M o u t h o u m e t

Aude

Agly

Luzenac

St. Barthélémy

C a s t i l l o n

B a r o u s s e

M i l h a s

Trois seigneurs

A r i z e

BessèdeSalvezines

A g l y

Aigue

tte

Boulzane

S y n f o r mB a s A g l y

B o u c h e v i l l e S y n f o r m

A X I A L Z O N E

A X I A L Z O N E

St GaudensLannemezan

TARBES

PAU

St Girons

Pamiers

Foix

Tarascon-sur-Ariège

Quillan

Limoux

PERPIGNAN

Mauléon-Licharre

St JeanPied-de-Port

St Jean-de-Luz

SAN SEBASTIAN

Oloron-Ste Marie

PAMPLONA

Lourdes

GranulitePeridotite Migmatite Amphibolite Intrusivegranitoids

Greenschiste Silurian Devonian Carboniferous

N

N

0 5 10 20 30 km

Aude

Agly

NN

Aude

Agly

St. Barthélémy

C a s t i l l o n

B a r o u s s e

M i l h a s

Trois seigneurs

A r i z e

BessèdeSalvezines

A g l y

Aigue

tte

Boulzane

S y n f o r mB a s A g l y

B o u c h e v i l l e S y n f o r m

A X I A L Z O N E

St GaudensLannemezan

TARBES

PAU

St Girons

Pamiers

Foix

Tarascon-sur-Ariège

Quillan

Limoux

PERPIGNAN

Mauléon-Licharre

St JeanPied-de-Port

St Jean-de-Luz

SAN SEBASTIAN

Oloron-Ste Marie

PAMPLONA

Lourdes

0 5 10 20 30 km

A X I A L Z O N E385

560 385

495

495

<450

<450570

570580

555550 550520

510<450

405

450400

<400560337 356387 494

568353

609621353

519540560530

576572

542437

532600

550610

230

350200

542

346300

233

587

333358

600289

303301

320 430380594

CenomanianSantonian

sedimentarybreccias

Peridotite upper Cretaceousto Quaternary

Paleozoicbasement

Triassic tolower Aptian

upper Aptianlower Albian

middle Albianlower Cenomanian

333 RSCM Peak Temperaturethis study

570 Temperature fromGoldberg and Leyreloup(1990)

Simplified geologic map of the North Pyrenean Hercynian Massifs and peridotite outcrops

P e a k t e m p e r a t u r e s o f t h e H T / L P c r e t a c e o u s m e t a m o r p h i s m i n t h e P y r e n e e s

Clerc Camille1, 2 ; Lagabrielle Y.2 ; Reynaud J.-Y.3 ; Boulvais P.4 ; Bousquet R.4 ; Lahfid A.1, 5 ; Vauchez A.2 ; Mahé S.2, 6

FROM CRUSTAL THINNING TO MANTLE EXHUMATION: WHAT THE PYRENEAN BRECCIA FORMATIONS TELL US ?

Corresponding author: clerc@geologie.ens.fr1 Laboratoire de Géologie, CNRS-UMR 8538, Ecole Normale Supérieure, Paris, France; 2 Géosciences Montpellier, Montpellier, France;

3 Muséum national d'Histoire naturelle, Paris and ISTeP Paris, France; 4 Géosciences Rennes, France;5 BRGM / LMA / MIN, Orléans, France; 6 Ecole des Mines, Alès, France

Aude

Agly

Luzenac

St. Barthélémy

C a s t i l l o n

B a r o u s s e

M i l h a s

Trois seigneurs

A r i z e

BessèdeSalvezines

A g l y

Aigue

tte

Boulzane

S y n f o r mB a s A g l y

B o u c h e v i l l e S y n f o r m

A X I A L Z O N E

A X I A L Z O N E

St GaudensLannemezan

TARBES

PAU

St Girons

Pamiers

Foix

Tarascon-sur-Ariège

Quillan

Limoux

PERPIGNAN

Mauléon-Licharre

St JeanPied-de-Port

St Jean-de-Luz

BAYONNE

SAN SEBASTIAN

Orthez

Oloron-Ste Marie

PAMPLONA

Lourdes

0 5 10 20 30 km

N

INTRODUCTION: Several formations with various breccia types occur in Mesozoic basins disseminated along the North Pyrenean fault, on the northern flank of the French Pyrenees. Due to their location along the Iberia-Europa plate boundary, the North Pyrenean breccia formations represent complex archives documenting the tectonic and

