Structural correlation within the Kapuskasing uplift

Structural correlation within the Kapuskasing uplift1 J.T. BUR~NALL Department of Geology, St. Lawrence University, Canton, NY 13617, U.S.A.

A.D. LECLAIR Geological Survey of Canada, 601 Booth Street, Ottawa, ON KIA OE8, Canada

D.E. MOSER~

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by Depository Services Program on 06/04/13 For personal use only.

Department of Geological Sciences, Queen2 University, Kingston, ON K Z 3N6, Canada AND

J. A. PERCIVAL Geological Survey of Canada, 601 Booth Street, Ottawa, ON KIA OE8, Canada Received June 18, 1993 Revision accepted January 17, 1994 Comparison of progressive deformation and metamorphic history within and between the tectonic domains of the Kapuskasing uplift indicates significant variation in age and style of deformation across this large segment of the central Superior Province; multiple stages of tonalite and granitoid intrusion, melt generation, polyphase diachronous deformation, and likely rapid deep burial of supracrustal rocks collectively produced the complex character of this example of Archean mid to deep crust. At least four Archean deformation phases are recognized, although not all are of regional extent. Dated structural chronology suggests that the locus of the earliest recorded deformations migrated to deeper crustal levels with time. Pre-2680 Ma deformation (local D,-D,) within high-level tonalites is correlated with deformation in the Michipicoten supracrustal belt. The apparent earliest deformational fabrics at deeper crustal levels in the granulite terrane of the Kapuskasing structural zone occurred between 2660 and 2640 Ma. Archean third and fourth phase deformation phases (-2667 to -2629 Ma) are present at mid-crustal and deeper levels and deform post-2667 Ma metaconglomerate; these resulted in large-scale folding and subhorizontal ductile shear zones, which seem to represent an important transitional zone that separated a passive upper crust from continued ductile strain at deeper levels. Subsequent uplift of the high-grade rocks was accomplished in multiple stages, initiated prior to 2.45 Ga and likely culminated around 1.9 Ga, although continued movement occurred as late as 1.14 Ga. The Ivanhoe Lake fault zone, along which much of the uplift must have occurred, exhibits some evidence of ductile deep-thrust-related fabrics, but most of the observed structures are brittle to brittle -ductile and steeply inclined. A broad zone of pervasive cataclasis and brittle -ductile shear zones is a characteristic feature of the fault zone throughout its length, and both dextral and sinistral offset are locally present. Clear ground evidence for major transcurrent or thrust displacements, however, has not been recognized. Une comparaison, de la dCformation progressive et de l'histoire mktamorphique des domaines ou interdomaines tectoniques du soulkvement de Kapuskasing, rCv2le que les dges et les styles des d~formationsvarient considCrablement au travers ce large segment de la province du lac SupCrieur centrale; les nombreux Cvknements intrusifs de tonalite et de granitoide, la gknkration de magmas, la dkformation polyphasCe diachrone, et I'enfouissement vraisemblablement rapide des roches supracrustales, ont tous contribuC au dCveloppement complexe de cet exemple de crodte archeerne a des niveaux mCdian B profond. Au moins quatre phases de dCformation sont reconnues, quoiqu'elles ne soient pas toutes d'ktendue rkgionale. La datation des kvknements structuraux suggkre que le foyer des prem5res dkformations enregistrkes se dkpla~aitdans le temps vers les niveaux crustaux plus profonds. La dCformation antkrieure a 2680 Ma (D, -D2 locale), dans les hauts niveaux de la tonalite, est mise en corrklation avec la dCformation de la zone supracrustale de Michipicoten. Les fabriques de dtformation, apparemment les plus anciennes, qui sont observCes dans le terrane 2 granulites de la Zone structurale de Kapuskasing, 2 des niveaux crustaux plus profonds, ont CtC produites entre 2660 et 2640 Ma. La troisikme et la quatriBme phase de dkformation archCenne ( 2667 B 2629 Ma) apparaissent au niveau de la crodte mkdiane et B plus grande profondeur, et elles ont affect6 les conglomCrats postCrieurs 2 2667 Ma; le rCsultat est la crCation de zones de plissements a grande Cchelle et de zones de cisaillement ductile, subhorizontales, qui reprksentent possiblement une zone de transition majeure, skparant la croDte supkrieure passive d'avec les niveaux plus profonds qui Ctaient asujettis 2 une dCformation ductile continue. Le soul2vement substquent des roches de degrk de mktamorphisme ClevC s'est produit par Ctapes, amorcC avant 2,45 Ga, il a connu sa phase culminante il y a d'environ 1,9 Ga, quoique le mouvement ait Ctk entretenu jusqu'h une kpoque aussi tardive que 1,14 Ga. La zone de failles du lac Ivanhoe, le long de laquelle le soulkement fut trks actif, prksente certains indices de fabrique ductile relike a un charriage profond, cependant la majorit6 des structures observCes sont de type fragile 2 fragile-ductile, et elles sont fortement inclintes. L'existence d'une grande zone de cataclase pCnetrante et de zones de cisaillement fragile-ductile est la particularit6 qui caractkrise la zone de failles sur toute sa longueur, et localement des dCcrochements dextre et senestre sont prCsents. I1 n'existe pas sur le terrain d'indices suffisarnment clairs pour permettre la reconnaissance de dCplacements dus i des charriages ou 2 des failles coulissantes. [Traduit par la rkdaction]

-

-

Can. J. Earth Sci. 31, 1081-1095 (1994)

ILithoprobe Publication 562; Geological Survey of Canada Contribution 30794. 'Present address: Royal Ontario Museum, Department of Geology, 100 Queen's Park, Toronto, ON M5S 2C6, Canada. Pr~ntedin Canada 1 Imprim6 au Canada


CAN. J. EARTH SCI. VOL. 31, 1994

Introduction In recent tectonic models for the southern Superior Province, greenstone-granite terranes are interpreted as island arcs and metasedimentary belts as fore-arc accretionary wedges, amalgamated in the late Archean (Percival and Williams 1989; Card 1990; Williams et al. 1992). Key elements of these broad models are detailed studies of structural sequences within individual lithotectonic domains and along their boundaries, which are available for a few areas (e.g., Hudleston et al. 1988; Bauer and Bidwell 1990). Many parts of the Abitibi and Wawa belts have received detailed structural study as a result of their high mineral potential; however, relatively little attention has been devoted to the tectonic evolution of the d e e ~ structural levels of these belts. Studies of deeper structural levels are timely for several reasons. Firstly, recent models of gold mineralization in highlevel shear zones relate to metamorphic and tectonic activity in the deep crust (Colvine et al. 1988; Cameron 1989; Bursnall et al. 1989; Leclair et al. 1993); yet detailed structural studies demonstrating linkage do not exist. Secondly, recent Lithoprobe lines in the Abitibi belt (e.g., Green et al. 1990; Jackson et al. 1990) underscore the need for an understanding of structural character on a crustal scale. The gently dipping features observed at depths of a few kilometres on reflection profiles cannot readily be reconciled with steep surface structures. Finally, recent conceptual and analytical advances have provided tools capable of addressing some of these questions. Kinematic analyses provide a framework in which to view large-scale crustal movements, while developments in U -Pb geochronology permit dating and correlation of structures in different areas and at diverse crustal levels. Several structural levels, from the well-known greenstone belts of the Abitibi and Wawa subprovinces to deep crustal granulites of the Kapuskasing structural zone, are represented within the Kapuskasing uplift (Percival and Card 1983; Percival and McGrath 1986; Leclair 1990). The uplift is divided by brittle faults of probable Proterozoic age (Percival and Peterman 1994) into Archean domains with discrete lithological, metamorphic, and structural character. Although structural sequences have been established within individual domains, this paper presents the first attempt to integrate the structural and chronological data into a coherent regional framework. This synthesis produces a complex picture of three-dimensional crustal development over time. The Kapuskasing uplift The Kapuskasing uplift (KU) of the Superior Province is a region containing a west-to-east greenschist to granulite facies metamorphic transition, interpreted as an oblique cross section through an Archean greenstone belt (Percival and McGrath 1986). The high-grade part of the uplift, the Kapuskasing structural zone (KSZ; Thurston et al. 1977) is a curvilinear, north-northeast-trending,predominantly fault-bounded Archean granulite terrane (Fig. 1). This high-grade belt, and its associated prominent geophysical anomalies, transects the east -westtrending Wawa -Abitibi volcano-plutonic and Quetico-Opatica metasedimentary-plutonic subprovinces (Percival and Card 1985; Percival and McGrath 1986; Leclair 1992) from eastern Lake Superior to James Bay, a distance approaching 500 km (Card and Ciesielski 1986; Percival et al. 1991; Fig. 1). Highpressure granulite- and amphibolite-facies gneiss (Percival 1983) and associated rocks are bounded to the south and east

by the Ivanhoe Lake fault zone and its extensions (Bad River i d Kineras faults) to the north (Fig. l), a clearly defined discontinuity on lithological and aeromagnetic maps (Thurston et al. 1977; Percival 1990; West and Ernst 1991; Leclair 1992). The northwestern boundary corresponds to the Foxville and Lepage faults in the north and the Saganash Lake fault in the central KU (Percival and McGrath 1986; Leclair 1992). In the south, the granulites are transitional to amphibolite facies rocks of the Wawa gneiss domain (Moser 1994; Fig. 1). A variety of interpretations and models for the KU have been proposed. These include the following: an intracratonic basement-uplift style (Fountain and Salisbury 1981) southeastdirected thrust (Percival and Card 1983; Percival and McGrath 1986) and earlier suggestions of upper crustal thinning (Garland 1950), Proterozoic rifting (Innes et al. 1967; Bennett et al. 1967; Burke and Dewey 1973), and sinistral transcurrent faulting (Watson 1980). The thrust-uplift model has in part been supported by gravity interpretations (Percival and McGrath 1986) and Lithoprobe seismic reflection surveys (Cook 1985; Percival et al. 1989; Geis et al. 1990). Evidence of significant transcurrent movement along the KU has recently been interpreted by Goodings and Brookfield (1992) and West and Ernst (1991) on the basis of aeromagnetic data. West and Ernst (1991) proposed a modification of the simple thrust-generated geometry by inferring 70 km of dextral Proterozoic displacement based on the configuration of the Matachewan dyke swarm. Paleomagnetic data from the same dykes supports significant dextral movement (Bates and Halls 1991). Furthermore, U -Pb, Rb -Sr, and 40Ar/39Argeochronological studies point to a protracted cooling history (Krogh and Moser 1994; Percival and Peterman 1994; Hanes et al. 1991, 1994). A complex uplift history appears probable and can locally be demonstrated in surface structures (Bursnall 1989, 1990). The Archean structure of high-grade gneisses and contiguous areas has received considerable recent attention in support of Lithoprobe activity (e.g ., Percival 1983; Leclair and Nagerl 1988; Leclair and Poirier 1989; Bursnall 1989, 1990; Moser 1988, 1989, 1993; Leclair 1990, 1992), following the earlier reconnaissance work by Bennett et al. (1967), MacLaren et al. (1968), Thurston et al. (1977), and Riccio (1979). Structural detail available from these studies varies not only with the exposure level in different field areas, but also with the intent and scale of the investigation, which range from regional reconnaissance to focussed structural analysis in specific areas (e.g., Bursnall 1989, 1990; Bursnall and ~ o s e 1989; r Moser 1988, 1989; Percival et al. 1991). The primary sources for the data base used in this regional compilation are indicated in Fig. 2.

