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Geological Society, London, Special Publications
Extent and significance of the Upper Ordovician felsic
volcanism in the Pyrenees and Mouthoumet massifs, SW
Europe
Josep Maria Casas, Teresa Sánchez-García, Alejandro Díez-Montes, Pilar
Clariana, Aina Margalef, Pablo Valverde-Vaquero, Aratz Beranoaguirre,
Manuel J. Román-Alpiste, Núria Pujol-Solà & J. Javier Álvaro
DOI: https://doi.org/10.1144/SP542-2022-358
To access the most recent version of this article, please click the DOI URL in the line above. When
citing this article please include the above DOI.
Received 20 December 2022
Revised 9 April 2023
Accepted 11 April 2023
© 2023 The Author(s). Published by The Geological Society of London. All rights reserved. For
permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer:
www.geolsoc.org.uk/pub_ethics
Supplementary material at https://doi.org/10.6084/m9.figshare.c.6670226
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Extent and significance of the Upper Ordovician felsic volcanism in the Pyrenees and
Mouthoumet massifs, SW Europe
Josep Maria Casas1*, Teresa Sánchez-García2, Alejandro Díez-Montes3, Pilar Clariana4, Aina Margalef5,
Pablo Valverde-Vaquero2, Aratz Beranoaguirre6, Manuel J. Román-Alpiste7, Núria Pujol-Solà8,9, J.
Javier Álvaro10
1 Departament de Dinàmica de la Terra i de l’Oceà, Universitat de Barcelona, Martí Franquès s/n,
08028 Barcelona, Spain, casas@ub.edu, ORCID: 0000-0001-7760-7028
2 Instituto Geológico y Minero de España (CSIC), Ríos Rosas 23, 28003 Madrid, Spain,
t.sanchez@igme.es, ORCID: 0000-0001-5826-420X, p.valverde@igme.es, ORCID: 0000-0002-
2184-0848
3 Instituto Geológico y Minero de España (CSIC), Plaza de la Constitución 1, 37001 Salamanca, Spain,
al.diez@igme.es, ORCID: 0000-0003-3215-9174
4 Instituto Geológico y Minero de España (CSIC), Campus de Aula Dei, Avda. Montañana, 1005, 50059
Zaragoza, Spain, p.clariana@igme.es, ORCID: 0000-0002-4168-2744
5 Andorra Research + Innovation, Av. Rocafort 21-23, 3ª planta; Sant Julià de Lòria, Andorra,
amargalef@ari.ad, ORCID: 0000-0003-3165-3162
6 Institute of Applied Geosciences (AGW), Karlsruhe Institute of Technology (KIT), Adenauerring 20b,
76131 Karlsruhe, Germany, aratz.beranoaguirre@kit.edu, ORCID: 0000-0002-1137-6498
7 Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, 18100 Armilla,
Granada, Spain. mj.roman@csic.es, ORCID: 0000-0001-5771-6526
8 Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Martí i
Franquès, s/n, 08028, Barcelona, Spain. npujolsola@ub.edu, ORCID: 0000-0001-6378-6811
9 Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Avda.
Fuentenueva, s/n, 18071, Granada, Spain.
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10 Instituto de Geociencias (CSIC-UCM), Dr. Severo Ochoa 7, 28040 Madrid, Spain, jj.alvaro@csic.es,
ORCID: 0000-0001-6294-1998
*Correspondence: casas@ub.edu
Abstract
New geochronological (U–Pb ID‑TIMS), geochemical and isotopic data from Upper Ordovician felsic
volcanic rocks recorded in the Pyrenees and Mouthoumet massifs, SW Europe, suggest that this
volcanic activity is more widely represented than previously accepted, and allows a better
refinement of the age span involved in the Sardic unconformity. This Sandbian volcanism represents
the final pulse of the Sardic tectonothermal event, started with the Floian–Darriwilian emplacement
of voluminous plutonic rocks and the contemporaneous erosion of the uplifted pre‒Upper
Ordovician basement, and followed by the emplacement of a tholeiitic volcanism contemporaneous
with extensional features and the opening of (half-)grabens finally sealed by Hirnantian glaciomarine
deposits. The Sardic-related lithospheric extension may be linked to thermal doming originated by a
superplume activity causing, in turn, an extensive crustal melting responsible for the onset of the
felsic (calc-alkaline-dominated), Floian–Darriwilian intrusive and Sandbian extrusive magmatism
encased along the northern margin of Gondwana.
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The pre–Variscan geodynamic evolution of the northern Gondwana terranes amalgamated now in
SW Europe is marked by two important tectonothermal events: a Cadomian accretional orogeny (~
590‒550 Ma) followed by a Cambrian rift (~ 540‒485 Ma) (Kroner and Stern 2005; Álvaro et al. 2007;
Nance et al. 2010; Sánchez-García et al. 2019). Most tectonic models of the latter invoke a genetic
connection with the Ordovician opening of the Rheic Ocean (e.g., Gutiérrez-Alonso et al. 2007, 2016;
Díez Montes et al. 2010), which led to the drift of some terranes, collectively known as peri-
Gondwanan terranes, including Avalonia, Carolina, Ganderia and Meguma (Murphy et al. 2006; van
Staal et al. 2009, 2012). In the northern Gondwana margin, the Furongian‒Ordovician rift-drift
transition was related to widespread magmatic activity and crustal uplift that led to the onset of
forced regressions, subaerial exposure and denudation processes followed by onlapping geometries,
unconformities and extensional deformation (Álvaro et al. 2018; Sánchez-García et al. 2019). These
events took place diachronously throughout North Gondwana (e.g., Álvaro et al. 2021), from which
two geochronological end-members can be recognized: (i) a Furongian–early Ordovician Toledanian
Phase, recognized in the Iberian Massif, and (ii) a late–Early to early–Late Ordovician Sardic Phase,
reported in the Mouthoumet massif and Montagne Noire (Occitan Domain), the eastern Pyrenees
(Fig. 1), southern Sardinia and several Mediterranean Variscan realms involved in Alpine orogens. Till
now, attention has been mainly devoted to the plutonic products linked to the “Sardic” magmatism,
which in the Pyrenees, Sardinia, the Mouthoumet massif and the Montagne Noire generated the
protoliths of large gneissic bodies that punctuate the Variscan basement of these areas (e.g., Casas
and Murphy 2018; Álvaro et al. 2020). In contrast, little attention has been given to the volcanic
“Sardic” equivalents preceding the widespread development of extensional tholeiitic pulses (Álvaro
et al. 2016).
In this contribution we present new geochronological, geochemical and isotopic data from Upper
Ordovician felsic volcanic rocks found in the Pyrenees and Mouthoumet massifs (Fig. 1). New data
suggest that this volcanism is more widely represented in these areas than previously thought,
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which allows a better refinement of the age span involved in the Upper Ordovician (“Sardic”)
Unconformity. Moreover, they may contribute to discussion of the genetic relationships between
the different “Sardic” events connecting (i) calc-alkaline-dominant magmatism, (ii) uplift -
denudation - stratigraphic unconformities, and (iii) final extensional, normal-fault development
associated with tholeiitic-dominant volcanism, a matter that is still controversial (Álvaro et al. 2016,
2020b; Puddu et al. 2019).
Geological setting
The Pyrenees is an Alpine range bounded to the North by the North-Pyrenean Frontal Thrust (NPFT
in Fig. 1) separating the Alpine Pyrenees from the Variscan Montagne Noire (southern French Massif
Central) and Mouthoumet massifs (Muñoz 1992, 2019) (Fig. 1).
Pyrenees
Variscan basement rocks, ranging in age from Ediacaran to Carboniferous, crop out extensively in the
Pyrenees forming an elongated strip along the backbone of the cordillera (Fig. 1). Three different
tectonostratigraphic units are detailed below, namely the Canigó Massif, the Pallaresa Dome and the
Ribes de Freser Antiformal stack.
The most complete pre‒Variscan succession occurs in the Canigó Massif, where a thick (up to
3000 m?), poorly fossiliferous pre–Upper Ordovician succession can be recognized, subdivided from
bottom to top into the Canaveilles and Jujols groups (Laumonier et al 1996; Padel et al. 2018a),
formely kown as Canaveilles and Jujols Schists Series (Cavet 1957). The lower part, the Canaveilles
Group and lateral equivalents, is Ediacaran to Terreneuvian in age (Padel et al. 2018a), and mainly
composed of metapelite and metagreywacke interbedded with numerous marble, quartzite and
calc-silicate interbeds (Guitard 1970). The group, ca. 1500 m thick, records a Cadomian (~590-550Ma
in SW Europe) magmatic activity (felsic metavolcanic and metabasite, Casas et al. 2015; Padel et al.
2018b; Pujol-Solà et al. 2022), as well as common felsic Ordovician magmatism (Navidad et al. 2018,
among others, see below). Overlying the Canaveilles Group, the relatively monotonous shale-
dominated strata of the Err Formation (Padel et al. 2018a) constitutes the bottom of the Jujols
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Group. The Err Formation is conformably overlain by limestone and marble of the Valcebollère
Formation, of Cambrian Epoch 2 age according to Padel et al. (2018a). Overlying these limestones,
the Serdinya Formation constitutes the upper succession underlying the Sardic Unconformity. The
Serdinya Formation is mainly made up of grey to greenish shales alternating with centimetre to
decimetre-thick sandstone beds and some quartzite beds at the top. Acritarchs recovered from the
uppermost part of this formation have yielded a broad Furongian–Early Ordovician age (Casas and
Palacios 2012), coincident with a maximum depositional age of ca. 475 Ma for the top of this
succession based on the youngest detrital zircon population collected in the southern slope of the
Rabassa Dome (Margalef et al. 2016). Thus, the age of the Jujols Group is bracketed between the
Terreneuvian and the Furongian‒Early Ordovician.
In the Canigó massif, the Upper Ordovician succession forms a broad fining-upward siliciclastic
package (Cavet 1957; Hartevelt 1970), ranging from 100 to 1000 m in thickness, which
unconformably overlies the pre–Sardic succession (Santanach 1972a). Hartevelt (1970) distinguished
five formations, the Rabassa Conglomerate, Cava, Estana, Ansobell and Bar Quartzite formations,
which can be recognized with some variations over a wide area of the central and eastern Pyrenees.
The Rabassa Conglomerate Formation consists of variegated polygenic conglomerates, up to is 100
m thick, with heterometric clasts of vein quartz, quartzite and slate. The overlying Cava Formation, 0
to 850 m thick, consists of sandstones and shales rich in Katian brachiopods and bryozoans
(Hartevelt 1970; Gil-Peña et al. 2004). The Estana Formation, 0–200 m thick, is composed of
limestone and marly limestone with abundant late–Katian brachiopods, bryozoans, echinoderms and
conodonts (Gil-Peña et al. 2004). The top of the carbonate succession is unconformably capped by
the black-grey shales of the Hirnantian Ansobell Formation, 20–320 m thick, subsequently overlain
by the 8–18 m thick Hirnantian Bar Quartzite Formation (Sanz López et al. 2002; Štorch et al. 2019).
These formations are readily recognised in the southern slope of the massif and in the Rabassa
Dome, which constitutes the western edge of the large antiformal structure formed by the Canigó
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Massif. The Andorra-Montlluís granodiorite separates the Rabassa Dome from the rest of the Canigó
Massif (Hartevelt 1970) (Fig. 1).
