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\DOI{10.5802/crgeos.250}
\datereceived{2023-01-31}
\daterevised{2023-10-31}
\datererevised{2023-12-06}
\dateaccepted{2023-12-07}
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\dateposted{2024-03-05}
\begin{document}

\begin{noXML}

\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

\title{Subduction of active spreading ridges and the disappearance of
Andean-type cordilleras}

\alttitle{Subduction de dorsales actives et att\'{e}nuation des
cordill\`{e}res de type Andine}

\author{\firstname{Bruno} \lastname{Scalabrino}\IsCorresp}
\address{Universit\'{e} C\^{o}te d'Azur, CNRS, Observatoire de la
C\^{o}te d'Azur, IRD, G\'{e}oazur, 250 rue Albert Einstein, Sophia
Antipolis 06560 Valbonne, France}
\email[B. Scalabrino]{bruno.scalabrino@geoazur.unice.fr}

\author{\firstname{Yves} \lastname{Lagabrielle}}
\address{35 All\'{e}e du Pargo, 56000 Vannes, France}
\email[Y. Lagabrielle]{yveslagabrielle@yahoo.fr}

\author{\firstname{Claudio} \lastname{Faccenna}}
\address{Departement of Science, Roma Tre University, Roma, Italy}
\address{GFZ, German Research Center for Geoscience, Germany}
\email{faccenna@uniroma3.it}
\email[C. Faccenna]{claudio.faccenna@gfz-potsdam.de}

\shortrunauthors

\thanks{ECOS France-Chile-Argentina cooperative research program,
CNRS-INSU and Geosciences Montpellier}

\begin{abstract}
We address the possible link between the age of subducting oceanic
lithosphere and growth of elevated cordilleras versus
extension-dominated arc regions. Singularity exists in South America:
the lowest elevated Andean segments are found in Patagonia where the
active Chile Ridge enters the trench. Subduction of active ridge
triggers thermal doming, crustal extension and attenuation of former
cordilleras. At the Antarctica--South America connection, three active
ridge subductions induced the disruption of a former continuous
cordillera during the opening of Drake Passage. Active ridge subduction
induces lithosphere thermal erosion and related crustal extension in
the upper plate. Evolution of regions worldwide experiencing ridge
subduction confirms this hypothesis. %\vspace*{-3pt}
\end{abstract}

\begin{altabstract}
Nous pr\'{e}sentons les liens possibles existants entre l'\^{a}ge de la
lithosph\`{e}re oc\'{e}anique en subduction et la croissance des
cordill\`{e}res de haute altitude par rapport aux r\'{e}gions d'arc
domin\'{e}es par de l'extension. Une singularit\'{e} existe en
Am\'{e}rique du Sud~: les segments andins les moins \'{e}lev\'{e}s se
trouvent en Patagonie, lieu o\`{u} la dorsale active du Chili passe en
subduction. La subduction de dorsale active entraine ici le bombement
thermique de la plaque sup\'{e}rieure puis l'extension et
l'att\'{e}nuation de la Cordill\`{e}re pr\'{e}c\'{e}demment form\'{e}e.
Au niveau de la connexion Antarctique--Am\'{e}rique du
Sud, trois dorsales actives en subduction ont provoqu\'{e} la
disparition d'une ancienne cordill\`{e}re continue lors de l'ouverture
du Passage de Drake. Les processus de subduction de dorsales actives
sont responsables d'une importante \'{e}rosion thermique de la base de
la lithosph\`{e}re et par cons\'{e}quent de l'extension de la plaque
sup\'{e}rieure. Cette hypoth\`{e}se est confirm\'{e}e \`{a} partir de
la synth\`{e}se des r\'{e}gions \`{a} travers le monde ayant connus des
subductions de dorsales actives dans le pass\'{e}.
\end{altabstract}

\keywords{\kwd{Cordilleras}
\kwd{Active spreading subduction}
\kwd{Slab window}
\kwd{Extensional tectonics}
\kwd{Attenuation}}

\altkeywords{\kwd{Cordill\`{e}res}
\kwd{Subduction de dorsale active}
\kwd{Fen\^{e}tre asth\'{e}nosph\'{e}rique}
\kwd{Tectonique extensive}
\kwd{Att\'{e}nuation}}

\maketitle

{\vspace*{3pt}}

\twocolumngrid

\end{noXML}

\section{Introduction}\label{sec1}

Subduction of oceanic lithosphere beneath continental lithosphere is
able to generate high relief cordilleras, such as the Andean belt in
South America and the Sierra Nevada, Coastal Ranges, Rocky Mountains
and Alaska Mountains in Northern America. However, with along many
subduction zones worldwide, the continental lithosphere overriding the
subducting oceanic lithosphere does not carry high elevation belts.
This is well observed for example, along the subduction zones of Alaska
Peninsula, Aleutian Islands, Kuril Islands and Ryukyu Islands as well
as along the overall Indonesia convergent \unskip\break boundary.

\begin{figure*}
\vspace*{2pt}
\includegraphics{fig01}
\vspace*{3pt}
\caption{\label{fig1}Present-day slab windows and probable location of
areas affected by Cenozoic slab windows beneath SE Asia to Antarctica
Peninsula
[\citealp{DickinsonSnyder1979,JohnstonThorkelson1997,GorringKay2001,
Sissonetal2003,Madsenetal2006,BreitsprecherThorkelson2009,Whittakeretal2007,Thorkelsonetal2011, 
Mulleretal2008,Mulleretal2016} for predicted SE Asian slab
window].}
\vspace*{3pt}
\end{figure*}

Explanations for such contrasting styles of the continental lithosphere
overriding subducting oceanic lithosphere have long been proposed but
are still a matter of debate. Classifications based on various
characteristics describing the behaviour of the upper and lower plates
suffer many exceptions
\citep{Shemenda1992,Shemenda1994,Uyeda1982,UyedaKanamori1979}. At a
global scale, differences of topography between western and eastern
Pacific cordilleras can be assigned as a function of subduction
polarity, related slab retreat/advance and force balance
\citep{Doglionietal1999,Doglionietal2007}. For
\citet{VanderhaegheDuchene2010}, the topography of the overriding plate
is the consequence of the crust-lithospheric mantle ratio resulting
from the interaction between slab kinematics and the degree of
crust-mantle coupling/decoupling. Moreover, by looking at the force
balance, mechanisms involving mantle drag beneath the upper plate can
represent a prime role to the deformational regime at subduction zones
\citep[e.g.][]{Husson2012}. Another point of view is to attempt to
correlate simple parameters. For example, correlating the topography of
the continent at a given active margin boundary with the age of the
corresponding subducting oceanic lithosphere provide contrasted results
\citep{Garfunkeletal1986,HeuretLallemand2005,Heuretetal2011,Jarrard1986,SdroliasMuller2006}. 
In addition, lateral changes of rheology due to progressive variations
in the age of the subducting lithosphere are difficult to integrate
into analogic or numerical experiments 
\citep{DeLongetal1979,DelongFox1977,GroomeThorkelson2009,UeharaAoya2005}.
More specifically, the situations involving the subduction of active
spreading ridges leading to the opening of an asthenospheric slab window
beneath a continental margin, although studied in detail
\citep{Thorkelson1996,ThorkelsonTaylor1989}, have not been integrated
into a model depicting the complete evolution of subduction
cordilleras.

The purpose of this article is to examine the role played by the
subduction of active spreading ridges on the evolution of subduction
belts, with a focus on the processes leading to the attenuation and
disappearance of the cordillera reliefs (Figure~\ref{fig1}). We first
discuss correlations between two parameters which may simply describe
ocean-continent subduction zones. For a given transect across a
subduction zone, these parameters are: (1) the mean elevation of the
continent of the upper plate and, (2) the age of the subducting oceanic
lithosphere at trench. We point to a major singularity arising when
considering this simple correlation at the global scale on one hand,
and at a more regional scale, on the other hand.



Resolving this singularity at the scale of the Andean belt leads us to
emphasize the role played by the subduction of active spreading ridges
and the opening of slab windows in the progressive decrease of the
elevation and volume of the cordillera. We finally test the idea that a
causal link exists between lowering and disappearance of subduction
cordilleras reliefs and opening of slab windows due to spreading ridge
subduction by discussing a number of situations worldwide.

\section{Correlating the {cordillera topography} with the 
{age of the subducting oceanic lithosphere}: the {singularity}}

At the scale of the entire peri-Pacific subduction boundaries, there is
a negative correlation between the elevation of the continental crust
over the subducting oceanic lithosphere (corresponding to the forearc
to the back-arc region) and the age of the oceanic lithosphere at the
trench for a given transect (blue dotted line with a correlation
coefficient $R^{2} = -0.16$, Figure~\ref{fig2}). Without considering
transects located close to modern subducting spreading ridges, low
elevation subduction belts are found in the west Pacific regions where
the descending lithosphere is of Mesozoic age (Figure~\ref{fig2}). High
elevation cordilleras such as the Andes, the Western American
Cordillera and the Alaska belt, are found along the eastern Pacific
regions where the subducting lithosphere is Cenozoic in age
(Figure~\ref{fig2}). However, at a more \mbox{regional} scale, when considering
the relations between the elevation of the Andean crust and the age of
the oceanic lithosphere at the trench, the negative correlation is
changed into a positive correlation (red dotted line with a correlation
coefficient $R^{2} = 0.59$ on Figures~\ref{fig2}, and~\ref{fig3}).
This constitutes a singularity that needs to be solved. Indeed, the
highest and widest elevation of the Andes, corresponding to the
Altiplano-Puna region, occurs where the oceanic lithosphere is the
oldest (Eo-Oligocene) (transects S15 and S16 Figures~\ref{fig2} and~\ref{fig3}) 
and by contrast, the \unskip\break{lowermost} segments of the
Cordillera, in Central Patagonia, occur at the site of the Chile Triple
junction (CTJ), where the oceanic lithosphere is zero Ma in age, that
is where the Chile spreading ridge enters the trench (transect S19
Figures~\ref{fig2} and~\ref{fig3}). Southward of the CTJ, the Andes
disappear completely into the ocean due to the opening of the Scotia
Sea during the Neogene
\citep{Eagles2003,Eaglesetal2005,Eaglesetal2006,Lagabrielleetal2009,Livermoreetal2005,Livermoreetal2007}.
This occurred following a period of rifting that affected the
Antarctica--South America connection where a high subduction cordillera
existed 
\citep{EaglesJokat2014,GhiglioneRamos2005,Ghiglioneetal2016,Kraemer2003,Verardetal2012}. 
In the following section, we will show that the attenuation and
complete disruption of this former Cordillera occurred in relation with
the subduction of several active spreading ridges.

