Table A. Sample co-ordinates from the eclogite-facies shear zone rocks.
Island	Locality	Sample	Longitude (E)	Latitude (N)	Altitude (mts)	
Vestvågøy	Vågje	HF-08-24a	33W0439035	7563024	22	
		HF-08-24b1	33W0439054	7563045	“	
		HF-08-24b2	“	“	“	
		HF-08-25a	33W0439213	7562902	8	
		HF-08-25b	“	“	“	
		HF-08-25c	“	“	“	
		HF-08-25d	33W0439236	7562890	18	
		HF-08-25e	33W0439242	7562892	-	
Flakstadøy	Myrland	HF-08-20b	33W0430973	7562597	10	
		Hf-08-20c2	“	“	“	
		Hf-08-20d	“	“	“	
		HF-08-21	33W0430964	7562593	“	
	Skagen	HF-08-15c	33W0428003	7555489	8	
		HF-08-15e	33W0428011	7555506	8	
		HF-08-15g	33W0428033	7555503	6	
		HF-08-16	33W0427918	7555544	6	

ANALYTICAL METHODS
Electron Microprobe Analyses
Quantitative chemical analyses were made at the University of Manitoba, Winnipeg, Canada. For the silicate minerals, analyses were obtained on an automated 4-spectrometer Cameca SX 100 electron probe by the wavelength dispersive x-ray method. Line transverses of 8 to 20 spots were conducted across minerals. Operating conditions were 15kV accelerating potential and a beam current of 20 nA. Peak counting times for each analyzed element were approximately 20 seconds on the following peaks: Na-Kα, F-Kα, Mg-Kα, Al-Kα, Si-Kα, K-Kα, Ti-Kα, Fe-Kα, Mn-Kα, Cl-Kα, Ca-Kα, Ba-Lα and Cr-Kα. Background counts were measured once in the beginning of line profiles and the same background counts were applied to the remainder of the spot analyses. For each spot analysis, a beam size of 5 µm was used. 
Radiogenic Isotope Analyses
Meaningful geological ages (e.g. ages that we consider to not be affected by 40ArE or inherited 87Sr) at ±2σ level reported in this work correspond to the divisions of the geological time scale of Walker & Geissman (2009) and are shown in Fig. 2.
Ar–Ar
Apparent 40Ar/39Ar ages of amphibole, muscovite, biotite, K-feldspar and sericite were obtained from rocks samples at the above localities. High-purity (> 99 %) unaltered mineral separates of fresh, non-weathered rocks were obtained by crushing, cleaning with deionised water, sieving into fractions approximating the grain sizes observed in thin section and finally handpicking with tweezers using a binocular microscope. All separates were cleaned in ethanol in an ultrasonic bath for 20 minutes and then washed again using deionised water. For each mineral separate, 10 mg of material were wrapped in Al foil as individual samples and stacked vertically in an Al canister (11.5 cm long x 2.0 cm diameter) with the irradiation standard Hb3gr hornblende [K/Ar age = 1072 ± 11 Ma (1σ)] (Roddick 1983; Turner et al. 1971). The samples were irradiated for 40-45 hours at the McMaster Nuclear Reactor, Hamilton, Ontario.
Step-heating 40Ar/39Ar analyses were performed in the 40Ar/39Ar Geochronology Laboratory at Queen’s University, Kingston, Canada. After irradiation, aliquots of both samples and standards were placed in small pits, 2 mm in diameter and 1.5 mm in depth, drilled in a Cu sample holder, which was placed beneath the sapphire viewport of a small, bakeable, stainless-steel chamber. Standards were fused in a single step, using a focused an Ar-ion laser (LEXEL 3500) and a CO2 laser (New Wave). The J value at various positions in the can was subsequently determined by second-order polynomial interpolation.