LOOKING FOR A POSTDOCCenomanianSantonian

sedimentarybreccias

Peridotite upper Cretaceousto Quaternary

Paleozoicbasement

Triassic tolower Aptian

upper Aptianlower Albian

middle Albianlower Cenomanian

References: Goldberg, J.-M., et A.F. Leyreloup. 1990. High temperature-low pressure Cretaceous metamorphism related to crustal thinning (Eastern North Pyrenean Zone, France). Contributions to Mineralogy and Petrology 104, 194–207; * Barbieri, M., U. Masi, & L. Tolomeo. 1979. Stable isotope evidence for a marine origin of ophicalcites from the north-central Apennines (Italy). Marine Geology 30, 193–204; ** Evans, C.A., & M. Baltuck. 1988. Low-Temperature Alteration of Peridotite, Hole 637A. Proceedings of the Ocean Drilling Program, 103 Scientific Results, 235–239; Milliken, K.L., & J.K. Morgan. 1996. Chemical Evidence for Near-Seafloor Precipitation of Cacite in Serpentinites (Site 897) and Serpentinite Breccias (Site 899), Iberia Abyssal Plain. Proceedings of the Ocean Drilling Program, 149 Scientific Results, 553–558; Skelton, Alasdair D.L., and J. W. Valley. 2000. The relative timing of serpentinisation and mantle exhumation at the ocean-continent transition, Iberia: constraints from oxygen isotopes. Earth and Planetary Science Letters 178, 327–338; *** Weissert, Helmut, & Daniel Bernoulli. 1984. Oxygen isotope composition of calcite in Alpine ophicarbonates: a hydro-thermal or Alpine metamorphic signal ? Eclogae geol. Helv. 77, 29–43; Barrett, Timothy J., & H. Friedrichsen. 1989. Stable isotopic composition of atypical ophiolitic rocks from east Liguria, Italy. Chemical Geology: Isotope Geoscience section 80, 71–84; Demeny, A., T. Vennemann, & F. Koller. 2007. Stable isotope compositions of the Penninic ophiolites of the Köszeg-Rechnitz series. Central European Geology 50, 29–46; Früh-Green, G., H. Weissert, & D. Bernoulli. 1990. A multiple fluid history recorded in Alpine ophiolites. Journal of the Geological Society 147, 959–970.

Alpine medium -T ophicalcites*(seawater or metamorphic �uids related)

Iberian marginlow-Temperature ophicalcites

(seawater related)**

-8.000

-6.000

-4.000

-2.000

0.000

2.000

4.000

12.00 17.00 22.00 27.00 32.00

δ13C

δ18O

veinsmatrixesclasts

Weste

rn P

yrenees

M oncaup

Moncaup

Eastern Pyren

ees

Alps***Iberian Margin**Apennine*

Ophicalcites fromlitterature:

This study:

Ophicalcites:Agly breccias

F o l d

Semi-ductile syn-metamorphic breccias: The boudinage of silicic or dolomitic beds is the expression of rheologic heterogeneities during the ductile stretching of the meso-zoic cover.

Cataclastic breccias and gouges: The clasts are barely displaced and they display a relatively monogenetic character. These tectonic breccias result from the disruption of the material under cooling conditions. The cata-clastic intervals are mainly hosted by the Triassic and Liassic weaker levels.

Anhydrite vein

Peridotite

Sapphirine bearing

sandstone

Anh

ydrit

e ve

in

Decoupling along the weaker evapo-ritic levels triggers a juxtaposition of the pre-rift sediments directly on the exhumed mantle. We re-interpret the sapphirine bearing sandstones lying around the eastern Pyrenean perido-tites as remnants of these Triassic evaporites transformed by contact metamorphism with the uprising peri-dotites and lower crustal units.

Hydraulic-tectonic breccias: Mid-Cretaceous stretching of the continental crust is accompanied by circulations of hot fluids. These fluids are responsible for allochemical metamorphism, metasomatic reactions and hydrothermalism.

Strike-slip Extension N

SW

EN

SW

E Transtension

S i m p l i f i e d g e o l o g i c m a p o f t h e P y r e n e e s

Polymictic sedimentary breccias: Their composition is dominated by clasts of Mesozoic metasediments. Locally, close to subcontinental mantle bodies, the sedimentary breccias include numerous clasts of

ultramafic and/or crustal basement rocks. Such breccias are the witnesses of the disruption and c l a s t i c sedimentation of the sedimentary cover in a context of hyper-extended crust and mantle exhumation.

Stable isotope composition of some Pyrenean breccias and ophicalcites

Syn-metamorphic extensional and/or gravity slidingof pre-rift mesozoic cover on unroofedUB basement

- Tearing of Allochtonous carbonates and UB basement exhumation- Chaotic sedimentation inbetween the individualizing rafts and locally over the mesozoic rafts.- Sliding rafts overthrusting breccia 1- Breccia 2: UB clasts + clasts of mesozoic metasediments + clasts of breccia 1

A

B

2 km

Mesozoic cover

Triassic-Liassic evaporitesUB basement Lower crust

breccia 1 breccia 1

olistostrombreccia 2

olistostrombreccia 2

U p l i f t

Parallel carbonate veining in mantle Rock - Urdach

Hydraulic fracturation in mesozoic marbles - Agly

Cataclastic breccias and gouges - Agly

Cataclastic breccias of marbles- Aulus trough

Cataclastic breccias of peridotite - Aulus trough

Polimictic sedimentry breccias - Agly

Ophicalcite - Lherzmarble-peridotite bearing sedimentary breccias- Lherz

The Pyrenean ophicalcites and breccias are displaced toward low d18O values with respect to typicalmarines ones. This could be the sign of their formation in a continental lacustrine environment.

S0

sedimentary evolution of the Pyrenean realm during the Aptian-Albian period. In particular, the North Pyrenean breccia formations have recorded the main stages of crustal thinning, continental break-up and mantle exhumation, which occurred along the North Pyrenean Zone (NPZ).