U N C O R R E C T E D P R O O F Exhumation, doming and slab retreat in the Betic Cordillera (SE Spain): in situ 40 Ar/ 39 Ar ages and P–T–d–t paths for the Nevado-Filabride complex R. AUGIER, 1 P. AGARD, 1 P. MONIE ´ , 2 L. JOLIVET, 1 C. ROBIN 3 AND G. BOOTH-REA 4 1 Laboratoire de 1 Tectonique, UMR 7072, case 129, Universite ´ de Pierre et Marie Curie, 4, place Jussieu, 75252, Paris Cedex 5, France 2 Laboratoire Dynamique de la Lithosphe `re, UMR 5573, Universite ´ Montpellier, 2, Place Emile Bataillon, 34095, Montpellier Cedex 05, France 3 Geosciences, UMR 4661, Universite ´ de Rennes I, 263, Avenue du Ge ´ne ´ral Leclerc, CS 74205, 35042, Rennes Cedex, France 4 Departamento de Geodinamica, Universidad de Granada-CSIC, Instituto Andaluz de Ciencias de la Tierra, Fuentenueva s/n 18002-Granada, Spain ABSTRACT The combination of metamorphic petrology tools and in situ laser 40 Ar/ 39 Ar dating on phengite (linking time of growth, compositions and P–T conditions) enables us to identify a detailed P–T–d–t path for the still debated tectonometamorphic evolution of the Nevado-Filabride complex and infer new geody- namic-scale constraints. Our data show an isothermal decompression (at 550 °C) from 20 kbar for the Be´dar-Macael unit and 14 kbar for the Calar Alto unit down to c. 3–4 kbar for both units at 2.8 mm year )1 . At 22–18 Ma, this first part of the exhumation is followed by a final exhumation at 0.6 mm year )1 along a high-temperature low-pressure (HTLP) gradient of c. 60 °C km )1 . The age of the peak of pressure is not precisely known but it is shown that it is around 30 Ma and possibly older, which is at variance with recent models suggesting a younger age for high-pressure (HP) metamorphism. Most of the exhumation is related to late-orogenic extension from c. 30 to 22–18 Ma. Thus the formation of the main ductile extensional shear zone, the Filabres Shear Zone (FSZ), occurred at 22–18 Ma and is clearly associated with a top-to-the-west shear sense once the FSZ is well localized. The transition from ductile to brittle then occurred at c. 14 Ma. The final exhumation, accommodated by brittle deformation, occurred from c. 14 to 9 Ma and was accompanied, from 12 to 8 Ma, by the formation of nearby extensional basins. The duration of the extensional process is c. 20 Myr which argues in favour of a progressive slab retreat from c. 30 to 9 Ma. The change in the shape of the P–T path at 22–18 Ma together with strain localization along the main top-to-the-west shear zone suggests that this date corresponds to a change in the direction of slab retreat from southwards to westwards. Key words: Betic Cordillera; exhumation velocities; in situ 40 Ar/ 39 Ar dating; P–T–d–t paths; phengite. INTRODUCTION The mechanisms and processes by which deep-seated metamorphic rocks of highly extended back-arc terr- anes were transported to the surface, such as the migmatitic gneiss dome of Naxos (Greece; Avigad et al., 1997; Vanderhaeghe, 2004) or the Betic Cor- dillera domes (Martı´nez-Martı´nez et al., 2002), are still debated (Yin, 1991; Wernicke, 1992; Selverstone et al., 1995; Axen et al., 1998; Jolivet et al., 2004). In par- ticular, extensional structures alone cannot discrimin- ate between syn- or post-orogenic settings (or both). To achieve this, continuous P–T paths relying on blastesis–deformation relationships (Spear et al., 1984; Parra et al., 2002) must be obtained for samples rela- ted to the main exhumation shear zones (e.g. Lister et al., 1984; Spear et al., 1990; Jolivet et al., 1998; Parra et al., 2002). In situ dating of minerals with textural control can provide the crucial link between ages and textures with high spatial resolution as pro- posed by Muller (2003). The aim of this paper is to present such an integrated pressure–temperature– deformation–time (P–T–d–t) approach for the Betic Cordillera domes. The Betic-Rif orogen resulted from the closure of the westernmost part of the Tethys Ocean between Africa and the Iberian Peninsula. Subduction and crustal thickening leading to the formation of high-pressure low-temperature (HPLT) metamorphic units probably took place from the Eocene to the Oligocene and were followed by late-orogenic extension after c. 35–30 Ma (Platt et al., 1998; Jolivet & Faccenna, 2000). The causes of late orogenic extension are still debated, with at least three contrasting models based on slab retreat (Royden, 1993; Lonergan & White, 1997 2 ), delamina- tion of subcontinental lithosphere (Garcı´a-Duen˜ as et al., 1992; Martı´nez-Martı´nez & Azan˜o´n, 1997; Cal- vert et al., 2000) or convective removal of thickened J M G 5 8 1 B Dispatch: 17.5.05 Journal: JMG CE: Manikandan Journal Name Manuscript No. Author Received: No. of pages: 25 PE: Raymond J. metamorphic Geol., 2005 doi:10.1111/j.1525-1314.2005.00581.x Ó 2005 Blackwell Publishing Ltd 1
Transcript
UNCORRECTEDPROOF
Exhumation, doming and slab retreat in the Betic Cordillera(SE Spain): in situ
40Ar/39Ar ages and P–T–d–t paths for theNevado-Filabride complex
R. AUGIER,1 P. AGARD,1 P. MONIE ,2 L. JOLIVET,1 C. ROBIN3 AND G. BOOTH-REA4
1Laboratoire de1 Tectonique, UMR 7072, case 129, Universite de Pierre et Marie Curie, 4, place Jussieu, 75252, Paris Cedex 5,France2Laboratoire Dynamique de la Lithosphere, UMR 5573, Universite Montpellier, 2, Place Emile Bataillon, 34095, MontpellierCedex 05, France3Geosciences, UMR 4661, Universite de Rennes I, 263, Avenue du General Leclerc, CS 74205, 35042, Rennes Cedex, France4Departamento de Geodinamica, Universidad de Granada-CSIC, Instituto Andaluz de Ciencias de la Tierra, Fuentenueva s/n18002-Granada, Spain
ABSTRACT The combination of metamorphic petrology tools and in situ laser 40Ar/39Ar dating on phengite (linkingtime of growth, compositions and P–T conditions) enables us to identify a detailed P–T–d–t path for thestill debated tectonometamorphic evolution of the Nevado-Filabride complex and infer new geody-namic-scale constraints. Our data show an isothermal decompression (at 550 �C) from 20 kbar for theBedar-Macael unit and 14 kbar for the Calar Alto unit down to c. 3–4 kbar for both units at2.8 mm year)1. At 22–18 Ma, this first part of the exhumation is followed by a final exhumation at0.6 mm year)1 along a high-temperature low-pressure (HTLP) gradient of c. 60 �C km)1. The age of thepeak of pressure is not precisely known but it is shown that it is around 30 Ma and possibly older, whichis at variance with recent models suggesting a younger age for high-pressure (HP) metamorphism. Mostof the exhumation is related to late-orogenic extension from c. 30 to 22–18 Ma. Thus the formation ofthe main ductile extensional shear zone, the Filabres Shear Zone (FSZ), occurred at 22–18 Ma and isclearly associated with a top-to-the-west shear sense once the FSZ is well localized. The transition fromductile to brittle then occurred at c. 14 Ma. The final exhumation, accommodated by brittledeformation, occurred from c. 14 to 9 Ma and was accompanied, from 12 to 8 Ma, by the formation ofnearby extensional basins. The duration of the extensional process is c. 20 Myr which argues in favourof a progressive slab retreat from c. 30 to 9 Ma. The change in the shape of the P–T path at 22–18 Matogether with strain localization along the main top-to-the-west shear zone suggests that this datecorresponds to a change in the direction of slab retreat from southwards to westwards.
The mechanisms and processes by which deep-seatedmetamorphic rocks of highly extended back-arc terr-anes were transported to the surface, such as themigmatitic gneiss dome of Naxos (Greece; Avigadet al., 1997; Vanderhaeghe, 2004) or the Betic Cor-dillera domes (Martınez-Martınez et al., 2002), are stilldebated (Yin, 1991; Wernicke, 1992; Selverstone et al.,1995; Axen et al., 1998; Jolivet et al., 2004). In par-ticular, extensional structures alone cannot discrimin-ate between syn- or post-orogenic settings (or both).To achieve this, continuous P–T paths relying onblastesis–deformation relationships (Spear et al., 1984;Parra et al., 2002) must be obtained for samples rela-ted to the main exhumation shear zones (e.g. Listeret al., 1984; Spear et al., 1990; Jolivet et al., 1998;Parra et al., 2002). In situ dating of minerals withtextural control can provide the crucial link between
ages and textures with high spatial resolution as pro-posed by Muller (2003). The aim of this paper is topresent such an integrated pressure–temperature–deformation–time (P–T–d–t) approach for the BeticCordillera domes.
The Betic-Rif orogen resulted from the closure of thewesternmost part of the Tethys Ocean between Africaand the Iberian Peninsula. Subduction and crustalthickening leading to the formation of high-pressurelow-temperature (HPLT) metamorphic units probablytook place from the Eocene to the Oligocene and werefollowed by late-orogenic extension after c. 35–30 Ma(Platt et al., 1998; Jolivet & Faccenna, 2000). Thecauses of late orogenic extension are still debated, withat least three contrasting models based on slab retreat(Royden, 1993; Lonergan & White, 19972 ), delamina-tion of subcontinental lithosphere (Garcıa-Duenaset al., 1992; Martınez-Martınez & Azanon, 1997; Cal-vert et al., 2000) or convective removal of thickened
J M G 5 8 1 B Dispatch: 17.5.05 Journal: JMG CE: Manikandan
Journal Name Manuscript No. Author Received: No. of pages: 25 PE: Raymond
J. metamorphic Geol., 2005 doi:10.1111/j.1525-1314.2005.00581.x
� 2005 Blackwell Publishing Ltd 1
UNCORRECTEDPROOF
crust (Platt & Vissers, 1989; Vissers et al., 1995) beingpropounded. One major difference between the threescenarios pertains to the timing: convective removal ordelamination is assumed to be more instantaneousthan slab retreat, which also shows a migration of thelocus of extension. The clustering of overall agesaround 20 Ma in the Betic-Rif orogen has often beentaken as an argument in favour of a sudden removal ofthe lower lithosphere (Platt & Vissers, 1989). It is thuscrucial to obtain a precise timing and scenario ofexhumation (P–T–d–t path) of the various metamor-phic units of the internal Betics, especially for thelowermost Nevado-Filabride (NF) complex.