\begin{figure*}
\includegraphics{fig02}
\vspace*{-1pt}
\caption{\label{fig2} (A) Peri-Pacific overview showing continental
topography (Digital Elevation Model, GTOPO30) and age of the oceanic
lithosphere \citep[from][]{Setonetal2020}. 19 transects were selected
from Indonesia to southern South America. Max/mean/min topographic
profiles of each 19 transects were extracted and are available on
Supplementary files. (B) Correlations between age of the oceanic
lithosphere at trench and the surface area S of the overriding plate
domain along the 19 selected transects. The surface area S was 
extracted from mean elevation of the 19 selected transects from
peri-Pacific region (using the midpoint Reimann Sums method). Surface
area of transects across the Andean Cordillera are represented with red
stars. Green (from west Pacific to Aleutian regions) and orange (east
Pacific regions) boxes represent the peri-pacific correlations between
topography and age of the oceanic lithosphere. The blue dotted line
corresponds to the negative correlation observed along the peri-Pacific
regions with a correlation coefficient $R^{2}= -0.16$. The
red dotted line corresponds to the positive correlation described
between the Andean Cordillera topography and the age of the subducted
oceanic lithosphere at trench. The correlation coefficient
$R^{2} = 0.56$ was calculated using red stars.\vspace*{-3pt}}
\end{figure*}

\begin{figure*}
\vspace*{1pt}
\includegraphics{fig03}
\vspace*{1pt}
\caption{\label{fig3}The positive correlation between the Andean
topography and the age of the oceanic lithosphere at trench. (A)~Maximum
(red line) and mean (gray area) elevations of the Andean Cordillera in
1\textdegree~latitude bins (with 100-km width). Yellow line represents
the seafloor age (Myr). The location of the Chile Triple Junction (CTJ)
corresponds to the yellow star. (B)~Andean topography (Digital Elevation
Model, GTOPO30) and seafloor age 
\citep[from][]{Setonetal2020,SdroliasMuller2006}.
The trench is represented by thick line with
triangles. Red dotted line limits the Andean topographic front 
\citep[from][]{Horton2018}. Relative plate velocities from
\citet{DeMetsetal1990}.}
\vspace*{1pt}
\end{figure*}

\section{Resolving the singularity along the Andean Cordillera}\label{sec3}


At present, the Andes are actively growing in the regions north of the
Chile Triple Junction and south of the Cocos--Nazca--Mid-America trench
junction 
\citep[e.g.][]{Allmendingeretal1997,Gregory-Wodzicki2000,Isacks1988,Jordanetal1983,Ramos1989}. 
Active eastward verging thrusts develop in the frontal regions of the
Andes where the Amazonian lithosphere is underthrust beneath the Andean
lithosphere \citep{Taboadaetal2000}. The resulting continental plateau,
formed in response to the initiation of westward South America
continental (or Amazonian block) collision, stretches for
North--South 1800~km-long and attains a width of
350--400~km. Westward verging thrusts also develop in the
western Andean belt \citep{Armijoetal2015}. Current uplift occurs with
the highest values recorded in the central Andes, in the Altiplano-Puna
regions 
\citep[e.g.][]{Gregory-Wodzicki2000,HussonSempere2003,Perkinsetal2016}. The
Altiplano-Puna Andean plateau was uplifted primarily because of crustal
thickening produced by horizontal shortening of a thermally softened
lithosphere \citep[e.g.][]{Allmendingeretal1997,Gerbaultetal2005}
with a recent evolution linked to gravity-driven crustal channel
\citep{HussonSempere2003}. Uplift in the region of the Altiplano began
around 25~Ma, coincident with increased convergence rate and inferred
shallowing of subduction; uplift in the Puna commenced 5--10
million years later
\citep{Sempereetal1990,Allmendingeretal1997,Charrieretal2013}.
Therefore, the current \mbox{topography} of South America is a recent feature
and contrasted morphological changes have occurred along various
segments of the Andean cordillera during the last 50~Ma.

An overview of the average evolution of the topography of the Andean
orogen highlights that an important decrease of max and mean elevation
occurs starting from 35\textdegree~S (Figure~\ref{fig3}). At the site
of the present-day Chile Triple Junction, the mean topography of the
Andean belt is reduced. Here, the cordillera lacks central high relief
and the average elevation reaches a few hundred meters
[Figure~\ref{fig3} and see \citealp{Scalabrinoetal2010} for more details].
It is demonstrated that the uplift of the Central Patagonia Cordillera
occurred from 25 to 15~Ma in response to compressional deformation of
the arc domain
\citep{Blisniuketal2005,Lagabrielleetal2004,Ramos1989,Thomsonetal2001}. 
Eastward verging frontal thrusts bring the external units of the
Cordillera over molasse deposits of the Pampa regions
(Figure~\ref{fig4}A). After this period linked to the break-up of the
Farallon plate \citep{Londsale2005} inducing the acceleration rate of
the subduction of the Nazca plate \citep{Somoza1998,Pardo-casasMolnar1987}, 
the interval 16--14~Ma was characterized by the tip of a
long segment of the SCR entering the Chile trench at around
55\textdegree~S \citep{CandeLeslie1986}. In the Patagonian Cordillera,
the compression resumed and a major phase of erosion resulted to the
rapid peneplanation of the eastern side of the frontal belt 
(Figure~\ref{fig4}B). To the west, low-temperature thermochronology
studies show that the late Cretaceous topographic evolution of the
Cordillera was governed by complex feedbacks between deep geodynamic
processes \citep{Georgievaetal2019,Guillaumeetal2013} with climate
\citep{Thomsonetal2010,Willettetal2020}, transcurrent deformation
along the dextral strike-slip Liqui\~{n}e-Ofqui Fault Zone (LOFZ) 
\citep[e.g.][]{Cembranoetal2002} and upper crustal shortening along NW--SE
thrusts related to the LOFZ 
\citep{Georgievaetal2016,StevensGodardFosdick2019}. The occurrence of
remnants of glacial deposits and landform perched surfaces preserved
in the central and eastern parts of the cordillera also suggests higher
elevations at this time
\citep{Lagabrielleetal2010,Scalabrinoetal2010,Scalabrinoetal2011}.

\begin{figure}
\vspace*{-1pt}
\includegraphics{fig04}
\vspace*{-5pt}
\caption{\label{fig4}\fontsize{9.7}{11}\selectfont
{Lithospheric-scale model of circum-Pacific
cordilleras evolution during active spreading ridge subduction from a
``classical cold'' subduction stage (A) to a ``hot'' subduction stage 
(B--D). After a compressional stage linked to arrival of high bathymetric
features close to the trench (A), regional thermal uplift, or
related-uplift dynamic topography, represents the first impact of
uprising of hot asthenosphere flows through the slab-window
(B--C). Extensional to transtensional deformation
associated with variability of magmatism comprising voluminous OIB
intraplate activities substantiates the thermal erosion and the
weakening of the continental lithosphere above and around slab window
pathways (D).}}
\end{figure}

From 15 to 3~Ma, large alkaline plateau basalts were erupted in the
eastern Patagonia Cordillera (Figure~\ref{fig4}C)
\citep{Espinozaetal2008,Gorringetal1997,Gorringetal2003,RamosKay1992}.
These major magmatic events are likely linked to the development of a
tear in the Nazca slab \citep{Guiveletal2006}, followed by the
development of the Patagonian slab window
\citep{GorringKay2001,BourgoisMichaud2002,BreitsprecherThorkelson2009,Espinozaetal2010,Lagabrielleetal2004,Russoetal2010}.
During this period, no significant tectonic and arc magmatic activities
are known in the cordillera domain, but the overall elevation of the
cordillera remained high south of CTJ (Figure~\ref{fig4}C). As depicted
in Figure~\ref{fig4}C, \citet{Scalabrinoetal2010} suggest that
synchronously to alkaline magmatism, thermal uplift was able to
maintain high elevation plateau, creating conditions for major eastward
glaciers dynamics as shown by 7~Ma to 3~Ma till deposits interbedded
with alkaline lavas \citep{Lagabrielleetal2010,MercerSutter1982}.
Thermal doming, or dynamic topography according to some authors, is
interpreted as the first consequence of the presence of hot
materiel beneath the upper plate 
\citep{AvilaDavila2018,AvilaDavila2020,Guillaumeetal2009,Scalabrinoetal2010}. 

The cessation of the tectonic activity along the Patagonian Cordillera
coincides with the collision and subduction of the Chile Spreading
Ridge, which started at 14~Ma at the site of the present-day Tierra de
Fuego. Negative tectonic inversion of the front of the Cordillera
occurred recently in Central Patagonia as a response to the presence of
very young subducted segments of the Chile Ridge buried at depth
\citep{Scalabrinoetal2010,Scalabrinoetal2011}. This frontal inversion
is accompanied by the subsidence of internal asymmetrical basins
limited by normal faults, inside the cordillera itself
(Figure~\ref{fig4}D). According to
\citet{Scalabrinoetal2010,Scalabrinoetal2011}, extensional tectonics
play an important role in the attenuation of the reliefs of the
cordillera (Figure~\ref{fig4}D). Extension was triggered by the
presence of hot mantle belonging to the subducted Chile Ridge
lithosphere moving eastward beneath the southern tip of the South
America Plate.

\begin{figure*}
{\vspace*{-2pt}}
\includegraphics{fig05}
{\vspace*{-4pt}}
\caption{\label{fig5}\fontsize{9.7}{11.8}\selectfont
{Early Tertiary (A) and present-day (B)
configurations of the South American plate and West Antarctica
Peninsula. (A)~Paleoelevation of South American plate and supposed
continental connection to the West Antarctica Peninsula at 60--50~Ma
\citep[from][]{Boschman2021,Ghiglione2016,Regueroetal2013,Rileyetal2023}.
Cross section A--A$'$ represents the large-scale 2D structure of the Andean
magmatic arc and back-arc domains 
\citep[simplified from][]{Armijoetal2015}
and the cross-section B--B$'$ is a proposed
structural view of the former elevated Cordillera (including the
Cordillera Darwin) connecting the South American plate to the West
Antarctica Peninsula 
\citep[after ][]{Cunningham1993,Cunningham1995,Ghiglione2016,Ghiglioneetal2016,Rondaetal2019}. 
(B) Present-day elevation of the Andean and the
West Antarctica Peninsula. Cross section C--C$'$ corresponds to the actual
tectonic structure of the Andean belt at 21\textdegree~S 
\citep[after][]{Armijoetal2015}, cross section 
D--D$'$ illustrates the present-day
setting of the Drake Passage and Scotia Sea back-arcs domains.}}
\end{figure*}