	For the 40Ar/39Ar step-heating analyses, the Ar-ion or CO2 laser beams were defocused to heat the entire sample and only refocused in the last step to fuse the sample. Samples were typically heated for 3 minutes for each step and stepwise-degassed using laser-power increments from 0.5 to 7.0 W using the Ar-ion laser or from 2.0 to 5.5% of power using the CO2 laser. The released gas was purified with a Ti sponge and Zr-Al getters, and analyzed using a MAP 216 noble gas mass spectrometer, with a Baur-Signer ion source and an electron multiplier. All ages were calculated using the decay constant as recommended by Steiger & Jäger (1977): λe = 0.581 x 10-10 a-1, λβ = 4.962 x 10-10 a-1 and 40K = 1.167 x 10-2 atom %. All isotope analyses were corrected for system blanks (typical blank values were 40 x10-13 and 75 x10-13 cm3 STP) run before analysing the gas, atmospheric contamination, and neutron-induced interferences (including the radioactive decay of the 37Ar and 39Ar isotopes). In order to examine the potential influence of Ar residing in alteration or inclusion phases within the minerals, Ca/K and Cl/K ratios of the minerals were calculated from their 37Ar/39Ar and 38Ar/39Ar ratios using the relations derived from the measured (37Ar/39Ar)/K and (38Ar/39Ar)/K of the flux monitor Hb3gr [K/Ar age = 1072 ± 11 Ma (1σ)]. A liquid nitrogen cold trap on the MAP 216 provided additional gas-cleaning before inletting into the mass spectrometer. Peaks from 36Ar to 40Ar were scanned 8 times each, the amounts were extrapolated back to the inlet time, and standard deviations at 1σ of the peaks were calculated. The peaks final values were obtained by the error-weighted line regression using the set of values obtained from each peak. The errors of the apparent ages (plateau and integrated ages) were calculated using the error propagation formula applied to the Ar/Ar age equation which also includes the error of the J-value. In this study, a plateau is defined as three or more contiguous gas fractions which have apparent ages indistinguishable at the 1σ level and which comprise over 50% of the 39Ar released from the sample.
	The publication of new decay constant by Renne et al. (2010): λe = 0.5755 x 10-10 a-1, λβ = 4.9737 x 10-10 a-1 was not taken into consideration for this paper. However, using the 40Ar/39Ar hastingsite plateau age of sample HF-08-24a as an example a recalculation yields a plateau age of 415.13 ± 1.12 Ma which correspond to a difference of 0.47 Ma younger than using the previous published decay constant (415.60 ± 1.12 Ma). Therefore, using the new decay constant does not substantially change the conclusions of this present paper.
Rb–Sr
All the analyses were conducted at the Radiogenic Isotope Facility at the University of Alberta. Pure mineral separates typically weighing 1–26 mg were leached in dilute (~0.7 N) hydrochloric acid (Brown et al. 1989) in an ultrasonic bath for ~30 min to remove trace carbonate minerals, prior to repeated rinses in ultrapure water. The leach-cleaned mica was spiked with a known amount of a mixed 84Sr–87Rb spike to enable isotope dilution analysis, and dissolved in a 5:1 mix of 24 N HF:16 N HNO3 in PFA Teflon containers. Strontium and Rb were separated by standard cation-exchange chromatographic methods (e.g. Holmden et al. 1996) and isotopic analyses of both elements were performed using Thermal Ionization Mass Spectrometry, a single Re filament, and the tantalum gel loading method. Strontium isotope analyses were performed using either a VG354 5-collector machine in multi-dynamic data collection mode, or a Micromass Sector54 9- collector machine in either multi-dynamic or static data collection mode. All analyses