Fluid inclusions in speleothems as a new archive for the noble gas palaeothermometer [Elektronische Ressource] / presented by Tobias Kluge

Informations

• Publié par: ruprecht-karls-universitat_heidelberg
• Publié le: 01 janvier 2008
• Nombre de lectures: 28
• Langue: Deutsch
• Poids de l'ouvrage: 4 Mo

Extrait

DISSERTATION
submitted to the
Combined Faculties for the Natural Sciences and for Mathematics
of the Ruperto-Carola University of Heidelberg, Germany
for the degree of
Doctor of Natural Sciences
presented by
Diplom-Physicist Tobias Kluge
born in Heilbronn
Oral examination:
22.10.2008Fluid inclusions in speleothems as a new
archive for the noble gas palaeothermometer
Referees:
Prof. Dr. Werner Aeschbach-Hertig
Prof. Dr. Augusto ManginiZusammenfassung
Fluideinschlusse¨ in Spel¨ aothemen stellen ein einzigartiges Archiv fur¨ Pal¨aow¨ asser dar. Diese
Arbeit beschaftigt¨ sich mit der Untersuchung der Fluideinschlusse¨ in Spel¨ aothmen bzgl. deren
Verwendbarkeit als Pal¨aotemperaturarchiv. Anhand der temperaturabh¨ angigen Loslic¨ hkeit
verschiedener Edelgase (He, Ne, Ar, Kr und Xe) konnen¨ Edelgastemperaturen gewonnen
werden. Dazu ist die Bestimmung von Edelgaskonzentrationen unerl¨ asslich, welche neben
der Bestimmung absoluter Gasmengen auch die Messung der freigesetzten Wassermenge vo-
raussetzt. Es werden zwei M¨ oglichkeiten vorgestellt, mit denen die sehr kleinen, aus dem
Gestein extrahierten Wassermengen (≤ 1 µl) mit ausreichender Genauigkeit gemessen wer-
den konnen.¨ Darub¨ erhinaus wurden verschiedene Verfahren zur Extraktion von Edelgasen
aus Spel¨aothemen untersucht und in Bezug auf die angestrebte Anwendung analysiert. Als
besonders geeignet hat sich das Zerkleinern in einem Stahlzylinder unter Hochvakuum mittels
einer magnetisch bewegten Stahlkugel erwiesen. Außerdem werden die Edelgasaufbereitung
sowie das auf sehr kleine Gasmengen spezialisierte massenspektrometrische Messverfahren
erl¨ autert.
Abschließend wird anhand von 6 Proben aus einer Wachstumsschicht des Stalagmiten BU-U
aus der Bunkerh¨ ohle (Sauerland) aufgezeigt, dass es moglic¨ h ist, reproduzierbare und glaub-
w¨ urdige Temperaturen zu berechnen. Die Messungen an weiteren Stalagmiten der Bunker-
h¨ ohle (BU-1 bzw. BU-2) ergaben darub¨ er hinaus Temperaturen, die mit den erwarteten
klimatischen Bedingungen ub¨ ereinstimmen. Typische Temperaturunsicherheiten liegen bei
diesen Probenstuc¨ ken zwischen < 1 ℃ und 2 ℃. An den Stalagmiten BU-U und BU-1 wur-
den ub¨ er die Messung von Edelgaskonzentrationen Pal¨ aotemperaturverl¨ aufe erstellt und in
Verbindung mit den stabilen Isotopendaten diskutiert. Diese exemplarischen Anwendungen
machen das große Potential der hier vorgestellten Methode deutlich.
Abstract
Fluid inclusions in speleothem constitute a unique archive for palaeo-waters. This thesis deals
with the investigation of fluid inclusions in speleothems and their possible use as a palaeotem-
perature archive. The main objective focuses on the calculation of noble gas temperatures,
which can be derived from the temperature-dependent solubility of the noble gases He, Ne,
Ar, Kr and Xe. An essential requirement is the determination of noble gas concentrations,
which implies measuring the absolute gas amounts as well as determining the amounts of
water released. Two ways of measuring the tiny water amounts (≤ 1 µl) extracted from
the speleothems are presented and will be discussed with regard to the required precision.
Furthermore, various techniques for the extraction of noble gases from the speleothems are
investigated and analysed in terms of the intended application. It turned out that crushing
under vacuum in a steel cylinder by milling with a magnetically movable steel ball is the
most suitable technique. Additionally, the noble gas preparation and the mass spectrometric
procedure, optimized for the measurement of tiny gas amounts, will be discussed.
Finally, it is demonstrated that it is possible to determine reliable temperatures from fluid
inclusions in speleothems and that the acquired results can be reproduced to a certain extent.
From the stalagmite BU-U (Sauerland, NW Germany) six samples from one growth period
were extracted and measured. Their results agree within the uncertainties although the
samples are not totally identical. Measurements on other stalagmites (BU-1, BU-2) from the
same cave revealed temperatures corresponding to the expected climatic conditions in the
respective growth period. Typical uncertainties for these samples range from≤ 1 ℃ to 2 ℃
at most. From the stalagmites BU-U and BU-1 a temperature record has been established by
noble gas concentrations and will be discussed in combination with the stable isotope data.
