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Petrology of the Hastingsite-Riebeckite Granite of Mt. Cabot, NH Colin Robert Kraft Bates College, [email protected]

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Petrology of the Hastingsite-Riebeckite Granite of Mt. Cabot, NH Colin Robert Kraft Bates College, Ckraft@Bates.Edu Bates College SCARAB Standard Theses Student Scholarship 5-2017 Petrology of the hastingsite-riebeckite Granite of Mt. Cabot, NH Colin Robert Kraft Bates College, [email protected] Follow this and additional works at: http://scarab.bates.edu/geology_theses Recommended Citation Kraft, Colin Robert, "Petrology of the hastingsite-riebeckite Granite of Mt. Cabot, NH" (2017). Standard Theses. 37. http://scarab.bates.edu/geology_theses/37 This Open Access is brought to you for free and open access by the Student Scholarship at SCARAB. It has been accepted for inclusion in Standard Theses by an authorized administrator of SCARAB. For more information, please contact [email protected]. Petrology of the Hastingsite-Riebeckite Granite of Mt. Cabot, New Hampshire A Senior Thesis Presented to The Faculty of the Department of Geology Bates College In partial fulfillment of the requirements for the Degree of Bachelor of Science By Colin Kraft Lewiston, Maine April 7, 2017 Acknowledgements I would like to thank my advisor Professor Geneviève Robert for her guidance and feedback during the whole thesis project. Her knowledge, expertise, and consistent push allowed me to deeply understand my topic and foster a love for igneous petrology. This summer could not have been possible without the help from Professor Dyk Eusden and fellow classmate Ian Hillenbrand. I would like to thank Professor Dyk Eusden for the opportunity to work on this project and the help he gave during the data collection and field season period. I would also like to thank you my other field partner, Ian Hillenbrand, for showing me how to navigate GIS and helping me create the mineralogical and textural maps. I am incredibly grateful for the time the Greg Anderson spent helping me learn the correct way to use the SEM-EDS for my thin sections. Unfortunately, I did not get far enough in the process to include the results in my thesis but I will treasure the information. Special thanks to David Gibson and his lab assistants for analyzing my rock sample for XRF data at their laboratory at the University of Maine- Farmington. To the rest of the geology department: Mike Retelle, Beverly Johnson, Marita Bryant, Raj Saha, Phil Dostie, and the visiting professors, thank you for inspiring me throughout my studies in geology. Thank you to all my friends and fellow geology students who have made these four years a blast every step of the way A special thanks to my family for supporting me every step of the way and for allowing me the opportunity to be where I am today. ii Table of Contents Acknowledgements ii Table of Contents Error! Bookmark not defined. Table of Figures iii Table of Tables vii Abstract viii Introduction 10 1.1 Study Area 10 1.2 Tectonic History 12 1.3 Ring Dike and Caldera Collapse 20 1.4 Focus Area Geology 22 1.5 Previous Studies 25 1.6 The White Mountain Magma Series 28 1.7 Similar Peralkaline Granites 35 1.8 Amphiboles 42 1.9 Purpose 48 Methods 49 2.1 Field Methods 49 2.2 Labratory Methods 50 2.3 Analytical Methods 51 Results 55 3.1 Mt. Cabot Granite Lithology Descriptions 55 3.2 Sample 52 Geochemistry 83 Discussion 4.1 General Crystallization Order of Plutonic Minerals 86 iii 4.2 Conditions for Perthite Formation 89 4.3 Indicators for Parental Magma Composition 91 4.4 Origins of Intergranular Albite and Hydrothermal Alterations 96 4.5 Relation to Other New Hampshire Igneous Plutons 98 4.6 Proposed Petrogenic Model and Conclusions 100 References 103 iv Table of Figures Figure 1.1: Geologic map of Pliny region and Mt. Cabot pluton region (Hillenbrand 2017).......11 Figure 1.2: Cross sectional view of Taconic orogenic events. From top to bottom: (a) Taconic 1, (b) Taconic 2 (Van Staal et al., 2009)................................................................................14 Figure1.3: (a) Taconic 2, and (b) Taconic 3 (Van Staal et al., 2009)...........................................15 Figure 1.4: Acadian-Neoacadian orogeny (Hatcher, 2010). .........................................................17 Figure 1.5: Alleghanian orogenic events (Hatcher, 2010).............................................................19 Figure1.6: Caldera collapse and the formation of ring dikes (Kennedy and Stix, 2007)..............................................................................................................................................21 Figure1.7: Map of ring dike complexes in New Hampshire (Chapman, 1942)..............................................................................................................................................23 Figure 1.8: Modified New Hampshire State Bedrock Map (Lyons et al., 1997)..........................24 Figure 1.9: White Mountain igneous province (Eby and Creasy, 1993).......................................29 Figure 1.10: Correlation of magmatism with North Atlantic rifting and spreading during the Mesozoic era (McHone and Butler, 1984).........................................................................31 Figure 1.11: Simplified geology of the White Mountain batholith (Eby et al., 1992)...................34 Figure 1.12: Granitic rocks at Sharm El-Sheikh area, Egypt (Sherif et al., 2013)................................................................................................................................. 