An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry
This dissertation contributes to our understanding of the use of the Li-isotopic composition of seawater as a tracer of the earth system with a focus on the role of low-temperature hydrothermal systems within the lava section of the ocean crust. Experiments were conducted to study the exchange coeff...
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ftuvicpubl:oai:dspace.library.uvic.ca:1828/12262 2023-05-15T17:36:45+02:00 An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry Seyedali, Minasadat Coogan, Laurence Gillis, Kathryn M. 2020 application/pdf http://hdl.handle.net/1828/12262 English en eng http://hdl.handle.net/1828/12262 Available to the World Wide Web Lithium isotope geochemistry ICP-MS off-axis oceanic crust hydrothermal system seawater chemistry Thesis 2020 ftuvicpubl 2022-05-19T06:13:14Z This dissertation contributes to our understanding of the use of the Li-isotopic composition of seawater as a tracer of the earth system with a focus on the role of low-temperature hydrothermal systems within the lava section of the ocean crust. Experiments were conducted to study the exchange coefficient (D(Li/Ca)) and isotopic fractionation factor (α; 1000ln(α)=Δ) for lithium between inorganic calcite and an aqueous solution as a function of solution chemistry. These experiments show that, under the conditions used, D(Li/Ca) negatively correlates with solution H+/Ca2+ ratio (and the solution pH) and Δ positively correlates with solution pH. The change in D(Li/Ca) with solution chemistry is interpreted as indicating that Li is incorporated into calcite as LiHCO3, and hence depends on solution H+/Ca2+. A series of diffusion experiments were performed to test whether changes in pH led to changes in the aqueous Li speciation that would lead to changes in the relative diffusivity of the two Li-isotopes, but no such changes were observed. It is proposed that the change in Δ with changing solution pH may either reflect a kinetic or equilibrium isotope fractionation associated with changing solution chemistry. These results have important implications for interpreting the Li content of calcite that has undergone any diagenetic modification. The Li-content and isotopic composition of rocks altered by low-temperature, off-axis hydrothermal systems in the upper oceanic crust were studied to better understand the role of these systems in controlling the Li-isotopic composition of seawater. Results of a detailed study of DSDP Holes 417A, 417D and 418A from 119 Myr Western North Atlantic Ocean basin show that the Li content of the lavas decreases with depth in the upper ~30 m below sediments while the Li-isotopic composition increases from a low value and then does not show systematic variation in deeper sections. No evidence was found to support a role for a change in mineralogy of alteration products to explain the ... Thesis North Atlantic University of Victoria (Canada): UVicDSpace |
institution |
Open Polar |
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University of Victoria (Canada): UVicDSpace |
op_collection_id |
ftuvicpubl |
language |
English |
topic |
Lithium isotope geochemistry ICP-MS off-axis oceanic crust hydrothermal system seawater chemistry |
spellingShingle |
Lithium isotope geochemistry ICP-MS off-axis oceanic crust hydrothermal system seawater chemistry Seyedali, Minasadat An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry |
topic_facet |
Lithium isotope geochemistry ICP-MS off-axis oceanic crust hydrothermal system seawater chemistry |
description |
This dissertation contributes to our understanding of the use of the Li-isotopic composition of seawater as a tracer of the earth system with a focus on the role of low-temperature hydrothermal systems within the lava section of the ocean crust. Experiments were conducted to study the exchange coefficient (D(Li/Ca)) and isotopic fractionation factor (α; 1000ln(α)=Δ) for lithium between inorganic calcite and an aqueous solution as a function of solution chemistry. These experiments show that, under the conditions used, D(Li/Ca) negatively correlates with solution H+/Ca2+ ratio (and the solution pH) and Δ positively correlates with solution pH. The change in D(Li/Ca) with solution chemistry is interpreted as indicating that Li is incorporated into calcite as LiHCO3, and hence depends on solution H+/Ca2+. A series of diffusion experiments were performed to test whether changes in pH led to changes in the aqueous Li speciation that would lead to changes in the relative diffusivity of the two Li-isotopes, but no such changes were observed. It is proposed that the change in Δ with changing solution pH may either reflect a kinetic or equilibrium isotope fractionation associated with changing solution chemistry. These results have important implications for interpreting the Li content of calcite that has undergone any diagenetic modification. The Li-content and isotopic composition of rocks altered by low-temperature, off-axis hydrothermal systems in the upper oceanic crust were studied to better understand the role of these systems in controlling the Li-isotopic composition of seawater. Results of a detailed study of DSDP Holes 417A, 417D and 418A from 119 Myr Western North Atlantic Ocean basin show that the Li content of the lavas decreases with depth in the upper ~30 m below sediments while the Li-isotopic composition increases from a low value and then does not show systematic variation in deeper sections. No evidence was found to support a role for a change in mineralogy of alteration products to explain the ... |
author2 |
Coogan, Laurence Gillis, Kathryn M. |
format |
Thesis |
author |
Seyedali, Minasadat |
author_facet |
Seyedali, Minasadat |
author_sort |
Seyedali, Minasadat |
title |
An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry |
title_short |
An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry |
title_full |
An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry |
title_fullStr |
An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry |
title_full_unstemmed |
An investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry |
title_sort |
investigation of low-temperature off-axis hydrothermal systems using lithium isotopes and trace element geochemistry |
publishDate |
2020 |
url |
http://hdl.handle.net/1828/12262 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
http://hdl.handle.net/1828/12262 |
op_rights |
Available to the World Wide Web |
_version_ |
1766136336559898624 |