Nd Isotope Geochemistry of Igneous Rocks in the Glennie Domain and its Immediate Sub-Phanerozoic Extension: Evidence for

Interactions with the Sask Craton?

Tim C. Prokopiuk I and Kevin M Ansdell I

Prokopiuk. T.C. and Ansdell, K.M. (2000): Nd isotope geochemistry of igneous rocks in the Glennie Domain and its immediate Sub-Phanerozoic extension: Evidence for interactions with the Sask Craton?: in Summary of Investigations 2000, Volume 2, Saskatchewan Geological Survey. Sask. Energy Mines. Misc. Rep. 2000-4.2

Abstract The Nd isotopic composition of mafic and granitoid igneous rocks/ram the Glennie Domain, andfram drillcore immediately to the south of the Phanerozoic-Precambrian unconformity were used to provide: (I) constraints on the isotopic composition of the Paleoproterozoic mantle, (2) evidence for the initial interaction between the Archean Sask Craton and the juvenile rocks of the Trans-Hudwn Orogen, and (3) the present extent of the Sask Craton. The age of the mafic volcanic rocks from the southern Glennie Domain and the Sub-Phanerozoic are not known, but are assumed to be ca. 1880 to 1850 Ma. The ENi1 {1850 Ma) values range from +3.8 to+ 1.3, which suggests that these mafic magmas were likely derived from a similar heterogeneous mantle to that which yielded the ocean floor rocks of the Flin Flon Domain. The lower values may provide evidence for a small amount of interaction of this magma with older crustal materials. Three granitoids in the southern Glennie Domain have U-Pb ages of ca. 1832 Ma and are thus broadly coeval with the collision between the Sask Craton and the Flin Flan-Glennie complex, whereas the Wapawekka lake pluton is ca. 1850 Ma. The latter has an E,w (1850 Ma) value of + 3.2, whereas the former have ENi1 ( 1832 Ma) values of +O. 9 to + l . 7. The Wapawekka lake pluton was probably derived/ram a similar source as the mafic volcanic roch or by melting of relatively young arc crust, whereas the younger plutons may have crystallized from magmas that had undergone up to 20% contamination by Archean crustal material. The nature of this older crust is unknown, but may represent the Sask Craton itself. These granitic magmas may thus be recording the arrival of the Sask Craton in the Trans-Hudson Orogen. The granitoid rocks from the Sub-Phanerozoic have significantly lower ENi1 (1850 Ma) values ranging from -3.8 to -8.6, and thus have undergone significant interaction with older crust or are actually Archean in age. The lowest f.,~.i value obtained in this study is.from a ca. 1780 Ma pegmatite from the northern Glennie Domain. The ENi1 (1780 Ma) of-10.6 indicates that the pegmatitic melt was probably derived by melting of the northern buried extension of the Sask Craton, as imaged on LITHOPROBE seismic line S2h.

1. Introduction

The Trans-Hudson Orogen (THO) is a Paleoproterozoic zone of orogenesis extending from Greenland, through central Canada, and into the northern United States (Hoffman, 1988). The THO comprises a collage of accreted intraoceanic terranes (Reindeer Zone) and reworked continental margins (Lewry and Collerson, 1990), and formed in response to the collision of the Archean Hearne and Superior cratons (Bickford et al., 1990), and a third Archean craton, the Sask Craton, which drifted northwards between the Superior and Hearne cratons from about 1.83 to 1.80 Ga (Ansdell el al., 1995).

The Sask Craton outcrops in structural windows located in the Flin Flon- Glennie complex (Figure I ; Chiarenzelli e t al., 1998; Ashton et al., 1999), but extends into the subsurface as a crustal-scale anticlinorium which is separated from the bounding Superior and Hearne cratons by Paleoproterozoic crust. The geometry of this craton has been estimated from LITHOPROBE and COCORP seismic sections (Lucas et al. , 1993; Nelson et al., 1993; Lewry et al., 1994; Baird et al., 1996), whereas its extent has been estimated from Nd and Pb isotope analyses ofpost-collisional pegmatites in the exposed THO (Steinhart et al. , 1997; Ansdell and Stem, 1997), and Precambrian rocks intersected in drill holes through the Phanerozoic cover (Collerson et al., 1988). Together, these methods have shown that the Sask Craton extends over I 000 km under the Phanerozoic cover and tapers northwards towards the northern end of the Glennie Domain. Although geophysical anomalies have been used to extrapolate the Paleoproterozoic clements of the THO southwards (e.g. Green et al., 1985), geochronological and isotopic data suggest that the volume of juvenile Paleoproterozoic crust is probably insignificant below the Phanerozoic cover (Collerson et al. , 1988). The character of this southward change in age and isotopic composition of the Precambrian rocks is, however, unknown.

