Radiogenic Isotope Geochemistry of Sedimentary and Aquatic Systems (Lecture Notes in Earth Sciences)

225 Pages·1997·11.06 MB·English

by  Peter Stille

Lecture Notes in Earth Sciences 68
Editors:
.S Bhattacharji, Brooklyn
G. M. Friedman, Brooklyn and Troy
H. J. Neugebauer, Bonn
A. Seilacher, Tuebingen and Yale
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Berlin --
Heidelberg
New York
Barcelona
Budapest
Hong Kong
London
Milan
Santa Clara
Singapore
Paris
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Peter Stille Graham Shields
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With 441 Figures and 41 Tables
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Authors
Dr. Peter Stille
Research Director
Centre de Geochimie de la Surface (C.N.R.S.)
I rue Blessig, Strasbourg Cedex, France
Dr. Graham Shields
Centre de Geochimie de la Surface (C.N.R.S.)
I rue Blessig, Strasbourg Codex, France
"For all Lecture Notes in Earth Sciences published till now please see final pages of
the book"
Library of Congress Cataloging-In-Publication Data
St111e, Peter, 1950-
Rad|ogenlc Isotope geochemistry of sedimentary and aquatic systems
/ Peter Stllle. Graham Shields.
p. cm. -- (Lecture notes In earth sciences. ISSN 0930-0317 ;
68)
Includes bibliographical references and Index.
ISBN 3-540-63177-1 (softcover : alk. paper)
1. Isotope geology. 2. Wea~her~ng. 3. Sediments (Geology)
I. Shields, Graham, 1970- [I, Title. III. Series.
OESOl.4.NgS75 1997
551.9--dc21 97-34436
CIP
ISSN 0930-0317
ISBN 3-540-63177-1 Springer-Verlag Berlin Heidelberg New York
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(cid:14)9 Springer-Verlag Berlin Heidelberg 1997
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Table of Contents
1 Introduction and Basic Principles of Isotope Geochemistry .......................... 1
1.1 Stable Isotopes .................................................................................................... I
1.2 Radiogenic Isotopes ............................................................................................ 2
1.2. I The Rb-Sr Method ............................................................................. 3
1.2.2 The U-Th-Pb Method .......................................................................... 5
1.2.3 The Sm-Nd Method ............................................................................ 5
1.2.4 The K-Ar Method ................................................................................ 6
1.3 Pb. Sr and Nd Isotopes as Geochemical "Tracers". ........................................... 7
1.4 Elemental Residence Times .............................................................................. 9
1.5 References ....................................................................................................... 10
2 Weathering ........................................................................................................ 11
2.1 Weathering of the Whole Rock ........................................................................ 12
2.2 Weathering of Biotite and Muscovite Mica ..................................................... 14
2.3 Weathering of Feldspars .................................................................................. 19
2.4- Products of Chemical Weathering .................................................................... 20
2.5 The Sr Isotopic Composition of Fluid Phases in Weathered Profiles; an
Isotopic Model for Rock Weathering .............................................................. 24
2.6 References ........................................................................................................ 30
3 Isotope Geochemistry of River Water ............................................................ 33
3.1 Sr Isotopes in River Water ............................................................................... 34
3.2 Nd Isotopes and the Rare Earths (REE) in River Water .................................. 36
3.3 References ........................................................................................................ 45
4 Isotope Geochemistry in the Environment- ..................................................... 47
4.1 Heavy Metals in the Environment .................................................................... 49
4.2 Migration of Contaminated River Water into Groundwater Systems .............. 63
Preface
This book is based on the script of a lecture course in isotope geochemistry, which
is given at the University of Strasbourg, France and at the Eidgen6ssische
Tecnhi sche Hochschule (ETH), Zurich, Switzerland by Peter Stille. It is intended
to be read by geologists, hydrologists, geochemists and any researchers and
students from the broad fieldof environmental science. Its purpose is to enable
readers to venture safely into the often mirky realms of radiogenic isotope
geochemistry' applied to sedimentary and aquatic systems. The authors have
strived to construct the book ni such a way that it can be read and understood by
those readers, especially students, who have no background in geochemistry. 7
chapters.take the reader through the rock cycle from weathering on the continent
to eventual deposition in the sea, looked at largely from the perspective of
radiogenic isotope geochemistry.
