QAIT-O'icH'L 58-40 PAPER 68-40 S. M. ROSCOE 1969 Reprintod 1976 GEOLOGICAL SURVEY OF CANADA PAPER 68-40 HURONIAN ROCKS AND URANIFEROUS CONGLOMERATES S.M. Roscoe DEPARTMENT OF ENERGY, MINES AND RESOURCES CANADA & Minister of Supply and Sc>rvk-(;s C'iin;nl;i l'J7ti I'l-iming and Publishing Supply iind Si?i-viL-i-.s Cimada. Oltuwii. L'niiiiiJfi K1A OS!), from the (iuulfWictil Survuy t>[ Uiiiiiiiln fiUI Hooth St.. Ottawji. K1A 0K8 or through your \ 1'rico: Cumidu: S-i. ^ Ct, ..ii[fU(; No. M1-1-I.H-4U OIIKT counti-ios: H. n Pritrc: subjout to uhiin^G wilhout notice TABLE OF CONTENTS Page Abstract ix Introduction 1 Acknowledgments 2 Usage of the term Huronian' 4 General features of the Huronian succession 6 Lithology : 6 Arenites i 6 Conglomeratic greywacke 9 Fine-grained argillaceous rocks 9 Division of the Huronian succession into groups 9 Distribution and correlations of the Huronian rocks 15 General 15 Cobalt group 15 General 15 Gowganda Formation 18 Lorrain Formation 19 Gordon Lake Formation 19 Bar River Formation 20 Quirke Lake Group — Bruce, Espanola and Serpent Formations. 20 General 20 Thickness variations 21 Correlation problems northeast of Sudbury 22 Correlation problem north of Thessalon 23 Hough Lake Group - Ramsay Lake, Pecors, and Missassagi Formation , 24 General 24 Correlation problem in Sault Ste. Marie area 26 Ramsay Lake Formation 27 Pecors Formation 28 Mississagi Formation 29 Elliot Lake Group 31 General 31 Livingstone Creek Formation 31 Thessalon Formation 34 Pater Formation 35 Stobie Formation and probable correlative volcanic rocks .... 35 Copper Cliff Formation 39 Matinenda Formation 40 McKim Formation 49 Relationships between volcanic and sedimentary rocks 51 Pre-Huronian rocks 55 General 55 Archean metavolcanic and metasedimentary rocks 58 Whiskey Lake greenstone belt 58 Granitic rocks near Elliot Lake 61 Heavy accessory minerals 63 Page Thorium and uranium oxide contents 64 Distribution of radioactivity in granitic rocks 65 Influence of Archean basement rocks and topography on Matinenda sedimentation 65 General 65 Nordic area 66 Pardee area 66 Quirke Lake area , 67 Whiskey Lake area 67 Area west of Quirke Lake 68 Wanapitei area 69 Mount Lake area 69 Areas with granitic basement rocks 69 Residual deposits on the pre-Huronian surface 70 Mineralogy 70 Chemical variations 72 Significance 73 Discussion of special characteristics of Huronian rocks 75 Possible glacial origin of conglomeratic grevwacke units 75 Gowganda Formation 75 Ramsay Lake Formation 77 Bruce Formation 78 Significance of association of oZigomictic conglomerates with tilloids 79 Anoxic character of Huronian rocks 80 Lack of red beds in pre- cobalt rocks 80 Colours of rock clasts 81 Comparison of pyritic and hematitic conglomerates 82 Concepts of evolution of the earth's atmosphere 83 Diagenesis, regional metamorphism and rnetasomatic alteration ... 85 General 85 Discuision of diagenetic and metamorphic processes 86 I o-depositional alteration 86 Diagenesis 86 Deep diagenesis 87 Distinction between diagenesis and metamorphism 87 Disequilibrium assemblages of detrital minerals in Huronian rocks 88 Preservation of sedimentary textures 90 Secondary mineral cement 90 Argillaceous constituents 91 Incipient recrystallizations 92 Cataclasis 92 Dynamically and thermally metamorphosed rocks 93 Contact metamorphic rocks 94 Metasomatically altered rocks 94 General 94 Page Deleterious effects of altered ores on milling operations 95 Albitization 96 Chloritization 97 Intrusiva rocks 99 Gabbro 99 General 99 Nipissing diabase 100 Associated mineral deposits 101 Granitic rocks 103 Cutler granite 103 Murray-Creighton granite 103 Croker Island complex 105 Wavy Lake granite 105 Mongowin ultrabasic body 105 Lamprophyre dvkes 105 Grenville rocks 1 07 Structure 108 Folds 108 Faults 108 Classification . 108 Murray Fault 108 Flack Lake Fault 109 Northwesterly and northeasterly trending faults 109 North-northeasterly trending faults 109 Gently-dipping reverse faults 109 Relationship of faulting to Huronian sedimentation 110 Comparison of Huronian and other Aphebian rocks Ill General Ill Relationships between Huronian and Animikie rocks 113 Whitewater Group 113 Mlstassini region 115 Metaquartzite in the Grenville Province east o[ Lake Temiskaming 117 Wakeham Group 118 Continental clastic sediments in northern Quebec 118 Aphebian rocks west of Hudson Bay 119 Radioactive quartz-pebble conglomerates 1 20 Introduction , 1 20 Distribution 120 Character of ore zones 121 Pronto zone 121 Nordic zone 1 22 Quirke zone 123 Mineralogy 125 Minerals present 125 Pyrite 128 Uraninite 129 Page Titania- rich grains or aggregates 136 Monazite J 39 Zircon 1 39 Thucholite 139 Chemical-mineralogical classification 139 Mineralogical zonations 143 Isotopicage of lead in radioactive and non- radioactive minerals 1 46 General 146 Significance of variations in isotopic compositions of leads. , J 47 Lead contents of conglomerate ores 149 Apparent isotopic ages of radioactive minerals 1 51 Isotopic composition of leads in non-radioactive minerals. ... 