The Ribes de Freser and Bruguera units are two Alpine structural units involved in the Ribes de
Freser Antiformal stack, separated from the rest of the Canigó Massif by the Ribes-Camprodon
Thrust (Muñoz 1985) (Fig. 2). In contrast to the Upper Ordovician succession cropping out in the
Canigó Massif, both units show Ordovician magmatism dominated by felsic volcanism. The Bruguera
unit exhibits a 300 m-thick unfossiliferous slate-rich succession, attributed to the Cambrian–Lower
Ordovician by Muñoz (1985) (Fig. 2A, B). This succession is overlain by a volcanic complex, described
below. To the north, a north-dipping fault separates this unit from the Ribes de Freser unit, which
exhibits a 200–600 m-thick succession, mainly composed of Upper Ordovician volcanic, subvolcanic
and volcanosedimentary rocks interbedded in Sandbian‒Katian strata and intruded by a subvolcanic
granitic body (see below). Preliminary restoration of the Alpine deformation locates the Ribes de
Freser unit in a pre‒Alpine northernly position, between the Bruguera unit and the Canigó Massif
(Fig. 2C).
The Pallaresa Dome is a large E–W trending antiformal structure that, together with the la
Massana Anticline, comprises a 4000 m thick pre‒Upper Ordovician siliciclastic-dominated
succession (Figs. 1, 3). This succession was subdivided by Laumonier et al. (1996) into three
formations, from bottom to top, the Alós d’Isil, Lleret-Bayau and Alins formations. The Alós d’Isil and
Alins formations are dominated by shale, locally alternating with thin- to medium-grained
sandstone, and are separated by the metasandstone and marble of the Lleret-Bayau Formation.
Despite the lack of geochronological and biostratigraphical controls, Padel et al. (2018a) suggested
that the Pallaresa succession should be correlatable with the Jujols Group, defined in the Canigó
Massif, being the Alós d’Isil, Lleret-Bayau and Alins triad equivalent to the Err, Valcebollère and
Serdinya formations, respectively. The top of the Alins Formation is unconformably overlain by the
Upper Ordovician Rabassa conglomerate Formation (Zandvliet 1960; Zwart 1979) that constitutes
the base of the Upper Ordovician rocks that are correlated with the type succession described by
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Hartevelt (1970) in the Canigó Massif, Eastern Pyrenees. The Massana Anticline shares the same
lithological characteristics and is bounded to the north and south by the Siluro‒Devonian
successions of the Tor-Casamanya and Llavorsí synclines, respectively (Figs. 1, 3).
Mouthoumet massif
The Mouthoumet Massif or inlier, located between the Montagne Noire to the north and the Alpine
North-Pyrenean Frontal thrust to the south (Fig. 1), represents the southernmost prolongation of the
Massif Central (Berger et al. 1997) and belongs to the Variscan Occitan Domain (Pouclet et al. 2017)
(Fig. 1). Four tectonostratigraphic units are distinguished, from east (tectonically top) to west
(bottom), they are named the Serre de Quintillan, Félines-Palairac and Roc de Nitable thrust slices,
and an unnamed parautochthon (Berger et al. 1997) (Fig. 1). The basement consists of Lower
Ordovician green shale and sandstone, dated to Tremadocian–Arenig(?) by acritarchs and grouped in
the Davejean Formation (Berger 1982; Cocchio 1982). The overlying Upper Ordovician
volcanosedimentary succession is bracketed between the Sardic Unconformity and Silurian black
shale (Fig. 4). Four formations are distinguished there, from bottom to top: (i) the Villerouge
volcanosedimentary complex or formation, ca. 50 m thick, which comprises lava flows, ignimbrite
and breccia interbedded with variegated shale and subsidiary sandstone; (ii) the Gascagne
Formation, a largely sandstone unit, ranging in thickness from 5 to 100 m and rich in Katian
brachiopods; (iii) the Montjoi Formation, an alternation of carbonate and marly shale rich in Katian
bryozoans, brachiopods and echinoderms; and (iv) the Marmairane Formation, up to 10 m thick,
mainly composed of green shale with rare dolostone nodules and centimetre-thick sandstone
interbeds, rich in Hirnantian brachiopods, and finally capped by discontinuous diamictite
glaciomarine beds (Touzeau et al. 2012; Álvaro et al. 2016).
The Upper Ordovician Unconformity
In the Pyrenees, the Upper Ordovician Unconformity was first described by Santanach (1972a). After
his work, it was widely accepted that the Upper Ordovician succession unconformably overlies either
the Jujols or Canaveilles groups (García-Sansegundo and Alonso 1989; Den Brok 1989; Kriegsman et
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al. 1989; García-Sansegundo et al. 2004; Casas and Fernández 2007; Puddu et al. 2019). However,
the origin of this unconformity has been the subject of several interpretations as the timing and
nature of deformation in the Cambrian–Ordovician rocks is controversial. Santanach (1972a) in the
southern slope of the Canigó Massif and García-Sansegundo et al. (2004) in the Garona Dome
attributed the Sardic Unconformity to basement tilting, related to a Late Ordovician faulting episode
and subsequent erosion. To the west, in the Lys-Caillaouas Massif, Den Brok (1989) and Kriegsman et
al. (1989) proposed the existence of a pre‒Variscan deformation event. A pre‒Late Ordovician
folding episode has also been suggested as related to the unconformity in the Canigó massif (Casas
2010; Casas et al. 2012). However, the meaning of this deformation episode is unclear because it is
related neither to metamorphism nor cleavage development, but it seems related to uplift,
widespread emersion and considerable erosion before the onset of Upper Ordovician deposition. As
a result, the Upper Ordovician rocks onlap different formations of the pre‒Sardic succession in the
central and eastern Pyrenees, lying near the lower Cambrian Valcebollère limestones in the Ribes de
Freser area. In the central Pyrenees, Clariana et al. (2018) proposed that an extensional pre‒Variscan
deformation affecting only the underlying Cambrian–Ordovician succession was responsible for the
formation of the Upper Ordovician Unconformity, and Puddu et al. (2019) have suggested that pre‒
Upper Ordovician folds can be related to Mid–Late Ordovician upward propagating extensional
faults. Considering a Furongian‒Early Ordovician age (ca. 475 Ma) for the uppermost part of the
Jujols Group, and a Sandbian‒Katian age (ca. 455 Ma) for the base of the Upper Ordovician rocks, a
time gap of about 20 m.y. can be estimated for the Upper Ordovician Unconformity in the Pyrenees.
In the Canigó Massif extensional tectonics developed synchronously with the deposition of the
lower part of the Upper Ordovician succession. In the Cerdanya area, Puddu et al. (2019) described
extensional faults cutting the pre–Sardic succession, the Sardic Unconformity and the lower part of
the post–Sardic succession (Rabassa Conglomerate and Cava formations). These Late Ordovician
synsedimentary extensional faults are subvertical, NNE–SSW-trending and dramatically affect the
thickness of the lower part of the Upper Ordovician succession. In the Ribes de Freser area, Casas
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(2010) proposed that the Bruguera and Ribes units are separated by E–W trending Late Ordovician
extensional faults. In this scenario, some Alpine thrust faults in the Bruguera and Ribes de Freser
units can be interpreted to have reactivated Mid–Late Ordovician normal faults.
In the Mouthoumet Massif, Upper Ordovician–Lower Devonian rocks rest paraconformably or
with angular discordance on an inherited (pre–Sardic) Lower Ordovician palaeorelief formed by the
Davejean Formation. The Middle Ordovician is absent in the Occitan Domain, and the Sardic
Unconformity is directly affected by extensional pulses leading to the onset of (half-)grabens. These
were infilled with volcanic and volcanosedimentary rocks of tholeiitic affinity, also present in the
neighbouring Cabrières slices of the southern Montagne Noire, but not yet described in the
Pyrenees. Sealing of the Sardic palaeorelief was finally achieved during Early Devonian times (Álvaro
et al. 2016; Pouclet et al. 2017).
Ordovician magmatism
Pyrenees
In the Pyrenees, the lowermost succession or Canaveilles Group is cut by voluminous orthogneissic
bodies, about 500 to 3000 m thick, derived from Ordovician intrusives. They are well represented in
the Aston (ca. 467–470 Ma; U-Pb zircon, Denèle et al. 2009; Mezger and Gerdes 2016), Hospitalet
(ca. 472 Ma; U-Pb zircon, Denèle et al. 2009), Canigó (ca. 472–462 Ma; U-Pb zircon, Cocherie et al.
2005; Navidad et al. 2018), Roc de Frausa (ca. 477–476 Ma; U-Pb zircon, Cocherie et al. 2005;
Castiñeiras et al. 2008) and Albera (ca. 470 Ma; U-Pb zircon, Liesa et al. 2011) massifs (Fig. 1).
Equivalent felsic volcanics have been documented in the Albera Massif, where subvolcanic rhyolitic
rocks have yielded similar ages to those of the main gneissic bodies (ca. 474–465 Ma; U-Pb zircon,
Liesa et al. 2011); mafic coeval rocks are clearly subsidiary (Navidad et al. 2018). In the Canigó
Massif, small gneissic bodies with Sandbian–Katian protolithe ages have been also recognized,
indicating that the magmatism persisted until Late Ordovician times yielding another set of
magmatic rocks that constitute the protoliths of the Cadí (ca. 456 Ma; U-Pb zircon, Casas et al. 2010),
Casemí (446 to 452 Ma; U-Pb zircon, Casas et al. 2010), Núria (ca. 457 Ma; U-Pb zircon, Martínez et
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al. 2011) and Canigó G1-type gneiss (ca. 457 Ma; U-Pb zircon, Navidad et al. 2018). The lowermost
part of the pre‒Upper Ordovician succession host metre-scale metadiorite sills related to an Upper
Ordovician protolith (ca. 453 Ma; U-Pb zircon, Casas et al. 2010). In the Bruguera and Ribes de Freser
units, coeval calc-alkaline ignimbrite, andesite and volcaniclastic rocks are interbedded in the Upper
Ordovician succession (Robert and Thiebaut 1976; Ayora 1980; Martí et al. 1986) or unconformably
cover the pre‒Upper Ordovician succession (Martí et al. 2019). Rheomorphic rhyolite ignimbrite of
the Bruguera unit have been recently dated at ca. 459‒460 Ma by Martí et al. (2019) using U-Pb in
zircon. In the Ribes area, a Sandbian granitic body (ca. 458 Ma, U-Pb zircon, Martínez et al. 2011;
460‒461 Ma, U-Pb zircon, Martí et al. 2019) with granophyric textures intruded at the base of the
Upper Ordovician succession. In the La Pallaresa Dome, some metre-scale rhyodacitic to dacitic
subvolcanic sills, Late Ordovician in age (ca. 453 Ma, U-Pb zircon, Clariana et al. 2018), occur
interbedded within the pre-unconformity strata close to the base of the Upper Ordovician
succession.
Mouthoumet and Montagne Noire massifs
In the Axial Zone of the Montagne Noire, voluminous migmatitic orthogneisses derived from
Ordovician metagranites bearing large K-feldspar phenocrysts, were emplaced at about 471 Ma
(Somail orthogneiss; Cocherie et al. 2005), 456 to 450 Ma (Pont de-Larn and Gorges d’Héric gneisses;
Roger et al. 2004) and ca. 455 Ma (Saint Eutrope Gneiss; Pitra et al. 2012). They intruded the
“Schistes X” or St-Pons-Cabardès Group, a poorly constrained stratigraphic succession capped by the
Sériès tuff, dated at about 545 Ma (Lescuyer and Cocherie 1992). The age of migmatization has been
inferred from U–Pb dates on monazite from migmatites and anatectic granites at 333 to 327 Ma
(Charles et al. 2009), which would represent a Variscan crustal melting event.
