combined AFT and AHe thermal models suggest erosional cooling phases at main ..... of the CRS algorithm to drive convergence, and uses the observed age ...
Appendix A: Sample characterization and constraining geochronologic data Samples are presented from the Canadian Shield with bracketing thermochronology data. Data from nearby samples are given when information about the sample from this study requires additional thermal constraints. See Table S1 for samples dated in this paper and Table S2 for (U-Th)/He datum for western Superior province. Table S1: North American craton 40Ar/39Ar samples Sample
Longitude (DD) Latitude (DD) Rock type
Superior Province, ON 70 -90.659
52.945
WN-1
50.250
-95.841
pegmatite leucogranite/trondhjemite granite/granodiorite, Winnipeg River subprovince Lac du Bonnet Batholith
Grenville Province, QC OL-13 -76.509
45.779
syenogranite
Athabasca BF02-76B BF02-108B BF02-123A 02M133A
-105.198 -105.284 -105.312 -105.412
59.424 59.322 59.328 59.42
cross-cutting pegmatite, Chipman domain granitic segregation, Chipman domain granitic vein mafic granulite
Saskatchewan SK-KM-01 -103.196 SK-KM-02 -104.905 SK-KM-03 -104.897
54.085 54.814 57.841
K-feldspar granitoid foliate core K-feldspar granitoid foliate core pegmatite granite
Mid-Continent U.S.A. 95-11 -90.692 95-13 -90.726 IL-ST-3 -89.867 96-WIS-11 -88.109 WRB-3 -88.783 EC-8 -87.507 EC-13 -87.586 EC-25 -87.767
44.373 44.393 42.433 45.392 44.805 45.880 45.691 45.604
Neillsville Granite Hatfield Gneiss Illinois UPH3 basement granite core Athelstane Gneiss granite, Wolf River Batholith granite, East-Central Minnesota Batholith granite, East-Central Minnesota Batholith granite, East-Central Minnesota Batholith
Table S2: Sample #70 single grain apatite (U-Th)/He age Long. (DD)
Lat. (DD)
Corrected age (Ma)
Full unc. (Ma)
Analyt. unc. (Ma)
4He (mol)
U/Th/Sm (ppm)
eU (ppm)
Rs (μm)
Raw age
±
-90.659
52.945
531.53
31.89
11.52
3.564E-13
30.6/63.5 /217.8
45.5
61.97
408.07
7.92
403
40.3
8.81
2.678E-13
CRH-corr. age:
Ft 0.761
Table S2: Single-grain (U-Th)/He age for Superior Province sample #70. CRH-corrected age after methods of McDannell et al. (2018). All uncertainties are 1. eU = effective uranium concentration, Rs = spherical equivalent radius, Ft = FT correction.
Figure S2: (U-Th)/He apatite continuous ramped heating (CRH) screening result for sample #70. (A) Cumulative f-loss with increasing temperature for a single grain. This grain would fall into the anomalous category of McDannell et al., 2017. (B) Smoothed (12 pt. median) df spectrum shown in black with raw spectrum in red. Note the extreme 4He gas spikes and long gas tail at intermediate to high temperature. Blue curve shows the predicted volume diffusion (VD) df spectrum fit to the median-smoothed curve to correct the total-gas age and remove the anomalous non-VD components of gas.
Western Superior Province, Ontario Sample No. 70 is from the Archean North Caribou Terrane of the western Superior Province in Ontario Canada and is part of one of the oldest Archean cratonic cores in North America. The ca.
2.7 Ga collision of micro-continent blocks during the Uchi orogeny occurred from lateral platetectonic-like accretionary stacking of various proto-continents and oceanic fragments during multiple well-documented events (Percival et al., 2006; Percival et al., 2012; White et al., 2003). The craton stabilized by about 2.5 Ga after orogenesis cessation at 2.6 Ga, although some reactivation occurred ca. 1.9 Ga, and during failed rifting of the mid-continent in peripheral terranes near Lake Superior at ca. 1.1 Ga (Percival and Easton, 2007). This sample and others in the same area were dated and described in Van Lankvelt et al. (2016) and is denoted sample #72 in that paper. Most of the rocks in this region record high-temperature (>550-600°C) 2.6-3.1 Ga magmatic activity and hydrothermal alteration (Van Lankvelt et al., 2016). Sample #70 rock is a tonalite-trondjhemite granite (TTG) and nearby sample #71 has zircon and titanite U-Pb age of 2858 ± 5 Ma and 2854 ± 7 Ma, respectively, with Ti-in-zircon thermometry indicating zircon crystallization temperatures of 752 ± 37°C. Approximately 50-100 km to the east/southeast of sample #70, localized carbonatite dikes yield K-Ar biotite ages of 1014 ± 40 Ma and 1070 ± 40 Ma (Gittins et al., 1967; Wanless et al., 1967). The dikes in this part of Ontario are the southeastern extension of the ca. 1.27 Ga Mackenzie dike swarm originating at the Coppermine mantle plume LIP locus in the Slave Province (Hou, 2012).
