The 1996 Eruption Of Karymsky Volcano, Kamchatka: Detailed Petrological Study Of A Single Basalt -Triggered Eruption Cycle Item Type Thesis Authors Izbekov, Pavel Edgarovich Download date 06/10/2021 11:34:21 Link to Item http://hdl.handle.net/11122/8615 INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted.Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand corner and continuing from left to right in equal sections with small overlaps. ProQuest Information and Learning 300 North Zeeb Road, Ann Arbor, Ml 48106-1346 USA 800-521-0600 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THE 1996 ERUPTION OF KARYMSKY VOLCANO. KAMCHATKA: DETAILED PETROLOGICAL STUDY OF A SINGLE BASALT-TRIGGERED ERUPTION CYCLE A THESIS Presented to the Faculty of the University of Alaska Fairbanks in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Pavel Edgarovich Izbekov Fairbanks, Alaska December 2002 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3071429 UMI UMI Microform 3071429 Copyright 2003 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THE 1996 ERUPTION OF KARYMSKY VOLCANO, KAMCHATKA: DETAILED PETROLOGICAL STUDY OF A SINGLE BASALT-TRIGGERED ERUPTION CYCLE By Pavel Edgarovich Izbekov RECOMMENDED: t *■1— / “ ir Advisory Committee Chair^ Department Head APPROVED: tCc&ta UL Dean,College of Science, Engineering and Mathematics Dean of the Graduate School -iJj - Date Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract The current activity at Karymsky Volcano, Kamchatka, began on January 2, 1996, with simultaneous eruptions from two vents located 6 km apart: Karymsky summit vent, which erupted andesite, and a newly formed vent within Academy Nauk caldera, which erupted basalt. Detailed petrologic study of volcanic ash, bombs, and lavas of Karymsky erupted during 1996-1999 provides evidence for basaltic replenishment at the beginning of the eruptive cycle, as well as a record of compositional variations within the Karymsky magma reservoir induced by basaltic recharge. Shortly after the beginning of eruption the composition of matrix glasses of Karymsky tephra became more mafic, and then, within two months, gradually returned to its original state and remained almost constant the following three years. Further evidence for basaltic replenishment includes the presence of xenocrysts of basaltic origin in andesites erupted from Karymsky. A conspicuous portion of plagioclase phenocrysts in Karymsky andesites contain calcic cores, the composition and texture of which mimic those in Academy Nauk basalt. The earlier portions of andesite also contain rare xenocry sts of olivine, which occur as relicts in plagioclase-pyroxene aggregates. The compositions of olivine xenocrysts match those of olivines in Academy Nauk basalt. Compositional variations of glass and the presence of xenocrysts indicate that Karymsky magma reservoir was recharged by basalt at the onset of the 1996 eruptive cycle. The mixing of basalt with host andesite was both thorough and rapid, perhaps due to a modest contrast in temperature, viscosity, and density between the magmas. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Academy Nauk basalt contains granophyre xenoliths. the whole-rock compositions of which are identical to that of dacites erupted twice at 40.000 yr. BP and 7,900 yr. BP. and formed the neighboring Academy Nauk and Karymsky calderas. According to hydrothermal experiments and petrologic observ ations both dacites last equilibrated at 3-4 km depth. At the same depth granophyre phase assemblage is reproduced by isobaric cry stallization of dacites, thus implying that the granophyres represent a crystallized silicic reservoir, which produced dacites 40.000 yr. BP and formed Academy Nauk caldera. In 1996 this cry stallized body was sampled by ascending basalt, which erupted in the northern part of the caldera. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V Table of Contents Abstract ........................................................................................................................................... iii Table of Contents .......................................................................................................................... v List of Figures.............................................................................................................................. ix List of Tables ................................................................................................................................ xi List of Appendices...................................................................................................................... xii Acknowledgments ....................................................................................................................... xiii CHAPTER 1. INTRODUCTION........................................................................................... 1 CHAPTER 2. 1996 ERUPTION OF KARYMSKY VOLCANO. KAMCHATKA: HISTORICAL RECORD OF BASALTIC REPLENISHMENT OF AN ANDESITE RESERVOIR .............................................................................................................................. 4 A bstract ........................................................................................................................... 4 Introduction.................................................................................................................... 5 Geologic setting............................................................................................................ 7 Karymsky volcano........................................................................................... 7 Academy Nauk caldera................................................................................. 9 1996 eruption of Karymsky and Academy Nauk ................................................... 9 Samples and analytical methods................................................................................ 12 Petrography and mineralogy of Academy Nauk basalt ........................................ 14 Groundmass and melt inclusions................................................................ 15 Plagioclase....................................................................................................... 16 Pyroxenes.......................................................................................................... 17 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VI O livin e............................................................................................................... 17 M agnetite........................................................................................................... 17 Petrography and mineralogy of Karymsky andesite.............................................. 18 Groundmass and melt inclusions.................................................................. 18 Plagioclase........................................................................................................ 20 P yroxenes........................................................................................................... 21 O livin e............................................................................................................... 22 M agnetite........................................................................................................... 22 D iscussion ....................................................................................................................... 23 Origin o f variation o f Kar\ msk\ melt composition ................................. 23 Origin of calcic plagioclase and olivine in Karymsky andesites 25 Mechanism of mixing at Karymsky magma system................................. 27 C onclusion ...................................................................................................................... 32 Acknowledgements ........................................................................................................ 33 CHAPTER 3. CALCIC CORES