BULLETIN 51 Geology of the Questa Molybdenum (Moly) Mine Area, Taos County, New Mexico BY JOHN H. SCHILLING Local structure and stratigraphy, and detailed description of mineral deposits as related to regional geology, with guides to ore exploration in the surrounding area 1956 STATE BUREAU OF MINES AND MINERAL RESOURCES NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY CAMPUS STATION SOCORRO, NEW MEXICO NEW MEXICO INSTITUTE OF MINING & TECHNOLOGY E. J. Workman, President STATE BUREAU OF MINES AND MINERAL RESOURCES Eugene Callaghan, Director THE REGENTS MEMBERS EX OFFICIO THE HONORABLE JOHN F. SIMMS ......................Governor of New Mexico MRS. GEORGIA L. LUSK ...................... Superintendent of Public Instruction APPOINTED MEMBERS ROBERT W. BOTTS .................................................................... Albuquerque HOLM O. BURSUM, JR. .......................................................................Socorro THOMAS M. CRAMER ...................................................................... Carlsbad JOHN N. MATHEWS, JR.......................................................................Socorro RICHARD A. MATUSZESKI ...................................................... Albuquerque FRONTISPIECE View of Sulphur Gulch showing W level dump (lower left), landslide covering portals of Glory Hole workings (center), and the altered area — hydrothermal pipe — at the head of Sulphur Gulch (treeless area, upper right). Contents Page ABSTRACT ....................................................................................................ix INTRODUCTION ...........................................................................................1 Purpose and Scope .......................................................................................1 Methods of Investigation .............................................................................1 Previous Work .............................................................................................2 Acknowledgments .......................................................................................2 Geographic Features ....................................................................................4 Location and Accessibility ........................................................................4 Physical Features ......................................................................................4 Climate ......................................................................................................4 History and Production ................................................................................6 Surface Plant and Mine ................................................................................8 Mining Methods ...........................................................................................8 Prospecting and Exploration .....................................................................8 Development .............................................................................................9 Stoping ......................................................................................................9 Transportation .........................................................................................10 Drainage and Ventilation ........................................................................10 Milling Methods ........................................................................................10 GEOLOGIC SETTING ..................................................................................11 Descriptive Geology ..................................................................................11 Introduction .............................................................................................11 Precambrian ............................................................................................11 Amphibolite Complex ........................................................................11 Cabresto Metaquartzite .......................................................................16 Granite ................................................................................................18 Pegmatites ...........................................................................................19 Diabase Dikes .....................................................................................19 Pennsylvanian-Permian (?) Sangre de Cristo (?) Formation ...................20 Tertiary ...................................................................................................23 Volcanic Complex ..............................................................................23 Andesite and Rhyolite Intrusives ........................................................25 Soda Granite .......................................................................................26 Postgranite Dikes ................................................................................30 Quaternary ..............................................................................................30 Page Terrace Gravels .................................................................................. 30 Cemented Gravels .............................................................................. 31 Alluvium ............................................................................................ 31 Mud-Flows ......................................................................................... 31 Cover .................................................................................................. 32 Structural Geology ..................................................... ................................ 33 Introduction ............................................................................................ 33 Regional Structures ................................................................................ 33 Folds .................................................................................................. 33 Faults .................................................................................................. 34 Fractures ............................................................................................ 35 Brecciation ......................................................................................... 37 Foliation ............................................................................................. 37 Alteration .................................................................................................. 37 Introduction ............................................................................................ 37 Hydrothermal Pipes ................................................................................ 38 Propylitic Alteration ............................................................................... 39 Geologic History ....................................................................................... 40 MINERAL DEPOSITS ................................................................................. 42 Introduction ............................................................................................... 42 Questa Molybdenum Mine Deposit .......................................................... 42 Introduction ............................................................................................ 42 Spacial Relation of Veins to Rock Units and Structure .......................... 42 Size and Form of Veins .......................................................................... 46 Ore Shoots .............................................................................................. 51 Vein Mineralogy .................................................................................... 54 Introduction ........................................................................................ 54 Ore Minerals ...................................................................................... 54 Molybdenite ................................................................................... 54 Gangue Minerals ................................................................................ 55 Apatite ........................................................................................... 55 Biotite ............................................................................................ 55 Calcite ............................................................................................ 55 Chalcopyrite .................................................................................. 55 Chlorite .......................................................................................... 56 Ferrimolybdite ............................................................................... 56 Fluorite .......................................................................................... 56 Galena ............................................................................................ 56 Page Gold ...............................................................................................56 Graphite .........................................................................................56 Hübnerite .......................................................................................57 Limonite ........................................................................................57 Malachite .......................................................................................57 Orthoclase .....................................................................................57