Attrition of mantle cargo during kimberlite ascent : insights from analogue experiments
department or school: Science, Faculty of
department or school: Earth, Ocean and Atmospheric Sciences, Department of
data provider: DSpace
degree campus: UBCV
creator: Sasse, David
issued: 2020-01-03T23:27:03Z
issued: 2019
related degree: Master of Science - MSc
degree grantor: University of British Columbia
description: Kimberlite magmas transport mantle cargo in the form of xenoliths and xenocrysts to the surface of the Earth. Due to the lack of recent kimberlite eruptions and unanswered questions concerning melt composition and magma rheology, the mechanisms supporting efficient ascent of these cargo-rich magmas remains enigmatic. Although olivine is the dominant mineral phase in kimberlite, given the polymineralic nature of mantle xenoliths, xenocrysts are transported as a multi-mineral mixture. Within the ascending dyke, high particle concentrations and high velocities resulting in turbulent flow provides an environment for frequent particle-particle interaction. Xenocryst morphologies, textures and size distributions observed in kimberlite deposits are not reflective of how they occur in xenoliths and are therefore modified during ascent to the surface. The degree of modification of each mineral varies and is a function of its chemical and physical properties. Here I present a series of analogue attrition experiments on the mantle minerals: olivine, orthopyroxene, clinopyroxene, garnet and diamond designed to inform on the ascent of kimberlite magmas. Data is collected on particle size distributions, particle morphologies and particle velocities. Natural xenocrysts extracted from coherent kimberlite reveal remarkably similar surface features and morphologies to that of the experiments suggesting that attrition indeed operates during kimberlite ascent. Kimberlite ascent velocities are estimated by using a scaling analysis of the experiment conditions and by investigating impact pits observed on the surfaces of kimberlitic olivine and garnet xenocrysts. Both methods result in calculated ascent velocities of ~ 4 m s-1. In mineral mixtures, cleavage is shown to be a controlling factor in determining attrition rates whereby minerals with cleavage undergo accelerated breakdown. I suggest that the accelerated breakdown of orthopyroxene increases assimilation rates, contributing to th…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/73096
note: ATTRITION OF MANTLE CARGO DURING KIMBERLITE ASCENT: INSIGHTS FROM ANALOGUE EXPERIMENTS by DAVID SASSE B.Sc., The University of British Columbia, 2016 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 2019 © David Sasse, 2019 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, a thesis entitled: Attrition of mantle cargo during kimberlite ascent: Insights from analogue experiments submitted by David Sasse in partial fulfillment of the requirements for the degree of Master of Science in Geological Sciences Examining Committee: James Kelly Russell, Geological Sciences Supervisor Thomas Jones, Geological Sciences Supervisory Committee Member Maya Kopylova, Geological Sciences Supervisory Committee Member Lucy Porritt, Geological Sciences Additional Examiner iii Abstract Kimberlite magmas transport mantle cargo in the form of xenoliths and xenocrysts to the surface of the Earth. Due to the lack of recent kimberlite eruptions and unanswered questions concerning melt composition and magma rheology, the mechanisms supporting efficient ascent of these cargo-rich magmas remains enigmatic. Although olivine is the dominant mineral phase in kimberlite, given the polymineralic nature of mantle xenoliths, xenocrysts are transported as a multi-mineral mixture. Within the ascending dyke, high particle concentrations and high velocities resulting in turbulent flow provides an environment for frequent particle-particle interaction. Xenocryst morphologies, textures and size distributions observed in kimberlite deposits are not reflective of how they occur in xenoliths and are therefore modified during ascent to the surface. The degree of modification of each mineral varies and is a function of its chemical and physical prope…
has type: Thesis/Dissertation
date issued: 2020-05
is shown at: 10.14288/1.0387458
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
type: Text
identifier URI: http://hdl.handle.net/2429/73096