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\DOI{10.5802/crgeos.260}
\datereceived{2024-04-15}
\dateaccepted{2024-04-15}
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%\makeatletter
%\def\TITREspecial{\relax}
%\def\cdr@specialtitle@english{Geodynamics of continents and oceans - A tribute to Jean Aubouin}
%\def\cdr@specialtitle@french{G\'eodynamique des continents et des Oc\'eans - Hommage \`a Jean Aubouin}
%\makeatother

\shortrunauthors

\title{Avant-propos}

%\alttitle{}

\author{\firstname{Michel} \lastname{Faure}\IsCorresp}
\email{michel.faure@univ-orleans.fr}

\author{\firstname{Olivier} \lastname{Fabbri}}

\author{\firstname{Jacky} \lastname{Ferri\`{e}re}}

\author{\firstname{Laurent} \lastname{Jolivet}}

\author{\firstname{Sylvie} \lastname{Leroy}}

\maketitle

\vspace*{6pt}

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\section*{T\'{e}moignage de Ren\'{e} Blanchet}

\vspace*{-1pc}

\begin{quote}
\parindent 0pt

Jean Aubouin, 1928--2020

Acad\'{e}mie des sciences~: \'{e}lu Correspondant en 1978,
\hspace*{.5pc} Membre en 1981

Pr\'{e}sident de l'Acad\'{e}mie des sciences en 1989 et 1990

Pr\'{e}sident de l'Institut de France en 1989

\end{quote}

\vspace*{.5pc}

Tous les \'{e}l\`{e}ves de Jean Aubouin, fran\c{c}ais et \'{e}trangers,
trop nombreux pour \^{e}tre nomm\'{e}s ici, sont reconnaissants au
comit\'{e} \'{e}ditorial des Comptes Rendus G\'{e}oscience de
l'Acad\'{e}mie des Sciences d'avoir promu un num\'{e}ro th\'{e}matique
\guillemotleft{}~G\'{e}odynamique des continents  et des
oc\'{e}ans~\guillemotright{} en hommage \`{a} leur Ma\^{i}tre et
Professeur.

Un comit\'{e} scientifique anim\'{e} par Michel Faure a sollicit\'{e}
les auteurs en accueillant, dans la diversit\'{e}, des approches
nouvelles et stimulantes comme l'aurait souhait\'{e} J. Aubouin.
L'article introductif de Jacky Ferri\`{e}re et Michel Faure montre
toute la richesse de l'\oe{}uvre scientifique de J. Aubouin. 

Depuis son \'{e}lection \`{a} l'Acad\'{e}mie des sciences en 1978 et
jusqu'en 2012, J. Aubouin a manifest\'{e} un engagement sans faille
pour l'Institution. Provincial tr\`{e}s assidu et actif aux s\'{e}ances
et aux r\'{e}unions des comit\'{e}s et commissions, il animait souvent
les d\'{e}bats scientifiques par ses interventions claires et
rigoureuses d'une grande courtoisie. Pr\'{e}sident de l'Acad\'{e}mie
(1989 et 1990), pr\'{e}sident de l'Institut (1989) il a notamment
jou\'{e} un r\^{o}le majeur dans la pr\'{e}paration et la mise en
\oe{}uvre des nouveaux statuts et du r\`{e}glement int\'{e}rieur.

Jean Aubouin a eu le souci constant de l'\'{e}volution et de l'impact
des Comptes Rendus G\'{e}oscience. Il a suivi depuis sa retraite
l'installation d'une nouvelle \'{e}quipe \'{e}ditoriale, et a pu avec
satisfaction, en connaitre les premiers succ\`{e}s. Le fait que ce
num\'{e}ro th\'{e}matique soit publi\'{e} dans la revue de
l'Acad\'{e}mie des Sciences est donc un hommage 
particuli\`{e}rement\unskip\break
justifi\'{e}. 

Jusqu'\`{a} son dernier souffle, Jean Aubouin a eu \`{a} c\oe{}ur de
suivre la carri\`{e}re, et souvent les al\'{e}as de la vie, comme les
r\'{e}sultats scientifiques nouveaux de ses \'{e}l\`{e}ves et, autour
d'eux, des jeunes g\'{e}n\'{e}rations, en France et dans le Monde.

