Precambrian Research 148 (2006) 1–18

Polycyclic evolution of the Late Neoproterozoic basement in theHermitage Flexure region (southwest Newfoundland Appalachians):

New evidence from the Cinq-Cerf gneiss

P. Valverde-Vaquero a,∗, G.R. Dunning b, S.J. O’Brien c

a Instituto Geologico y Minero de Espana, La Calera 1, Tres Cantos, Madrid 28760, Spainb Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada A1B 3X5

c Geological Survey of Newfoundland and Labrador, P.O. Box 8700, St. John’s, Newfoundland, Canada A1B 3X5

Received 14 July 2005; received in revised form 1 March 2006; accepted 7 March 2006

Abstract

The Cinq-Cerf gneiss represents one of the oldest tectonic elements yet documented within the “Avalonian” basement complexof the Hermitage Flexure region of the Newfoundland Appalachians. This gneiss is a composite unit that includes both supra-crustaland granitic gneisses, the latter having an igneous crystallization age of 675 + 12/−11 Ma. The timing of the gneiss-forming event(D1 polyphase deformation) is constrained by the protolith age of the orthogneiss and the 584 + 7/−6 Ma crystallization age ofgranodiorite intrusive into gneiss. The emplacement of the granodiorite is coeval with the previously dated 585 Ma eruption of felsictuff within nearby low-grade stratified elements of the pre-Silurian basement, north of the Grand Bruit Fault Zone (GBFZ), adding

support to models of a Late Neoproterozoic basement-cover relationship between the gneiss and the low-grade volcano-sedimentarysequence. Younger Neoproterozoic magmatism in the gneissic basement is recorded by emplacement of 557 + 14/−5 Ma gabbroand the intrusion of 547 + 2/−7 Ma diorite dykes. The latter have a recrystallized tectonic fabric that hosts 448 + 9/−3 Ma titanite.Peak Appalachian-cycle overprinting of the Cinq-Cerf gneiss occurred in mid- to late Silurian time, and commenced with high-temperature deformation (D2) of the gneiss, associated with synkinematic intrusion of Western Head granite at 431.5 ± 1 Ma. Maficdyke swarms that intrude the gneiss and the granite contain 420 ± 3 Ma titanite. This age reflects new growth during Silurianretrogression and mylonitization of the mafic dykes. The D3 mylonitization is widespread and linked to thrusting of the Cinq-Cerfgneiss along the GBFZ during the 420–418 Ma closure of the northerly adjacent Silurian volcano-sedimentary cover basin.

New data bearing on the Late Neoproterozoic record of the basement block of the western Hermitage Flexure further demonstratessimilarities in magmatic, stratigraphic and metallogenic record documented in Avalonian rocks of east Newfoundland’s Connaigre,Burin and Avalon peninsulas, pointing to a Neoproterozoic linkage with the rocks in these areas. The early to mid-Paleozoic historyof the Hermitage Flexure basement indicates that, during that time, the basement block evolved as a terrane separate from the AvalonZone (sensu stricto).© 2006 Elsevier B.V. All rights reserved.

Keywords: Neoproterozoic; Avalonia; U–Pb geochronology; Newfoundland

∗ Corresponding author. Tel.: +34 91 8032200; fax: +34 91 7287202.E-mail address: p.valverde@igme.es (P. Valverde-Vaquero).

1. Introduction

The integration of well-defined field and textural rela-tionships with reliable geochronology is key to unrav-elling the evolution of poly deformed terranes in theinternal parts of modern and ancient orogens. The Late

0301-9268/$ – see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.precamres.2006.03.001

2 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

Fig. 1. (A) Location of the Cinq-Cerf gneiss and “Avalonian” basement inliers of the Central Mobile Belt in the Newfoundland Appalachians. (B)Simplified geological map of the Cinq-Cerf Bay area in the western end of the Hermitage Flexure (modified from O’Brien et al., 1991). U–Pb agesfrom Dunning and O’Brien (1989), O’Brien et al. (1991) and Dube et al. (1995).

Neoproterozoic–Early Ordovician basement complex ofthe Hermitage Flexure in Central Mobile Belt of theNewfoundland Appalachians (Fig. 1A; e.g. O’Brien etal., 1991, 1996) is one such terrane, and the focusof investigations reported upon below. This basementcontains low-grade volcano-sedimentary rocks, plutonicsuites and gneissic rocks of Late Neoproterozoic age andinferred Avalonian affinity (e.g. Dunning and O’Brien,1989). These have been variously overprinted by Ordovi-cian and Siluro-Devonian events characteristic of theAppalachian-cycle tectonism affecting younger Iapetansuccessions of the Central Mobile Belt (e.g. Williams etal., 1988; Dunning et al., 1990; Williams, 1995).

This paper presents new data bearing on the natureand timing of the tectonothermal events, from the Pro-terozoic to the Devonian, affecting the oldest componentof the western part of that basement complex—theCinq-Cerf gneiss. Data presented below show older,dated fabrics and igneous textures in rocks affectedby multiple generations of well-documented and datedthermal and structural overprints in the same and adjoin-ing areas. These new data document Ordovician andSilurian, Appalachian-cycle overprints of the basementcomplex, and see through these events to: (1) corrob-orate the preservation of Late Neoproterozoic intrusiveand deformational events in the Appalachian Central

Mobile Belt, (2) reinforce the notion of a Neoprotero-zoic basement-cover relationship in this region, and (3)demonstrate strong links with other gneiss complexesof the Hermitage Flexure, and with major magmaticevents recorded in outboard Avalonian terranes.

1.1. Geological setting

The southern and eastern parts of the island ofNewfoundland are cored by Late Neoproterozoic plu-tonic and volcano-sedimentary rocks that, prior to theirinvolvement in early to mid-Paleozoic Appalachian-cycle orogenesis, were once part of a major magmaticarc that lay in the periphery of the ancient continent ofGondwana (Nance et al., 2002). These Neoproterozoicrocks, which form part of the eastern margin of theearly Paleozoic Iapetus Ocean (e.g. Williams, 1995),are commonly denoted by the term “Avalonian” (e.g.O’Brien et al., 1996), and are most completely preservedin Avalon Zone of the Newfoundland Appalachians,where they are capped by a Cambrian to early Ordovi-cian shale-rich cover (Williams, 1979; O’Brien et al.,1996; Fig. 1A). They form the core of the largestof the outboard terranes of the Appalachian Orogen,and record several major magmatic pulses, includingvolcanic arc forming events at 760, 730, 680, 620 and

P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18 3

580 Ma and a major rifting event between ca. 560 and540 Ma (O’Brien et al., 1996, 2001). Late Neoprotero-zoic rocks with a similar “Avalonian” Neoproterozoictectono-magmatic signature are preserved farther westin the Appalachian hinterland marked by the CentralMobile Belt (Fig. 1A). These rocks however have acontrasting Cambro-Ordovician tectonic history linkedto the Paleozoic events that shaped the peri-Gondwananedge of the Iapetus Ocean, which is largely unrecordedin the type Avalon Zone (O’Brien et al., 1996).

Within the Appalachian Central Mobile Belt, Aval-onian rocks crop out in two principal areas. In thefirst, Late Neoproterozoic (ca. 565 Ma) plutons and theircountry rocks occur with the Victoria Lake Supergroupof the Exploits Subzone (Dunnage Zone), in the poorlyexposed interior of central Newfoundland (Evans et al.,1990; Rogers and van Staal, 2002; Fig. 1A), wherethey represent either tectonic windows or basement toCambrian volcanic arcs of Iapetus. The second area isin southern Newfoundland, in the Late Neoproterozoicbasement block of the orogen-scale orocline defined bythe Hermitage Flexure (Dunning and O’Brien, 1989;O’Brien et al., 1991, 1993). There, Late Neoproterozoicrocks and Ordovician intrusions form basement to anunconformably overlying Silurian volcano-sedimentarysequence (429–422 Ma La Poile Group) and are sepa-rated by faults from Ordovician rocks of the ExploitsSubzone to the north (Bay du Nord Group; Fig. 1B).

In the Hermitage Flexure region, Late NeoproterozoicAvalonian rocks have been identified in three princi-pR1pItraaaNbbt

1H

t5t

the 576–562 Ma intrusions of the Roti intrusive suite(Fig. 1; Cooper, 1954; Chorlton, 1978, 1980, 1984;O’Brien, 1987, 1988, 1990; O’Brien et al., 1991; Dubeet al., 1995). Conglomerate from the base of the Whit-tle Hill sandstone-Third Pond tuff succession includesclasts of amphibolitic gneiss, suggesting that the Cinq-Cerf gneiss pre-dates the low-grade rocks and, as such,is the oldest element of the basement. The contact ofthe Cinq-Cerf gneiss with the other Late Neoproterozoicrocks is a fault zone with a prolonged history of LateNeoproterozoic to mid-Paleozoic movement, the GrandBruit fault zone (O’Brien et al., 1993). Enclaves of gneissin the 568 Ma granite of the neighboring Roti intrusivesuite provide evidence for Late Precambrian stitchingof the Cinq-Cerf gneiss with the low-grade volcano-sedimentary sequence (cf. Dunning and O’Brien,1989).