South of the present-day Chile Triple Junction, geological studies 
revealed that the Andean Cordillera started growing in earliest
Cenozoic times, that is well before the current Central Cordillera of
Chile--Peru--Bolivia which was at that time with elevations close to
sea-level (Figure~\ref{fig5}A) 
\citep[e.g.][]{Armijoetal2015,Boschman2021,Gregory-Wodzicki2000,Horton2005,Jordonetal2010,Lambetal1997,Sempereetal1997}.
Exhumation of the internal part of the Cordillera Darwin in Tierra del Fuego
initiated during the Eocene, indicating that there was a larger
cordillera belt at the site of the current tip of southernmost South
America (Figure~\ref{fig5}A) 
\citep{Coutandetal1999,Cunningham1993,Cunningham1995,Fosdicketal2011,Ghiglioneetal2016,Mulleretal2021,Rondaetal2019}. 
At present, the Central Andean Cordillera
regions expose highest elevation and the widest belt
(Figure~\ref{fig5}B), while to the south, remnants of the former
Southern Andean Cordillera form restricted parts of the end of South
America continent and are still exposed along the Antarctic Peninsula
(Figure~\ref{fig5}B). Plate reconstructions of the South
America--Antarctica region involve frequent interplay between ocean
lithosphere subduction and accretion at young spreading centers since
Mesozoic times. Based on a compilation of various regional kinematics
models gathered from the literature, Figure~\ref{fig6} shows the
evolution of the interactions between trenches and ridges to the south
of South America. The current Drake Passage area was the site of
the subduction of at least three active spreading ridges
(Figure~\ref{fig6}) and its mantle is now characterized by a strong
thermal anomaly. Tomography models reveal a zone of strongly attenuated
P and S waves extending from the CTJ to the Antarctica Peninsula 
\citep[e.g.][and references herein]{BenMansouretal2022}. The opening of
the Drake Passage at 33~Ma (Figure~\ref{fig6}), in response to seafloor
spreading along the Scotia Ridge \citep[][and
references herein]{Lagabrielleetal2009}, 
cross-cut the Southern Andean Cordillera leading to
two separated strongly attenuated remnant cordilleras. The volume and
elevation of the former continuous cordillera remain unknown, but
comparison with some portions of the current Andes north of the Chile
Triple Junction can be proposed (Figure~\ref{fig5}A--B). 

\begin{figure*}
\includegraphics{fig06}
\caption{\label{fig6}Schematic kinematic reconstructions of South
America--Antarctica since 60~Ma, showing relations between active
spreading ridges subductions and Scotia Sea back arc expansion. General
stereographic projection (using GMT software), 
after \citet{Scalabrinoetal2009}.}
\end{figure*}


\section{A theoretical model of ``active continental margin orogenic
cycle''}\label{sec4}

The evolution of the Antarctica--South America connection leads us to
highlight a causal link between the sites of opening of slab windows
and the attenuation and disappearance of a former continuous
cordillera. Situations involving more than one ridge subduction in one
single region are rare on Earth, but they cannot be neglected. We will
comment in Section~\ref{sec5} the case Sundaland that has been
concerned by the subduction of two ridges leading to widespread
extension in the upper plate. Most of the situations however involve the
subduction of one ridge. Here we attempt to design a theoretical
evolution for active continental margin with cordillera which focuses
on the variations of slab forces before, during and after the
subduction of a single spreading ridge segment (Figure~\ref{fig7}). We
assume that the ridge intersects the trench at a low angle.

\begin{figure}
\includegraphics{fig07}
\vspace*{-5pt}
\caption{\label{fig7}Multi-stage theoretical model of continental
margin evolution during and after active spreading ridge subduction and
slab window formation (see comments in text).\vspace*{-5pt}}
\end{figure}

The evolution can be divided into three stages. During stage 1
(cartoons 1 and 2, Figure~\ref{fig7}), the ridge remains far from the
trench and the age of the ocean lithosphere decreases oceanward from
the trench. We assume that slab pull is efficient as a large amount of
relatively old lithosphere is descending in the subduction zone.
Therefore, coupling at the subduction interface is supposed to remain
high during stage 1 and a compressional regime develops in the
continental plate triggering the construction of an elevated
cordillera. Analogue models have shown that an increase of shortening is
observed in the overriding plate during the subduction of increasingly
young oceanic lithosphere in the case the overriding plate moves toward
the trench faster than slab retreat \citep{Salzeetal2018}.

During stage 2, the ridge enters the trench (cartoon 3,
Figure~\ref{fig7}). Now, the oceanic lithosphere gets older seaward.
Interplate coupling decreases due to rapid thermal weakening at the
plate interface; in a same sense, slab pull force is greatly reduced
because a slab window opens beneath the forearc domain. 

During stage 3, the oceanic lithosphere is older oceanward
(cartoons 4 and 5, Figure~\ref{fig7}). The slab-window continues to
develop and migrates beneath the upper plate. A high thermal regime occurs
beneath the continental lithosphere and the overriding plate records
long-wavelength thermal doming as suggested by field studies in the
Patagonian Cordillera (cartoon 4, Figure~\ref{fig7})
\citep{Scalabrinoetal2010,Scalabrinoetal2011}. In cartoon 5, the
slab-window is largely opened and a thermal erosion occurs at the base
of the continental lithosphere. The tectonic regime of the cordillera
is now dominated by local to regional extension with negative inversion
of the main thrusts.

After a few millions of years, the slab window opens largely and the
asthenospheric mantle is able to flow from the oceanic domain through
the window to maintain a large thermal anomaly beneath the upper plate,
favoring thermal erosion. In addition, slab pull is reduced to almost
zero and the coupling at the interface might still be low. These
parameters maintain low tectonic coupling at the subduction interface. 

Numerical models designed to investigate the effects of the complete
subduction of an oceanic plate suggest that the arrival of a mid-ocean
ridge at the trench is preceded by a slab detachment due to a \mbox{reduction}
in strength and negative buoyancy of the approaching oceanic
lithosphere and the loss of transmission of the slab pull force to the
surface \citep{BurkettBillen2009,Wuetal2022b}. In terms of mantle
dynamics, a complex mantle circulation begins beneath the upper plate.
Laboratory models of mantle dynamics through slab gaps highlight that
lateral, poloidal and toroidal flow patterns affect a large part of the
subduction zone which may result on some variations of the
spatio-temporal behavior of the overriding plate 
\citep[see][]{Guillaumeetal2010,Kiralyetal2018,Kiralyetal2020}.

A remarkable feature displayed by large peri-Pacific subduction
boundaries is their geographical stability over hundred millions of
years. This is well demonstrated for the successive Ecuador--Peru--Chile
arcs that moved only some dozen of kilometers apart from an average
position on the western side of South America 
\citep[e.g.][]{Ancellinetal2017}. For this reason, during their long
evolution, the Andean-type cordilleras are able to record all types of
margin morphologies and structure
\citep{Allmendingeretal1997,Armijoetal2015,Onckenetal2006,Ramos2009,Ramos2014,RussoSilver1996}. 
Indeed, during its Mesozoic--Cenozoic
evolution, the Andes region changed from a very low elevation area
dominated by marine sedimentation to a 400~km wide uprising continental
plateau, that reached an elevation of 3500--4000~m during a relative
short period of about 20~Ma (see Figure~\ref{fig5}A--B) 
\citep[e.g.][]{Armijoetal2015}. Inversely, we recalled above that around
33~Ma, southernmost South America underwent progressive subsidence and
completely disappeared below sea-level in relation to the opening and
widening of the Drake Passage (Figure~\ref{fig5}B). This implies that
at the geological scale, the reliefs of subduction cordilleras are not
stable features, they may change from elevations close to sea level to
very elevated plateaus that in turn may resume to sea level elevations.
We thus evidence an ``active continental margin orogenic cycle''
including birth, growth, attenuation and disappearance of subduction
cordilleras. Part of this cycle is controlled by the subduction of
active spreading ridges.
\vspace*{-3pt}

\section{Discussion: what about the rest of the\newline world?}\label{sec5}
\vspace*{-2pt}

In the following, we will explore how geological constraints around the
world allow to confirm that subduction of active spreading ridges
triggers significant changes in the behavior of the upper plate
continental lithosphere, inducing notably subsidence and attenuation of
former cordilleras. 

\subsection{North East-Pacific: from Aleutian-Alaska to Central America}\label{sec51}

The North-Eastern Pacific margin is integrated into a long-lived
history of oceanic subductions beneath continental lithosphere
involving oceanic plates or micro-plates since the Mesozoic. Most of
these continental active margins exhibit high-elevation cordilleras in
response to magmatic and tectonic crustal thickening. Through time,
compressional shortening was not the unique factor of tectonic
evolution of the North-Eastern cordilleras as evidenced by several
phases of extensional deformation related to the complex and long-term
subduction of spreading ridges. In this section, we describe how active
spreading ridge subductions during the Cenozoic induced particular
changes in the tectono-magmatic evolution of cordilleras from
Aleutian-Alaska to the Central America region. 