Au nom de cette \guillemotleft{}~Ecole~\guillemotright{} je remercie
chaleureusement le comit\'{e} \'{e}ditorial et tous les auteurs des
publications de ce volume sp\'{e}cial, qui repr\'{e}sente un vrai
moment de synth\`{e}se et de projection, bien utile dans le cours
foisonnant des publications scientifiques.\looseness=1

\vspace*{.8cm}

\hspace*{.33cm}\begin{xxminipage}
Ren\'{e} Blanchet

Professeur \'{e}m\'{e}rite, Universit\'{e} C\^{o}te d'Azur, Nice

Membre de l'Acad\'{e}mie des Sciences 
\end{xxminipage}



\onecolumngrid

\xfigure{fx01}{Jean Aubouin entour\'{e} de ses \'{e}l\`{e}ves lors de la
mission du Charcot sur la zone de subduction des Tonga Kermadec en
1985. De gauche \`{a} droite~: J. Ferri\`{e}re, R. Louat, J. Aubouin,
B. Pelletier, R. Blanchet.}

\vspace*{.3cm}

\twocolumngrid

\section*{T\'{e}moignage de Xavier Le Pichon}
Le num\'{e}ro th\'{e}matique \guillemotleft{}~G\'{e}odynamique des Continents et des
Oc\'{e}ans~\guillemotright{} en hommage \`a Jean Aubouin
t\'{e}moigne de la qualit\'{e} exceptionnelle des
chercheurs qui se r\'{e}clament de lui. Quant \`{a} moi, j'avais lu son
livre \guillemotleft{}~Geosynclines~\guillemotright{} dans les ann\'{e}es soixante et j'avais
\'{e}t\'{e} fascin\'{e} par cet essai de synth\`{e}se auquel il ne
manquait qu'une connaissance des espaces oc\'{e}aniques. Car Jean
Aubouin est pour moi l'homme qui visualisait tout paysage tectonique
comme un espace organis\'{e} avec ses racines. 

Je ne l'ai rencontr\'{e} pour la premi\`{e}re fois qu'en 1968. Je
venais d'arriver en France et mes pr\'{e}sentations de la Tectonique
des Plaques, sponsoris\'{e}es par Jean Coulomb, se heurtaient au
scepticisme des principaux g\'{e}ologues. Ce fut le cas pour Jean
Aubouin qui me critiqua vivement. Je lui r\'{e}pondis qu'avant de
critiquer, il ferait mieux de lire la litt\'{e}rature scientifique
r\'{e}cente. Furieux, il se leva et quitta la salle. Mais un mois plus
tard, il revint me voir en me disant qu'il avait maintenant lu ces
articles et qu'on pouvait discuter. Ce fut le d\'{e}but d'une solide
amiti\'{e} qu'il me manifesta jusqu'\`{a} la fin de sa vie. 

Une dizaine d'ann\'{e}es plus tard, il m'emmena dans une travers\'{e}e
des Hell\'{e}nides ~\guillemotleft{}~\`{a} la recherche des  oc\'{e}ans
perdus~\guillemotright{}. Je d\'{e}couvris l\`{a} son talent pour faire
parler les paysages en faisant appara\^{i}tre ses \mbox{origines.} Cette
excursion g\'{e}ologique donna naissance \`{a} une publication commune
intitul\'{e}e \guillemotleft{}~Les Hell\'{e}nides dans l'optique de la
tectonique des plaques~\guillemotright{}~[1]. D\`{e}s lors, Jean
Aubouin comprit que, pour reconstruire ces oc\'{e}ans perdus, il
fallait \'{e}tudier la tectonique des oc\'{e}ans actuels. C'est ainsi
qu'il devint l'\'{e}l\'{e}ment moteur dans la marche \`{a} la mer des
g\'{e}ologues. Je me souviens d'une pr\'{e}sentation qu'il fit \`{a} la
Scripps Institution \`{a} San Diego. Il se mit \`{a} une
extr\'{e}mit\'{e} du grand tableau et commen\c{c}a \`{a} dessiner une
tr\`{e}s longue coupe tectonique en progressant vers l'autre
extr\'{e}mit\'{e}, d'un trac\'{e} rapide et s\^{u}r sans une seule
interruption. L'assembl\'{e}e \'{e}tait bouche b\'{e}e. Il se fit un
grand silence. 