The low-grade Late Neoproterozoic volcano-sedi-mentary sequence is intruded by the Roti intrusive suiteand a set of 576–565 Ma intrusions that include felsicporphyry, gabbro and intermediate dykes and sills; italso hosts the high-sulfidation epithermal gold depositat Hope Brook, which formed between 578 and 574 Ma(Dube et al., 1995). The first set of large-scale regionalfolds in the Neoproterozoic volcano-sedimentarysequence is cross-cut by 499 + 4/−3 Ma and 495 ± 2 Maplutons (Dunning and O’Brien, 1989; O’Brien et al.,1991), indicating that folding took place before the LateCambrian.

The main tectonothermal overprint of the basement

al localities: Cinq-Cerf Bay, Grandys Brook, and Greyiver (Dunning and O’Brien, 1989; O’Brien et al., 1991,993). Correlative rocks of this basement are widely dis-ersed as mega-enclaves in the Siluro-Devonian Burgeontrusive Suite, which occupies approximately 70% ofhe basement block (Fig. 1). The Late Neoproterozoicocks lie unconformably beneath, and in tectonic contactbove, dated Silurian (429–422 Ma) subaerial volcanicnd sedimentary rocks of the La Poile Group (O’Brien etl., 1991). The subject of this investigation are the Lateeoproterozoic and adjoining rocks of the sub-Silurianasement; mapping focused on the coastal sectionetween Grand Bruit and Cinq-Cerf Bay (Fig. 1), wherehe oldest elements of the basement are best exposed.

.2. Pre-Silurian basement in the westernermitage Flexure region

In the western Hermitage Flexure, the Late Pro-erozoic basement contains the Cinq-Cerf gneiss, the85–582 Ma low-grade volcano-sedimentary rocks ofhe Whittle Hill sandstone and the Third Pond tuff, and

block occurred during the Siluro-Devonian (O’Brienet al., 1991). These events include emplacement ofthe Western Head granite (429 ± 2 Ma, 430 ± 2 Ma;O’Brien et al., 1991) and the Otter Point granite(419 ± 2 Ma; Fig. 1B) into the Cinq-Cerf gneiss.Siluro-Devonian movement along the Grand Bruit FaultZone has thrust the Cinq-Cerf gneiss and the WesternHead granite northward over the Late NeoproterozoicWhittle Hill sandstone and Roti intrusive suite, andover the Cambrian-aged Wild Cove granite, during theclosure of the Silurian La Poile cover basin to the north(O’Brien et al., 1991). The post-kinematic, DevonianChetwynd granite (390 ± 2 Ma) cross-cuts the GrandBruit Fault Zone, placing a younger limit on thrustmotion along that structure (O’Brien et al., 1991).

2. New mapping of pre-Silurian units

2.1. Cinq-Cerf gneiss

The Cinq-Cerf gneiss (cf. O’Brien, 1988;Figs. 2 and 3) is a composite unit of supra-crustal

4 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

Fig. 2. Geological map of the Cinq-Cerf gneiss and adyancent rocks in the Three Islands and the coast section between Sandbank Point and EastDiver Head. The stereonets correspond to the structural measurements along the coastal section.

and intrusive rocks having a composite gneissic fabric,which is cut by the Silurian Western Head granite. Thisgneissic fabric does not occur in the pre-Silurian plu-tonic bodies that intrude the gneiss, with the exceptionof some pre-Silurian granitoid dykes at Three Islands

(Fig. 2). The gneiss consists of amphibole-rich andquartzo-feldspathic supra crustal rocks with gabbroicpods, deformed mafic dykes and granitic orthogneiss.Locally, the gneiss is an injection migmatite formedfrom the intrusion of pre-Silurian granitoids and

Fig. 3. Geological map of the Cinq-Cerf gneiss in the type locality of Cinq-Cerf Bay.

P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18 5

the Western Head granite. Although Cooper (1954)described garnet from these rocks, subsequent studies(Chorlton, 1980, 1984; O’Brien, 1988; this study) havefailed to corroborate this observation. Conditions ofmetamorphism are uncertain, but mineral paragenesiswith hornblende, actinolite, and epidote in the amphi-bolitic members of the gneiss suggest formation underamphibolite to lower amphibolite facies conditions.

2.1.1. Amphibole-rich banded gneissAmphibolitic banded gneiss is characteristic of the

Cinq-Cerf Bay section (Fig. 3), and also occurs inthe Sandbank Point section near East Diver Head(Fig. 2) Alternating layers of green amphibole (horn-blende and actinolite), grey quartz, plagioclase (albite),and local epidote-rich bands define a compositionalbanding. Locally the gneiss contains 0.5–1 cm longporphyroblasts of green clinoamphibole (actinolite?)Near East Diver Head the gneissic banding warpsaround isolated, metric scale, coarse-grained gabbroicpods.

2.1.2. Quartz-feldspathic gneiss and schistPsammite and schist occur in the area between Sand-

bank Point and East Diver Head (Fig. 2). These arefine-grained rocks (∅ ≈0.2–0.6 mm) having a quartzo-feldspathic matrix with phyllosilicate-rich layers ofbiotite, chlorite and white mica. Lithologically, theschist includes both psammite and pelitic-psammite, andlocally contains 2 mm long tourmaline porphyroblasts.These psammites are the “melanosome” of the injec-tion migmatites produced after formation of the gneissby the intrusion of aplitic and granitic veins. Note thatthese psammitic gneisses (and not the orthogneisses)were sampled by Kerr et al. (1995) as a part of a regionalNd isotopic study of Newfoundland. The sample yieldedan ε

(600 Ma)Nd value of −2.4.

2.1.3. Orthogneiss (U–Pb sample)Near East Diver Head, the gneiss contains a mylonitic

granitic orthogneiss with associated mafic dykes (amphi-bolite) cross cut by younger granite and mafic dykes(Fig. 4). The gneissosity in the country rock and the

F pracrus9 94PV1( liationhf

ig. 4. Cinq-Cerf gneiss, map of the field relationships between the su4PV12) and the Silurian intrusions. (A) Granite dyke (U–Pb sampleB) Intrusive contact, the granite dyke is overprinted by a mylonitic fo

osted by the granitic orthogneiss. (D) Dyke of granitic orthogneiss in psammoliation.

tal quartzo-feldspathic gneiss, the granitic orthogneiss (U–Pb sample1) cross-cutting the Cinq-cerf gneiss, including granitic orthogneiss.(S3) and cross-cuts the gneissosity (S1). (C) Pre-Silurian mafic dykes

itic gneiss cross-cut by a granite dyke overprinted by the S3 mylonitic

6 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

Fig. 5. Pre-Silurian granodiorite (U–Pb sample 94PV6). (A) Sketch of the field relationships of the granodiorite with surrounding rocks. (B) Contactof the granodiorite with the country rock paragneiss (Cinq-Cerf gneiss). (C) Aplitic dyke cross-cutting the contact between the granodiorite andthe paragneiss, this aplitic dyke joins together with the aplite veins that give the migmatic character to the paragneiss. (D) Microtexture of thepre-Silurian granodiorite showing primary igneous zoning of plagioclase and grain reduction in the intergranular spaces.

orthogneiss are subparallel, but locally the intrusive rela-tionship between the granite orthogneiss and the countryrock is still preserved (Fig. 4). Pre-Silurian mafic dykesintrude the orthogneiss and the psammitic gneiss. Thesedykes are subparallel to the gneissic banding, and locallycontain a tectonic fabric parallel to the gneissosity in theenclosing orthogneiss (Fig. 4).

2.2. Granodiorite

The section between Sandbank Point and East DiverHead contains a 100 m2 outcrop of weakly deformedhornblende-bearing granodiorite (Fig. 2). The gran-odiorite (dated as part of this study) is cut by anaplitic vein, which merges with the deformed apliticveins in the country rock gneiss (Fig. 5). The strainin the country rock increases towards the contactwith the granodiorite (Fig. 5A), deflecting the folia-tion of the country rock. The country rock is an injec-tion migmatite formed by tourmaline-bearing quartzo-feldspathic schist, which was deformed prior to intru-sion of the aplitic veins. The strain associated withthe deformation after the injection of the aplitic veins

has masked any trace of a cross-cutting relationshipbetween the granodiorite and the earlier fabric in theschist. The granodiorite has an equigranular igneous tex-ture defined by plagioclase with igneous zoning, horn-blende and K-feldspar with primary simple twins andquartz. This igneous texture is overprinted by a weaknon-penetrative fabric associated with local grain-sizereduction (>0.2 mm) along grain boundaries, dynamicalrecrystallization of quartz, and new growth of epidote,white mica, chlorite, green clinoamphibole and opaques(Fig. 5C).

2.2.1. Unnamed folded granitoidThe aplitic veins in the migmatitic gneiss, that is the

country rock to the granodiorite describe above, coalescewith folded granitoid dykes (Fig. 5). These granitoiddykes have a thickness of 1–3 m and contain centimeter-scale gabbroic xenoliths. The aplitic veins and granitoiddykes are coeval, and post-date the intrusion of the gra-nodiorite and the formation an earlier foliation in thecountry rock paragneiss (Fig. 5). The Western Headgranite apparently intrudes these granitoids, but the con-tact has been reworked and the pre-Silurian age of the

P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18 7

Fig. 6. Sandbank Point gabbro, contact between the leucogabbro and the melanogabbro with a cross-cutting late mafic dyke. (A) Range of the MgOand SiO2 content of the gabbro suite. (B) Ternary tectonic discrimination diagrams: La–Y–Nb (Cabanis and Lecolle, 1989); MnO–TiO2–P2O5

(Mullen, 1983).

aplitic veins and granitoid dykes remains untested byU–Pb geochronology.