The internal zones of the Betic Cordillera corres-pond to the stacking of the NF, Alpujarride andMalaguide complexes (from bottom to top), separatedfrom each other by major crustal-scale extensionalshear zones: the Filabres Shear Zone (FSZ; Garcıa-Duenas et al., 1992) and the Malaguide-AlpujarrideContact (MAC; Vissers et al., 1995) respectively. Al-though both the NF and the Alpujarride units sufferedan initial high-pressure low-temperature (HPLT)metamorphic event (e.g. Gomez-Pugnaire & Soler,19873 ; Goffe et al., 1989; Azanon et al., 1994; Azanon& Goffe, 1997; Booth-Rea et al., 2002), the P–T,structural and time evolution of the NF complex is lessunderstood. Indeed, published P–T paths for the NFcomplex include both cooling (Puga et al., 2000a,b;Lopez Sanchez-Vizcaıno et al., 2001; De Jong, 2003)and heating during decompression (Gomez-Pugnaire& Soler, 1987; Booth-Rea et al., 2003a). The P–Ttrajectories and peak temperatures undergone by theserocks range between 500 �C (Gonzalez-Casado et al.,1995) and 700 �C (Lopez Sanchez-Vizcaıno et al.,2001). In addition, neither recent P–T estimates northe shape of the P–T path are available for theuppermost unit of the NF complex (i.e. Bedar-Macaelunit, see below).
While the main exhumation of the Alpujarridesoccurred through a roughly N–S regional penetrativeextension between 22 and 18 Ma (Zeck et al., 1989,1992, 1998, 2000; Crespo-Blanc et al., 1994; Monieet al., 1994; Crespo-Blanc, 1995; Platt et al., 1996),exhumation of the NF complex took place through aroughly E–W regional penetrative ductile extension(Garcıa-Duenas et al., 1992; Martınez-Martınez &Azanon, 1997; Martınez-Martınez et al., 2002), thetiming of which is still unclear. No consensus exists onthe timing of the peak pressure event in the NF com-plex, which ranges from the Early Eocene (Monie &Chopin, 19914 ) to as late as the Middle Miocene(15 Ma; Lopez Sanchez-Vizcaıno et al., 2001; De Jong,2003). In particular, the recently published extremelyhigh exhumation and cooling rates (12 km Myr)1,Lopez Sanchez-Vizcaıno et al., 2001), based on theassumption that these 15 Ma ages represent peakburial conditions, contrast with numerous other geo-chronological and stratigraphical studies (Monie &Chopin, 1991; De Jong et al., 1992; Platt et al., 2005).
In order to tackle such discrepancies, this studyprovides new metamorphic evolution, mineral chem-istry and thermobarometric constraints for samplesfrom the Calar Alto and Bedar-Macael units. Inaddition, in situ laser-ablation 40Ar/39Ar-dating radi-ochronology is undertaken on those successive gener-ations of phengite, the compositions of which andP–T–d history have been detailed.The absolute ages of the main metamorphic stages
are then discussed with respect to the closure tem-perature concept as well as exhumation rates. Thesedata are then combined with published low-tempera-ture fission track ages (Johnson et al., 19975 ) in order todraw a new P–T–d–t path for the NF complex.Implications in terms of tectonic and geodynamicprocesses involved in the exhumation and doming ofthe Betic Cordillera internal zones are then discussed.
GEOLOGY OF THE NF COMPLEX
Only the geology of the NF complex is detailed hereand the reader unfamiliar with the geology of the BeticCordillera is referred to recent publications (e.g. Vis-sers et al., 1995; Azanon & Crespo-Blanc, 2000;Martınez-Martınez et al., 2002; Puga et al., 20026 ; Plattet al., 2003).
The NF core complexes
The NF metamorphic complex (Egeler & Simon, 19697 )only crops within two tectonic windows in the core oflarge-scale antiformal structures (Fig. 1b,c; i.e. the�Sierra Nevada-Sierra de los Filabres� and to the south-east and the east, the �Sierra Alhamilla-Sierra Cabr-era�). The NF complex is separated from the overlyingAlpujarride units and from the associated sedimentarybasins by a set of major shear zones (see cross-section:Fig. 1d), namely the Mecina shear zone and the FSZthat were active sequentially (Martınez-Martınez et al.,2002).The NF complex is composed of three main units
(Garcıa-Duenas et al., 1988a,b; De Jong, 1991; Visserset al., 1995) which are, from bottom to top: the Ragua(i.e. ex Veleta, Martınez-Martınez et al., 2002), theCalar Alto and the Bedar-Macael units with respectivestructural thicknesses of 4000, 4500 and 600 m (Gar-cıa-Duenas et al., 1988a), the latter two correspondingto the so-called Mulhacen complex (see Martınez-Martınez et al., 2002). These three units present aroughly similar lithostratigraphic succession (as for theAlpujarride units) with a thick and monotonoussequence of presumably Palaeozoic dark schists(Lafuste & Pavillon, 1976) topped by light-colouredPermo-Triassic graphitic schists and quartzites (Nijhuis,1964; Platt et al., 1984) and Triassic carbonate rocks(Kozur et al., 1985). These units are separated bymajor (i.e. 500 m thick) ductile to ductile-brittle shearzones, hereafter noted Intra-Nevado-Filabride ShearZones (Garcıa-Duenas et al., 1988b8 ; De Jong, 1993;
2 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Fig. 1. Tectonic maps and location of the samples. (a) Location of the studied areas within the Gibraltar arc (inset) and theNevado-Filabride domes. (b–c) Position of the samples on the maps of the Eastern Sierra de los Filabres and the Sierra Alhamilla(modified after Augier et al., in press). The main D2 and D3 stretching direction are indicated. (d) Position of the samples along aschematic N-S cross section. Note that the relative structural location of the samples is also given across the vertical axis of thelegend. Key to symbols (used hereafter in other figures): circles and squares: samples from Calar Alto and Bedar-Macael units,respectively; empty symbols: samples only studied for thermobarometry; filled symbols: samples only studied for geochronology;stars: samples used for both purposes; small dots: other samples not detailed here.
EXHUMAT ION, DOMING AND SLAB RETREAT 3
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Gonzalez-Casado et al., 1995). The most completesection of the NF complex can be found in the Sierrade los Filabres where it is bounded by the FSZ(Fig. 1a,b).
Adjacent Neogene basins were mostly infilled fromthe Serravallian-Tortonian boundary (c. 11.6 Ma)to the Plio-Quaternary, with evidence of syn-tectonicinfill related to the exhumation of the NF complex(see below) from 12 to 8 Ma (e.g. Volk, 1967;Vissers et al., 1995; Barragan, 1997; Augier et al.,submitted).
Despite abundant stratigraphic markers in theNF complex (Nijhuis, 1964; Lafuste & Pavillon, 1976;Platt et al., 1984; Kozur et al., 1985; Tendero et al.,1993), the youngest stratigraphic constraints frommeta-sediments are Cretaceous (Tendero et al., 1993)and thus not very restrictive for the timing of themetamorphism (as already pointed out by Monie &Chopin, 1991).
Structural evolution of the NF complex
The detailed structural evolution of the NF complex,which is beyond the scope of the present paper, wasrecently investigated by Augier et al., in press in orderto relate the tectonic evolution of the NF complex andthe formation of adjacent basins. Only the maininformation is summarized here.
Very little is known about early deformation stagescoeval with thickening, rising pressure and tempera-ture and peak pressure conditions (D1; Vissers, 1981;Bakker et al., 1989). The first schistosity (S1) isrecognized towards the core of the NF units, andpreserved within isolated lenses protected from thelater deformation in higher structural level; in places,the relationships between the initial bedding (S0)and S1 can be observed in the hinges of F1 folds(Fig. 2).
In fact, the NF complex primarily shows a succes-sion of deformation phases (here labelled D2, D3 andD4) interpreted as a continuum of strain localizationduring exhumation with a progressive evolution fromductile to brittle regime.
D2 is characterized by the development, in most ofthe NF complex, of a generally gently dipping, planar-linear fabric (S2–L2), axial–planar to F2 folds. The S2foliation carries a strong and penetrative E–Wstretching lineation (L2) which is more intensetowards the major extensional contacts, in particularthe FSZ. Kinematic indicators (absent or rare in thecore of the complex) increase near the FSZ and theIntra-Nevado-Filabride Shear Zones, indicating aconsistent non-coaxial flow accompanied by the pro-gressive disappearance of S0 and S1 features. Thedirection and sense of shear consistently indicate anoverall top-to-the-west shear (Galindo-Zaldıvar et al.,1991; Jabaloy et al., 1993; Gonzalez-Casado et al.,1995; Martınez-Martınez & Azanon, 1997; Martınez-Martınez et al., 2002).
All previous structures, particularly in the highestpart of the NF complex, are affected by a late D3extensional cleavage. The finite strain and the degree ofnon-coaxiality increase towards the major shear zoneswhere D3 cleavage is highly penetrative and previousstructures are overprinted. Most importantly, a pro-gressive change in the shear direction and an outwardrotation of the stretching lineations towards the limbsof the Sierras are observed: top-to-the-west shear sen-ses, which are observed along the antiform axis, pro-gressively rotate towards the north on the northernlimb and the south on the southern limb (Fig. 1b,c).This pattern suggests that D3 extension is principallycontrolled by E–W crustal stretching coupled with N–Sextension because of gravitational processes inducedby the formation of domes.Brittle conditions (D4) point to an amplification of
this pattern leading to locally predominant lateralextension on dome limbs (i.e. N–S). This result isconfirmed by cooling ages which illustrate that thecores of domes were systematically exhumed beforetheir adjacent limb (as already pointed out byMartınez-Martınez et al., 2002), in addition to aprogressive younging of the fission tracks agestowards the west (Johnson et al., 1997). It should benoted that this time and space transition fromregional E–W to local N–S extension in the meta-morphic domes reconciles the history of ductiledeformation with the dominant N–S to NW–SEbrittle extension responsible for the formation ofmost of the Eastern Betic basins (Vissers et al., 1995;Martınez-Martınez & Azanon, 19979 ; Booth-Reaet al., 2003a,b, 2004).
