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Volcanic Rocks of the Cienega Area, Santa Fe County, New Mexico

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Volcanic Rocks of the Cienega Area, Santa Fe County, New Mexico BULLETIN 54 Volcanic Rocks of the Cienega Area, Santa Fe County, New Mexico by MING-SHAN SUN and BREWSTER BALDWIN Sequence and geochemistry of Cenozoic volcanic rock units, with a discussion of the norm classification 1 9 5 8 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 Alvin J. Thompson, Director THE REGENTS MEMBERS Ex OFFICIO The Honorable Edwin L. Mechem .................. Governor of New Mexico Mrs. Georgia L. Lusk ........................ Superintendent of Public Instruction APPOINTED MEMBERS Robert W. Botts ................................................................. Albuquerque Holm 0. Bursum, Jr. .................................................................. Socorro Thomas M. Cramer .................................................................. Carlsbad John N. Mathews, Jr. ................................................................. Socorro Richard A. Matuszeski ....................................................... Albuquerque Contents Page ABSTRACT ...................................................................................................... 1 INTRODUCTION ......................................................................................... 3 Purpose .......................................................................................................... 3 Setting ............................................................................................................ 3 Previous work ............................................................................................... 5 Method of work ........................................................................................... 5 Acknowledgments ....................................................................................... 6 FIELD RELATIONSHIPS (by Brewster Baldwin) ................................... 7 Stratigraphy ................................................................................................... 7 Cretaceous mudstone ............................................................................... 8 Galisteo formation .................................................................................... 8 Andesite breccia ...................................................................................... 10 Augite monzonite ................................................................................... 11 Calcic latite .................................................................................................. 12 Glassy latite .............................................................................................. 13 Units of uncertain stratigraphic position ............................................. 14 Volcanic conglomerate ...................................................................... 14 Augite basalt ........................................................................................ 14 Hornblende andesite dike ................................................................. 14 Vent breccia ......................................................................................... 15 Felsite dike ........................................................................................... 15 Cieneguilla limburgite ............................................................................. 15 Ancha formation ..................................................................................... 18 Basalt ......................................................................................................... 18 Terrace gravel ............................................................................................. 19 Alluvium ...................................................................................................... 19 Cover ............................................................................................................ 19 Age and correlation ................................................................................... 19 Structure ......................................................................................................... 23 LABORATORY STUDIES (by Ming-Shan Sun) .................................... 26 Petrography ................................................................................................. 26 Introduction ............................................................................................. 26 The term "monzonite" ........................................................................... 26 Andesite breccia ...................................................................................... 27 iii Page Augite monzonite ................................................................................... 29 Calcic latite ............................................................................................... 30 Hornblende andesite .............................................................................. 31 Glassy latite .............................................................................................. 31 Felsite ....................................................................................................... 32 Vent breccia ............................................................................................. 33 Cieneguilla limburgite ............................................................................ 33 Olivine basalt ........................................................................................ 34 Limburgite ............................................................................................ 34 Basalt ........................................................................................................ 35 Petrology ...................................................................................................... 36 Norm classification ..................................................................................... 38 Weight norm ........................................................................................... 40 Molecular norm........................................................................................ 41 Norms of the Cienega rocks ................................................................. 45 Geochemical aspects .................................................................................. 45 Index of refraction ................................................................................. 45 General discussion .............................................................................. 45 Artificial glasses .................................................................................... 48 Chemical composition ........................................................................... 51 Minor constituents .............................................................................. 51 Major constituents ............................................................................... 54 APPENDIX I .................................................................................................. 59 Rules for the calculation of norms ............................................................ 59 Weight norm ........................................................................................... 60 Molecular norm ...................................................................................... 64 APPENDIX II ................................................................................................ 69 Summary of data from rock samples, Cienega area, New Mexico 69 REFERENCES ............................................................................................... 74 INDEX ............................................................................................................. 77 Illustrations TABLES 1. Rock units of the Cienega area, New Mexico ....................................... 7 2. Orthoclase-plagioclase ratios of the Cienega monzonite, latite, and andesite, in comparison with those of Daly's average monzonite, andesite, and diorite .......................................................... 27 iv Page 3. Grain-size analysis of disintegrated andesite breccia .................... 28 4. The C.I.P.W. weight norms of seven volcanic rocks, Cienega area, New Mexico .................................................................................. 43 5. The molecular norms of seven volcanic rocks, Cienega area, New Mexico ........................................................................................... 44 6. Effect of various oxides on the index of refraction of glasses of binary or ternary system with silica ..................................................... 46 7. The ionic density of the cations which occur as modifiers in silicate glass ............................................................................................. 47 8. Lower limits of spectrographic detection ....................................... 51 9. Minor constituents of the Cienega volcanic rocks ........................ 53 10. Chemical composition of seven volcanic rocks, Cienega area, New Mexico ........................................................................................... 54 11. Modified Holmquist formulae .......................................................... 55 12. Calculation of standard rock cell of olivine basalt of the Cienega area ...........................................................................................
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