2.3. Sandbank Point gabbro

The Sandbank Point gabbro is a separate unit ofgabbroic rocks spatially associated with the Cinq-Cerfgneiss at Three Islands, Sandbank Point and Cinq-CerfBay (Figs. 2 and 3). Mapping shows that the gabbrointrudes the Cinq-Cerf gneiss, although the original rela-tionship is mainly obscured by later deformation thathas caused deflection of the composite fabric in thegneiss around the gabbroic bodies. The Sandbank Pointgabbro is intruded by the Western Head granite andis faulted against the late Cambrian Wild Cove gran-ite (499 + 3/−2 Ma; Dunning and O’Brien, 1989) by theGrand Bruit Fault Zone. The gabbro has been dated aspart of the study.

The gabbro exhibits three main facies: melano-gabbro, leuco-gabbro and hornblendite. The melano-gabbro, the most common facies (Fig. 6), is composedof 65–70% amphibole (hornblende-actinolite), 30% pla-gioclase (An30–55), about 5% opaques and minor quartz,and locally approaches dioritic composition. Apatite,zircon and rare titanite are accessory phases. At Sand-bank Point, the gabbro is intruded by irregular dykesof leuco-gabbro. The contacts between the leuco-gabbroand the gabbro are sharp to diffuse and have cuspate andlobate shapes (Fig. 6A), indicating that the two facies

were coeval (e.g. Wiebe, 1991). Exposed only at ThreeIslands, the hornblendite shares a gradational contactwith the melano-gabbro, and it is interpreted as an ultra-mafic cumulate. The only relicts of primary features areplagioclase crystals with subhedral tabular shapes and aweak concentric zoning, otherwise the gabbro exhibits agranoblastic texture, which is interpreted to be a productof autometamorphism. Major and trace element geo-chemical characterization indicates that this is a tholeiiticgabbro with a minor transitional volcanic arc signature(Fig. 6; Valverde-Vaquero, 1997).

2.4. Folded dioritic dykes (Three Islands)

At Three Islands, a set of refolded dykes of apliteand amphibole-bearing granitoid intrudes the SandbankPoint gabbro (Fig. 7A and B) and the gneiss. The pres-ence of small-scale refolded folds, not observed in theWestern Head granite, suggest that these dykes are pre-Silurian, an interpretation confirmed by the new U–Pbdating (see below).

3. New mapping of Silurian intrusive rocks

3.1. Western Head granite

The Western Head granite is a 15 km-long body ofgranite (O’Brien, 1990), which has been dated in twoseparate localities, east of the area of study, at 429 ± 2 Ma

8 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

Fig. 7. (A) Gabbro enclaves and refolded compositional banding in pre-Silurian dioritic dyke at Three Island; (B) Titanite in contact with recrystallizedplagioclase and green hornblende (U–Pb sample BHOB-71-88); (C) Western Head granite showing a “gneissic” area with ductile deformation, adeformed mafic enclave and small late mafic dykes with sharp contacts; (D) high temperature D2 isoclinal folding in the Western Head granite(Three Islands). (E) Disharmonic folding in thermally softened Cinq-Cerf gneiss (local D2 deformation), the granite inyections merge with thegranite dykes in Fig. 4. (F) Penetrative mylonitic fabric (D3) in the Western Head granite. (G) Microtexture of the S3 mylonitic fabric in the dykesof Western Head granite of Fig. 4A and B (U–Pb sample 94PV11), shear sense of top to the north (thrust). (H) Titanite porphyroblast associated tothe D3 mylonitization of the late porphyritic mafic dykes.

and 430 ± 2 Ma (Fig. 1B; O’Brien et al., 1991). TheWestern Head granite is a composite intrusion of gran-ite and granodiorite that shows extensive mingling withdisrupted mafic dykes and enclaves. Locally, the gran-ite contains variably deformed enclaves of the Cinq-Cerf gneiss and the Sandbank Point metagabbro. AtGrand Bruit, Sandbank Point and Three Islands, high-temperature deformation of the folded and sheared maficand gneissic enclaves imparts a gneissic aspect to thegranite (Fig. 7C). However, these rocks grade, over a

distance of ca. 2 km, into lower strain, homogeneousgranite near East Diver Head. Despite variable green-schistfacies mylonitization of the granite, clear intrusiverelationships are preserved with the Cinq-Cerf gneiss andthe Sandbank Point gabbro.

3.2. Late dykes

Several swarms of late dykes cross-cut the folds in theWestern Head granite and the Cinq-Cerf gneiss (O’Brien

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et al., 1993; Fig. 7C), and are particularly dense near EastDiver Head (Fig. 2). Although the dykes are variablyoverprinted by a mylonitic foliation they are not folded,and show sharp, straight, angular contacts. A penetra-tive mylonitic fabric, parallel to that in the Western Headgranite, is variably developed in these dykes, particularlyin thinner examples. Dyke thickness ranges from 1 m to10 cm; locally, chilled-margins are preserved. O’Brien(1990) describes equivalent dykes being locally cross-cut by the 419 ± 2 Ma Otter Point granite (O’Brien etal., 1991), which itself hosts variably deformed maficdykes. There are four types of late dykes: grey dioriticdykes, green mafic dykes, felsic aplitic dykes, and por-phyritic mafic dykes. These hornblende-bearing maficporphyritic dykes are the last generation and were sam-pled for U–Pb geochronology.

4. Deformation

Four main phases of deformation can be identi-fied based on overprinting relationships in the Cinq-Cerf gneiss and younger cross-cutting units (Valverde-Vaquero, 1997). The pre-Silurian structures, groupedunder a D1 phase, form the composite gneissic folia-tion (S1) in the gneiss, which is cut by the Western Headgranite. The subsequent D2 and D3 phases and a final D4brittle phase overprint the Silurian Western Head gran-ite. In addition there is evidence for a local pre-Siluriandeformation between formation of the gneiss and theSilurian D2 deformation.

4

pCt(iagtofcobsTcf(

0.1–0.3 mm recrystallized matrix of quartz and feldsparwith undulose extinction and subgrains, and plagioclaseaggregates with core-mantle structures (Passchier andTrouw, 1996). Local quartz veins cut the Sa

1 fabric ata high angle (Db

1 subphase; Sb1 fabric?) and are folded

by tight isoclinal Fc1 microfolds with an axial planar Sc

1fabric defined by biotite and chlorite. This suggests for-mation of the S1 gneissosity by mylonitization of thegranite under lower amphibolite conditions.

This composite D1 gneissosity is not present in eitherthe pre-Silurian granodiorite or the Sandbank Pointgabbro. The granodiorite is older than the gabbro butstill preserves igneous textures, suggesting that forma-tion of the gneiss during the D1 event(s) took placebefore the intrusion of these pre-Silurian bodies (seeSection 6).

A pre-Silurian event that postdates formation of thegneiss is locally preserved at Three Islands, where small-scale pre-Silurian granitoid dykes in the Sandbank Gab-bro contain a compositional banding with tight isocli-nal folds overprinted by open D3 folds (Fig. 7A). TheU–Pb data corroborates that this isoclinal folding is pre-Silurian, and separate in time from the formation of thegneiss. This deformation is very local and is tentativelycorrelated with the generation of the Dc

1 structures in thegneiss.

4.2. Siluro-Devonian deformation events

Later phases of deformation overprint both the gneiss

.1. Pre-Silurian deformation

The microstructural elements, and fold interferenceatterns observed in the S1 gneissic fabric of theinq-Cerf gneiss permit separation of three genera-

ions of D1 pre-Silurian structures and microstructuresDa

1, Db1, and Dc

1), whose end result is the compos-te S1 gneissosity. Boudins (D1) folded by D3 foldsnd local F1 intrafolial folds in the amphibolite bandedneiss and the granitic orthogneiss provide evidence ofhe polyphase character of the D1 deformation. Somef the F1 intrafolial folds show basin and dome inter-erences, which demonstrate an Fb

1–Fc1 folding of the

ompositional banding (Sa1). The fabric in the granitic

rthogneiss (Fig. 4B) is a composite Sa1–Sc

1 gneissicanding. Sections cut perpendicular to the L1 inter-ection lineation show three microstructural elements.he oldest fabric (Sa

1) is a schistosity defined by aompositional banding and oriented biotite. In the Sa

1abric, the quartzo-feldspathic load-bearing frameworksensu Handy, 1990) of the granite has collapsed into a

and the Silurian Western Head granite, but with differ-ent intensity. Extensive folding and ductile shearing ofenclaves, disrupted mafic dykes, and the magmatic com-positional banding demonstrate the syn-kinematic natureof the Western Head granite. This syn-magmatic to solid-state high-temperature deformation, which constitutesthe D2 phase of deformation, is restricted to the WesternHead granite and areas where the granite has thermallysoftened the Cinq-Cerf gneiss (Fig. 7D and E). D2 defor-mation ended before the intrusion of the late mafic dykeswarms. These late dykes are overprinted by a penetra-tive mylonitic foliation (S3). The S3 mylonitic foliationand the L3 lineation are particularly well developed inthe Western Head granite, which was retrogressed undergreenschist facies conditions during the D3 myloniti-zation (Fig. 7F–H; Valverde-Vaquero, 1997). Open F3folds with axial planes parallel to the S3 mlylonitic fabricare observed in the gneiss, where it has escaped exten-sive development of the S3 penetrative foliation (Fig. 4).Local D3 reworking of the gneiss around the compe-tent pre-Silurian intrusions has produced a local S1–S3fabric in the gneiss, which is deflected around these

10 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

bodies (Fig. 5). The kinematic analysis indicates thatthe D3 deformation was produced by oblique sinistralthrusting of the Cinq-Cerf gneiss along the Grand BruitFault followed by dextral shearing (O’Brien et al., 1993;Valverde-Vaquero, 1997). Late sets of conjugate brittlefaults and joints were formed during a final D4 episodeof minor brittle deformation.

