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80 30© Ministry of Hon- James A- c. Auld Minister Natural n tlfn Dr. J. K. Reynolds Ponflero Deputy Minister Ontario

. ..- ... . -. ONTARIO GEOLOGICAL SURVEY PRELIMINARY MAP P. 2296 MARGINAL NOTES GEOPHYSICAL SERIES r*vi o 7T LOCATION: The area is bounded by Latitudes,460 20© and 470 52/ 30" N, BOUGUER GRAVITY AND and Longitude 790 W, the Ontario-Quebec border and Longitude 800 30© W, covering an area of approximately 14 875 km 2 . The village of Temaqami is GENERALIZED GEOLOGICAL MAP to approximately in the centre of the survey area. Access by motor vehicle in O the region is provided by various highways which are connected with numer O ous lumbering, mining, resource and recreation access roads. Excellent water access is by an extensive lake system and many rivers. Access to the remote areas is restricted to float-equipped fixed-wing aircraft and helicopter. TEMAGAMI - ENGLEHART

GRAVITY SURVEY: In a land gravity survey the following primary data are recorded at each station: the time of observation in Greenwich Mean Time AREA (GMT), the observed gravimeter scale value, the elevation of the station with reference to mean sea level and the grid coordinates. During the summer of 1977, a field party, utilizing fixed-wing and helicopter aircraft established DISTRICTS OF TIMISKAMING,NIPISSING AND SUDBURY 2808 gravity stations using four Lacoste-Romberg gravimeters, numbers G-28, G-294, G-329 and G-417. In addition, 945 gravity stations were establi Scale: 1:100000 shed during a previous survey in 1973. The average gravity station distribution 4 Miles over the entire area was approximately 1 station per 4 km 2 . Miles 1 1 2

The gravity observations were tied to control stations established by the Kilometres 1 O 6 Kilometres Earth Physics Branch, Ottawa, at North Bay, Marten River, Temagami, Latch l H H E ford and Cobalt. These stations form part of the National Gravity Network which is tied to the International Gravity Standardisation Net 1971. Both the survey stations and the control stations are marked on the gravity maps. The LOCATION MAP Scale: l: 1,584,000 or 1 inch to 25 miles NTS References: 31My3W,4,5,6W,12,13; 41P;i,8,9,16 Lacoste-Romberg meters which are relatively drift-free were read at control stations every day at the beginning and end of each traverse. The meters had ODM-GSC Aeromagnetic Maps: an average daily drift of about 0.035 mgals. 1" to 1 mile 1481G, 1482G, 1491G, 1492G.1505G, Elevations: Vertical control for most of the survey was provided by lake levels, 1506G 1493G,1494G,1503G,1504G, with gravity station elevations being recorded as secondary elevations l "to 4 miles 7075G, 7076G relative to lake levels. The elevation of lakes close to bench marks along high ways and railways (Geodetic Survey of Canada and Ontario Ministry of Trans Earth Physics Branch Gravity Map Series portation and Communications (MTC)) were established by precise levelling 1:500 000 No.84, No.134 from these bench marks. Other larger adjacent and interconnected lakes were levelled from these lakes. The elevations of certain other lakes and river systems were established using data from Ontario Hydro, Ontario Ministry of OMNR-OGS 1980 Natural Resources and Government of Canada dams. Lake levels for the re Parts of this publication may be quoted if credit is given and the material maining less accessable lakes and elevations for points on roads were determ is properly referenced. ined using Wallace and Tiernan altimeters in pair. Appropriate corrections for temperature and humidity variations were applied and elevation control was provided by occupying a point of known elevation at least once every one to two hours. Some bench marks on the 47 45 highways and railways were used as gravity stations and for altimetry control. MTC