153 Discussion 1 58 Discussion of genesis 159 General 159 Theories of epigenetic origin 159 Weaknesses in the concept of permeability control 161 Comparison of conglomeratic deposits with known epigenetic deposits 163 Credibility of the placer hypothesis 165 Exploration possibilities ] 66 General 166 Huronian belt 168 Bibliography 1 72 Appendix Table A: Analyses of selected rocks, Elliot Lake area 195 Table B: Partial analyses of radioactive conglomerates and conglomeratic quartzites 1 96 Table C: Gold contents of some ores, conglomerates and associated radioactive rocks 1 99 Index 200 Table I Huronian Formations 8 II Quirke Lake Group at Quirke Lake 20 III Equivalent formational names. Hough Lake Group. 25 IV Formations in the Elliot Lake Group 32 V Minor elements and isotopic composition of sulphur in sulphides 1 30 VI Partial analyses of uraninites 1 34 VII Chemical* classification and partial analyses of pyritic quartz-pebble conglomerates 141 VIII Ratios of concentration of diagnostic elements 145 IX Isotopic analyses of leads in radioactive minerals. 152 X Isotopic compositions of leads in non-radioactive minerals 1 57 XI Comparison of sandstone-type and conglomeratic- type uranium deposits 1 64 Illustrations Page Plate I Matinenda subarkose 6 II Conglomeratic greywacke, Bruce and Ramsay Lake Formations 10 IIIA. Pyriie grains in matrix of conglomerate, Lacnor Mine 126 B. X- ray micrograph; base of pronto ore 126 IV Uraninite-rich layers in thin crossbedded subarkose lens, Quirke Mine 1 32 V Large composite grain of rutile-anatase-quartz- brannerite 1 37 Figure 1 Distribution and structure of Hurcnian rocks 14 2. Distribution ol Huroniari groups 16 3 Stratigraphy of Matinenda Formation near Elliot Lake 43 4 Relationships between distribution of thick grit zones in Matinenda Formation and structural uplifts during deposition 47 5 Schematic sections showing inferred stratigraphic relationships of volcanic rocks of the Stobie and Thessalon volcanic and sedimentary rocks of the Elliot Lake Group 52 6 Distribution of Archean rocks beneath Huronian strata and ore zones 56 7 Distribution of Aphebian rocks in the Canadian Shield 112 8 Relationships of the Whitewater Group to Huronian rocks in the Sudbury-Elliot Lake area 114 9 Aphebian strata in the Mistassini region, central Quebec 116 10 Lead: uranium isotopic ratios in ore minerals .... 153 11 Lead isotope ratios in radiogenic leads 1 54 12 Approximate depth or core distance to strata likely to contain radioactive quartz-pebble conglom- erate 169 ABSTRACT Uranium ore deposits of the Elliot Lake-Blind River area and other beds of radioactive, pyritic, quartz-pebble conglomerate near the north shore of Lake Huron, occur within greenish, very coarse grained, crossbedded, argillaceous, feldspathic quartzite in the Elliot Lake Group at the base of the Huronian Supergroup. Volcanics, formerly considered pre-Huronian, in the Espanola-Sudbury area east of Elliot Lake may be correlative with basalt that comprises much of the Elliot Lake Group to the west in the Thessalon- Sault Ste. Marie area. Overlying Huronian formations^ Hough Lake, Quirke Lake and Cobalt Groups, in ascending order, each contain conglomeratic greywacke of probable glacial origin overlain by argillaceous strata (including limy beds in the Quirke Lake Group) in turn overlain by subarkose. Sediment- ary strata totalling more than 30,000 feet in the southeastern part of the region thin sourceward to the north. Grain sizes in clastic rocks coarsen and lower strata wedge out northward beneath disconformably overlying strata. The dominantly continental, early Aphebian (2.1-2.5 x 10' years) Huronian rocks are probably older than most other Aphebian rocks in the Canadian Shield which are dominantly marine, deposited on relatively smooth surfaces under comparatively stable conditions. Probable Huronian correla- tives in the Mistassini region, Quebec, contain radioactive conglomerates and limited areas of similar rocks occur near Padlei, Northwest Territories. Highly metamorphosed remnants of analogous strata may be present in the Grenville and Churchill Provinces. Deposition of Huronian uraniferous conglomerates was controlled by the disposition of Huronian lava fields and by tectonic movements during sedimentation as well as by local and sourceward topographic features. Exploration possibilities near Elliot Lake, where ore is associated with valleys in basement greenstone, are mainly at depths greater than 3,000 feet. Conglomeratic zones