5. U–Pb geochronology

U–Pb dating of zircon and/or titanite was carriedout on samples of granitic Cinq-Cerf orthogneiss (A),three pre-Silurian intrusions (B–D), a dyke of West-ern Head granite (E) that cross-cuts the gneiss and isoverprinted by the D3 mylonitization, and a titanite-bearing porphyritic mafic dyke (F). Sample preparationincludes air abrasion of the selected mineral fractions(Krogh, 1982). Isotope dilution was carried out using amixed 205Pb/235U spike. The U and Pb separation andpurification techniques for zircon and titanite followedmodified versions of those of Krogh (1973) and Manheset al. (1979), respectively. Isotopic ratios were measuredwith a MAT 262 multicollector thermal ionization massspectrometer equipped with a secondary electron multi-plier ion-counting system. Total procedural blanks wereless than 10 pg Pb for zircon and 20 pg Pb for titanite.The total Ublank was below 1 pg. Regression lines andintercept ages are calculated using the method of Davis(1982), this method emphasizes the more concordantpoints. In addition, and for comparison, the same regres-

Ludwig’s Isoplot. This age of 646 Ma coincides with a“concordant” age, sensu Ludwig (2003), of 642 ± 4 Ma(MSWD 0.30) for the subconcordant fraction Z1 (0.5%discordant). Z6 was not abraded, is more discordant,and the discordia line including fractions Z1–Z6 hasan upper intercept at 675 ± 17 Ma and a lower inter-cept at 432 ± 28 Ma (MSWD 0.62), using Isoplot. Thelower intercept coincides with the age of the youngercross-cutting Western Head granite from the same out-crop (Fig. 4; sample E; see below). Using the age ofthe granite to pin the lower intercept at 431 ± 2 Ma, theresulting discordia line has a 97% probability of fit andan upper intercept age of 675+12/−11 Ma, according tothe method of Davis (1982). The geometrical positionof the unabraded fraction (Z6; Fig. 8A), to the left ofthe 646 Ma discordia line of fractions Z1–Z5, suggeststhat the isotope systematics have been disturbed at thetime of intrusion of the nearby Western Head granite.The subconcordant fractions Z1–Z5 are interpreted tohave undergone Pb-loss at ca. 431 Ma from 675 Ma zir-con, resulting in a discordia line with a very small angleof intersection with the concordia curve. This data set isbest interpreted if the “concordant” age of 642 ± 4 Ma offraction Z1 and the upper intercept at 675+12/−11 Maof the Z1–Z6 discordia line are considered, respectively,as the youngest and oldest possible age limits for theintrusion of the orthogneiss. It is the authors’ view that675+12/−11 Ma represents the most accurate estimatefor the protolith age of the granitic orthogneiss.

sion lines are reported using Isoplot (Ludwig, 2003).Uncertainties on the isotopic ages are reported at the95% confidence level. Further details of the procedurecan be found in Dube et al. (1996).

5.1. U–Pb samples and results

5.1.1. Cinq-Cerf gneiss: granitic orthogneiss (A)This granitic orthogneiss is the oldest intrusive mem-

ber of the Cinq-Cerf gneiss and has been emplacedinto metasedimentary psammitic gneiss and schist. Thesample yielded large amounts of high quality euhe-dral zircon. The zircon fractions contain stubby (1:3width/length ratio), multifaceted, sharp, inclusion-freeclear prisms. Seven zircon fractions were analyzed(Table 1; Fig. 8A). One fraction (Z7) is discordantsuggesting the presence of Proterozoic inheritance.Five fractions (Z1–Z5) are sub-concordant with errorellipses touching the concordia curve. These five frac-tions define a discordia line (not shown) with an upperintercept of 646 ± 18 Ma and a negative lower inter-cept of −149 ± 1300 Ma and an MSWD of 0.52 using

5.1.2. Pre-Silurian granodiorite (B)The dated granodiorite postdates metamorphism and

formation of the gneissosity in the Cinq-Cerf gneissand predates the formation of the injection migmatite.Four zircon analyses were performed (Fig. 8B). Frac-tions Z1–Z3 are formed by stubby euhedral, inclusion-free, gem-quality prisms. Fraction Z4 consists of smalleuhedral elongated (1:5 length/width ratio) prisms, andwas not air abraded, in order to constrain the discordialine. The larger degree of discordancy of fraction Z4 isattributed to greater radiation damage of the crystal dueto the higher U concentration (twice that of the otherfractions; Table 1) and lead diffusion facilitated by thelarger length/width ratio, compared with the other frac-tions. The four analyses define a discordia line (MSWD1.6) with upper and lower intercepts at 584 ± 8 Ma and325 ± 26 Ma. This discordia line calculated after themethod of Davis (1982) has a 14.8% probability of fitwith an upper intercept of 584 + 7/−6 Ma and a lowerintercept of 326 Ma (Fig. 8B). The upper intercept isinterpreted as the best estimate for the crystallizationage.

P.Valverde-Vaqueroetal./P

recambrian

Research

148(2006)

1–1811

Table 1U–Pb data

Description (fraction) Weight (mg) Concentration Measured Corrected atomic ratios Age (Ma)

U (ppm) Pb rad(ppm)

TotalcommonPb (pg)

206Pb/204Pb 208Pb/206Pb 206Pb/238U(+/−)

207Pb/235U(+/−)

207Pb/206Pb(+/−)

206Pb/238U 207Pb/235U 207Pb/206Pb

94-PV-12: Cinq-Cerf gneiss, granitic orthogneiss, Sandbank Point-East Diver Head, 11500–81750Z1 M. stb. eu. prisms AB 0.0112 76 7 9 664 n.d. 0.10470 (64) 0.884 (13) 0.06120 (82) 642 643 646Z2 M. stb. eu. prisms AB 0.0786 79 9 12 3277 0.2451 0.10327 (58) 0.8713 (35) 0.06119 (28) 634 636 646Z3 M. stb. eu. prisms AB 0.0293 76 9 23 653 0.2307 0.10335 (64) 0.873 (12) 0.06128 (72) 634 637 649Z4 M. stb. eu. prisms AB 0.0651 69 8 11 2626 0.2399 0.10327 (56) 0.8729 (48) 0.06130 (16) 634 637 650Z5 M. stb. eu. prisms AB 0.0726 75 9 7 4998 0.2399 0.10232 (84) 0.8637 (55) 0.06122 (34) 628 632 647Z6 S. stb. eu. prisms NAB 0.1276 159 15 38 3045 0.1359 0.08936 (34) 0.7322 (28) 0.05943 (10) 552 558 583Z7 M. stb. eu. prisms AB 0.0311 93 13 32 756 0.2225 0.13075 (92) 1.3481 (92) 0.07478 (42) 792 867 1062

94-PV-6: Weakly deformed granodiorite, Sandbank Point-East Diver Head, 11000–81600Z1 M. stb. prisms. AB 0.1353 112 12 17 5282 0.2580 0.09299 (44) 0.7611 (34) 0.05936 (16) 573 575 580Z2 M. stb. prisms. AB 0.1295 111 11 73 1130 0.2518 0.09019 (30) 0.7351 (29) 0.05911 (12) 557 560 571Z3 S. prisms (1:3–1:5) AB 0.2043 132 13 65 2323 0.2433 0.08822 (32) 0.7150 (26) 0.05878 (12) 545 548 559Z4 S. prisms. NAB 0.0366 205 25 9 3721 0.9143 0.07105 (38) 0.5571 (27) 0.05687 (18) 442 450 487

94-PV-4: Sandbank Point Gabbro, 10200–81150Z1 M. eu. prisms AB 0.0498 90 9 9 2856 0.2718 0.08962 (26) 0.7251 (23) 0.05868 (08) 553 554 551Z2 M. eu. prisms AB 0.0390 71 7 12 1305 0.2917 0.08949 (54) 0.7202 (66) 0.05836 (46) 553 551 543Z3 M. eu. gem prisms AB 0.1346 94 9 16 4570 0.2612 0.08859 (34) 0.7154 (25) 0.05857 (14) 547 548 551Z4 S. eu. gem prisms NAB 0.1622 105 10 30 3117 0.2321 0.08603 (36) 0.6921 (29) 0.05835 (10) 532 534 543