Age constraints on the P–T evolution of the NF complex
No consensus exists on the timing of the peak pressureevent in the NF complex, which ranges from the EarlyEocene (48 Ma; Monie & Chopin, 1991) to as late asthe Middle Miocene (15 Ma; Lopez Sanchez-Vizcaınoet al., 2001; De Jong, 2003). High exhumation andcooling rates recently based on 15 Ma ages attributedto peak burial (D1) conditions (without accurate con-trol on the time of growth of the dated minerals)contrast with numerous other geochronological andstratigraphic data (Fig. 3). Amphibolite facies retro-gression coeval with the formation of the S2 foliation(D2) is only constrained (Monie & Chopin, 1991).Late exhumation stages are better constrained, as
several studies dated the greenschist facies retro-gression (De Jong, 1991; Monie & Chopin, 1991; Plattet al., 2005). Yet, although some of the 30–15 Ma agesmay correspond to D3 (e.g. the 17–16 Ma cluster;Fig. 3), the lack of reliable control of the texture andtime of growth of phengite prevents any definitiveinterpretation.The final exhumation stages (D4) are constrained by
fission tracks (FT) cooling ages (Johnson et al., 1997)on both zircon and apatite (closure temperature
4 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
around 250–290 �C and 60–110 �C, respectively; Hur-ford, 1990; Tagami & Shimada, 199610 ; Gunnell, 2000).Zircon FT ages (Johnson et al. 1997) show that coolingoccurred first in the east (Sierra de los Filabres) at theUpper Serravallian (13 Ma) and was completed11 by theUpper Tortonian in the west (9–8 Ma; Sierra Nevada).In the studied transect across the Sierra de los Filabres,the last extensional deformation increments took placealong the FSZ from 11.9 ± 0.9 Ma for zircon and8.9 ± 2.9 Ma for apatite (i.e. hereafter 12 and 9 Marespectively), with NF complex core ages systematic-ally older than those of the NF complex adjacentlimbs.
These results are consistent with the subsidencepulse in the sedimentary infill of neighbouring basins(i.e. Tabernas and Huercal-Overa basins) characterizedby disorganized red conglomerates (Mora, 1993; Vis-sers et al., 1995) carrying the first NF detritus, thoughtto be Upper-Serravallian to Serravallian-Tortonian
boundary (i.e. 12 Ma; Kleverlaan, 1989). Accurateconstraints for the above-mentioned stages are thusneeded in order to establish an internally consistentP–T–d–t tectonic model.
SAMPLING AND ANALYTICAL METHODS
Sample selection
Metapelite samples were selected from the presumably Permo-Triassic unit (Garcıa-Duenas et al., 1988b) of both the Bedar-Macael (BM) and the Calar Alto (CA) units to avoid inheritanceof mineral relics and/or Ar excess in phengite from the Hercynianmetamorphism recognized in the underlying Palaeozoic unit (Puga& Dıaz de Federico, 197612 ). Samples were selected in key outcropsproviding unambiguous deformational features (e.g. Fig. 2). Thinsections were cut in the XZ plane from oriented samples fromthese localities, where X and Z are the maximum and the mini-mum principal stretches respectively (i.e. to ensure a good tectoniccontrol). The location of the samples in the structural nappe stackis indicated in Fig. 1(b–d) (maps and cross-section).
Fig. 2. Three-dimensional sketches derived of field observation illustrating the outcrop-scale tectono-metamorphic evolution of theNevado-Filabride complex (modified after Augier et al., in press). Successive parageneses are closely associated with (macro-) textures(also visible at the thin-section scale). This evolution is separated into four main deformation stages labelled from D1 to D4, which isfrom peak burial conditions to the latest extensional deformation taking place under brittle conditions. Framed and unframedassemblages belong to the Bedar-Macael and Calar Alto units respectively.
EXHUMAT ION, DOMING AND SLAB RETREAT 5
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Microprobe and P–T estimates
Microprobe
Mineral analyses were performed with Camebax SX50 and SX100electron microprobes at University Paris VI and at the GranadaUniversity (15 kV, 10 nA, PAP13 correction procedure) using Fe2O3
(Fe), MnTiO3 (Mn, Ti), diopside (Mg, Si), CaF2 (F), orthoclase (Al,K), anorthite (Ca) and albite (Na) as standards.
P–T estimates
The major source of errors in P–T estimates stems from the equi-librium criteria used to select parageneses. We combined criteriasuch as the habit of minerals, their textural relationships, andmicro-structural location to select the minerals used in each multi-equilibrium calculation. The minerals used are involved in the samemicro-structural domain and in close contact, which are believed tohave crystallized at the same time. In parageneses involving garnet,minerals in the pressure shadows were assumed to be in equilibriumwith the rim composition. The program THERMOCALC was usedto apply an average P–T calculation (Powell & Holland, 1988;Holland & Powell, 1990, 1998) to assemblages that are interpreted tobe in textural equilibrium. THERMOCALC v3.21 calculations weretypically performed for low-variance stage 1 and stage 2 mineralassemblages (see below). TWEEQU 2.02 software was used for
high-variant mineral associations such as phengite, chlorite ± albite.The P–T results allowed constraints to be placed on the P–T pathsfor the two different units.
THERMOCALC thermobarometry calculations. Calcu-lations used the internally consistent thermodynamic dataset ofHolland & Powell (1998) and the program THERMOCALC v3.21(Holland & Powell, 1998). Calculations were made on metapeliticassemblages except for assemblages of the Bedar-Macael metaba-sites. Recalculation of the analysis, including the calculation of Fe3+
iron and mineral end-member activities was performed with theprogram AX, of Holland & Powell (ftp://www.esc.cam.ac.uk/pub/minp/AX/14 ).
Only P–T estimates satisfying the equilibrium test criteria (e.g.sigfit, hat; Holland & Powell, 1998) were considered in this study(and plotted onto Fig. 6). Accuracy on the P–T estimates, estimatedby the error ellipse parameters, is typically of the order 10–30 �C fortemperature and 1–2 kbar for pressure, except for the calculations onthe eclogitic association (stage 1) of the Bedar-Macael unit wherethey reach 50 �C and 3 kbar.
TWEEQU multiequilibrium thermobarometry. The multi-equilibrium approach (Berman, 1991; Vidal & Parra, 2000a,b) waschosen for deriving continuous P–T paths for rocks which includephengite–chlorite pairs because: (i) these minerals rather recrystallizethan change composition by lattice diffusion (especially at the lowtemperatures of blueschist and greenschist facies metamorphism) and(ii) a relative chronology of phyllosilicate growth can frequently be
Fig. 3. Compilation of the geochronologicaland stratigraphical data from the Nevado-Filabride complex. For each study, themethod, the mineral used and the presumeddated P–T domains are indicated in the le-gend. Data are from: (in black) this study,(1) Monie & Chopin (1991)43 , (2) Lopez San-chez-Vizcaıno et al. (2001)44 , (3) Platt et al. (inpress)45 , (4) De Jong et al. (1992), (5) Andri-essen et al. (1991)46 , (6) Johnson et al. (1997),(7) Montenat & Ott d’Estevou (1990); Bri-end et al. (1990)47 ; Mora, 1993; Vissers et al.(1995); Montenat & Ott d’Estevou (1999);Poisson et al. (1999), (8) Weijermars et al.(1985). Our results (filled squares) yield thefirst complete P–T–t history of the Nevado-Filabride complex.
6 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
determined using micro-structural criteria (Vidal & Parra, 2000a;Parra et al., 2002). In this study, this method was used only for low-pressure low-temperature characterization, where only phengite andchlorite record the P–T changes.
The P–T location of these reactions was calculated with TWEEQU2.02 software (Berman, 1991) and its associated database JUN92together with thermodynamic properties for Mg-amesite, Mg-sudoite, Mg-celadonite and chlorite and phengite solid-solutionmodels from Vidal et al. (1992, 1994, 1999, 2001), Vidal & Parra(2000) and Parra et al. (2001). The character and magnitude ofthese uncertainties have been discussed by Parra et al. (2001), Vidalet al. (2001) and Trotet et al. (2001). Following these authors, thetemperature (rT) and pressure (rP) scatter are calculated withINTERSX (Berman, 1991) and if rP >800 bar or rT>25 �C, theminerals are considered to be out of equilibrium and the P–Testimates are rejected.
Ar–Ar in situ dating
The 40Ar/39Ar in situ laser ablation technical procedure was firstproposed by Schaeffer et al. (1977), modified by Maluski & Monie(1988), and was recently detailed elsewhere (Agard et al., 2002). Werecall here the main stages for 40Ar/39Ar in situ sample preparationand analytical procedure.
The laser system consists of: (a) a continuous 6-W argon-ion laser,(b) a beam shutter for selection of lasering exposure time, withtypically 5-ms pulses separated by 40 ms and (c) a set of lenses forbeam focussing. The number of pulses depend on the nature of theanalysed mineral, its K-content and its presumed age. Argonextraction, purification and analyses are performed within threedistinctive parts with (d) the sample chamber where gas extraction isperformed, (e) the purification line with hot and nitrogen liquid(cold) traps and (f) a MAP 215–50 noble gas mass spectrometerequipped with an electron multiplier.
Rock sections of 1 mm thick, which had been used to make thepetrographic thin-sections, were double polished to c. 1 lm. Whole-section and detailed-area photographs of both the rock section andcorresponding thin section were taken for an accurate selection ofsuitable areas for laser experiments. All samples were ultrasonicallyrinsed in ethanol and distilled water, wrapped in pure aluminium foilsand then irradiated in the McMaster nuclear reactor (Canada)with several aliquots of the MMHb-1 international standard(520.4 ± 1.7 Ma; Samson & Alexander, 1987) standards. After irra-diation, both themonitors and the sectionswere placed on aCu-holderinside the sample chamber and heated for 48 h at 150–200 �C.
For each age determination, argon was extracted from a150 · 300 lm surface which always corresponds to a mixture ofseveral phengite grains taking into account the small size of thegrains. The crater is a 30–40 lm approximate hemisphere surroun-ded by a circular wall made of melted material. Incision of the sampledid not exceed 10–20 lm deep depending on the three-dimensionalorientation of the phengite crystals. Once the extraction was com-pleted, about 4 min were required for gas cleaning of the line and15 min for data acquisition by peak jumping from mass 40 to mass36 (eight runs).
For each experiment, ages have been obtained after correctionwith blanks, mass discrimination, radioactive decay of 37Ar and 36Arand irradiation-induced mass interferences. They are reported with1r uncertainty and were evaluated assuming an atmospheric com-position for the initially trapped argon [i.e. (40Ar/36Ar)i � 295.5].
MINERAL EVOLUTION
Crystallization-deformation relationships
In the study area, several successive parageneses sys-tematically relate to the main deformation stagesinferred from field data (Fig. 2). Table 1 gives adetailed paragenetic evolution of each NF unit during
the retrograde metamorphic evolution. Microphoto-graphs of representative mineral associations areshown in Fig. 4.
Representative analyses given in Table 2 [cation performula unit (c.p.f.u.)] all correspond to samples pre-sented in Fig. 4, so as to illustrate P–T results and later40Ar/39Ar dating (stars indicate where microprobeanalysis was performed). They represent turning pointsof both the Calar Alto and the Bedar-Macael P–Tpaths. Mineral abbreviations are after Kretz (1983)except for amphibole (Amph), omphacite (Omph) andphengite (Phg).
D1 stage
The eclogitic mineral association of the Bedar-Macael metabasites comprises garnet, omphacite,phengite (often rare and tiny) and rutile (Fig. 4a),located at the boundary of the magmatic grain, thetexture of which is still often recognizable (see alsoMortem et al., 1987; Puga et al., 2000a). In Fig. 4(a),garnet, omphacite, HP phengite (noted Phg1 onTable 1) and rutile are included inside a large D2-stage amphibole. In the Calar Alto unit, HPLTparagenesis corresponds to garnet, chloritoid,phengite and chlorite associated with kyanite andrutile (Fig. 4b; Table 1).