\subsubsection{Subduction of active spreading ridges along the
North-Eastern Pacific since the Cenozoic}\label{sec511}

During the Cenozoic, the northwestern margin of North American plate
(including the East Aleutian arc, Alaska, British Columbia and Oregon)
was the site of multiple active spreading ridge subductions
\citep{Breitsprecheretal2003,FustonWu2020,Madsenetal2006,Mulleretal2008,Mulleretal2016,Sissonetal2003,SissonPavlis1993,Thorkelsonetal2011}. 
Cenozoic plate kinematic reconstructions highlight three subductions of
oceanic plates/microplates located northward of the Pacific plate,
namely the Resurrection, the Kula and the Farallon plates
(Figure~\ref{fig8}) \citep[e.g.][]{FustonWu2020,Madsenetal2006}. These
plates were separated by four spreading axes: the Kula/Resurrection
Ridge (KRR); the Resurrection/Farallon Ridge (RFR), the Kula/Farallon
Ridge (KFR) and the Pacific/Farallon Ridge (PFR); all of them were
progressively subducted beneath the North American plate\break (Figure~\ref{fig8}).

\begin{figure*}
\includegraphics{fig08}
\caption{\label{fig8}Cenozoic plate configuration around the
northwestern American margin and synthesis of tectono-magmatic events
at 70~Ma, 50~Ma and 30~Ma. Positions of active spreading ridges and slab
windows come from \citet{Madsenetal2006} and \citet{FustonWu2020}. KRR:
Kula/Resurrection Ridge; KPR: Kula/Pacific Ridge; RFR:
Resurrection/Farallon Ridge; KPR: Kula/Pacific Ridge; PFR:
Pacific/Farallon Ridge.}
\end{figure*}

\subsubsection{Aleutian-Alaska}\label{sec512}

The Alaska active continental margin offers a clear example of the
transition between an elevated \mbox{subduction} cordillera, the Alaska belt,
to a low {elevation} belt, finally passing to a succession of volcanic
islands forming the Aleutian arc \citep{Jichaetal2004}. The
significance of such a rapid transition between a high elevation
cordillera to an island arc is not yet explored and no evidence of
dramatic crustal extension was reported at the Alaska western
border, in the transition to the Bering sea. Due to the geometry of the
NW--SE KRR with respect to the arcuate active margin, the 
KRR/North America triple junctions followed two different
configurations (Figure~\ref{fig8}): a high-angle intersection from the
Aleutian to the Sanak-Baranof (Alaska) margins from 80--55~Ma and a
low-angle intersection along the northern British Columbia between
50--35~Ma
\citep{Breitsprecheretal2003,ColeStewart2009,FarrisPaterson2009,FustonWu2020,Kuskyetal1997,Madsenetal2006,Sissonetal2003}. 


Together with the CTJ region, the eastern Aleutian arc has long been a
reference for studies of slab window effects. It has been shown that
slab window opening has a profound influence on continental margin
magmatism with the formation of mantle-derived magmas intruding
accretionary wedges. The upwelling of suboceanic mantle beneath a
continental margin triggers the generation of magmas by partial melting
of overlying crustal rocks and/or by decompression melting of the
upwelling mantle \citep{ColeStewart2009,Coleetal2006,DOrazioetal2001,Sissonetal2003,SissonPavlis1993}.

When considering the tectonic evolution of cordilleras, it is important
to point that the Aleutian arc region and southern Alaska slab window
volcanism was coincident with HT-LP metamorphism and crustal extension
\citep{Bradleyetal2003,Groomeetal2003,Iwamori2000,Sissonetal1989,Underwoodetal1999}.
Zones of local extension developed within arc-front, forearc, and
accretionary prism settings. For example, the late Paleocene to Eocene
Caribou Creek volcanic field (Southern Alaska) was erupted in a zone
of extension that trended orthogonally to the continental margin
(Figure~\ref{fig8}) \citep{Bradleyetal2003,ColeStewart2009}. Infra-arc
tectonic extension caused long-arc differences in the nature of
crystallization, facilitated by changes in the thermal and density
structure of the subarc lithosphere
\citep{SingerMyers1990,Singeretal1992}. \citet{ColeStewart2009} note
that in order for basalts or gabbros to retain their mantle signature,
the mafic magmas need pathways to reach shallow crustal \mbox{levels}. These
pathways are more easily formed during crustal extension. Crustal extension
was also described in the Alaskan back-arc domain coeval to
alkaline magmatism right above the slab-window (Figure~\ref{fig8})
\citep{Bradleyetal2003}. Locally, HT-LP metamorphism was 
associated with Metamorphic Core Complex exhumation as shown around the
central margin of Alaska [53--50~Ma Chugach MCC,
\citealp{PavlisSisson1995,SissonPavlis1993}].

\subsubsection{Northern American Cordillera}\label{sec513}

After a Mesozoic--Early Cenozoic complex evolution of terrane
accretions along the Northern America Cordillera 
\citep[see][for a synthesis]{Clennettetal2020}, 
the entire Northern American
active margin has been subjected to spreading axis subductions.
Synchronously to the eastward subduction of the KRR along the Alaskan
margin, the RFR entered the subduction along the Northern American
Cordillera (Figure~\ref{fig8}) \citep[e.g.][]{FustonWu2020}. The
related triple junction migrated northward close to the Vancouver
Island \citep{Madsenetal2006,FustonWu2020}. Since Late
Eocene--Oligocene times, multiple slab-windows related to KRR, RFR and
KFR subductions have developed inducing a composite large-scale pathway
for asthenospheric flows still observable beneath British Columbia
(Figure~\ref{fig8}) \citep{Breitsprecheretal2003,SeveringhausAtwater1990,Madsenetal2006,Thorkelsonetal2011}. 
A composite
slab-window is also responsible of the break-off of the Resurrection
slab [the ``Yukon'' slab according to \citealp{FustonWu2020}] forcing the
dynamics of the British Columbia margin to switch from a convergent to a
transcurrent lithospheric boundary at 40~Ma (the Queen Charlotte
dextral fault system). Today, the Juan de Fuca oceanic plate (a remnant
of the Farallon plate) intersects the continental margin with
two related triple junctions, the Explorer Triple junction close to
Vancouver Island and the Mendocino triple junction north of the
Californian\break state. 

Before slab-window interactions, the North American Cordillera was
the site of a complex magmatism evolution inducing two main igneous
domains from west to east and separated by a North--South Sr--Nd
isotopic limit: the western Cordillera mainly dominated by mantle
magmas and the eastern Cordillera with crustal magma affinities
\citep{KistlerPeterman1973,Leemanetal1992}. The Cenozoic-Quaternary
influence of hot asthenospheric flow through slab-window and/or gaps is
well evidenced by studies of magmatic products from the forearc and
back-arc domains. During Eocene--Oligocene times, the voluminous forearc
magmatism of the Canadian Cordillera bears tholeiitic and alkalic
signatures and was emplaced in an extensional/transtensional setting
(Figure~\ref{fig8})
\citep{BarnesBarnes1992,Davisetal1995,HamiltonDostal2001,Thorkelsonetal2011}. 
More inland, the Cenozoic Canadian magmatism varies from north to south.
Intraplate magmatism signature is localized along a major part of the
British Columbia Cordillera, whereas the Cascadian Arc exhibits a
typical calc-alkaline character (Figure~\ref{fig8})
\citep{Thorkelsonetal2011}. A key feature of the Cenozoic magmatic
evolution occurred at ca. 47~Ma with the cessation of arc-like
magmatism switching to an intraplate activity from Late Oligocene to
Holocene \citep{EdwardsRussell2000,Madsenetal2006,Thorkelsonetal2011}.
This transition occurred during the development of the Northern
Cordillera slab-window, below a 1500~km-long transect from south
British Columbia to the northwestern tip of Canada. Along this last
region, adakitic magmatism was emplaced just above the slab-window edge
(Figure~\ref{fig8}) \citep[e.g.][]{Thorkelsonetal2011}. The Northern
American Cordillera is also characterized by a change in the
deformation regime. Until early Cenozoic times, a compressional regime
was responsible for crustal thickening, metamorphic core complex
(MCC) initiation and Andean Altiplano-like cordillera
\citep{ConeyHarms1984}. This stage is followed in Cenozoic times
(starting in the Eocene) by tectonic extension inducing thinning of the
crust and denudation of MCC \citep{ConeyHarms1984}. The present
architecture of the British Columbia and Washington region derives
mainly from this Eocene extensional event \citep{Parrishetal1988}. For
\citet{EdwardsRussell1999}, the Northern Cordilleran Volcanic Province
can be considered as a northern Basin and Range model where MCC are
associated with HT-BP metamorphism (Figure~\ref{fig8}). This is the
case for the Early-Middle Eocene complexes of the Leech River (south of
Vancouver Island) \citep{Groomeetal2003} and the Challis--Kamloops
(south of British Columbia and northwest of United States) where
magmatism occurred during the formation of a pull-apart basin~and MCC
exhumation \citep{Breitsprecheretal2003,Parrishetal1988}. Finally, high
heat flow and thin lithosphere of the northern Cordillera [60--52~km,
\citealp{HarderRussell2006}] demonstrate the impact of the thermal
erosion of the lithospheric mantle linked to hot mantle upwelling.

\subsubsection{California and Basin and Range}\label{sec514}

South of the Northern Cordillera, the California margin was also deeply
affected by active spreading ridge interaction. During the Oligocene,
the PFR entered the subduction (Figure~\ref{fig8}) and a
PFR-related transform fault collision (probably) led to the initiation
of the transcurrent dextral fault system of San Andreas
\citep{Atwater1970,DickinsonSnyder1979,SeveringhausAtwater1990}.
From 30 to 15~Ma
the progressive opening of a slab window led to subsequent active
mantle upwelling beneath the western United States. Two triple
junctions, the Mendocino and Rivera triple junctions, then migrated in
opposite directions along the continental margin in relation with the
growth of the San Andreas transform fault. The slab window continued to
widen as both triple junctions propagated north and south. This process
explains the shutdown of the previous magmatic arc as the San Andreas
Fault\break developed.


\citet{Fernandesetal2019} realized a synthesis of Cenozoic topographic
evolution of Northwestern and Western America coupling stratigraphic
and geomorphic markers. They highlight a series of uplift pulses
characterized by a total of more than 2~km high long-wavelength surface
uplift. Correlations between thermochronology, magmatism and
syntectonic sedimentation analysis also suggest that a Late Mesozoic
regional compressive regime evolved toward a regional extensional
regime also described northward by \citet{ConeyHarms1984} 
\citep[see][for references]{Fernandesetal2019}. This overall extensional
deformation is well documented in the Basin and Range Province where
Late Oligocene?--Miocene MCC  formed (Figure~\ref{fig8}).
These features accommodate considerable amounts of horizontal
displacements in the middle crust along low-angle normal faults. In the
upper crust, normal faulting with high angle faults control the
formation of numerous grabens and subsiding basins infilled by
syn-extensional sediments
\citep{Fauldsetal1990,FauldsR.J.Varga1998,Malavieille1987,Vargaetal1996,Wernicke1981,Wernicke1985,Wernickeetal1987,Wernicke2009}. 
This area was also subjected to mid-Miocene intensive intraplate
eruption from the Colorado River Plateau
\citep[][for references]{Dickinson1997,Dickinson2006,Robertsetal2012}
to the south of California \citep{ColeBasu1992,Wilsonetal2005}.