Tectonic subdivisions of the Kapuskasing uplift The KU is composed of several tectonic blocks (Fig. I), each characterized by distinctive lithology, structure, and metamorphic grade. Metamorphic assemblages indicate variable paleopressure, implying differential uplift between the blocks and juxtaposition of different crustal levels (Percival 1985; Percival and McGrath 1986; Leclair and Nagerl 1988; Leclair and Poirier 1989; Leclair 1989, 1990). The predominantly northeasterly-trending boundary faults to these blocks coincide with prominent aeromagnetic lineaments (Leclair 1990; West and Ernst 1991) and, with the possible exception of the Wakusimi River fault (Leclair et al. 1993) and sections of the

BURSNALL ET AL.


post-Archean cover

SUBPROVINCE

SUBPROVINCE

WAWA SUBPROVINCE

KAPUSKASING

Fraserdale-Mooronee block

FIG. 1. Location map. Identification of fault-bounded tectonic blocks of the Kapuskasing uplift and adjacent terranes. Adapted from Percival and McGrath (1986) and Leclair and Nagerl (1988).

Ivanhoe Lake fault zone, are predominantly cataclastic in nature and presumed to be Proterozoic in age (Percival and Peterman 1994). The northernmost Fraserdale -Moosonee block, consisting mainly of granulite-facies paragneiss with some mafic gneiss, as well as minor diorite, tonalite, pyroxenite, and anorthosite, is contained between the west-dipping Foxville normal and Bad River thrust faults (Fig. 1) and has been interpreted as thrust-tip, pop-up (Percival and McGrath 1986), or flower structure (Goodings and Brookfield 1992). Garnet -orthopyroxene -plagioclase -quartz assemblages yield paleopressures of 0.83-0.94 GPa, indicating at least 13 km of uplift relative to lower-pressure granulite-facies rocks to the west (Percival and McGrath 1986). A 65 km gap without granulites (or positive aeromagnetic anomaly) between the Fraserdale -Moosonee and the Groundhog River blocks has been interpreted as a downfaulted section against the Kineras normal fault (Percival and McGrath 1986) or as a strike-slip basin formed during sinistral transpression (Goodings and Brookfield 1992). The poorly exposed Groundhog River block contains upper

amphibolite- to granulite-faciesassemblages in mafic, tonalitic gneiss and paragneiss and is bounded to the west by the Saganash Lake fault, accommodating approximately 10 km of listric normal displacement to the west (Percival and McGrath 1986). Paleopressure estimates from this block are in the 0.7 - 1.0 GPa range (Percival and McGrath 1986; Leclair 1992) implying at least 15 km of uplift along the Ivanhoe Lake fault zone. This fault, which dips about 20" northwest, is cut by the Saganash Lake fault and may underlie the eastern Val Rita block to a depth of 20 km (Leclair et al. 1994). It juxtaposes background erosion levels of 10- 15 km in greenstone belts of the Abitibi belt with 30 - 35 krn levels in Kapuskasing granulites (Leclair 1989, 1990). Percival and McGrath (1986), assuming a thrust origin for the Ivanhoe Lake fault zone, interpreted the Groundhog River block as a perched thrust tip, a configuration supported in part by the presence of two small bodies of rnafic gneiss that may be outliers of the Groundhog River block to the north of the Nansen Creek fault (Figs. 1, 3). Both the Saganash Lake and Ivanhoe Lake faults are slightly offset by the Nansen Creek fault at the northern termination of the Groundhog River block (Fig. 1; Leclair and Nagerl

1 084

CAN. J. EARTH SCI. VOL. 31, 1994 I

LECLAIR 1992 LECLAlR AND POlRlER 1989

83"

I , 1986; Leclair and Nagerl 1988; Leclair 1992). LECLAIR AND NAGERL 1980

CC


35 km

48"-

FIG. 2. Principal map areas used for this study. BL, Borden Lake belt; CC, Cargill Complex; DB, Dishnish Batholith; SA, Shawmere anorthosite; SL, Shack Lake Pluton; WB, Windermere Batholith. Broken lines are major fault traces.

1988; Leclair 1990, 1992; Leclair et al. 1994). North-sidedown displacement of about 3 km is inferred from paleopressure determinations (Leclair 1990). The Chapleau block, the largest high-grade block in the uplift, is separated from the Groundhog River block by the Wakusimi River fault (Fig. 1) and contained between the southern continuation of the Saganash Lake and Ivanhoe Lake faults. The block broadens to the southwest where it merges with the Wawa gneiss domain along a north-trending 10 km wide zone to the east of Chapleau (Fig. 1). The zone is defined by lithological, structural, density, and seismic velocity changes reflecting the transition from granulite to arnphibolite facies (Percival 1986; Moser 1994). Since it obliquely transects the dominant east-west lithological trend, this transition allows for both lithological and structural correlation between deepcrustal (KSZ) and the mid-crustal levels of the uplift (e.g., the Borden Lake belt, Figs. 2, 3; Percival 198la, 1981b; Bursnall 1987; Moser 1994). The Val Rita block and contiguous parts of the Wawa subprovince (Wawa gneiss domain, Figs. 1, 3) consist mainly of xenolithic tonalitic gneiss (0.5-0.7 GPa) and metavolcanic rocks (0.4 -0.5 GPa) in the amphibolite facies, and a voluminous suite of massive and locally foliated granitoid plutons (0.4 -0.6 GPa; Leclair 1992). Granulite-facies paragneiss (0.8 GPa) occurs at the northwestern fault contact (Lepage fault) with the Quetico subprovince (Percival and McGrath

Percival and McGrath (1986) used gravity data to model the northern Lepage fault as a 60-70' northwest-dipping structure with 7 - 10 km of normal displacement; progressively less displacement is apparent southward (Leclair and Poirier 1989). The 1888 f 3 Ma Cargill carbonatite complex (L.M. Hearnan, personal communication, 1988) straddles the Lepage fault but is apparently offset 3 km dextrally (Sandvik and Erdosh 1977). Thus the Lepage fault existed prior to emplacement of the complex and was subsequently reactivated (Buchan and Ernst 1994). The Wawa gneiss domain (Fig. 1; Moser 1994), as defined here, occurs in the intervening ground between the southern Val Rita and Chapleau blocks and the Michipicoten greenstone belt to the west and is composed of tonalite, tonalitic and granodioritic orthogneiss plutons, and kilometre-scale belts of predominantly amphibolite-facies mafic gneiss and paragneiss. Within the eastern part of the domain an east -west-trending supracrustal assemblage, the Borden Lake belt (Moser 1994), made up of metasediment (including a distinctive polymict conglomerate), mafic and felsic metavolcanics, and mafic gneiss, continues 35 km to the east into similar rocks within the KSZ (Figs. 3, 5; Bursnall 1987).

Structural chronology within the KU: Archean deformation Although orientation data from structural features, such as planar and linear fabric elements, have been recorded in all recent studies, their relative timing may not have been defined. It is impossible in retrospect to fit many of the recorded structures into a chronological sequence of deformation phases and, as a result, confident correlation between even relatively close areas may not be possible. In most instances local deformation chronology has been constructed on the basis of outcrop-scale, not microscopic-scale, structures, since annealing in these high-grade rocks typically has eradicated all but the latest grain-scale anisotropic fabrics. Most studies have nevertheless recognized at least three distinct phases of deformation (Table 1) based on structural intersections and the relationship of structures to intrusive or melt events, such as mafic dykes, plutons, diatexite bodies, and other partial melt-generated material (e.g., granitoid veins and dykes). Correlation over large distances using purely morphological and local relative chronology is at best very risky and at worst may severely misdirect regional synthesis. An additional complication to structural correlation results from the possibility that some high-grade supracrustal sequences in the KU, such as the Borden Lake belt, may be allochthonous (Moser 1994). Map patterns (Figs. 3, 4) do, however, suggest some regionally consistent fold trends. In high-grade gneiss terranes, geochronological studies are critical in providing time constraints for regional structural correlation from disparate field areas. Although a significant volume of radiometric data is available from the KU and surrounding terranes (Hanes et al. 1994; Krogh and Moser 1994) only a small number of dates have been specifically directed at constraining structural history (e.g ., Moser 1994). The following section is a summary of structural evolution within each tectonic block of the KU and some adjacent areas. Correlation between blocks proposed by individual authors are also summarized, but an assessment of uplift-wide correlation is left to a later section. Progressive deformation phases and

BURSNALL ET

AL.

- Ilthclogical contact -fault / topogmphlc lineament


11111 Puskuta Lake shear zone

SUBPROVINCE

EXPLANATION PROTEROZOIC

Shack Lake pluton Floranna Lake cmplx.