The giant emplacement of Ordovician granites (now transformed into Variscan orthogneises)
preserved in the Axial Montagne Noire contrasts with the reduced distribution of contemporaneous
volcanic activities recorded in the extensional (half-)grabens exposed in the Cabrières slices of the
southern Montagne Noire (infilled with the Upper Ordovician Roque de Bandies Formation) and the
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Mouthoumet massif (Villerouge Formation). Both units, up to 50 m thick, comprise, from bottom to
top, polymictic breccia deposits overlain by lava flows and volcanogenic breccia interbedded with
tephra, pyroclastic and volcanosedimentary lenses, with local laharic mudflows, some of which are
included in the overlying Glauzy Formation. The mafic lavas forming the basal part of both units
were described by Álvaro et al. (2016), who interpreted them as continental tholeiites partially
affected by crustal contamination. However, the overlying felsic tephra, pyroclastic and
volcanosedimentary lenses are geochemically described and dated below for the first time.
Sample Descriptions
New geochemical data from four Upper Ordovician subvolcanic or volcanic felsic rocks from the
Pyrenees [fC1803 (Pallaresa dome), BN-1 (Massana anticline), CG-20-01 (Bruguera unit) and CG-20-
05 (Ribes de Freser unit)], and two Upper Ordovician samples from the Mouthoumet massif [VLR_1a
and VLR_1b (Villerouge stratotype)] are reported here. We also present isotopic data from samples
CG-20-01, CG-20-05 and VLR_1a and new geochronological data (U–Pb ID–TIMS) from samples BN-1
and VLR_1a. In addition, U‒Pb LA-ICP-MS detrital zircon data were obtained from one sample some
centimetres above the Upper Ordovician Unconformity in the Rabassa dome (MOI-01).
Sample fC1803 (Clariana et al. 2018) is a rhyodacitic to dacitic subvolcanic rock collected in the
Pallaresa dome, forming sills interbedded within the Alins formation, a lateral equivalent of the
upper part of the Jujols Group (Padel et al. 2018a) (Figs 1, 3). This sample was previously dated as
Sandbian (about 453 Ma, U–Pb ID‑TIMS, Clariana et al. 2018) and is located close to the base of the
Upper Ordovician rocks, near the northern boundary of the Tor-Casamanya syncline (Figs. 1, 3, 5).
Sample BN-1 was collected at the eastern edge of the Massana anticline forming sills on top of
the pre‒Upper Ordovician successions (Figs. 1, 3, 5). It is a rhyolite with a porphyritic texture and
shows eutaxitic foliation (Fig. 6A). The quartz phenocrysts have subhedral habit to rounded shapes
and are surrounded by a fine-grained groundmass of quartz, plagioclase and chlorite, with accessory
zircon, apatite, Fe-Ti oxide and sulfides (Fig. 6B‒D). The larger quartz crystals contain deep
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embayments filled by the rhyolitic groundmass (Fig. 6D). All quartz crystals have narrow rims of
chlorite and plagioclase (Fig. 6D).
Sample CG-20-01 was collected from an ignimbrite with rhyolitic to dacitic composition in the
Bruguera area, on top of a 200 m-thick slate succession broadly dated as Cambrian‒Ordovician in
age (Muñoz 1985) (Fig. 2A). Recent U‒Pb data suggest a radiometric age at ca. 459 Ma (LA-ICP-MS;
Martí et al. 2019). Under the microscope (Fig. 7A‒C), eutaxitic textures can be recognized displaying
very fine grain to aphanitic features. Lithic fragments of ash and fragments of quartz phenocrysts are
abundant, some with microcracks and others with corrosion embayments in a very fine to aphanitic
sericitic groundmass. Other lithic fragments, such as recrystallized rhyolitic glasses, are also present.
Cooling edges can be recognized both in fine-grained tuffs fragments and crystals. Zircon and iron
oxides occur as accessory minerals.
Sample CG-20-05 corresponds to a fine-grained subvolcanic granite, known in the literature as
"Ribes Granophyre", and cropping out in Ribes de Freser area. The granophyre is located in the
lower and middle parts of the Upper Ordovician metasedimentary succession (Fig. 2A) and was
firstly considered as a Variscan magmatic body (Fontboté 1949; Santanach 1972b; Robert 1980),
although Ayora (1980) and Muñoz (1985) suggested a Late Ordovician age on the basis of field
relationship. A Late Ordovician (Sandbian) age was later confirmed by Martínez et al. (2011) (about
458 Ma, SHRIMP U‒Pb) and Martí et al. (2019) (about 460‒461 Ma, LA-ICP-MS U‒Pb). It has a
rhyolitic composition and under the microscope presents a subidiomorphic, fine-grained and
granophyric texture (Fig. 7D), with quartz, K-feldspar and mica as main minerals, and plagioclase,
biotite, muscovite, lithic fragments, oxides and zircon as accessory minerals. Sericite, adularia and
epidote are also present as alteration minerals. K-feldspar is the most abundant mineral, which
forms granophyric textures with quartz. Plagioclase crystals are not abundant. Some exhibit albite
twins, but most of them are seritized. Chloritized biotites are common as well as some quite
unaltered muscovites. Lithic fragments correspond to rhyolitic glass.
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Samples VLR_1a and VLR_1b belong to the Villerouge volcanosedimentary complex cropping out
in the Felinés-Paylarac thrust sheet and unconformably covering the Lower Ordovician Davejean
Formation (Figs 4‒5). Metarhyolites and volcanoclastic tuff of rhyolite composition can be
distinguished. Under the microscope (Fig. 7E‒F), textures are fragmental to fine-grained, with
rounded to angular phenocrysts. Lithic fragments appear to be rhyolites, which may or may not be
porphyritic, whereas ash with small feldspar crystals are embedded in a now recrystallized glassy
groundmass. Microcracks and corrosion embayments occur in some quartz crystals.
Sample MOI-01 was collected from the Upper Ordovician Cava sandstone located just above the
Upper Ordovician Unconformity, in the northern limb of the La Rabassa dome (Fig. 3). Hartevelt
(1970) attributed a Katian age for this formation based on the fossil content, whereas the youngest
detrital zircons obtained in the overlying quartzites of the Bar Quartzite Formation yielded a 442 to
443 Ma-age (U-Pb zircon, Margalef et al. 2016).
Details of analytical methods are to be found in the accompanying supplementary publication.
Results
Whole rock geochemistry
All samples are felsic, with geochemical compositions ranging from rhyolite to dacite (Fig. 8A). They
have an Alumina Saturation Index (ASI; Maniar and Piccoli 1989) mostly >1 and normative
corundum, indicating a peraluminous affinity and a calc-alkaline character, except for sample VLR-1b
that has calcic character (Frost et al. 2001). Sample VLR-1a has the lowest SiO2 content, a very high
FeOt content (7.81), and displays high rates of alteration: CCPI = 75 (Large et al. 2001) and AI = 94
(Ishikawa et al. 1976). This could reflect the influence of hydrothermal processes and high sulphide
content.
In Figure 8B the volcanic rocks of Bruguera (CG-20-01), Andorra (BN-1) and Pallaresa (C1803)
exhibit similar characteristics, sharing the geochemical features of the Upper Ordovician augen
gneisses from the Montagne Noire Axial Zone (Occitan Domain) (OG in Álvaro et al. 2020: fig. 5C)
and of the Middle Ordovician augen gneisses from the Canigó massif (G2 and G3 in Álvaro et al.
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2020: fig. 5B). The two Mouthoumet samples (VLR-1a and VLR-1b) show the highest Nb/Y ratio
values, with a slightly more alkaline character than the other samples. Finally, sample CG-20-05
differs in its higher Zr/Ti ratio and lowest values of TiO2 and Zr, mimicking those of the Upper
Ordovician Casemí gneiss of the Canigó massif (Casemí in Álvaro et al. 2020: fig. 5B).
Regarding the immobile, trace and REE elements, all samples display similar patterns. Thus, all
felsic-type rocks display similar chondrite-normalized REE patterns (Fig. 9A), with an important
enrichment in LREE relative to HREE, which should indicate the involvement of crustal material in
their parental magmas. LREEs have a strong fractionation (La/Smn=4.23–2.75), general flattening of
HREE (Gd/Lun=1.69–1.28) and negative Eu anomalies (Eu/Eu*=0.68–0.08). Sample CG-20-05 (a
subvolcanic granite) comprises the most pronounced Eu anomaly (Eu/Eu*=0.08), similar to that of
the Lower Ordovician leucogneiss from the Iberian Massif and the Upper Ordovician G-1 gneiss from
the Canigó massif (Álvaro et al. 2020: fig. 7).
These felsic rocks exhibit a relatively narrow range of values with pronounced P and Ti negative
anomalies in the normalized multi-element diagram (Fig. 9B), suggesting significant fractionation of
apatite, ilmenite and magnetite. The anomalies shown by Ba and Sr correspond to feldspar
fractionation. The negative anomalies of Nb and Ta suggest a volcanic-arc setting, and the negative
Ti and Nb anomalies are very similar to those exhibit by the Canigó G-1 type gneiss and the
leucogneiss of the Iberian Massif (Álvaro et al. 2020: fig. 8). It should be noted that the depicted
pattern is very similar to that of the Ordovician rocks of the Occitan Domain, Sardinia, Iberian Massif
and Pyrenees (Álvaro et al. 2020: fig. 8).
In the Upper Continental Crust normalized multi-element patterns (Fig. 9C), all samples display
similar flat patterns, with a relationship close to unity, but slightly rich in almost all elements, and
with slightly higher values in the HREE. There is only a slight negative anomaly in Sr. Sample CG-20-
05 has very pronounced negative anomalies in Ba and Ti, probably related to more marked
differentiation evolution processes than the remaining samples.
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Concerning the tectonic discrimination diagrams, e.g. Pearce et al. (1984) (Fig. 10A‒B), the
relatively high contents in Y and Yb plot these samples on the boundary with the Within-Plate
Granite (WPG) field. Figure 10C shows that the study rocks define a high Th trend. In the normalized
incompatible element diagram (Fig. 10D), they exhibit enriched patterns with pronounced Th
positive anomalies, similar or slightly larger than those of the Upper Continental Crust. These facts
suggest that the high Th content of the felsic rocks have a close genetic link with magmatic
processes in the continental crust (Yang and Scott 2003).
Sm‒Nd isotopic analysis
New isotopic values documented here correspond to the samples CG-20-01, CG-20-05 and VLR_1b.
εNd values range from –3.3 (CG-20-01), ‒2.9 (VLR_1b ) to –1.2 (CG-20-05). TDM values vary between
1.21 Ga (Mouthoumet) to 1.37 Ga (Bruguera area) and 1.44 Ga (Ribes de Freser) (Fig. 12). The
differences in the TDM ages could indicate that the magmas that gave rise to the Upper Ordovician
volcanic rocks had different residence times in the crust. All are compatible with magmas derived
from young crustal rocks, with felsic compositions.
