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Fission-Track Geochronology and Geothermometry of Late Cretaceous-Early Tertiary Epizonal Plutons, in and Adjacent to the Lombard Thrust Fault, Southwestern Montana

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Fission-Track Geochronology and Geothermometry of Late Cretaceous-Early Tertiary Epizonal Plutons, in and Adjacent to the Lombard Thrust Fault, Southwestern Montana Western Michigan University ScholarWorks at WMU Master's Theses Graduate College 6-1988 Fission-Track Geochronology and Geothermometry of Late Cretaceous-Early Tertiary Epizonal Plutons, in and Adjacent to the Lombard Thrust Fault, Southwestern Montana Jean Talanda Follow this and additional works at: https://scholarworks.wmich.edu/masters_theses Part of the Geology Commons Recommended Citation Talanda, Jean, "Fission-Track Geochronology and Geothermometry of Late Cretaceous-Early Tertiary Epizonal Plutons, in and Adjacent to the Lombard Thrust Fault, Southwestern Montana" (1988). Master's Theses. 1202. https://scholarworks.wmich.edu/masters_theses/1202 This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. FISSION-TRACK GEOCHRONOLOGY AND GEOTHERMOMETRY OF LATE CRETACEOUS-EARLY TERTIARY EPIZONAL PLUTONS, IN AND ADJACENT TO THE LOMBARD THRUST FAULT, SOUTHWESTERN MONTANA by Jean Talanda A Thesis Submitted to the Faculty of the Graduate College in partial fulfillment of the requirements for the Degree of Master of Science Department of Geology Western Michigan University Kalamazoo, Michigan June 1988 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FISSION-TRACK GEOCHRONOLOGY AND GEOTHERMOMETRY OF LATE CRETACEOUS-EARLY TERTIARY EPIZONAL PLUTONS , IN AND ADJACENT TO THE LOMBARD THRUST FAULT, SOUTHWESTERN MONTANA Jean Talanda, M.S. Western Michigan University, 1988 Thrusting occurred in the central portion of the cen tral Montana sa lie n t where the timing of movements is somewhat obscured by the multiple deformations from Archean time to the present. The relationship of this thrusting to the associated plutons has not been established in every case. Fission-track geochronology was employed in dating several plutons associated with the Lombard thrust fault, consequently, defining a time range in which movement along the thrust occurred. Seven plutons with known structural relationships to the Lombard thrust have ages which suggest that movement along the fault occurred 73.2 +/-6.7 Ma. Fission-track length distributions suggest that all the plutons studied share a common thermal history. The distributions indicate that the plutons were brought to a shallow depth and cooled rapidly similar to undisturbed volcanic-type rocks. Therefore, the fission-track ages obtained in this study are very likely related to the actual crystallization of rocks. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AC KNOWLEDGEMENT S Matthew Fisher, my husband: Thanks for your support. Dorothy and Edmund Talanda, my parents: I hope this paper can appropriately reflect all that I have learned. Donald S. Miller, Chairman of the Geology Department at Rensselaer Polytechnic Institute (RPI); Ian R. Duddy, from the University of Melbourne, Australia; and, Raymond A. Donelick, RPI: They have given me their time and energy above and beyond th a t expected from any outside university. I truly appreciate their assistance. The su p p o rtin g s t a f f a t RPI; Mary Roden, C harles Kavanaugh and Clark Isachsen. I thank them for th e ir help. John D. Grace, W. Thomas Straw, Christopher J. Schmidt and Ronald B. Chase; Professors in the Geology Department at Western Michigan University (WMU) : This thesis has been a challenge. Thanks for helping me with the concept, the field work and lab equipment. My sincere gratitude to my other supporters: the Graduate Research Fund at WMU; the Awards and Fellowship Committee for a financial grant; the Department of Geology at WMU, for a financial award; the Carlson's, in Montana; Jerry Jones, for the Phoenix Memorial Reactor at U of M; Richard Berg at the Montana Bureau of Mines; and, the Michigan Department of Transportation, for their lab. Jean Talanda ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This reproduction was made from a copy of a document sent to us for microfilming. While the most advanced technology has been used to photograph and reproduce this document, the quality of the reproduction is heavily dependent upon the quality o f the material submitted. The following explanation of techniques is provided to help clarify markings or notations which may appear on this reproduction. 1.The sign or “target” for pages apparently lacking from the document photographed is “Missing Page(s)”. If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting through an image and duplicating adjacent pages to assure complete continuity. 2. When an image on the film is obliterated with a round black mark, it is an indication of either blurred copy because of movement during exposure, duplicate copy, or copyrighted materials that should not have been filmed. For blurred pages, a good image o f the page can be found in the adjacent frame. If copyrighted materials were deleted, a target note will appear listing the pages in the adjacent frame. 3. When a map, drawing or chart, etc., is part o f the material being photographed, a definite method of “sectioning” the material has been followed. It is customary to begin filming at the upper left hand comer o f a large sheet and to continue from left to right in equal sections with small overlaps. If necessary, sectioning is continued again—beginning below the first row and continuing on until complete. 4. For illustrations that cannot be satisfactorily reproduced by xerographic means, photographic prints can be purchased at additional cost and inserted into your xerographic copy. These prints are available upon request from the Dissertations Customer Services Department. 5. Some pages in any document may have indistinct print. In all cases the best available copy has been filmed. University M icrdrilm s International 300 N. Zeeb Road Ann Arbor, Ml 48106 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Order Number 1334666 Fission-track geochronology and geothermometry of Late Cretaceous-Early Tertiary epizonal plutons, in and adjacent to the Lombard thrust fault, southwestern Montana Talanda, Jean, M.S. Western Michigan University, 1988 Copyright ©1988 by Talanda, Jean. All rights reserved. UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark V . 1. Glossy photographs or pages ______ 2. Colored illustrations, paper or print _______ 3. Photographs with dark background _____ 4. Illustrations are poor copy _______ 5. Pages with black marks, not original co p y _______ 6. Print shows through as there is text on both sides of page _______ 7. Indistinct, broken or small print on several pages i / 8. Print exceeds margin requirements ______ 9. Tightly bound copy with print lost in sp in e ________ 10. Computer printout pages with indistinct print _______ 11. Page(s)____________ lacking when material received, and not available from school or author. 12. Page(s) seem to be missing in numbering only as text follows. 13. Two pages num bered . Text follows. 14. Curling and wrinkled pages ______ 15. Dissertation contains pages with print at a slant, filmed as received_ 16. Other _____________________________________________________________ Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Copyright by Jean Talanda 1988 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS ACKNOWLEDGEMENT ...................................................................................... i i LIST OF TABLES ........................................................................................ vi LIST OF FIGURES ...................................................................................... v ii CHAPTER I. INTRODUCTION .............................................................................. 1 The Problem ........................................................................ 1 II. GEOLOGICAL .................................................................................. 5 Lombard Thrust Fault ................................................... 6 Boulder Batholith Region ......................................... 7 I II . FISSION TRACK ANALYSIS ...................................................... 10 Problems Involved in Fission Tracking .......... 10 Effects of Other Fission Track Producing Isotopes ................................................ 12 Physical and Age Limitations of Apatite Crystals ..................................................... 13 Changes After Crystal Formation ................. 14 Laboratory Determinations
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