Borden Lake belt metaconglomerate and quartz-feldspar

FIG. 3. Summary lithological map of the central Kapuskasing uplift. DB, Dishnish Batholith; SL, Shack Lake Pluton; WB, Windermere Batholith. Refer to Fig. 1 for fault identification; see also Fig. 5.

related structures for each block or subarea (i.e., Val Rita block (VR), Wawa gneiss domain (WGD), Borden Lake belt (BL), and Chapleau block (CB) are identified in the standard fashion (Dl, D2, F1, F2, etc.) and identified by block (e.g., VRDlrefers to the first deformation phase in the Val Rita block). Wawa Subprovince Val Rita block The Wawa gneiss domain and its northern extension, the Val Rita block have similar lithological, structural, metamorphic, and geochronological characteristics. In the Val Rita block demonstrable primary structures are rare but compositional layering in metavolcanics and metasediments has been

interpreted by Leclair and Nagerl (1988) as predominantly primary in origin (Leclair 1992) and enhanced during synmetamorphic deformation; wholly strain-generated layering is also recognized (Leclair and Poirier 1989). A preferred dimensional alignment of biotite and hornblende defines a regional, planar fabric (VRS1)that is subparallel to compositional layering in supracrustal rocks and to gneissic layering (Leclair and Poirier 1989; Leclair 1992). Rare intrafolial folds may be related to this deformation phase. East-plunging mesoscopic, tight to open folds of VRSl(F2 of Leclair and Poirier 1989) with a rare attendant axial surface fabric are particularly well developed in the western part of the block where they plunge south-southeast and may be equivalent to large-scale east-west-trending folds in the northern


TABLE1. Comparison of Archean structural history across the Kapuskasing uplift

Event

Val Rita block

D,

2730 Ma Gneissic layering and subparallel foliation

Wawa gneiss domain NW

Wawa gneiss domain SE (Chapleau area)

Gneissic layering

>2707 Ma Gneissic layering

East-trending upright folds

Intrafolial folds and planar fabric


2691 Ma Tight-open folds; variable trend

D,

I

Borden Lake belt Planar fabric in metavolcanics 2677 Ma 2667 Ma Pervasive planar fabric; intrafolial folds in mafic gneiss

2670 Ma

?2691Ma

Chapleau block SE Gneissic layering

Northnorthwest variable trend tight to isoclinal small-scale folds; ductile high-strain zones (2660 -2640 Ma ?)

2685 Ma D,

Large-scale tightclose northeasttrending upright folds

East-west fabric sub-parallel to steeply northwestdipping axial surface of kilometre-scale folds

? 2682 Ma

D,

2660 Ma

Ductile shears

Subhorizontal ductile shear zones

2682 Ma

Tight, large-scale, gently Tight, moderate to gentle southwest east-plunging synform northeast folds with with east-west steeply moderate to steep northwest-dipping axial surface fabric northwest-dipping axial surfaces; ductile shear zones Post-garnet growth gneissic fabric in mafic gneiss

2636 Ma Puskuta Lake shear zone 2665 Ma D5

Late extension at 2603 Ma

Dalton shear zone

Ductile shears contain lensoid garnet aggregates 2629 Ma Late extension at 2601 and 2586 Ma

2660 Ma North-northwest-trending open to gentle folds

North-northwest-trending North-northwestopen to gentle folds trending open synform

NOTE:Key constraining dates mentioned in the text as indicated. The designation of Dl, D,, etc., refers to the sequence within each subarea and does not imply regional equivalance.

Chapleau block that define the prominent map pattern south of the Wakusimi River fault (Leclair and Poirier 1989; Figs. 3, 4; see below). A regionally significant third set of northeast-trending folds (VRF3)has been identified by Leclair and Poirier (1989). These are large-scale (Figs. 3, 4) upright, gently-plunging structures, apparently without axial surface fabrics, which may also be present within the northern Chapleau block as refolds of the postulated VRF2equivalents. In the Kapuskasing area, narrow ductile shear zones exhihiting normal displacement occur in some tonalite outcrops and create a phacoidal shear array surrounding less-deformed lozenges (Leclair and Poirier 1989); they possess rare east- to west-plunging lineations and postdate VRF3,and therefore are late in the structural sequence. U-Pb zircon ages for multiply deformed tonalite gneiss in the Val Rita block give a crystallization age of 2725 k 5 Ma (Sullivan and Leclair 1992a), corroborated by a whole-grain lead evaporation result of 2724 f 3 Ma. These ages indicate that tonalitic magmatism was coeval with volcanic activity within the Michipicoten belt (2749-2696 Ma; Turek et al. 1982). U-Pb zircon ages from a unit of biotite-epidote granodiorite at 2686:: Ma and the Shack Lake quartz diorite pluton (2691': Ma) characterize the age of late- to posttectonic intrusions (Leclair 1992; Leclair and Sullivan 1991; Moser 1994). A weak foliation within the Shack Lake pluton and folded 2690 f 2 Ma tonalitic veinlets within tonalite

gneiss indicate younger deformation (Sullivan and Leclair 1992a), but the main regional deformation in the Val Rita block may have occurred prior to this. The Puskuta Lake shear zone Within the southern Val Rita block, a southeast-trending, 1-2 km wide, dextral ductile shear zone extends for at least 75 km from the eastern Wawa Subprovince (Leclair 1990). This gently curved zone (Fig. 3) possesses a well-developed, steeply northeast-dipping, mylonitic fabric and associated shallowly plunging stretching lineation that are cut by undeformed 2454 Ma (Heaman 1988) Matachewan dykes. The youngest Archean rock units affected by the zone belong to the 2682 f 3 Ma Dishnish Batholith (Fig. 3), and a titanite age obtained from the mylonite suggests that ductile deformation ceased by 2665 f 4 Ma (Sullivan and Leclair 1992b). The zone postdates all other structures so far described from the Val Rita block. The Puskuta Lake shear zone may be part of a fundamental crustal-scale structure (with a total strike length of > 700 km) that continues through high-grade rocks of the KSZ and joins major auriferous shear zones in the Abitibi Subprovince (Leclair et al. 1993). The correlation of these major neoArchean shear zones across different metamorphic terranes of the central Superior Province implies that such structures are subvertical in the upper crust becoming more gently northdipping at deeper levels (Leclair et al. 1993). If this model is

BURSNALL ET

AL.

I

correct then movement on this system may be an important element in the subsequent development of granulite metamorphism.


l

Wawa gneiss domain In general, planar fabrics and compositional layering in the Wawa gneiss domain maintain east-west strikes and dip predominantly to the north, with gentle dips generally more common towards the east. The timing of deformation and deformation style vary complexly across the domain and seven deformation fabric subareas have been defined by Moser (1994). The following is a brief summary. In the northwest, a pre-2684 Ma planar fabric and upright east-west-trending folds (WGDD2)are present both in the supracrustal units of the Michipicoten greenstone belt and the orthogneisses of the Wawa gneiss domain. These fabrics are transposed into a north-striking dextral shear at the contact between the two domains. The zone is cut by massive granodiorite and is thus likely formed prior to regional -2680 Ma plutonism observed nearby in the greenstone belt (Frarey and Krogh 1986). In the southeastern Wawa gneiss domain near Chapleau, minor isoclinal folds that may correlate with the WGDD2 folds to the northwest are affected by three younger deformation events, WGDD3,WGDD4,and WGDD5 (Moser 1994). The WGDD3phase resulted in regional shortening of both orthogneisses and kilometre-wide supracrustal assemblages, such as the Borden Lake belt in the eastern Wawa gneiss domain (BL in Fig. 2), which is contained within a tight, shallow east-plunging fold; this supracrustal sequence extends into the adiacent high-wessure granulite terrane of the Cha~leau "the east' WGDD3 be younger than 266jMa because it affects the Borden Lake metaconglomerate, which contains a cobble of that age and a 2675 f 2 tonalite body (Krogh . - 1993; Moser 1994). Layering in mafic metavblcanics and dioritic gneiss within the Borden Lake belt parallels steeply north-dipping gross lithological layering and constitutes the earliest recognized fabric (BLDI),which predates a 2677 Ma granodiorite (Moser 1994). This foliation is isoclinally folded (BLD2),and an associated planar fabric is manifest as flattened cobbles in the Borden ~ a k emetaconglomerate. Outcrop-scale tight BLD3 folds are related to the large east-plunging synform that contains the Borden Lake supracrustal package (Figs. 3, 4). Fabric trends in the adjacent tonalitic gneisses define the continuation of this fold to the west (Figs. 3, 4). A BLD3stretching lineation parallel to minor fold axes and elongation of metaconglomerate clasts preceded garnet porphyroblast growth. The relationship of a strong post-garnet fabric (BLD4)to later fabrics in the adjacent zones is uncertain. The BLD2and BLD3 structures outlined above have been constrained to the interval 2667 -2661 Ma (Moser 1994). Subhorizontal ductile shear zones (WGDD4)with strong planar fabrics and an east -west lineation occur to the west of the Borden Lake supracrustal belt. Deformed xenoliths in tonalitic gneiss within them exhibit high extensional strains of up to K (Flinn 1962) = 1.5. This fabric is succeeded by the development of ductile extensional faults (Moser 1989). Both of these WGDD4 phases occurred in the interval 2661 -2636 Ma (see below; Moser 1994). In the Chapleau area, subsequent north to northwest gentle warping of earlier fabrics comprises WGDD

5.

A 3 km wide west-northwest dextral ductile shear zone

-

LINEATION ANTIFORM 4 SYNFORM

+

PIG.4. Generalized fold and foliation-layering trends within the Kapuskasing uplift.

