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Effects of Basalt Intrusion on the Multi-Phase Evolution of the Jemez Volcanic Field, New Mexico

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Effects of Basalt Intrusion on the Multi-Phase Evolution of the Jemez Volcanic Field, New Mexico UNLV Retrospective Theses & Dissertations 1-1-2003 Effects of basalt intrusion on the multi-phase evolution of the Jemez volcanic field, New Mexico Leigh Justet University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Justet, Leigh, "Effects of basalt intrusion on the multi-phase evolution of the Jemez volcanic field, New Mexico" (2003). UNLV Retrospective Theses & Dissertations. 2549. http://dx.doi.org/10.25669/gjly-fy1p This Dissertation is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Dissertation in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Dissertation has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. EFFECTS ()i;]3k\jSV\I,Tr]3SrrTllJ:SIC)t4 ON THE MULTI-PHASE EVOLUTION OF THE JEMEZ VOLCANIC FIELD, NM by Leigh Justet Bachelor of Science lJnbM%atyofFk%mda,Las)A%pB 1996 Master of Science Lhuvenw^fofbknnKk^IjsT/egas 1999 A dhaeüadansubnnËedinpan&ü fulfillment ofthenxphnanaüsfbrÜK Doctor of Philosophy in Geoscience Department of Geoscience College of Sciences Graduate College University of Nevada, Las Vegas December 2003 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 3115889 INFORMATION TO USERS 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 bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send 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. UMI UMI Microform 3115889 Copyright 2004 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. Dissertation Approval IINTV The Graduate College University of Nevada, Las Vegas November 25 _,2003 The Dissertation prepared by Leigh Justet_____ Entitled Effects of Basalt Intrusion On The Multi-Phase Evolution Of The Jemez Volcanic Field, New Mexico is approved in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geoscience__________________ Examimtion Committee Chair /"V f Dean of the Graduate College Examination Committee Member Examination Com mitte^i Grai ■acj 'resentative PS/1017-52/1-00 ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Effects of basah intrusion on the multiphase evolution of the Jemez volcanic Geld, NM by Leigh Justet Dr. Terry L. Spell, Examination Committee Chair Associate Professor of Geoscience University of Nevada, Las Vegas Analysis of ^Ar/^^Ar age, m^or/trace element geochemical, and Nd and Sr isotopic data indicates that the Jemez volcanic Geld, a long-lived continental volcanic center located at the intersection of the Rio Grande riA and Jemez Lineament in northern New Mexico, evolved in a complex two-phase maimer. The Jemez volcanic Geld evolved two -3.8 m.y.-long pulses of volcanic activity separated by a -2.2 m.y. period of eruptive quiescence. Each eruptive phase is composed of: (1) an initial -2 Ma period of intense volcanic acGvity dominated by basalGc and andesiGc composiGons that formed by variable amounts of mixing between lithospheric manüe-derived basalt and lower crustal melts; (2) followed by a 0.3 to 0.8 m.y. period of eruptive quiescence; (3) and culminating in the erupGon of ihyolite magmas Gom large, shallow silicic systems that formed by the contaminaGon of lower crustal melts by lithospheric manGe-derived basalt. This two phase model stands in contrast to the convenGonal view that long-Gved continental volcanic centers simply evolve in an iiuGal protracted interval of maGc in Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. enqrdons that culminate in the formation of a large silicic system. ComposiGonal and enqrtive Gming trends predicted by models simulating basalGc intrusion into the lower crust (Annen and Sparks, 2002) imply that the Jemez volcanic Geld's evolution was likely controlled by several factors in addidon to the presence or absence of fault conduits as proposed by Gardner (1985) and Gardner and Goff (1984). The basalt intrusion model implies that the thermal eSects of modest constant basalt intrusion rates produces a diversity of magma composidons and intervals of erupdve quiescence as seen in the Jemez volcanic Geld. IV Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ABSTRACT..................................................................................................................... iü UST OF TABLES......................................................................................................... viii LISTOFHGURES.......................................................................................................... ix ACKNOWLEDGEMENTS............................................................................................. xi CHAPTER 1 INTRODUCTION......................................................................................1 The Problem .............................................................................................................. 1 Objectives and Methods ............................................................................................3 Tectonic Setting ........................................................................................................5 Geologic Units Composing the Jemez Volcanic Field .............................................8 Previous Interpretations of the Jemez Volcanic Field .............................................10 CHAPTER 2 REVISED GEOCHRONOLOGY OF THE JEMEZ VOLCANIC FIELD......................................................................................................... 13 Summary of Previous Geochronologic Work......................................................... 14 ^Ar/^^Ar Results..................................................................................................... 15 ReGned Geochronology of the Jemez Volcanic Field Based on ^Ar/^Ar Dating......................................................................................................24 Comparison between ^Ar/^^Ar and K/Ar Ages in the Jemez Volcanic Field 31 Implications for the EvoluGon of the Jemez Volcanic Field ...................................32 CHAPTER 3 REVISED GEOCHEMISTRY OF THE JEMEZ VOLCANIC FIELD.........................................................................................................35 Summary of Data by PetrogeneGc Group.............................................................. 42 15.4 Ma........................................................................................................ 42 12.4 to 10.5 Ma.............................................................................................42 9.8 to 7.9 Ma ................................................................................................ 48 7.5 to 6.0 Ma.................................................................................................53 3.8 to 2.1 Ma .................................................................................................55 1.85 Ma to 50 ka..........................................................................................58 CHAPTER 4 PETROGENETIC INTERPRETATIONS................................................60 Explaining the Chemical VariaGon of Plagioclase Phenocrysts .............................61 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Explaining the Isotopic Variation of Jemez Rocks ................................................ 64 Composition of the Mande and Lower Crust .............................................. 64 Simple Mixing Models ................................................................................ 64 Explaining 6 e Trace Element Variability of Jemez Rocks ................................... 67 Composition of the Mantle and Lower Crust .............................................. 67 Source of Jemez MaGc and Felsic End Members ....................................... 68 Reconciling FracGonal CrystallizaGon Models with the Isotopic Data .......................................................................................... 74 Revised Petrogenesis of the Jemez Volcanic Field ................................................ 79 Comparison of the Revised Petrogenesis and Previous Work ............................... 81 ViabiGty of the Fault Conduit Model ....................................................................
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