One of the problems is that the Nd isotopic composition of magmatic rocks in the Glennie Domain, other than post-collisional pegmatites (Bickford et al., 1992), are poorly known, and thus it is unclear whether the older igneous rocks may record

'Department uf Geological Sciences. University of Saskatchewan, 114 Science Place. Saskatoon, SK S7N 5E2.

Saskatche wan Geological Survey 79

Wathaman Ball!olilh

ROTTENSTONE DOMAIN

./LARONGE / ;' DOMAIN

b / : ! O I 'lg /

Nemeiben Zone

M.36

.M38

COVER • M28

0 50 -, ... I

Kilometres

56°30'

54°30'

; ; ; ,. / ., /

; ;

,l'(ISSEY}IEW DOMMN ,,,/

/ / ., ., ., ., ; / ,. ;

; ., ., / ., .,

., ., "fLON Flin Fk>n •

DOMAIN

dec ided to analyze magmatic rocks from drill holes closest to the Phanerozoic unconformity to provide the most reasonable bas is for the southward extrapolation of data from the exposed THO.

2. Sampling and Analytical Techniques

Samples (Figure I) were chosen from the rock collections at Saskatchewan Energy and Mines,

~ and consisted of either powders. u:! outcrop samples, or drillcore. The

absolute age o f the samples was either known, or assumed from well-understood geological re lationships. The only samp le located at a significant distance from the contact w ith the Phanerozoic rocks is 9811-3004, a ca. 1780 Ma post-coll isiona l pegmatite, wh ich was used to he lp del ineate the northern extent of the Sask Craton.

N d isoto pe analyses were performed at the Univers ity of Saskatchewan, and the results

Figure I - Simplified geological map of the Gle1111ie Domain, a11d surro1111di11g Paleoproterow ic terra11es of the Reindeer Zo11e of the Tra11s-Hudson Oroge11 ( after Ashton, 1999; Delaney, 1992). The Flin Flon-Gle11nie Complex comprises the Gle11nie and Flin Flon domains. The grey-shaded regions in the Glennie Domain are greenstone belts. The location of samples are indicated by tl,e collar of the ,!rill hole f or the Sub-Phanerowic samples, and the location of outcrops in the exposed shield. The complete sample numbers are shown in Table I.

reported in Table 1. Rock and drillcore samples were jaw-crushed and ground in a tungsten carbide sw ing mi ll. Powdered samples were completely spiked w ith the appropriate amount of a mixed 1' ''Sm-"r'Nd tracer so lu tion prior to digestion in HF-HN01 in

interaction with Archean crust. Thus, these rocks may have a significantly di fferent Nd isotopic composition from litho logically similar arc and ocean floor rocks in the Flin Flon Domain (Stern et al., I 995a, I 995b; Whalen et al , 1999). In addition, extrapolation of geophysical anomalies over long distances is difficult , and in fac t Green et al. ( 1985) indicate that the southward extension of the Glennie Domain is particularly inconclusive. Thus, it is difficult to relate the isotopic data obtained from drill ho les across the whole of southern Saskatchewan with specific regions within the exposed THO . In order to address some of these problems, it was decided to determ ine the Nd isotopic composition of pre- and post-colli sional igneous rocks in the Glennie Domain. The fonner included mafic volcanic rocks, which are assumed to provide an indication of the Nd isotopic composition o f the Paleo proterozoic mantle, The latter included ca, 1.83 Ga granitoid rocks. interpreted to have been intruded synchronous with the deve lopment of regiona l scale thrust faults related to the first interactions between the Reindeer Zone and the Sask Craton (Ansdell et al., 1995; Ashton et al. , 1999). It was a lso

80

screwtop Teflon containers. Sm and Nd were separated using

standard cation-exchange procedures. prior to loading on outgassed rhenium filaments with I 11PO, and 2.0N HC I. Isotopic analyses were performed in s tatic mode on a Finnigan MAT 261 mass spectrometer. Spike unmix ing, and mass fractionation corrections were perfonned offline, and used the following normalization ratios: 14~Ndl 44Nd-"- 0.72 l 9 and 14MSm/ 1~4Sm=0.49419. Analyses of standards during the course o f this project yielded the follow ing values: La Jolla Nd standard yielded a 143 Nd/ 144Nd value of 0.5 I 183 5 ±9; Ames Nd standard y ie lded an average '4 ' Nd/144 Nd value of0.512102 ±11 (n~3); and Ames

