Table of Contents Abstract ...... i Resume ...... iii Acknowledgement ...... v Chapter 01 - Introduction ...... 1

1.1 Overview ...... 1 1.2 Tectonics and volcanism in the ...... 4 1.3 State of the Art ...... 4 1.3.1 What is a hydrothermal system? ...... 4 1.3.2 Immature hydrothermal system ...... 7 1.3.3 Mature hydrothermal system ...... 9 1.3.4 Composition of fluids ...... 9 1.3.5 Isotopic composition ...... 13 1.3.5.1 Sulfur isotopes ...... 13 1.3.5.2 Deuterium and oxygen isotopes ...... 14 1.4 monitoring ...... 16 1.5 Objectives of the study ...... 18 Chapter 02 - Methods ...... 20

2.1 Sample collection ...... 20 2.2 Analytical work ...... 22 2.2.1 High-performance ion -exchange chromatography ...... 22 2.2.2 Inductively Coupled Plasma- Optical Emission Spectrometry ...... 23 2.2.3 Elemental Analysis-Isotope Ratio Mass Spectrometry ...... 24 Chapter 03 – Geochemical studies of thermal waters from Volcano, Negros Islands, Philippines ...... 26

Abstract...... 26 3.1 Introduction ...... 28 3.2 Volcano tectonic setting and previous work ...... 28 3.3 Eruptive history of Kanlaon Volcano ...... 29 3.4 Sampling and analytical methods ...... 31 3.5 Results ...... 33 3.5.1 Composition of thermal waters ...... 33 3.5.2 Sulfur isotopic composition of thermal waters ...... 34 3.5.3 Alteration minerals at Mambucal ...... 36 3.6 Discussion ...... 36 3.6.1 Origin of thermal waters ...... 36 3+ 3.6.2 Behavior of Iron (Fetot) and Aluminum (Al ) in the hydrothermal system ...... 43 3.6.3 Mineral saturation state of Kanlaon thermal waters ...... 44 3.6.4 Temporal variation in springs at Kanlaon Volcano ...... 46 3.6.5 Proposed geochemical model of the magmatic-hydrothermal system of Kanlaon Volcano ...... 48 3.7 Conclusion ...... 49 Chapter 04 – The magmatic-hydrothermal system of Volcano, Biliran Province, Philippines ....50

4.1 Introduction ...... 50 4.2 Geologic setting and eruptive history ...... 51 4.3 Previous work ...... 54 4.4 Methods ...... 55 4.4.1 Sample locations ...... 55 4.4.2 Field measurements ...... 55 4.4.3 Analytical techniques ...... 55 4.5 Results ...... 59 4.6 Discussion ...... 63 4.6.1 Origin of the different hydrothermal springs in Biliran Volcano ...... 63 4.6.2 Application of Na-K-Mg-Ca geothermometers ...... 68 4.6.3 Isotopic composition of the hydrothermal springs ...... 70 4.6.3.1 Sulfur isotopes ...... 70 4.6.3.2 Hydrogen and Oxygen isotopes ...... 72 4.7 Proposed geochemical model of the magmatic-hydrothermal system of Biliran Volcano ...... 74 4.8 Conclusions and recommendations ...... 77 Chapter 05 – Major element composition of the springs at Mt. Bulusan, Sorsogon Province,

Philippines ...... 79

5.1 Introduction ...... 79 5.2 Background ...... 81 5.2.1 Geologic setting ...... 81 5.2.2 History of Bulusan Volcanic Complex (BVC) ...... 81 5.2.3 Eruptive history of Mt. Bulusan ...... 82 5.3 Previous work ...... 85 5.4 Methods ...... 87 5.4.1 Samples and measurements ...... 87 5.4.2 Analytical techniques ...... 87 5.5 Results ...... 87 5.6 Discussion ...... 90 5.6.1 Origin of the hydrothermal springs in Mt. Bulusan ...... 90

vii 5.6.2 Saturation Index ...... 95 5.7 Proposed geochemical model of the magmatic-hydrothermal system of Mt. Bulusan ...... 98 5.8 Conclusion ...... 98 Chapter 06 – General Conclusion...... 101

References ...... 104 Appendix A – List of Figures ...... 117 Appendix B – List of Tables ...... 123

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