Isotope geochemistry has become the most important field of speciality in
geochemistry and is being applied increasingly to the study of chemical processes
in natural water bodies, the atmosphere and to other aspects of our environment.
By integrating various isotope systems we can demonstrate that chemical
exchange or movement of material has taken place in, for example, waste dumps
or during natural sedimentation processes. (including weathering, erosion and
diagenesis) as a result of water-rock exchange. The study of isotope systems can
yield important information which allows us to determine the origin of migrating
Huid phases, the water-rock ratio necessary for such exchange and the
mechanisms which have led to the mobility of elements.
This book attempts to shed some light on the entire field of sedimentary isotope
geochemistry, including the isotope geochemistry of natural water bodies, and
objectively discusses important results of previous research in the various sub-
fields. Readers are thus given the opportunity to critically assess this research,
allowing them to apply isotopes in their own particular fields. In order to do this,
we will deal especially with the geochemical and environmental questions which
can be and have been solved through the application of an isotopic study.
The sequence of chapters reflects the rock cycle. Weathering and erosion
contribute significantly to sediment formation and are discussed in chapter 2.
In chapter 3, the fluvial transport of these weathering products into the sea is
looked at ni some detail. The rivers transport large quantities of chemical elements
iv Peter Stilte and Graham Shields
into the ocean basins either in dissolved form or associated with the suspended
load. Knowledge of these transport mechanisms allows us to establish mass
balances for the oceans. Isotope studies help us also to reconstruct chemical
exchange processes between the suspended load, river water and river basin
sediments as well as determining the origin of toxic elements. Isotope
geochemistry comes into its own when used to identify the sources of
contamination in river water and to trace the transport routes of unwelcome
chemical substances.
Chapter 4 concerns the application of various isotopic systems to the
investigation of our heavily polluted biosphere. It is designed especially to
encourage environmental researchers to explore the application of isotope
geochemistry to their studies. Problems of source, mobility and exchange
characteristics of heavy metals in contaminated soils and natural water bodies are
discussed here.
Chapters 5, 6 and 7 are all concerned with the marine environment. The oceans
represent the most important sedimentary environment. River loads end up here
and authigenic minerals (e.g. phosphates, carbonates, clay minerals, FeMn-ore
bodies) are formed here. Knowledge of the isotopic composition of oceans today
and in the past is of the greatest importance not only for understanding the
processes of exchange between sediments and seawater and during diagenesis but
also for the reconstruction of the paieo-environment. Residence times of elements
in seawater are explained in Sect. 5.3. Elements with long residence times
(relative to the ocean mixing time) can be used for high resolution
chemostratigraphy (e.g. Sr) whereas those with short residence times can be used
to trace ocean currents and reconstruct ocean circulation patterns in the past (e.g.
Nd, Pb, Ce, O). As well as looking ni detail at the application of the Rb-Sr and the
Sm-Nd systems to stratigraphy and paleoceanography, this chapter introduces tess
intensely researched isotope systems such as the U-Th-Pb, Re-Os and La-Ce
systems and their potential for future marine research.
While chapter 5 concentrates on seawater and authigenic mineral isotope
geochemistry, chapter 6 deals more especially with detrital and authigenic clay
minerals in marine sediments for dating and for constraining mechanisms of
exchange during deposition and diagenesis. The Rb-Sr and K-A.r isotope systems
of clay-rich rocks are explored here. Special attention is paid to the formation and
dating potential of glauconite.
Chapter 7 concerns the behaviour of the Sm-Nd isotope system in marine
sediments during diagenesis. Chemical and isotopic exchange mechanisms
leading to Nd isotopic homogenization between authigenic clay minerals in
phosphate-rich, detrital sediments and bituminous shales are discussed.
Knowledge of these mechanisms is of great importance, not only for the
reconstruction of diagenetic evolution in a sedimentary basin, but also for dating
these diagenetic processes. However, as was shown recently, knowledge of the
Sm-Nd isotopic system can also be important for petroleum exploration, since
Pret'~e iiv
neodymium isotopic equilibrium may occur between authigenic clay minerals,
ambient waters, source rocks and petroleum.