BHOB-2a-88: Deformed dioritic dyke, Three IslandsZ1 L. eu. prisms AB 0.167 212 20 13 24077 0.1508 0.08873 (26) 0.7166 (23) 0.05857 (06) 548 549 551Z2 L. eu. prisms AB 0.163 187 17 11 27209 0.1520 0.08892 (29) 0.7195 (24) 0.05863 (08) 549 550 556Z3 M. eu. prisms AB 0.127 223 21 9 17963 0.1530 0.08915 (31) 0.7218 (26) 0.05872 (09) 551 552 557Z4 L. eu. prisms AB 0.261 190 18 32 8728 0.1608 0.08923 (32) 0.7241 (27) 0.05885 (07) 551 553 562T1 L. brown Ttn AB 0.401 176 20 633 517 0.7467 0.07161 (32) 0.5539 (31) 0.05610 (15) 446 448 456T2 L. brown Ttn AB 0.436 237 24 708 675 0.5854 0.07193 (25) 0.5570 (24) 0.05613 (10) 448 450 457

94-PV-11: Western Head Granite, 11500–81750Z1 M. eu. prisms AB 0.1209 726 50 17 22740 0.1049 0.06846 (26) 0.5235 (20) 0.05547 (06) 427 428 431Z2 M. eu. prisms AB 0.1030 705 48 10 31803 0.1163 0.06818 (22) 0.5213 (18) 0.05546 (06) 425 426 431Z3 M. eu. prisms AB 0.0825 489 33 13 13194 0.1029 0.06818 (28) 0.5215 (21) 0.05547 (10) 425 426 431Z4 M. eu. prisms NAB 0.2189 792 54 99 7466 0.1047 0.06797 (22) 0.5202 (18) 0.05551 (06) 424 425 433Z5 M. eu. prisms AB 0.1776 622 42 16 29250 0.1135 0.06744 (20) 0.5157 (17) 0.05547 (06) 421 422 431

BHOB-2b-88: Mafic porphyritic dyke, post-Western Head granite, Three IslandsT1 L. brown Ttn AB 0.219 356 31 619 580 0.4400 0.06733 (28) 0.5131 (26) 0.05527 (14) 420 421 423

(1) Z, zircon; T (Ttn), titanite; S. = small (<80 �m); M. = medium (80–150 �m); L. = Large (>150 �m); stb., stubby (<1:3 width/length ratio); eu., euhedral; AB, air abraded (Krogh, 1982); NAB,not abraded. All zircon fractions were selected from the 0◦ non magnetic and the 0◦ and 1◦ magnetic fractions (Frantz separation). (2) Uncertainty in sample weight ± 0.0001 mg (2σ); (3) Atomicratios corrected for fractionation and spike, 8–12 pg Pb blank lab procedure, initial common Pb (Stacey and Kramers, 1975) and 1 pg U blank. Two sigma errors reported for corrected isotopicratios. (4) Sample location in UTM coordinates, 21TVC UTM zone and 100 km2.

12 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

Fig. 8. U–Pb concordia diagrams.

5.1.3. Sandbank Point gabbro (C)This sample of quartz-bearing, hornblende-rich gab-

bro/diorite was collected at Sandbank Point (Fig. 2).Four fractions of gem quality zircon were separatedfrom this rock (Table 1). Fraction Z4 was not abradedto help constrain the discordia line. Fractions Z1–Z3 arebetween 0.37 and 0.73% discordant. The two most con-cordant fractions (Z1 and Z2) provide a “concordant”age of 553 ± 1.4 Ma (MSWD 0.38). The discordia linedefined by all four fractions (MSWD 0.8; Fig. 8C) hasan upper intercept of 557 + 14/−5 Ma and a lower inter-cept of 321 Ma with a 46% probability of fit (Davis,

1982). Given the problems encountered with Pb-loss inprevious samples, and the fact that it is within uncer-tainty of the “concordant” age, the upper intercept ageat 557 + 14/−5 Ma is preferred as our best estimate ofthe crystallization age. Both this sample and sampleB, above, have lower intercepts of ca. 320 Ma (lateVisean/Namurian time). It is possible that these reflectdisturbance of the isotopic systems during Allegheniandeformation and basin inversion, documented in thenearby Sydney Basin (Gibling et al., 2002), the edge ofwhich lies offshore of the Hermitage Flexure basementcomplex.

P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18 13

5.1.4. Deformed dioritic dyke with mafic enclaves(D)

This dyke, located in Three Islands (Fig. 2) containsenclaves of gabbro and is folded by F1c folds and F2 openfolds. Titanite occurs in contact with green amphiboleand plagioclase (oligoclase) forming a recrystallized gra-noblastic texture (Fig. 7B). The titanite porphyroblastsare interpreted to be post-F1c and pre-F2. Four fractionsof clear euhedral abraded zircon are clustered opposite a206Pb/238U age of 550 Ma with 207Pb/206Pb ages of 551,556 and 562 Ma. These do not overlap and define a shortmixing line with a lower intercept of 547 + 2/−7 Maand an upper intercept of 1460 Ma (MSWD 0.29). Thelower intercept at 547 Ma and the 551 Ma 207Pb/206Pbage of fraction Z1, since this is the fraction with theleast amount of inherited component, set respectivelythe youngest and oldest limits for the crystallization ageof the rock (Fig. 8D).

Analyses of two fractions of abraded titanite over-lap with 206Pb/238Uages of 448 and 446 Ma, and207Pb/206Pb ages of 457 and 456 Ma respectively.Because of the common Pb correction, the 206Pb/238Uages are considered more reliable in this case. The age ofisotopic closure of the titanite in this rock is estimated at448 + 9/−3 Ma, this upper error includes the 207Pb/206Pbages as well (Fig. 8D).

5.1.5. Mylonitic Western Head granite (E)This sample was collected from the same outcrop as

6drdz

All zircon fractions are U-rich (792–489 ppm; Table 1).Despite strong abrasion the analyses are slightly discor-dant; this is attributed to radiation damage and minorPb-loss (Krogh, 1982). Five clustered zircon analysesyield a weighted average of the 207Pb/206Pb ages of431.5 ± 1.1 Ma using ISOPLOT (MSWD 0.42), whichis interpreted as the crystallization age.

5.1.6. Hornblende porphyritic dyke (F)The hornblende porphyritic dykes cut all other dyke

swarms and have a variably developed mylonitic fabric(late D3). No zircon is present but titanite grows lateafter ilmenite during green schist facies retrogressionand deformation (Fig. 7H). One titanite multigrain frac-tion was analysed. The fraction is U-rich (ca. 355 ppm)and the resultant analysis is 0.79% discordant with a206Pb/238U age of 420 ± 3 Ma (Fig. 8F), interpreted tobe the time of the greenschist facies event.

6. Discussion

6.1. Chronology and correlation of LateNeoproterozoic magmatism and deformation

New field data and geochronology from the Cinq-Cerf area demonstrate that the oldest events in thepre-Silurian basement block of the western HermitageFlexure are the formation of the psammitic and amphi-bolitic paragneisses and the emplacement of a suite

ed in th

75 Ma granitic orthogneiss (Figs. 2 and 4). The graniteyke cuts the gneissosity in the orthogneiss and the sur-ounding banded gneiss and the boudinaged amphiboliteykes. The granite is overprinted by the D3 myloniti-ation and intruded by a swarm of late mafic dykes.

Fig. 9. Sequence of late Neoproterozoic events record

of ca. 675 Ma granitic magmas (Fig. 9). The absoluteage of the sedimentary protoliths of the paragneissesremains undetermined and the significance of the 2.0 Gainheritance pattern in the zircon population is unclear.The regional deformation and amphibolite-grade

e Cinq-Cerf gneiss and its volcanosedimentary cover.

14 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

metamorphism associated with the formation of theCinq-Cerf gneiss is constrained by the emplacementof 584 +7/−6 Ma granodiorite in the gneiss and thepresence of clasts of the gneiss in the conglomerate at thebase of the 585 Ma Whittle Hill sandstone. Preservationof primary igneous features in the 584 Ma granodiorite(Fig. 5C) and the low metamorphic grade of the adjacentvolcano-sedimentary sequence indicate that there is norecord of significant regional-scale metamorphic eventssubsequent to the 585 Ma magmatism.

The 675 + 12/−11 Ma age of the granitic orthogneisssupports correlations with Neoproterozic gneissic rockselsewhere in the pre-Silurian basement of the Her-mitage Flexure, namely those 70 km farther east atGrey River (Blackwood, 1985), previously dated at686 + 33/−15 Ma (Dunning and O’Brien, 1989). The579 ± 10 Ma age of metamorphic titanite in the GreyRiver gneiss (Dunning and O’Brien, 1989) is interpretedto reflect the tectonothermal event responsible for for-mation of the gneiss, and is consistent with the datapresented above. The existence of coeval magmatic rocksin similar amphibolite-grade gneiss at Cinq-Cerf andGrey River, and in magmatic arcs east of and adjacent tothe Hermitage Flexure area, on the Connaigre Peninsula(O’Brien et al., 1995, 1998), demonstrate the regionalscale of the ca. 680 Ma magmatic event and argue forfirst-order linkages amongst these terranes in the Neo-proterozoic.

6.2. Neoproterozoic magmatic events and the

O’Brien et al., 1998, 1999; Dube et al., 2001; Sparkes etal., 2005). Extensive datasets from both regions clearlypoint to first-order links and correlation among ca.590–570 Ma geological events in the Hermitage Flex-ure and in the type Avalon Zone, and are consistent withtheir common and coeval volcanic arc formation (e.g.O’Brien et al., 1990, 1996, 1998, 1999, 2001; Dube etal., 1995, 2001; Sparkes et al., 2005).

