Investigation and application of thallium isotope fractionation
File(s)
Accepted version
Author(s)
Nielsen, SG
Rehkämper, M
Prytulak
Type
Journal Article
Abstract
This contribution summarizes the current state of understanding and recent advances made in the field of stable thallium (Tl)
isotope geochemistry. High precision measurements of Tl isotope
compositions were developed in the late 1990s with the advent of
multiple collector inductively coupled plasma mass spectrometry
(MC-ICP MS) and subsequent studies revealed that Tl, despite the small relative mass difference of the two isotopes, exhibits substantial stable isotope fractionation, especially in the marine environment. The most fractionated reservoirs identified are ferromanganese sediments with ε205 Tl≈ +15 and low temperature altered oceanic
crust with ε205 Tl≈–20. The total isotopic variability of more than 35
ε 205 Tl-units hence exceeds the current analytical reproducibility of
the measurement technique by more than a factor of 70.
This isotopic variation can be explained by invoking a combination of conventional mass dependent equilibrium isotope effects and nuclear field shift isotope fractionation, but the specific mechanisms
are still largely unaccounted for.
Thallium isotopes have been applied to investigate paleoceanographic processes in the Cenozoic and there is evidence to suggest that Tl isotopes may be utilized as a monitor of the marine manganese oxide burial flux over million year time scales. In addition, Tl isotopes can be used to calculate the magnitude of hydrothermal fluid circulation through ocean crust. It has
also been shown that the subduction of marine ferromanganese sediments can be detected with Tl isotopes in lavas erupted
in subduction zone settings as well as in ocean island basalts.
Meteorite samples display Tl isotope variations that exceed the terrestrial range with a total variability of about 50 ε205 Tl. The large isotopic diversity, however, is generated by both stable Tl isotope fractionations, which reflect the highly volatile and labile cosmochemical nature of the element, and radiogenic decay of extinct 205 Pb to 205 Tl with a half-life of about 15 Ma. The difficulty of deconvolving these two sources of isotopic variability restricts the utility of both the 205 Pb-205 Tl chronometer and the Tl stable isotope system to inform on early solar system processes.
isotope geochemistry. High precision measurements of Tl isotope
compositions were developed in the late 1990s with the advent of
multiple collector inductively coupled plasma mass spectrometry
(MC-ICP MS) and subsequent studies revealed that Tl, despite the small relative mass difference of the two isotopes, exhibits substantial stable isotope fractionation, especially in the marine environment. The most fractionated reservoirs identified are ferromanganese sediments with ε205 Tl≈ +15 and low temperature altered oceanic
crust with ε205 Tl≈–20. The total isotopic variability of more than 35
ε 205 Tl-units hence exceeds the current analytical reproducibility of
the measurement technique by more than a factor of 70.
This isotopic variation can be explained by invoking a combination of conventional mass dependent equilibrium isotope effects and nuclear field shift isotope fractionation, but the specific mechanisms
are still largely unaccounted for.
Thallium isotopes have been applied to investigate paleoceanographic processes in the Cenozoic and there is evidence to suggest that Tl isotopes may be utilized as a monitor of the marine manganese oxide burial flux over million year time scales. In addition, Tl isotopes can be used to calculate the magnitude of hydrothermal fluid circulation through ocean crust. It has
also been shown that the subduction of marine ferromanganese sediments can be detected with Tl isotopes in lavas erupted
in subduction zone settings as well as in ocean island basalts.
Meteorite samples display Tl isotope variations that exceed the terrestrial range with a total variability of about 50 ε205 Tl. The large isotopic diversity, however, is generated by both stable Tl isotope fractionations, which reflect the highly volatile and labile cosmochemical nature of the element, and radiogenic decay of extinct 205 Pb to 205 Tl with a half-life of about 15 Ma. The difficulty of deconvolving these two sources of isotopic variability restricts the utility of both the 205 Pb-205 Tl chronometer and the Tl stable isotope system to inform on early solar system processes.
Date Issued
2017-01-31
Date Acceptance
2016-10-03
Citation
Reviews in Mineralogy and Geochemistry, 2017, 82 (1), pp.759-798
ISSN
1529-6466
Publisher
Mineralogical Society
Start Page
759
End Page
798
Journal / Book Title
Reviews in Mineralogy and Geochemistry
Volume
82
Issue
1
Copyright Statement
© 2016 Mineralogical Society of America.
Sponsor
Science and Technology Facilities Council (STFC)
Grant Number
ST/J001260/1
Subjects
Science & Technology
Physical Sciences
Geochemistry & Geophysics
Mineralogy
EARLY SOLAR-SYSTEM
CONTINENTAL-MARGIN SEDIMENTS
LOW PD/AG METEORITES
IAB IRON-METEORITES
MC-ICP-MS
OCEANIC-CRUST
FERROMANGANESE CRUSTS
CARBONACEOUS CHONDRITES
TRACE-ELEMENTS
S-PROCESS
0402 Geochemistry
0403 Geology
Publication Status
Published