B. S. Butler and W. S. Burbank 

The Copper Deposits of Michigan

U S Geological Survey Professional Paper 144 (1929)

CONTENTS

Outline of report-------------------------------------------------------- XI Geology------------------------------------------------------------ XI General features------------------------------------------- XI Lava tops or amygdaloids ----------------------------- XI Oxidation of lavas ---------------------------------------- XI Copper in trap---------------------------------------------- XI Structure----------------------------------------------------- XI Ore deposits------------------------------------------------------ XII Conglomerate lodes ------------------------------------- XII Amygdaloid lodes---------------------------------------- XII Ore shoots-------------------------------------------------- XII Mineralized fissures-------------------------------------- XII Changes with depth ------------------------------------- XII Genesis of the deposits --------------------------------- XII Part 1. General features--------------------------------------------------- 1 Introduction --------------------------------------------------------- 1 Field work and authorship -------------------------------- 1 Scope of report----------------------------------------------- 1 Acknowledgments ------------------------------------------ 2 Previous investigation ------------------------------------- 2 Bibliography -------------------------------------------------- 3 Geography---------------------------------------------------------- 14 Location------------------------------------------------------ 14 Topography------------------------------------------------- 14 Climate-------------------------------------------------------- 14 Industries---------------------------------------------------- 15 Transportation --------------------------------------------- 15 Power---------------------------------------------------------- 15 Physiography ----------------------------------------------------- 16 Bedrock geology-------------------------------------------------- 16 Broader relations ------------------------------------------- 16 Location and extent --------------------------------- 16 Character of the rocks ------------------------------ 16 Stratigraphy -------------------------------------------------- 17 Maps and sections ---------------------------------- 17 Age and relations ------------------------------------ 17 General character and distribution --------------- 17 Sediments ---------------------------------------------- 18 Distribution ------------------------------------- 18 General character ------------------------------ 18 Conglomerate ----------------------------------- 18 Felsite conglomerate -------------------- 18 Extent and thickness of beds--- 18 Vertical distribution--------------- 18 Character of material ------------- 18 Character of beds- ---------------- 19 Character of underlying bed---- 19 Source of material ----------------- 19 Manner of deposition------------- 20 Amygdaloidal conglomerate ---------- 20 Relation to felsite conglom- erate ---------------------------------- 20 Origin -------------------------------- 20 Sandstone and shale--------------------------- 21 Ash and tuff-------------------------------------- 21

Part 1. General features-Continued.                                             Page Bedrock geology-Continued. Stratigraphy-Continued. Igneous rocks -------------------------------------------- 21 Extrusive rocks ------------------------------------ 21 Distribution ---------------------------------- 21 Extent of beds ------------------------------- 21 Thickness ------------------------------------ 21 Composition of flows --------------------- 23 Textural types ------------------------------- 23 Ophite----------------------------------- 24 Porphyrites ---------------------------- 24 Glomeroporphyrites ----------------- 24 Melaphyre ----------------------------- 24 Dolerite --------------------------------- 24 Relation of texture to composition ----- 24 Distribution of the different      rocks --------------------------------------- 24 Character of eruptive rocks -------------- 25 Location of volcanic vents--------------- 26 Amygdaloids -------------------------------------- 26 Trap -------------------------------------------- 26 Bottom amygdaloid layer------------------ 27 The lava tops -------------------------------- 27 Varieties ------------------------------- 27 Smooth tops-------------------------- 28 Fragmental or brecciated       tops-------------------------------- 29 Character ---------------------- 29 Origin --------------------------- 31 Scoriaceous tops ------------------- 33 Alteration ------------------------------------------ 34 Alteration of traps ------------------------- 34 Alteration of the lava tops -------------- 34 Red color of amygdaloid tops----------- 34 Statement of the problem---------- 34 Red tops of unaltered western     flows--------------------------------- 35 Oxidation in smooth-top flows of      Keweenawan series-------------------- 35 Oxidation and concentration in     brecciated-top flows ------------------- 36 Mineralogic features ---------------------- 37 Cause of iron oxidation and con-     centration -------------------------------- 38 Modern weathering----------------- 38 Independent solutions------------- 38 Surface weathering immediately after extrusion------------------------ 39 Hydrothermal alteration------------ 41 Atmospheric oxidation of hot tops ------------------------------------- 42 Magmatic processes---------------- 42 Magmatic segregation------- 42 Fumarolic alteration----------- 42 Action of gases from the flows------------------------------ 43