(Dalton shear zone) that postdates all plutonic rocks in the western Wawa gneiss domain (Moser 1994) may be equivalent in age to the Goudreau -Lochalsh deformation zone (Heather and Arias 1987), dated at < 2671 Ma (Corfu and Sage 1992), and to the Puskuta Lake shear zone. Kapuskasing structural zone Fraserdale-Moosonee block Exposure and access are poor in the Fraserdale -Moosonee block, and observations are limited to early reconnaissance maps (MacLaren et al. 1968), augmented by a few road and river transects (Percival 1985; Percival and McGrath 1986). High-grade rocks of the Fraserdale -Moosonee block truncate the east-west-trending Quetico and Wabigoon belts, themselves at granulite facies in their eastern 120 km (Percival 1985). A well-developed moderate to steeply north-dipping gneissosity and migmatitic layering characterizes these belts and may be accompanied by a moderately east-plunging rodding lineation (Percival 1989). East of the FraserdaleMoosonee block, the equivalent Opatica and Partridge River belts (MacLaren et al. 1968) are characterized by massive to foliated granitoid rock with minor supracrustal rocks in the amphibolite facies . The structure of the Fraserdale-Moosonee block is dominated by a prominent northeast-striking, moderately northwestdipping gneissosity that varies in character from migmatitic layering in paragneiss to a mylonitic ribbon quartz foliation in all rock types, including pegmatite. Rare rodding lineations


1088


plunge moderately to the southwest or northeast. It is unclear whether the magnitude of fabric development results from a single event of variable intensity or to later superimposed deformation. Mafic dykes, which are probable members of the Matachewan and Kapuskasing swarms, cut gneissic layering in the high-grade rocks but are cut locally by pseudotachylite veinlets. Thin dykes of mafic and lamprophyric composition, probably related to nearby alkalic rock - carbonatite complexes, locally cut highly fractured rock and are weakly sinistrally offset along late fractures. Groundhog River block Limited exposure within the Groundhog River block precludes detailed structural analysis. Where observed, these rocks display a well-developed compositional layering and a foliation defined by the preferred orientation of hornblende and biotite. The general orientation of planar structures varies along the length of the Groundhog River block (Figs. 3, 4). Gneissic layering strikes northeasterly and dips moderately to the northwest in the northernmost outlier of the Groundhog River block. Just south of the Nansen Creek fault, planar structures generally trend northward with steep dips to the east, but local variations suggest some large-scale folding. In the southern part of the block they strike northeasterly with moderate northwesterly dips, similar to the dominant trend in the Chapleau block. A shallowly northeasterly-plunging lineation has been observed (Leclair and Poirier 1989). Comparable paleodepth determinations across the Groundhog River block (Leclair 1990) indicate that the variations in structural trend are not a reflection of different crustal levels. Wakusimi River fault A zone of regularly layered northeast-trending, moderately northwest-dipping, grain-size-reduced gneiss constitutes this ductile shear zone, which separates the Groundhog River block from the northern Chapleau block (Leclair 1990; Leclair et al. 1993). It coincides with a prominent aeromagnetic intensity boundary that is truncated by the trace of the Ivanhoe Lake fault zone. Paleopressure estimates indicate minor postmetamorphic differential uplift (Leclair 1990). Cataclasite veinlets occur locally (Leclair and Nagerl 1988). Chapleau block Map patterns and aeromagnetic images suggest large-scale folds in parts of the Chapleau block (Figs. 1, 3). Examples include the areas south of the Wakusimi River fault (Leclair 1992; Percival 1981b; Figs. 3, 5) and south of the Shawmere anorthosite complex. The Borden Lake synform likely continues eastwards into the Chapleau block and Riccio (1979) has postulated a synformal configuration for the Shawmere anorthosite complex. Other large-scale apparent fold patterns are visible on 1 : 250000 aeromagnetic maps but have yet to be demonstrated on the ground. Synmetamorphic Archean deformation events (CBDl-CBD4) have collectively imparted a regionally pervasive, strong planar compositional anisotropy and resulted in the dominant east-west to northeast regional trend and low northerly dips of lithological units (Figs. 3, 4). Abundant field evidence indicates that the earliest deformation preceded injection of large volumes of tonalite. The earliest recognized fabric (CBSl)is a compositional layering within mafic gneiss and paragneiss that, for the most part, is parallel

to unit boundaries (Percival 1981a; Bursnall 1990); a stromatic gneissic layering within enclaves of mafic gneiss in tonalite gneiss and rare fold-like structures of uncertain origin are included (Bursnall 1990). Some modal layering within mafic gneiss may be a relic of primary compositional heterogeneity (Percival 1981a). The poorly preserved CBDlfeatures are succeeded by two fold sets. The earlier, CBF2,are small-scale, north-northwesttrending, tight to isoclinal, typically reclined folds of low to moderate plunge; attendant axial surface fabrics are uncommon. Many CBF2structures are true intrafolial folds, suggesting that the prominent regional gneissic layering is mainly a secondary (CBD2)composite fabric, the folded fabric being assigned to CBDl. A third deformation phase (CBD3)represents the latest of the high-grade deformations and may, in part, continue progressively into CBD4(equivalent to "late-D3" of Bursnall (1989)). Third phase folds are observed to refold CBF2and are tight, with gentle to moderately inclined, north- to northwest-dipping axial surfaces and moderate, west to northeast plunge. A subparallel mineral lineation and more common rodding lineation are present, and a poorly developed axial planar grain fabric is rare. CBD3and earlier folds locally possess curved hinge lines that are thought to have developed at least in part during a period of pervasive CBD4ductile shearing, which in places resulted in conversion of granulite assemblages to arnphibolite facies in mafic gneisses and the production of a pronounced grain fabric. CBD3hinge lines and a locally well-developed rodding lineation generally plunge shallowly to the northeast and to the northwest. Approximate cumulative local strain magnitude for the preand synmetamorphic deformation phases in the southeastern part of the Chapleau block are given by axial ratios of prolate clasts in metaconglomerate that exceed 12:1, and high axial ratios for deformed mafic inclusions in tonalitic gneiss that exceed 20: 1 in sections close to the principal finite extension direction (Bursnall 1990). CBD3folds in niafic gneisses in the central part of the Chapleau block mainly verge to the south and some are host to axial-surface-parallel leucosome veinlets. Folds similar to these occur close to the Ivanhoe Lake fault zone 15 km to the south. Modification by CBD4ductile shear zones occurs at both localities. To the north, pegmatite dated at 2580 Ma cuts these structures, whereas at the southern locality a minimum 1 Ma pegmatite (Krogh and Moser age is given by a 2629 1994); resetting of monazite at the latter indicates continued deformation at or younger than 2500 Ma (Krogh and Moser 1994). Recently exposed areas produced for the Canadian Continental Drilling Program's pilot project in the KSZ expose a similar structural sequence for the southern border to the Shawmere anorthosite (Bursnall and Moser 1989; Percival et al. 1991). Gently west-northwest-plungingisoclinal, and in places intrafolial, folds of compositional layering (?CBF2)are refolded by gently west-plunging, close to tight folds with steep northwest-dipping axial surfaces (?CBF3).Rare, open north-northeast-trending subhorizontal folds are also present in this section. The deformation sequence from within the anorthosite is locally ambiguous but Riccio (1979) has recognized isoclinal folds with shallow plunges to the south and west-southwest, and a related hinge-line-parallel mineral lineation; these folds possess moderate northwest-dipping axial surfaces to the north

+

-

1089

BURSNALL ET AL.


and are recumbent in the southern part of the body. A subsequent set of northeast-trending open subhorizontal folds has also been defined (Riccio 1979); close to the Ivanhoe Lake fault zone minor folds of this orientation fold cataclasite and pseudotachylite seams and are therefore likely of Proterozoic age (Percival 1981a; Bursnall 1990). Late broad and gentle northwest-plunging folds are also of uncertain age (Bursnall 1990), but could be equivalent to late folds in the Wawa gneiss domain (WGDD5; Moser 1994). Correlation of Archean deformation phases Inspection of a lithological compilation map of the central part of the KU (Figs. 3, 4) shows some consistent fold trends within and between the tectonic blocks described above. For example, map pattern alone suggests that the early northeasttrending folds in the northern Chapleau block (and the postulated equivalent structures in the Val Rita block) and those in the southeastern Chapleau block, which possess a more easterly trend, could be equivalent, but relative chronology indicates that the former structures are D2 in age whereas the latter are D3. Furthermore, the earlier fabrics in the Val Rita block predate 2691 Ma, whereas deformation of the Borden Lake belt metaconglomerate must postdate 2667 Ma (Krogh 1993). Table 1 outlines the structural history within the various domains. Although the structural sequences between some tectonic blocks seem similar, recent geochronological studies suggest significant deviations in the age of structural development and metamorphism, from the mid-crustal levels of the Wawa gneiss domain and the Val Rita block to the deepcrustal Chapleau and Groundhog River blocks (Krogh and Moser, this volume; Moser 1994; Krogh 1993). Such variation should be anticipated since similarity in style and relative position within the local structural sequence in itself does not indicate contemporaneity, but rather that the rock packages in each domain have undergone similar stages of structural development. Some diachroneity of structures and metamorphism is to be expected across such a large area as the KU (encompassing a range of conditions resulting from differences in crustal depth), but at the present scale of investigation it is impossible to trace many structural elements (folds, shear zones, etc.) with any confidence from one domain to another. Table 1 also includes key geochronological constraints on the timing of the main deformation phases. Earlier Archean deformation phases Most investigations have recognized a deformational component in the production of the regionally east-west to northeast-trending gneissic layering, and in homogeneous plutonic rocks the earliest deformation structure is locally represented by a biotite -hornblende foliation. In the western Wawa gneiss domain, development of the earliest fabrics predates 2684 Ma (Moser 1994), and in the Val Rita block, 2725 Ma tonalite gneisses are considered likely to have developed their prominent fabric prior to 2691 Ma (the age of the Shack Lake pluton; Leclair and Sullivan 1991). Deformed leucosome of 2690 Ma age indicates later deformation, of VRD2or VRD3age. Pervasive ductile deformation appears to have ceased by 2682 Ma (Sullivan and Leclair 19926). In contrast, the earlier fabrics in mafic gneiss and paragneiss in the high-pressure granulite terrane of the Chapleau block may be much younger. A metamorphic zircon date of 2650 f 2 Ma for mafic gneiss and 26272: Ma for leucosome in paragneiss (Percival and Krogh 1983), which partially defines