\citet{Dickinson1997} and \citet{DickinsonSnyder1979} first pointed to
the correlation between extensional tectonics in the Basin and Range
Province and the opening of the slab window beneath western North
America. They suggest that upwelling asthenosphere heated the base
of the lithosphere and caused its weakening. The hypothesis of a hot
mantle anomaly is enhanced by the regional-scale uplift that does not
involve crustal thickening \citep{Lewandowskietal2018}. \looseness=1

Therefore, the dynamic topography observed in California and surrounding
areas reflects long-term thermal anomalies driven by asthenospheric
upwelling through slab-windows or related-slab-window gaps. These deep
processes have induced the thinning of the lithosphere [ca. 70~km;
\citealp{Klolclingetal2018}] via thermal erosion of the lithospheric
mantle and extensional deformation of the upper plate since middle
Cenozoic. We must note that in the Basin and Range region, the
extensional tectonics applied to a former collisional orogen having a
thickened crust. This allowed the continental crust to return to a
former thickness of 30~km by extensional collapse
\citep{Dewey1988,ConeyHarms1984}. 

\begin{figure*}
\includegraphics{fig09}
\caption{\label{fig9}Cenozoic plate configuration around the Central
American margin and synthesis of tectono-magmatic events at 20~Ma, 
10~Ma and 5~Ma. Position of the active spreading ridges from 20~Ma 
{and}
5~Ma come from \citet{BourgoisMichaud2002,JohnstonThorkelson1997,
Morell2015}. PFR: Pacific/Farallon Ridge; CNR:
Cocos/Nazca Ridge; SAF: San Andreas Fault; SAM: South American Plate.}
\end{figure*}

Comparisons between the northern and southern cordilleras of North
America finally confirm that the context of active ridge subduction
impacts a large panel of characteristics of the overriding plate.
Switches from convergent to transcurrent boundary conditions
(transcurrent strike-slip systems of Queen Charlotte and San Andreas
Faults) associated with hot asthenosphere flowing through slab window
favor extension of cold lithosphere. In this context, the variability
of extension styles affecting the cordilleras is controlled by the
rheological and thermal state of the overriding crust
\citep{Buck1991,Reyetal2001}. 

\subsubsection{Baja California}\label{sec515}

The Baja California and western regions of Mexico mainlands (from
Sonora to Jalisco) belong to the southern part of Laramide orogen.
During Cretaceous to Eocene times, they experienced a
magmatic-tectonic evolution in relation to the subduction of the
Farallon plate beneath the \mbox{northern} America plate, involving
variability of subduction rates and slab dips
\citep{ConeyReynolds1977,Engebretsonetal1985,Ferrarietal2006,Keith1978}. 
Progressive eastward subduction of oceanic plates was also responsible
for the middle Miocene to Present recycling of the East Pacific Ridge
(EPR) beneath Baja California and Mexico, where the Mexico triple
junction has migrated to the south with trench-parallel slab window
opening (Figure~\ref{fig9})
\citep{BourgoisMichaud2002,Michaudetal2006}. During the early
Pliocene, the fragmentation of the Pacific plate leading to the
creation of the Rivera plate, induced a jump of the triple
junction, which is now located southeastward
\citep{BourgoisMichaud2002,Michaudetal2006}. Contemporaneously to the
Basin and Range Province, Baja California and the western Mexican
region were affected by Late Oligocene--Late Miocene continental-scale
extension responsible of OIB-type magmatism in the upper plate and of
the initiation of Metamorphic Core Complex exhumation
(Figure~\ref{fig9}) \citep[see][for references]{Calmusetal2015}. The
overall regions experienced a major alkaline magmatic event, dated from
11~Ma to present, with volcanics emplaced along an E--W trending
corridor from Jalisco to Mexico City \citep{Ferrarietal2006}. To the
northwest, the Gulf of California corresponds to a 1300~km-long
corridor extending from the southern tip of the San Andreas Fault to
the Mexico triple junction to the south. On the western flank of the
Gulf of California, the presence of bajaites with adakitic magmatic
affinities, suggests \mbox{subduction} of a very young oceanic lithosphere
(Figure~\ref{fig9}) \citep{AguillonRoblesetal2001}. Based on these
results, \cite{BourgoisMichaud2002} propose that the slab window
development beneath southern Baja California and mainland Mexico
(30\textdegree~to 18\textdegree~N) resulted from the subduction of the
East Pacific rise.

Oblique rifting in the Gulf of California and extensional deformation
in the surrounding regions of Mexico were accentuated from 12~Ma
to 6~Ma (Figure~\ref{fig9})
\citep{StewartRoldan-Quintana1994,StockHodges1989}. Crustal extension
is correlated with a regional scale uplift 
\citep[e.g.][]{Calmusetal2015,Ferrarietal2013,Marketal2017} with a notable
increase of uplift rates (0.1 to 0.2~mm/yr) starting at 15~Ma 
\citep[see][for a synthesis]{Stephensonetal2014}. Recent extension, local
uplift and alkaline magmatism are associated with high surface heat
flow from 83 mW/m$^{2}$ to $90 \pm 27~\mathrm{mW}/\mathrm{m}^{2}$ 
\citep{Ziagosetal1985,Perez-Camposetal2008}, suggesting a mantle
origin for these surface processes. As indicated by
\citet{BourgoisMichaud2002}, oblique rifting and oceanic seafloor
spreading in the Gulf of California occur right above the slab window
related to the subduction of the EPR (Figure~\ref{fig9}). During its
southeastward migration, this window allowed upwelling of
asthenospheric flows inducing progressive weakening of the continental
lithosphere and subsequent increase of extension and magmatism in the
upper plate.

\subsubsection{Central America}\label{sec516}

Central America, and more specifically Costa Rica and Panama, are
the site of the interaction of multiple plates including the North
American, South American, Cocos, Nazca and Caribbean plates. The
Cocos--Nazca spreading system initiated at around 25~Ma
\citep{Hell1977} and progressively subducted beneath the Central
America (Figure~\ref{fig9}). Thus, between 10~Ma and 2~Ma, Central
America was swept by a restricted slab window, the Panama
slab-window, related to the buried Cocos--Nazca spreading axis (CNR,
Figure~\ref{fig9}) \citep{JohnstonThorkelson1997,Thorkelsonetal2011}.
At present, the corresponding triple junction corresponds to a
trench--trench--transform configuration where the subduction of the
Panama Fracture Zone forced the \mbox{northeastward} movement of the
slab-window \citep{JohnstonThorkelson1997}. Magmatic interactions of
the Panama slab window on the Costa Rica/Panama areas and on the
Caribbean plate are well-documented. Here, late Miocene to Pleistocene
dacites and rhyolites rocks with adakitic signatures located in the
forearc of Panama and southern Costa Rica correspond to the trailing
edges of the slab-window (Figure~\ref{fig9})
\citep{JohnstonThorkelson1997}. OIB-type magmatic activity is also
observed onland, on the Caribbean plate whereas Nicaragua, El Salvador
and Guatemala lavas display arc compositions (Figure~\ref{fig9}).
Therefore, the Panama slab window corresponds to a pathway for
voluminous flows of enriched sub-slab peridotite into the arc and
back-arc domains \citep{JohnstonThorkelson1997}. Based on geochemistry
analysis of hydrothermal fluids, \citet{Bekaertetal2021} confirm that
the Panama window allows eastward intensive asthenospheric flows coming
from the Galapagos hot spot. This observation correlates with seismic
anisotropy data showing W--E trending flows beneath the Caribbean plate
\citep{RussoSilver1994}. Tectonically, the evolution of the region
results from several phases of deformation related to: (1) the subduction
of the Cocos plate, (2) the subduction of the ridge-transform system of
Nazca--Cocos, (3) the opening of the Caribbean basin and, (4) the
subduction of the aseismic Cocos ridge.

In central America, an epeirogenic uplift event occurred between 10 and
6~Ma with north-striking late Miocene--Holocene grabens
(Figure~\ref{fig9}) disrupting a middle-Miocene ignimbrite layer
\citep{Rogersetal2002}. These authors attribute this event to an
upwelling of mantle asthenosphere through a tear linked to the slab
detachment during the Cocos ridge collision. Nevertheless, the uplift
and the trench-orthogonal extensional deformation are synchronous with
the slab-window development beneath the southern Central America
(Figure~\ref{fig9}). In such a configuration, voluminous mantle flows
from the Galapagos hot-spot may have disrupted the thermal state of the
upper plate further north and east from the predicted slab-window
position. Finally, this region is governed by complex interactions of
subduction processes, involving normal subduction, recycling both
spreading and aseismic ridge in a short time. In consequence, the 4D
evolution of the mantle dynamic beneath Central America and its impacts
on the upper plate remain difficult to fully assess. 

\subsection{West-Pacific: from the Philippine Sea plate to the Kuril
arc}\label{sec52}

{\advance\baselineskip by .3pt
The West Pacific active margins include subduction of oceanic
lithosphere beneath both continental and oceanic lithosphere. The
continental active margins forming the easternmost edge of the Eurasia
plate are characterized by relatively low elevation regions and the
lack of prominent active compressional cordilleras (Kamchatka, Kuril,
Japan). By contrast to the margins of North and South America, the
Western Pacific continental margins exhibit a number of back-arc basins
resulting from the extension of the continental crust and/or intra-arc
tearing, and subsequent localized accretion of oceanic crust. These
basins show complex histories, but opened generally in a short time
span, between 30 to 10~Ma \citep{Parketal1990}. In this section, we
first describe the subduction of the Izanagi--Pacific Ridge (IPR)
beneath the Eurasian margin during Cenozoic times. We further focus our
discussion on some local and regional geological consequences of the
IPR subduction and its migration through the Philippine-Borneo region,
the South China Sea, Japan and Kuril\break regions.