The metallogenically important ca. 590–570 Mamagmatic episode was followed by the intrusion ofthe 568–563 Ma granite, granodiorite and tonalite ofthe Roti intrusive suite, which locally stitches the con-tact between the Cinq-Cerf gneiss and the low-gradevolcano-sedimentary cover prior to its reworking inthe Grand Bruit Fault Zone (Dunning and O’Brien,1989; O’Brien et al., 1991; O’Brien et al., 1993). Thecrystallization of the Roti intrusive suite is broadlycoeval with emplacement of 566 + 2/−7 Ma gabbroand a 565 ± 5 Ma intermediate dyke in the volcano-sedimentary succession (Dube et al., 1995). Their intru-sion is arguably coeval, within error, with emplacementof the 557 + 14/−5 Ma Sandbank gabbro (note that theformer two samples have analyses less than 1% dis-cordant, which overlap the concordia curve at 560 Ma).The intrusion of the 547 + 2/−7 Ma dioritic dykes in theSandbank Point gabbro is the final Late Neoprotero-zoic magmatic pulse recorded in the immediate area.The significance of recrystallized 448 + 9/−3 Ma titan-ite in these dykes is unclear, but magmatic events of thisage are known from elsewhere in the Hermitage Flexure

Neoproterozoic basement–cover relationship

The new data reveal that the basement block wasthe site of several later pulses of felsic to interme-diate Neoproterozoic magmatism, beginning as earlyas 585 Ma (Fig. 9). Emplacement of granodiorite plu-tons in the Cinq-Cerf gneiss was coeval with felsicpyroclastic volcanism in the Whittle Hill sandstone-Third Pond tuff succession; these events were thenfollowed by ca. 575 Ma emplacement of granodioriteand felsic porphyry dykes and sills into the low-gradestrata (Dube et al., 1995). The latter hypabyssal mag-matism was genetically linked to widespread develop-ment Late Proterozoic advanced argillic alteration andhigh-sulphidation epithermal gold mineralization in thevolcano-sedimentary package (Hope Brook Mine; Dubeet al., 1995).

Similar styles and ages of not only plutonism, vol-canism and sedimentation, but also hydrothermal alter-ation and high-sulphidation epithermal gold mineraliza-tion are well documented east of the Hermitage Flexureregion in both the Avalon and Burin Peninsula (e.g.

region (Dunning, unpublished, in O’Brien and O’Brien,1992; van Staal et al., 1996).

These data demonstrate magmatic links betweenhigh- and low-grade metamorphic elements of the pre-Silurian basement in the western Hermitage Flexure and,together with the U–Pb age of the older orthogneiss,support the notion of depositional links and a basement-cover relationship between the Cinq-Cerf gneiss andthe Whittle Hill sandstone-Third Pond tuff volcano-sedimentary succession (e.g. O’Brien et al., 1991, 1996).Similar crosscutting and/or depositional relationshipsbetween ca. 680 and younger Neoproterozoic rocks havebeen described from the Avalon Zone in the aforemen-tioned Connaigre Peninsula region (e.g. O’Brien et al.,1995).

The latest Neoproterozoic (post-570 Ma) magmatismin the Cinq-Cerf area is coeval with volcanic events in theAvalon Zone east of the Hermitage Fault. In the westernAvalon Zone, however, 570 Ma and younger volcanismis characteristically peralkaline and subaerial in nature(O’Brien et al., 1990). In contrast, tuffs of this age in theeastern Avalon Zone occur as laminae and beds in deep

P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18 15

turbidite-filled basins containing well-preserved marineEdiacaran biota (Narbonne, 2005; Hofmann et al., 2005).

6.3. Neoproterozoic deformation (post-585 Ma)

The first regional deformation of the Late Neoprotero-zoic low-grade volcanosedimentary cover of the Cinq-Cerf gneiss postdates the emplacement of 576–562 MaRoti intrusive suite and the coeval, 576–565 Ma minorintrusions into the Whittle Hill sandstone-Third Pondtuff sequence. Both the volcanosedimentary successionand these intrusions contain the same D1 folds andthe axial planar cleavage S1 (Fig. 9). A younger setof 499–495 Ma gabbro and granodiorite plutons (e.g.Dunning and O’Brien, 1989; O’Brien et al., 1991) cross-cut the D1 structures and bracket the D1 deformationof the cover between the Latest Neoproterozoic and theLate Cambrian. According to O’Brien et al. (1993), ear-lier mylonitization of the contact between the Cinq-Cerfgneiss and the 568 Ma Roti intrusive suite ocurred alongthe Grand Bruit Fault Zone. The D1 deformation in thevolcano-sedimentary cover may be linked with the lateDc

1 subphase in the gneiss and the Dc1 deformation of the

547 + 2/−7 Ma dioritic dyke (Fig. 7A). The intrusion ageof this dyke coincides, within error, with a 545 Ma mon-azite age from a 566 Ma aplitic dyke in the Grand BruitFault (O’Brien et al., 1993). This monazite age is notinterpreted to reflect a major high-temperature tectono-thermal event in the local basement. It may record alower-temperature regional overprint, or local heat inputf

awDtu1lviaaTugZ

pZit

similarities noted above suggest that they formed partof the same active margin, but were not necessarily sep-arate terranes (Barr and White, 1996). In this respect,it is important to note that the Avalon Zone was itselfa composite collage in the Neoproterozoic, comprisedof temporally and spatially discrete arc sequences andmarine basins developed over ca. 200 million years fromca. 760 to 545 Ma (O’Brien et al., 1996, 2001). Thiscomplex character, which predates deposition of thecharacteristic Cambrian cover sequence, precludes sim-ple inclusion or rejection of Neoproterozoic terranes inthe Appalachian mobile belt with Neoproterozoic rocksof the “type” Avalon Zone, as described in the earlierliterature (e.g. Williams, 1979).

6.4. Chronology, nature and regional correlation ofPaleozoic events

The Paleozoic overprint on the Cinq-Cerf gneissoccurred mainly in the Silurian (Fig. 9), during Salinicorogenesis (cf. Dunning et al., 1990), and is related inlarge part to emplacement of the Western Head granite atca. 430 Ma, and is coeval with the onset of voluminoussubaerial felsic volcanism and coarse-grained terrige-nous siliciclastic sedimentation in basins that openedalong the north edge of the exposed Late Proterozoicbasement (O’Brien et al., 1991). This magmatic activity,which is widespread throughout the Hermitage Flexureat this time (e.g. Dunning et al., 1990), and local defor-mation during emplacement of the Western Head granite,

rom this final pulse of Late Neoproterozoic magmatism.The correlation of deformation events in the 580 Ma

nd younger rocks in the Neoproterozoic basement blockith deformation affecting coeval rocks east of theover-Hermitage fault is uncertain, but consistent with

he presence throughout the latter area of a regionalnconformity beneath the lower Cambrian (e.g. King,988). Data presented above are also consistent with theack of angular discordance within the ca. 570–550 Maolcano-sedimentary successions of Avalonian rocksmmediately east of the Hermitage Flexure (O’Brien etl., 1995, 1998). The hiatus at the proposed unconformityt the base of the ca. 585 Ma Whittle Hill sandstone-hird Pond tuff succession may be coincident with thenconformity at the base of the ca. 580–550 Ma Mus-ravetown Group and its equivalents in the type Avalonone (O’Brien et al., 1990, 1996).

Existing data cannot prove which, if any, of the dis-arate magmatic arc complexes comprise the Avalonone (sensu stricto; cf. O’Brien et al., 1996) were phys-

cally linked to the Neoproterozoic basement block ofhe Hermitage Flexure area in the Neoproterozoic. The

accounts for the high-temperature character of the D2deformation of the granite and the thermally softenedadjacent rocks.

The gneiss and the Western Head granite underwentductile inhomogeneous deformation under greenschistfacies conditions during oblique sinistral thrusting anddextral strike-slip shearing along the Grand Bruit FaultZone (D3 deformation). Local partial overprint and ret-rogression of the late mafic dykes hosting 420 ± 3 Matitanite by D3 mylonitization indicate that D2 and D3 aretwo separate events.

Emplacement of late mafic dykes are presumedrelated to dyke swarms associated with the intrusionof the 419 ± 2 Ma Otter Point granite (O’Brien et al.,1991, 1993) and voluminous emplacement of magmasinto the crust, throughout the Hermitage Flexure, at thattime. The D3 deformation in the gneiss is consideredequivalent to the D2 penetrative deformation of the LateProterozoic cover along the Cinq-Cerf Fault (Dube etal., 1995), and linked to closure of the Silurian volcano-sedimentary basins between 420 and 418 Ma (O’Brienet al., 1991), and the onset of Acadian orogeny.

16 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

The Paleozoic history of Avalonian rocks in the Neo-proterozoic basement complex of the Hermitage Flexurecontrasts with that of equivalent rocks in the Avalon Zonefarther east (cf. O’Brien et al., 1996). In the latter area,the early Paleozoic record is one of shale-dominatedplatformal sedimentation (see reviews in O’Brien et al.,1990; Landing, 1996). The contrasting record indicatesthat, in the Paleozoic, the basement complex constitutedpart of a separate terrane from the type Avalon Zone.This has been referred to as Avalonian (sensu lato) byO’Brien et al. (1996), or as Ganderia (van Staal et al.,1996; Valverde-Vaquero et al., 2006). Therefore the LateNeoproterozoic-Early Cambrian events here describedare related to an earlier dispersal and dismembermentof the Avalonian margin of Iapetus, leading to the rift-ing of Ganderia from Avalonia. This breakup likelybegan sometime after 570 Ma, coeval with rifting andbasin formation across the Avalon Zone (O’Brien et al.,1996).