Sm standard 14"Smr 4Sm a value of 0.6075 1 ±3. The epsilon Nd (£-;d) values at the present or at the age of the rock were calculated using the fo llow ing reference values: 14'Nd/144Nd C HU R (prcsent)=0.5 12638 and 147Sm/ 144Nd CHU R (present)=0. 1966 (Goldste in et al. , 1984). The T DM values were calculated using the following re ference values: 14·'Ndf '4 '1Nd Depicted Mantle (present}=0 .5 I 3 16 and 14"Sm/ 144Nd Depleted Mantle (present)=0.2 141 (Goldstein et al .. 1984). Procedural blanks are about I 00 pg Nd and 30 pg Sm, but are insignificant for these samples.

Summary of Invest igations]{)()(). I· "o /rr111e 2

Table I - A11aly tical data.

To'.\1 Age E,o Sample UTM lJTM l .. ocation Rock Type Sm (ppm) Nd (ppm) 1~1Sml"uNd IH N

10

5 -"". : . ..-:" .:... : ·· . _, .--- -- - --- __ _

Depleted Mantle

. StJb..Ph¥*'ozoic

M11

.. M28A

M2 BE

+ M368 '1J z

0 ~ ~ --- · ~

t-,---,-.--,· _-_---:'-----------~...,.:..;;__ _ _..., _____________ _, SouthemGlennit Domilin I

c 0 (/) a. w -s I

I I

-10

-15

1600

.... •

1800 2000 2200

Archean Crust

2400 2600 2800

-.· ss22-11 I • eg22. 121

I 8922-250

+ 8822-375

• "822-377

8822-378

I l 8922-19

j Northern Glennie Domain • 9811-300<

3000 3200

Age (Ma) Figure 2 - Epsilon Nd-age plot showing i:N, value at assumed or known age of rock, and extrapolation towards Depleted Mantle. The field for Archean crust is after Collerson et al. ( 1988) and Ansdell and Bleeker (199 7), and Depleted Mantle is after Goldstein et al. (1984).

Sub-Phanerozoic

M28A and M28E are samples of amphibo lite grade mafic volcanic rocks from a drill ho le located to the south of the G lennie Domain. They have E,._d values at 1850 Ma of +3.8 and+ 1.3, respectively. The best interpretation for M28A is that the mafic magma was derived from a similar source as the mafic volcanic rocks in the southern Glennie Domain, and is probably Paleoproterozoic in age. The ENd value of + 1.3 obtained from M28E is similar to the lower values obtained from arc rocks in the Flin Flon Domain (Stem et al. , 1995b), and may provide evidence for the interaction of this magma with older crustal materials. However, this material may have been Paleoproterozoic sediment which contained minor amounts of recycled Archean or earlier Proterozoic elastic detritus.

Overall, the E:-id values of the mafic volcan ic rocks are similar to other juvenile Paleoproterozoic mafic volcanic rocks in the THO. The mafic rocks from the Sub-Phanerozoic drillcore do not provide evidence for large-scale interaction with o lder crust , a lthough they probably fonned in an oceanic environment prior to the arrival of the Sask Craton.

b) Granitoid Rocks

Southern G lennie Domain

Four granitoid rocks that intrude the supracrustal rocks of the southern Glennie Domain were analyzed. Three of these y ie lded simi lar U-Pb zircon ages of ca. 1832 Ma (Table I; McN icoll et al., 1992). These granitoids were em placed broadly synchronous with the initiation of southwest-directed thrusting, which

82

was related to the collision between the Sask Craton and the Flin Flon-Glennie complex (Ansdell et al .. 1995; Ashton et al. , 1999). Thus. these rocks may record some interact ion with the newly arr ived Sask Craton. The fourth, the Wapawekka Lake granodiori te , formed during the earl ie r phase of g ranito id magmatism , and is thus assumed to be 1850 Ma.