U‒Pb Geochronology (CA ID-TIMS)
Samples BN-1 and VLR_1a contain elongated zircon prisms with length/width ratios of 1:5 to 1:7,
which were selected for analysis corresponding to the P1-P4 prismatic zircon of Pupin (1980).
Multigrain fractions were used to date these volcanic levels because, if concordant, they provide an
accurate estimate of the volcanic zircon population.
VLR_1a (455 ± 1 Ma): five multigrain zircon fractions, ranging from two to twenty zircon prims,
were analyzed (Fig.12A). Four fractions define a Discordia line (line Z1-Z2-Z3-Z4) with an upper
intercept age of 455±4 Ma (MSWD 0.118). The two concordant fractions Z1 and Z2 that anchor the
upper intercept also provide a Concordia age of 454.65 ± 0.65 Ma (MSWD 0.06) (Fig. 12A). Given the
low MSWD to avoid error underestimation, it is preferred to round the age and quote 455 ± 1 Ma as
the most accurate estimate for the age of extrusion of this rock.
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BN-1 (457±1.5 Ma): five, multigrain, zircon fractions made of 6 to 11 crystals were analyzed.
Fraction Z5 is concordant at 457 Ma (Fig. 12B). The other fractions are discordant due to the
presence of older, inherited zircon. The mixing lines of 457 Ma zircon with these fractions (not
plotted; Fig. 12B) provide ages ranging from 0.72 Ga (Z1) to 2.3 Ga (Z4); given the long projection of
the intercepts the presence of Neoproterozoic and Paleoproterozoic inherited zircon can only be
inferred. The Concordia age of fraction Z5 is 457 ± 1.4 Ma. Even though this is only one analysis, and
hence its MSWD is low, the fact that this concordant fraction is made of 11 crystals makes the result
reliable. Therefore, an age of 457 ± 1.4 Ma is considered an accurate estimate for the age of
extrusion.
U‒Pb Geochronology (LA-ICP-MS)
MOI-01: Fifty-seven grain measurements are plotted in Figure 13. They give a wide range of
concordant ages between 2662 and 443 Ma (degree of concordance between 90 and 110%), with a
prominent age cluster at ca. 600‒700 Ma, and minor clusters at 450 Ma (Katian), 900 Ma (Tonian),
1000‒1050 Ma (Stenian), 1800‒2000 Ma (Orosirian) and 2600 (Neoarchean). The youngest zircon
grains yielded a Concordia age of 452.0 ± 6.5 Ma (MSWD=2.1, n=4), which allows us to propose a
maximum sedimentation age for the basal part of the Cava Formation around 452 Ma (Katian). The
youngest zircon crystals show euhedral shapes, whereas older grains are commonly rounded. The
high Th/U ratios of most of the analysed grains, significantly > 0.1, suggest a magmatic origin. The
obtained zircon population matches with the distribution of detrital zircon ages exhibit by the
samples RB-10-01, RB-10-02 and RB-10-03 of the underlying Cambrian‒Ordovician Serdinya
quartzites (Margalef et al. 2016) and with the population of sample RB-10-04 from the overlying
Hirnantian Bar Quartzite Formation (Margalef et al. 2016) (Fig. 14).
Comparison with the Ordovician magmatism in NE Iberia, Montagne Noire and Sardinia
The time span of the Upper Ordovician volcanism in the Pyrenees is bracketed between 459 to 453
Ma (Sandbian) and is contemporaneous with the emplacement of the protoliths of the Late
Ordovician gneisses in the Canigó massif (G-1 and Cadí gneiss: ca. 457‒456 Ma; Casas et al. 2010;
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Martínez et al. 2011; Navidad et al. 2018). Although, in the latter massif, the magmatic activity
started earlier, at Darriwilian times (ca. 464‒462 Ma, G-2 and G-3 type gneiss, Navidad et al. 2018),
and persisted until the Katian (ca. 456‒446 Ma, Casemi gneiss, Casas et al. 2010 (Fig. 15). The
studied metavolcanic rocks exhibit geochemical and isotopic signatures similar to those of the
Darriwilian and Upper Ordovician (Sandbian and Katian) Canigó gneiss (εNd from –3.5 to ‒4.7 and
TDM from 1.39 to 1.5 Ga; Navidad et al. 2010; Martínez et al. 2011), and the Upper Ordovician
metavolcanic samples from the Gavarres and Guilleries massifs in the neighbouring Catalan Coastal
Range (εNd from –4.6 to ‒5.2 and TDM from 1.39 to 1.7 Ga; Navidad et al. 2010; Martínez et al.
2011). The age of the sample of the Mouthoumet massif (ca. 455 Ma) indicates that it is
pecontemporaneous with the emplacement of the protoliths of the orthogneisses form the
Montagne Noire Axial Zone (ca. 456‒451 Ma; Roger et al. 2002; Pitra et al. 2012) (Fig. 15). The
metavolcanites from the Pyrenees and Mouthoumet were also contemporaneous to the
metavolcanic rocks of the Catalan Coastal Range (ca. 455‒452 Ma; Navidad et al. 2010; Martínez et
al. 2011). Thus, although the time span of Ordovician magmatism was longer in the Pyrenees, from
Darriwilian to Katian times, the studied samples can be considered as the volcanic and subvolcanic
equivalents of the plutonic protoliths that led to the Upper Ordovician gneisses from the Pyrenees
and the Montagne Noire (Occitan Domain) (Fig. 15). It should be noted that in the studied areas, no
Middle Ordovician volcanic rocks have been described.
In addition to the Pallaresa Dome, the Massana Anticline and the Canigó Massif from the
Pyrenees and the Mouthoumet Massif, this volcanism was probably widespread in other western
Pyrenean massifs, such as the Pierrefitte Dome (Calvet et al. 1988). However, geochronological data
are needed to confirm the Ordovician age attributed to the rhyolitic sills of this massif. It should be
noted that the Upper Ordovician volcanism of the Canigó Massif has been recognized only in the
southernmost Ribes de Freser and Bruguera units, whereas, as stated above, equivalent upper
Lower and Upper Ordovician plutonic rocks predominate in the remaining units. The volcanism was
seemingly controlled by the development of local structures, such as irregularly distributed
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extensional faults, which were active at different episodes from Mid-Ordovician to Sandbian‒Katian
times (Puddu et al. 2019).
In Sardinia, a Ordovician felsic volcanism is present in the southernmost Bithia unit (Pavanetto et
al. 2012; Cruciani et al. 2018), in the External Nappe Zone of the island, where it is especially well
represented (Garbarino et al. 2005; Giacomini et al. 2006; Oggiano et al. 2010; Cruciani et al. 2012,
2013), and in the northern Internal Nappe Zone (Helbing and Tiepolo 2005; Giacomini et al. 2006;
Oggiano et al. 2010). However, these areas show differences. First, the felsic volcanism started
earlier and is not restricted to the Sandbian‒Katian: it ranged from the Darriwilian to the Katian in
the Bithia unit (Pavanetto et al. 2012; Cruciani et al. 2018) and from Furongian to the Katian in the
External Nappe Zones (Oggiano et al. 2010; Cruciani et al. 2013), whereas in the Internal Nappe Zone
it is mainly Tremadocian in age (Oggiano et al. 2010). Secondly, Ordovician felsic plutonic rocks are
subsidiary, being Katian in age in the Bithia unit (Ludwig and Turi 1989) and ranging from the Floian
to the Katian in the Internal Nappe Zones (Helbing and Tiepolo 2005; Giacomini et al. 2006).
However, Ávaro et al. (2020) pointed out that despite some small differences in the chemical ranges
of some major elements, most felsic Ordovician rocks from the Eastern Pyrenees, the Mouthoumet
and Montagne Noire (Occitan Domain) and Sardinia are similar in their geochemical patterns. In the
Iglesiente area, where the Sardic Unconformity is well expressed, no Ordovician magmatic rocks
have been described until now. This, together with some differences in their sedimentological and
fossil record, led Coco et al. (2022) to propose a different palaeogeographic location for this unit in
relation to the External Nappe Zone units. According to these authors, both units were subsequently
amalgamated during the Variscan Orogeny. However, the irregular distribution of the Upper
Ordovician volcanic rocks in the areas, the different depths of erosive related to the Sardic Phase,
the different ages of the strata sealing the inherited palaeorelief, and the biogeographic affinities of
different sub-units in Sardinia (characters also shared by different nappes and slices of the northern,
Axial and southern Montagne Noire), do not seem strong arguments to attribute different initial
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paleogeographic positions (fringing vs. far from Gondwana) for different structural units of southern
Sardinia.
The age zircon signature of the studied detrital rocks
As previously noticed by Margalef et al. (2016), and supported by this work, the detrital zircon
populations below and above the Sardic Unconformity in the Rabassa dome, where the time gap is
minimal, are almost equivalent. The only exception can be related to the scarcity of Upper
Ordovician zircon populations yielded by the Cava Formation (sample MOI-01) above the
unconformity (Fig. 14). This similarity in the zircon spectrum below and above the unconformity,
points to no changes in the source area influencing the successions below and above the Sardic
Unconformity. However, this can be alternatively explained by the origin of the Upper Ordovician
siliciclastic rocks, necessarily influenced by the denudation of the directly underlying Serdinya
Formation, and deposited in the accommodation space yielded by the hangingwall of the
extensional faults. The euhedral shape of the younger zircons is in accordance with a local origin for
the Upper Ordovician sedimentary rocks. The minor contribution from coeval Upper Ordovician
magmatic rocks could be due to the localized extent of the volcanic rocks and/or the plutonic rocks
emplaced at depths not reached by the Sardic erosion.
Moreover, the U‒Pb age patterns of the detrital zircon populations in the samples below and
above the Sardic Unconformity are similar to those yielded by Ordovician samples from the Iberian
Massif, characterized by a wide spectrum of Ediacaran and Cryogenian peaks and a variable,
although always present, Mesoproterozoic (Stenian) population (Chichorro et al. 2022). This
distribution reinforces their proposed Trans Sahara Belt influence, between the Saharan Metacraton
and the Arabian-Nubian Shield (Hart et al. 2016; Margalef et al. 2016; Casas and Murphy 2018; Padel
et al. 2017, 2022).
The Upper Ordovician Unconformity
The aforementioned volcanism is coeval with the deposition of Sandbian‒Katian alluvial to fluvial
sediments. Obtained data from the detrital zircon population of sample MOI-01 allows us to propose
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a maximum sedimentation age for the basal part of the Cava Formation around 452 Ma (Katian).
This age is coincident with regional data (Hartevelt 1970; Gil-Peña et al. 2004). Considering an age of
ca. 475 Ma for the underlying quartzites of the Serdinya Formation (Margalef et al. 2016), an age gap
of ca 23 m.y. can be attributed to the Sardic Unconformity in the Canigó Massif. Similar gaps are
found in the Sulcis-Iglesiente area of SW Sardinia (ca. 17 m.y., Cocco et al. 2022), the type area
where the Sardic Unconformity was originaly defined. There the unconformity separates the
Cambrian–Ordovician from the Upper Ordovician successions, marking a stratigraphic gap that
includes part of the Floian (Pillola et al. 2008), the entire Dapingian and Darriwilian, and part of the
Sandbian (Hammann 1992; Leone et al. 2002).
In the eastern Pyrenees, the time gap of the Sardic Unconformity increases from west to east,
from the Rabassa Dome (23 m.y.) to the Ribes de Freser area, where the Upper Ordovician rocks are
unconformably overlying Cambrian Series 2 Valcebollère Formation (Muñoz et al. 1994; Vergés et al.