7. Summary

The combination of detailed mapping and U–Pbgeochronology reveals the following major points:

1 The Cinq-Cerf gneiss is a composite unit that includessupra-crustal gneiss and granitic orthogneiss; theprotolith age of the latter has been established as675 + 12/−11 Ma.

2 Formation of the Cinq-Cerf gneiss is constrained by

orthogneiss. The migmatitic elements in the gneissare injection migmatites associated with granite intru-sions post-dating formation of the gneiss.

4 Younger Neoproterozoic magmatic events includeemplacement of the 557 + 14/−5 Ma Sandbank gab-bro and 547 + 2/−7 Ma diorite dykes into the Cinq-Cerf gneiss.

5 The 547 Ma dykes have a recrystallized tectonic fabriccontaining 448 + 9/−3 Ma titanite. Isoclinal folding ofthis fabric is interpreted as correlative with the Dc

1subphase of deformation in the Cinq-Cerf gneiss.

6 Four phases of deformation have been identified basedon relationships in the Cinq-Cerf gneiss and youngercross-cutting units. The D1 deformation is polypha-sic and has three subphases. The Da

1 phase, whichproduced the composite gneiss banding (S1) in thegneiss, is cut by 431.5 Ma plutons and predates rocksas old as 584 Ma. The age of the later subphaseDc

1, which is associated with tight isoclinal folds,is not constrained. Potentially, it could be youngerthan 584 Ma if it correlates with the F1 folds in the547 Ma diorite and the D1 folds in the Whittle Hillsandstone.

7 Major overprinting of the Cinq-Cerf gneiss occurredin mid- to late Silurian time, and commencedwith local high-temperature deformation (D2) of thegneiss, associated with the intrusion of the syn-kinematic Western Head granite at 431.5 ± 1 Ma.

8 The D3 phase produced widespread low-grademylonitization associated with thrusting of the Cinq-

the 675 + 12/−11 Ma protolith age of the graniticorthogneiss and the 584 + 7/−6 Ma crystallizationage of granodiorite intrusive into the gneiss. Thisca. 585 Ma granodioritic magmatism in the gneis-sic basement south of the Grand Bruit Fault Zone(GBFZ) is coeval with previously dated 585 ± 5 Maeruption of felsic tuff in the adjacent low-gradevolcano-sedimentary sequence north of the GBFZ.The presence of clasts of amphibolitic gneiss inthe conglomerate at the base of the 585–580 Mavolcanosedimentary package suggests a basement-cover relationship between the Cinq-Cerf gneissand the Whittle Hill sandstone-Third Pond tuffvolcano-sedimentary succession, and confirms thepre-585 Ma age of the gneiss-forming tectonothermalevent.

3 Blastesis of green amphibole (hornblende) and para-genesis with green clinoamphibole (hornblende andactinolite), albite and epidote in the amphibole-richbanded gneiss suggest formation of the gneiss underlower amphibolite facies conditions. This is consistentwith the microfabric observed in the 675 Ma granitic

Cerf gneiss and the Western Head granite along theGrand Bruit Fault Zone, and is dated by 420 ± 3 Matitanite from mafic dykes. This is the main phase ofpenetrative deformation and is responsible for par-tially bringing the D3 and D1 structures into par-allelism. The resultant composite S3–S1 fabric isdeflected around the competent 584 Ma granodioriteand 557 Ma gabbro. The preservation of the Late Pro-terozoic S1 fabrics, despite the D3 mylonitic overprint,is attributed to strain hardening after the D1 event.

9 The Late Neoproterozoic tectonic and magmaticrecord of the basement block of the western HermitageFlexure bears strong similarities to that in Proterozoicrocks of the Avalon Zone in eastern Newfoundland.New data further support a first-order Neoproterozoiclinkage of the rocks in these areas. The early to mid-Paleozoic history of the Hermitage Flexure basement,however, contrasts with that of the Avalon Zone tothe east and supports the earlier view (O’Brien etal., 1996) that, during that time, the basement blockevolved as a terrane separate from the type AvalonZone.

P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18 17

Acknowledgements

The mapping and geochronological investigation ofthe Cinq-Cerf gneiss and adjoining rocks was completedas part of the Ph.D. thesis of P.V.V. at Memorial Univer-sity of Newfoundland. Funding was provided through anNSERC operating grant to G.R. Dunning. The authorsacknowledge the major contribution of B.H. O’Brien toour understanding of the geology of the western Her-mitage Flexure area, and that of the Cinq-Cerf region inparticular, and the insight gained by way of our manyfield- and office-based discussions. B.H. O’Brien alsoprovided the senior author with samples of deformeddioritic dykes from the Three Islands area and is spe-cially thanked for reviewing an earlier version of themanuscript. C.R. van Staal and S. Samson are thankedfor their constructive reviews of the manuscript. A. Kerris thanked for sharing information on earlier samplingfor Nd isotopic studies.

Appendix A. Supplementary data

Supplementary data associated with this articlecan be found, in the online version, at doi:10.1016/j.precamres.2006.03.001.

References

Barr, S.M., White, C.E., 1996. Contrasts in Late Neoproterozoic-early

B

C

C

C

C

C

Davis, D.W., 1982. Optimum linear regression and error estimationapplied to U–Pb data. Can. J. Earth Sci. 19, 2141–2149.

Dube, B., Dunning, G., Lauziere, K., 1995. Geology of the HopeBrook Mine, Newfoundland, Canada: a preserved Late Protero-zoic high-sulfidation epithermal gold deposit and its implicationsfor exploration. Econ. Geol. 93, 405–436.

Dube, B., Dunning, G.R., Lauziere, K., Roddick, J.C., 1996.New insights into the Appalachian Orogen from geology andgeochronology along the Cape Ray fault zone, southwest New-foundland. Geol. Soc. Am. Bull. 108, 101–116.

Dube, B., O’Brien, S.J., Dunning, G.R., 2001. Gold deposits indeformed terranes: examples of epithermal and quartz-carbonateshear zone-related gold systems in the Newfoundland Appalachi-ans and their implications for exploration. In: North Atlantic Min-erals Symposium, pp. 31–35 (Extended Abstracts volume).

Dunning, G.R., O’Brien, S.J., 1989. Late Proterozoic-Early Paleozoiccrust in the Hermitage Flexure, Newfoundland Appalachians: U/Pbages and tectonic significance. Geology 17, 548–551.

Dunning, G.R., O’Brien, S.J., Colman-Sadd, S.P., Blackwood, R.F.,Dickson, W.L., O’Neill, P.P., Krogh, T.E., 1990. Silurian orogenyin the Newfoundland Appalachians. J. Geol. 98, 895–913.

Evans, D.T.W., Kean, B.F., Dunning, G.R., 1990. Geological studies,Victoria Lake Group, Central Newfoundland, Department of Minesand Energy, Geological Survey Branch. Report 90-1, pp. 131–144.

Gibling, M.R., Langenberg, W., Kalkreuth, W.D., Waldron, J.W.F.,Courtney, R., Paul, J., Grist, A.M., 2002. Deformation of UpperCarboniferous coal measures in the Sydney Basin: evidence forlate Alleghanian tectonism in Atlantic Canada. Can. J. Earth Sci.39, 79–93.

Handy, M.R., 1990. The solid-state flow of polymineralic rocks. J.Geophys. Res. 95 (B6), 8647–8661.

Hofmann, H.J., O’Brien, S.J., King, A.F., 2005. Hiemalora and otherEdiacaran fossils of Northeastern Newfoundland, and correlationswithin Avalonia. Geol. Soc. Am. Abstr. Prog. 37 (7), 485.

Kerr, A., Jenner, G.A., Fryer, B.J., 1995. Sm–Nd isotopic geochemistry

Paleozoic tectonothermal history between Avalon composite ter-rane sensu stricto and other possible peri-Gondwanan terranesin southern New Brunswick and Cape Breton Island, Canada.In: Nance, R.D., Thompson, M.D. (Eds.), Avalonian and RelatedPeri-Gondwanan Terranes of the Circum-North Atlantic: Boulder,Colorado, Geological Society of America Special Paper 304, pp.95–108.

lackwood, R.F., 1985. Geology of the Grey River area, southwestcoast of Newfoundland: Current Research, Newfoundland Depart-ment of Mines and Energy. Mineral Development Division Report85-1, pp. 153–164.

abanis, B., Lecolle, M., 1989. Le diagramme La/10–Y/15–Nb/8: unoutil pour la discrimination des series volcaniques et la mise enevidence de processus de melange et/ou de contamination crustale.Compt. Ren. Acad. Sci., Ser. II 309, 2023–2029.

horlton, L.B., 1978. Geology of the La Poile area (110/9), Newfound-land, Newfoundland Department of Mines and Energy. Report78-5, p. 14.

horlton, L.B., 1980. Geology of the La Poile River area (110/16),Newfoundland Department of Mines and Energy. Report 80-3, 86pp.

horlton, L.B., 1984. Geological development of the southern LongRange Mountains, southwest Newfoundland: a regional synopsis.Ph.D. Thesis. Memorial University of Newfoundland, St. John’s,Newfoundland, 580 pp.

ooper, J.R., 1954. The La Poile-Cinq-Cerf map area, Newfoundland:Geological Survey of Canada. Memoir 276, 62 pp.

of Precambrianto Paleozoic granitoid suites and the deep structureof the southeast margin of the Newfoundland Appalachians. Can.J. Earth Sci. 32, 224–245.