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Part 1. General features-Continued.                                           Page Bedrock geology-Continued. Stratigraphy-Continued. Igneous rocks-Continued. Copper content of the basalts --------------- 45 Intrusive rocks----------------------------------- 46 General features -------------------------- 46 Quartz porphyry and felsite ----------- 47 Basic dikes --------------------------------- 47 Age of intrusive rocks------------------- 47 Structure-------------------------------------------------------- 48 Folds------------------------------------------------------ 48 Faults----------------------------------------------------- 48 Age and cause of folding and faulting---------- 50 Mineralogy---------------------------------------------------- 53 Rock-forming period --------------------------------- 53 Ore-forming period ----------------------------------- 53 Period of weathering --------------------------------- 55 Minerals of the Keweenawan copper      bearing rocks --------------------------------------- 55 Native metals ------------------------------------ 55 Sulphides ----------------------------------------- 55 Arsenides ---------------------------------------- 56 Haloids -------------------------------------------- 58 Oxides---------------------------------------------- 58 Carbonates --------------------------------------- 59 Silicates-------------------------------------------- 59 Phosphates --------------------------------------- 62 Sulphates ----------------------------------------- 62 Molybdates and tungstates ------------------ 62 Hvdrocarbon ------------------------------------- 62 Part 2. Ore deposits-------------------------------------------------------- 63 History------------------------------------------------------------------ 63 Production------------------------------------------------------------- 64 Operating practice--------------------------------------------------- 98 Mining ---------------------------------------------------------- 98 Development ------------------------------------------- 98 Stoping -------------------------------------------------- 99 Open stope -------------------------------------- 99 Room and pillar --------------------------------- 99 Shrinkage stope --------------------------------- 99 Horizontal cut and fill -------------------------- 99 Transportation ---------------------------------------- 100 Underground conditions---------------------------- 100 Milling---------------------------------------------------------- 100 Smelting-------------------------------------------------------- 101 Copper deposits---------------------------------------------------- 101 Principal types------------------------------------------------ 101 Distribution in the Keweenawan series ---------------- 101 Conglomerate lodes ----------------------------------------- 101 Physical character ------------------------------------ 101 Iron content-------------------------------------------- 102 Mineralization ----------------------------------------- 103 Mineralogy -------------------------------------- 103 Rock alteration---------------------------------- 103 Distribution of copper in the lode---------------- 103 General controls ------------------------------- 103 Richness in relation to depth--------------- 104 Sandstone and shale lodes ------------------------------- 105 General relations ------------------------------------- 105 Mineralization and rock alteration---------------- 105 Amygdaloid lodes ------------------------------------------ 106 Types of amygdaloid ------------------------------- 106 Brecciated amygdaloid lodes---------------------- 106 Physical character ----------------------------- 106 Iron content------------------------------------- 107 Mineralization ---------------------------------- 107 Mineralogy------------------------------- 107 Rock alteration-------------------------- 107