D2 stage
In Bedar-Macael metabasites, stage D2 corresponds tothe transformation of stage D1 paragenesis intoamphibole, plagioclase and titanite (i.e. from rutile,Fig. 4a). In the pelitic rocks, mineral associationscomprise staurolite, biotite, garnet, phengite ± kya-nite (Fig. 4c,d). These minerals are predominantlysyn-kinematic. Phengite (i.e. Phg2) forming the oftenvery-penetrative S2 foliation shows lower substitutionthan that in the previous stage, with Si values about3.15 c.p.f.u. Rutile in the matrix is partially replacedby titanite while still preserved in the garnet. The caseof sample BM3* (Fig. 4c) is particularly interesting, asthe D1 paragenesis is partly preserved inside the garnetwith Fe-chloritoid, while the matrix is mostly charac-terized by D2 minerals including biotite, staurolite andplagioclase. On the basis of textures, the followingthree successive parageneses, Grt-Cld-Phg-Chl-Ky,Grt-Phg-St-Bt ± Pl-Ky, and Grt-Phg-Bt-Chl-Ky wereconsidered in the calculations. Another example of theGrt-Phg-St-Bt ± Pl-Ky paragenesis is given by thecloser textural association of Fig. 4(d) (sample BM2*).Details of the mineral evolution for each sample aregiven in Table 1.
In the Calar Alto unit, the post-HPLT paragenesiscorresponds to a garnet overgrowth around the HP-LT garnet, together with chloritoid (in the matrix),phengite and chlorite (Table 1). A microphotograph ofthis paragenesis is shown in Fig. 4(e), where a new
EXHUMAT ION, DOMING AND SLAB RETREAT 7
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
generation of chloritoid underlines the S2 foliation. Alarger-scale view (Fig. 4f) demonstrates that garnetovergrowth occurred during the formation of thechloritoid-rich S2 foliation.
D3 stage
In the most deformed parts of the NF complex (forboth units), stage 3 corresponds to the crystalliza-tion of large amounts of chlorite, phengite (i.e.Phg3) ± albite. This paragenesis overprints and thusclearly post-dates stage-D2 parageneses. Figure 4(g)illustrates the neo-crystallization of phengite andchlorite along C3 shear bands, post-dating thechloritoid, chlorite and phengite S2 foliation.
D4 stage
Crystallization of D4 minerals, mainly chlorite andalbite, occurs at the vicinity of the main shear zones ofthe NF complex, mostly in quartz veins (V4). Althoughthese veins represent useful kinematic indicators of theductile-brittle to purely brittle stages, the P–T condi-tions for this late stage were not investigated and arenot discussed below.
Mineral composition
Table 2 lists representative analyses of the D1 to D3stages for both units. Each mineral of this table is
involved in one of the above-mentioned parageneses(stars: analytical spots on microphotographs presentedearlier; Fig. 4). Equilibrium P–T estimates derivedfrom these assemblages are given in Table 3 (see alsoFigs 6 & 7).Phengite (Phg) shows Si contents of 3.36 to c.
3.00 c.p.f.u (Table 2; e.g. Fig. 5b) with strong varia-tions from one sample to the other. Variable Si con-tents are generally interpreted in terms of Tschermaksubstitution alone (between the celadonite and mus-covite end members), which is favoured by an increaseof pressure (Velde, 1967; Massonne & Schreyer, 1987;Massonne, 1995). The Si contents are high in D1phengite and decrease in each sample during the ret-rograde deformation stages. Some Calar Alto meta-pelites contain phengite with a Si content around 3.40–3.35 c.p.f.u (i.e. greater than those shown in Table 2),but this phengite does not provide equilibrium HPLTP–T results: it is interpreted as a relic of progradestages (i.e. early D1). Figure 5(b) shows that Si contentvariations in sample BM3* are relevant to the presenceof a small amount (c. 10 mol.%) of pyrophyllitecomponent and deviate from the purely Tschermak-type substitution. The Si contents vary from3.27 c.p.f.u for S1 phengite preserved inside the garnetand in their adjacent pressure shadows to c.3.00 c.p.f.u for rosette-like phengite post-dating the S2foliation (e.g. Phg3; Fig. 4c). S2 foliation phengiteshows a continuous range of Si content between c. 3.17and c. 3.05 c.p.f.u (Fig. 5b), which, at least in places,
Table 1. List of successive parageneses for each sample. Mineral abbreviations are from Kretz (1983) except Amph: amphibole; Omph:omphacite; Phg: phengite.
BM3 Grt, Cld, Phg 1, Chl, Ky Grt, Phg2, St, Bt, Pl, Ky Grt, Phg2, Bt, Chl,Ky Qtz, Rt, Ttn, Ap, Rt, Cal
BM4 Grt, Omph, Phg1, Rt Amph, Ab, Ttn
Calar Alto Unit
CA1 Chl, Phg3 Qtz, Ab, Mt, Grt, Ep, Tur
CA2 Grt, Cld, Phg 2, Chl, Ky Qtz, Mt, Ep
CA3 Grt, Cld, Phg 2, Chl, Ky Qtz, Ep, Tur
CA4 Grt, Cld, Phg 1, Chl, Ky Qtz, Mt, Ep
CA5 Grt, Cld, Phg 1, Chl, Ky Qtz, Mt, Tur, Ap, Rt
CA6 Grt, Cld, Phg 1, Chl, Ky Qtz, Mt, Ep, Rt
Fig. 4. Microphotographs of representative textures and structures. Dots refer to microprobe analyses given in Table 2. (a) Partiallypreserved mafic eclogite (sample BM4) showing the garnet-omphacite-phengite-rutile paragenesis within a retrograde amphibolitematrix. (b) High-pressure assemblage partially preserved as rutile, chloritoid and phengite inclusions in garnet (sample CA5*). (c)Typical example of the progressive record of P–T conditions in some metapelites (sample BM3*): inclusions in garnet comprisechloritoid, rutile, phengite which yield HP conditions (together with kyanite relics in the matrix), while the assemblage staurolite-biotite-plagioclase later developed in the matrix as well as successive phengite generations (corresponding P–T estimates are given inTable 3). See also Fig. 5a for garnet, phengite and chlorite chemistry. (d) Late staurolite-garnet-biotite-bearing S2 foliation (sampleBM2*). (e) Chlorite-chloritoid-phengite-bearing S2 foliation deformed by chlorite-phengite ± albite-bearing C3 shear bands. The relicS2 paragenesis yields equilibrium conditions with the rim of the garnet porphyroblast shown in (f) (sample CA2*). (f) Relic garnetporphyroblast showing a clear syn-S2, post-HP overgrowth (while the core is underlined by the presence of many inclusions; sampleCA2*), the zonation of which is given in Fig. 5a. (g) Close-up view of a post-S2 C3 shear band underlined by chlorite and phengite.Successive recrystallizations and decreasing P–T estimates from 3–4 kbar/550 �C to 1–2 kbar/350 �C suggest that this shear bandapparently recorded the whole of the D3 cooling path (sample CA1). See text for details and Table 1 for a detailed list of mineralparageneses.
8 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
COLOUR
FIG
.
EXHUMAT ION, DOMING AND SLAB RETREAT 9
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
corresponds texturally to successive neo-crystallizationof phengite during the formation and development ofthe S2 foliation (Fig. 4c). This suggests that during theP–T evolution, equilibrium is maintained by the cry-stallization of new phengite grains of different com-position, as suggested by Vidal & Parra (2000), ratherthan by the progressive reequilibration of older grains.Phengite with different compositions, thereby reflectsdifferent P–T conditions, and were selectively analysedby laser-probe in situ age dating to provide absoluteradiometric ages of fabric elements.
According to Vidal & Parra (2000), variations in thechlorite (Chl) compositions can be explained in termsof: (i) FeMg
)1 substitution between the daphnite(Daph: Fe2þ5 Al2Si3O10(OH)4) and clinochlore (Clin:Mg5Al2Si3O10(OH)4 end members, (ii) Tschermak
substitution (Al2R2þ�1Si)1: TK) between clinochlore/
daphnite and amesite [Am: (Fe,Mg)4Al4Si2O10(OH)4],and (iii) di-trioctahedral substitution (Al2R
2þ�3: DT)
between daphnite/clinochlore and sudoite [Sud:(Fe,Mg)2Al4Si3O10(OH)4]. Most of the chlorite com-positions of the studied samples plot along a line cor-responding to the TK substitution with amesitecontents between 20 and 60 mol.% (e.g. Fig. 5d forsample BM3*). Sudoite content varies between c. 0 and20 mol.% (e.g. Fig. 5b). As for phengite, a clear trendis visible in the XMg v. Si contents, which underlinesprogressive changes during the retrograde evolution.Garnet (Grt) is generally Fe-rich and shows, in
Calar Alto samples, a chemical zoning characterizedby a depletion in Ca and Mn and an enrichment in Mgand Fe towards the rims (Fig. 5a,b). Core–rim com-
Table 2. Representative microprobe analyses of major index minerals from the Calar Alto and Bedar-Macael units. Same mineralabbreviations as for Table 1.
positions are XPyp ¼ 0.03–0.05; XAlm ¼ 0.63–0.82;XSps ¼ 0.06–0.07; XGrs ¼ 0.28–0.07 in the pelitic rocksof the Calar Alto unit. In the Bedar-Macael unit, core–rim compositions are XPyp ¼ 0.15–0.13; XAlm ¼ 0.72–0.60; XSps ¼ 0.02–0.01; XGrs ¼ 0.11–0.06 for themetapelites. Garnet is even more homogenous in themetabasites and typical compositions (core–rim) areXPyp ¼ 0.10–0.09; XAlm ¼ 0.62–0.59; XSps ¼ 0.02–0.01; XGrs ¼ 0.26–0.21.
Chloritoid (Cld) is always Fe rich and devoid ofchemical zoning. XMg for D1-stage chloritoid is around0.17–0.14 in the Bedar-Macael, and 0.32–0.23 in theCalar Alto unit. Later, D2-stage chloritoid (for CalarAlto) shows XMg values around 0.25–0.21.
Biotite, staurolite, omphacite and plagioclase showonly minor compositional variations from one thin-section to the other. Representative analyses are givenon Table 2.
P–T–T RESULTS AND DISCUSSION
P–T results
Averaged P–T estimates and associated uncertaintiesfor the D1 to D3 stages are presented in Fig. 6 forCalar Alto (CA; white symbols) and Bedar-Macaelunits (BM; black symbols). For the sake of clarity,only some of the P–T points obtained are shown inFig. 6, but the shaded area indicates the full scatter ofthe P–T estimates for each deformation stage (italici-zed numbers give the total number of such P–T esti-mates).