The ca. 1832 Ma pluton ic rocks have very sim ilar Nd isotopic compositions at time of formation ( E'4d values between +0.9 and + 1.7 ; Table I). In contrast, the Wapawekka Lake granodiorite, w hich is assumed to be older, has an e~d value of +3.2 at 1850 Ma. The latter value lies within the range exhibited by the middle successor arc granito ids in the Flin Flon Domain, whereas the younger granitoids have sign ificant ly lower E:-,J values than rocks of the same age in the Flin Flo n Domain (Whalen et al., 1999). However, these va lues arc sim ilar to those exhibi ted by older gran itoid rocks ( 1860 to 1880 Ma) in the Flin Flon Domain, which are thought to have been generated by mel ting of mant le wedge or juveni le arc crust w ith subsequent small amounts of contam ination by ass imi lation o f older crust.

The best in terpretation of the data from the southern G lennie Domain is that the Wapawekka Lake granodioritic magma was derived from a sim ilar source as the mafic volcanic rocks, or by mel ting of relat ively young mantle-derived crust. The 1832 Ma plutons have cons istent calculated T0 M ages, wh ich suggests that these magmas could have fonned by part ial me lt ing o f 2. 14 Ga crust (Figure 2). There is no known crust of this age within the THO, and so these magmas could have formed by either: ( I) me lt ing of slight ly o lder basaltic crust. similar in isotopic composition to sample M28E, o r (2) contamination of + 3 .0 magmas with

Summar ,: cl Investigations ]()()(), 1 ·0 ! 11me l

older Archean crust with an £Nd value of about -10.0 or less. A simple two-component mixing calculation using the following end-member components (granitic magma Nd=30 ppm and ENd=+ 3 .O; Archean crust Nd=30 ppm and ENd=-1 0.0) indicates that the EM value of the 1832 Ma plutons could result from 20% contamination by Archean crust. If the Archean crust has a lower £Nd va lue or higher concentration of Nd then the weight fraction of older c rust required would decrease accordingly. In addition, it is not known whether this Archean component would consist of Archean crysta lline rocks, or Archean crust that had been recycled and deposited into Paleoproterozoic sedimentary basins and subsequently incorporated into the 1832 Ma magmas.

Northern Glennie Domain

An undeformed ca. 1780 Ma granitic pegmatite which intrudes my lonitized granitoid g neisses a long the northern boundary of the G lennie Domain (Harper, 1998; Harper et al., 2000) was analyzed to determine whether its Nd isotopic compos ition suggested interaction with significantly older crust. The £Nd value at the assumed age of intrusion is - I 0.6 (Table 1 ), which suggests extensive contamination by or direct derivation from Archean crust ( Figure 2). This Archean crust is probably the northern extension of the Sask Craton, which is imaged on LITHOPROBE seismic line S2b ( Hajnal et al. , 1996), and indicates that the Sask Craton had underthrust the Paleoproterozoic rocks of the THO at least as far north as this point by ca. 1780 Ma.

Sub-Phanerozoic

Three granitic samples were taken from drill holes that inte rsected the basement below the Phanerozoic sedimentary cover. The ages of these samples are not known, but are presumed to be Paleoproterozoic, because they are taken from drill holes that are as close as possible to the exposed THO. Drill holes M36 and M38 are situated with in the extension o f the La Ronge Domain, whereas MI I lies immediately to the south of the G lennie Domain in the Deschambault Lake area.

The samples from M36 and M38 have Ei-;d values of -4 .6 and -8.6 at an assumed age of 1850 Ma, and T DM ages of 2.55 and 2. 75 Ga, respectively (Table I , Figure 2 ). These magmas have thus interacted significantly with older crust, or are actually Archean in age. However, no geochronological data is available for these rocks. Simi lar E:-Jd values have been obtained from the Wathaman Batholith and the Tonalite-Migmatite Complex on Reindeer Lake (Kyser and Stauffer, 1992). These authors suggested that low £~d values in the gneisses of the Tonalite-Migmatite Complex resulted from metamorphism of supracrusta ls containing detritus shed from the Hearne craton. The Wathaman Ratholith formed fro m magmas that incorporated significant quantities of this older supracrusta l material. A better understanding of the geological, age, and petrogenet ic relationships in the

Saskatchewan (ieoloRical S11rvey

southern La Ronge Domain is necessary before the Nd isotopic compositions of the granitoids in this study can be fully interpreted.

Sample M 11 is a coarse-grained granito id with a E:,.,d value of -3.8 at an assumed age of 1850 Ma. This value is significantly lower than the values obtained from the ca. 1832 Ma granitoids in the Glennie Domain. Therefore, even though the crystallization age of th is rock is not known, the init ial magma interacted with a sub,stantial amount of older, possib ly Archean, crust prior to crystall ization.