Le reste de sa vie, Jean Aubouin n'eut de cesse que de partager avec
joie la d\'{e}couverte de ces oc\'{e}ans perdus qu'il avait
soup\c{c}onn\'{e}s mais ne pouvait d\'{e}crire.

\vspace*{.55cm}

\hspace*{1.8cm}\begin{xxminipage}
Xavier Le Pichon

Professeur au Coll\`{e}ge de France

Membre de l'Acad\'{e}mie des Sciences
\end{xxminipage}

\vspace*{.6cm}

\noindent                              
[1] Aubouin, J. Le Pichon, X., Winterer, E., Bonneau, M. 1977. Les
Hell\'{e}nides dans l'optique de la tectonique des plaques, 
\textit{6th Colloquium on the Geology of the Aegean region,
Ath\`{e}nes, Proceedings},
Volume~III, pages~1333--1354. IGME, Athens, 1979.

\section*{Introduction to the thematic volume}
At the end of the sixties, the plate tectonics theory provided a new
fruitful framework to explain all the geological aspects of the Earth
evolution, at least since the Paleo-Proterozoic. This revolution in
Earth Sciences was rapidly understood by Jean Aubouin who shifted from
the geosyncline model to the new paradigm that was able to account for
the sedimentological, petrological, and tectonic features he observed
in the Hellenides. J. Aubouin also realized that the understanding of
orogens was dependent on the improvement of our knowledge on the
geology of the oceanic domains. This ``walk to the sea'' was one of the
guidelines of the tectonic school led by 
J.~Aubouin. \citet{FerriereFaure2024} relate the scientific itinerary
of this Master who deeply influenced the evolution of Earth Sciences.

During more than half a century, the principles of plate dynamics have
been considerably improved. This thematic issue of the Comptes Rendus
G\'{e}oscience presents some of the major advances in the understanding of
tectonic and geodynamic aspects of oceans and continents. Tectonics is
an integrative speciality of Earth Sciences that requires the
contribution of several methods. Therefore, this Volume introduces also
recent methodological progresses in several fields such as analogue and
numerical modelling, low- and high-temperature geochronology,
petrochronology, and crustal rheology. 

Subduction zones are the places where pre-orogenic material is accreted
to the upper plate, but in many convergent plate boundaries the
ablation (or subductive erosion) is a major phenomenon. The physical
causes such as fluid flux or sediment porosity controlling accretion or
erosion in the trench are analyzed by  \citet{Lallemandetal2024}.  The
Alaska-Aleutian subduction zone exhibits trench-parallel extension that
accommodates slip partitioning. As shown by \citet{Kahrizietal2024},
trench oblique- and parallel-faults are often inherited structures that
play a significant role in tsunamigenic rupture. The consequences of
subduction of buoyant structures are explored by 
\citet{ScalabrinoLagabrielle2024} from the example of the Chili ridge.
Ridge subduction induces lithospheric thermal erosion leading to
crustal extension in the upper plate. This process has also important
effects on surface geodynamics, allowing the opening of sea-ways and
controlling climate changes. Moving to ancient orogens, the analysis of
detrital zircon age distribution in the matrix of ophiolitic
m\'{e}langes allows  \citet{Linetal2024} to decipher the source of the
sedimentary rocks involved in the closure of the Paleo-Tethys ocean and
the building of the Permian-Triassic Indosinian belt of SE Asia. 

Extensional tectonics that develop in the upper plate of convergent
active continental margins is well documented in the South China Block.
The large data base is synthetized by  \citet{Chuetal2024} who show
that the formation of domes and basins resulted of two cycles of
compression and extension during the Cretaceous.