The eclogitic association of the Bedar-Macaelmetabasites (sample BM4) consistently yields higherP–T results than any other sample (Fig. 6; see alsoFig. 4a & Table 2 for the corresponding texture, min-eral compositions and detailed P–T results). Peakconditions for Calar Alto unit are lower, of the orderof 14 kbar/550 �C (obtained with the HP mineral Cld-Phg-Ru assemblage preserved inside the garnet ofCA5*; Fig. 4b).
The continuous P–T record exemplified by the pro-gressive paragenetic change in sample BM3* (Fig. 4c)yields the following estimates (Fig. 6; see Table 2 for
the two first steps): c. 10.6 kbar/565 �C for Grt-Cld-Phg-Chl-Ky, c. 7.2 kbar/601 �C for Grt-Phg-St-Bt ± Pl-Ky from the matrix, and c. 5.1 kbar/560 �C Grt-Phg-Bt-Chl-Ky. These P–T estimateseffectively provide a large segment of the P–T path(Fig. 6). A similar example is given by sample CA4*(Fig. 6).
Final retrogression through the greenschists facies isillustrated by the crystallization of closely associatedChl-Phg ± Ab in D3 shear bands (C3) both in CalarAlto (Fig. 4g; Table 2) and Bedar-Macael, whose P–Tresults (derived from TWEEQU software) indicate anc. 200 �C cooling from a pressure of the order of3–4 kbar down to 1 kbar for some 350 �C.
Combining the P–T results from D1, D2 and D3assemblages allows these fragmentary constraints to beput on a single composite P–T path for each unit of theNF complex (Fig. 7). Relative P–T results for CA andBM can be compared with a good precision becausethe same thermobarometric method was used. It is alsoshown that THERMOCALC (D1 & D2) andTWEEQU (D3) methods yield estimates which line upalong a fairly continuous path.
The two P–T paths show a similar clockwise tra-jectory (a) into the eclogite facies (18–20 kbar/550–650 �C) for the Bedar-Macael unit and (b) the lowereclogite facies (14 kbar/550 �C) for the Calar Altounit. Both units were buried at a somewhat differentdepth along a roughly similar gradient of the order of11–14 �C km)1. This HPLT event is followed, for bothunits, by an isothermal decompression to a pressure aslow as 3–4 kbar, a result in line with previous estimatesfor the Calar Alto unit (Gomez-Pugnaire & Soler,1987; Jabaloy et al., 1993). Rocks were finallyexhumed along a HTLP gradient of the order of60 �C km)1.
Age data and interpretations
Results are shown in Fig. 9a and complete results aregiven in Table 4; examples of representative texturesare also given in Fig. 8. The data show a large range ofapparent ages from c. 44 Ma for sample CA5* toc. 10 Ma for sample BM7. There are many features
Table 3. Representative parageneses made by some mineral associations from the Table 2 drawing the P–T framework for both CalarAlto and Bedar-Macael units. Numbers of the minerals are those given Table 2 with the same mineral abbreviations as for Table 1.
Sample Paragenesis P P T T Picture (Fig. 4)
Bedar-Macael Unit
BM1 Chl29, Phg9 1.5 0.8 419 14
BM1 Chl30, Phg10 2.9 0.4 561 7
BM2* Grt 14, Phg4, Bt22, Chl24, Ky 5.1 2.2 560 18 d
CA5* Grt15, Cld19, Phg5, Chl25, Ky 13.0 2.5 557 12 b
EXHUMAT ION, DOMING AND SLAB RETREAT 11
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
that can explain this age distribution. First, the com-plexity of the P–T paths recorded by the NF complexis responsible for the crystallization of more than onegeneration of phengite in the majority of rocks, givingrise to the possibility of mixed and meaningless ages.Secondly, the spatial resolution of the laser experi-ments does not allow an absolute separation of thevarious phengite generations under the camera used toselect the ablation zones on the thick sections. Thirdly,the existence of high-diffusivity argon pathways insome phengite (such as kink-bands) or the interactionwith fluids can cause age variations. Finally, it must beremembered that the ages reported in this study are
apparent ages calculated with an atmospheric ratio forinitial argon, thus discarding possible effects of argonloss or excess argon. Such effects are known to repre-sent frequent problems in argon geochronology thatcan be partially circumvented using 40Ar/39Ar laser-probe dating (e.g. Agard et al., 2002; Maurel et al.,2003; Mulch & Cosca, 2004).However, a straightforward yet important conclu-
sion from Fig. 9a is that the successive phengite gen-erations recognized on the basis of textures (e.g.Fig. 8), compositions and P–T estimates (e.g. Figs 3 &6) effectively yield successive ages. Results obtained forS1 phengite preserved inside isolated lenses or zones of
Fig. 5. (a) Element maps (Fe, Mn, Mg, Ca) showing core to rim garnet zoning in sample CA2* with an increase of Fe and Mg towardsthe rim and correlative decrease in Ca and Mn. The corresponding garnet profile is shown to the right of the maps. (b) Chemicalvariations of phengite, chlorite and garnet in sample BM2*.
12 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
crenulation cleavage in the deeper but less deformedpart of the Calar Alto unit (samples CA5* & CA8; e.g.Fig. 8c) show a large age scatter from 44 down to22 Ma, whereas ages obtained for the S2 foliation(samples CA2*, CA4*, CA7, CA8, CA9, BM2*,BM3*, BM5, BM6) are very consistent with anunweighted mean on 33 spots of 19.3 Ma (Figs 8b &9a). Results for C3 phengite cluster at around17–16 Ma (see Fig. 9a: samples CA2*, CA7, CA9,BM2*, BM3*, BM5, BM7 and Fig. 8a for the texture).The significance of these ages relies on our ability tomake a distinction between cooling ages, recrystalli-zation or neo-crystallization ages and meaningless agescaused by argon loss or excess argon.
At high temperature, it is generally suggested thatthe closure of phengite for argon is controlled by a
volume-diffusion mechanism. According to the closuretemperature concept (Dodson, 1973), radiometric agesrepresent the time elapsed since the cooling throughthe closure temperature. Many authors assume that theclosure temperature of isotopic diffusion for phengitevaries in the narrow range of 350–430 �C, dependingon cooling rate or grain size (Hames & Browring, 1994;Kirschner et al., 199615 ; Hames & Cheney, 1997; Villa,1998). For the temperature path followed by the NFrocks, the temperature concept thus predicts that all S1and S2 (and at least some of the C3) phengite shouldyield the same age. Yet this is not the case. On thecontrary, the correlation of in situ 40Ar/39Ar ages withphengite of distinct compositions (XMg, Tchermaksubstitution and, whenever available, P–T conditions)reveals that ages are texturally controlled and therefore
Fig. 6. P–T results and inferred P–T path segments. For the sake of clarity, only some of the P–T points and related error barsare shown; the area in grey corresponds to the envelope comprising all calculation results and uncertainties (numbers refer to thenumber of calculations). Errors brackets are based on the 1r uncertainties on P and T. Results are presented, from bottom totop, according to the main deformation stages (this presentation actually also respects their relative position in the structural pile; seelegend of Fig. 1).
EXHUMAT ION, DOMING AND SLAB RETREAT 13
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
independent of closure temperature. These observa-tions suggest that it is very likely that the 40Ar/39Arphengite ages reported in this study closely approachthe crystallization age of the different phengite popu-lations at conditions well above their commonlyaccepted closure temperature. This resistance ofphengite to argon resetting has been highlighted byseveral recent studies (e.g. Di Vincenzo et al., 2001;Agard et al., 2002; Maurel et al., 2003).
Exceptions to the closure temperature rule have of-ten been interpreted as diagnostic of excess argonincorporation (e.g. for older ages; De Jong et al., 2001,for the Betics) or late re-opening of the isotopic systemby a later thermal event (e.g. for younger ages;hydrothermal, magmatic or metamorphic re-heating).In the Alps however, several studies (Chopin & Mal-uski, 1980; Scaillet et al., 1992; Dahl, 1996; Scaillet,1998; in situ dating: Muller et al., 2001; Agard et al.,2002; Muller, 2003) have demonstrated that many agesrepresent neo- and recrystallization ages rather thancooling ages, because of the complexity of controllingfactors on argon diffusion (i.e. time of growth v.metamorphic evolution, composition or grain size,cooling rate, pressure, fluids or deformation).
In our samples, excess argon could be responsiblefor the old, relatively isolated ages around 44 Mareported in sample CA5* for S1 phengite (Fig. 9). Bycontrast, age as young as 10 Ma obtained on sample
BM7 can reflect some grain-size effect on argon accu-mulation in C3 phengite or the presence of lattice de-fects that could have facilitated argon diffusion. Theseage variations are principally observed for S1 and C3phengite. In the case of C3 phengite, Figs 8(a) and 9(b)reveal a strong textural control on their age; youngerages are encountered close to microscopic-scale C3shear bands. Away from the shear bands, typical S2(D2) ages are found. Such textural evidence accountingfor the scatter of ages is much more limited for S1phengite (Fig. 8c). Ages range mainly between 30 and22–18 Ma, with the younger ages approaching D2deformation ages.Overall, it is noteworthy that samples with D3
deformation (Fig. 9) show a clustering around 22–18and 14 Ma. The former age clearly corresponds to agesfound for D2 deformation (i.e. 22–18 Ma), whereasthe latter age could correspond to the last mineralrecrystallization (i.e. c. 14 Ma), after crossing theductile-brittle transition at about 350–300 �C andtherefore defining the lower bound of the presumedclosure temperature of phengite (Hames & Browring,1994; Hames & Cheney, 1997; Villa, 1998). The17–16 Ma ages found for the Sierra de los Filabres andSierra Alhamilla mylonites (Monie & Chopin, 1991 andPlatt et al., 2005 respectively) probably correspond to amixture of these two �end-member� ages, as only mineralpopulations have been analysed in these two studies.
Fig. 7. Composite P–T path for the Calar Alto and Bedar-Macael units, as inferred from the detailed estimates given in Fig. 6. Samplename and approximate equilibrium P–T conditions of the phengite generations considered in the radiochronological study areindicated (shaded areas). See text for details.
14 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Table 4. Results of 40Ar/39Ar radiometric data. Isotopic ratios and associated errors are presented together with the amount ofatmospheric argon (% atm).
