Physical and chemical evolution of Cracked Mountain glaciovolcano, SW British Columbia
department or school: Science, Faculty of
department or school: Earth, Ocean and Atmospheric Sciences, Department of
data provider: DSpace
degree campus: UBCV
creator: Harris, Martin Alexander
issued: 2021-12-07T21:38:46Z
issued: 2021
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: The focus of this thesis is Cracked Mountain Volcano, located in the Garibaldi volcanic belt (GVB), of southwestern British Columbia, Canada. This study investigates the physical and petrochemical evolution of Cracked Mountain. Field mapping, lithostratigraphy, petrography, geochemistry, and thermodynamics were used to model: i) the eruptive sequence, style, duration, and paleoenvironment, ii) the causes of petrochemical variation and the P-T-H2O contents for the Cracked Mountain magmas. The major findings show that Cracked Mountain has a glaciovolcanic origin. We find lapilli tuffs consistent with a phreatomagmatic (i.e. explosive) origin, followed by intrusions (dykes, peperites) and effusions (pillows, sheet-lavas), indicating a transitional eruptive style. Paleomagnetic directions record a single-pole direction (i.e. monogenetic eruption). The edifice morphology indicates syn-eruptive confinement by a paleo-ice sheet that was  850 m thick, capable of holding a ‘leaky’ paleolake system with a maximum of ~0.36 km3 of water. The glaciovolcanic (40Ar/39Ar) age of ~400 ka represents an important record of the Cordilleran Ice sheet (CIS) in southwestern BC during the mid-Pleistocene. Petrographically, Cracked Mountain volcanic rocks comprise two unique suites: i) an olivine-plagioclase phyric (OP) assemblage and ii) an olivine-plagioclase-augite phyric (OPA) assemblage. Thermodynamic modeling based on Rhyolite-MELTS (Gualda and Ghiorso, 2015) reveals that these differences in phenocryst assemblage require distinct storage conditions before the eruption. OP magma must have been stored at depths less than 6 km (<2 kbar) and temperatures of 1240-1155 ̊ C. In contrast, OPA magmas crystallized at depths between 7-9 km (~2-2.5 kbar) at 1250-1150 ̊ C. Both magmas contained ≤ 0.5 H2O wt.% in their respective systems. Incompatible elements show no significant chemical differences between the two petrographic suites, indicating a singular melt source. Detailed analysis of vari…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/80391
note: PHYSICAL AND CHEMICAL EVOLUTION OF CRACKED MOUNTAIN GLACIOVOLCANO, SW BRITISH COLUMBIA by Martin Alexander Harris B.Sc., The University of Oregon, 2017 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Geological Sciences) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) December 2021 © Martin Alexander Harris, 2021 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the thesis entitled: PHYSICAL AND CHEMICAL EVOLUTION OF CRACKED MOUNTAIN GLACIOVOLCANO, SW BRITISH COLUMBIA Submitted by Martin Alexander Harris in partial fulfillment of the requirements for the degree of Master of Science in Geological Sciences. Examining Committee: James K. Russell, Professor, Department of Earth, Ocean, and Atmospheric Sciences, UBC Supervisor Dominique Weis, Professor, Department of Earth, Ocean, and Atmospheric Sciences, UBC Supervisory Committee Member Lucy Porritt, Lecturer and Research Associate, Department of Earth, Ocean, and Atmospheric Sciences, UBC Supervisory Committee Member Lee Groat, Professor, Department of Earth, Ocean, and Atmospheric Sciences, UBC Additional Examiner iii Abstract The focus of this thesis is Cracked Mountain Volcano, located in the Garibaldi volcanic belt (GVB), of southwestern British Columbia, Canada. This study investigates the physical and petrochemical evolution of Cracked Mountain. Field mapping, lithostratigraphy, petrography, geochemistry, and thermodynamics were used to model: i) the eruptive sequence, style, duration, and paleoenvironment, ii) the causes of petrochemical variation and the P-T-H2O contents for the Cracked Mountain magmas. The major findings show that Cracked Mountain has a glaciovolcanic origin. We find lapilli tuffs consistent with a phreatomagmatic (i.e. explosive) origin, followed by intrusions (dykes, peperites) and effusions (pillows, …
has type: Thesis/Dissertation
date issued: 2022-05
is shown at: 10.14288/1.0404505
language: eng
degree discipline: Geological Sciences
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
contributor: Russell, J. K. (J. Kelly)
type: Text
identifier URI: http://hdl.handle.net/2429/80391