1994), implying that a thickness of ca. 1500 m of Cambrian‒Ordovician rocks would have been
eroded prior to the sealing by Upper Ordovician rocks in this area. In the Bruguera unit, the
stratigraphic gap between Upper Ordovician volcanics (sample CG-20-01) and the underlying
succession cannot be evaluated.
The variation in the time gap involved in the Sardic Unconformity, and the absence of preserved
Middle Ordovician sedimentary rocks, suggest that two factors may have contributed to the pre‒
Upper Ordovician basement erosion. A first, generalized, Mid Ordovician uplift would have been
responsible of subaerial conditions, erosion and the non-deposition of Middle Ordovician rocks,
together with the activity of coeval N‒S oriented subvertical west-dipping extensional faults. These
faults may control the progressive uplift and subsequent erosion of the rocks located on their
footwalls and, as a result, erosion increases eastward reaching its maximum in the Ribes de Freser
transect. A similar situation is described in the Sulcis-Iglesiente area of SW of Sardinia by Cocco et al.
(2022), where an incision of about 1200 m resulting in the onlapping of lower Cambrian rocks by
Upper Ordovician strata.
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Tectonic setting of Ordovician volcanism
The tectonic setting of Ordovician rocks along the northwestern margin of Gondwana is still a matter
of debate. Two end-member models have been proposed to explain the Ordovician
tectonomagmatic events in NW Gondwana: a subduction-related orogenesis (e.g., Zurbriggen et al.
1997; Castro et al. 2009; Oggiano et al. 2010; Rubio-Ordóñez et al. 2012; Zurbriggen 2015; Villaseca
et al. 2016; Cruciani et al. 2018; Cocco et al. 2022) vs. a lithospheric extension (e.g., Calvet et
al.1988; Marini 1988; Bea et al. 2007; Montero et al. 2009; Díez Montes et al. 2010; Navidad et al.
2018; Puddu et al. 2019; Álvaro et al. 2020; Pereira et al. 2022). Lithospheric extension can be
related to either hot spot activity (Marini 1988), mafic underplating or intrusion (Bea et al. 2007;
Díez Montes et al. 2010; Puddu et al. 2019; Álvaro et al. 2020b) or asthenospheric upwelling
(Navidad et al. 2018; Pereira et al. 2022). We interpret the Sandbian volcanism reported in the
Pyrenees and Mouthoumet massifs as representing the final pulse of an Ordovician tectonothermal
event, which started in these areas with the Floian–Darriwilian emplacement of plutonic rocks,
lithospheric uplift and extensional fault movement leading to the partial erosion of the pre‒Upper
Ordovician palaeorelief. This scenario, associated with a Sandbian volcanic activity
contemporaneous with the infill of Sandbian‒Katian half-grabens by alluvial and fluvial sediments,
fits better with a global extensional setting and argues against any subduction model. Lithospheric
extension may be linked to thermal doming originated by a superplume activity causing, in turn,
extensive crustal melting, as proposed previously in this area (Puddu et al. 2019; Álvaro et al. 2020).
This Ordovician igneous event in the Pyrenees and Mouthoumet Massif, together with Cambrian and
Ordovician magmatic activity in other areas of the Variscan belt (Iberian Massif, Armorican Massif,
Montagne Noire, Sardinia, Saxo–Thuringian Zone), may define a large igneous province (LIP),
heralding continental breakup and terrane dispersion along the NW Gondwanan margin during the
Furongian–Early Ordovician (Díez Montes et al. 2010; Sanchez-Garcia et al. 2019). A similar situation
has been described in NE of Gondwana margin, where asthenospheric upwelling linked to mantle
plume emplacement in an intraplate setting has been proposed to explain a noticeable Cambrian‒
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Ordovician magmatic activity (Dan et al. 2022). As in the study case, this magmatic activity can give
rise to a silicic large igneous province (LIP), which is referred to here as the Pinghe silicic LIP (Dan et
al. 2022).
Conclusions
This work focuses on the geochemical features and radiometric ages yielded by the felsic Upper
Ordovician volcanic rocks from different tectonostratigraphic units of the Pyrenees and
Mouthoumet (Occitan Domain) massifs. This calc-alkaline volcanism is bracketed between 459 to
453 Ma (Sandbian) in both massifs, and can be considered as the volcanic and subvolcanic
equivalents of the voluminous plutonic protoliths that led to the Upper Ordovician gneisses that
punctuate the Axial Pyrenees and the Axial Montagne Noire of the Occitan Domain. The Sandbian
volcanism represents the final pulse of an Ordovician tectonothermal event, which started with the
Floian–Darriwilian emplacement of plutonic rocks, lithospheric uplift and extensional fault
movement leading to the partial erosion of the pre‒Upper Ordovician palaeorelief. This scenario,
associated with the infill of Sandbian‒Katian half-grabens by alluvial and fluvial sediments, suggest a
global extensional setting. Lithospheric extension may be linked to thermal doming originated by a
superplume activity causing, in turn, an extensive crustal melting responsible for the Ordovician
magmatism widely represented in this sector of Gondwana margin.
Acknowledgements
JMC acknowledges the hospitality of the Earth Science Department of the Saint Francis Xavier
University (Antigonish, NS, Canada) during a 2022-2023 one-year sabbatical. We gratefully
acknowledge constructive reviews by T. Pharaoh and an anonymous referee as well as careful
editorial handling by R. Strachan. With this contribution to the special issue, the authors would like
to celebrate the career of J.B. Murphy, and its legacy not only as a great professional he is, but also
as a person.
Author contributions
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JMC Conceptualization (lead), investigation (lead), methodology (lead), supervision (lead), validation
(lead), writing – original draft (lead))TSG Writing – original draft (equal), writing – review & editing
(equal), sampling ADM Writing – original draft (equal), writing – review & editing (equal), sampling
PC Writing, original draft (equal), writing – review & editing (equal), sampling AM Writing – original
draft (equal), writing – review & editing (equal), sampling AB Writing – original draft (equal), writing
– review & editing (equal), dating MJRA Writing – original draft (equal), writing – review & editing
(equal), dating NOPS Writing – original draft (equal), writing – review & editing (equal) J.J.Á Formal
analysis (equal), funding acquisition (lead), investigation (equal), methodology (equal), supervision
(equal), validation (equal), writing – review & editing (equal)
Funding
This work is a contribution to PID2021-122467NB-C22 and PID2021-125585NB-I00 projects from the
Ministerio de Ciencia, Innovación y Universidades/Agencia Estatal de Investigación/Fondo Europeo
de Desarrollo Regional (FEDER), EU. JMC acknowledges the financial support of the Dpt. de Dinàmica
de la Tera i de l’Oceà (Universitat de Barcelona).
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Figure Captions
Fig. 1. A. Geologic sketch of the Eastern Pyrenees and Mouthoumet massifs with location of the
figures 2, 3 and 4. B. Pre-Variscan reconstruction of the Variscan tectonostratigraphic units reported
in this work, based on Pouclet et al. (2017) and Álvaro et al. (2020). Abbreviations: CIZ – Central
Iberian Zone, CZ – Cantabrian Zone, GAPL – Grimaud–Asinara–Posada Line, GTMZ – Galicia–Trás-os-
Montes Zone, ME –Maures-Estérel Massif, Mo – Mouthoumet Massif, OD – Occitan Domain, OMZ –
Ossa-Morena Zone, Pyr- Pyrenees, PTFSZ –Porto–Tomar–Ferreira do Alentejo Shear Zone, SAD-South
Armorican Domain, SASZs – South Armorican Shear Zone southern branch, SHF – Sillon Houiller
Fault, SISZ – South-Iberian Shear Zone, WALZ – West Asturian–Leonese Zone.
Fig. 2. A. Geological map of the Bruguera and Ribes de Freser area showing the location of samples
CG-20-01 (Bruguera unit) and CG-20-05 (Ribes de Freser unit). B. Balanced cross-section of the Ribes
de Freser antiformal stack (B unit=Bruguera unit; RF unit=Ribes de Freser unit; RC thrust=Ribes
Camprodopn thrust). C. Restored section of the Ribes de Freser antiformal stack showing the initial
location of the Bruguera and Ribes de Freser units and the Canigó massif.
Fig. 3. Geological map showing the location of the samples fC1803 (Pallaresa massif), BN-1 (Massana
anticline) and MOI-01 (Rabassa dome). Modified after Clariana et al. (2018).
Fig. 4. Geological map of the Mouthoumet massif showing the location of samples VLR_1a and
VLR_1b. Modified after Berger (1982), Bessière and Schulze (1984) and Bessière and Baudelot
(1988).
Fig. 5. Stratigraphic sketches showing the position of the studied samples. Geochronological data
after (1) Clariana et al. (2018), (2) Margalef et al. (2016), (3) Martí et al. (2019), (4) Martínez et al.
(2011) and (5) this study.
Fig. 6. Sample BN-1. A. Thin-section of BN-1 sample with a porphyritic texture. B. Rounded-shaped
quartz crystal surrounded by a narrow rim of chlorite and plagioclase crystals. C‒D. Rounded-shaped
larger quartz phenocrysts with deep embayment filled by rhyolitic groundmass. Abbreviations: Qz,
quartz; Ser, sericite; Lth, lithic fragment.
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Fig. 7. A‒C. Sample CG-20-01, Bruguera area. Rhyolitic ignimbrite. A. recrystallized glass in a sericitic
groundmass. B. Lithic fragment of rhyolitic composition, with a zircon crystal, embedded on a
sericitic groundmass. C. Phenocrystal of shattered quartz with a reaction margin (RM), embedded in
a seriticic-rich groundmass bearing sparse opaques. D. Sample CG-20-05, subvolcanic granite, fine-
grained, with sub-idiomorphic and granophyric textures. Secondary deformation features include
subgrain boundaries, chloritization of biotite and seritization of some minerals. E. Sample VLR_1a,
Mouthoumet area. Volcanic tuff with abundant lithic fragments rich in rhyolitic rocks and shale. F.
Volcanic tuff (sample VLR_1b), with a large fragment of porphyritic rhyolite, with plagioclase
phenocrysts on a vitreous groundmass, now recrystallized. Abbreviations: V, recrystallized glass; Ser,
sericite; Zrn, zircon; Lth Rhy, Lithic Rhyolite; L, Lithic fragment; Qz, quartz; Pl, plagioclase; Kfs,
potassium feldspar; Ms, muscovite.
Fig. 8. Classification diagrams for Upper Ordovician felsic rocks. A. SiO2 vs. Zr/TiO2 diagram
(Winchester and Floyd 1977). B. Zr/Ti vs. Nb/Y diagram from Pearce (1996).
Fig. 9. A. Chondrite-normalized REE patterns (Sun and McDonough 1989). Grey area defined to
Occitan Domain of the Pyrenees from Álvaro et al. (2020). B) Multi-element diagram normalized to
the Primitive Mantle (Sun and McDonough 1989). C. Multi-element diagram normalized to the
Upper Continental Crust (Rudnick and Gao 2003).
Fig. 10. A‒B. Tectonic discrimination diagrams from Pearce et al. (1984). C. Yb-Th-Hf ternary diagram
from Yang and Scott (2003). D. Chondrite-normalized incompatible element patterns for the Upper
Ordovician felsic rocks from Pyrenees (UCC: Upper Continental Crust from Rudnick and Gao 2003;
chondrite from Sun and McDonough 1989).