Part 2. Ore deposits-Continued.                                                 Page Copper deposits-Continued. Amygdaloid lodes-Continued. Cellular amygdaloid lodes--------------------------- 108 Scoriaceous amygdaloid lodes -------------------- 109 Distribution of copper in amygdaloid           lodes---------------------------------------------- 109 Distribution of shoots in the lodes-------- 109 Distribution of copper in the shoots------ 109 Richness in relation to depth----------------------------- 110 Fissure deposits--------------------------------------------- 110 General features -------------------------------------- 110 Distribution of copper in veins ------------------- 111 Has there been enrichment of the deposits?---------------- 112 No evidence that the lodes are poor at the        surface and richer below------------------------------ 112 Kearsarge lode ---------------------------------------- 112 Osceola lode ------------------------------------------- 112 Calumet & Hecla conglomerate ------------------- 112 Pewabic amygdaloid lodes ------------------------- 113 Atlantic lode ------------------------------------------- 113 Isle Royale lode --------------------------------------- 113 Baltic lode----------------------------------------------- 113 Evergreen and succeeding lodes ----------------- 113 Nonesuch lode----------------------------------------- 113 Veins------------------------------------------------------ 113 No evidence of leaching and removal of copper        near the surface------------------------------------------ 113 No evidence of enrichment at the salt-water        horizon----------------------------------------------------- 114 Summary and conclusions --------------------------------- 114 Persistence with depth-------------------------------------- 114 Conditions determining position of ore shoots ------------ 115 Permeability of rock------------------------------------------ 115 Barriers of relatively impermeable rock ----------------- 115 Fault barrier---------------------------------------------------- 116 Folds------------------------------------------------------------- 117 Strike fissures-------------------------------------------------- 117 Cross fissures------------------------------------------------- 117 Influence of thick flows ------------------------------------ 118 Chemical composition -------------------------------------- 118 Genesis of the deposits------------------------------------------- 118 Similar origin of all types ---------------------------------- 118 Features common to all types ---------------------------- 119 Single period of mineralization --------------------------- 119 Hypotheses of origin---------------------------------------- 120 Deposition by descending solutions ------------ 120 Source of copper-------------------------------- 120 Mode of transportation------------------------ 121 Cause of precipitation ------------------------- 122 Chloride water conception ------------ 122 Mine waters-------------------------------- 122 Deposition by ascending solutions -------------- 124 Source of the copper---------------------------------- 124 Direction of movement of the solutions---------- 125 Means of access of the solutions ----------------- 125 Ascent from contacts of the         Duluth gabbro ----------------------------- 125 Ascent from the Keweenaw fault------------ 126 Gradual accumulation in permeable                   channelways ------------------------------------- 127 Causes and conditions of precipitation ---------- 127 Precipitation by reducing action       of ferrous iron ------------------------------- 127 Precipitation in consequence of        saturation------------------------------------ 129 Precipitation by oxidation -------------------- 129 Presence of sulphides------------------- 130

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Part 3. Detailed description of lodes and fissures---Con,          page Kearsarge lode-Continued. Alteration and mineralization -------------------------------198 Oxidation ------------------------------------------------- 198 Alteration accompanying mineralization---------- 198 Yield-------------------------------------------------------- 198 Probable causes of rich and poor ground -------------- 199 Character of rock ----------------------------------------------------------- 199 Influence of structure and texture -------------------------------------- 200 Structure------------------------------------------- 200 Texture -------------------------------------------- 200 Influence of fissures on the lode ------------------ 201 Conditions favorable to mineralization in the      known productive portion of the Kearsarge      lode --------------------------------------------------- 201 Effect of depth on the copper content of the      lode---------------------------------------------------- 202 Mayflower-Old Colony mine ------------------------------------ 202 Structure-------------------------------------------------------- 202 Developments------------------------------------------------- 203 Isle Royale lode ----------------------------------------------------- 203 History and production ------------------------------------ 203 Extent and correlation -------------------------------------- 203 Character of lode -------------------------------------------- 204 Fragmental zone -------------------------------------- 204 Banded amygdaloid --------------------------------- 204 Foot inclusion zone --------------------------------- 204 Vein trap------------------------------------------------ 205 Main trap----------------------------------------------- 205 Hanging-wall trap ------------------------------------ 205 Distribution of types -------------------------------- 205 Structure------------------------------------------------------- 206 Isle Royale syncline --------------------------------- 206 Faults---------------------------------------------------- 206 Fissures------------------------------------------------- 207 Rock alteration and ore deposition -------------------- 208 First period--------------------------------------------- 208 Second period ----------------------------------------- 208 Chemistry of ore deposition ----------------------- 210 Arcadian lode-------------------------------------------------------- 211 New Arcadian lode------------------------------------------------- 211 Winona lode --------------------------------------------------------- 211 Production and character ---------------------------------- 211 Wyandot mine------------------------------------------------ 212 Elm River mine ------------------------------------------------ 212 Cherokee mine------------------------------------------------- 212 Wyandot No. 8 lode------------------------------------------------ 212 Evergreen and succeeding lodes ------------------------------- 212 Occurrence----------------------------------------------------- 212 Production ----------------------------------------------------- 213 Character of flows ------------------------------------------- 213 Structure-------------------------------------------------------- 213 Character of amygdaloids --------------------------------- 213 Mineralization ------------------------------------------------ 213 Rock alteration ----------------------------------------------- 213 Relation of mineralization to character of lode-------- 213 Butler lode ----------------------------------------------------- 214 Mass mine----------------------------------------------- 214 Lithologic character ---------------------------- 214 Structure ------------------------------------------ 214 Mineralization ----------------------------------- 214 Yield------------------------------------------------ 214 Adventure mine --------------------------------------- 214 South Lake mine --------------------------------------- 214 Lake mine------------------------------------------------ 214 North Lake mine --------------------------------------- 214 Evergreen lode------------------------------------------------ 214 Mass mine----------------------------------------------- 214 Adventure mine --------------------------------------- 215

