Geology and Mineral Resources of the Pico de Itabirito District Minas Gerais, Brazil GEOLOGICAL SURVEY PROFESSIONAL PAPER 341-F Prepared in cooperation with the Departamento Nacional da Producao Mineral of Brazil under the auspices of the Agency for International Development of the United States Department of State Geology and Mineral Resources of the Pico de Itabirito District Minas Gerais, Brazil By ROBERTS M. WALLACE GEOLOGY AND MINERAL RESOURCES OF PARTS OF MINAS GERAIS, BRAZIL GEOLOGICAL SURVEY PROFESSIONAL PAPER 341-F Prepared in cooperation with the Departamento Nacional da Producao Mineral of Brazil under the au-spices of the Agency for International Development of the United States Department of State UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1965 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract_ _---_-_---___-__________________________ Fl Metamorphism_ ____________________________________ F34 Introduction. ______________________________________ 2 Geologic history____________________________________ 35 Purpose of the survey.__________________________ 3 Economic geology______---_---__-_-_----_---------- 36 History of investigations_______________________ 3 Iron ores.__--_-------------------------------- 37 Present work_________________________________ 3 High-grade hematite______-__-_-------_-- 37 Coordinate system for locations________________ 4 Origin_______-____-__-_--_---_---_----_ 37 Acknowledgments___ _ _________________________ 4 Mineralogy _________-__--_------------- 39 Geography _-------_---------____________________ 4 Supergene ore______________--_--_--_---_-_- 40 Topography and drainage______________________ 4 Rolado ore_________________--_--_--_---_--_ 40 Climate and vegetation__________________________ 5 Canga __________________----_----_-----_ 41 Population, industry, and transportation________ 6 Ocher_____-_------------------------------ 42 Geology.__________________________________________ Itabirite_ _______________--__-_-_----------- 42 7 42 Precambrian metasedimentary rocks ______________ 7 Manganese _________--__----------------------- 42 Pre-Rio das Velhas(?) rocks._________________ Mangantferous rocks._________________-----_ 7 42 Rio das Velhas Series______________________ 7 Itabirite. _______________-_--___-__----- 43 Nova Lima Group______________________ 7 Carbonate rocks________________________ 44 Minas Series..------_______________________ 10 Mixed itabirite and carbonate rock protore. 44 Caraga Group._________________________ 10 Clastic rocks_____________--------_-_--- 45 Moeda Formation. _________________ 10 Production ______-_____------_------------- 45 Batatal Formation._________________ 12 Origin of manganese ore__------------------- 46 Itabira Group._________________________ 13 Marble___------------------------------------- 46 Cau6 Itabirite._____________________ 13 Clay. 46 Gandarela Formation.______________ Sand. __-_-_---_------------------------------- 16 46 Piracicaba Group.______________________ Glass sand .------------- ---- -- 17 48 Cercadinho Formation____________ 17 Kyanite ________-_--_-------------------------- 48 F6cho do Funil Formation___________ Gold_____-- 19 48 TaboOes Quartzite._________________ 20 Cata Branca mine____--__--_--------------- 48 Barrewo Formation.________________ 20 Santo Ant6nio lode.________-__------------- 49 Itacolomf Series.___________________________ 20 Iron mines____---__---------------------------- Granitic rocks._________________________________ Pico de Itabirito --_----_--.-------.-------- 49 23 51 Complex west of the Serra da Moeda________ 24 Exploration. __.___.___-_---_----------- Distribution of high-grade hematite. .. 52 Granite gneiss._________________________ 24 52 Granodiorite. __________________________ 25 Broken ore__________._-_---_----- 53 Ba§ao granitic complex..____________________ 25 Mining methods._____.___.---_---_----- Reserves _ _ _______-_-__-_----------- 53 Relation of Ba$ao granites to Minas Series- 26 55 Dike rocks and quartz veins____________________ 27 Pau Branco._____-__--_-------------------- 55 Granodiorite dikes and pegmatite.____________ Reserves. _________-____-_-------------- 27 55 Diabase and other mafic dikes._______________ 27 Vdrzea do Lopes-____---__------------------ 56 Amphibolitic rocks________________________ Reserves_ ____________-_------------- 28 56 Quartz veins.______________________________ 28 Ab6boras deposit-___________-_------------- 58 Surficial deposits______________________________ 28 Andaime. _ _- ____________-_-------------- 58 Canga__ _ __________________________________ 29 Cata Branca rolado deposits ___-_-_---__ 58 Ferruginous soil.___________________________ 29 Manganese mines.