are corrected for variable mass fractionation using an exponential law and 86Sr/88Sr = 0.1194. Accuracy of the Sr isotopic composition was monitored using the NIST SRM987 Sr isotopic standard, and all isotopic ratios are reported relative to a value of 0.710245 for the NIST SRM987 Sr isotope standard. Long-term measured values of this standard are as follows. For the VG354 instrument from 1999 to 2001, 87Sr/86Sr = 0.710269 ± 21 (1σ, n = 50). For the Sector54 instrument, from 2000 to 2002 87Sr/86Sr = 0.710279 ± 28 (1σ, n = 28), and from 2002 to 2003, 87Sr/86Sr = 0.710258 ± 22 (1σ, n = 19, following machine relocation). Rubidium isotopic analysis used either a Micromass MM30 single collector instrument in peak-hopping mode, or the VG354 or S54 machines in static mode. For all Rb analyses, a correction factor is applied to all measured ratios to account for instrumental mass fractionation in each mass spectrometer, based upon long-term monitoring of the NIST SRM984 Rb isotopic standard value relative to the recommended value of 2.59265 (Steiger & Jäger 1977). Chemical processing blanks are < 150 pg of Sr and < 200 pg Rb. An 87Sr/86Sr blank isotopic composition of 0.7088 was measured for a typical reagent load in the laboratory, and used to correct all measured 87Sr/86Sr ratios. The largest Sr blank corrections made are ~2%, for samples with the lowest Sr contents (<5 ppm Sr) and smallest sample weights (~3 mg); more typically blank corrections of < 0.2 % were made for Sr. For Rb, analyses were blank corrected assuming normal Rb isotopic composition and in all cases this correction was < 0.03 %.
Trioctahedral mica Rb/Sr ages are calculated applying the age equation including the initial 87Sr/86Sr ratio obtained from the regression of two points (trioctahedral mica and a low-Rb mineral) using Isoplot (Ludwig 2001). Uncertainties for Rb/Sr ages are calculated with the application of the error propagation formula to the age equation combining a ±1% 2σ uncertainty in measured 87Rb/86Sr in the mica, the measured 2σ uncertainty in 87Sr/86Sr in the mica, the variation in the initial 87Sr/86Sr ratio obtained from the regression using Isoplot and the errors in λ87Rb. All ages use λ87Rb = 1.3968 x 10-11 a-1 with errors: +0.0027 x 10-11 a-1 and -0.0018 x 10-11 a-1 both at 2σ (Rotenberg et al. 2012). The different errors in the λ87Rb produce a difference in the error propagation formula up to of 0.05 Ma (sample HF-08-10); in this work, however, the errors quoted in the Rb/Sr ages are calculated using the +2σ value in λ87Rb which is higher in absolute value than the -2σ.
DESCRIPTIONS OF THE 40Ar/39Ar STEP-HEATING SPECTRA
Vågje shear zone
Amphibole
	The age spectrum from the amphibole of sample HF-08-24b1 yields a general flat pattern with an integrated age of 727 ± 2 Ma (Fig. 6a). The age spectrum yields older ages in the low-temperature steps (< 4 % of 39Ar released) that monotonically descend from c. 1300 Ma to 740 Ma, and then remain in between 725–703 Ma for the remainder of the steps. The Cl/K and Ca/K values mimic the age spectrum in the low temperature steps with high values up to 0.07 and 34.30, respectively, monotonically decreasing to constant values of c. 0.010 and c. 8.4. 
	The age spectrum from the hastingsitic amphibole of sample HF-08-24a yields a flat profile with a plateau age of 416 ± 1 Ma (steps 2–9 comprising 99.8% of the 39Ar released, MSWD = 1.1) (Fig. 6b). The first step of the age spectrum yields an anomalously old age of c. 2360 Ma representing < 1 % of 39Ar released. The Cl/K and Ca/K values are constant and around 0.015 and 6.5, respectively, similar rim-to-core chemical values (0.06–0.08 and 6.5–6.1, respectively) were obtained.