profiles of certain highways were used for altimetry control and gravity LEGEND station elevations. Horizontal Control: The gravity stations were established at identifiable sites PHANEROZOIC SUPERIOR AND SOUTHERN and were located on 1:36 000 and 1:50 000 scale air photographs. The CENOZOIC* PROVINCES station positions were then transferred onto NTS topographic maps (Scale QUATERNARY MIDDLE PRECAMBRIAN PLEISTOCENE AND RECENT 1:50 000) with a six degree grid superimposed. The gravity stations were REFERENCES NIPISSING DIABASE digitized with a precision of 40m. Sand, gravel, day, boulder till, 24 Unsubdivided. i. G Brfethofr swamp deposits. 24a Pyroxene gabbro, minor pyroxenite. ERRORS IN THE BOUGUER ANOMALIES: The accuracy of the final Bou Bennett, G. 24b Hornblende gabbro, metagabbro, JvNfrowave UNCONFORMITY amphibolite. guer anomaly values, which were reduced to the datum of the mean sea T978: Geology of the Northeast Temagami Area. District of Nipissing; ?4c Granophyre. level using a uniform crustal density of 2.67 g/cm 3 , is limited by the follow Ont. Geul. Surv., Report 163, 128p. Accompanied by Maps 2323 FELSIC INTRUSIVE ROCKS ing sources of error. and 2324, scale 1 inch to V?. mile, and Chart A. 23a A/Me granite, syenite, ant! grano phyre f. Elevation Errors: The principal source of error in a gravity survey comes from Card, K.D..and Lumbers, S.B. Limestone, dolostone, shale, sand ?3b Porphyritic quartz monzonite, and the uncertainty in elevation measurements using altimeters. In this area, the 977: Sudbury-Cobalt Sheet; Ontario Geological Survey, Map 2361, stone, conglomerate. granite elevations are accurate to within 0.3 m for 1172 gravity stations while 1871 Scale 1 inch to 4 miles. INTRUSIVE CONTACT gravity stations elevations are accurate to within 1 m. The remaining 710 Card, K.D., Mcilwaine, W.H., and Meyn, H.D. ALKALIC ROCK-CARBONATITE HURONIAN SUPERGROUP* gravity stations elevations are accurate to within 3 m. The average deviation COMPLEXES COBALT GROUP 1973: Geology of the Maple Mountain Area, Districts of Timiskaming, of the altimeter elevations calculated from independently repeated altimeter Nipissing, and Sudbury; Ontario Div. Mines, GR106, I33p. 44 Carbonatite, nepheline and alkalic BAR RIVER FORMATION measurements at numerous sites was approximately 2.5 m. This is equivalent syenites, associated mafic eirf ul Accompanied by Maps 2256, 2257, 2258,and 2259,scale 1 inch tramafic rocks, lamprophyre dikes, 22 Quartz sandstone©, hematittc silt to an error of about 0.4 mgal in the Bouguer anomalies. to 1 mile, and Map 2260, scale 1 inch to Va mile. and fenite. stone, and sandstone. UNCONFORMITY. INTRUSIVE CONTACT GORDON LAKE FORMATION Location Errors: Gravity station positions were located correctly to within Lovell, H.L., and Caine, T .W. 40 m. This imprecision is equivalent to errors of about 0.03 mgal in the uttsVill 1970: Lake Timiskaming Rift Valley; O.nt. Dept. Mines, MP39, 16p. SUPERIOR, SOUTHERN AND 21 Siltstone, argillite, sandstone. latitude correction. GRENVILLE PROVINCES Lovell, H.L., and Frey, E.D. LORRAIN FORMATION Terrain Correction Errors: The average elevation for all the gravity stations is 1976: Geology of the New Liskeard Area, District of Timiskaming; 20 Quartz sandstone, micaceous and 281 m (from mean sea level) with a standard deviation of 47 m. Terrain PRECAMBRIAN Ont. Div. Mines, GR144, 34p. Accompanied by Maps 2300 and aluminous quartz sandstone, corrections were not calculated since the relief of the area is relatively flat. LATE PRECAMBRIAN quartz-feldspar sandstone, and 2301, scale 1 inch Lo Va mile and Chart A. minor diaglomerate, and siltstone. It is estimated that the maximum error from irregular topography would not MAFIC INTRUSIVE ROCKS6 Lovell, H.L., and de Grijs, J.W. GOWGANDA FORMATION exceed 0.1 mgal. 43 Unsuhdivided. 