These exemplary applications reveal the high potential of the method presented.Contents
1 Introduction 5
2 Theory and basics 9
2.1 Speleothemsasaclimatearchive......................... 9
2.1.1 Speleothemformationandtypes..................... 9
2.1.2 The importance of speleothems in climate research and possible appli-
cations.................................... 13
2.1.3 Limitations................................. 15
2.2 Fluidinclusions 16
2.2.1 Definition,origin,properties........................ 16
2.2.2 Applications ................................ 18
2.3 Noblegasesandcommonapplications...................... 19
2.3.1 Noble gases - occurrence and solubility . . . ............... 19
2.3.2 Temperature determination using noble gas concentrations . . . . . . 21
2.3.3 Furtherapplications............................ 22
2.3.4 Limitations 23
2.4 Noblegasesfromspeleothemsasaproxy..................... 24
2.4.1 Studies using noble gases in fluid inclusions of speleothems and minerals 24
2.4.2 Basic idea of climate reconstruction from noble gases in speleothems . 25
2.4.3 Objective.................................. 26
2.4.4 Constraints................................. 26
2.5 Diffusionofnoblegasesinspeleothems...................... 28
2.5.1 Theoreticalbackground.......................... 29
2.5.2 Literaturevalues.............................. 31
2.6 Adsorptioneffects ................................. 31
2.7 Goals of this study . . ............................... 35
3 Working with speleothems 37
3.1 Sampleselection 37
3.1.1 Opticalmethods 37
3.1.2 Summaryofthethin-sectionanalysis................... 42
3.2 Waterdetermination. 43
3.2.1 Waterdeterminationbyweighing..................... 44
3.2.2 Waterdeterminationbypresure..................... 46
3.2.3 Precision and limits . ........................... 48
3.2.4 Summary.................................. 50
3.3 Extractionofwaterandnoblegases ....................... 51
3.3.1 Designoftheextractionline. 51
3.3.2 Extractionusingametalcrusher 54
34 Contents
3.3.3 Extractionbycrushinginacoppertube................. 56
3.3.4 Extractionbymicrowaveheating..................... 60
3.3.5 Extraction by thermal decrepitation ................... 65
3.3.6 Summary.................................. 69
3.4 Separationtechniques............................... 71
3.4.1 Stepwisecrushing.............................. 71
3.4.2 Stepwiseheating 72
3.4.3 Combinedstepwiseprocedures...................... 75
3.4.4 Summary 78
3.5 Masspectrometry................................. 78
3.5.1 Gasseparationandpurification 78
3.5.2 Measurementsequences.......................... 79
3.5.3 Calibration................................. 80
3.5.4 Reproducibility and uncertainties . . ................... 81
3.5.5 Sensitivity.................................. 82
3.5.6 Blankvalues 83
3.5.7 Measurementautomation......................... 85
3.6 Masspectrometricproceduresanddataevaluation............... 85
3.6.1 HeandNemeasurement.......................... 85
3.6.2 Argonmeasurement............................ 92
3.6.3 Magnet stability and implications for data evaluation . . ....... 93
3.6.4 Dataevaluation............................... 95
3.7 Testofthemeasurementprocedurewithanartificialstandard......... 96
4Results 99
4.1 Caveairanddripwatermeasurements...................... 99
4.1.1 Investigationofthecaveair........................ 99
4.1.2 Dripwatermeasurements..........................104
4.2 Extraction......................................14
4.2.1 Sampleselection..............................114
4.2.2 Waterdeterminationandwatercontent.................114
4.2.3 Air/watervolumeratio16
4.2.4 Applications ................................17
4.2.5 Theory of fluid inclusion origin and frequency . . . ...........124
4.3 Separationtechniques...............................127
4.4 Noblegasfractionationandenrichment .....................130
4.5 DatingviaHelium.134
4.6 Case studies . . ...................................142
4.6.1 Reproducibility and uncertainties . . ...................142
4.6.2 Case study BU-1 . . . ...........................148
4.6.3 Case study BU-U . . .153
5 Summary and outlook 161
References 164
Appendix 179
Abbreviations.......................................179
Listoffigures182
ListofTables185Chapter 1
Introduction
The ten warmest years since 1880 have occurred from 1995 to 2007, of which since 2001 every
year has been one of the ten warmest (DWD, 2008; WMO, 2008). Such an accumulation of
extraordinary mean annual air temperatures encourage the discussion about global warming
and climate change. Not only temp are rising significantly compared to the beginning
of the last century, but also the con