compositional layering and a strong composite fabric (CBDICBD2or younger), suggests that metamorphism, anatexis, and the development of the earliest preserved fabrics regionally become younger with increasing paleodepth. It is possible, however, that the 2627 Ma date relates to younger CBD4 shearing because the zone from which it was extracted contains a strong biotite planar fabric, a characteristic of some CBD4fabrics elsewhere. Krogh (1993) has further demonstrated younger ages with depth from metamorphic zircon ages of 2660 and 2640 Ma for stkcturally higher in ma& and lower localities in the eastern Chapleau block; CBD4shear zones in that area, however, may have significantly modified the synmetamorphic relationships. A boudin neck-line leucosome, dated at 2630 Ma, within mafic gneiss metamorphosed at 2640 Ma indicates late metamorphic extension (Krogh 1993); the relative structural age of this deformation is uncertain but is likely younger than CBD2(see above). First phase structures in Borden Lake belt mafic gneiss (BLD1)occurred prior to 2677 Ma, based on a cross-cutting foliated granodiorite on Borden Lake (Moser 1994). The oldest gneisses external to the belt in that area are greater than 2707 Ma (Percival and Krogh 1983), giving an upper limit for the maximum age of WGDDI.The earliest deformation phase Iwithin the Val Rita block and Wawa gneiss domain, WGDD WGDD2 and VRDl-VRD2, are also older than the Borden Lake metaconglomerate, which contains clasts as young as 2667 Ma (Krogh 1993). The earliest phase to affect the metaconglomerate is BLD2. It is possible, therefore, that whereas the earliest structures in the Wawa gneiss domain and Val Rita block may be contemporaneous, the earliest fabrics within the Borden Lake belt may not be equivalent and the early tectonic relationship of the Borden Lake belt to the enveloping gneisses is therefore unclear (see also Moser 1994). BLD3may predate regional upper-amphibolite facies metamorphism ( 2660 Ma; Moser 1994), since garnet overgrowths of elongate clast margins occur in the metaconglomerate. Metaconglomerate and associated units within the highgrade Chapleau block, close to the Ivanhoe Lake fault zone (Bursnall 1990) and here correlated with the Borden Lake belt, suggests that these post-2667 Ma supracrustal rocks must have been buried to mid- to deep-crustal depths prior to highpressure granulite metamorphism of 2660 to 2640 Ma age (ICrogh 1993). Clast composition in the eastern metaconglomerate indicates a varied lithological source, somewhat similar to rocks elsewhere in the KU (Bursnall 1990); some deformation occurred prior to incorporation, since some clasts contain quartz veins that are abruptly terminated at clast boundaries. No dates are available from the eastern locality but, similar to Borden Lake, the growth of garnet postdates clast elongation, placed in the CBD2to CBD3period (Bursnall 1989).

-

Later Archean deformation phases Archean postpeak metamorphism deformation resulted in a variety of structures that include regionally significant ductile shear zones in the Wawa gneiss domain and Chapleau block. The fourth deformation phase in the Wawa gneiss domain (WGDD4) consists of flat-lying shear zones (2661 to 2636 Ma; Moser 1993) that contain abundant evidence of extensional fabrics and a locally strong east-west lineation. These cut the western continuation of the Borden Lake synform in the Wawa gneiss domain tonalitic gneiss. Fourth phase structures within


1090


the Borden Lake belt (BLD4),which postdate garnet growth, may be related. Textural criteria, however, suggest that WGDD4and BLD4 may not be equivalent. WGDD4ductile shears experienced thorough annealing, producing polygonal granoblastic textures, whereas the BLD4fabrics possess a strong preferred dimensional orientation. It is thought, therefore, that WGDD 4 may have preceded BLD4(Moser 1994). Although U -Pb zircon ages indicate that CBD4shear zones might be younger than those in the Wawa gneiss domain, with a minimum age of 2629 in contrast to 2636 Ma (Krogh and Moser 1994), this regional period of pervasive ductile shear zone development is perhaps is the most extensive within the uplift; it is thought to represent a period of mid-crustal collapse closely following peak metamorphism (Moser 1993, 1994). A postpeak metamorphism high-strain event is implied by a monazite age of 2628 f 2 Ma (Krogh and Moser 1994) from strongly foliated rocks with west-plunging stretching lineation within a fault-bounded segment of the Ivanhoe Lake fault zone. Importantly, this section of the fault zone encompasses the surface extrapolation of strong northwest-dipping seismic reflections (Wu and Mereu 1993). Elsewhere, zircons from pressure shadow sweats within the metaconglomerate at Borden Lake have been dated at 2603 Ma (Krogh 1993; Moser 1994). Boudin neck-line infill at 2601 and 2586 Ma in the deeper levels of the granulite terrane of the Chapleau block (Krogh 1993) indicate late extension of regional significance. Northwest-trending folds that postdate pervasive latemetamorphic ductile shears are present in the Wawa gneiss domain (Moser 1994) and might be related to late regional warping in both the Wawa gneiss domain (WGDD5) and the Chapleau block. Similar structures have been observed elsewhere in the KSZ where they could be related to movement on the Ivanhoe Lake fault zone (see below; Bursnall 1989). The latest-Archean to Proterozoic deformation phases Younger deformation within the KU encompasses a protracted period from the latest Archean to the Middle Proterozoic and includes the uplift phases of the KU. Dominant structures in this period are brittle and include faults that defined the tectonic blocks described above. Overprinting and, in some areas, total destruction of high-grade fabrics in the vicinity of these faults is common. For example, Archean structures have been obliterated by extreme cataclasis and brittle faulting against the Nansen Creek, Saganash Lake, and Ivanhoe Lake faults (Leclair 1992; Bursnall 1990; Percival 1981a), and a 4 krn wide zone of cataclasis and pseudotachylite veins lies to the east of the Foxville fault (Percival 1985). A similar broad zone of complex brittle-ductile to brittle faulting marks the continuation of the Ivanhoe Lake fault zone to the south, the "Ivanhoe Lake cataclastic zone" (cf. Percival 1981a; Bursnall 1989). The presence of pseudotachylite in many of these zones suggests rapid displacements at relatively shallow depths (Sibson 1975, 1977), indicating significant uplift of the KSZ to depths appropriate for brittle deformation. That the bulk of the uplift was entirely restricted to thrust transport on the predominantly brittle Ivanhoe Lake fault is now in question; aeromagnetic interpretations have demon-

strated significant post-Matachewan strike-slip displacement of the KSZ (West and Ernst 1991). Definitive field-based evidence for either model has not been identified (Bursnall 1989). Mafic rocks within the Ivanhoe Lake fault zone southwest of Ivanhoe Lake contain a well-developed northwest-plunging mineral lineation and southeast-verging folds, which are cut by late, small-scale northwest-dipping brittle thrusts; these occur in fine-grained mafic to felsic rocks that locally contain lenses of coarser material from which they may have been derived (Bursnall 1989). In this area, therefore, it is possible that relict southeast-directed ductile thrust-uplift fabrics are present. The younger steep faults of the Ivanhoe Lake fault zone that cut these structures may have been generated during Proterozoic transcurrent displacement (Bursnall 1987). The trend of layering and prominent fabric within the KSZ varies from highly discordant (east -west) to subparallel to the trace of the Ivanhoe Lake fault zone. At local and regional scale within the Chapleau block (Figs. 3, 5), mild deflection, where layering is at a high angle to the fault zone trace, suggests some component of sinistral offset, particularly where the trend of the fault zone is north-northeasterly. The southern segment of the Ivanhoe Lake fault zone contains two distinct fault orientations in a zone where the trace of the fault swings from its prominent north-northeast direction to east-northeast (Figs. 3, 5). The more easterly fault trend, which is parallel to a strong subhorizontal stretching lineation, offsets the north-northeast segment dextrally. Progressive ductile to brittle transition (e.g., from thin mylonitic seams through cataclasite veins to fault breccias) is exhibited by the sequential development of structures at many localities within the Ivanhoe lake fault zone and may be viewed as responses to the progressive uplift and unroofing of the KSZ plate. In a few localities, however, mylonites postdate brittle structures (Bursnall and Moser 1989; Percival et al. 1991). Variations in uplift rate could explain the local transition from brittle to ductile behavior and could also explain many of the complexities present within the fault zone. Low-amplitude dome-and-basin interference patterns southwest of Ivanhoe Lake result from the intersection of two upright fold sets and are considered likely related to movement on the Ivanhoe Lake fault zone (Bursnall 1990). One of these produces slight deviations in regional strike along northwesterlytrending axes as the fault zone is approached and may be equivalent to similar folds elsewhere (e.g., WGDD5). A second set of northeast-trending, upright and gently plunging folds occurs close to Ivanhoe Lake, deforms cataclasites and mylonitic seams of the Ivanhoe Lake fault zone (Bursnall 1990). The Ivanhoe Lake fault zone therefore exhibits a complex polyphase deformation history. That this was protracted for both this zone and for other terrane-bounding faults has been inferred through several isotopic data sets (see Buchan and Ernst 1994; Hanes et al. 1994; Krogh and Moser 1994; Percival and Peterman 1994). Isotopic studies and other criteria indicate significant cooling around 2500 Ma; an early uplift event is implied (see below; Krogh and Moser 1994; Hanes et al. 1994), but its significance in the total uplift history is unclear. Recent studies suggest that it is likely that the main uplift event occurred in the post-Matachewan period (Percival et al. 1994; Percival and Peterman 1994). In general, the major faults affect diabase dykes of the

FIG.5. Lithological compilation map of the Kapuskasing uplift and adjacent areas. Compiled by J.T. Bursnall from Riccio (1979), Percival (1981b), Bursnall (1990), Ayer and Puumala (1991), Percival et al. (1991), Leclair (1992), and Moser (1993, 1994).