1976: Lorrain Township, Southern Part, Concessions 1 to VI, District 43a Diabase, quartz diabase dikes, 19 Conglomerate, sandstone, si/lsione, Other Errors: An error arises due to the assumption of a linear gravimeter and argillite. of Timiskaming; Ontario Div. Mines, MP51, 16p. Accompanied 43b Olivine diabase tfrtes, drift between the control readings. This average error due to instrument drift by Chart A, scale 1 inch to V& mile. 43c Gabbro, norite, pyroxenite, perido HOUGH LAKE GROUP is approximatly 0.035 mgal. Observational errors arising from factors such tite sloe h s. 43d Partly serpentinite! peridotite and MISSISSAGI FORMATION as poor levelling of the gravimeter would not exceed 0.02 mgal. Lovell, H.L. minor olivine yabbm stocks. )5 Quartz-feldspar sandsioni© with 1977: Geology of the Englehart-Earlton Area, District of Timiskaming; minor siltstone, mgillitf, anil con INTRUSIVE CONTACT Error Summary: The resulting maximum expected error (defined as the Ont. Geol. Sun/., MP69, 16p. Accompanied by Map P.1249, glomerate. square root of the sum of the squares of the individual errors) in the Bouguer MAFIC INTRUSIVE ROCKS scale 1 inch to Va mile. GRENVILLE PROVINCE anomaly due to the above listed sources will be less than 0.45 mgal for any 6 Unsubdivided. gravity station. Lumbers, S.B. fo Gabbro, anorthosite gabbro, gab 1969: Tomiko Area, District of Nipissing; p.61 -64 in Summary of Field HIGH RANK REGIONAL METAMORPHISM broic anorthosite and metamor phosed equivalents. METAMORPHOSED MAFIC Work, 1969 by the Geological Branch, edited by E.G. Pye, 6b Metagabbro and porphyritic m&ta- ROCK DENSITIES: One thousand, four hundred and eighty three density INTRUSIVE ROCKS Ontario Dept. Mines, MP32, 70p. gabbro dikes, measurements were made on fresh rock samples collected from outcrops at 41 UnsuMifiderJ. UNCONFORMITY, INTRUSIVE CONTACT or near gravity station sites. The rock samples were soaked in water for about 1970: Tomiko Area, District of Nipissing; p.84-88 in Summary of Field JJa Metamorphosed diabase and gab one hour and agitated to remove air bubbles. The porosity and permeability bro, EARLY PRECAMBRIAN Work, 1970 by the Geological Branch, edited by E.G. Pye, 410 Metamorphosed ultramafic rocks. of the rock types in the area is low and therefore the measured densities FELSIC INTRUSIVE AND Ontario Dept. Mines and Northern Affairs, MP43, 96p. FELSIC INTRUSIVE ROCKS should approximate closely the field densities. The densities listed below are METAMORPHIC ROCKS T971a:River Valley Area, Districts of Sudbury and Nipissing; p.90-97 5 Unsubdivided granitic and migma- grouped to correspond to the geological compilation legend which accom 39 Quarts monzonite, minor granodio in Summary of Field Work, 1971 by the Geological Branch, edi titic rocks. panies this map. rite and derived gneisses. ^ ^ 5a Quartz monzonite, granite, grano ted by E.G. Pye, Ontario Dfipt. Mines and Northern Affairs. : ANORTHOSITE SUITE INTRUSIVE diorite, trondhjemite, syenite and MP49, 109p. ROCKSC minor pegmatite and aplite, 5b Predominantly miQmatitic metavof- 1J971 b:Geology of the North Bay Area, Districts of Nipissing and Parry- 38a Anorthosite, gabbroic anorthosite canics and metasedimentary rocks. SUMMARY OF DENSITY (g/cm3 ) MEASUREMENTS and derived gneisses. 5c Trondhjemite, granodiorite, and Sound; Ontario Dept. Mines and Northern Affairs, GR94, 104p. 38b Csbbroic anorthosite, anoithositic minor quartz monzonite and quartz Accompanied by Map 2216, scale 1 inch to 2 miles, gabbro, minor gabbro, diorite, and d for i le. Density ultramafic rocks and derived gneis 5d felsite, quartz and feldspar por Unit© 1978: Geology of the Grenville Front Tectonic Zone in Ontario, ses. phyry, trondhjemite, granodiorite, Rock Type* N Range 38c Tonalite, diorite, ancf derived p.347-361 in Toronto 78 Field Trips Guidebook edited by A.L. gneisses, INTRUSIVE CONTACT Sedimentary Rocks 45 35 2.46-2.76 2.65 0.064 Currie and W.O. Mackasey, Geological Association of Canada. 