MIAMI UNIVERSITY the Graduate School Certificate for Approving The
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MIAMI UNIVERSITY The Graduate School Certificate for Approving the Dissertation We hereby approve the Dissertation of Ninad R. Bondre Candidate for the Degree: Doctor of Philosophy William K. Hart, Director Craig M. White, Reader Elisabeth Widom, Reader Jason A. Rech Brian S. Currie Michael W. Crowder, Graduate School Representative ABSTRACT FIELD AND GEOCHEMICAL INVESTIGATION OF BASALTIC MAGMATISM IN THE WESTERN UNITED STATES AND WESTERN INDIA by Ninad R. Bondre This dissertation consists of three sub-projects, each of which integrates field and geochemical information to address specific questions pertaining to magmatism in three different continental basaltic provinces. It is expected that these sub-projects will contribute to a deeper understanding of various facets of basaltic magmatism. The first sub-project involves the Sangamner mafic dike swarm in the western Deccan Volcanic Province (DVP). This study, which is the first study of its kind from this province, uses a combination of field and geochemical characteristics to understand the relationship of the dikes with associated lava flows, and their position in the established Deccan stratigraphy. The results indicate that several dikes are geochemically similar to younger formations, and that NE-SW trending dikes in the central part of the area possibly represent a fissure system that could have fed lava flows of the Poladpur and / or Khandala formation. The second sub-project is the first attempt at integrating morphological, textural and compositional data to understand the emplacement of basaltic lava flows from the Steens Basalt in southeastern Oregon, and its eruptive history. The study reveals substantial morphological diversity within the Steens package. Typical compound pahoehoe flows are abundant – these were probably sourced from small to moderate-sized shield volcanoes, and grew as a network of overlapping, inflated lobes. Interbedded a’a and transitional flows suggest that physical parameters varied throughout the eruptive episodes. Geochemical data, in conjunction with morphological data hints at complex eruptive episodes that probably reflect complex processes at depth. These deserve to be investigated in greater detail. The final sub-project focuses on the newly-recognized Jordan Valley Volcanic Field (JVVF) in southeastern Oregon. An integration of field, geochemical and geochronologic information has been used to understand the evolution of this field through space and time, and to better understand the origin of other monogenetic volcano-fields. Salient results include the recognition of two major pulses of volcanism, long-lived vent alignments, and considerable chemical and isotopic diversity. This information is evaluated in terms of its implications for understanding issues pertaining to small-scale mantle heterogeneity, differentiation processes, and melt transport. FIELD AND GEOCHEMICAL INVESTIGATION OF BASALTIC MAGMATISM FROM THE WESTERN UNITED STATES AND WESTERN INDIA A DISSERTATION Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Geology by Ninad R. Bondre Miami University Oxford, Ohio 2006 Dissertation Director: William K. Hart, Ph.D. TABLE OF CONTENTS Chapter1: Introduction 1 References 4 Chapter 2: Geology and Geochemistry of the 5 Sangamner Mafic Dike Swarm, Western Deccan Volcanic Province, India: Implications for Regional Stratigraphy Abstract 5 Body Text 6 References 23 Chapter 3: Morphological and Textural Diversity of 49 the Steens Basalt Lava Flows, Southeastern Oregon, USA: Implications for Emplacement Style and Nature of Eruptive Episodes Abstract 49 Body Text 50 References 73 Chapter 4: Geology, Geochronology and Compositional 104 Diversity of The Jordan Valley Volcanic Field (JVVF), Southeastern Oregon: Implications for Small-Volume, Monogenetic Volcanism Abstract 104 Body Text 105 References 145 Chapter 5: Concluding Remarks and Suggestions for Future Work 205 Appendix 1: Analytical Methods 210 Appendix 2: Summary of Methods Used in Ar-Ar Geochronology 215 Appendix 3: Sample Locations and Descriptions 224 Appendix 4: Geochemical Data for Samples From the JVVF 243 ii LIST OF TABLES Chapter 2: Geology and Geochemistry of the 5 Sangamner Mafic Dike Swarm, Western Deccan Volcanic Province, India: Implications for Regional Stratigraphy 1 – Stratigraphic classification of the Southwestern Deccan 29 Volcanic Province 2 – Major and Trace Element Data for the Sangamner Samples 30 3 – Rare Earth Element and Isotopic Data for the 33 Sangamner Samples 4 – Results of Discriminant Function Analysis for the 34 Sangamner Samples Chapter 3: Morphological and Textural Diversity of 49 the Steens Basalt Lava Flows, Southeastern