Tracing water masses and continental weathering by neodymium and hafnium isotopes in the Atlantic sector of the Southern Ocean [Elektronische Ressource] / vorgelegt von Torben Stichel

Torben M.Andersen

Informations

• Publié par: christian-albrechts-universitat_zu_kiel
• Publié le: 01 janvier 2010
• Nombre de lectures: 24
• Langue: English
• Poids de l'ouvrage: 33 Mo

Extrait

Tracing water masses and continental weathering
by neodymium and hafnium isotopes
in the Atlantic sector of the Southern Ocean



Dissertation
zur Erlangung des Doktorgrades
Dr. rer. nat.


der Mathematisch-Naturwissenschaftlichen Fakultät
der Christian-Albrechts-Universität zu Kiel









vorgelegt von
Torben Stichel
Dipl.-Geol., Universität Kiel
Kiel, 2010







































































1. Gutacher und Betreuer: Prof. Dr. Martin Frank
2. Gutachter: Prof. Dr. Anton Eisenhauer
Eingereicht am: 14. Dezember 2010
Datum der Disputation:
Zum Druck genehmigt:




gez. (Titel, Vor- und Zuname), Dekan




































Erklärung



Hiermit versichere ich an Eides statt, dass ich diese Dissertation selbständig und nur mit
Hilfe der angegebenen Quellen und Hilfsmittel erstellt habe. Ferner versichere ich, dass
der Inhalt dieses Dokumentes weder in dieser, noch in veränderter Form, einer weiteren
Prüfungsbehörde vorliegt. Die Arbeit ist unter Einhaltung der Regeln guter
wissenschaftlicher Praxis der Deutschen Forschungsgemeinschaft entstanden.


Kiel, den


(Torben Stichel, Dipl.-Geol.)































































...to Luisa
























Torben Stichel
Tracing water masses and continental weathering by
hafnium and neodymium isotopes in the Atlantic sector of the Southern Ocean
Contents
Abstract v
Zusammenfassung ix
1. Introduction 1
1.1. The global thermohaline circulation and water
masses in the Southern Ocean 2
1.2. Radiogenic isotopes as proxies for past ocean circulation 4
1.3. Hafnium and Neodymium isotope evolution 5
1.4. Low temperature geochemical processes governing
the radiogenic isotope composition of Hf and Nd 7
1.5. Hafnium and Neodymium isotopes in seawater 8
1.5.1 Sources of hafnium and neodymium in the ocean 8
1.5.2 Residence time of hafnium and neodymium in seawater 9
1.5.3 Hafnium and neodymium isotope systematics and
the seawater array 10
1.6. Previous work, motivation and research questions 11
1.6.1. Previous work 11
1.6.2. Motivation and research questions 13
1.7. Outline of the thesis 14
2. Methodology 17
2.1. Surface samples 19
2.1.1. Sample collection and onboard procedures of
the surface samples 19
2.1.2. Home laboratory procedures of the surface samples 20
2.1.3. Chromatographic purification of Hf and Nd of
the surface samples 22
2.2. Deepwater samples 24
2.2.1. Sample collection and onboard procedures of
the deepwater samples 24
2.2.2. Home laboratory procedures of the deepwater samples 24
i Contents
2.2.3. Chromatographic purification of Hf and Nd of
the deepwater samples 25
2.3. Hf and Nd isotope measurements 26
2.4. Hf and Nd concentration measurements by isotope dilution 29
2.4.1. Principles of isotope dilution and spike addition 29
2.4.2. Chemical treatment 31
2.4.3. Mass spectrometry 32
2.5. Recommendations on the methodology 33
3. Sources and input mechanisms of hafnium and neodymium
in surface waters of the Atlantic sector of the Southern Ocean 37
Abstract 38
3.1. Introduction 40
3.1.1. Hafnium and neodymium isotopes as tracers in the sea 40
3.1.2. Study area 43
3.2. Methods 45
3.2.1. Sample collection and onboard procedures 45
3.2.2. Further procedures in the home laboratory 46
3.2.3. Concentration measurements 47
3.2.4. Isotope measurements 48
3.3. Results 50
3.3.1. Hf and Nd concentrations 51
3.3.2. Shale normalized La/Yb ratios 51
3.3.3. Hf and Nd isotope composition 52
3.4. Discussion 53
3.4.1. Particles as potential sources for the dissolved Hf
and Nd in the Southern Ocean? 53
3.4.2. Hf and Nd isotope signatures of the dissolved fraction 55
3.5. Summary and conclusions 58
4. The Hafnium and Neodymium Isotope Composition of
Seawater in the Atlantic Sector of the Southern Ocean 61
Abstract 62
4.1. Introduction 63
ii