Geology of the Eastman-Orford Lake Area I

DP 007 GEOLOGY OF THE EASTMAN-ORFORD LAKE AREA I MINISTERE DE L'ENERGIE ET DES RESSOURCES DIRECTION GENERALE DE L' EXPLORATION GÉOLOGIQUE ET MINERALE J Î I GAOL O G Y DF EASTMAN-ORFORD LAKE AREA H.S. de Römer 1960 DP-7 II GEOLOGY OP THE EASTMAN—ORFORD LAKE AREA, QUEBEC by Henry, S. de Römer Ministère des Richesses [a Hes, Québec na • • 9r ID. No GM: July 1960 III TABLE OF CONTENTS Page INTRODUCTION 1 General Statement 1 Location and Means of Access 2 Field Work and Methods of Study 2 Acknowledgments 3 Previous Work 4 DESCRIPTION OF THE AREA 8 Settlement and Resources 8 Topography 8 Drainage 9 Glaciation 10 Depositional Features 10 Erosional Features 12 Ice Movement 12 Physiographic History 13 GENERAL GEOLOGY 15 General Statement 15 Bonsecours Group 16 General Statement 16 Distribution and Extent 17 Quartz-sericite-graphite Schist Division . 17 Table of Formations 18 Quartz-sericite-Schist Division 19 Quartz-sericite-albite-(chlorite) Schist . 20 Quartz-sericite-chlorite-(albite) Schist . 22 Chlorite Schist and Greenstone 23 Marble 27 Metamorphism 28 Bonsecours Quartzo-feldspathic Schists . 28 Bonsecours Chlorite Schist and Greenstone . 29 Quartz Veins 30 Thickness 31 Age and Correlation 32 Ottauquechee Formation 32 General Statement 32 Quartzite 33 Phyllite and Quartz-sericite-graphite Schist . 35 Thickness 36 Age and Correlation 36 N Page GENERAL GEOLOGY (Cont'd) Miller Pond Formation 37 General Statement 37 Greywacke-slate Division 39 Greywacke 39 Megascopic Description 39 Microscopic Features 40 Slate and Argillite 42 Greenstone 43 Schist Division 44 Distribution 44 Lithology 44 Structural Relations 46 Rhyolite Division 47 Distribution 47 Lithology 47 Spilitic Greenstone Division 49 Distribution 49 Macroscopic Description 49 Microscopic Features 5o Metamorphism 51 Miller Pond Quartz-sericite-chlorite Schist 51 Miller Pond Spilitic Greenstone 52 Metasomatic Dolomite 52 General Statement 52 Description 53 Origin 54 Thickness 55 Age and Correlation 55 Beauceville Formation 56 General Statement 56 Metabasalt 56 Macroscopic Description 56 Microscopic Features 57 Slate and Minor Quartzite 58 Structural Relations 59 Age and Correlation 60 Intrusive Rocks 61 General Statement 61 Serpentinized Peridotite 61 Pyroxenite 62 Gabbro 63 'Acidic Rock' 65 Quartz-Diorite- and Granite-Breccia 67 Lamprophyre Dikes 68 The Orford-Chagnon-Baldface Complex 70 Haythmic Banding 71 Large-scale Zoning 72 Origin of the 'Acidic Rock' 73 Sequence of Events 74 Age of Intrusion 75 Page STRUCTURAL GEOLOGY . .. 77 General Statement . .. .. 77 early and Late Structures 78 Major Structures 78 Folds 78 Faults 81 Joints 83 Tectonic Breccia 83 Minor Structural Features 85 Planar Features 85 Bedding 85 Schistosity S1 86 Late Axial Plen Cleavage S2 87 Linear Features 88 Lineation L 88 Boudinage 1 89 Lineation L 89 Minor Early Fo'ds 90 Minor Late Folds 91 Pattern of Movement 93 Origin of Early Folds 93 Origin of Late Folds 93 „, Plasticine Models 94 Relation Between Deformation and Regional Metamorphism . 95 Time of Deformation 98 HISTORICAL GEOLOGY 100 ECONOMIC GEOLOGY 104 General Statement 104 Copper 104 The Quebec Copper Mine 105 Recent Developments 105 Geological Setting 108 Ore Zones 108 The 'A' Zone 108 The 'B' Zone 109 The IC' Zone 110 The 'D' Zone 110 Structural Control and Wall Rock Alteration 110 Method of Mining 112 Production and Ore Reserves 113 Lots 6 and 7, Range I, Stukely Township • . 113 Lot 24, Range VII, Bolton Township (No. 1) . 114 Lot 25, Range VII, Bolton Township (No. 2) . 115 Lot 26, Range VII, Bolton Township (No. 3) . 115 Lot 27, Range VII, Bolton Township (No. 4) . 116 Lot 6, Range VIII, Bolton Township 117 Lot 2, Range IX, Bolton Township 118 Lot 27, Range VII, Potton Township (No. 5) . 118 Other Small Copper Occurrences 119 VI Page ECONOMIC GEOLOGY (Cont'd) Asbestos 120 Lots 9 & 10, Range VII, Bolton Township . • 120 Lot 22, Range VII, Bolton Township 120 Lot 6, Range VIII, Bolton Township 120 Lot 9, Range IX, Bolton Township 121 Lot 2, Range XI, Bolton Township 121 Other Small Asbestos Occurrences 121 Steatite 121 Magnetite and Hematite 122 Chromite 123 Pyrite and Pyrrhotite 123 Marble 124 Lot 6, Range I, Stukely Township 124 Lot 8, Range II, Stukely Township 125 Lots 3 & 4, Range XI, Bolton Township 126 Slate 126 Sand and Gravel 126 BIBLIOGRAPHY 128 APPENDIX i Figure 1 Location of the map-area ii Figure 2 Physiographic features of the St. Etienne area iii Figure 3 Albite and muscovite porphyroblasts in Bonsecours schists . iv Figure 4 ACF diagram of Bonsecours greenstones and phyllites v Figure 5 Successive stages in the igneous activity of the Orford-Chagnon- Baldface complex vi Figure 6 Block diagram of the St. Etienne-de- Bolton map-sheet vii Figure 7 Successive stages in the development of S2 viii Figure 8 Styles of early folds ix Figure 9 Late folds of Schistosity S1 Figure 10 Geological plan of the ' A' , ' B' , 'C' and 'D' zones at the Quebec Copper mine . xi Figure 11 Longitudinal section of ore zones at the Quebec