Fluid inclusion and stable isotope studies of hydrothermal vein deposits, Schwarzwald, Germany [Elektronische Ressource] / vorgelegt von Baldorj Baatartsogt

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• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2006
• Nombre de lectures: 71
• Langue: English
• Poids de l'ouvrage: 20 Mo

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FLUID INCLUSION AND STABLE ISOTOPE STUDIES
OF HYDROTHERMAL VEIN DEPOSITS,
SCHWARZWALD, GERMANY.



DISSERTATION
zur Erlangung des Grades eines Doktors der Naturwissenschaften

der Geowissenschaftlichen Fakultät
der Eberhard-Karls-Universität Tübingen





vorgelegt von
BALDORJ BAATARTSOGT

aus Bayan Önjuul, Mongolei.
2006 Baatartsogt B: Fluid inclusion and stable isotope studies of hydrothermal vein deposits, Schwarzwald, Germany.










































Tag der mündlichen Prüfung: 27. Januar 2006


Dekan: Prof. Ph.D. Klaus-Georg Nickel

1. Berichterstatter: Prof. Dr. Gregor Markl

2. Berichterstatter: Prof. Dr. Dr.h.c Muharrem Satir

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Baatartsogt B: Fluid inclusion and stable isotope studies of hydrothermal vein deposits, Schwarzwald, Germany.

TABLE OF CONTENT

ACKNOWLEDGEMENTS 4
ABSTRACT 5
ZUSAMMENFASSUNG 8

Chapter 1. INTRODUCTION 12
Chapter 2. GEOLOGICAL AND METALLOGENIC FRAMEWORK 17
2.1. Geological background 17
2.2. Metallogenesis and hydrothermal veins 23
2.3. Previous studies 24

Chapter 3. SAMPLE DESCRIPTION AND PETROGRAPHY 26
3.1. Sampling strategy and general sample description 26
3.2. Samples used for fluid inclusion and Raman spectroscopy 29
3.3. Samples used for oxygen isotope analysis in quartz 29
3.4. Samples used for sulfur and carbon isotope analysis 29

Chapter 4. ANALYTICAL TECHNIQUES 30
4.1. Microthermometry 30
4.2. Oxygen isotope analysis of quartz 30
4.3. Stable isotope analysis of fluid inclusions 31
13 184.3.1. δD, δ C and δ O isotope analysis of fluid inclusions
in quartz, fluorite and calcite 31
4.3.2. The dependence of hydrogen isotope compositions
of fluid inclusions on the extraction method 32
4.4. Sulfur and carbon isotopes 33
4.5. Infrared Spectroscopy 34
4.6. Raman Spectroscopy 34

Chapter 5. RESULTS 35
5.1. VARISCAN VEINS
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Baatartsogt B: Fluid inclusion and stable isotope studies of hydrothermal vein deposits, Schwarzwald, Germany.

5.1.1. Fluid inclusion data and Raman spectroscopy 35
5.1.2. Oxygen isotope data of vein quartz 39
5.1.3. Hydrogen isotope data of fluid inclusions 41
5.2. POST-VARISCAN VEINS 42
5.2.1. Fluid inclusion data and Raman spectroscopy 42
5.2.2. Oxygen isotope data of vein quartz 49
5.2.3. Oxygen, hydrogen and carbon isotope systematics of fluid inclusions 52
5.2.4. Dependence of measured δD of fluid inclusion water on extraction
temperatures 55
5.2.5. Infrared spectra and water content of fluorite 57
5.2.6. Sulfur isotopes 58
5.2.7. Carbon and oxygen isotopes of calcites 62

Chapter 6. DISCUSSION 66
6.1. VARISCAN VEINS 66
6.1.1. Pressure-temperature conditions of Variscan mineralizations 66
6.1.2. Isotopic composition of the Variscan hydrothermal solutions 67
6.2. POST-VARISCAN VEINS 67
6.2.1. Pressure-temperature conditions of post-Variscan mineralization 67
6.2.2. Isotopic composition of the post-Variscan hydrothermal fluids 69
6.2.3. Sulfur isotope systematics 71
6.2.4. Mixing calculations involving Sulfur isotopes 73
6.2.5. Modeling of the carbon and oxygen isotope composition of
mixed fluids 77
6.2.6. Carbon and oxygen isotope variation in hydrothermal calcites 83
6.2.7. The post-Variscan fluid system 86

Chapter 7. CONCLUSIONS 88

REFERENCES 90

CURRICULUM VITAE 99

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Baatartsogt B: Fluid inclusion and stable isotope studies of hydrothermal vein deposits, Schwarzwald, Germany.