38 Figure 1.13: Distribution of alkalic plutons of southern New England (Lyons and Krueger, 1976)..................................................................................................................................40 Figure 1.14: Genesis of the Hastingsite group and riebeckite amphibole. Billings (1928).............................................................................................................................................47 Figure 2.1: XRF process of creating X-ray fluorescence (Bruker, 2016)......................................54 Figure 3.1: (A) Sample 52 (B) Sample 61 (b) Sample 104 (c) Sample 165..................................56 Figure 3.2: APQ classification of Mt Cabot samples....................................................................58 Figure 3.3: Unaltered and chemically altered riebeckite...............................................................61 Figure 3.4: Typical albite rimming of a sample.............................................................................62 Figure 3.5: Albite rimming and penetration within the perthite grains.........................................63 Figure 3.6: Prevalent intermingling of subhedral perthite and quartz grains................................64 v Figure 3.7: Subhedral perthite and quartz grains with uneven and broken boundaries.................67 Figure 3.8: Hastingsite light green and green pleochroic nature. Limonite and opaque mineral weathering is prevalent......................................................................................................68 Figure 3.9: Intergranular albite penetrating the anhedral perthite grains.......................................69 Figure 3.10: Sericitization of the feldspars with larger quartz crystals and broken up anhedral perthite grains.....................................................................................................................70 Figure 3.11: Only instance of horneblende in all the samples. Sericitization of the feldspar is prevalent.............................................................................................................................71 Figure 3.12: Subpoikilitic riebeckite engulfing a large euhedral perthite grain............................74 Figure 3.13: Two differently oriented riebeckite crystals with light clean to dark blue pleochroism....................................................................................................................................75 Figure 3.14: Close-up of albite rims on subhedral perthite grains.................................................76 Figure 3.15: Zoomed out example of albite rims and minor albite penetration within perthite grains..................................................................................................................................77 Figure 3.16: Prevalent albite riming between perthite-perthite boundaries...................................80 Figure 3.17: Large poikilitic grain of riebeckite............................................................................81 Figure 3.18: Only example of visible myrmekite texture in all of the rock samples.....................82 Figure 4.1: Crystallization timeline with some key conditions for amphibole formation.............88 Figure 4.2: Typical System phase diagram for alkali feldspar forming in hypersolvus granite under 5 kbar of pressure (Perkins and Brady, 2017).........................................................90 Figure 4.3: Mineralogical map of the Mt. Cabot hastingsite-riebeckite pluton.............................93 Figure 4.4: Evolution of the hastingsite group and riebeckite amphibole.....................................94 Figure 4.5: Magmatic evolution of the composition of magma melt and associated amphibole formation (Griet et al., 1980).........................................................................................................95 Figure 4.6: Geochemical data from Eby et al. (1992) and sample 52 from the Mt. Cabot region............... ............................................................................................................................99 vi Table of Tables Table 3.1: The APQ and amphibole percentages of each sample
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