Trioctahedral mica
	The age spectrum obtained for the relict igneous phlogopite of sample HF-08-25e (Fig. 6c) is characterized by anomalously high apparent ages in the first steps which decrease to a plateau with an age of 1885 ± 9 Ma (steps 12–17 comprising 56 % of the 39Ar released, MSWD = 3.3). Cl/K and Ca/K values of 0.02 and 0.04, respectively, are constant, and similar rim-to-core chemical analyses (0.013 and 0.002, respectively) were obtained. Phlogopite and orthopyroxene contain 100.68 and 0.99 ppm of Rb and 7.77 and 3.59 ppm of Sr, respectively. The Rb–Sr isotopic data for these minerals yields a 2-point line corresponding to an age of 411 ± 4 Ma and an IR of 0.7074 (Table 3).
	Late growth biotite from the retrogressed eclogite (HF-08-25a) has a disturbed age spectrum characterized by an undulating profile (Fig. 6d), yielding an integrated age of 3230 ± 14 Ma. The Cl/K and Ca/K values for this sample are very low (0.05 and 0.12, respectively), and the Cl/K ratio is relatively constant. The Ca/K spectrum mimics the age spectrum with maximum Ca/K values up to 0.20. Biotite and garnet for this rock contain 166.23 and 4.75 ppm of Rb and 25.96 and 172.91 ppm of Sr, respectively. The Rb–Sr isotopic data for these minerals yields a 2-point line corresponding to an age of 360 ± 4 Ma and an IR of 0.7054 (Table 3).
	Annites from samples HF-08-24b1 and HF-08-24a yield age spectra characterized by flat profiles with 100% of the 39Ar released. For the sample Hf-08-24b1, a plateau age of 1127 ± 4 Ma (steps 1–15, MSWD = 1.4) was obtained (Fig. 6e). Cl/K and Ca/K ratios yield constant values (< 0.001 and 0.02 respectively), similar rim-to-core electron microprobe values (0.001) were obtained. Sample HF-08-24a yields a plateau age of 472 ± 2 Ma (steps 1–14, MSWD = 0.6) (Fig. 6f). The Cl/K and Ca/K values are also constant (0.001 and 0.04 respectively), similar rim-to-core chemical values (0.01 and <0.01, respectively) were obtained. Annite and plagioclase from HF-08-24a contain 30.09 and 231.09 ppm of Rb and 7.85 and 2945.76 ppm of Sr, respectively. The Rb–Sr isotopic data for these minerals yields a 2-point line corresponding to an age of 363 ± 4 Ma and an IR of 0.7038 (Table 3).
Dioctahedral mica
	Muscovite from HF-08-24b2 yields a flat profile (Fig. 6g) with high apparent ages in the first 4.5% of the 39Ar released which monotonically decrease to a plateau with an age of 426 ± 3 Ma (steps 4–9 comprising 60 % of the 39Ar released, MSWD = 1.2). Very low Cl/K and Ca/K values were obtained with weighted mean values of 0.002 and 0.007 respectively.
K-feldspar
	The age spectrum of K-feldspar in sample HF-08-25c is characterized by the presence of a “saddle” in the low-temperature steps up to 7.5 % of the 39Ar released (steps 1–7) with a minimum apparent age at c. 279 Ma in the step 4, followed by four relatively large steps that range in age from 416 to 421 Ma (Fig. 6h). The Cl/K and Ca/K spectra do not mimic the age spectrum and have very low values. The Cl/K and Ca/K values increase over the saddle steps with 0.0037 and 0.06 respectively, then decreasing to constant values of < 0.01 and 0.01, respectively.
Myrland shear zone
Amphibole
	The age spectrum of the pargasitic-hastingsitic amphibole of sample HF-08-20b is disturbed (Fig. 7a), characterized by anomalously high apparent ages from 4000 Ma to 806 Ma, in the first steps (steps 1–4), which decrease to apparent ages ranging between 570-516 Ma in the remaining seven steps. The integrated age yields 571 ± 1 Ma. The Cl/K and Ca/K spectra are flat with constant values of 0.068 and 7.7. The Cl/K and the Ca/K values are similar to the electron microprobe values from rim to core (0.04 and 7.6–9.6, respectively). An isotope correlation plot yields an intercept age of 450 ± 38 Ma (MSWD = 1.7) with a 40Ar/36Ar intercept (5509 ± 1800) excluding the first three anomalously old steps (steps 1–3 represent only 1.1 % of the 39Ar released) (see supplementary material).
