Michigan Technological University Digital Commons @ Michigan Tech Dissertations, Master's Theses and Master's Reports 2015 INSIGHTS INTO THE RELATIONSHIP BETWEEN MIXING DURATION AND VOLCANIC EXPLOSIVITY INDEX (VEI): PACAYA AND FUEGO VOLCANOES, GUATEMALA Nicola Mari Michigan Technological University, [email protected] Copyright 2015 Nicola Mari Recommended Citation Mari, Nicola, "INSIGHTS INTO THE RELATIONSHIP BETWEEN MIXING DURATION AND VOLCANIC EXPLOSIVITY INDEX (VEI): PACAYA AND FUEGO VOLCANOES, GUATEMALA", Open Access Master's Thesis, Michigan Technological University, 2015. https://doi.org/10.37099/mtu.dc.etdr/30 Follow this and additional works at: https://digitalcommons.mtu.edu/etdr Part of the Geochemistry Commons, and the Volcanology Commons INSIGHTS INTO THE RELATIONSHIP BETWEEN MIXING DURATION AND VOLCANIC EXPLOSIVITY INDEX (VEI): PACAYA AND FUEGO VOLCANOES, GUATEMALA By Nicola Mari A THESIS Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE In Geology MICHIGAN TECHNOLOGICAL UNIVERSITY 2015 © 2015 Nicola Mari This thesis has been approved in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE in Geology. Department of Geological and Mining Engineering and Sciences Thesis Advisor: William I. Rose Committee Member: Chad D. Deering Committee Member: Gregory P. Waite Committee Member: Alessandro Tibaldi Department Chair: John S. Gierke Table of Contents Page List of Figures ................................................................................................................... 5 List of Tables ................................................................................................................... 10 Acknowledgments ........................................................................................................... 11 Abstract ............................................................................................................................ 12 1 - Introduction ............................................................................................................... 13 1.1 - Postulate of research ........................................................................................... 13 1.2 - Volcanism of Pacaya and Fuego ........................................................................ 14 1.2.1 – Geodynamic setting ................................................................................... 14 1.2.2 – Pacaya volcano ......................................................................................... 14 1.2.3 – Fuego volcano ........................................................................................... 15 2 – Sample selection ........................................................................................................ 17 3 – Methodology .............................................................................................................. 21 3.1 – Polarized light microscopy ............................................................................... 21 3.2 – SEM images acquisition and EDS analyses ...................................................... 21 3.3 – Image processing and CSD analysis ................................................................. 22 3.4 – Viscosity model ................................................................................................ 25 4 - Results ......................................................................................................................... 26 4.1 – Qualitative descriptions ..................................................................................... 26 4.1.1 – Sample characterization .......................................................................... 26 4.1.2 – Disequilibrium textures in VEI 0 ............................................................. 26 4.1.3 – Disequilibrium textures in VEI 1 ............................................................. 29 4.1.4 – Disequilibrium textures in VEI 2 ............................................................. 35 3 4.1.5 – Disequilibrium textures in VEI 4 ............................................................ 38 4.2 – Quantitative analysis ......................................................................................... 42 4.2.1 – Geochemistry .......................................................................................... 42 4.2.2 – Modal data .............................................................................................. 43 4.2.3 – Reverse zoning chemical data ................................................................. 44 4.2.4 – Disequilibrium textures vs. VEI .............................................................. 45 4.2.5 – Plagioclase crystal size distributions (CSD) .......................................... 45 4.2.6 –Viscosity data ........................................................................................... 47 5 - Discussion ................................................................................................................... 50 5.1 - Magma mixing signatures .................................................................................. 50 5.2 - Interpretation of Crystal Size Distributions data ............................................... 53 5.3 – Timing effect ..................................................................................................... 59 6 - Conclusion .................................................................................................................. 61 7 - References .................................................................................................................. 63 8 - Appendices ................................................................................................................. 69 8.1 – Appendix A _ Optical Microscopy Sample Preparation procedure .................. 69 8.2 – Appendix B _ More polarized light microscope images ................................... 69 8.3 – Appendix C _ More SEI images ........................................................................ 82 8.4 – Appendix D _ Modal data from other works ................................................... 101 8.5 – Appendix E _ SEM characteristics .................................................................. 102 8.6 – Appendix F _ More viscosity vs. temperature diagrams ................................. 102 4 List of Figures Page Fig. 1.1 Pacaya volcano .................................................................................................... 15 Fig. 1.2 Fuego volcano...................................................................................................... 16 Fig. 2.1 Examples of eruptions at Pacaya and Fuego volcanoes ...................................... 17 Fig. 3.1 Methodology of CSD measurements – Part 1 ..................................................... 23 Fig. 3.2 Methodology of CSD measurements – Part 2 ..................................................... 24 Fig. 4.1 Microphotograph of sample PA-19 (N//) at 2.5x ................................................ 27 Fig. 4.2 Microphotograph of sample PA-19 (NX) at 2.5x ................................................ 28 Fig. 4.3 SEI image of sample PA-19 ................................................................................ 28 Fig. 4.4 Microphotograph of samples PA-44 and PA-49 (NX) at 2.5x ........................... 30 Fig. 4.5 Microphotograph of sample PA-49 (NX) at 2.5x ............................................... 31 Fig. 4.6 Microphotograph of samples PA-44 and PA-47 (NX) at 2.5x ........................... 32 Fig. 4.7 SEI image of sample PA-44 ................................................................................ 32 Fig. 4.8 X-ray elemental map of an area of sample PA-44 .............................................. 33 Fig. 4.9 Microphotograph of sample PA-27 (NX) at 2.5x ............................................... 34 Fig. 4.10 Microphotograph of sample PA-27 and PA-14 (NX) at 10x ............................ 35 Fig. 4.11 SEI images of sample PA-27 ............................................................................. 37 Fig. 4.12 Microphotograph of sample VF-74-130 (NX) at 10x ....................................... 38 Fig. 4.13 Microphotograph of samples VF-74-130a and VF-74-130c (NX) at 2.5x ....... 39 Fig. 4.14 X-ray elemental map of sample VF-74-130a .................................................... 40 Fig. 4.15 TAS diagram of the samples analyzed using SEM ........................................... 41 Fig. 4.16 Modal and petrographyc data for the samples .................................................. 43 Fig. 4.17 Distribution of disequilibrium textures in all the samples of different VEI ..... 44 5 Fig. 4.18 CSD for each sample analyzed ......................................................................... 45 Fig. 4.19 Comparative figure with all CSDs .................................................................... 46 Fig. 4.20 Viscosity vs. temperature plot for VEI 0 .......................................................... 47 Fig. 4.21 Vesiculation vs. viscosity diagram for each VEI .............................................. 49 Fig. 5.1 Geochemical comparison with previous work at Pacaya and Fuego .................. 51 Fig. 5.2 Evolution of mixing textures in plagioclase crystals with increasing in VEI ..... 52 Fig. 5.3 Evolution of mixing textures in olivine crystals with increasing in VEI ............ 53 Fig. 5.4 Mixing interpretations