___-___-.__---_--------------- 58 Clay______________________________________ 29 Sapecado mine _________________--------- 60 Quartzite talus and residual sand_____________ 30 Reserves ____-____._--------------- Alluvium. _________________________________ Lagoa Grande deposits__._____-_------------ 60 30 62 Landslide debris____________________________ 30 Marble quarries.___._____________----_--------- Jazida do Urubu. _________-__-_-_------- 62 Structure-------------_-________.__________________ 31 Quarrying methods.__________--_------- 62 Moeda syncline_______________________________ 31 Jazida Siema.________________--_----------- 64 Minor folds._______________________________ 31 Copper deposits.___.____.-___--_--------------- 64 Faults__-----------.__--_____________________ 32 Jazida do C6rrego do Eixo__----------------- 64 Cleavage._____________________________________ 32 Kyanite mines.. __________------------------- 65 Lineation. _____________________________________ 33 References cited.________________-_---_------------- 65 Joints._____________ 33 Index _____________________-_____------------------ 67 in ILLUSTRATIONS [Plates are in separate volume] PLATES 1-4. Geologic map and sections of the 1. Lagoa Grande quadrangle, Minas Gerais, Brazil. 2. Marinho da Serra quadrangle, Minas Gerais, Brazil. 3. Itabirito quadrangle, Minas Gerais, Brazil. 4. Bac.ao quadrangle, Minas Gerais, Brazil. 5. Simplified structural and geologic map of the Pico de Itabirito district, Minas Gerais, Brazil. 6. Geologic map and schematic section of the Pico de Itabirito iron-ore deposit, Minas Gerais, Brazil. 7. Exploration adit 1, Pico de Itabirito, Itabirito quadrangle, Minas Gerais, Brazil. 8. Exploration adit 2, Pico de Itabirito, Itabirito quadrangle, Minas Gerais, Brazil. 9. Geologic map showing subsurface data of the Pau Branco iron mine, Lagoa Grande quadrangle, Minas Gerais, Brazil. 10. Geologic map and sections of Ab6boras iron deposit, Minas Gerais, Brazil. Page FIGURE 1. Index map of the Quadrilatero Ferrffero.____---_____________________ ___________ ______ F2 2-12. Photograph of 2. Mato in the Serra da Moeda_____________________________________________________________ 5 3. Grassy highlands in the Moeda basin_.___________________________________________________ 6 4. Contact between the Moeda and Batatal Formations______-________-__-___-__-____----_______ 10 5. Type locality of the Moeda Formation-________-___----__-_-_--__---__-------_----_------__- 11 6. Crossbedding in the Moeda Formation_________-____---_------_--_--_------------_-------__- 11 7. Gently folded itabirite_______ ___---__-_________________ _ 14 8. Crossbedding in the Cercadinho Formation_____-_____--____----__----_----,______-----______ 18 9. Ripple marks in the Cercadinho Formation________ __________________________________________ 18 10. Weathered contact in marble-------------------------------------------------------------- 20 11. Conglomerate of the Itacolomf Series__-___-_---_--_---__----------------------------------- 22 12. Crossbedding in the Itacolomf Series _____________-_______-_--____---_-_-___-_--__-___----- 22 13. Conjugate joint system_________...______________________________________________________________ 34 14. Crumpled bedding in itabirite_______________________________________________________ -___ __ 38 15. Histograms of sand samples______--_---____________--_-_--_---_------------------_-_--- ______ 47 16-19. Photograph of 16. Foundations of an old blast furnace._ ___________________---_--_-______---__--_-_-----__--__ 50 17. Pico de Itabirito.____________________________________________-.____ 51 18. Lump ore____-__________________-__________-___--__---__-----__---_-_-_---_--_---------- 53 19. Western face of Pico de Itabirito______________-___---_--------_------_------_----------_-_- 54 20. Geologic map of the Varzea do Lopes mine_____-___---__--_-----_----__--------------- _______ 57 21. Geologic sketch map of the Sapecado mine____-_____---_---_---------_--------_---------- _--____ 59 22. Geologic sketch map of the Lagoa Grande manganese mines--__-_-__-_-_____----_---_----_- -_-____ 61 23. Photograph of open-pit manganese mine____________________--____--___-_-----------_---- ------- 62 24. Geologic sketch map of the Jazida do Urubu marble quarry___--__--_---_----_-_------_---- _______ 63 25. Photograph of reverse fault in marble_______________-______-____________----_--------- -___-__ 64 TABLES Page TABLE 1. Mineral content and average grain size of fresh rock samples of the Nova Lima Group, Itabirito quadrangle. F8 2. Chemical composition of weathered Cau6 Itabirite__-_______----_--------_________--_ 14 3. Itabirite from tunnel