These results suggest that recrystallization system-atics in the NF complex is mainly dominated byrecrystallization processes rather than cooling: thecoexistence, at the scale of a few microns, of different
phengite generations of contrasting compositions andages demonstrate that phengite did recrystallize underdifferent P–T conditions rather than being completelyreset. We therefore interpret D3 ages as the age of
Fig. 8. Three examples of the rock stubs used for in situ laser-probe 40Ar/39Ar radiochronology illustrating textures typical of C3(i.e. D3, a), penetrative S2 (i.e. D2, b) and S1–S2 (i.e. D1–D2; c) relationships. White overlays show surface areas from which argonwas extracted: numbers represent the obtained ages. Scale bars represent a millimetre. (a) Example of the close correspondence betweenthe irradiated/dated stub and the thin-section microphotograph (sample CA7), illustrating our approach to ensure a good texturalcontrol on phengite. Phengite crystallized along the S2 foliation and C3 shear bands. Age results reveal a younging of S2 phengite,which partly recrystallized at the vicinity of the C3 shear bands. (b) Stub from sample BM5 showing a penetrative S2 foliationyielding ages within the range 22–18 Ma plus a younger age attributed to a later recrystallization of phengite (during D3?). (c) Stubfrom sample CA8 showing the relics of a crenulated S1 foliation within the S2 matrix foliation (also note the pressure shadowsaround garnet). Age results reveal a cluster of S2 ages around 22–18 Ma, while S1 phengite partly recrystallized but retained olderages (around 30 Ma).
COLOUR
FIG
.
16 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
formation of new C3 phengite together with the par-tial, deformation-controlled reequilibration of S2phengite. On the contrary, D1 ages would correspondto the temperature-controlled progressive reequilibra-tion of S1 phengite (and/or to the existence of inheritedexcess argon) after its formation and until the D2deformation, which is more or less along the isother-mal part of the P–T path. Conversely, the cluster ofages for D2 (i.e. 22–18 Ma) probably reflects thecoincidence of the peak temperature with the end ofD2 deformation.
Time constraints, cooling and exhumation rates for the NFcomplex
The above discussion shows that texturally controlledin situ dating has shown that phengite generationsfrom distinct deformation events have specific distinctcrystallization ages (the compositions and P–T condi-tions of which were determined earlier). We thus pro-pose that the minimum age for the HP event in theCalar Alto unit, characterized by the higher celadonitecontent S1 phengite, took place at c. 30 Ma and in anycase before 20 Ma. Our study thus proposes new ��old��
ages for the burial age of the NF complex, similar tothose previously reported on amphibole (c. 48 Ma;Monie & Chopin, 1991). The mafic Bedar-Macael
eclogites were not dated however, and the significanceof these rocks remains uncertain.
In the light of the recrystallization processes evi-denced above, it is proposed that the end of thedominant D2 extensional deformation took place at22–18 Ma, and that the end of D3 deformation tookplace at c. 14 Ma (Fig. 9a). These 14 Ma ages corres-pond to the last phengite crystallization (C3 phengiteand re-equilibration of the S2 phengite) and are as-sumed to mark the crossing of the ductile-brittleboundary. They agree well with recent, well-con-strained fission track ages of 12 Ma for zircon and9 Ma for apatite (Johnson et al., 1997). By comparisonwith previous studies, our results yield the first com-plete P–T–t history of the NF complex. These resultsare presented in a composite P–T diagram for the NFcomplex (Fig. 10a) and plotted in T–t and P–t dia-grams (Fig. 10b,c), in order to estimate cooling andexhumation rates of both units. These new radiometricconstraints can be compared with previous studies (seeFig. 3), and suggest that the claim of a recent HPLTevent for the NF complex at 15 Ma (Lopez Sanchez-Vizcaıno et al., 2001) is unlikely.
Both units follow the same P–T path from D2onwards, but the Calar Alto unit exhumation occurredin two very distinctive steps (see Fig. 10). The firststep, D2, corresponds to isothermal decompression at
Fig. 9. (a) Compilation of the age results obtained in this study displayed by sample. The a priori tectonic constraints derived fromfield and thin-section observations are indicated below each column. To facilitate the comparison between the samples, they areordered so that samples progressively yield younger ages to the right. Horizontal shaded bands correspond, from bottom to top, to theinferred age for HP metamorphism, to the end of D2 deformation stage and to the end of D3 deformation stage respectively. See textfor details. (a) Age constraints from fission-track data (zircon and apatite; Johnson et al., 1997). (b) Stratigraphic constraints for theearliest occurrence of Nevado-Filabride pebbles in adjacent Eastern Betic basins and the earliest occurrence of post-extensionalsediments (arrow). (b) Example of the deformation-controlled recrystallization of phengite during D3 deformation stage (sample CA9):ages clearly decrease towards C3 shear bands.
COLOUR
FIG
.
EXHUMAT ION, DOMING AND SLAB RETREAT 17
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
c. 550 �C. It is followed by a second exhumation stageduring which the complex underwent a relative fast(from 20 to c. 9 Ma) and constant cooling of40–45 �C Myr)1 through the greenschists facies to thesurface (Fig. 10b). Such estimates for cooling are notparticularly high with respect to the cooling rates of200–350 �C Myr)1 proposed for the Alpujarridecomplex (Zeck et al., 1989, 1992, 1998; Monie et al.,1994; Sanchez Rodrıguez & Gebauer, 2000), whichsuggests that different cooling mechanisms prevailed.Our data also contrast with the 80 �C Myr)1 coolingrate of Lopez Sanchez-Vizcaıno et al. (2001)16 andDe Jong (2003) associated with a 12 km Myr)1 exhu-mation rate.
Exhumation rate estimates are of the order of2.8 km Myr)1 for the first part of the exhumation pathand fall to 0.6 km Myr)1 from the end of D2 onwards(Fig. 10c). Such contrasted and decreasing exhumationrates have already been reported from a variety ofgeodynamic contexts (Andersen & Jamtveit, 1990;Duchene et al., 1997; De Sigoyer et al., 2000; Brunet
et al., 2001; Agard et al., 2002). This steep decreasesuggests important changes in mechanisms responsiblefor the exhumation. Interestingly, although finalexhumation rates are comparable with erosion rates,which are typically <0.5 km Myr)1 (Ahnert, 1970;Pinet & Souriau, 1988; Ring et al., 1999), field obser-vations pertaining to the formation of extensionalbasins show that it occurred in a highly active exten-sional tectonic setting.
Geodynamic implications
Doming of the NF complex and basin infill
The origin of the NF dome has recently been inter-preted as the result of the combination of the large-scale folding taking place at the rear of a progressivelywestward migrating extensional front, as a conse-quence of isostasic readjustment of the extensionaldetachment, intra-crustal flow and orthogonal N–Scompression (Martınez-Martınez et al., 2002, 2004).
Fig. 10. (a) P–T–t path for the Calar Alto and Bedar-Macael units deduced from the thermobarometric and radiometric results of thisstudy. (b) Cooling history (T–t diagram) of the Calar Alto and Bedar-Macael units underlining the abrupt change of cooling rates takeplace at 19.3 Ma. Later, D3 exhumation takes place along a 60 �C km)1 gradient at 40–45 �C Myr)1. (c) Exhumation rates (P–tdiagram) for the Calar Alto and Bedar-Macael units: initial D2 exhumation velocities of the order of 2.8 mm year)1 decrease to0.6 mm year)1 during D3. (d) Close-up view of the final part of the P-t diagram showing the correlation between the final exhumationof the Nevado-Filabride complex and the subsidence curves of adjacent sedimentary basins (Huercal-Overa, Tabernas: see Fig. 1 forlocation).
18 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
This model, however, does not account for the pro-gressive rotation of extension directions between D2and D3 (Augier et al., in press; Fig. 1b,c), which likelyresults from the acquisition of a domal geometry andsuggests that the dome already existed under green-schist facies conditions (i.e. 18 Ma, at least). Neitherdoes it explain the kinematic changes required toaccount for the contemporaneous formation of theHuercal-Overa and Tabernas basins during D4.
Although the origin of doming remains to beexplained, the present study places constraints on thetiming of acquisition of the domal geometry. The mainexhumation stage took place between 30 and c. 20 Maand brought back the NF units from depths of at least40–45 to 9–12 km (Fig. 10a). The last mineralre-equilibrations characterizing the preserved S2 phengite(D2) took place between 22 and 18 Ma, for both units,while D3 ages scatter from 18 to 14 Ma.
As discussed above, near-surface cooling of themetamorphic rocks (<290 �C) occurred during theUpper Serravallian to Tortonian period (Johnsonet al., 1997). This period also corresponds to the firstinfill of the adjacent eastern Betic sedimentary basinsby continental coarse-grained sediment from the NFmetamorphic rocks (Fig. 10d). Basin subsidence curves(Fig. 10d) point to an increase in subsidence rates until8 Ma, at the time when the overall tectonic regimechanges from extension to compression across theNF domes. Eastern sedimentary basins therefore onlyrecord the very end of the exhumation of the NFcomplex, from 12 to 8 Ma. Although processes exhu-ming the NF complex at depth were active from 30 Maonwards, only few relics of the sedimentary basinslikely to have formed before 12 Ma are preserved(Fig. 10d).
Implications for the Betic nappe stack
The P–T–d–t evolution of the NF complex demon-strates that the main E–W, amphibolite faciesdeformation (end of D2) took place towards the endof the period 30–22 Ma, with age constraints clus-tering near 22–18 Ma (Fig. 9a). During that period,the Alpujarride complex was exhumed from depthsaround c. 35 km (e.g. Azanon & Goffe, 1997) to thesurface (FT data on apatite clusters around 18 Ma(Zeck et al., 1989, 1992, 1998, 2000; Monie et al.,1994; Platt et al., 1996). These almost perfectly coe-val exhumations point to very intriguing processes atdepth as the two complexes also show perfectlyorthogonal exhumation directions (top-to-the-northfor the Alpujarrides; Garcıa-Duenas et al., 1992;Jabaloy et al., 1993; Crespo-Blanc et al., 1994; Cre-spo-Blanc, 1995; top-to-the-west for the Nevado-Filabrides)! However, apatite fission tracks revealthat the Alpujarrides reached the surface (c. T < 60–110 �C) at 18 Ma, whereas the Nevado-Filabridesonly did so at 11–8 Ma (e.g. 9 Ma, Johnson et al.,1997). The NF complex thus only represented a core
complex with respect to the Alpujarrides from theperiod 18 to 9 Ma.
The NF core complex and slab retreat
The formation of domes parallel to the extensiondirection (type-a domes of Jolivet et al., 2004), such asthe NF complex, has been explained so far by variousmodels. For example, they have been interpreted as theresult of constrictional extension bounded by perpen-dicular compression (Hartz et al., 1994), or as an iso-stasic rebound caused by tectonic unroofing(Wernicke, 1992; Axen et al., 1995; Avigad et al.,1997).
In the Western Alpine Mediterranean system, Neo-gene extensional tectonics triggered the development ofthinned continental crust (such as the Alboran Sea;Fig. 11a) on the concave side of tight orogenic arcs (inthis case the Betic-Rif arc). Tomographic imagesthrough to mantle depths have revealed a Tethyan slabrelic dipping eastwards below the Alboran Sea(Gutscher et al., 2002; Spakman & Wortel, 2004).Following the latter authors, the Oligo-Miocenesouthward slab retreat (resulting from the regional-scaletransition from frontal collision to back-arc extension)was split during the Miocene into two distinctivesegments rolling back towards the east (Calabrian activesubduction) and towards the west (Alboran Sea).
