N. Clauer

Centre National de la Recherche Scientifique

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S. Chaudhuri

Indian Institute of Technology Guwahati

Nicole Liewig

Institut Pluridisciplinaire Hubert Curien

Theofilos Toulkeridis

Aristotle University of Thessaloniki

Gérard Blanc

Environnements et Paléoenvironnements Océaniques et Continentaux

Peter Stille

Université de Strasbourg

Alfred Kröner

Johannes Gutenberg University Mainz

Khadija Semhi

Université de Strasbourg

O. Dequincey

Centre National de la Recherche Scientifique

François Chabaux

Centre National de la Recherche Scientifique

Joël Lancelot

Aix-Marseille Université

Cooperative Institutions

Centre National de la Recherche Scientifique

Laboratoire d’HYdrologie et de GEochimie

Institut des Sciences de la Terre

Université de Strasbourg

É&

École & Observatoire des Sciences de la Terre

Université Paris Cité

Aix-Marseille Université

Institut de Recherche pour le Développement

Centre de Recherche et d’Enseignement de Géosciences de l’Environnement

Université de Montpellier

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Barberton Greenstone Belt, South Africa PbPb age, stable isotope and chemical composition of Archaean magnesite,

Theofilos Toulkeridis Bernhard Peucker‐Ehrenbrink N. Clauer Alfred Kröner Manfred Schidlowski

Abstract: Trace-element, carbon, oxygen and lead-isotope analyses were carried out to determine theformation mode and crystallization age of magnesite from the Budd ultramaﬁc complex of the ArchaeanBarberton Greenstone Belt, South Africa. Its signiﬁcantly high Ti contents probably relate to a soluble Ti-richaccessory mineral, probably dissolved during magnesite precipitation. Primitive mantle-normalized REEpatterns of the magnesite show negative Ce and Eu anomalies induced by two events: (1) the Eu anomalyindicates reducing conditions probably induced by the emplacement of the ultramaﬁc source rock; (2) the Ceanomaly implies oxidizing conditions, probably during a hydrothermal event that favoured the precipitation ofmagnesite in veins of the rock. This Ce anomaly is among the oldest in Earth history. Negative 13 C( 2.9 to 3.3‰ PDB) and high 18 O (30.5–31.2‰ SMOW) suggest low-temperature precipitation in a near-surfaceKraubath-type epithermal system. The magnesite contains considerable amounts of radiogenic lead (

Magnesite

Greenstone belt

Trace element

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A km-scale illite alteration zone in sedimentary wall rocks adjacent to a hydrothermal fluorite vein deposit

Clay Minerals (2005)

Olaf Brockamp N. Clauer

Abstract In a study of wall-rock alteration in the 1.4 km long Würmtal adit at the Käfersteige hydrothermal vein deposit (northern Black Forest, Germany) illite was found to be the only clay mineral within the Bunter sandstone and intercalated claystone. Illite occurs mainly as a detrital mineral in the claystone, whereas it is hydrothermally neoformed in the sandstone, either in the pores or as an alteration product of K-feldspar. The extensive occurrence of authigenic illite along the entire 1.4 km long profile confirms that the fluids migrated far into the sandstone. The authigenic illite formed during a first pulse of high-temperature fluids ( T h of ~220°C) with a low salinity (~1 wt.% NaCl eq ). These fluids also dissolved Sr and Rb from detrital illite of the claystones at the vein. A later hydrothermal pulse with a lower temperature (~70–150°C) and higher salinity (21–28 wt.% NaCl eq ) silicified the sandstone adjacent to the vein and caused partial substitution of OH - by F - in the structure of the detrital and neoformed illite along the profile. Within analytical error, the K-Ar dates for the neoformed illite of the <2 µm fraction are the same along the profile (~150 Ma). During this hydrothermal process, the age of the detrital illite within the claystone was reset from 310 to 190 Ma. The illite-rich <0.2 µm fractions yield ages of ~142 Ma (sandstone) indicating a Jurassic origin. The uniform age data for illite in the sandstone and in the claystone are probably due to extensive migration of hot fluids through the wall rocks. The hydrothermal fluids are attributed to recycled meteoric water and brines that ascended from the basement into the cover rocks during the opening of the North Atlantic and/or the nearby Tethys area.

Illite

Authigenic

10.1180/0009855054020170

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Citations (20)

Postdepositional Evolution of Platform Claystones Based on a Simulation of Thermally Induced Diffusion of Radiogenic 40Ar from Diagenetic Illite

Journal of Sedimentary Research (2003)

N. Clauer Horst Zwingmann И. М. Горохов

ABSTRACT The Lower Cambrian Lontova claystones contain well crystallized authigenic 1M illite mixed with detrital 2M illite. Part of the authigenic illite probably precipitated during sedimentation and subsequently experienced a temperature up to 140°C, despite a limited burial to 500-1000 m. The difference between the Rb-Sr and K-Ar dates of this authigenic illite are attributed to preferential loss of radiogenic 40Ar induced by a short-lasting thermal pulse. This interpretation is based on an Ar-diffusion model suggesting that the Lontova blue clays were heated to around 140°C for 2-5 Myr. This thermal pulse could have occurred in relation with hot-fluid migration induced by either tectonic dislocations in the basement rocks during the Late Silurian-Early Devonian, or rifting conditions during the Permian. By comparing Rb-Sr and K-Ar data, evaluation of radiogenic 40 Ar losses by small authigenic illite particles at low temperatures could be a powerful tool for reconstruction of evolutionary histories of sedimentary successions that were either shallowly buried, or percolated by migrating fluids released during tectono-thermal activities.