gneiss

1


CAN. I. EARTH SCI. VOL. 31, 1994

Preissac (Leclair and Nagerl 1988) and Kapuskasing swarms (Percival and Card 1985), dated, respectively, at 2140 f 40 Ma (Hanes and York 1979) and 2040 Ma (Hanes et al. 1986). The Kapuskasing dykes have been reoriented by uplift structures (Percival 1981a) and locally are invaded by pseudotachylite. Significant movement on the Lepage fault prior to intrusion of carbonatite at 1888 Ma was followed by mild reactivation (Buchan and Ernst 1994). Mylonites within the Ivanhoe Lake cataclastic zone have produced 40Ar/39Ardates of 1.96 and 1.72 Ga (Percival 1981a; Hanes et al. 1994) and a model based on isobaric cooling followed by rapid uplift suggests a 1.95 Ga age for the lower bracket to the main uplift event (Parrish 1987; Percival et al. 1988; Percival and Peterman 1994). 40Ar/39Ar dating by Hanes et al. (1994) indicates that deformation within the KU continued well into the Middle to Late Proterozoic. Hanes et al. argue that uplift must have been initiated at or closely following 2.5 Ga based on closure ages of amphibole within the Chapleau block close to the Ivanhoe Lake fault zone and coincident 2.4-2.45 Ga ages for biotite. A set of 2.25 -2.3 Ga ages in the vicinity of the Ivanhoe Lake, Wakusimi, Saganash Lake, and the Budd Lake (Hanes et al. 1994) faults either indicates hydrothermal overprinting, reactivation of earlier faults, or the age of the main uplift event (Hanes et al. 1994). Southwest of Ivanhoe Lake, lamprophyre dykes belonging to an extensive 1.14 Ga swarm (Hanes et al. 1991) contain a coarse fracture cleavage indicating that deformation continued into the Middle Proterozoic.


-

-

Discussion The earliest recognized deformation structures at the ddlower depths of the Wawa gneiss domain PmDI -w'JDD2) and Val Rita blocks kYRD2;), comprising early p i s sosity and east-west upright folds and predating -2580 Ma, may be equivalent. It is fso apparent that W G D Q -WGD& can be correlated with similar structures within the Michipicoten supracrustal belt. How far equivalent smctures can be traced eastwards to deeper crustal levels ia, however, uncertain. The post-2667 Ma B o h n Lake maconglomerate md, perhap, the whole supracrustal belt, however. must have been jutapsed against the. contiguous mid- to deep-crustal mks following the early deformation within the Wawa gneiss domain md adjacent Michipicoten belt. The relationship of tbe earliest deformation phases {Dl-D3 in the Wawa gneiss domain to those within the Borden b k e s ~ r u s &belt d is therefore unclmr and their quivdence cannot be demonstrated. If the Borden Lake belt is alloch~onms,it was emplaced prior to BLD3and Wq3, the earliest structures that can be codidently demonstrated to affect botb t e m e s (Moser 1%). These are younger than 2667 Ma (the maximum age of &psilion for the metamnglomerate;Kmgh 1993) and may be 2661 Ma in age (Moser 19941, implying that juxtaposition of this supmmtd belt and the surromdhg g n e i m had m u r e d by fbat time. The Barden Lake Wt, including tfie mtacongIomerate, was therefore finally assembled short2y before being affected by high-grade metamorphism at 2660 Ma (possibly younger at deeper crustal level8 in the KSZ;see Mow). The tectonic relationship htwcm movement on the Puskuta Lake shear zone and its postulated correlatives &eclair et al. 1993) and the rapid burial of the Borden h k e belt, which may k closely

-

related in time, is currently not known. Models for the emplacement of these supracrustal rocks and the progressive assembly of the KU are given elsewhere (Moser 1994; Krogh and Moser 1994). Strong evidence exists to suggest that the locus of deformation within the KU migrated southeastwards with time, from tonalites within the Wawa gneiss domain to the high-grade rocks of the KSZ, corresponding to progressively deeper crustal levels. The arnphibolite -granulite transition is discordant to lithological contacts in the central KSZ and high-grade metamorphism appears to be younger at greater structural depth (2660 to 2640 Ma within mafic gneiss; Krogh 1993). If these U -Pb zircon ages from the eastern Chapleau block date the deformational fabric, then the (earliest recognized) fabrics are significantly younger than those in the Wawa gneiss domain and Val Rita block. It is possible, however, that compositional layering in the KSZ localities may be a relict of primary layering (Percival 198la), which could have been deformed prior to metamorphism and therefore these dates do not necessarily record the earliest deformation (CBDI).Subsequent CBD3 folding affects this composite fabric, and boudinage-related leucosome has been dated at 2630 Ma (Krogh 1993). A zircon age of 2627 Ma on foliation-parallel leucosome in adjacent paragneiss and pegmatite in pull-apart structures in nearby mafic granulite dated at 2601 and 2586 Ma (Krogh 1993) further demonstrates that thermal and tectonic activity continued for a significant period in the eastern Chapleau block (Percival and Krogh 1983). Young extensional deformation may be more widespread, since extension within metaconglomerate at Borden Lake has been dated at 2603 Ma (Krogh 1993). Structural style varies significantly across the KU, from regionally steep fabrics in the west to the shallow-dipping structures in the eastern Wawa gneiss domain. The generally low dips in the high-grade parts of the domain and the Chapleau block are typically related to subhorizontal to low northerly-dipping shear zones. Such late D4 high-strain zones are more pervasive with depth and are a characteristic feature in the southeastern part of the Chapleau block, where they could be slightly younger than in the Wawa gneiss domain. This deformation (WGDD4 -CBD4) is, however, apparently the most extensive and consistent within the uplift and indicates that major regional deformation and reconstitution of the mid to lower crust occurred significantly later than polyphase deformation within the Michipicoten belt. The resulting broad zone of distributed shear effectively isolated the upper crust from significant deep-crustal deformation during this period. The precise nature of deformation in the latest Archean to earliest Proterozoic is not known but most authors suggest that it marks a period of early, pre-Matachewan uplift either along the Ivanhoe Lake fault zone or some precursor to it. It is possible that this initial stage of uplift was principally along a thrust surface in the position defined by the Lithoprobe highresolution survey and that the moderate to shallowly westplunging strong lineations that occur close to the Ivanhoe Lake fault zone are related to this event. Percival et al. (1994) and Percival and Peterrnan (1994) present evidence that implies that the pre-Matachewan event could have resulted in only a small part (0-8 km) of the total uplift of 35 km required by the paleopressure estimates. Subsequent uplift of (4 -7 km) occurred prior to 2.04 Ga Kapuskasing dyke emplacement, but the main uplift phase (10- 17 km) followed this at 1.9 Ga (Percival and Peterman 1994; Percival et al. 1994).

-

-

BURSNALL ET AL.


Discrete faults within the Ivanhoe Lake fault zone are typically steep and some indicate a component of strike-slip motion. Structures indicating low-angle reverse displacement are rare but do exist within some fault-bounded blocks within the zone and in one area clearly document a ductile to brittle progression. It is also apparent that brittle to ductile transition occurred locally and that deformation within the zone was both lengthy and complex, occurring in multiple stages from preMatachewan (-2.5 Ga) to post-1.14 Ga lamprophyre dyke intrusion.

Conclusions Relative structural history and geochronological evolution within the mid- to lower-crustal blocks of the KU indicate a complex interplay between plutonism, deformation, and metamorphism. Present levels of mapping and geochronological control, together with deformational diachroneity, have inhibited precise correlation of structures across this large region. Archean deformation appears to be younger at deeper levels. The earliest preserved, likely CBDI-CBD2 composite, fabrics at the deepest crustal levels could be 2660-2640 Ma, which 1is at least 20 Ma younger than the pre-2684 Ma WGDD WGDD2 fabrics in the western Wawa gneiss domain and the main regional deformation in the Val Rita block (likely pre269 1 Ma). Leucosome development (2627 Ma) and younger extension (at 2601 and 2586 Ma) also occurred at deeper crustal levels, further supporting the notion of continued tectonothermal activity with depth. Mid-crustal extension also occurred at 2603 Ma within metaconglomerate at Borden Lake. Rapid burial of the Borden Lake conglomerate (and, presumably, the associated supracrustal rocks) must have occurred in the period from 2667 to 2660 Ma. The earliest structures within this belt cannot be correlated with those in the surrounding tonalitic gneisses, and this, together with the 2667 Ma age of a cobble within the metaconglomerate, suggests that the belt might be allochthonous. Movement on the crustal-scale Puskuta Lake shear zone also may have occurred in this period, but the relationship between these two events is not known. The younger Archean deformation phases in the south and eastern part of the Kapuskasing uplift (D4 and younger) are seemingly the most consistent in age, regional extent, and deformational style. The large strains that developed from these occurred at mid-crustal and deeper levels in the period 2660 to post-2630 Ma, apparently beneath a passive suprastructure represented by the Michipicoten greenstone belt. Dextral displacement of the KSZ postdates Matachewan dykes, but precisely how much uplift was associated with this event is not clear. It is likely that dextral strike-slip motion followed limited earlier, pre-Matachewan, uplift (Percival et al. 1994), but structures related to this phase have not been defined. The greatest amount of uplift seems to have followed Kapuskasing dyke intrusion, but whether or not this was produced by thrust displacement has not been determined. Steep faults and related structures are characteristic of the Ivanhoe Lake fault zone and are predominantly brittle to brittle-ductile in character, with only local evidence for ductile deformation. In places, ductile shear zones postdate brittle shears, although the reverse is more common. Steep brittle faults cut gently to moderately west-dipping surfaces, defined both on the ground and by high-energy reflectors in the vicinity of Ivanhoe Lake and in the northern Groundhog River

-

-

1093

block area. Whether or not these low-dipping structures are a manifestation of regional, uplift-scale earlier thrusting is not clear. The Ivanhoe Lake fault zone was initiated prior to 2.45 Ga but continued displacements occurred as recently as 1.14 Ga, demonstrating a protracted polyphase deformation history for this important subprovince boundary.