Since the sixties, the considerable amount of investigations collected
in the Hellenides allows  \citet{Ferriereetal2024} to propose a
synthetic geodynamic evolution model of this orogen. The model
encompasses all the stages of the formation of a mountain belt from
continental rifting, oceanic opening, oceanic subduction and obduction,
continental collision, and late to post-orogenic extension. The
Hellenides provide also an example of tectonic inversion.
\citet{Chanieretal2024} document the reactivation of the Frontal Thrust
of the Internal Zones as the Main Pelagonian Detachment. The
reactivated Early Cenozoic (Eocene) compressional structures control
the development of Oligo-Mio-Pliocene intramontane basins. 

Although not fully understood yet, oroclines are major structures
widespread in most of orogens. The arcuate shape of the Western Alps is
investigated by  \citet{Brunsmannetal2024} who show that bent
structures, partly inherited from the Eocene Pyrenean orogeny, already
existed before the Alpine collision. The oroclinal bending was enhanced
by the Miocene NW-directed indentation of Adria. The Western Alps are
also an ideal place to unravel the interplay between climatic and
tectonic processes. The formation of the High Verdon Gorge is analyzed
by \citet{Cardinaletal2024}. The timing of incision evidenced by 
$\mbox{}^{36}$Cl dating supports the view that the High Verdon Gorge
morphology was controlled by tectonics and isostatic uplift during the
Quaternary, around ca 2--1.5~Ma, and is thus related to the Quaternary
glaciation, even if a contribution of the Late Miocene, Messinian, salinity
crisis cannot be definitely ruled~out.

The Alpine and Variscan orogens are emblematic systems of Western
Europe. Their  geodynamic evolution is compared in the framework of the
Wilson cycle by  \citet{Faure2024}. The main difference between the
Alpine, Variscan and eo-Variscan belts lies in the contrasted
geothermal gradients. This feature accounts for the variations in
crustal melting, fluid circulation, and ore deposits. Crustal
thickening was accommodated by nappe stacking in the lower plate for
the Alps and the eo-Variscan belts whereas in the Carboniferous
Variscan belt \textit{stricto sensu} nappe stacking involved the upper
plate (i.e. Gondwana)\break continent. 

Along-strike segmentation of orogens is partly controlled by inherited
pre-orogenic structures. Analogue modelling carried out by
\citet{DallAstaetal2024} document several types of rift linkage. The
results are applied in the external zone of the Westen Alps to account
for the formation of the Jurassic passive continental margin and its
Cenozoic inversion. 

Due to it transient character, continental rifting cannot be easily
investigated in natural cases. The mechanisms of continental
lithospheric thinning are reviewed by  \citet{Tugendetal2024}, using a
two-layer numerical model. Extension rates and initial thermal
conditions are two of the major conditions accounting for the different
modes of rifting. This modelling is applied to the conjugate passive
continental margins of Iberia and Newfoundland, and also to the N. part
of the S. China sea. In this last case, the wide lithospheric thinning
appears to be controlled by the high initial geothermal gradient.
Thermomechanical modelling is also developed by  \citet{Perronetal2024}
who address the formation of complex real passive continental margins
formed through multiphase continental rifting and break-up. The
approach that uses a new kinematic calibration module and
thermo-mechanical evolution enables the authors to define specific
areas where deformation is localized in the continental crust. The
method is benchmarked by calibrating a 2D cross-section extracted from
a 3D model. The result provides a satisfactory prediction of the
thermal history and helps to mitigate some uncertainties in the
deformation path compared to the previous approaches. The model is also
applied to the magma-poor Iberia-Newfoundland\unskip\break 
conjugate continental
margins. Numerical models are also used by
\citet{Guillou-Frottieretal2024} to reassess the potential of 
high-temperature geothermal systems. Permeability, topography, fault dip and
tectonic regimes are investigated to propose possible targets for
geothermal exploitation. 

Fluids play a major role in the rheological behavior of the brittle
crust.  \citet{Fabbrietal2024} analyze the relationships between
fluids, faulting and earthquakes in various geodynamic settings. 
Several lines of evidence suggest that supra-hydrostatic pore fluid
pressures contribute to the reactivation of low-angle thrust faults or
normal faults, rather than vertical or steeply-dipping plate boundary
transform faults or intra-continental strike-slip faults.
Supra-hydrostatically pressurized fluids also play a role in the
nucleation and propagation of seismic ruptures in the continental or
oceanic crust, and in subducting slabs at convergent plate margins, as
reported from aftershocks, swarms, slow earthquakes, and to a lesser
extent for major earthquakes. Lastly, variations of pore fluid pressure
due to human activities such as hydrocarbon extraction, dam
impoundment, gas storage or geothermal energy production result in many
cases in the inception of seismic\break activity.