38ti Pink and green monzonitic rocks, MAFIC AND ULTRAMAFIC 361 p. sodic arid alkalic syenites, quartz INTRUSIVE ROCKS [Paleozoic) McKenzie syenite, minor quartz monzonite, 4 Unsubdivided. Mcilwaine, W.H. and derived gneisses. Mafic Intrusions 43 18 2.84-3.14 2.96+0.092 38s Quartz monzonite, minor quartz 4a Quartz diorite, diorite, gabbro. 1970: Geology of South Lorrain Township, District of Timiskaming; syenite, and derived gneisses, 4b Pyroxenite, peridotite, dunite, ser Mafic Intrusions I 3.07 pentinite, Ont. Dept. Mines and Northern Affairs, GR83, 95p. Accompan 4c Lamprophyre, carbonatite dikes and Felsic Intrusions 28 2.59-2.79 2.66 0.041 ied by Map 2194, scale 1 inch to Va mile, and 2 charts. MIDDLE AND LATE intrusive breccia k. PRECAMBRIAN INTRUSIVE CONTACT Anorthosite Suite 6 2.74-3.05 2.86 0.120 Meyn, H.D. MAFIC AND ULTRAMAFIC METASEOIMENTS Intrusions 1,977: Geology of Afton, Scholes, Macbeth, and Clement Townships, INTRUSIVE ROCKS*: Districts of Sudbury and Nipissing; Ont. Geol. Surv., Report 3 Greywacke, siltstone, chert, and Mafic Intrusions 37 1 3.02 37 Uiisubdisided. arkose with minor me/a ve©ran/c 170, 77u. Accompanied by Maps 2335 and 2386, scale 1 inch 37rt Gneissic gabbro, diorite, and am rocks, and derived migmatite!,. enaelss phibolite. Felsic Intrusions 36 22 2.58-2.75 2.67+0.041 METAVOLCANICS to J4 mile. 37b Metamorphosed ultramafic intru FELSIC TO INTERMEDIATE Metasediments © 36 147 2.592.43 2.70+0.092 Pyke, D.R., Ayres, L.D., and Innes, D.G. sive rocks. 37c Gnsissic metagabbro probably METAVOLCANICS (Biotite Gneiss) 1973: Timmins-Kirkland Lake Sheet; Ontario Division of Mines, Map equivalent to Nipissing Diabase of 2 Unsubdivided. the Southern Province. 2.70-3.06 2205, Scale 1 inch to 4 miles. 2a Rhyolite, dacite flows with minor Metasediments 2 2.88 felsic^ intrusions and felsic pyro (Marble * Gneiss) Simony, P.S. MIDDLE PRECAMBRIAN clastics. 2b Felsic to intermediate pyroclastics Metasediments (Quartzo- 33 II 2.59-2.75 2.6510.052 1964: Geology of Northwestern Timagami Area, District of Nipissing; FELSIC INTRUSIVE ROCKS tuff, breccia, and agglomerate Feldspathic Gneiss) Ont. Dept. Mines, GR28, 30p. Accompanied by Map 2057,scale with minor flows, metasediment^ 36 Unsubdivided, in part gneissic and intrusive rocks, and derived 1 inch to ©/2 mile. equivalent of unit 28. Metasediments 32 73 2.60-2.99 2.71+0.063 36a Gneissic quartz monzonite end migmatttes. (Clastic Gneiss) minor granodiorite and granite. MAFIC TO INTERMEDIATE 3Sb Gneissic trondhjemite and grano METAVOLCANICS Felsic Intrusions 11 2:64-3.09 2.7U0.130 47V 30© - diorite. 1 Unsubdivided. INTRUSIVE CONTACT 1a Basalt and andesite Flows with Metasediments 30 1 2.72 minor malic pyroclastics and mafic METASEDIMENTS* intrusions. Granophyre (Nipissing) 24c 9 2.57-2.75 2.68+0.056 35 Biotite gneiss derij&j from grey Ib Interflow metasediments and mafic wacke, siltstone, immature sand- pyroclastics. Diabase (Nipissing) 24 246 2.72-3.18 2.96 0.068 stone and minor calcareous siltstone and sandstone. Bar River Formation 22 1 2.65 35a Biotite gneiss containing numerous IF iron formation and ferruginous thin teds of feldspathic gneiss chert (associated with units 3, 32, Lorrain Formation 20 .171 2.53-2.82 2.66+0.041 (33b), muscovitic and Quartzose 33, 34, 35). gneiss (33a) ancf sills and dikes o! Gowganda Formation 19 364 2.56-2.89 2.75+0.057 gneissic gabbro (37c). Mississagi Formation 15 7 2.61-2.75 2.69+0.045 34a Calcitic and dolomitic marble with minor irtterlayered calc-silicate Felsic Intrusions 5 170 2.55-2.82 2.69+0.061 gneiss. 