ACKNOWLEDGEMENTS

I am deeply grateful to all of the individuals who gave their valuable ideas and time
generously during my Ph.D research period at the Institute of Geoscience, University of
Tübingen.

In particular, I would like to express my sincere thanks to my supervisor Prof. Dr. Gregor
Markl, who has been an excellent mentor and gave me full support during my Ph.D work. I
will always remember that and be grateful for it. Sincere thanks are due to the Deutscher
Akademischer Austauschdienst (DAAD) for financial support. I would like to thank Prof. Dr.
Dr.h.c Muharrem Satir for his interest in my work and for taking on the function as a co-
advisor.

I am especially grateful to Dr. Thomas Wagner for profitable discussions on interpretations
about stable isotopes and geochemical modeling of ore deposits and his great papers reviews.
Many ideas and discussions of this thesis resulted from the close collaboration with him as
well as my co-PhD student Mr. Gregor Schwinn.
Dr. Heinrich Taubald, Ms. Gabriele Stoschek and Mr. Bernd Steinhilber are thanked for
invaluable help concerning the geochemical and stable isotope analysis. Special thanks to Ms.
Jasmin Koehler for English correction.

This work has significantly benefited from discussions with my colleagues and friends in the
Geoscience Department. To name a few, PD Dr. Thomas Wenzel, Dr. Andreas Audetat
(Bayreuth), Ms. Katrin Mierdel, Ms. Jasmin Koehler and Mr. Gregor Schwinn.
Mr. Bernd Binder helped with the Raman spectroscopic measurements. Infrared
Spectroscopic measurement and its discussion on interpretation data have been done with
assistance of Ms. Katrin Mierdel.
I would also like to thank all my colleagues from the Institut für Geowissenschaften for their
contribution by facilitating most pleasant and academically productive period during my stay.

Very special thanks go to my parents, who enabled me the education in Mongolia and who
have supported and encouraged me from the thousand of miles away. I am very grateful to my
wife, my lovely son and daughter, who accompanied and supported me during my stay in
Germany.
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Baatartsogt B: Fluid inclusion and stable isotope studies of hydrothermal vein deposits, Schwarzwald, Germany.

ABSTRACT
In the Schwarzwald area, southwest Germany, more than 400 hydrothermal veins hosting
different gangue and ore mineral assemblages cross-cut the crystalline basement rocks. An
integrated fluid inclusion and stable isotope study has been carried out on hydrothermal veins
(Pb-Zn-Cu-bearing fluorite-barite-quartz veins, Co-Ni-Ag-Bi-U-bearing and barren barite-
fluorite-quartz veins) from the Schwarzwald district. More than 400 individual samples from
110 Variscan and post-Variscan deposits covering a large area of 120 by 40 km were studied
by microthermometry, Raman spectroscopy, stable isotope analysis of minerals and fluid
inclusions.
Natural waters of various origins exhibit systematic differences in their deuterium (D)
18and O contents. The most straightforward method for the determination of paleofluid
signatures is the direct extraction of fluid inclusion water from hydrothermal minerals.
Inclusion fluids in fluorite are particularly useful, because their host is presumable or
normally devoid of oxygen and hydrogen, thus precluding post-entrapment isotope
exchanges. The δD values for water extracted from fluorites at 400°C range widely between -
60 and +82 ‰, whereas at 650°C the values range from -78 to +40 ‰. The systematic
differences between δD values obtained from the same samples at both extraction
temperatures indicate that most likely two isotopically distinct reservoirs contribute to the
extracted water. To clarify the nature of these reservoirs, FTIR (Fourier transformation
infrared) analyses were performed on the fluid inclusions and host fluorite. The FTIR spectra
-1of fluid inclusions show that two dominant peaks at absorbance values of about 3400 cm and
-15200 cm are present, which conform to structurally bound and molecular water,
respectively. In contrast, the FTIR spectra of fluid inclusion free areas in the host fluorites
-1show only a peak at 3400 cm . These results demonstrate that significant amounts of
structurally bound water must be present in most of the studied hydrothermal fluorites. Based
on the isotopic and spectroscopic data, we believe that water released at extraction
-
temperatures greater than 500-600 °C is dominantly originating from interstitial OH defect
sites in the fluorite structure. This structurally bound water appears to be isotopically depleted
compared to the original fluid inclusion water, resulting in a significant shift of the δD values.
This calls for extreme caution in setting up appropriate analytical procedures for the
determination of δD values and has important implications for the interpretation of paleofluid
signatures.
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Baatartsogt B: Fluid inclusion and stable isotope studies of hydrothermal vein deposits, Schwarzwald, Germany.

Most Variscan fluid