We have benefited from many discussions with, and helpful comments from,
several of our colleagues and friends. Peter Stille would like to express his
gratitude to Emilie Jtiger (Bern) and Mitsunobu Tatsumoto (Denver) who were
undoubtedly the greatest influences during his formative years in science. Thanks
go to Norbert Clauer (Strasbourg) for first introducing Peter Stille to sediments.
We are also grateful to Franqois Gauthier-Lafaye, Regis Bros. Marc Steinmann,
Miriam Andres, Urs Schaltegger, Horst Zwingmann and Jost Eikenberg. Especial
thanks go to Claude Hammel who drafted all the figures.
Strasbourg, France Peter Stille
July 1997 Graham Shields
x Stille Peter dna Graham sdleihS
4.3 Anthropogenic Contamination in River Water Observed Using Isotope
Methods (R, Rhine)
.......................................................................................... 71
4.3. I Oxygen Isotopes ................................................................................ 17
4.3.2 Strontium Isotopes ............................................................................ 72
4.3.3 Carbon Isotopes .............................................................7.6. .................
4.4 Contamination of Flowing Water and Groundwater after the Reactor
Accident at Chernobyl Shown Using Released Radionuclides ....................... 76
4.5 Radionuclides sa Tracers in Sedimentology .................................................... 83
46 References 87
........................................................................................................
5 Isotopic Composition of Seawater Past and Present (Sr, Nd, Pb. Os,
Ce) .................................................................................................................... 89
.5 I Sr Isotopic Composition of Seawater: Tectonic Proxy and Stratigraphic
Toot .................................................................................................................. 90
.5 I I. Microstratigraphy 91
..............................................................................
5.1.2 The Role of Diagenesis in 5r I~otope Stratigraphy 97
..........................
51.3 Micrt~stra~igraphy at the Precambdan/Cambrian Boundary? ........ 102
5.1.4 Mass Balance Calculations ............................................................ 106
5.1.5 The Influence of Groundwater on the Sr Isotopic Composition
of Seawater ..................................................................................... 801
5.2 Nd Isotopic Composition of Seawater: Tracer of Water Circulation
Patterns
.......................................................................................................... 112
5.2.1 Calculation of the Residence Time of Nd in Seawater and of
the Time Necessary for the "I~orough Mixing of Two Oceans
or Water Bodies .............................................................................. 114
5.2.2 Possibilities Ior the Derivation o[ eh1 Nd Isotopic
Composition of Paleo-Oceans ........................................................ 911
5.2.3 Nd Isotopic Evolution ni Seawater ................................................. 126
5.2.4 The Closing of the Tethys and the Opening of the Atlantic ........... 821
5.3 Tracing Ocean Currents Using Nd and Pb Isotopes 331
......................................
5.3.1 Ocean Currents and Nd Isotopes 331
....................................................
5 3,2 Ocean Currents and Pb Isotopes ..................................................... i 35
5.4 Ce Isotopic Composmon of Seawater: Another Potential Tracer of
Ocean Circulation? ........................................................................................ 140
5.5 ..'O Isotopic Composition of Seawater: Stratigraphic Tool or Tracer of
Ocean Circulation Patterns'? ........................................................................... 241
5.5. I Changes in Seawater Os Isotopic Ratio through Geologic
Time 441
................................................................................................
5.5.2 Meteorite Impact at the Cretaceous-Tertiary (K-T) Boundary.? .... 146
5.6 References ...................................................................................................... 150
Contents ix
6 Isotope Geochemistry of Detrital and Authigenic Clay Minerals in
Marine Sediments (Rb-Sr, K-At, O) 155
..........................................................
6. l Detrital Clay Minerals .................................................................................... 551
6.2 Glauconite Formation .................................................................................... 167
6.3 Dating of Authigenic Clay Minerals .............................................................. 178
6.4 References ...................................................................................................... 381
7 The Sm-Nd Isotope System in Detrital and Anthigenic Argillaceous
Sediments 185
......................................................................................................
1.7 The First Attempts to Date Diagenesis Using the Sm-Nd Isotope
Method ............................................................................................................ 185
7.2 The Process of Nd Isotopic Homogenization in Bituminous Shales .............. 188
7.3 Nd Isotopic Homogenization in Phosphatic, Detrital Sediments .................. 204
7.4 References ...................................................................................................... 210
Subject Index 213
......................................................................................................