Apatite fission-track ages from this region of Ontario are ca. 350-450 Ma (Kohn et al., 2005; Lorencak, 2003) and at Atikokan, Ontario (borehole ATK-1) to the southwest, near the Minnesota border, AFT range from 515 ± 72 to 376 ± 46 Ma from depths of 4 m to 993 m, respectively (Naeser and Crowley, 1990). Sample #70 was dated via (U-Th-Sm)/He analysis for this study using the continuous heating method (Idleman and Zeitler, 2014; Idleman et al., 2018; McDannell, 2017; McDannell et al., 2015; McDannell et al., 2018), which produced an alpha-
corrected single grain cooling age of 531.53 ± 31.89 Ma (2σ); uncorrected age: 408.07 ± 7.9 Ma (1σ), eU = 45.5 ppm, spherical equivalent radius, Rs = 62 μm). The CRH corrected age is 403 ± 40.3 Ma (2σ, analytical error).
Sample WN-1 is a granodiorite from the Winnipeg River Subprovince of the Superior craton taken from core at the deep borehole site at the Whiteshell Nuclear Research laboratory outside Winnipeg, Manitoba from the Lac du Bonnet Batholith that was emplaced 2665 ± 20 to 2568 ± 23 Ma (Everitt et al., 1996; Krogh et al., 1976). This sample was from 30.5 m depth and dated previously via
40
Ar/39Ar of biotite, yielding a late Kenoran age of 2291 ± 27 Ma (Hunt and
Roddick, 1988). This sample was then dated via 40Ar/39Ar of K-feldspar in 1990 by C. Roddick (pers. comm. with P. Zeitler) and was never published. The age spectrum presented here is from that laboratory experiment. AFT data from a borehole at the underground research lab where sample WN-1 was obtained shows ages of ca. 370-250 Ma, decreasing with depth. The sample URL-6-2 at nearly the same depth/elevation as WN-1 has an AFT age of 373 ± 29 Ma (Feinstein et al., 2009). Osadetz et al. (2002) also show AFT ages of ~300-400 Ma for SE Manitoba. Apatite fission-track thermochronology of Ontario and W. Manitoba show ages of ca. 350-500 Ma (Kohn et al., 2005). These data suggest these rocks have been cooler than ~110°C throughout the Phanerozoic. Further to the east where there are geologic constraints in the form of Ordovician sediments overlying crystalline basement near the Sudbury Igneous Complex, combined AFT and AHe thermal models suggest erosional cooling phases at main stages of the Appalachian Orogeny with episodic burial reheating and ensuing unroofing (Feinstein et al., 2009; Lorencak, 2003; Lorencak et al., 2004).
Grenville Province, Quebec The Grenville Province represents the remains of a deeply-eroded collisional mountain belt that formed primarily between 1.35 to 1.0 Ga (McLelland et al., 1996), bordering the eastern Superior Province. Sample OL13 is a syeno-granite from the Central Metasedimentary Belt (Otter Lake region of Quebec), ~75-100 km northwest of Ottawa. This area underwent upperamphibolite facies metamorphism at temperatures and pressures of 700 ± 50°C and 6.5-7.5 kbar (Kretz, 1994) during the Elzivirian and Ottawan phases of the Grenville orogeny. Titanite from this sample was dated via U-Pb LA-ICP-MS of different petrologic phase of the same sample giving concordant ages of 1025 ± 11 Ma, 1023 ± 7.8 Ma, 1029.7 ± 5.7 Ma for hornblende and hornblende-pyroxene granites (D. Schneider, pers. comm.). This sample is now used as the titanite U-Pb standard at the Geologic Survey of Canada where samples at the same outcrop as OL-13 gave a SHRIMP concordia age of 1017.1 ± 3.6 Ma and a TIMS U-Pb concordia age of 1014.8 ± 2.0 Ma (Sample OLT1) and a SHRIMP age of 1021.8 ± 2.4 Ma and TIMS age of 1018.1 ± 1.7 Ma for Sample TCB (Kennedy et al., 2010). The same sample as OL13, labled NC9-7, yields a biotite 40Ar/39Ar plateau age of 885.2 ± 4.3 Ma (total gas age: 875.6 ± 13.8 Ma) and a nearby sample NC9-8 (