34b Calc-silicate gneiss derived from Only the thickest, most extensive Cenozoic deposits Mafic 81 Ultramafic 4 23 2.76-3.23 2.92 0.120 calcareous sandstone and siltstone. in which bedrock outcrops are absent or scarce arc shown as coded, uncoloured areas. Intrusions 33 Unsubdivided Quartzo-ivid spathic gneiss. *Some may D& of Phanerozoic age. Metasediments 3 29 2,57-2.92 2.72+0.082 33d Muscovitic ana quartzose gneiss derived from orthoquartzite, subar "Multiple ages represented. Minor amounts of anor Felsic to Intermediate 2 67 2.62-2.85 2.74+0.049 kose, and aluminous claystone, thosite suite rocks occur in the Southern Province. Metavoicanics 33b Feldspathic gneiss derived from *Probabfy approximately equivalent in age to the arkose, subarkose, and ferruginous Huronian Supergroup. Intermediate to Mafic 54 2.69-3.21 2.91+0.091 arkose with minor interlayeredcalc- irstbrtfbk silicate gneiss (34b) and immature fProbably equivalent in age to Nipissing Diabase. Metavoicanics melasandstone. f*The Huronian rocks arc weakly to moderately meta Iron Formation t 3.50 32 Gneissic coarse clastic metasedi- morphosed, tint as original lithologicsi characteristics ments derived from pebbly to are generally welt preserved, sedimentary rock desig bouldery coarse-grain&d greywacke, nations are used, Note: N = number of samples: p = mean density, s ~-standard deviation immature sandstone, arkose, and minor conglomerate. *7oo small to be shown at map scale. *See Legend for further description EARLY PRECAMBRIAN FELSIC INTRUSIVE ROCKS GENERAL GEOLOGY: The geology of much of the area included in the pre sent survey has been described by Lumbers (1969; 1970; 1971a; 1971b; Bale 3ta Gneissic quartz monzonite and minor gneissic granodiorite. 1978), Card e t al. (1973), Bennett (1978), Meyn (1977), Lovell (1977), "" \ Joannes 31!) Gneissic trondhjemite, granodiorite, This Geological Legend is modified from OGS Lovell and de Grijs (1976}, Lovell and Frey (1976), Lovell and Caine (1970), and miner quartz monzonite. Map 2361, Sudbury-Cobalt Sheet, Geological Mcilwaine (1970) and Simony (1964). The Sudbury-Cobalt (Card and METASEDIMENTS Compilation Series. Lumbers 1977) and Timmins-Kirkland Lake (Pyke ei al. 1973} compilation Note: Not all faults shown and subdivision of 30 Gneissic equivalent o! unit J. maps show most geological details. Maple Mountain certain units omitted for simplification.

FAULT CONTACT General Setting: The area is underlain by Precambrian rocks of the Superior, 39 l Southern and Grenville Provinces of the Canadian Shield and is traversed by Fire Locraout the Grenville Front Tectonic Zone. This is a zone of faulting, constriction and cataclasis that separates highly deformed and metamorphosed Middle and Late Precambrian rocks of the Grenville Province to the southeast from rela tively little deformed and metamorphosed Middle Precambrian rocks of the Portage Southern Province and Early Precambrian rocks of the Superior Province to SYMBOLS the northwest. In addition there is an outlier of Paleozoic rocks. Superior Province: Early Precambrian metavolcanics and associated meta sediment are the oldest rocks in the area. They consist of isoclinally folded Gravity station (Ontario Fault Geological Survey) mafic and felsic volcanic rocks, wacke, argillite, and minor iron formation regionally metamorphosed under greenschist facies conditions. A variety of metagabbros, metadiorites and felsic porphyries intrude the metavolcanics. Gravity station (Earth Geological boundary The surrounding granitic batholiths are mainly trondhjemite to quartz mon Physics Branch, Ottawa) zonite in composition, and are intrusive into the metavolcanics which were contact metamorphosed under albite-epidote and hornblende-hornfels facies Gravity control station Gierwille Front boundary conditions. The rocks are cut by Middle Precambrian Nipissing Diabase dikes fault and sills and by Late Precambrian olivine diabase dikes.