4. Summary

I) The Nd isotopic composition of mafic volcanic rocks from the southern Glennie Domain and two samples from the Sub-Phanerozoic indicate derivation from a sim ilar mant le to that from which the Flin Flon arc and ocean floor rocks were generated.

2) The ca. 1850 Ma Wapawekka Lake granodiorite has an e'ld value of + 3.2, which is similar to the successor arc p lutons of the Flin Flon Domain, and is thus probab ly derived by remelting of juveni le arc crust.

3) In contrast, the ca. 1832 Ma granitoids have lower e]';d values, which suggest up to approximately 20% contamination by older crustal material. The nature of this contaminant is unknown , but may be Paleoproterozoic sedimentary rocks containing Archean detritus, or actual Archean crust. If it is the latter, then these granito ids may be samp ling a small component of the Sask Craton, which thus provides further constraints on the arrival of this craton in the THO.

4) The age of the granitoids from the Sub-Phanerozoic drillcore are unknown, although all three samples have negative i;"'d values. These data suggest significant interaction with Archean crustal mate ria l, although the lack of age control makes inte,pretation diffi cult.

5) The ca. 1780 Ma pegmatite from the northern Glennie Domain has an Ei-;d value of -10.6, which suggests that the pegmatitic melt was probab ly generated from Archean crust. The location of th is sample, and the interpretation of the LITHOPROBE seismic signature lends support to the theory that this Archean crust is the Sask Craton. This sample thus marks the northernmost limit of the Sask Craton.

More detailed and integrated geochronolog ical, geochemical, and isotopic analys is is required to fu lly understand the development of the southern G lennie Domain and the southern extensions of the La Ronge Domain. in order to be able to extrapolate to the Su-b-Phanerozo ic basement. These new data, however, do suggest that the ca. 1832 Ma granitoids may be providing evidence for the arr iva l of the Sask Craton, which then undcrthrust as far north as the northern G lennie Domain.

83

5. Acknowledgments This study was initiated while Tim Prokopiuk was a recipient of an NSERC Undergraduate Research Scholarship. The supplement to the scholarship, and sampling and analytical costs were borne by an NSERC Research Grant lo Kevin Ansdell . Samples were collected in Regina with the assistance and advice of Gary Delaney, Ken Ashton, Charlie Harper, and Lynn Kelley. Technical support in the Isotope Laboratory at the University of Saskatchewan was provided by Diane Fox, Chris Holmden, and Kerrie Fanion. Tim Prokopiuk appreciated the midsummer break from lab work provided by Don Wright and Ralf Maxeiner. Bill Slimmon and Ken Ashton are thanked for a digital copy of a Glennie Domain map on which Figure I is based, and Gary Delaney is thanked for his comments on the manuscript. LITHOPROBE Publication # I I 03 .

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the Superior Craton : Neodymium isotope constraints on the evolution of the Thompson Nickel Belt, Manitoba; Geol. Assoc. Can./Miner. Assoc. Can., Abst. Vol., v22, pA-4-5.

Ansdell , K.M., Lucas, S.B., Connors, K., and Stern, R.A. (1 995): Kisseynew melasedimentary gneiss belt, Trans-Hudson Orogen (Canada): Back-arc origin and coll isional inversion; Geo!., v23, p I 039-1043.

Ansdell, K.M. and Stern, R.A. ( 1997): The Scimitar Complex: Initial SHRIMP U-Pb and Nd isotope data from granitoid rocks; in Summary of Investigat ions 1997, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 97-4, pl 45-149.

Ashton, K.E. ( 1999): A proposed lithotectonic domainal reclassification of the southeastern Reindeer Zone in Saskatchewan; in Summary of Investigations 1999, Volume 1, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 99-4.1, p92-100.

Ashton, K.E., Heaman, L.M., Lewry, J.F., Harllaub, R.P., and Shi, R. ( 1999): Age and origin of the Jan Lake Complex: A glimpse of the buried Archean craton of the Trans-Hudson Orogen; Can. J. Earth Sci., v36, p 185-208.

Baird, D., Nelson, K., Knapp, J. , Walters, J., and Brown, L. ( 1996): Crustal structure and evolution of the Trans-Hudson Orogen: Results from se ismic reflection profiling; Tectonics, v 15, p4 I 6-426.