\subsubsection{Subduction of the Izanagi--Pacific Ridge and Wharton
Ridge along the Eurasian margin}\label{sec521}

During Mesozoic to Cenozoic times, the Eurasian margin along East Asia
was affected by extensive subduction along an up to 6000~km long active
margin \citep{Mulleretal2016,Torsviketal2019} including several
related processes including trench retreat, slab roll-back and
subduction of active spreading ridges. Process of spreading ridge
subduction has been described for several decades especially in the
regions surrounding Japan coastlines. Here, two opposites
reconstructions of interaction between the Asian margin and active
spreading ridge have been proposed involving the Izanagi--Pacific Ridge
(IPR). The first one, suggested by \citet{Maruyamaetal1997}, corresponds
to a frontal ridge--trench interaction where the IPR intersects the
Asian continental margin at a high angle. The related
trench--trench--ridge triple junction migrated from south to north from
Late Cretaceous to Eocene times. The second one, based on large-scale
reconstructions of the Pacific hemisphere starting at 140~Ma 
\citep{Mulleretal2008}, \mbox{hypotheses} that the western part of the Pacific
floor was created by a NNE--SSW, 3000~km-long spreading ridge
that kept remarkably parallel to the active margin of Eurasia between
110 and 70~Ma. In this reconstruction (Figure~\ref{fig10}), a low-angle
ridge--trench interaction was proposed where the IPR entered the
subduction zone in one piece between 60 and 50~Ma
\citep{Whittakeretal2007,Setonetal2015,WuWu2019}. This implies that
the entire border of the Eurasian plate was concerned by the
opening of a mega-slab window continuously widening beneath the
continent as subduction continued. In addition, high-resolution
tomography records of East Asian mantle as well as numerical modelling
of mantle structure and dynamics provide spectacular images of a large
slab-window opened between the Izanagi and Pacific plates following the
early Cenozoic subduction of the active IPR \citep{Wuetal2022a}.
Recent kinematic models confirm the low-angle Izanagi--Pacific
ridge--trench interaction with Eurasia at $50 \pm 10$~Ma but limit
the ridge subduction between Korea, Japan and the Russian Far East
\citep{Wuetal2022a} instead of \citet{Mulleretal2008} models that
involve the entire East Asian margin from Borneo to Kuril areas
(Figure~\ref{fig10}). An active spreading subduction process is also noted
along the southwestern tip of the East Asian margin. From Late
Cretaceous to Early Eocene periods, the northeastward subduction of the
Wharton Ridge (WR), an active spreading ridge between Indian and
Australian plates (Figure~\ref{fig10}), led to the development of a
slab window beneath the Sundaland \citep{Whittakeretal2007}. The
entire region was concerned by two opposite-vergent subductions of
spreading axis: the IPR with a southwest vergence and the Wharton ridge
with a northeast vergence\break (Figure~\ref{fig10}).

\begin{figure*}
\includegraphics{fig10}
\caption{\label{fig10}Cenozoic plate configuration around the
Southeast Asian margin and synthesis of tectono-magmatic events at
70~Ma, 50~Ma and 30~Ma. Position of active spreading ridges at 70~Ma
come from \citet{Mulleretal2008,Whittakeretal2007}. IPR:
Izanagi/Pacific Ridge; WR: Wharton Ridge; RFE: PSP: Philippine Sea
Plate; Russian Far East; SCB: South China Block; ECSB: East China South
Block; PRMB: Pearl River Mouth Basin; QDNB: Qiongdongnan basin.}
\end{figure*}


\subsubsection{The Philippine and Borneo area}\label{sec522}
The Philippine and Borneo Region (PBR) was affected by a
long-lived subduction process since Mesozoic times causing complex and
spectacular opening of back-arc extensional basins together with
various magmatic signatures on the upper plate 
\citep[see][for references]{Burton-JohnstonCullen2022}.
The rifting history of South China
Sea region, including Philippine and Borneo, shows the initiation of
extensional deformation lasting from 62~Ma to 45~Ma
\citep{Cullen2010,Zhangetal2020}. This event is well
documented in the Dangerous Grounds, where Paleocene to Middle-Eocene
extensional deformation causes continental rifting between 
\unskip\break\mbox{Vietnam},
Indonesia and Borneo Islands (Figure~\ref{fig10}) 
\citep[e.g.][]{Burton-JohnstonCullen2022}. 
To the east, rifting started from 50 to 40~Ma and
was responsible for the extension in the Celebes and Sulu basins
(Figure~\ref{fig10}), followed by initiation of oceanic spreading at
45~Ma and 35~Ma respectively \citep[e.g.][]{Burton-JohnstonCullen2022}.
The early Cenozoic intraplate rifting event in this region is well
documented by: (1)~regional geology, (2)~geochemical evolution
characterized by low volumes of OIB magmas, and (3)~geophysical data.
\citet{Burton-JohnstonCullen2022} suggest that slab retreat is a
dominant process able to trigger extension in the Celebes and Sulu
basins and exclude extrusion, mantle plume or slab pull of the
Proto-South China Sea subduction. Their model of extension during the
Cenozoic period also shows that an active spreading ridge center
interacted with the eastern margin of SE Asia during the Eocene 
but do not discuss its impact on the evolution of the overriding plate.
Kinematic reconstructions by \citet{Mulleretal2008} show that the PBR
was affected by the Early Cenozoic subduction of the NE--SW
IPR. In this configuration, the IPR interacted with the SE
Asian margin southeast of Borneo and migrated northeastward
inducing the progressive opening of a large slab-window beneath the PBR
(Figure~\ref{fig10}). Together with IPR recycling, the Wharton Ridge
subducted leading up to the opening of a slab window beneath the
southern tip of Borneo region (Figure~\ref{fig10}). Rising of hot
material during this time induced dynamic uplift with basaltic
magmatism in Borneo and Indochina and surrounding extensional basins
since the Early Cenozoic \citep{Fyhnetal2009,Robertsetal2018,Yanetal2018a}.
It is important to point that in such reconstructions, the
entire region was the site of a complex subduction process involving a
double opposite-vergent subduction of active spreading ridges (IPR to
the east and Wharton to the west) from 65 to 45~Ma
(Figure~\ref{fig10}). This situation was responsible for the opening of
a double opposite slab-window allowing upwelling of a large amount of
hot asthenospheric mantle, triggering in turn the initiation of
lithospheric extension in the upper plate, coupled with intraplate
OIB-type magmatism during late Cretaceous to Early Cenozoic times. 
}

\subsubsection{South East China}\label{sec523}

\vspace*{3pt}

During Permian to Early Cretaceous times, South East China was marked
by the development of subduction-type orogens, locally thickened by
accretion of mantle-derived magmas. Emplacement of large amounts of
Mesozoic granitoids in South East China was accompanied by thermal
softening and gravitational instability allowing extension of the crust
\citep{Faureetal2016}. Therefore, during Middle Jurassic to Late
Cretaceous times, the Pacific coastal region of China was characterized
by Basin and Range type province, notably in the South China block (SCB).
But this widespread Mesozoic extensional event cannot be related to any
documented slab window development beneath the region
\citep{Faureetal2016,WangShu2012}. 

During the Late Cretaceous-Cenozoic, the tectonic evolution of the
South China domain was controlled by successive stages of
subduction of the Pacific lithosphere including the subduction of the
IPR beneath the Eurasia active margin (Figure~\ref{fig10}) 
\citep[e.g.][]{Brownetal2022,Wangetal2022}. A recent analysis of present
residual topography indicates an abnormal hot mantle beneath the entire
East Asian margin \citep{Hoggardetal2017,Hoggardetal2021}. This
hot anomaly has produced local to regional dynamic uplift and
subsidence, evidenced by a series of geological records as follows. 
(1)~To the south, the northern margin of the South China Sea 
experienced uplift events since the Eocene coupled with syn-rift
tectonic subsidence \citep[e.g.][]{Brownetal2022}. This is the case
for the Pearl River Mouth Basin (PRMB) where \citet{Suoetal2020}
describe an Early Eocene narrow rift followed by a Late Eocene wide
rift governed by detachment faults (Figure~\ref{fig10}). 
(2)~\cite{Suoetal2020} also suggest that the East China Sea Basin (ECSB)
located several hundred kilometers to the northeast, recorded a
similar evolution in relation to hot asthenospheric flows
(Figure~\ref{fig10}). (3)~South West of the PRMB, the Qiongdongnan
basin (QDNB) was affected by an uplift of approximatively 1~km
from 30~Ma to 25~Ma \citep{Xieetal2006,Zhaoetal2021} with a lack of
compressional deformation \citep{CliftSun2006}. Here, intraplate
volcanism was emplaced synchronously during the uplift event 
\citep[e.g.][]{Brownetal2022}. During this period, local narrow to wide
rift-related basins developed, concentrating syn-extension
sediments (Figure~\ref{fig10}) \citep{CliftSun2006,Wangetal2021}. 
(4)~Northward, the South China Block (SCB) 
experienced a Miocene~km-scale uplift inducing a regional erosional
event at this time
\citep{Cullenetal2010,Morley2016,PubellierMorley2014,Wangetal2017,LiZou2017,Wangetal2021,Yanetal2018b}.
Similarly to other regions, this uplift is associated with intraplate
alkaline volcanism and is interpreted as a consequence of hot
asthenospheric flow below the SCB. (5)~The multi-stage extension event
evidenced in this region was also revealed at the scale of the
South China Sea by apatite fission track studies \citep{Wangetal2022}.
The thermal history modeling reveals successive cooling stages: a rapid
cooling process during ca. 80--50~Ma, a slow cooling process during ca.
50--35~Ma and another rapid cooling process during ca. 35--12~Ma. The
slow cooling stage can be linked to the subduction of the
Izanagi--Pacific spreading ridge \citep{Wangetal2022}. 

Based on Pacific plate kinematic reconstructions,
\citet{Mulleretal2008} propose an
interpretation of the interaction of the IPR with the South Asian
margin, showing a mega-ridge subduction between 70 and 50~Ma
(Figure~\ref{fig10}). We saw that the main event recorded in the
upper plate continental region in response to this kinematic event
corresponds to local and regional dynamic uplift associated with OIB
volcanism. In addition, extensional deformation across the entire
region is responsible for major rift-related basin opening,
testifying for tectonic subsidence from Eocene to Late Oligocene times
(Figure~\ref{fig10}). At a large scale, the stratigraphic records
indicate a Late Eocene--Oligocene N--S regional scale uplift up
to 3,000,000~km$^{2}$ affecting Eastern China and the northern~margin
of China Sea \citep{Brownetal2022} with westward migration towards the
South China Block during the Miocene. In addition, OIB magmatism
observed from Indochina to the South China Block and extending
northward to China and Korea, illustrates the prominant role of
asthenospheric flows during Cenozoic times (Figure~\ref{fig10}). 