Copper mine xii Figure 12 Cross-sections at the G,uebec Copper mine xiii Plate I A. Finely laminated Bonsecours quartz- sericite-albite-(chlorite) schist . xiv I B. Close-up view of a folded Bonsecours . xiv Plate IIA. Photomicrograph of a twinned albite porphyroblast xv IIB. Photomicrograph of muscovite flakes growing along S2 xv VII Page Plate III A. Photomicrograph showing well-developed S2 in quartz-sericite-chlorite-(albite) schist ..,xvi IIIB. Photomicrograph of a typical Miller Pond greywacke xvi Plate IVA. Close-up view of a Miller Pond amygdaloidal greenstone xvii IVB. Photomicrograph of antigorite in in dolomite..xvii Plate VA. Beauceville quartzite and slate . xviii VB. Close-up view of the 'acidic rock' . xviii Plate VIA. Photomicrograph of quartzo-feldspathic veinlets in gabbro xix VIB. Granite breccia xix Plate VIIA. Photomicrograph showing S1 and S2. xx VIIB. Tectonic breccia xx Plate VIIIA. Style of late folds xxi VIIIB. Crestal part of a late fold xxi Plate IXA. Crests of small early folds xxii IXB. Crinkles and S2 in Bonsecours schists.. xxii Plate XA. Bonsecours schists showing L and L2 ..xxiii XB. Segregational layering in Bonsecours schists xxiii Plate XIA. Plasticine model showing repetition of 'strata' xxiv XIB. Plasticine model of a late fold super- imposed on tightly squeezed early folds xxiv Table 1 Partial chemical analyses of schists, greywackes and slates of the Eastman- Orford-Lake area xxv Table 2 Chemical analyses, molecular propor- tions and ACF values of Bonsecours chlorite schists, phyllites and greenstones xxvi Table 3 Modes of Miller Pond greywackes . xxvii Table 4 Modes of Miller Pond greenstones . xxviii Table 5 Partial chemical analyses of bandes and massive rocks of the rhyolite division xxix Table 6 Partial chemical analyses of Miller Pond spilitic greenstones xxx Table 7 Partial chemical analysis of metasomatic dolomite xxx Table 8 Annual production at the Quebec Copper mine xxxi Table 9 Operating costs and profits at the Quebec Copper mine xxxii Map I Geological map of the Eastman-Orford Lake area Map II Structural map Map III Correlation map Map IV Geological map of the South Bolton area GEOLOGY OF THE EASTMAN-ORFORD LAkE AREA, QUEBEC INTRODUCTION General Statement In 1956 and 1957; the writer was directed by the Quebec Mineral Deposits Branch to undertake a detailed study of the structural relations and stratigraphy of the above area with the view to investigate possible exploitable mineral deposits. The Eastman-Orford Lake area lies within the southeastern portion of the'Appalachian physiographie province of Quebec. Its topographic Divisions include the Sutton Mountains in the west, flanked by the Eastern Quebec Uplands to the east. The area is underlain by a thick assemblage of intensely folded Bonsecours schists succeeded eastward by steeply dipping clastic rocks of the Ottauquechee, Miller Pond and Beauceville formations of Cambrian and.Ordovician age. Zoning of the intrusives, underlying Orford and Chagnon mountains, suggests differentiation in place through gravitative crystal settling. The structural features consist of the Sutton-Green Moun- tain anticlinorium and a profusion of minor structures. It is suggested that two contrasting sets of folds represent two stages of deformation, accompanied by corresponding early and late phases of metamorphism. The mineral occurrences of the area consist of copper and iron sulphides and other materialsof economic importance. The mineral deposits and mining operations of the Quebec Copper -2- Corporation are described in some detail. Location and Means of Access The Eastman-Orford Lake area lies in the southern part of the Eastern Townships, about 22 miles southwest of Sherbrooke. It comprises approximately 44 square miles arid is bounded by latitudes 45°15' and 45°20' and by longitudes 72°15' and 72°25'. The area includes about 32 square miles of the northern part of Bolton township in the county of Brome, 11 square miles of the southern part of Stukely township, Shefford county and about 1 square mile of Orford township, Sherbrooke county (Fig. 1) . The most important road serving the area is the Montreal- Sherbrooke Highway No. I. The Sherbrooke-Montreal line of the Canadian Pacific Railways crosses the northern part of the area, closely paralleling Highway No. I. In addition, an old North Stukely- Eastman Railway crosses the area from north to south and a network of good secondary gravel roads covers the district making the area easily accessible. ( .U14Ce ./>. Field Work and Methods of Study In the summers of 1956 and 1957, the writer completed two 5-minute quadrangles for the Quebec Department of Mines, the St. Etienne-de-Bolton and the Lake Orford map-sheets, respectively. In 1958, the writer spent part of the summer rechecking the structural data collected in previous summers. In addition, a small area, a few miles east of South Bolton, comprising about ten square miles, was mapped by the writer in late 1958.

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