King, A.F., 1988. Geology of the Avalon Peninsula, Newfoundland:Department of Mines and Energy. Geological Survey Branch Map88-01, Scale 1:250,000.

Krogh, T.E., 1973. A low-contamination method for hydrothermaldecomposition of zircon and extraction of U and Pb for isotopicage determinations. Geochim. Cosmochim. Acta 37, 485–494.

Krogh, T.E., 1982. Improved accuracy of U–Pb zircon ages by cre-ation of more concordant systems using an air abrasion technique.Geochim. Cosmochim. Acta 46, 637–649.

Landing, E., 1996. Avalon: Insular continent by the Late Precambrian.In: Nance, R.D., Thompson, M.D. (Eds.), Avalonian and RelatedPeri-Gondwanan Terranes of the Circum-North Atlantic: Boulder,Colorado, Geological Society of America Special Paper 304, pp.29–63.

Ludwig, K., 2003. Isoplot 3.00: a geochronological toolkit forMicrosoft Excel. Berkeley Geochronological Center Special Pub-lication 4.

Manhes, G., Allegre, C.J., Dupre, B., Hamelin, B., 1979. Lead-leadsystematics, the “age of the earth” and the chemical evolution ofour planet in a new representation space. Earth Planet. Sci. Lett.44, 91–104.

Mullen, E.D., 1983. MnO/TiO2/P2O5: a minorelement discriminantfor basaltic rocks of oceanic environments and its implications forpetrogenesis. Earth Planet. Sci. Lett. 62, 52–62.

18 P. Valverde-Vaquero et al. / Precambrian Research 148 (2006) 1–18

Nance, R.D., Murphy, B.J., Keppie, J.D., 2002. A Cordilleran modelfor the evolution of Avalonia. Tectonophysics 352, 11–31.

Narbonne, G.M., 2005. The Ediacaran biota: Neoproterozoic origin ofanimals and their ecosystems. Annu. Rev. Earth Planet. Sci. 33,421–442.

O’Brien, B.H., 1987. The lithostratigraphy and structure of the GrandBruit—Cinq-Cerf area (parts of NTS areas 110/9 and 110/16),southwestern Newfoundland, Current Research, NewfoundlandDepartment of Mines and Energy. Report 87-1, pp. 311–334.

O’Brien, B.H., 1988. Relationships of phyllite, schist and gneiss in theLa Poile Bay-Roti Bay area (parts of 110/9 and 110/16), southwest-ern Newfoundland, Current Research, Newfoundland Departmentof Mines. Report 88-1, pp. 109–125.

O’Brien, B.H., 1990. Geology of the La Poile Bay-Couteau Bay region(parts of 110/9 and 11/19) southwest Newfoundland. 1:50.000scale map. Newfoundland Department of Mines and Energy, Map90-07.

O’Brien, B.H., O’Brien, S.J., Dunning, G.R., 1991. Silurian cover,Late Precambrian-Early Ordovician basement, and the chronologyof Silurian orogenesis in the Hermitage Flexure (NewfoundlandAppalachians). Am. J. Sci. 291, 760–799.

O’Brien, B.H., O’Brien, S.J., 1992. Day 3: Burgeo road (south end),Burgeo to Buck Lake. In: Colman-Sadd, S.P., Cawood, P.A., Dun-ning, G.R., Hall, J.M., Kean, B.F., O’Brien, B.H., O’Brien, S.J.(Eds.), Lithoprobe East in Newfoundland (Burgeo transect): ACross-section through the Southwest Newfoundland Appalachi-ans, Field Excursion A-7 Guide Book. Geological Association ofCanada Annual Meeting, Wolfville, pp. 72–84.

O’Brien, B.H., O’Brien, S.J., Dunning, G.R., Tucker, R.D., 1993.Episodic reactivation of a Late Precambrian mylonite zone on theGondwanan margin of the Appalachians, Southern Newfoundland.Tectonics 12 (4), 1043–1055.

O’Brien, S.J., Strong, D.F., King, A.F., 1990. The AvalonZone typearea: southeastern Newfoundland Appalachians. In: Strachan,R.A., Taylor, G.K. (Eds.), Avalonian and Cadomian Geology of

Avalonian rocks on the Burin Peninsula, Newfoundland: Impli-cations for gold exploration. In: Current Research. Newfound-land Department of Mines and Energy. Report 99-1, pp. 275–296.

O’Brien, S.J., Dunning, G., Dube, B., O’Driscoll, C.F., Sparkes, B.,Israel, S., AndKetchum, J., 2001. New insights into the Neopro-terozoic geology of the central Avalon Peninsula (NTS map areasIN/6, IN/7 and IN/3, eastern Newfoundland. In: Current Research.Newfoundland Department of Mines and Energy. Report 00-1, pp.169–189.

Passchier, C.W., Trouw, R.A.J., 1996. Microtectonics. Springer-Verlag, Berlin, p. 289.

Rogers, N., van Staal, C.R., 2002. Towards a Victoria Lake Supergroup:a provisional stratigraphic revision of the Red Indian to Victorialakes area, Central Newfoundland. Current Research, Newfound-land Department of Mines and Energy, Geological Survey. Report02-1, pp. 185–195.

Sparkes, G.W., O’Brien, S.J., Dunning, G.R., Dube, B., 2005. U–Pbgeochronological constraints on the timing of magmatism, epither-mal alteration and low-sulphidation gold mineralization, easternAvalonZone, Newfoundland. In: Current Research, Newfoundlandand Labrador Department of Natural Resources. Report 05-01, pp.115–130.

Stacey, J.S., Kramers, J.D., 1975. Approximation of terrestrial leadisotope evolution by a two-stage model. Earth Planet. Sci. Lett. 26,207–221.

Van Staal, C.R., Sullivan, R.W., Whalen, I., 1996. Provenance and tec-tonic history of the Gander margin in the Caledonian/Appalachianorogen: implication for the origin and assembly of Avalonia. In:Nance, D., Thompson, M. (Eds.), Avalonian and Related Peri-Gondwanan Terranes of the Circum-North Atlantic: Boulder, Col-orado, Geological Society of America Special Paper 304, pp.347–367.

Valverde-Vaquero, P., 1997. An integrated field, geochemical andU–Pb geochronological study of the southwest Hermitage Flex-

the North Atlantic. Blackie & Son Ltd., Glasgow-London, pp.166–194.

O’Brien, S.J., O’Driscoll, C.F., Greene, B.A., Tucker, R.D., 1995.Pre-Carboniferous geology of the Connaigre Peninsula and theadjacent coast of Fortune Bay, southern Newfoundland. In: Cur-rent Research, Newfoundland Department of Natural Resources,Geological Survey. Report 95-1, pp. 267–298.

O’Brien, S.J., O’Brien, B.H., Dunning, G.R., Tucker, R.D., 1996.Late Neoproterozoic Avalonian and related peri-Gondwanan rocksof the Newfoundland Appalachians. In: Nance, R.D., Thompson,M.D. (Eds.), Avalonian and Related Peri-Gondwanan Terranes ofthe Circum-North Atlantic: Boulder, Colorado, Geological Societyof America Special Paper 304, pp. 9–28.

O’Brien, S.J., Dube, B., O’Driscoll, C.F., Mills, J., 1998. Geologicalsetting of gold mineralization and related hydrothermal alterationin late Neoproterozoic (post-640 Ma) Avalonian rocks of New-foundland, with a review of coeval gold deposits elsewhere in theAppalachian Avalonian belt. In: Current Research, NewfoundlandDepartment of Mines and Energy, Geological Survey. Report 98-1,pp. 93–124.

O’Brien, S.J., Dube, B., O’Driscoll, C.F., 1999. High-sulphidation,epithermal-style hydrothermal systems in Late Neoproterozoic

ure (Newfoundland Appalachians, Canada) and the Sierra deGuadarrama (Iberian Massif, Central Spain): a contributionto the understanding of the geological evolution of circum-Atlantic peri-Gondwana. Ph.D. Thesis. Memorial University ofNewfoundland.

Valverde-Vaquero, P., van Staal, C.R., McNicoll, V., Dunning, G.R.,2006. Mid-Late Ordovician magmatism and metamorphism alongthe Gander margin in central Newfoundland. J. Geol. Soc. Lond.163, 347–362.

Wiebe, R.A., 1991. Co-mingling of contrasted magmas and genera-tion of mafic enclaves in granitic rocks. In: Didier, J., Barbarin, B.(Eds.), Enclaves and Granite Petrology. Developments in Petrol-ogy, vol. 13. Elsevier, Amsterdam, pp. 393–402.

Williams, H., 1979. Appalachian orogen in Canada. Can. J. Earth Sci.16, 792–807.

Williams, H., Colman-Sadd, S.P., Swinden, H.S., 1988. Tectonic-stratigraphic subdivisions of Central Newfoundland. GeologicalSurvey of Canada, Paper 88-1B, pp. 91–98.

Williams, H., 1995. Geology of the Appalachian-Caledonian Orogenin Canada and Greenland, Geological Survey of Canada, Geologyof Canada, vol. 6, 944 pp. (also Geological Society of America,The Geology of North America, vol. F-l).