To sum up, we may conclude that at 60~Ma, the IPR subducted with a
low angle beneath the continental Asia upper plate leading to the
progressive development of a large slab-window beneath the South East
Asian margin (Figure~\ref{fig10}). This large window probably served as
a major pathway for Pacific asthenosphere to flow beneath the entire
East Asia during Middle to Late Cenozoic \citep{Brownetal2022}. Today,
there is no evidence of the 3D geometry of this window, nevertheless as
reported above, recent geophysical studies indicate abnormal hot
asthenopheric mantle below the upper plate \citep{Zhaoetal2021}. We
are well aware that the Late Cenozoic to Quaternary regional
deformations across the South East Asian margin can be attributed to
additional subduction processes such as trench retreat and slab
roll-back with far-field consequences of the Indian collision. However,
based on this review, we may claim that correlations between uplift,
intraplate volcanism and extensional deformation above the IPR
slab-window during Cenozoic times can be \mbox{attempted.} 

\subsubsection{Japan}\label{sec524}

Along the Eurasian margin, the Japanese Islands and associated southern
Russian Far East (RFE) represent a well-preserved testimony of
subduction history since Mesozoic times 
\citep[e.g.][]{Mulleretal2016}. The Japan and the Kuril basins located
northeast of the Japan islands are currently concerned by the
subduction of the Pacific plate whereas the Okinawa and South China
basins located south of Japan are concerned by the subduction of the
Philippine Sea plate. This was not the case at the beginning of the
Cenozoic when most of the margin was affected by the subduction of the
Izanagi and Pacific plates (Figure~\ref{fig10}), before the growing up
of the Philippine Sea plate at 50~Ma
\citep{Lallemand2016,Liuetal2022,Wangetal2022,WuWu2019}. 

During Late Jurassic--Cretaceous times, the Japanese Islands were
characterized by an Andean-type cordillera where distributed igneous
rocks and accretionary prisms developed in relation with
subduction processes \citep{Tairaetal2016,Wakitaetal2013}. The Japan
Sea opened in the Early Miocene in a broad pull-apart zone between two
major NNE--SSW dextral strike-slip shear zones 
\citep{Jolivetetal1994,LallemandJolivet1986}. The first one extends from north
Sakhalin to Central Japan along 2000~km and accommodated 400~km of
displacement, the second one, between Korea and SW Japan, accommodates
displacement of about 200~km. Here, the extensional domain between
these two transcurrent faults forms the back-arc region of Japan with a
westward spreading propagation inside the pull-apart region
(Figure~\ref{fig10}). The basin of the Japan Sea can be viewed first as
a back-arc basin opened in relation with the subduction of the Pacific
plate \citep{Otofujietal1985,UyedaKanamori1979,VanHorneetal2017},
but additional processes
can be involved, notably because oceanic back-arc spreading is not
parallel but orthogonal to the trench direction
\citep{Sato1994,Yamamoto1991}. For some authors 
\citep[see review in][]{Mantovanietal2001}
crustal extension occurred in the wake of the
Japan arc, which was forced to bend by extrusion between compressional
boundaries involving the Okhotsk block and Eurasia. According to
\citet{Jolivetetal1994}, internal deformation of Asia due to collision of
India has also to be considered. For \citet{Tatsumietal1989}, the
back-arc extension of the Japan Sea occurred between 21~Ma and 14~Ma in
response to an asthenospheric injection into the mantle wedge due to a
change in the dip of the subduction. Evidence comes  from the migration
of the arc that can be traced to the surface. During the Oligocene (ca.
30~Ma), the volcanic front was located along the western coast of the
present Northeast Japan and migrated about 200~km trenchwards at 23~Ma,
before the opening of the Sea of Japan. Therefore, the angle of the
subduction became steeper during the period of 30--23~Ma. The
\citet{Tatsumietal1989}'s model does not involve slab tear nor slab
window opening. However, it shows similarities with slab window
configuration but upwelling comes from above the slab and does not
originate in part from the sub-slab region. The forearc region of
northern Japan underwent spectacular tectonic erosion revealed by the
subsidence of a regional subaerial unconformity and normal faulting
that started 22~Ma ago \citep{VonHueneLallemand1989}. \looseness=-1

Interaction of the IPR with the Japanese margin has been documented
for several decades at a regional, in particular along the NE--SW
accretionary belt of Shimanto (Figure~\ref{fig10}). This
accretionary wedge is composed of Cretaceous to Neogene sedimentary,
magmatic and metamorphic units that record some typical influences
of slab-window related to active spreading ridge subduction. The most
spectacular event includes: (1) near-trench MORB-type magmatism, (2)
abnormal fore-arc thermal event with OIB volcanism, (3) adakites
intrusions, (4) HT-BP metamorphic events, (5) gap in sedimentation
along the forearc and, (6) erosion at the trench wedge
\citep{HibbardKarig1990,Iwamori2000,Kinoshita2002,MaedaKagami1996,Osazawa1992,Sakaguchi1999,WuWu2019}.
From a tectonic point of view, the Shimanto belt is characterized
by a progressive switch of deformation, from a Paleocene--Early Eocene
compressional stage allowing the growing up and the thickening of the
prism, to an erosional stage of the margin followed by the collapse of
the prism with extensional faulting 
\citep[e.g.][]{Iwamori2000,Osazawa1992,Raimbourgetal2013,Raimbourgetal2014,Raimbourgetal2017,UeharaAoya2005}.
This evolution was principally governed by the subduction of the
IPR below the Japanese margin.\looseness=-1

Landward from the southern margin of the Japan Sea to the Sakhalin
Peninsula (Russian Far East), a compilation of magmatic records from
Cretaceous to Eocene times highlights the impact of the IPR subduction
and the development of the related slab-window (Figure~\ref{fig10}).
For instance, \citet{WuWu2019} assign the magmatic gap from 56 to 46~Ma
along the NE Asian margin to the IPR subduction. After this hiatus,
Late Eocene igneous activities bear a more depleted mantle signature
with respect to older rocks, consistent with hot-depleted mantle
circulation into the mantle wedge allowed by slab-window
\citep{WuWu2019}. Dynamic topography effects are also reported in the
upper plate. This is the case for the Sangliao basin at the northern
margin of the Japan Sea (NE China) where an Early Eocene regional
unconformity was identified \citep{Songetal2014,Wangetal2013}.
Apatite fission-track dating also suggests intense uplift related to
heat upwelling during Early Cenozoic times, from 65 to 50~Ma, in this
region \citep{Pangetal2020}. 

Finally, our compilation of geological data shows that the tectonic and
magmatic events affecting the Japan margin during the Cenozoic are
globally asynchronous and did not occur during the first stages of the
subduction of the IPR (Figure~\ref{fig10}). Indeed, dynamic uplift
occurred from 65--50~Ma to 45~Ma, the magmatism gap was bracketed
between 56 and 46~Ma and depleted mantle-related magmatism was emplaced
since from 46~Ma. As shown previously, back-arc basins opening occurred
during the Oligocene--Miocene times, but some authors suggest that they
may have initiated in the Late Cretaceous--Early Eocene
\citep{SchellartLister2005}. Therefore, back-arc basins appear to be
30--20~Ma younger than the IPR subduction and do not coincide exactly
with the initiation of slab-window opening below the region. Such a time
offset between ridge subduction and continental lithosphere extension
can be interpreted as a late response of a thick Eurasian lithosphere
(Andean-type orogen) at the time of the IPR \mbox{subduction.} The thermal
effect of asthenospheric mantle flowing through the IPR slab window may
be delayed due to thermal inertia. In some cases, thermal erosion,
weakening of the upper plate lithosphere and related extensional
deformation could occur some million years after ridge subduction.

\subsubsection{Kuril basin and Okhotsk sea}\label{sec525}

The Kuril basin is located in the easternmost part of the Eurasian
margin, and opened between 30--26~Ma and 15~Ma north of the Kuril arc,
in a triangular domain with one side along the Sakhalin--Hokkaido shear
zone \citep{Baranovetal2002,KimuraTamaki1985,KimuraTamaki1986}. These
mid-Eocene to Early Miocene extensional basins were constrained to open
mainly in a North--South direction
\citep{Fournieretal1994,Schellartetal2003,Vaesetal2019,Woralletal1996}. 
From the Kuril basins and the Okhotsk Sea to the north, we found no
mention that these back-arc basins might have opened in relation to
spreading ridge subduction and subsequent slab-window at depth.
However, some geological records around the Okhotsk Sea testify for
interactions between hot asthenospheric upwelling and the upper plate
(Figure~\ref{fig10}). The first evidence corresponds to the Eocene OIB
to adakite-like signature rocks observed in the region of the Okhotsk
Sea \citep{Emelyanovaetal2020} and also found in the eastern part of
Kamchatka Peninsula, northeastern China and Honshu Island in Japan 
\citep[e.g.][]{EmelyanovaLelikov2016}. For these authors, these
magmatic products are the consequence of the uprising of hot mantle
through a slab-window related to the break-up of the Pacific plate.
From the northeastern China margin to the western margin of Okhotsk
Sea, apatite fission-track analysis suggests important reheating of the
crust during Late Paleocene to Eocene as a consequence of rapid
upwelling of asthenospheric mantle \citep{Pangetal2020}. Mid-ocean
ridge basaltic (MORB) intrusion into forearc sediments
(Figure~\ref{fig10}), high heat flow and regional uplift have been also
recorded from the region surrounding the Russian Far East 
\citep{Kimuraetal2019,WuWu2019}. 

Considering the Pacific plates reconstructions of 
\citet{Mulleretal2008}, the IPR intersected the Kuril trench from 60
to 50~Ma leading to the development of a hypothetic slab-window beneath
the entire \mbox{region} (Figure~\ref{fig10}). Models of 
\citet{Mulleretal2016} and \citet{Wuetal2022a} also include the complex
\mbox{subduction} of the Kula spreading ridge, spatially limited to the
northern Russia region during Cretaceous and Early Cenozoic times.
Therefore, here again, the Late Cretaceous--Eocene tectono-magmatic
evolution of the Asian margin could result from ridge subduction
inducing development of one or several slab-window beneath Russian Far
East. However, as observed in the Japan region, one must point to a
timing offset since the extensional/transtensional events in the
Kuril region are 30~Ma younger than the first impact of the IPR in
the trench. 