-

Acknowledgments J.T.B. acknowledges support provided by a research fellowship at the University of Toronto and from J.A. Hanes' (Queen's University) phase 2 Kapuskasing Lithoprobe Natural Sciences and Engineering Council of Canada (NSERC) grant; we also appreciated the assistance of J.S. Street during the later stages of manuscript production, and thank R.E. Ernst and 0 . Ijewliw for the digital cartography of Fig. 5. D.M. acknowledges support from Hanes' Lithoprobe NSERC grant and from the Geological Survey of Canada. Fieldwork by A.D.L. was supported by the 1987- 1990 Canada-Ontario Mineral Development Agreement. Comments by K. Card, T. Kusky, and G. Stott are gratefully acknowledged. Ayer, J.A., and Puumala, M.A. 1991. Geology of Foleyet and Ivanhoe townships, Northern Swayze Greenstone Belt. In Summary of Field Work and Other Activities. Ontario Geological Survey, Miscellaneous Paper 157, pp. 263 -267. Bates, M.P., and Halls, H.C. 1991. Paleomagnetism of dykes from the Groundhog River Block, northern Ontario: implications for the uplift history of the Kapusaksing Structural Zone. Canadian Journal of Earth Sciences, 28: 1424- 1428. Bauer, R.L., and Bidwell, M.E. 1990. Contrasts in the response to dextral transpression across the Quetico -Wawa subprovince boundary in northeastern Minnesota. Canadian Journal of Earth Sciences, 27: 1521- 1535. Bennett, G., Brown, D.D., George, P.T., and Leahy, E.J. 1967. Operation Kapuskasing. Ontario Department of Mines, Miscellaneous Paper 10. Buchan, K.L., and Ernst, R.E. 1994. Onaping fault system: age constraints on deformation of the Kapuskasing structural zone and units underlying the Sudbury Structure. Canadian Journal of Earth Sciences, 31: 1197-1205. Burke, K., and Dewey, J.F. 1973. Plume-generated triple junctions: key indicators in applying plate tectonics to old rocks. Journal of Geology, 18: 406-433. Bursnall, J.T. 1987. Deformation sequence from the Kapuskasing structural zone, near Foleyet, Ontario. Geological Association of Canada, Program with Abstracts, 12: 27 Bursnall, J.T. 1989. Structural sequence from the southeastern part of the Kapuskasing structural zone in the vicinity of Ivanhoe Lake, Ontario. In Current research, part C. Geological Survey of Canada, Paper 89-lC, pp. 405 -41 1. Bursnall, J.T. 1990. Deformation sequence in the southeastern Kapuskasing structural zone, Ivanhoe Lake, Canada. In Exposed cross-sections of the continental crust. Edited by M.H. Salisbury and D.M. Fountain. Kluwer, Dordrecht, pp. 469 -484. Bursnall, J.T., and Moser, D. 1989. Site survey for continental drilling in the Kapuskasing Structural Zone. In Summary of field work and other activities. Edited by A.C. Colvine, M.E. Cherry, 0. Dressler, O.L. White, R.B. Barlow, and C. Riddle. Ontario Geological Survey, Miscellaneous Paper 146, pp. 16-21. Bursnall, J.T., Hodgson, C.J., Hubert, C., Kerrich, R.W., Marquis, P., Murphy, J.B., Osmani, I., Poulsen, H., Robert, F., SanbornBarrie, M., Stott, G., and Williams, H. R. 1989. Mineralization and shear zones. Edited by J.T. Bursnall. Geological Association of Canada, Short Course Notes No. 6. Cameron, E.M. 1989. Scouring of gold from the lower crust. Geology, 17: 26-29.


1094

CAN. I. EARTH SCI. VOL. 31, 1994

Card, K.D. 1990. A review of the Superior province of the Canadian Shield, a product of Archean accretion. Precambrian Research, 48: 99- 156. Card, K.D., and Ciesielski, A. 1986. Subdivisions of the Superior Province of the Canadian Shield. Geoscience Canada, 13: 5 - 13. Colvine, A.C., Fyon, J.A., Heather, K.B., Marmont, S., Smith, P. M., and Troop, D.G. 1988. Archean lode gold deposits in Ontario. Ontario Geological Survey, Miscellaneous Paper 139. Cook, F.A. 1985. Geometry of the Kapuskasing structure from a Lithoprobe pilot reflection survey; Geology, 13: 368 -371. Corfu, F., and Sage, R.P. 1992. U-Pb age constraints for deposition of clastic metasedimentary rocks and late-tectonic plutonism, Michipicoten Belt, Superior Province. Canadian Journal of Earth Sciences, 29: 1640- 1651. Flinn, D. 1962. On folding during three-dimensional progressive deformation. Quarterly Journal of the Geological Society of London, 118: 385 -433. Fountain, D.M., and Salisbury, M.H. 1981. Exposed cross sections through the continental crust: Implications for crustal structure, petrology and evolution. Earth and Planetary Science Letters, 56: 263-277. Frarey, M.J., and Krogh, T.E. 1986. U-Pb zircon ages of late internal plutons of the Abitibi and eastern Wawa subprovinces, Ontario and Quebec. Geological Survey of Canada, Paper 86-lA, pp. 43-48. Garland, G.D. 1950. Interpretation of gravimetric and magnetic anomalies on traverses in the Canadian Shield in Northern Ontario. Publications of the Dominion Observatory (Ottawa), No. 16. Geis, W.T., Cook, F.A., Green, A.G., Milkereit, B., Percival, J. A., and West, G.F. 1990. Thin thrust sheet forming Kapuskasing structural zone revealed by Lithoprobe reflection data. Geology, 18: 513-516. Goodings, C .R., and Brookfield, M.E. 1992. Proterozoic transcurrent movements along the Kapuskasing lineament (Superior Province, Canada) and their relation to surrounding structures. Earth Science Reviews, 32: 147- 185. Green, A.G., Mayrand, L.J., Milkereit, B., Ludden, J.N., Hubert, C., Jackson, S.L., Sutcliffe, R.H., West, G.F., Verpaelst, P., and Simard, A. 1990. Deep structure of an Archean greenstone terrane. Nature (London), 344: 327 -330. Hanes, J.A., and York, D. 1979. A detailed 40Ar/39Arage study of an Abitibi dike from the Canadian Superior Province. Canadian Journal of Earth Sciences, 16: 1060- 1070. Hanes, J.A., Archibald, D.A., and Lee, J.K.W. 1986. Reconnaissance 40Ar/39Argeochronology of Kapuskasing, Matachewan, and Hearst diabase dykes in the Kapuskasing Structural Zone and adjacent Abitibi and Wawa greenstone belts. Geological Association of Canada, Program with Abstracts, 11: 77. Hanes, J.A., Archibald, D.A., Queen, M., and Lee, J.K.W. 1991. Summary of the 40Ar/39Argeochronology in the Kapuskasing uplift and Abitibi greenstone belt. In Proceedings, Project Lithoprobe Kapuskasing Structural Zone, Workshop 111, Toronto, Ont., pp. 9-14. Hanes, J.A., Archibald, D.A., Queen, M., and Farrar, E. 1994. Constraints from 40Ar/39~r geochronology on the tectonothermal history of the Kapuskasing uplift in the Canadian Superior Province. Canadian Journal of Earth Sciences, 31: 1146- 1171. Heaman, L.M. 1988. A precise U-Pb zircon age for for a Hearst dyke. Geological Association of Canada, Program with Abstracts, 13: A53. Heather, K.B, and Arias, Z.G. 1987. Geological setting of gold mineralization in the Goudreau-Lochalsh area, District of Algoma. In Summary of field work and other activities, 1987, Ontario Geological Survey. Edited by R.B. Barlow, M.E. Cherry, A .C. Colvine, B.O. Dressler, and O.L. White. Ontario Geological Survey, Miscellaneous Paper 137, pp. 155- 162. Hudleston, P.J., Schultz-Ela, D., and Southwick, D.L. 1988. Transpression in an Archean greenstone belt, northern Mimesota. Canadian Journal of Earth Sciences, 25: 1060- 1068.