Barov ich, K.M. and Patchett, P.J . ( 199 1 ): Behavior of isotopic systematics during defonn ation and metamorphism: A Hf, Nd and Sr isotopic study of mylonitized granite; Contrib. Mineral. Petrol. , v l09, p386-393.

8-1

Bickford, M.E., Collerson, K.D., Lewry, J.F., and Orrell, S.E. ( 1992): Pegmatites and leucogranites as probes of crust beneath allochthonous orogenic rocks in the Glennie and La Ronge domains; in Summary of Investigations 1992, Saskatchewan Geological Survey, Sask. Energy Mines, Mis

Hoffman, P.F. ( 1988): United Plates of America, the birth of a craton: Early Proterozoic assembly and growth of Laurentia; Ann. Rev . Earth Planet. Sci., v 16, p543-603.

Kyser, T.K. and Stauffer, M. ( 1992): Petrogenesis of the Wathaman Batholith ; in LITHOPROBE Trans-I ludson Orogen Transect Meeting, Rep. 26, p I 26-128.

Lewry, J.F. and Collerson, K.E. ( 1990): The Trans-Hudson Orogen: Extent, subdivision, and problems; in~Lewry, J.F. and Stauffer, M.R. (eds.), The Early Proterozoic Trans-Hudson Orogen of North America, Geo!. Assoc. Can., Spec. Pap. No. 37, pl-14.

Lewry, J. , Hajnal , Z., Green, A., Lucas, S .. White, 0. , Stauffer, M., Ashton, K., Weber. W., and Clowes. R . ( 1994): Structure of a Paleoproterozoic continent-continent collision zone: A LITHOPROBE seismic reflection profile across the Trans-Hudson Orogen. Canada; Tectonophysics, v232, p 143-160.

Lucas, S.B., G reen, A. , Hajnal , Z ., White. 0., Lewry, J., Ashton, K .. Weber, W., and C lowes, R. ( 1993): Deep seismic profile across a Proterozoic coll is ion zone: Surprises at depth; Nature, v363, p339-342.

McCulloch, M.T. and Black. L.P. (1984): Sm-Nd isotopic systematics of Enderby Land granu lites and ev idence for the redistribution of Sm and Nd dur ing metamorphism; Earth Planet. Sci. Lett. , v7 L p46-58.

McNicoll, Y.J., Delaney, G.D. , Parrish, R.R. , and Heaman. L.M. (1992): U-Pb age determinations from the Gle nnie Lake Domain. Trans-Hudson Orogen, Saskatchewan; in Radiogenic Age and Isotopic Studies: Report 6 , Geo!. Surv. Can., Pap. 92-2, p57-72.

Nelson, K., Ba ird, D. , Walters , J., Hauck, M., Brown, L., Oliver, J.. Ahem. J., Hajna l, Z. , Jones, A., and Sloss, L. ( 1993): Trans-Hudson Orogen and Williston Bas in in Montana a nd North Dakota: New COCO RP deep profiling results: Geo!., v2 I , p447-450.

Steinhart. W.E. , Bickford, M.E. , Lewry, J.F., and Mock, T.D. ( 1997): Common Pb and Sm-Nd study of the Glennie, Hanson Lake , and La Ronge domains, and the Hearne province, Trans-Hudson Orogen: Implication s for tectonic evolution; Geo!. Assoc. Can./Mineral. Assoc. Can., Abst. Vol. , v22, pA-142.

Stern, R.A., Syme, E.C., and Lucas, J.B. ( 1995a): Geochemistry of 1.9 Ga MORB- and 018-like basalts from the Amisk collage, Flin Flon be lt, Canada: Evidence for an intra-oceanic o rigin, Geochim . Cosmochim. Acta, v59, p3 I 3 l-3154.

Saskatchewan GeuloRica/ Survey

Stem, R.A., Syrne, E.C., Bailes, A.H., and Lucas, S.B. (I 995b): Paleoproterozoic (1.90-1.86 Ga) arc volcanism in the Flin Flon belt, Trans-Hudson Orogen, Canada; Contrib. Mineral. Petrol., vi 19, pll7-141.

Whalen, J.B .. Syme, E.C., and Stem, R.A. (1999): Geochemical and Nd isotopic evolution of Paleoproterozoic arc-type granitoid magmatism in the Flin Flon belt, Trans-Hudson Orogen, Canada; Can. J. Earth Sci., v36, p227-250.

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