Oregon, USA: Implications for Emplacement Style and Nature of Eruptive Episodes 1 – Location and Approximate Stratigraphic Context of 80 Studied Steens Sections 2 – Major and Trace Element Data for the Steens Samples 81 Chapter 4: Geology, Geochronology and Compositional 104 Diversity of The Jordan Valley Volcanic Field (JVVF), Southeastern Oregon: Implications for Small-Volume, Monogenetic Volcanism 1 – Geochronologic Data for Selected Samples from the JVVF 156 2 – Major, Trace Element (including REE) and Isotopic Data for 157 Selected JVVF Samples 3 – Parameters Used in Fractional Crystallization Modeling Using 160 PELE Appendix 2: Summary of Methods Used in Ar-Ar Geochronology 215 1 – Age Data for the Dated JVVF Samples 216 Appendix 4: Geochemical Data for Samples From the JVVF 243 iii LIST OF FIGURES Chapter 2: Geology and Geochemistry of the Sangamner Mafic 5 Dike Swarm, Western Deccan Volcanic Province, India: Implications for Regional Stratigraphy 1 – DVP map with study area, principal flow types and principal dike 35 swarms 2 – Geological Map of the Sangamner Area 37 3 – Binary Plots involving elements and elemental ratios 39 4 – Results of Discriminant Function Analysis 41 5 – Primitive Mantle-Normalized Multi-element Patterns 43 6 – Chondrite-Normalized REE patterns 45 7 – Sr Isotopic Composition versus εNd 47 Chapter 3: Morphological and Textural Diversity of 49 the Steens Basalt Lava Flows, Southeastern Oregon, USA: Implications for Emplacement Style and Nature of Eruptive Episodes 1 – Steens Location Map 84 2 – Binary Plots that Help Determine Stratigraphic Context 86 3 – Measured Sections 88 4 – Field Photographs 90 5 – Field Sketches of Compound Pahoehoe Flows 92 6 – Field Sketches and Photograph of Pahoehoe Flow Lobes 94 7 – Photomicrographs Showing Textural Characteristics 96 8 – Field Sketches of A’a and Transitional Flows 98 iv 9 – Field Photographs of A’a Flows 100 10 – Binary Plots that Link Morphology and Texture with Composition 102 Chapter 4: Geology, Geochronology and Compositional 104 Diversity of The Jordan Valley Volcanic Field (JVVF), Southeastern Oregon: Implications for Small-Volume, Monogenetic Volcanism 1 – Regional Context of the JVVF 161 2 – Satellite Image of the JVVF with Locations of Vents and Vent 163 Alignments 3 – Simplified Geological Map of the JVVF 165 4 – Total Alkalis vs. Silica Diagram and Plot of Zr/TiO2 vs. Nb/Y 167 5 – Binary Plots of SiO2, TiO2, Al2O3 and Total Alkalis vs. Mg number 169 6 – MgO*0.5-K2O*5-TiO2*1.5 Triangular Diagram Showing Principal 171 Magma Types 7 – Binary Plots of Sr, Nb, Rb and Zr vs. TiO2 Revealing Two 173 Principal Groups 8 – Chondrite-Normalized REE diagram 175 9 – Sr vs. Nd Isotopic Compositions 177 10 – Pb Isotopic Compositions 179 11 – Sr and Nd Isotopic Compositions vs. Pb Isotopic Composition 181 12 – Satellite Image Showing the Spatial and Temporal Context of 183 Geochemical Data 13 – Binary Plots Showing Salient Characteristics of Groups 1 and 2 185 14 – Nd Isotopic Composition and Zr vs. Age 187 15 – Results of Batch Partial Melting Modeling of REE for HAOT 189 Generation 16 – La/Sm(N) and Sm/Yb(N) vs. TiO2 Indicating Depth of Melting 191 v 17 – Al-Factor and CaO/Al2O3 vs. Fe-Factor Indicating Depth of 193 Crystallization and Phases Involved 18 – Results of Modeling of Deep Fractional Crystallization of JC-30B 195 19 – Results of Binary Mixing Between Fraction Derived from JC-30B 197 and Melt of Rhyolitic Composition 20 – Results of Binary Mixing Between HAOT (Cow Vent Complex) 199 and SROT-like (V 4569) compositions 21 – End-member Plumbing System Scenarios for Monogenetic 201 Volcano-Fields 22 – Diagram for Conceptualizing Important Parameters in 203 Monogenetic Volcanism Appendix 2: Summary of Methods Used in 40Ar-39Ar 215 Geochronology 1-7 – Plateau/Isochron Plots for the Dated JVVF Samples 217- 223 Appendix 4: Geochemical Data for Samples From the JVVF 243 1 – JVVF Sample Locations on Satellite Image 252 vi ACKNOWLEDGEMENTS It gives me great pleasure to be able to explicitly express a deep sense of gratitude towards everyone that was involved in this dissertation, either directly or indirectly. Right at the outset, I apologize to those whom I might have inadvertently forgotten to acknowledge here. The support and guidance of a number of people was instrumental in the successful completion of this research. My advisor, Bill Hart leads this list. Bill was gracious enough to accept me into his research group and introduce me to the fascinating geology of the northwestern United States. I have learnt immensely from the numerous stimulating discussions that we have had for the past four years and thoroughly enjoyed our time together in the field. He deserves a great deal of credit for initiating me into the world of geochemical analysis and interpretation