The main exhumation (D2 stage) of the NF complex(until c. 18 Ma; Figs 9a & 10a) therefore took placeafter the transition from frontal collision to back-arcextension. Back-arc extension first coincided with thesouthward slab roll-back until it became E–W from 22to 18 Ma (Gutscher et al., 2002; Jolivet et al., 2003;Spakman & Wortel, 2004). On the contrary, during thesecond exhumation stage of the NF complex (D3stage, from 18 to 9 Ma), the Alpujarride complex hadreached the surface and the movements across the FSZseparating the two complexes and the Intra Nevado-Filabride Shear Zones were constantly E–W andassociated with top-to-the-west shear senses (Garcıa-Duenas et al., 1992; Jabaloy et al., 1993; Gonzalez-Casado et al., 1995; Martınez-Martınez et al., 2002).Fission-track data also point to a westward youngingof the unroofing of the NF complex therefore illus-trating continuous E–W crustal stretching under brittleconditions.
It is therefore tempting to propose that the finalexhumation of the NF complex (i.e. the last c. 10 km)below the Alpujarride complex occurred as a conse-quence of the westward slab retreat in a back-arcextension setting. Following this hypothesis, the FSZwould have concentrated a part of the extensionaldeformation permitting the NF to exhume from 18 to9 Ma (Fig. 11b,c). Appearance of the D3 divergentstretching directions, as evidence for the formation anduplift of the domes at depth, implies that significantgravity forces controlled by the newly formed �slopes�of the domes were added to the overall E–W crustal
EXHUMAT ION, DOMING AND SLAB RETREAT 19
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
stretching. The situation then evolved under brittleconditions with an amplification of this pattern whilethe rocks completed their exhumation, leading to localpredominance of N–S extension in the eastern part ofthe NF complex from 12 to 8 Ma (Fig. 11c).
The duration of the extensional process is c. 20 Myrwhich is evidence in favour of progressive slab retreatfrom c. 30 to 9 Ma rather than instantaneous convectiveremoval at 20 Ma. The change in the shape of the P–Tpath at 22–18 Ma together with the localization of themain top-to-the-west shear zones suggest that this datecorresponds to a change in the direction of slab retreatfrom southwards to westwards and to the tearing of theslab suggested by several authors (Faccenna et al., 2004;Spakman & Wortel, 2004). This rather abrupt event,could explain the quite sudden surge of temperaturearound 20 Ma often used by advocates of convectiveremoval. This position could reconcile both approaches.
CONCLUSIONS
Here the results of an integrated pressure–tempera-ture–deformation–time (P–T–d–t) study on the two
uppermost (Calar Alto and Bedar-Macael) units of theNF complex and outline their bearing on the exhu-mation of the internal parts of the Betic Cordillera aresummarized.Peak burial conditions are 18–20 kbar/550–650 �C
for Bedar-Macael metabasites and of the order of14 kbar/550 �C for the Calar Alto unit. During theD2 deformation stage, both units followed a similarisothermal decompression path constrained by pro-gressive paragenetic changes. Final retrogressionthrough the greenschists facies is illustrated by cry-stallization closely associated with D3 shear bandsindicating an c. 200 �C cooling from a pressure ofthe order of 3–4 kbar down to 1 kbar for some350 �C. The final exhumation of the NF complex todepths corresponding to the ductile-brittle bound-ary thus took place along a HT-LP gradient of60 �C km)1.Texturally controlled in situ laser-probe 40Ar/39Ar
dating of phengite reveals that ages represent defor-mation-controlled recrystallization processes ratherthan being dependent on closure temperature. Wepropose that the minimum age for the HP event in the
Fig. 11. Sketch depicting a possible geodynamic setting of the exhumation of the Nevado-Filabride complex illustrating how,in our interpretation, the late D2 to D3 exhumation stage relates to the roll-back of the relic Neo-Tethyan slab below the AlboranSea. Box: location of (b,c); 3D sketches summarizing the time evolution of the NF domes. See text for details.
20 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Calar Alto unit took place at 30 Ma and in any casebefore 20 Ma. In the light of recrystallization proces-ses, the end of the dominant D2 extensional defor-mation likely took place at c. 22–18 Ma, and the end ofD3 deformation took place at c. 14 Ma.
The P–T–d–t evolution of the NF complex dem-onstrates that the end of the main exhumation (D2)of the NF units occurred at 22 and 18 Ma, andcoincided with an E–W crustal stretching partlyaccommodated with the top-to-the-west sense ofshear along the already active Filabres shear zone.Meanwhile, the overlying Alpujarride complex wasbeing exhumed from depths around c. 35 km to thesurface. During the second exhumation stage D3, thecomplex underwent a relative fast and constantcooling of 40–45 �C Myr)1 through the greenschistsfacies onto the surface (from 18 to c. 9 Ma). Exhu-mation rate estimates, of the order of 2.8 km Myr)1
for the first part of the exhumation path, fall to0.6 km Myr)1 from the end of D2 deformation on-wards. This steep decrease suggests important changesin the mechanism responsible for the exhumation.The NF complex thus represented a core complexwith respect to the Alpujarrides from the period 18 to9 Ma, the FSZ concentrating a significant part of theextensional deformation.
The present study shows that the inception ofdoming, witnessed by the progressive rotation ofextension directions between D2 and D3 (Augier et al.,in press), dates back to 18 to 14 Ma. The eastern Beticsedimentary basins, therefore only recorded the veryend of the exhumation of the NF complex, from12 Ma with the appearance of NF clasts, to 8 Ma.Although extensional processes exhuming the NFcomplex at depth were active from 30 Ma onwards,they have no significant surface expression preserved,at least before 12 Ma.
In the light of these new age constraints, we proposethat: (1) the main exhumation of the NF complex (D2deformation, until c. 18 Ma) took place after thetransition from frontal collision to back-arc extensionoccurred towards the end of the regional-scale south-ward slab roll-back from 30 to 22 Ma (Jolivet et al.,2003), (2) the final exhumation of the NF complexbelow the Alpujarride complex (i.e. the last 10 km,from 18 to 9 Ma) occurred as a consequence of theMiocene westward slab retreat revealed by seismictomography images (Spakman & Wortel, 2004). The c.20 Myr long duration of the exhumation process alsoargues in favour of progressive slab retreat from c. 30to 9 Ma rather than instantaneous convective removalat 20 Ma.
ACKNOWLEDGEMENTS
This work was supported by the CEPAGE and thecontribution of the UMR 7072 (CNRS). We gratefullyacknowledge J.P. Platt for a very nice and instructivefield trip in March, 2003.
REFERENCES
Agard, P., Monie, P., Jolivet, L. & Goffe, B., 2002. Exhumationof the Schistes Lustres complex: in situ laser probe 40Ar/39Arconstraints and implications for the Western Alps. Journal ofMetamorphic Geology, 20, 599–618.
Ahnert, F., 1970. Functional relationships between denudation,relief, and uplift in large mid-latitude drainage basins.American Journal of Science, 268, 243–263.
Aldaya, F., Alvarez, F., Galindo Zaldıvar, J., Gonzalez Lodeiro,F., Jabaloy, A. & Navarro Vila, F., 1991. The Malaguide-Alpujarride contact (Betic Cordilleras, Spain): a brittleextensional detachment. Comptes Rendus de l’Academie desSciences de Paris, 313 (Serie II), 1447–1453.17
Andersen, T. B. & Jamtveit, B., 1990. Uplift of deep crust duringorogenic extensional collapse: a model based on field studies inthe Sogn-Sunn-Fjord region of Western Norway. Tectonics, 9,1097–1111.
Andriessen, P. A. M., Hebeda, E. H., Simon, O. J. & Verschure,R. H., 1991. Tourmaline K-Ar ages compared to otherradiometric dating systems in Alpine anatectic leucosomes andmetamorphic rocks (Cyclades and Southern Spain). ChemicalGeology, 91, 33–48.
Augier, R., Jolivet, L. & Robin, C., in press. Late Orogenicdoming in the Eastern Betics: final exhumation of the Nevado-Filabride complex and its relation to basin genesis. Tectonics.18
Augier, R., Robin, C. & Jolivet, L., submitted. The Tabernasbasin: a new example of extensional tectonic in the EasternBetics (SE Spain). Bulletin de la Societe Geologique de France.19
Avigad, D., Garfunkel, Z., Jolivet, L. & Azanon, J. M., 1997.Back-arc extension and denudation of Mediterranean eclo-gites. Tectonics, 16, 924–941.
Axen, G., Bartley, J. & Selverstone, J., 1995. Structural expres-sion of a rolling hinge in the footwall of the Brenner Linenormal fault, eastern Alps. Tectonics, 14, 1380–1392.
Axen, G.J., Selverstone, J., Byrne, T. & Fletcher, J.M., 1998. Ifthe strong crust leads, will the weak crusts follow? GSA Today,8, 1–8.
Azanon, J. M. & Crespo-Blanc, A., 2000. Exhumation during acontinental collision inferred from the tectonometamorphicevolution of the Alpujarride Complex in the central Betics(Alboran Domain, SE Spain). Tectonics, 19, 549–565.
Azanon, J. M. & Goffe, B., 1997. Ferro-Magnesiocarpholite-kyanite assembleges as record of the high-pressure, low-tem-perature metamorphism in central Alpujarride units, Beticcordillera (SE Spain). European Journal of Mineralogy, 9,1035–1051.
Azanon, J. M., Garcıa Duenas, V., Martınez Martınez, J. M. &Crespo-Blanc, A., 1994. Alpujarride tectonic sheets in thecentral Betics and similar eastern allochthonous units (SESpain). Comptes Rendus de l’Academie des Sciences de Paris,318 (Serie II), 667–674.
Bakker, H. E., De Jong, K., Helmers, H. & Bierman, C., 1989.The geodynamic evolution of the Internal Zone of the BeticCordilleras (South-East Spain): a model based on structuralanalysis and geothermobarometry. Journal of MetamorphicGeology, 7, 359–381.
Barragan, G., 1997. Evolucion geodinamica de la depresion deVera. Doctoral Thesis, University of Granada, ?????????.20
Berman, R. G., 1988. Internally-consistent thermodynamic datafor minerals in the system Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-TiO2-H2O-CO2: representation, estimation, and hightemperature extrapolation. Journal of Petrology, 29, 445–522.21
Berman, R. G., 1991. Thermobarometry using multi-equilibriumcalculations: a new technique, with petrological applications.Canadian Mineralogist, 29, 833–855.
Booth-Rea, G., Azanon, J. M., Goffe, B., Vidal, O. & Martınez-Martınez, J. M., 2002. High-pressure, low-temperature meta-morphism in the Alpujarride units outcropping in southeasternBetics (Spain). Comptes Rendus de l’Academie des Sciences deParis, 334 (Serie II), 857–865.