Radiogenic nuclide

Illite

10.1306/061002730058

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Citations (15)

Preliminary information on the chemical and isotopic compositions of waters from the Caspian sea and its tributaries in the Makachkala region (Russia)

N. Clauer Giovanni Maria Zuppi Gérard Blanc Theofilos Toulkeridis Françoise Gasse

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Weathering of smectite and illite- smectite under temperate climatic conditions

Clay Minerals (2001)

V. Šucha J. Šrodoń N. Clauer Françoise Elsass Dennis D. Eberl

Abstract Weathering profiles developed on the top surface of a bentonite (containing Al-Mg montmorillonite) and a K-bentonite (containing mixed-layer illite-smectite (I-S)) under Central European temperate conditions were studied by XRD, HRTEM, FTIR, K-Ar and chemical analyses. Weathering of montmorillonite results in the decrease of cation exchange capacity (CEC), total surface area and Mg content. The process is interpreted as montmorillonite dissolution and precipitation of amorphous SiO 2 . Weathering of I-S produces an increase in CEC and total surface area. The XRD data suggest dissolution of I-S and appearance of smectite as a separate phase at intermediate depths. The fixation of ammonium is documented in the topmost sample. In both profiles, abundant aeolian contaminants, including mica, were identified and their migration was traced using K-Ar dating.

Illite

Bentonite

Cation-exchange capacity

10.1180/000985501750539490

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Citations (61)

Strontium isotopic evolution of oil-field waters from carbonate reservoir rocks in Bindley field, central Kansas, U.S.A

Geochimica et Cosmochimica Acta (1987)

S. Chaudhuri V. Broedel N. Clauer

Carbonate minerals

10.1016/0016-7037(87)90005-6

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Citations (70)

Pb–Pb age, stable isotope and chemical composition of Archaean magnesite, Barberton Greenstone Belt, South Africa

Journal of the Geological Society (2010)

Theofilos Toulkeridis Bernhard Peucker‐Ehrenbrink N. Clauer Alfred Kröner Manfred Schidlowski

Abstract: Trace-element, carbon, oxygen and lead-isotope analyses were carried out to determine the formation mode and crystallization age of magnesite from the Budd ultramafic complex of the Archaean Barberton Greenstone Belt, South Africa. Its significantly high Ti contents probably relate to a soluble Ti-rich accessory mineral, probably dissolved during magnesite precipitation. Primitive mantle-normalized REE patterns of the magnesite show negative Ce and Eu anomalies induced by two events: (1) the Eu anomaly indicates reducing conditions probably induced by the emplacement of the ultramafic source rock; (2) the Ce anomaly implies oxidizing conditions, probably during a hydrothermal event that favoured the precipitation of magnesite in veins of the rock. This Ce anomaly is among the oldest in Earth history. Negative δ 13 C (−2.9 to −3.3‰ PDB) and high δ 18 O (30.5–31.2‰ SMOW) suggest low-temperature precipitation in a near-surface Kraubath-type epithermal system. The magnesite contains considerable amounts of radiogenic lead ( 206 Pb/ 204 Pb is 125.5–153.7 and 207 Pb/ 204 Pb is 41.3–47.7). The resulting Pb–Pb age of 3043 ± 59 Ma is interpreted as dating a hydrothermal event related to the extensive plutonism episode that has been reported in the Barberton area at about 3.1 Ga. Previous models that proposed formation of the magnesite under recent climatic conditions can be discarded.

Greenstone belt

Magnesite

10.1144/0016-76492009-140

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Citations (8)

Genesis and Geodynamic Evolution of the Taoudeni Cratonic Basin (Upper Precambrian and Paleozoic), Western Africa

Geodynamics series/Geodynamic series (2011)

Georges Bronner J. Roussel Roland Trompette N. Clauer

The Taoudeni basin is one of the major structural units of the western African craton. To the north and northwest, it is bounded by the basement of the Reguibat shield. The southern boundary is the Léo shield, the Mauritanide fold belt occurs to the west, and the so-called Pan-African fold belt is to the east. During the period 1100–1000 to 300 Ma, the geodynamic evolution of the Taoudeni basin was controlled by two main factors: 1. An early regional Pan-African orogenic event circa 650 Ma—which gave elasticity again to the West African shield and craton which was stable since 1800 Ma. Before 650 Ma, the subsidence rate was extremely Iow, 3–4 m/Ma, then after 650 Ma, it rose to 15 m/Ma, a normal value for large cratonic basins. 2. The more local occurrence of heavy material, like ferruginous quartzite associated with aluminous gneisses, in the Lower Precambrian basement, which increased the density of the lower part of the crust and induced, during the 1100–1000 to 650 Ma period, important but local subsidence.

Basement

Indian Shield

10.1029/gd001p0081

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Citations (53)

Isotopic Dating of Very Low‐Grade Metasedimentary and Metavolcanic Rocks: Techniques and Methods

N. Clauer S. Chaudhuri

This chapter contains sections titled: Introduction Importance of mineral separation and characterization Principles of isotope dating Fission-track dating Rock lithologies and isotopic homogenization Metamorphic degree and extent of isotopic homogenization A model for isotopic homogenization in low-grade metamorphic conditions Basin evolution based on combined isotopic and fission-track data Conclusions Acknowledgements

Fission track dating

Lithology

Homogenization

10.1002/9781444313345.ch7

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Citations (55)

Understanding present and past Caspian Sea evolution. Contribution from isotope tracers

Escudie As Gérard Blanc Chalié N. Clauer

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Citations (4)