Dating faulting and folding developed in the brittle upper crust
remains a challenge. After reviewing the sedimentological,
stratigraphic, and geomorphic tools commonly used to get an estimate of
fold formation,  \citet{LacombeBeaudoin2024} present the recent
advances allowed by low-temperature geochronological methods such as
K--Ar and U--Pb on illite and  calcite, respectively. In spite of their
limitations, these new methods are powerful approaches to quantify the
duration and rate of deformation developed in fold-and-thrust belts.
Among the numerous geochronological methods, the
$\mbox{}^{40}$Ar/$\mbox{}^{39}$Ar method is one of the most popular.
The \textit{in-situ} approach of dating synkinematic minerals is
introduced by  \citet{Monieetal2024} The dating of ductile shear zones
documents the reworking of mica porphyroclasts involved in polyphase
deformation. The dating of authigenic clay minerals in fault gouges is
another way to access to the time of faulting. The interpretation of
the $\mbox{}^{40}$Ar/$\mbox{}^{39}$Ar results must be carefully
conducted considering the effects of re- and neo-crystallizations,
grain inheritance, and mineral-fluid\unskip\break 
interactions.    

Although investigated since decades, the relationships between
metamorphism and deformation recognized at all geological observation
scales still raise open questions. On the basis of several
world-examples of recent and ancient subduction and collision zones,
\citet{Lardeaux2024} discusses how metamorphic rocks allow us to access
lithospheric- and crustal-scale tectonics. At the rock- and
mineral-scale, the contrasted metamorphic textures are related to the
heterogenous distribution of finite strain. The interpretation of
geochronological dates requires an accurate knowledge of the analyzed
rocks from their mineral compositions, including REE profiles,
metamorphic  textures, up to km-scale tectonic structures. After giving
an historical perspective on the progress of isotopic dating methods
coupled with the understanding of metamorphic processes at the mineral
lattice-scale,  \citet{Labrousseetal2024} show how low-uncertainty
dates and \textit{in-situ} approaches represent major advances in
deciphering the tectono-metamorphic units stacked in the root zones of
orogens. Petrochronology and hygrochronology provide examples of how
dates and rates must be combined to reach a more realistic view of
orogeny. 

The implementation of the most improving tools must not make us forget
that to be useful, they have to be tested with natural objects, since
following the Master, ``les faits valent mieux que l'id\'{e}e qu'on
s'en fait'' (facts are better than the idea we have of them). The
reliability of the laboratory and modelling results must always be
validated by field survey as expressed by ``la v\'{e}rit\'{e} du
terrain'' cherished by\break Jean Aubouin.

The Editors of this Special Issue thank all authors for their relevant
contributions. Their patience during the review rounds is also deeply
acknowledged. Nothing would have been possible without the involvement
of the reviewers who accepted to spend a significant part of their
time and provided much effort to improve the quality of the articles
of this thematic issue. They are warmly acknowledged. 

\vspace*{.7cm}

\hspace*{3cm}\begin{xxminipage}
Michel Faure\frnewline 
CRG Associate Editor\frnewline 
\textemail{michel.faure@univ-orleans.fr} \vspace*{.5cm}

Olivier Fabbri\frnewline 
Guest Editor \frnewline 
\textemail{olivier.fabbri@univ-fcomte.fr} \vspace*{.5cm}

Jacky Ferri\`{e}re\frnewline 
Guest Editor\frnewline 
\textemail{jacky.ferriere@univ-lille.fr} %\vspace*{.5cm}
\end{xxminipage}

\hspace*{1.67cm}\begin{xxminipage}
Laurent Jolivet\frnewline 
Guest Editor\frnewline 
\textemail{laurent.jolivet@sorbonne-universite.fr}\vspace*{.5cm}

Sylvie Leroy\frnewline 
Guest Editor\frnewline 
\textemail{sylvie.leroy@sorbonne-universite.fr}
\end{xxminipage}

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