Finally, to sum up, we may consider that the NE Asian margin and
Russian Far East back-arc basins developed during Oligocene and Miocene
times, but extensional/transtensional events localizing narrow to wide
rift systems may have initiated earlier during Late
Cretaceous/Paleocene times (Figure~\ref{fig10}). This implies that
back-arc basin openings at the western-northwestern tip of the Pacific
rim were roughly synchronous, suggesting a regional rather than a local
process. The subduction of the long IPR system, sub-parallel to the
trench, and the related opening of a mega-slab window could be a good
candidate for such a regional mechanism. The Late Cretaceous--Eocene
initiation of extension in the upper plate could be the result of the
direct weakening of the lower crust induced by the uprising of hot
materiel through slab window near the trench. Further dynamic uplift
and thermal doming followed by alkaline magmatism as well as opening of
the back-arc basins during the Neogene could represent the effects of a
long-lasting thermal erosion of the regional lithosphere with decreased
mantle wedge viscosity, at a much larger scale. 

\subsubsection{Sunda-Java}\label{sec526}

The Sunda-Java area is part of the Sundaland (including Sumatra,
Borneo, Java and Indonesia), a complex domain located to the southern
tip of the SE Asian margin. Since the Paleozoic period, Sundaland has
been affected by several accretion of terranes from Gondwana and South
China \citep[e.g.][]{Hall2002}. Along the Sunda-Java margin, Jurassic
to Cretaceous subduction complexes including ophiolites and arc-type
magmatism illustrate \mbox{long-lived} subduction processes 
\citep[e.g.][]{ClementsHall2011}. Associated with this magmatism,
compression recorded in the upper plate was the main factor of the
growing up of this Andean-type cordillera until 80~Ma
\citep[][for references]{Whittakeretal2007,Zahirovicetal2014}. This
tectono-magmatic evolution ended close to the Late Cretaceous--Paleogene
boundary with a drastic change from regional compression to initiation
of back-arc opening. 

As shown previously in Section~\ref{sec522}, the entire region was
subjected to Late Cretaceous initiation of active spreading ridge
subduction (Figure~\ref{fig10}). The first one is west-verging and
involves the IPR subduction, the second one is east-verging and
involves the Wharton spreading ridge (Figure~\ref{fig10}). The latter
interaction is well-documented in plate kinematic reconstructions by
\citet{Whittakeretal2007} who infer subduction of the active Wharton
ridge between 70 and 43~Ma. This subduction induced the progressive
NW--SE migration of a slab-window from southeastern tip of Java
and Sumatra (60--45~Ma) to the Central Sumatra (45--30~Ma)
(Figure~\ref{fig10}). 

Sundaland is characterized by the presence of back-arc basins, most of
them having recorded extensional deformation from Early Eocene to Late
Oligocene \citep{Hall2002,Heineetal2004,McCourtetal1996}. In addition,
to the south, the Java Sea experienced extensional deformation from
60 to 45~Ma, inducing the~Makassar back-arc spreading ridge (strait located
between Borneo and central Sulawesi)
\citep{Letouzeyetal1990,McCourtetal1996}. According to
\citet{Whittakeretal2007}, slab-window opening is predicted beneath this
region between 70 to 45~Ma with a stationary position and thermal
weakening of the upper plate. As a result, decreased mantle wedge
viscosity associated with this slab-window exacerbated Palaeogene
extension and active rifting in the Java Sea region, and enabled
Sumatran continental extension to continue at 50--35~Ma
(Figure~\ref{fig10}). According to \citet{SchellartLister2005}, this
event was preceded by a regional uplift during the Late
Cretaceous--Paleogene. Back-arc spreading opening continued during
Middle to Late Cenozoic times in response to advance of the upper plate
and to slab roll-back processes. To the northwest, Sumatra area has
experienced compressional deformation from 15~Ma to present due to the
subduction of high bathymetric reliefs of the inactive Wharton Ridge
\citep{Whittakeretal2007}.

At the scale of Sundaland, analysis of geologic records onland confirms
the Late Cretaceous--Paleogene regional uplift event, without evidence
of compression nor tectonic thickening 
\citep[e.g.][]{ClementsHall2011,HallNichols2002,Morley2016,PubellierMorley2014,Robertsetal2018}.
As shown by AFT thermochronology dating, the region comprised between
Indochina and Java, (i.e. up to 5,600,000~km$^2$) recorded a
long-wavelength uplift of $600 \pm 200$~m, inducing a regional
sedimentary hiatus, ending close to 50~Ma in southern Sumatra-Java to
37~Ma in Central Java \citep[e.g.][]{ClementsHall2011}. 

\section{Conclusion}\label{sec6}

The time-space evolution of subduction cordilleras is attributed to a
diversity of geodynamic processes acting at convergent margins.
Understanding the evolution of overriding plate regime requires
deciphering the interaction of various physical parameters 
\citep[see][]{Heuretetal2011,Lallemandetal2005,Schellart2008,Stern2002}.
Indeed, the cordilleras are sensitive to the subduction polarity and
slab retreat/advance dynamics
\citep{Doglionietal1999,Doglionietal2007}. In the case of slab retreat
episodes, asthenospheric mantle upwelling cause dynamic topography
\citep[e.g.][]{Husson2006}. On the other hand, the switch from
Altiplano-like topography to collapsed orogen is closely related to the
thermo-mechanical state of the overriding plate 
\citep{VanderhaegheDuchene2010,VanderhaegheTeyssier2001,Vanderhaeghe2012,WangCurrie2023} 
and lateral boundary conditions which might alter the tectonic/gravity
force balances \citep[e.g.][]{Vanderhaegheetal2003}. All these
characteristics can draw and include themselves in a global orogenic
cycle of deformation and magmatism 
\citep[e.g.][]{DeCellesetal2009,Wilsonetal2005}. Notwithstanding, in this
review, we are able to identify the process of active spreading
ridge subduction as an important factor controlling the tectonic and
magmatic status of the upper plate at convergent margins. Since the
early days of the Plate Tectonics theory, it has been recognized that
elevated subduction cordilleras develop over young subducting oceanic
lithosphere (Chile type subduction). By contrast, continental regions
experiencing subduction of old oceanic lithosphere are devoid of high
relief cordilleras as examplified by the topography of the Aleutians,
Kuril, Japan and Indonesia areas. In this paper, we show that
in reality, when looking at subduction boundaries in detail, such
correlations between the age of the subducting lithosphere and the
elevation of the continental upper plate suffers from significant
exceptions. This singularity is illustrated by the active margin of
South America where the lowest elevated segments of the Andean
Cordillera are found in Patagonia over very young oceanic lithosphere,
including the active spreading Chile Ridge. 

Based on the Central Patagonia example, we suggest that the
subduction of an active spreading ridge triggers thermal doming
followed by crustal extension and attenuation of a former elevated
cordillera. In addition, plate reconstruction of the Antarctica--South
America connection shows that the subduction of three active spreading
ridges in this region induced the attenuation and disruption of a
former continuous cordillera and led to oceanic spreading in the Scotia
basin during the opening of the Drake Passage. Thus, the concentration
of several subducting ridges in a given region largely increases the
mechanism of thermal erosion of the continental lithosphere of the
upper plate, in turn causing large-scale crustal extension giving place
in some cases to oceanic spreading in a back-arc environment. 

Large amounts of crustal extension leading to exhumation of metamorphic
core complexes are well documented along North America (Basin and
Range, Columbia, Alaska). Processes of lithosphere thermal erosion at a
regional scale accompanying crustal extension ending by back-arc basin
opening are largely distributed in the East Asian region in relation to
the subduction of the Izanagi--Pacific and Wharton ridges during the
Cenozoic.

Our review of active margins worldwide confirms that a variety of
situations of active spreading ridge subduction induces a variety of
slab-window opening, with geometry varying from isolated gate to
mega-pathway. The impact of hot asthenosphere flowing through these
different windows generates thermal erosion of the lithospheric mantle,
heating and weakening of the crust and in turn various patterns of
extensional structures with narrow orthogonal rift (attenuating the
relief), to regional \mbox{back-arc} spreading of the overriding plate
(causing the full decay of former cordilleras). Active spreading ridge
subduction also impacts the tectonic boundary conditions when the ridge
enters the trench. In some cases, plate boundary conditions 
drastically changed during the Cenozoic with free subduction boundaries
related to the development of transcurrent fault systems. Nevertheless,
we are well aware that our model of cordillera attenuation is not
designed for all cases of ridge subductions and still suffers
unexplained situations. Firstly, all active continental margins may
have developed without a growing cordillera. This was the case for the
Andean margin before the Neogene and probably for Sundaland and Japan
in the late Cretaceous where testimonies of a previous elevated
cordillera are not reported. Secondly, attenuation of cordillera
reliefs by extensional tectonics may occur in relation to processes
that do not involve active ridge subduction, such as slab roll-back,
slab break-off, and tectonic erosion of the margin. Thirdly, in some
regions, we evidenced a 10--30~Myr long time span between the first
impact of the ridge at the trench and the initiation of the thermal
erosion driving the weakening of the upper plate lithosphere by
asthenosphere flows through the opened window. This applies to the East
Asian margin where the subduction of the IPR mega-ridge is not followed
immediately by large-scale lithosphere extension. The reasons for such
delays likely relate to the thermo-mechanical properties of the entire
system that need further investigations. Nevertheless, our model of
attenuation and decay of subduction cordilleras might explain some
aspects of the evolution of numerous convergent margins throughout
Earth's history.

\section*{Declaration of interests}
The authors do not work for, advise, own shares in, or receive funds
from any organization that could benefit from this article, and have
declared no affiliations other than their research organizations.

\section*{Acknowledgements}
We are grateful to Michel Faure, editor of this special issue, for his
constant support. We wish to thank Serge Lallemand for fruitful
discussions and suggestions relative to the evolution of the West
Pacific active margins. We thank also Anthony Memin and Louis de Barros
for hepful discussions. Field works in Patagonia were made possible
with~Manuel Suarez and the assistance of Pituso during twenty years
through friendly cooperation. YL thanks Jacques Bourgois for first
introduction into the CTJ issues with field work and sampling in the
Taitao Peninsula. YL and BS benefited of grants from the ECOS
France-Chile-Argentina cooperative research program, from the CNRS-INSU
and from Geosciences Montpellier. YL is indebted to Professor Munoz for
careful attention in the ``La Mutual de Securidad'' establishment at
Santiago de Chile. 

We thank an anonymous reviewer and Olivier Vanderhaege for very
positive and constructive reviews that helped us improving a first
draft of this article. 

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\section*{Supplementary data}
Supporting information for this article is available on the journal's
website under \printDOI\ or from the author. 

\CDRsupplementaryTwotypes{supplementary-material}{\cdrattach{crgeos-250-suppl.pdf}}

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