Fig. 11. εNd (t) vs. age diagram (DePaolo and Wasserburg 1976; DePaolo, 1981, 1988) for studied
rocks. Shadow area corresponds to Upper Ordovician volcanic rocks of Álvaro et al. (2020).
Fig. 12. U–Pb concordia diagram for the samples: a) VLR_1a and b) BN-1.
Fig. 13. U–Pb concordia diagram for the sample MOI-01.
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Fig. 14. Kernel Density Estimates (KDE) plots, showing the peak ages, for the analyzed sample (MOI-
01) in the top, compared with previous data of zircon grain analyses from the Jujols group and the
Bar Quartzite (Margalef et al. 2016). Abbreviations: Bw= Band width, n= number of samples. Figure
constructed using the HistogramsApp (Rodríguez-Corcho et al. 2020; Rodríguez-Corcho and action
users, 2021).
Fig. 15. Summary diagram of the U-Pb geochronological data (with error bars) of the two study
volcanic samples together with Ordovician ages ot the Pyrenees, Mouthoumet massif, Montagne
Noire and Catalan Coastal Range. References for the data are: 1: Denèle et al. (2009); 2: Mezger and
Gerdes (2016); 3: Cocherie et al. (2005); 4: Martínez et al. (2011); 5: Casas et al. (2010); 6: Navidad et
al. (2018); 7: Martí et al. (2019); 8: Castiñeiras et al. (2008); 9: Liesa et al. (2011); 10: Liesa
unpublish.;11. Clariana et al. (2018); 12: Roger et al. (2004); 13: Pitra et al. (2012); 14: Navidad et al.
(2010); 15: This work.
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Table Captions
Table 1. Whole rock major and trace element data of the studied samples.
Table 2. Sr–Nd isotopic data of samples CG-20-01, CG-20-05 and VLR_1b.
Table 3. CA ID TIMS U/Pb data table of samples VLR_1a and BN-1.
Table 4. LA-ICP-MS U/Pb data table of sample MOI-01.
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SAMPLE
VLR_1a
VLR_1b
BN 1
CG-20-05
CG-20-01
fC1803
Massif
Mouthoumet
Mouthoumet
Andorra
Ribes de
Freser
Bruguera
Pallaresa
SiO2
66,12
77,20
69,18
75,21
70,67
71,67
TiO2
0,78
0,76
0,61
0,09
0,42
0,63
Al2O3
14,73
12,36
15,05
12,28
13,51
14,24
Fe2O3
2,46
0,45
1,56
0,56
0,53
1,52
FeO
5,59
0,94
2,38
0,69
0,97
2,72
MnO
0,02
0,01
0,05
0,03
0,01
0,06
MgO
1,03
0,34
1,16
0,13
0,42
0,78
CaO
0,14
0,11
1,78
1,13
0,04
0,53
Na2O
0,09
0,15
3,40
2,81
0,03
1,67
K2O
2,87
2,80
2,71
4,91
4,51
2,91
P2O5
0,06
0,06
0,20
0,02
0,09
0,24
LOI
5,30
4,60
1,50
2
2,7
2,60
TOTAL
99,79
99,87
99,42
99,81
93,85
99,42
Sc
12
9
10
3
12
10
V
92
74
36
8
26
49
Cr
-
-
0,001
13,684
13,684
0,003
Co
12,5
3,9
6,
2
0,8
2,5
4,6
Ni
22
20
7,
7
0,4
0,4
8
Cu
5
8,2
10,3
0,6
3,1
13,2
Zn
106
14
70
17
14
52
Ga
21
11,7
18,8
19,2
23
19,8
As
0,8
0,5
6,
8
2,8
0,5
1,7
Rb
96,5
75,7
137,2
217,2
213,4
123,7
Sr
135,8
107,9
83,7
38,2
33,9
201,8
Y
32,4
31,4
50,6
52,2
39,5
43,9
Zr
246,3
217,4
237,1
124,2
225,1
263,2
Nb
18,2
17,4
11,3
12,9
13,1
11,3
Mo
0,1
0,1
1
0,8
0,1
0,9
Ag
0,1
0,1
0,
1
0,1
0,1
0,1
Sn
4
2
5
9
6
5
Sb
0,3
0,2
0,
3
1,2
1,2
0,1
Cs
9,4
5,8
4,
9
3,9
7,2
5,6
Ta
1,1
1,2
1,
1
1,5
1,1
1,1
Ba
778
381
39
8
99
763
388
Hf
6,5
5,6
6,
4
5,3
6,5
7,3
W
1,2
1,4
2,
5
2,3
1,6
1,9
Tl
0,1
0,1
0,
1
0,1
0,1
0,6
Pb
3
1,5
22
,9
8,6
1,4
9,8
Th
12
11,4
13,5
25,8
18,4
15,7
U
3,5
3,6
4,
6
7,6
3,3
5,1
Be
1
1
2
2
5
3
La
51,5
38,8
38
34,1
50,9
45,3
Ce
104,2
77,8
75,5
71,4
103,8
86,9
Pr
11,54
8,7
8,
8,74
12,59
9,8
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47
Nd
45,1
32,5
31,2
32,6
47,3
35,6
Sm
7,66
6,05
7,16
7,81
9,58
7,69
Eu
1,52
1,16
1,03
0,2
0,83
1,05
Gd
6,11
6,2
7,89
8,49
7,91
8,32
Tb
1,04
1,11
1,27
1,55
1,26
1,26
Dy
5,58
5,54
8
9,47
7,11
6,68
Ho
1,22
1,21
1,73
1,98
1,5
1,52
Er
3,32
3,52
4,96
5,69
4,27
4,52
Tm
0,57
0,55
0,
73
0,79
0,61
0,6
Yb
3,86
3,51
4,72
4,94
4
3,98
Lu
0,6
0,55
0,69
0,76
0,6
0,58
Table 1
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ROCK UNIT
SAMPLE
LOCATION
AGE
GEOGRAPHICAL
COORDINATES
Sm
Nd
147Sm/144
Nd
143Nd/144Nd
eNd
(age)
TDM
Bruguera
CG-20-01
Bruguera
458
42º17’05.09’’N
2º11’18.98’’E
6,73
31,99
0,1265
0,512260
-3,3
1,37
Ribes de
Freser
CG-20-05
Ribes de
Freser
458
42º19’04.87’’
2º10’03.13’’E
6,28
25,26
0,1497
0,512433
-1,2
1,44
Mouthoumet
VLR_1b
Marmairane
creek
455
43º00’14.13’’N
2º40’07.28’’E
6,05
32,5
0,1120
0,512238
-2,9
1,21
Table 2
ACCEPTED MANUSCRIPT
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Concentration
Isotopic rations
Isotopic ages (Ma)
Weight
U
Pb
Pb
206
Pb*
208
Pb
206 Pb
207 Pb
corr.
207 Pb
206 Pb
207 Pb
207 P
Fractions
(mg)
(ppm)
(ppm)
(pg)
204 Pb
206
Pb
238 U
% err
235 U
% err
coef.
206 Pb
% err
238 U
235 U
206 Pb
Sample
Villerouge
Z1 (L2) 2
xtls, 120
µm
0.0017
1574
119
11.
0
1134.1
0.0
822
0.0730
5
0.13
0.5650
0.30
0.52
0.05609
0.25
454.5
454.8
456.0
Z2 (L1)1
xtl (120
µm) + 3
frags.
0.0017
1811
141
15.
7
913.0
0.1
051
0.0731
1
0.19
0.5650
0.45
0.51
0.05605
0.39
454.9
454.8
454.2
Z3 (L3)8
xtls 120-
80 µm
0.0100
523
46
91.
8
272.2
0.0
916
0.0713
7
0.41
0.5522
0.51
0.84
0.05612
0.28
444.4
446.5
457.1
Z4 (T13)
20 xtls 80
µm
0.0130
733
58
120
.0
359.1
0.0
789
0.0686
2
0.51
0.5308
0.67
0.77
0.05610
0.43
427.8
432.3
456.2
Z5
(T16)13
xtls 120-
80 µm
0.0150
635
48
72.
2
600.5
0.0
730
0.0700
4
0.29
0.5617
0.31
0.93
0.05817
0.11
436.4
452.7
536.1
Sample
BN-1,
Andorra
Z1 (L5)7
xtlas.
Elongated
1:5, 120
0.0025
4205
356
10.
2
5427.5
0.0
914
0.0840
0
0.55
0.8215
0.58
0.94
0.07093
0.19
520.4
608.9
955.4
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µm
Z2 (L6) 6
elongated
xtlas 100-
120 µm
0.0015
4113
327
12.
7
2380.5
0.1
034
0.0775
8
0.38
0.6433
0.42
0.91
0.06014
0.17
481.7
504.4
608.7
Z3 (L4)7
xtls
elongated
1:5 , 100-
120 µm
0.0015
3936
321
25.
7
1142.5
0.0
909
0.0782
3
0.37
0.6184
0.49
0.79
0.05732
0.31
485.6
488.8
504.0
Z4 (T15)
10 xtls,
100-120
µm
0.0019
4303
395
42.
4
1078.9
0.0
739
0.0882
8
0.29
0.7946
0.32
0.91
0.06528
0.13
545.4
593.8
783.5
Z5
(T12)11
xtls, 100
µm
0.0015
4701
370
46.
7
711.4
0.0
842
0.0734
6
0.33
0.5686
0.36
0.90
0.05613
0.15
457.0
457.1
457.6
Z, zircon, (L number, lab code) number of crystals (xtls.); euhedral prisms, length (μm), 1:5 to 1:7 width/length ratio. All fractions were chemically
abraded (CA technique; Mattison (2005)).ID done using the 205Pb-233U-235U BSU-1B spike (courtesy MIT lab). Pbc common Pb (pg, picograms) *
Ratio corrected for mass fractionation (0.11 ± 0.02 % AMU Pb; U internally corrected from 233U-235U spike), spike contribution and analytical blank (2
pg Pb; 0.1 pg U). The other isotopic ratios are also corrected for initial common Pb after the model of Stacey and Kramers (1975). Corr.Coef, error
correlation coefficient of the 207Pb/235U and 206Pb/238U ratios. Data reduced with PbMacDat (Isachsen et al. 2007; www.earth-time.org).
Tabe 3
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Grain
207Pba
Ub
Pbb
Thb
206Pbcc
206Pbd
±2
207Pbd
±2
207Pbd
±2
rhoe
206Pb
±2
207Pb
±2
207Pb
±2
conc.f
(cps)
(ppm)
(ppm)
U
(%)
238U
(%)
235U
(%)
206Pb
(%)
238U
(Ma)
235U
(Ma)
206Pb
(Ma)
(%)
U161
4757
102
13
0,57
b.d.
0,11140
3,1
0,9633
4,0
0,0627
2,54
0,78
681
20
685
20
698
54
98
U162
215063
181
110
0,58
0,26
0,50980
2,6
12,62
2,9
0,1795
1,24
0,90
2656
57
2652
27
2649
21
100
U163
41158
581
50
0,16
b.d.
0,08784
2,5
0,7147
2,6
0,05901
0,95
0,93
543
13
548
11
567
21
96
U164
86795
545
98
0,49
0,13
0,16460
2,4
1,659
2,6
0,07311
1,06
0,91
982
22
993
17
1017
22
97
U165
39620
272
47
0,64
b.d.