The age spectrum from the amphibole of sample HF-08-21 (Fig. 7b) yields a plateau age of 414 ± 5 Ma (steps 4–8, comprising 74.3 % of the 39Ar released, MSWD = 0.9), with slightly older ages in the last two steps (steps 9–10). Over the plateau steps, the Cl/K and Ca/K are constant with values of < 0.02 and 6.70 respectively, but are higher in the last two steps.
Trioctahedral mica
	The step-heating results of the biotite from sample HF-08-21 (Fig. 7c) yields a gentle saddle-shaped spectrum with an integrated age of 1593 ± 4 Ma. The Ca/K and the Cl/K profiles have average values of < 0.01 and 0.14 respectively.
	The age spectrum of phlogopite from sample HF-08-20b (Fig. 7d) is saddle-shaped, beginning with younger apparent ages in the low-temperature steps, then gradually undulating in age with an integrated age of 1460 ± 3 Ma. Both the Cl/K and the Ca/K ratios have low average values of < 0.01 and 0.11 respectively. The Cl/K ratio is consistent with rim-to-core chemical analyses in this phlogopite (0.009) but the Ca/K ratio is not (EMP data indicate Ca/K = 0.001). Phlogopite and epidote from this rock contain 91.42 and 48.34 ppm of Rb, and 5.30 and 2058.24 ppm of Sr, respectively. The Rb–Sr isotopic data for these minerals yields a 2-point line corresponding to an age of 182 ± 2 Ma and an IR of 0.7078 (Table 3).
	The age spectrum of the annite from sample HF-08-20c2 (Fig. 7e) yields a plateau age of 1029 ± 3 Ma (steps 1–17 comprising 100% of the 39Ar released, MSWD = 1.5), with Cl/K and Ca/K values (0.0125 and 0.043 respectively) that are consistent with the range of the rim-to-core chemical values (< 0.03 and < 0.01, respectively). Annite and epidote from the boudin contain 20.28 and 1.79 ppm of Rb, and 4.16 and 1783.69 ppm of Sr. The Rb–Sr isotopic data for these minerals yields a 2-point line corresponding to an age of 55.6 ± 0.6 Ma and an IR of 0.7091 (Table 3).
	In the case of the biotite of sample HF-08-20d (Fig. 7f), the age spectrum defines a plateau of 948 ± 3 Ma (steps 1 to 15, corresponding to 96.2 % of the 39Ar released, MSWD = 1.0). The Cl/K and Ca/K ratios are constant with low weighted mean values of 0.003 and 0.006 respectively.
Dioctahedral mica
	Muscovite from HF-08-20c2 (Fig. 7g) yields a flat profile with a plateau age of 390 ± 1 Ma (steps 3–13 comprising 87.6% of the 39Ar released, MSWD = 0.6). Low Cl/K and Ca/K values (averaging 0.00001 and 0.01 respectively) are generally consistent with the range of Cl/K and Ca/K values that were obtained from chemical rim-to-core analyses (0.011 and < 0.002, respectively).
K-feldspar
	The K-feldspar from sample HF-08-20d (Fig. 7h) yields an age spectrum characterized by an anomalously old age in the first step, followed by young ages in the first 15% of the 39Ar released that monotonically increase to a segment with a weighted mean age of 284.3 ± 3.5 (steps 11–16 comprising 49 % of the 39Ar released, MSWD = 27). The integrated age for this sample is 277.2 ± 0.4 Ma. The Cl/K and Ca/K ratios are very low.