Innes, M.J.S., Goodacre, A.K., Weber, J.R., and McConnell, R.K. 1967. Structural implications of the gravity field in Hudson Bay and vicinity. Canadian Journal of Earth Sciences, 4: 977 -993. Jackson, S.L., Sutcliffe, R., Ludden, J., Hubert, C., Green, A.G., Milkereit, B., Mayrand, L., West, G.F., and Verpaelst, P. 1990. Southern Abitibi greenstone belt: Archean crustal structure from seismic reflection profiles. Geology, 18: 1086- 1090. Krogh, T.E. 1993. High precision U-Pb ages for granulite metamorphism and deformation in the Archean Kapuskasing Structural Zone, Ontario: implications for structure and development of the lower crust. Earth and Planetary Science Letters, 119: 1- 18. Krogh, T.E., and Moser, D.E. 1994. U-Pb zircon and monazite ages from the Kapuskasing uplift: age constraints on deformation within the Ivanhoe Lake fault zone. Canadian Journal of Earth Sciences, 31: 1096-1103. Leclair, A.D. 1989. The third dimension of the central Kapuskasing uplift interpreted from geological and geophysical data. Geological Association of Canada, Program with Abstracts, 14: A102. Leclair, A.D. 1990. Puskuta Lake shear zone and Archean crustal structure in the central Kapuskasing uplift. In Current research, part C. Geological Survey of Canada, Paper 90-lC, pp. 197-206. Leclair, A.D. 1992. Geology of the Kapuskasing - Groundhog Missinaibi River area, Foleyet (42B, north-half) and Kapuskasing (42G, south-half) map-areas, northern Ontario. Geological Survey of Canada, Open File 25 15. Leclair, A.D., and Nagerl, P. 1988. Geology of the Chapleau, Groundhog River and Val Rita blocks, Kapuskasing area, Ontario. In Current research, part C. Geological Survey of Canada, Paper 88-lC, pp. 83-91. Leclair, A.D., and Poirier, G.G. 1989. The Kapuskasing uplift in the Kapuskasing area, Ontario. In Current research, part C. Geological Survey of Canada, Paper 89-lC, pp. 225 -234. Leclair, A.D., and Sullivan, R.W. 1991. U-Pb zircon and titanite ages of upper and lower crustal rocks in the central Kapuskasing uplift, northern Ontario. In Radiogenic age and isotopic studies, report 4, Geological Survey of Canada, Paper 90-2, pp. 45-59. Leclair, A.D., Ernst, R.E., and Hattori, K. 1993. Crustal-scale auriferous shear zones in the central Superior province, Canada. Geology, 21: 399-402. Leclair, A.D., Percival, J.A., Green, A.G., Wu, J., West, G.F., and Wang, W. 1994. Seismic reflection profiles across the central Kapuskasing uplift. Canadian Journal of Earth Sciences, 31: 1016- 1026. MacLaren, A.S., Anderson, D.T., Fortescue, J.A.C., Gaucher, E.G., Hornbrook, E.H. W., and Skinner, R. 1968. A preliminary study of the Moose River belt, northern Ontario. Geological Survey of Canada, Paper 67-38. Moser, D. 1988. Structure of the Wawa gneiss terrane near Chapleau, Ontario. In Current research, part C. Geological Survey of Canada, Paper 88-lC, pp. 93-99. Moser, D. 1989. Mid-crustal structures of the Wawa gneiss terrane near Chapleau, Ontario. In Current research, part C. Geological Survey of Canada, Paper 89-lC, pp. 215 -224. Moser , D. 1993. A Geological, structural, and geochronological study of the central Wawa Gneiss Domain; implications for the development of different crustal levels of the Archean AbitibiWawa Orogen of the southern Superior Province, Canadian Shield. Ph.D. thesis, Queen's University, Kingston, Ont. Moser, D.E. 1994. The geology and structure of the mid-crustal Wawa gneiss domain: a key to understanding tectonic variation with depth and time in the late Archean Abitibi-Wawa orogen. Canadian Journal of Earth Sciences, 31: 1064- 1080. Parrish, R.R. 1987. Applications of numerical modeling of heat transfer to P -T -t path determination of exhumed mountain belts. Geological Association of Canada, Abstract 12, pp. 78. Percival, J.A. 1981a. Geological evolution of part of the central Superior Province based on relationships among the Abitibi and Wawa subprovinces and the Kapuskasing structural zone. Ph.D. thesis, Queen's University, Kingston, Ont.


BURSNALL ET AL.

Percival, J.A. 1981b. Geology of the Kapuskasing structural zone in the Chapleau -Foleyet area. Geological Survey of Canada, Open File Map 763. Percival, J.A. 1983. High-grade metamorphism in the Chapleau Foleyet area, Ontario. American Mineralogist, 68: 667-686. Percival, J.A. 1985. The Kapuskasing structure in the Kapuskasing Fraserdale area, Ontario. In Current research, part A, Geological Survey of Canada, Paper 85-lA, pp. 1-5. Percival, J.A. 1986. A possible exposed Conrad discontinuity in the Kapuskasing Uplift, Ontario. In Reflection seismology: the continental crust. Edited by M. Barazangi and L. Brown. American Geophysical Union, Geodynamic Series, No. 14, pp. 135-141. Percival, J.A. 1989. A regional perspective of the Quetico metasedimentary belt, Superior Province, Canada. Canadian Journal of Earth Sciences, 26: 677-693. Percival, J.A. 1990. A field guide to the Kapuskasing Uplift, a cross section through the Archean Superior province. In Exposed crosssections of the continental crust. Edited by M.H. Salisbury and D.M. Fountain. Kluwer, Dordrecht, pp. 227 -283. Percival, J.A., and Card, K.D. 1983. Archean crust as revealed in the Kapuskasing uplift, Superior Province, Canada. Geology, 11: 323 - 326. Percival, J.A., and Card, K.D. 1985. Structure and evolution of Archean crust in central Superior Province, Canada. In Evolution of Archean supracrustal sequences. Edited by L.D. Ayres, P.C. Thurston, K.D. Card, and W. Weber. Geological Association of Canada, Special Paper 28, pp. 179- 192. Percival, J.A., and Krogh, T.E. 1983. U -Pb zircon geochronology of the Kapuskasing structural zone and vicinity in the ChapleauFoleyet area, Ontario. Canadian Journal of Earth Sciences, 20: 830 - 843. Percival, J.A., and McGrath, P.H. 1986. Crustal structure of the northern Kapuskasing uplift of Ontario: an integrated petrological geophysical study. Tectonics, 5: 553 -572. Percival, J.A., and Peterman, Z.E. 1994. Rb - Sr biotite and wholerock data from the Kapuskasing uplift and their bearing on the cooling and exhumation history. Canadian Journal of Earth Sciences, 31: 1172-1181. Percival. J.A.. and Williams. H.R. 1989. The late Archean Ouetico accretionary complex, superior province, Canada. ~ e o l o & ,17: 23-25. Percival, J.A., Parrish, R.R., Krogh, T.E., and Peterman, Z.E. 1988. When did the Kapuskasing zone come up? In Kapuskasing structural zone transect, Workshop I, pp. 43-47. Percival, J.A., Green, A.G., Milkereit, B., Cook, F.A., Geis, W., and West, G.F. 1989. Lithoprobe reflection profiles across deep continental crust exposed in the Kapuskasing uplift structure. Nature (London), 342: 416 -420. Percival, J.A., Bursnall, J.T., Moser, D.E., and Shaw, D.M. 1991. Site survey for the Canadian Continental Drilling Program's Pilot

1095

Project in the Kapuskasing Uplift. Ontario Geological Survey, Open File Report 5790. Percival, J.A., Palmer, H.C., and Barnett, R.L. 1994. Quantitative estimates of emplacement level of postmetamorphic mafic dykes and subsequent erosion magnitude in the southern Kapuskasing uplift. Canadian Journal of Earth Sciences, 31: 1218- 1226. Riccio, L. 1979. No. S3 Shawmere Anorthosite. In Summary of field work. Ontario Geological Survey, Miscellaneous Paper 90, pp. 100-102. Sandvik, P.O., and Erdosh, G. 1977. The geology of the Cargill phosphate deposit, northern Ontario. Canadian Institute of Mining and Metallurgy, Bulletin, 70, pp. 90-96. Sibson, R.H. 1975. Generation of pseudotachylite by ancient seismic faulting. Geophysical Journal of the Royal Astronomical Society, 43: 775-794. Sibson, R.H. 1977. Fault rocks and fault mechanisms. Journal of the Geological Society of London, 133: 191-213. Sullivan, R.W., and Leclair, A.D. 1992a. U-Pb zircon age of the mid-crustal tonalite gneiss in the central Kapuskasing uplift, northern Ontario. In Radiogenic age and isotopic studies, Report 6. Geological Survey of Canada, Paper 92-2, pp. 89-96. Sullivan, R.W., and Leclair, A.D. 19926. Age constraints on the Puskuta Lake shear zone from U-Pb dating of granitoid rocks, Kapuskasing uplift, northern Ontario. In Radiogenic age and isotopic studies: Report 6. Geological Survey of Canada, Paper 92-2, pp. 89-96. Thurston, P.C., Siragusa, G.M., and Sage, R.P. 1977. Geology of the Chapleau area, Districts of Algoma, Sudbury, and Cochrane. Ontario Division of Mines, Geoscience Report 157. Turek, A., Smith, P.E., and Van Schmus, W.R. 1982. Rb -Sr and U-Pb ages of volcanism and granite emplacement in the Michipicoten belt-Wawa, Ontario. Canadian Journal of Earth Sciences, 19: 1608- 1626. Watson, J. 1980. The origin and history of the Kapuskasing structural zone, Ontario, Canada. Canadian Journal of Earth Sciences, 17: 866 -875. West, G.F., and Ernst, R.E. 1991. Evidence from aeromagnetics on the configuration of Matachewan dykes and the tectonic evolution of the Kapuskasing Structural Zone, Ontario, Canada. Canadian Journal of Earth Sciences, 28: 1797 - 1811. Williams, H.R., Stott, G.M., Thurston, P.C., Sutcliffe, R.H., Bennett, G., Easton, R.M., and Armstrong, D.K. 1992. Tectonic evolution of Ontario: summary and synthesis. In Geology of Ontario. Ontario Geological Survey, Special Volume 4, Part 2, pp. 1255-1332. Wu, J., and Mereu, R. F. 1993. Crustal structure of the Kapuskasing uplift from LITHOPROBE near-verticallwide-angle seismic reflection data. Journal of Geophysical Research, B, 97: 17 441 - 17 453.

Structural correlation within the Kapuskasing uplift

Structural correlation within the Kapuskasing uplift

Suggest Documents

THE CORRELATION BETWEEN STRUCTURAL RELAXATION ...

Subsidence and uplift mechanisms within the South Caspian Basin ...

Uplift Infinity Preparatory - Uplift Education

Correlation between the structural and cathodoluminescence ...

Correlation between the spectroscopic and structural ...

Correlation between the Mechanical Properties and Structural ...

Correlation between the structural, morphological, optical, and ...

Uplift Infinity Preparatory - Uplift Education

Uplift Infinity Preparatory - Uplift Education

Uplift Infinity Preparatory - Uplift Education

Uplift Infinity Preparatory - Uplift Education

MONITORING STRUCTURAL CHANGES WITHIN THE WHOLESALE

structural data within the immune epitope database

1 Widespread denudation and uplift within a passive ...

Constraints on the nature of the Kapuskasing ...

The Ambassador - UpLift! Group

Detailed correlation and astronomical forcing within

The correlation energy functional within the GW-RPA approximation ...

Correlation between genetic polymorphisms within IL ...

Structural Correlation of Some Heterocyclic ... - Semantic Scholar

Qualitative correlation between structural chirality ... - OSA Publishing

Correlation between structural and functional connectivity impairment ...

Correlation between Optoelectronic and Structural Properties Epilayer ...

Correlation between Chemical Durability Behaviour and Structural ...