Table of Contents Abstract ................................................................................................................................................................ i Resume .............................................................................................................................................................. iii Acknowledgement ................................................................................................................................................v Chapter 01 - Introduction ..................................................................................................................................1 1.1 Overview ....................................................................................................................................................1 1.2 Tectonics and volcanism in the Philippines................................................................................................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 Volcano 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 Kanlaon 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 Biliran 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