Part 3. Detailed description of lodes and fissures-Con.            Page Evergreen and succeeding lodes-Continued. Evergreen lode-Continued. South Lake mine --------------------------------------- 215 Lake mine------------------------------------------------ 215 North Lake mine --------------------------------------- 215 Knowlton lode------------------------------------------------ 215 Mass mine---------------------------------------------- 215 Adventure mine -------------------------------------- 215 Lake mine ----------------------------------------------- 215 Michigan mine ----------------------------------------- 215 Ogima lode ---------------------------------------------------- 216 Other lodes---------------------------------------------------- 216 Forest ("Victoria") lode ------------------------------------------- 216 Production----------------------------------------------------- 216 Geologic horizon---------------------------------------------- 216 Character of amygdaloid ----------------------------------- 216 Mineralization ------------------------------------------------- 216 Extent of development -------------------------------------- 216 Lake lode-------------------------------------------------------------- 216 Production------------------------------------------------------ 216 Location -------------------------------------------------------- 216 Structure-------------------------------------------------------- 217 Correlation ----------------------------------------------------- 217 Character------------------------------------------------------- 217 Algomah lode-------------------------------------------------------- 217 Baltic lode------------------------------------------------------------- 217 History and production ------------------------------------- 217 Extent and correlation --------------------------------------- 218 Baltic flow------------------------------------------------------- 218 Structure--------------------------------------------------------- 218 Folds------------------------------------------------------- 218 Cross faults and slips --------------------------------- 218 Strike fissures-------------------------------------------- 219 Character of Baltic amygdaloid ---------------------------- 219 Oxidation--------------------------------------------------------- 219 Mineralization -------------------------------------------------- 219 Minerals--------------------------------------------------- 219 Rock alteration ------------------------------------------ 220 Relation of mineralization to character of       lode----------------------------------------------------- 220 Results of operation ------------------------------------------ 220 Baltic West lode ----------------------------------------------- 221 Relation of fissure mineralization and lode       mineralization------------------------------------------------ 221 Superior lodes--------------------------------------------------------- 221 Occurrence------------------------------------------------------- 221 Production-------------------------------------------------------- 221 Character--------------------------------------------------------- 222 Mineralization -------------------------------------------------- 222 Ore shoots------------------------------------------------------- 222 Isle Royale ------------------------------------------------------------- 222 Felsite of Indiana mine ---------------------------------------------- 222 Development ---------------------------------------------------- 222 Mineralization --------------------------------------------------- 222 Fissure deposits------------------------------------------------------- 223 History------------------------------------------------------------- 223 Production-------------------------------------------------------- 223 Distribution ------------------------------------------------------ 223 Distribution of copper in the fissures --------------------- 223 State of division of copper ----------------------------------- 225 Exploration of fissures ---------------------------------------- 225 Incentive to exploration -------------------------------- 225 General features of exploration ----------------------- 225 Method of exploration ---------------------------------- 226 Suggested explorations -------------------------------- 226 Fissure mines and prospects of Keweenaw      and Ontonagon Counties -------------------------------- 226 Star---------------------------------------------------------- 226

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Some portions of the professional paper have not been included in this website. These include the bibliography, theories of deposition, geophysical exploration, production history and index. Large plates that were in separate pockets have also not been reproduced. See the original work for these topics. See List of Illustrations for plates and figures available.

The pages reproduced are 1-3, 14-33, 46-63, 98-120, 141-156, 169-233

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