pb zircon dating by laser ablation – MC–ICP–MS using new multiple ion counting Faraday collector array. Journal of Analytical Atomic Spectrometry, 20: 677–686. Smith, M.T., and Gehrels, G.E. 1991. Detrital zircon geochronology of Upper Proterozoic to lower Paleozoic continental margin strata of the Kootenay Arc: implications for the early Paleozoic tectonic development of the eastern Canadian Cordillera. Canadian Journal of Earth Sciences, 28: 1271–1284. Stacey, J.S., and Kramers, J.D. 1975. Approximation of terrestrial lead isotope evolution by a two-stage model. Earth and Planetary Science Letters, 26: 207–221. Thompson, R.I., and Daughtry, K.L. 1997. Anatomy of the Neoproterozoic–Paleozoic continental margin, Vernon map-area, British Columbia. In Current research, part A. Geological Survey of Canada, Paper 1997-A, pp. 145–150. Thompson, R.I., Glombick, P., Erdmer, P., Heaman, L., Lemieux, Y., Daughtry, K.L., and Friedman, R.L. 2006. Evolution of the Ancestral Pacific Margin, southern Canadian Cordillera: Insights from new geological maps. In Paleozoic evolution and metallogeny of pericratonic terranes at the ancient Pacific margin of North America, Canadian and Alaskan Cordillera. Edited by M. Colpron and J.L. Nelson. Geological Association of Canada, Special Paper 45, pp. 435–484. Unterschutz, J.L.E., Creaser, R.A., Erdmer, P., Thompson, R.I., and Daughtry, K.L. 2002. North American margin origin of Quesnel terrane strata in the southern Canadian Cordillera: Inferences from geochemical and Nd isotopic characteristics of Triassic metasedimentary rocks. Geological Society of American Bulletin, 114: 462–475. Wasserburg, G.J., Jacobsen, S.B., DePaolo, D.J., McCulloch, M.T., and Wen, T. 1981. Precise determination of Sm/Nd ratios, Sm and Nd abundances in standard solutions. Geochimica et Cosmochimica Acta, 45: 2311–2323. Wheeler, J.O., and McFeely, P. (Compilers). 1991. Tectonic assemblage map of the Canadian Cordillera. Geological Survey of Canada, Map 1712A. Scale 1 : 2 000 000. Wheeler, J.O., Brookfield, A.J., Gabrielse, H., Monger, J.W.H., Tipper, H.W., and Woodsworth, G.J. (Compilers). 1991. Terrane map of the Canadian Cordillera. Geological Survey of Canada, Map 1713A. Scale 1 : 2 000 000.
1693 Yamashita, K., Creaser, R.A., and Villeneuve, M.E. 2000. Integrated Nd isotopic and U–Pb detrital zircon systematics of clastic sedimentary rocks from the Slave Province, Canada: evidence for extensive crustal reworking in the early- to mid-Archean. Earth and Planetary Science Letters, 174: 283–299.
Appendix A: Analytical procedures Sm–Nd geochemistry Rock powders were weighed and totally spiked with a known amount of mixed 150Nd–149Sm tracer solution. Dissolution occurred in mixed 24N HF + 16N HNO3 media in sealed PFA Teflon vessels at 160 °C for 5 days. The fluoride residue was converted to chloride with HCl, and Nd and Sm were separated by conventional cation and orthophosphoric acid (HDEHP) based chromatography. Chemical processing blanks were
