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Comprehensive Analysis of Global Mid Ocean Ridge and Mariana

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Comprehensive Analysis of Global Mid Ocean Ridge and Mariana COMPREHENSIVE ANALYSIS OF GLOBAL MID OCEAN RIDGE AND MARIANA CONVERGENT MARGIN HYDROTHERMAL SYSTEMS TECTONICS, FLUID CHEMISTRY AND VENT BIOTA by Diluni Ayeshika Wimalaratne Hetti Pathirannehelage APPROVED BY SUPERVISORY COMMITTEE: ___________________________________________ Dr. Robert J. Stern, Chair ___________________________________________ Dr. Thomas Brikowski ___________________________________________ Dr. Juan Gonzalez ___________________________________________ Dr. Carlos Aiken Copyright 2020 Diluni Ayeshika Wimalaratne Hetti Pathirannehelage All Rights Reserved Through the trenches up to the ridges You made my journey a success … To my little Neth, Sachith, family, friends and mentors COMPREHENSIVE ANALYSIS OF GLOBAL MID OCEAN RIDGE AND MARIANA CONVERGENT MARGIN HYDROTHERMAL SYSTEMS TECTONICS, FLUID CHEMISTRY AND VENT BIOTA by DILUNI AYESHIKA WIMALARATNE HETTI PATHIRANNEHELAGE, BS, MS DISSERTATION Presented to the Faculty of The University of Texas at Dallas in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY IN GEOSCIENCES THE UNIVERSITY OF TEXAS AT DALLAS May 2020 ACKNOWLEDGMENTS I would like to thank Dr. Frank Konietschke and Asanka M. Gunawardana of the Department of Mathematical Sciences at the University of Texas at Dallas for their guidance in statistical analysis. April 2020 v COMPREHENSIVE ANALYSIS OF GLOBAL MID OCEAN RIDGE AND MARIANA CONVERGENT MARGIN HYDROTHERMAL SYSTEMS TECTONICS, FLUID CHEMISTRY AND VENT BIOTA Diluni Ayeshika Wimalaratne Hetti Pathirannehelage, PhD The University of Texas at Dallas, 2020 Supervising Professor: Robert J. Stern This study is a multidisciplinary data integration and metadata analysis for mid-ocean ridge (MOR) and Mariana intra oceanic convergent margin hydrothermal vents including fluids and biota. We compiled separate databases for MOR and Mariana hydrothermal vent parameters and their vent biota using published and on-line information managed by government agencies and other research institutes. The vent parameter databases are compiled under the categories of setting, vent field name, vent field number, name, latitude, longitude, alias, vent sites, smoker type and chimney 3 4 composition, host rocks, full spreading rate, depth, temperature, pH, total Fe, ( He/ He)/Ra, CO2, 2- CH4, H2, H2S, SO4 ions, chlorinity, operations and references. MOR database for vent parameters includes 449 individual hydrothermal vents grouped into 73 vent fields at global divergent margins. The vent organism database of MOR vents includes 672 species belong to 72 individual vents. Mariana vent summary database includes 47 individual hydrothermal vents belong to four different tectonic settings: the forearc (FAR), arc (ARC), backarc (BAB) and the southern Mariana trough (SMT). Database for Mariana biota include vent animals for 31 vents of the above settings. vi We considered vent depth, fluid temperature, pH, total Fe, Mn, helium isotopic ratio 3 4 2- (( He/ He)/Ra), fluid gases (CO2, CH4, H2, H2S), SO4 ions and chlorinity of the fluids for statistical analysis. In addition to these parameters, for MOR vents full spreading rate was also considered for statistical analysis. To overcome non-linear data distributions and small number of observations for some vent parameters, we used purely nonparametric statistical procedures. We assessed vent fluid parameters first for correlations with key parameters spreading rate (for MOR only), summit depth, fluid temperature and fluid chlorinity. Second, we compared different segments (MOR segments and Mariana tectonic settings) based on vent parameters. Similarities between the vent organisms in different tectonic segments were assessed using Sörensen similarity indices; for MOR vents at both genera and species levels; and for Mariana only for genus level. Our results for MORs show that even if MOR hydrothermal systems are associated with simple divergent margin tectonism, they are remarkably similar despite having differences in both fluid chemistry and biota distribution regardless of the ocean and the rate of spreading. Vent fluid 2- temperature, pH, Fe, Mn, CO2, H2, SO4 ion and chlorinity are independent of the spreading rate. Fluid temperature does control pH, Fe and H2S. Brine separation might influence gases such as helium isotopic ratio and CO2 in venting fluids. Highest similarities of the macro organisms are seen in the Indian Ocean ridges and the greatest differences are observed in the Pacific Ocean ridges. Integration of tectonics, fluid chemistry and vent biota of Mariana convergent margin vents demonstrate that Mariana vent groups are more diverse than global mid-ocean ridge vents and that the southernmost Marianas most