0,15180
2,6
1,458
2,8
0,06967
1,08
0,93
911
22
913
17
919
22
99
U166
17167
289
25
0,42
5,73
0,08025
2,6
0,6379
3,3
0,05765
1,9
0,81
498
13
501
13
516
42
96
U167
46275
343
54
0,34
0,45
0,15060
2,6
1,438
2,9
0,06926
1,2
0,91
904
22
905
17
906
25
100
U168
20071
295
27
0,24
b.d.
0,08538
6,1
0,7979
6,9
0,06777
3,19
0,89
528
31
596
31
862
66
61
U169
22958
554
74
0,93
b.d.
0,11050
3,0
0,9474
3,8
0,06221
2,26
0,80
675
19
677
19
681
48
99
U170
21504
438
53
0,34
0,92
0,11660
2,9
0,9978
3,6
0,06208
2,24
0,79
711
19
703
19
677
48
105
U171
51401
174
76
0,75
b.d.
0,36690
3,2
6,268
3,5
0,1239
1,43
0,91
2015
56
2014
31
2013
25
100
U172
142257
232
129
0,20
b.d.
0,51140
3,4
12,67
4,1
0,1797
2,24
0,84
2662
76
2655
39
2650
37
100
U173
3059
64
9
0,83
b.d.
0,11510
2,6
0,998
4,3
0,06289
3,38
0,62
702
18
703
22
704
72
100
U174
47048
606
57
0,02
b.d.
0,10210
2,6
0,856
2,8
0,0608
1
0,93
627
15
628
13
632
22
99
U175
16357
151
19
0,31
1,39
0,11940
2,8
1,08
3,2
0,06561
1,43
0,89
727
20
744
17
794
30
92
U176
55620
699
74
0,21
0,66
0,10630
2,6
0,9008
4,2
0,06147
3,25
0,63
651
16
652
20
656
70
99
U177
12690
247
225
0,22
0,81
0,09757
4,3
0,8493
5,0
0,06313
2,58
0,86
600
25
624
24
713
55
84
U178
8716
173
21
0,39
1,55
0,11520
2,9
0,9903
3,9
0,06233
2,67
0,73
703
19
699
20
685
57
103
U179
22095
478
59
0,43
0,50
0,11620
3,6
1,013
4,2
0,06323
2,17
0,86
709
24
710
22
716
46
99
U180
54280
749
84
0,85
0,08
0,09521
2,8
0,7813
3,0
0,05951
1,15
0,92
586
15
586
13
586
25
100
U181
2990
71
8
0,35
13,77
0,10800
3,4
0,9022
4,4
0,06058
2,86
0,76
661
21
653
21
624
62
106
U182
44005
432
45
0,03
0,07
0,11160
3,0
0,9832
3,2
0,0639
0,87
0,96
682
20
695
16
738
18
92
U183
9694
181
24
0,43
2,18
0,12750
3,6
1,139
4,4
0,0648
2,56
0,81
774
26
772
24
768
54
101
U184
16958
318
25
0,59
b.d.
0,07113
2,4
0,5481
2,9
0,05588
1,65
0,82
443
10
444
10
448
37
99
U185
139406
1066
159
0,22
0,03
0,14810
2,9
1,468
3,3
0,07187
1,45
0,90
891
24
917
20
982
30
91
U186
7730
102
13
1,31
b.d.
0,09737
2,4
0,8085
3,2
0,06022
2,07
0,76
599
14
602
15
611
45
98
U187
22669
227
27
0,33
b.d.
0,11480
3,4
1,055
3,7
0,06662
1,41
0,92
701
23
731
19
826
29
85
U188
7557
45
8
0,30
b.d.
0,17840
3,0
1,837
3,8
0,07471
2,35
0,79
1058
29
1059
25
1061
47
100
U189
8854
112
23
0,97
1,04
0,16860
3,7
1,697
4,1
0,07299
1,76
0,90
1004
35
1007
27
1014
36
99
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U190
28152
156
52
0,22
0,61
0,32320
3,1
4,941
3,8
0,1109
2,16
0,82
1805
49
1809
32
1814
39
100
U191
57098
304
53
0,37
0,54
0,14890
5,4
2,332
6,1
0,1136
2,74
0,89
895
45
1222
44
1858
50
48
U192
3237
75
8
0,32
8,48
0,10740
4,0
0,9042
5,0
0,06109
3,02
0,80
657
25
654
24
642
65
102
U193
6917
167
18
0,35
2,12
0,10270
3,0
0,8314
4,0
0,05871
2,57
0,76
630
18
614
19
556
56
113
U194
7935
111
16
1,15
3,29
0,11130
2,8
0,9309
3,6
0,06069
2,3
0,77
680
18
668
18
628
50
108
U195
16027
375
37
0,08
b.d.
0,10440
3,5
0,8998
4,1
0,06252
2,14
0,85
640
21
652
20
692
46
93
U196
13182
339
38
0,50
1,25
0,10460
2,6
0,8769
3,2
0,06081
1,85
0,81
641
16
639
15
632
40
101
U197
7630
248
18
0,34
b.d.
0,07185
3,2
0,5624
4,3
0,05677
2,9
0,74
447
14
453
16
483
64
93
U198
47065
564
95
0,17
0,45
0,17130
3,7
1,746
4,0
0,07391
1,58
0,92
1020
35
1026
26
1039
32
98
U199
11234
126
34
1,81
0,87
0,17560
2,6
1,797
3,5
0,07426
2,28
0,75
1043
25
1045
23
1048
46
99
U200
43470
833
101
0,17
0,16
0,12230
4,0
1,101
6,5
0,06529
5,14
0,62
744
28
754
35
784
108
95
U206
10903
441
32
0,16
1,00
0,07454
4,1
0,5791
4,4
0,05635
1,49
0,94
463
19
464
16
466
33
99
U207
21652
266
58
1,04
2,67
0,17060
3,7
1,711
4,3
0,07275
2,22
0,85
1015
34
1013
28
1007
45
101
U208
9192
336
26
0,33
0,63
0,07507
3,8
0,5894
4,3
0,05694
1,96
0,89
467
17
470
16
489
43
95
U209
11171
268
26
0,04
b.d.
0,10490
3,4
0,8829
4,0
0,06102
2,09
0,85
643
21
643
19
640
45
101
U210
10854
114
28
0,99
b.d.
0,20150
2,7
2,172
3,5
0,07817
2,28
0,76
1183
29
1172
25
1151
45
103
U211
2495
61
7
0,39
6,43
0,10630
3,2
0,8924
4,1
0,06091
2,62
0,77
651
20
648
20
636
56
102
U212
5418
136
20
1,49
b.d.
0,10150
2,9
0,8586
3,7
0,06133
2,32
0,78
623
17
629
18
651
50
96
U213
108382
2415
206
0,20
0,55
0,08502
4,0
0,8058
4,6
0,06873
2,14
0,88
526
20
600
21
891
44
59
U214
8863
230
34
1,65
1,17
0,10230
2,5
0,852
3,3
0,06041
2,09
0,77
628
15
626
15
618
45
102
U215
17913
417
48
0,55
0,08
0,10330
3,1
0,8755
3,6
0,06144
1,69
0,88
634
19
639
17
655
36
97
U216
15014
183
21
0,46
0,22
0,10840
2,6
0,9223
2,9
0,06171
1,36
0,88
663
16
664
14
664
29
100
U217
14161
185
23
1,04
1,17
0,09736
2,4
0,8113
2,7
0,06044
1,3
0,88
599
14
603
13
619
28
97
U218
45683
346
53
0,40
0,02
0,14600
2,7
1,406
3,1
0,06985
1,47
0,88
879
22
892
18
924
30
95
U219
3187
41
4
0,59
6,15
0,09680
2,6
0,8245
3,4
0,06177
2,13
0,78
596
15
611
16
666
46
89
U220
10032
80
11
0,30
b.d.
0,12690
4,5
1,16
15,6
0,06629
14,9
0,29
770
33
782
89
816
311
94
U221
12165
146
17
0,59
1,65
0,10540
3,4
0,8903
4,0
0,06124
2,12
0,85
646
21
647
19
648
45
100
U222
10885
67
16
1,33
0,12
0,16750
5,0
1,731
6,0
0,07492
3,41
0,82
998
46
1020
39
1066
69
94
Spot size = 25µm.
206
Pb/
238
U error is the quadratic additions of the within run precision (2 SE) and the external reproducibility (2 SD) of the reference zircon.
207
Pb/
206
Pb error propagation (
207
Pb signal dependent) following Gerdes & Zeh (2009).
207
Pb/
235
U error is the quadratic addition of the
207
Pb/
206
Pb and
206
Pb/
238
U uncertainty.
a
Within run background-corrected mean
207
Pb signal in cps (counts per second).
b
U and Pb content and Th/U ratio were calculated relative to BB reference zircon.
c
percentage of the common Pb on the
206
Pb. b.d. = below dectection limit.
ACCEPTED MANUSCRIPT
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d
corrected for background, within-run Pb/U fractionation (in case of
206
Pb/
238
U) and common Pb using Stacy and Kramers (1975) model Pb composition and subsequently normalised to BB (ID-TIMS value/measured value);
207
Pb/
235
U calculated using
207
Pb/
206
Pb/(
238
U/
206
Pb*1/137.818)
e
rho is the
206
Pb/
238
U/
207
Pb/
235
U error correlation coefficient.