Southern Province: Metasediment5 of the Middle Precambrian Huronian Contours of equal Bouguer anomalies Supergroup comprise part of the Cobalt Plate of the Southern Province and at intervals of 20 Gravity Units were deposited unconformably on the Early Precambrian. The Gowganda (20G.U. - 2 miltigais) Formation consists of greywackes, siltstones, varved argillites, and conglo merate and is overlain conformably by the Lorrain Formation, which consists of massive feldspathic quartzite and arkose. The rocks of the Cobalt Group Gravity high are generally flat-lying except near the Grenville Front Tectonic Zone where they are folded and metamorphosed. The rocks are cut by Middle Precambrian Gravity low Nipissing Diabase and Late Precambrian olivine diabase dikes. und Chute Grenville Province:The Grenville Front Tectonic Zone, a zone of constriction, Observed gravity data is based on the National Gravity Net which is cataclasis and faulting up to 16 km wide trends northeast with a northeast consistent with the International Gravity Standardization Net 1971 foliation and southwest-plunging rodding lineation. The Grenville Front (IGSN 71). Theoretical gravity values are computed using the Geodetic Boundary Fault, a zone of crushed and mylonitized rocks up to 60 m wide, Reference System 1967 (GRS 67). Boutjuer anomalies have been calcu marks the only mappable northwestern boundry of the Grenville Front amssites lated assuming a vertical yrav*ty gradient of 0.3086 mgalVm and a Tectonic Zone, but granulation and mylonitization effects extend up to 5 km Mir crustal density of 2.67 g/cm 3 . northwest of the zone into the Early and Middle Precambrian rocks. An Early * 1 mgal = 10"5 m.;Sec2 Precambrian trondhjemite batholith of Superior Province extends up to 6 km into the Grenville Province, where it, together with inclusions and screens of greywacke, has been regionally metamorphosed to the same high rank as other rocks of the metamorphic complex and is unconformably overlain by a sequence of coarse-grained clastic siliceous metasediments, i.e., coarse-grained arkosic sandstone, coarse-grained pebbly sandstone, and minor finer grained sandstone and siltstone. The main coarse-grained clastic unit forms the base SOURCES OF INFORMATION of the metasedimentary accumulation dominating the Grenville Province and this-accumulation is probably Middle Precambrian in age. Biotite gneiss, pro Gravity survey and compilation by V.K. Gupta, D.R. Wadge and Assist bably derived from greywacke and muddy siltstone, and feldspathic gneiss ants, 1977, 1978, 1979. probably derived from arkosic sandstone, are intercalated with the basal clastic sequence and increase in abundance towards the southeast. A sequence of Some information taken from files of J.A. McCance from work done in quartzose and muscovitic gneiss derived from well-sorted quartz-rich sand 1973 and 1974. stones containing intercalated shale and orthoquartzite underlies much of the Gravity data reduction at Gravity and Geodynamics Division, Earth eastern part of the area. Calc-silicate gneiss derived from calcareous shale and Physics Branch, Department of Energy, Mines and Resources, Ottawa, siltstone commonly is interlayered with the sandy metasediments. The meta sediments underwent partial anatexis during regional metamorphism with the Baid Canada, 1978. result that many are now migmatitic containing numerous discontinuous veins and lenses of granitic material. A variety of plutonic rocks, probably ranging I©Africai Geology from the following published maps of the Ontario Geological Survey: in age from Middle to Late Precambrian, were emplaced within the metasedi ments of the Grenville Province before the high-rank regional metamorphism OGS Map 2316 Card St Lumbers 1977 1" to 4 miles Sudbury-Cobalt and accompanying deformation ended and were themselves metamorphosed. Compilation Of the various plutonic rocks, gneissic felsic varieties forming stocks, sheets, ODM MP51 Chart A Lovell 81 de Grijs 1976 1" to ©A mile Lorrain Township and a few batholiths are the most abundant. A gneissic quartz monzonite (Southern Part) batholith is intrusive over a large area and extends to the margin of the Gren ville Front Tectonic Zone. The batholith was emplaced during the waning ODM Map 2205 Pyke era/. 