Skagen shear zone
Amphibole
	The age spectrum of the sample HF-08-15e (Fig. 8a) monotonically decreases in apparent age, yielding an integrated age of 452 ± 1 Ma. The Cl/K and Ca/K spectra for this sample yield flat profiles with constant values of < 0.1 and 4.7 respectively, indicating the absence of fluid inclusions or other phases and consistent with very similar rim-to-core chemical values (< 0.1 and 5.0, respectively). An isotope correlation plot through all steps yields an intercept age of 424 ± 12 Ma (MSWD = 0.5) with 40Ar/36Ar intercept of 3254 ± 1100 (see supplementary material).
The age spectrum of sample HF-08-15c (Fig. 8b) is characterized by anomalously high apparent ages in the first three steps comprising 26% of the 39Ar released, which decrease monotonically to a flat segment in the higher-temperature steps that yields an weighted mean age of 414 ± 1 Ma (steps 7–11, corresponding to 36.7% of the 39Ar released, MSWD = 2.8); the integrated age is 453 ± 1 Ma. A strong correlation exists between the age spectrum and the Cl/K and Ca/K spectra. Low values of Cl/K and Ca/K (0.01 and 0.05–2.82) correspond to the older ages in the low-temperature steps of the age spectrum, while higher constant Cl/K and Ca/K values (0.02 and 4.95) correspond to the plateau-like segment. The rim-to-core electron microprobe analyses of Cl/K and Ca/K are similar to the ones obtained in the plateau-like segment (0.08 and 5.10, respectively).
Trioctahedral mica
	The annite age spectrum from sample HF-08-15c is characterized by a gentle bell shape (Fig. 8c), with young ages in the low-temperature and highest-temperature steps. The remainder of the steps define a plateau with an age of 597 ± 5 Ma (steps 3–9, representing 85% of the 39Ar released, MSWD = 1.6). The mean Cl/K and Ca/K values (<0.01 and 0.15, respectively) are similar to the electron microprobe values (rim-to-core values are <0.01). The annite and epidote of this amphibolite contain 20.28 and 1.79 ppm of Rb, and 4.16 and 1783.69 ppm of Sr, respectively. The Rb–Sr isotopic data for these minerals yields a 2-point line corresponding to an age of 319 ± 3 Ma and an IR of 0.7084 (Table 3).
Dioctahedral mica
The age spectrum from the muscovite of sample HF-08-16 (Fig. 8d) yields a plateau age of 319 ± 2 Ma (steps 6–15, representing 69.4 % of the 39Ar released, MSWD = 2.3). Over the plateau steps, the Cl/K and the Ca/K profiles are relatively flat (< 0.01 and 0.12 respectively). 
The age spectrum from the sericite of sample HF-08-15g (Fig. 8e) yields a plateau age of plateau age = 206 ± 15 Ma (steps 5–8, representing 66.3 % of the 39Ar released, MSWD = 0.2). The mean Cl/K and Ca/K values are also relatively constant over the same steps as the plateau.
K-feldspar
	The age spectrum for the K-feldspar of samples HF-08-16 is shown in Figure 8f. The disturbed age spectrum is characterized by young ages in the low-temperature steps that monotonically increase to a plateau-like segment in the higher-temperature steps that yields a weighted mean age of 191 ± 13 Ma (steps 6–11, representing 51 % of the 39Ar, MSWD = 3.8) and then decrease in the high-temperature steps; the integrated age is 184 ± 4 Ma. The Cl/K profile is similarly disturbed.
Hopen Pluton (Charnockite)
K-feldspar
	The age spectrum of sample C-99-22 yields a flat profile and a plateau age of 273 ± 7 Ma (steps 5–8, comprising 79.4% of the 39Ar released, MSWD = 1.1) (Fig. 9h). The Cl/K and the Ca/K values decrease to values of 0.02 and 0.03 corresponding to the steps of the plateau.
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