f
degree of concordance =
206
Pb/
238
U age /
207
Pb/
206
Pb age x 100
reference zircon BB1
BB1-1
13637
362
32
0,17
0,51
0,09068
2,4
0,74
3,7
0,05919
2,83
0,64
560
13
562
16
574
62
97
BB1-2
13551
354
32
0,18
0,49
0,09145
2,8
0,7486
3,3
0,05937
1,77
0,85
564
15
567
15
581
39
97
BB1-3
13905
362
32
0,18
0,50
0,09100
3,4
0,7362
3,8
0,05867
1,82
0,88
561
18
560
17
555
40
101
BB1-4
13445
354
31
0,17
0,35
0,09049
2,9
0,7324
3,6
0,05871
2,12
0,81
558
15
558
15
556
46
100
BB1-5
13715
366
33
0,17
0,53
0,09214
3,2
0,745
4,1
0,05864
2,58
0,78
568
18
565
18
554
56
103
BB1-6
14257
375
34
0,18
0,39
0,09116
3,1
0,7384
3,8
0,05874
2,26
0,80
562
16
561
17
558
49
101
BB1-7
13817
383
34
0,18
0,57
0,09022
2,9
0,7347
3,5
0,05906
1,93
0,83
557
16
559
15
569
42
98
BB1-8
14492
370
34
0,19
0,09
0,09262
2,6
0,7541
3,4
0,05905
2,1
0,78
571
14
571
15
569
46
100
BB1-9
14218
388
35
0,18
0,57
0,09179
3,3
0,7457
4,3
0,05892
2,69
0,78
566
18
566
19
564
59
100
BB1-10
13886
380
34
0,18
0,43
0,08989
3,5
0,7335
4,2
0,05918
2,29
0,83
555
18
559
18
574
50
97
BB1-11
12858
376
33
0,18
0,42
0,08935
3,4
0,7225
4,0
0,05865
1,97
0,87
552
18
552
17
554
43
100
BB1-12
13539
382
34
0,18
0,44
0,09053
3,2
0,7391
3,8
0,05921
2,03
0,84
559
17
562
16
575
44
97
BB1-13
14074
401
36
0,18
0,60
0,09148
3,0
0,744
3,5
0,05898
1,86
0,85
564
16
565
15
566
41
100
BB1-14
13759
395
36
0,19
0,50
0,09238
3,3
0,7463
3,6
0,05859
1,44
0,92
570
18
566
16
552
32
103
BB1-15
13348
390
35
0,18
0,58
0,09028
3,2
0,7299
3,6
0,05863
1,59
0,89
557
17
556
15
554
35
101
BB1-16
13408
377
34
0,18
0,68
0,09290
3,3
0,7507
3,9
0,05861
2,04
0,85
573
18
569
17
553
45
104
BB1-17
13630
396
36
0,18
0,49
0,09090
3,2
0,739
4,1
0,05896
2,46
0,80
561
17
562
18
566
53
99
BB1-18
13736
407
36
0,18
0,53
0,09110
3,6
0,7464
4,0
0,05942
1,69
0,91
562
19
566
17
583
37
96
BB1-19
13414
413
36
0,17
0,50
0,08984
4,0
0,7295
4,6
0,05889
2,23
0,87
555
21
556
20
563
49
99
BB1-20
12869
380
34
0,18
0,52
0,09166
3,5
0,7439
4,0
0,05886
1,94
0,87
565
19
565
17
562
42
101
BB1-21
13446
411
37
0,18
0,57
0,09166
2,7
0,7511
3,5
0,05943
2,18
0,78
565
15
569
15
583
47
97
BB1-22
13529
396
35
0,19
0,42
0,09009
3,3
0,7308
4,1
0,05884
2,33
0,82
556
18
557
18
561
51
99
BB1-23
13519
419
38
0,18
0,55
0,09199
3,5
0,7527
4,2
0,05934
2,37
0,83
567
19
570
19
580
51
98
BB1-24
13275
422
38
0,19
0,47
0,09113
3,0
0,7417
3,5
0,05903
1,82
0,86
562
16
563
15
568
40
99
BB1-25
13252
435
39
0,18
0,69
0,09122
3,3
0,7421
3,7
0,059
1,85
0,87
563
18
564
16
567
40
99
BB1-26
13242
427
38
0,18
0,50
0,09056
3,6
0,7417
4,2
0,0594
2,01
0,88
559
20
563
18
582
44
96
BB1-27
13183
442
39
0,17
0,61
0,08987
3,3
0,7304
3,9
0,05895
2,17
0,83
555
17
557
17
565
47
98
BB1-28
13250
429
39
0,19
0,46
0,09240
3,3
0,7501
3,9
0,05887
1,98
0,86
570
18
568
17
562
43
101
mean
(n=28):
0,0911
0,7407
0,0590
562
563
566
2SD(abs):
0,0019
0,0162
0,0005
11
10
20
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2SD(%)
2,05
2,19
0,91
reference zircon Plesovice
Pleso4
11778
573
29
0,09
0,00
0,05334
2,4
0,3916
3,1
0,05325
1,85
0,80
335
8
336
9
339
42
99
Pleso5
12075
575
29
0,09
0,22
0,05328
2,5
0,3916
2,9
0,0533
1,32
0,89
335
8
336
8
342
30
98
Pleso33
11729
575
29
0,09
0,23
0,05335
2,5
0,3904
3,2
0,05307
1,99
0,78
335
8
335
9
332
45
101
Pleso34
11567
562
28
0,09
0,20
0,05327
2,5
0,3938
2,8
0,05362
1,34
0,88
335
8
337
8
355
30
94
Pleso63
11436
552
28
0,09
0,24
0,05370
2,7
0,3947
3,1
0,05331
1,6
0,86
337
9
338
9
342
36
99
Pleso64
11256
559
28
0,09
0,31
0,05351
2,7
0,3939
2,9
0,05339
1,11
0,92
336
9
337
8
345
25
97
Pleso103
11867
586
30
0,09
0,20
0,05466
2,3
0,4029
2,7
0,05346
1,48
0,84
343
8
344
8
348
33
99
Pleso104
11804
573
29
0,09
0,25
0,05379
2,6
0,3967
3,0
0,05349
1,5
0,86
338
8
339
9
350
34
97
Pleso153
11871
601
30
0,09
0,24
0,05369
2,9
0,3932
3,3
0,05312
1,5
0,89
337
10
337
9
334
34
101
Pleso154
11317
591
30
0,09
0,22
0,05339
2,4
0,39
2,7
0,05297
1,19
0,90
335
8
334
8
328
27
102
Pleso203
11278
581
30
0,09
0,08
0,05418
2,8
0,3981
3,2
0,05329
1,52
0,88
340
9
340
9
341
34
100
Pleso204
11130
580
29
0,09
0,15
0,05373
2,7
0,3951
3,1
0,05334
1,53
0,87
337
9
338
9
343
35
98
Pleso253
11098
584
30
0,09
0,19
0,05448
2,5
0,4002
2,9
0,05327
1,5
0,85
342
8
342
8
340
34
100
Pleso254
11051
576
29
0,09
0,24
0,05312
2,7
0,3904
3,1
0,0533
1,53
0,87
334
9
335
9
342
35
98
Pleso303
10346
567
29
0,09
0,16
0,05488
2,5
0,3973
3,2
0,05251
1,88
0,81
344
9
340
9
308
43
112
Pleso304
10014
550
28
0,09
0,17
0,05325
2,3
0,3894
2,8
0,05304
1,57
0,83
334
8
334
8
330
36
101
Pleso353
9722
539
28
0,09
0,19
0,05432
2,5
0,3982
3,2
0,05316
2
0,79
341
8
340
9
336
45
102
Pleso403
7816
424
22
0,08
0,18
0,05431
2,4
0,4024
2,9
0,05373
1,61
0,84
341
8
343
9
360
36
95
Pleso404
7295
417
21
0,08
0,20
0,05239
2,5
0,3837
2,9
0,05311
1,52
0,85
329
8
330
8
333
34
99
Pleso453
7587
428
22
0,08
0,16
0,05378
2,6
0,3965
3,1
0,05347
1,66
0,85
338
9
339
9
349
37
97
Pleso454
7292
416
21
0,08
0,17
0,05341
2,6
0,3911
2,9
0,05311
1,12
0,92
335
9
335
8
333
25
101
Pleso503
11277
657
33
0,09
0,18
0,05381
2,3
0,3929
2,8
0,05296
1,58
0,83
338
8
336
8
327
36
103
Pleso504
11104
653
33
0,09
0,21
0,05368
2,4
0,3931
2,9
0,05311
1,75
0,80
337
8
337
8
333
40
101
Pleso553
11168
668
34
0,09
0,17
0,05388
2,7
0,3996
3,2
0,05379
1,71
0,84
338
9
341
9
362
39
93
Pleso554
11175
662
34
0,09
0,19
0,05426
2,5
0,4037
2,9
0,05396
1,42
0,87
341
8
344
8
370
32
92
Pleso555
10836
614
31
0,09
0,21
0,05397
2,7
0,3957
3,5
0,05318
2,13
0,79
339
9
339
10
336
48
101
Pleso556
10818
568
29
0,09
0,23
0,05389
2,7
0,394
3,4
0,05303
2,11
0,79
338
9
337
10
330
48
102
mean
(n=27):
0,0538
0,3948
0,0533
338
338
340
2SD(abs):
0,0011
0,0092
0,0006
7
7
25
2SD(%)
1,99
2,33
1,11
reference zircon KA (KaapValley)
KA1-7
30714
27
21
0,52
6,05
0,64720
4,1
22,85
4,6
0,2561
2,15
0,88
3217
104
3221
46
3223
34
100
KA1-35
33401
29
23
0,50
1,49
0,65860
3,5
23,27
4,3
0,2562
2,38
0,83
3262
91
3238
42
3224
38
101
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KA1-36
22925
19
16
0,53
b.d.
0,65420
3,6
23,23
4,0
0,2576
1,88
0,88
3244
91
3237
40
3232
30
100
KA1-65
37113
31
26
0,48
b.d.
0,66010
2,8
23,28
3,6
0,2558
2,18
0,79
3268
73
3239
35
3221
34
101
KA1-66
21855
19
16
0,55
0,87
0,66300
3,5
23,5
4,2
0,2571
2,29
0,84
3279
92
3248
42
3229
36
102
KA1-106
31038
27
22
0,51
1,51
0,64270
4,8
23,14
5,6
0,2611
2,84
0,86
3200
123
3233
56
3254
45
98
KA1-155
36739
33
26
0,39
0,66
0,64530
4,1
22,94
5,0
0,2579
2,87
0,82
3210
104
3224
50
3234
45
99
KA1-156
23697
23
18
0,54
2,13
0,64440
4,6
22,77
5,0
0,2562
1,98
0,92
3206
117
3217
50
3224
31
99
KA1-205
30702
31
24
0,36
b.d.
0,64890
4,0
22,94
4,5
0,2564
1,91
0,90
3224
103
3224
44
3225
30
100
KA1-305
35624
36
31
0,90
b.d.
0,63980
4,2
22,62
4,6
0,2564
1,87
0,91
3188
107
3211
46
3225
30
99
KA1-355
33363
34
29
0,69
b.d.
0,66280
4,0
23,45
4,7
0,2567
2,51
0,85
3278
103
3246
47
3226
40
102
KA1-405
47123
49
37
0,36
3,31
0,64010
4,5
22,62
5,1
0,2562
2,4
0,88
3189
113
3211
50
3224
38
99
KA1-455
40727
42
34
0,61
0,90
0,64230
3,5
22,83
4,0
0,2578
1,97
0,87
3198
90
3220
40
3233
31
99
KA1-505
16815
17
15
0,66
1,43
0,66350
3,4
23,47
3,8
0,2566
1,87
0,87
3281
87
3247
38
3226
29
102
mean
(n=14):
0,6509
230,650
0,2570
3232
3230
3228
2SD(abs):
0,0182
0,6173
0,0027
71
26
17
2SD(%)
2,79
2,68
1,05
Spot size = 25µm.
206
Pb/
238
U error is the quadratic additions of the within run precision (2 SE) and the external reproducibility (2 SD) of the reference zircon.
207
Pb/
206
Pb error propagation (
207
Pb signal dependent) following Gerdes & Zeh (2009).
207
Pb/
235
U error is the quadratic addition of the
207
Pb/
206
Pb and
206
Pb/
238
U uncertainty.
a
Within run background-corrected mean
207
Pb signal in cps (counts per second).
b
U and Pb content and Th/U ratio were calculated relative to BB reference zircon.
c
percentage of the common Pb on the
206
Pb. b.d. = below dectection limit.
d
corrected for background, within-run Pb/U fractionation (in case of
206
Pb/
238
U) and common Pb using Stacy and Kramers (1975) model Pb composition and
subsequently normalised to BB (ID-TIMS value/measured value);
207
Pb/
235
U calculated using
207
Pb/
206
Pb/(
238
U/
206
Pb*1/137.818)
e
rho is the
206
Pb/
238
U/
207
Pb/
235
U error correlation coefficient.
f
degree of concordance =
206
Pb/
238
U age /
207
Pb/
206
Pb age x 100
Table 4
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Figure 1
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Figure 2
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Figure 2(Continued)
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Figure 3
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Figure 4
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Figure 5
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Figure 7
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Figure 9
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Figure 10
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Figure 11
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Figure 12
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Figure 13
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Figure 15
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