resembles mid-ocean ridge (MOR) type venting, the other tectonic groups are quite different than MOR vents. vii TABLE OF CONTENTS ACKNOWLEDGMENTS ...............................................................................................................v ABSTRACT ................................................................................................................................... vi LIST OF FIGURES ....................................................................................................................... xi LIST OF TABLES ....................................................................................................................... xiv LIST OF ABBREVIATIONS ........................................................................................................xv CHAPTER 1: GLOBAL MID OCEAN RIDGE HYDROTHERMAL VENTS AND THEIR BIOTA 1.1. Abstract .........................................................................................................................1 1.2. Introduction ...................................................................................................................2 1.3. Geological Settings .......................................................................................................4 1.3.1. Pacific Ocean Spreading Ridges .........................................................................4 a. Juan de Fuca Ridge (JFR), Explorer Ridge (EXR), and Gorda Ridge (GOR) b. East Pacific Rise (EPR) c. Galapagos Spreading Center (GSC) 1.3.2. Atlantic and Arctic Ocean Spreading Ridges .....................................................8 a. Mid Atlantic Ridge (MAR), Reykjanes Ridge (RKR), Kolbeinsy Ridge (KOR), and Mohn’s Ridge (MHR) b. Mid Cayman Rise (MCR) c. Gakkel Ridge (GKR) 1.3.3. Indian Ocean Spreading Ridges ........................................................................10 a. Central Indian Ridge (CIR) viii b. Southwest Indian Ridge (SWIR) 1.4. Methods.......................................................................................................................11 1.4.1. Data Sources .....................................................................................................11 1.4.2. Statistical Analyses of Vent Parameters ...........................................................13 1.4.3. Statistical Analyses of Vent Biota ....................................................................15 1.5. Results .........................................................................................................................16 1.5.1. Analyses of Vent Parameters ............................................................................16 1.5.2. Similarity Analysis of Vent Biota……………………………………………..29 1.6. Discussion ...................................................................................................................30 1.6.1. Effect of Spreading Rate and Summit Depth on Hydrothermal Fluid………..30 1.6.2. Temperature and Chlorinity Controls on Fluid Compositions .........................32 1.6.3. Anomalous Fe and Chlorinity of Central Indian Ridge Vent Fluids ................34 1.6.4. Is geography the most important control on MOR vent biota? ........................34 1.7. Conclusions .................................................................................................................35 1.8. Acknowledgments.......................................................................................................35 1.9. Appendix A: Statistical analyses of fluid parameters and vent macro organisms in global mid ocean ridge hydrothermal system .............................................................36 1.10. References .................................................................................................................40 CHAPTER 2: A COMPILATION OF HYDROTHERMAL AND COLD-SEEP VENTS IN THE MARIANA CONVERGENT MARGIN: TECTONICS, FLUID CHEMISTRY AND BIOLOGY 2.1. Abstract .......................................................................................................................47 2.2. Introduction .................................................................................................................48 2.3. Geological Settings .....................................................................................................54 ix 2.4. Methods.......................................................................................................................56 2.4.1. Data Sources .....................................................................................................56 2.4.2. Statistical Analyses of Vent Parameters ...........................................................58 2.4.3. Statistical Analyses of Vent Biota ....................................................................60 2.4.4. Statistical Analysis of Chimney
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