1973 1" to 4 miles Timmins-Kirkland Lake stages of regional metamorphism. Dikes and sheets of gneissic anorthosite are Compilation intrusive into rocks of the batholith. A large anorthosite complex, extremely ODM Map P. 1249 Lovell 1977 1" to Vz mile Englehart-Earlton Area irregular in outline, is intrusive in the western portion of the area south of the ODM Map 2300 Lovell St Frey 1974 T©toVamile Kerns 8i Hudson Tps Grenville Front where it intruded metasediments of the Huronia Supergroup ODM Map 2301 Lovell St Frey 1974 1" to Vi mile Harley St Dymond Tps and Nipissing Diabase and associated granophyre. Most of the complex in the Grenville Province was recrystalized by the high-rank regional metamorphism Conversion factor: 1 mile = 1.609 km and is gneissic, but some parts of the eastern lobe are massive with primary Thievine Beqr ! mineralogy. That part of the complex extending across the Grenville Front is cataclastic, locally massive and was subjected to low grade metamorphism. Map base (Universal Transverse Mercator Projection) compiled from Following the high-rank regional metamorphism and plutonism the region National Topographic Series Sheets. was subjected to faulting during the Late Precambrian, and at least the Early Paleozoic. This map is published with the permission of E.G. Pye, Director, Ontario te- Geological Survey. Paleozoic: The rocks of the Paleozoic outlier occupy a fault-controlled, graben- style structure northwest of Lake Timiskaming. These limestones, doiostones, Marfel shales and sandstones are related to the Ordovician rocks of Lake Nipissing Issued 1980 and the Silurian rocks of the James Bay Lowlands and Manitoulin Island. Pleistocene; Pleistocene continental glaciation scoured and gouged the bed rock and left behind a thin, discontinuous mantte of ground moraine. Retreat of the continental glaciers resulted in the formation of end moraine, glacio Information from this publication may be quoted if credit is given. It is fluvial, and glaciolacustrine deposits of clay, sand and till. The Little Clay recommended that reference to this map be made in the following form: Belt, fertile agricultural soil laid down by Pleistocene glacial Lake Barlow-Ojib- Gupta, V.K., and Wadge, D.R. way, occupieG a broad valley controlled by Northwest-trending down-dropped 1980: Bouguer Gravity and Generalized Geological Map Temagarni- blocks centered on Lake Timiskaming. Recent deposits consist of alluvium Englehart Area, Districts of Timiskaming, Nipissing and and peat. Sudbury; Ontario Gftological Suivey, Prelim. Map P.2296, ECONOMIC GEOLOGY: The map-area contains one of the provinces oldest Geophys. Ser., Scale 1:100 000. Survey and compilation mining camps at Cobalt. Metals produced in 1977 were silver and cobalt in 1977, 1978,1979. the Cobalt area and iron ore at Temagami. Past producers of silver and cobalt are located in the Elk Lake, Cobalt and South Lorrain Township areas. Copper silver and gold were formerly mined at Lake Temagami and gold was produced at Emerald Lake. There are also numerous occurrences of silver, cobalt, gold, copper, nickel, lead, zinc, uranium, stone, feldspar, kyanite and vermiculite in the map-area.

PRESENTATION OF RESULTS: The map was compiled using a gridding and contouring program GPCP-II. The randomly spaced observed gravity data were interpolated to a 2 km grid-cell size. Some smoothing on the final Bouguer contours was also applied. The gravity data superimposed on general ized geology are presented on the Bouguer anomaly map at a scale of 1:100 000; the contour interval is 20 Gravity Units = 2 mgal . The principal facts of all gravity stations and descriptions of control station ©ocations are available from the Gravity and Geodynamics Division, Earth Physics Branch, Department of Energy, Mines and Resources, Ottawa, K1A- OY3. Obabika

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