EXHUMAT ION, DOMING AND SLAB RETREAT 21
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Booth-Rea, G., Azanon, J. M. & Martınez-Martınez, J. M.,2003a22 . Metamorfismo de A P/B T en metapelitas de la unidadde Ragua (complejo Nevado-Filabride, Beticas). Resultadostermobarometricos del estudio de equilibrios locales. Geoga-ceta, 34, 87–90.
Booth-Rea, G., Azanon, J. M., Martinez-Martinez, J. M., Vidal,F. & Garcia-Duenas, V., 2003b23 . Analysis estructural y evo-lution tectonometamorphica del basamento de las cuencasneogenas de Vera y Huercal-Overa, Beticas Orientales. Revistade la Societad Geologica de Espana, 16, 193–211.
Booth-Rea, G., Azanon, J. M. & Garcia-Duenas, V., 2004.Extensional tectonics in the north-eastern Betics (SE Spain):case study of the extension in a multilayered upper crust withcontrasting rheologies. Journal of Structural Geology, 26,2039–2058.
Brunet, C., Monie, P., Jolivet, L. & Cadet, J. P., 2001. Migrationof compression and extension in the Tyrrhenian Sea, insightsfrom 40Ar/39Ar ages on micas along a transect from Corsica toTuscany. Tectonophysics, 321, 127–155.
Calvert, A., Sandvol, E., Seber, D., et al., 2000. Geodynamicevolution of the lithosphere and upper mantle beneath theAlboran region of the western Mediterranean: constraintsfrom travel time tomography. Journal of GeophysicalResearch, 105, 10871–10898.
Chopin, C., 1984. Coesite and pure pyrope in high gradeblueschists of the Western Alps: a first record and some con-sequences. Contributions to Mineralogy and Petrology, 86,107–118.24
Chopin, C. & Maluski, H., 1980. 40Ar/39Ar dating of high-pressure metamorphic micas from the Gran Paradiso area(Western Alps): evidence against the blocking temperatureconcept. Contributions to Mineralogy and Petrology, 74, 109–122.
Crespo-Blanc, A., 1995. Interference pattern of extensional faultsystems: a case study of the Miocene rifting of the Alboranbasement (North of Sierra Nevada, Betic Chain). Journal ofStructural Geology, 17, 1559–1569.
Crespo-Blanc, A., Orozco, M. & Garcia-Duenas, V., 1994. Ex-tension versus compression during the Miocene tectonic evo-lution of the Betic chain. Late folding of normal fault system.Tectonics, 13, 78–88.
Dahl, P. S., 1996. The crystal-chemistry basis for Ar retention inmicas: inferences from interlayer partitioning and implicationsfor geochronology. Contributions to Mineralogy and Petrol-ogy, 123, 55–99.
De Jong, K., 1991. Tectono-metamorphic Studies and Radio-metric Dating in the Betic Cordilleras (SE Spain). DoctoralThesis, University of Amsterdam, ???????.25
De Jong, K., 1993. The tectono-metamorphic evolution of theVeleta Complex and the development of the contact with theMulhacen Complex (Betic Zone, SE Spain). Geologie enMijnbouw, 71, 227–237.
De Jong, K., 2003. Very fast exhumation of high-pressuremetamorphic rocks with excess 40Ar and inherited 87Sr, BeticCordilleras, Southern Spain. Lithos, 70, 91–110.
De Jong, K., Wijbrans, J. R. & Feraud, G., 1992. Repeatedthermal resetting of phengites in the Mulhacen Complex (BeticZone, South-eastern Spain) shown by 40Ar/39Ar step heatingand single grain laser probe dating. Earth and Planetary Sci-ence Letters, 110, 173–191.
De Jong, K., Feraud, G., Ruffet, G., Amouric, M. & Wijbrans,J. R., 2001. Excess argon incorporation in phengite of theMulhacen Complex: submicroscopic illitization and fluidingress during late Miocene extension in the Betic Zone,south-eastern Spain. Chemical Geology, 178, 159–195.
De Sigoyer, J., Chavagnac, V., Blichert-Toft, J. et al., 2000.Dating the Indian continental subduction and collisionthickening in the northwest Himalaya: multichronology of theTso Morari eclogites. Geology, 28, 487–490.
Di Vincenzo, G., Ghiribelli, B., Giogetti, G. & Palmeri, R., 2001.Evidence of a close link between petrology and isotoperecords: constraints from SEM, EMP, TEM and in situ
40Ar-39Ar laser analyses on multiple generations of whitemicas (Lanterman Range, Antarctica). Earth and PlanetaryScience Letters, 192, 389–405.
Dodson, M. H., 1973. Closure temperature in cooling geo-chronological and petrological systems. Contributions toMineralogy and Petrology, 40, 259–274.
Duchene, S., Lardeaux, J. M. & Albarede, F., 1997. Exhumationof eclogites: insights from depth-time analysis. Tectonophysics,280, 125–140.
Faccenna, C., Piromallo, C., Crespo-Blanc, A., Jolivet, L. &Rossetti, F., 2004. Lateral slab deformation and the origin ofthe Western Mediterranean arcs. Tectonics, 23, TC1012,doi:10.1029/2002TC001488.
Frey, M., Hunziker, J. C., Jager, E., Stern, W. B., 1983. Regionaldistribution of white K-mica polymorphs and their phengitecontent in the central Alps. Contributions to Mineralogy andPetrology, 83, 185–197.26
Galindo-Zaldıvar, J., Gonzalez-Lodeiro, F. & Jabaloy, A., 1989.Progressive extensional shear structures in a detachmentcontact in the Western Sierra Nevada (Betic Cordilleras,Spain). Geodinamica Acta, 3, 73–85.27
Galindo-Zaldıvar, J., Gonzalez-Lodeiro, F. & Jabaloy, A., 1991.Geometry and kinematic of post-Aquitanian brittle deforma-tion in the Alpujarride rocks and their relation with theAlpujarride/Nevado-Filabride contact. Geogaceta, 9, 30–33.
Garcıa-Duenas, V., Martınez-Martınez, J. M. & Navarro-Vila,F., 1986. La zona de cizalla de Torres Cartas, Conjunto deFallas normales de bajo angulo entre Nevado-Filabrides yAlpujarrides (Sierra Alhamilla, Beticas Orientales). Geogaceta,1, 17–19.28
Garcıa-Duenas, V., Martınez-Martınez, J. M., Orozco, M. &Soto, J., 1988a. Plis-nappes, cisillements syn- a post-meta-morphiques et cisaillements ductiles-fragiles en distensiondans les Nevado-Filabrides (Cordilleres betiques, Espagne).Comptes Rendus de l’Academie des Sciences de Paris, 307 (SerieII), 1389–1395.
Garcıa-Duenas, V., Martınez-Martınez, J. M. & Soto, J. I.,1988b. Los Nevado-Filabrides, una pila de pliegues mantosseparados por zonas de cizalla. II Congreso Geologico deEspana, Simposios, ??, 17–26.29
Garcıa-Duenas, V., Balanya, J. C. & Martınez-Martınez, J. M.,1992. Miocene extensional detachments in the outcroppingbasement of the Northern Alboran Basin (Betics) and theirtectonic implications. Geo-Marine Letters, 12, 88–95.
Goffe, B., Michard, A., Garcıa-Duenas, V., et al., 1989. Firstevidence of high-pressure, low-temperature metamorphism inthe Alpujarride nappes, Betic Cordillera (SE Spain). EuropeanJournal of Mineralogy, 1, 139–142.
Gomez-Pugnaire, M. T. & Soler, J. M., 1987. High-pressuremetamorphism in metabasite from the Betic Cordilleras(SE Spain) and its evolution during the Alpine orogeny.Contribution to Mineralogy and Petrology, 95, 231–244.
Gonzalez-Casado, J. M., Casquet, C., Martınez-Martınez, J. M.& Garcıa-Duenas, V., 1995. Retrograde evolution of quartzsegregations from the Dos Picos shear zone in the Nevado-Filabride Complex (Betic chains, Spain). Evidence from fluidinclusions and quartz c-axis fabrics. Geologische Rundschau,84, 175–186.
Gunnell, Y., 2000. Apatite fission track thermochronology: anoverview of its potential and limitations in geomorphology.Basin Research, 12, 115–132.
Gutscher, M. A., Malod, J., Rehault, J. P. et al., 2002. Evidencefor active subduction beneath Gibraltar. Geology, 30, 1071–1074.
Hames, W. E. & Browring, S. A., 1994. An empirical evaluationof the argon diffusion geometry in muscovite. Earth andPlanetary Science Letters, 124, 161–167.
Hames, W. E. & Cheney, J. T., 1997. On the retention of 40Ar*on the muscovite during reheating events. Geochimica andCosmochimica Acta, 68, 3863–3872.
Hartz, E., Andresen, A. & Andersen, T. B., 1994. Structuralobservations adjacent to a large-scale extensional detachment
22 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
zone in the hinterland of the Norwegian Caledonides. Tecto-nophysics, 231, 123–137.
Holland, T. J. B. & Powell, R., 1990. An enlarged and updatedinternal consistent dataset with uncertainties and correlations:the system K2O-Na2O-CaO-MgO-MnO-FeO-Fe2O3-Al2O3-TiO2-C-H2O-O2. Journal of Metamorphic Geology, 8, 89–124.
Holland, T. J. B. & Powell, R., 1998. An internally-consistentthermodynamic data set for phases of petrological interest.Journal of Metamorphic Geology, 16, 309–343.
Hurford, A. J., 1990. Standardization of fission track datingcalibration: recommendation by the Fission Track WorkingGroup of the IUGS Subcommission on Geochronology.Chemical Geology, 80, 171–178.
Jabaloy, A., Galindo-Zaldıvar, J. & Gonzalez-Lodeiro, F., 1993.The Alpujarride-Nevado-Filabride extensional shear zone,Betic Cordillera, SE Spain. Journal of Structural Geology, 15,555–569.
Jolivet, L., Goffe, B., Bousquet, R., Oberhansli, R. & Michard,A., 1998. The tectono-metamorphic signature of detachmentsin high pressure mountains belts, Tethyan examples. EarthPlanetary Science Letters, 160, 31–47.
Jolivet, L., Faccenna, C., Goffe, B., Burov, E. & Agard, P., 2003.Subduction tectonics and exhumation of high-pressure meta-morphic rocks in the Mediterranean orogens. AmericanJournal of Science, 303, 353–409.
Jolivet, L., Famin, V., Mehl, C. et al., 2004. Strain localizationduring crustal-scale boudinage to form extensional metamor-phic domes in the Aegean Sea. In: Gneiss Domes in Orogeny(eds Whitney, D., Teyssier, C. & Siddoway, C. S.), pp. 391.Special Paper, The Geological Society of America, ??????????.30
Kirschner, D., Hunziker, J. & Cosca, M., 1996. Closure tem-perature of argon in micas: A review and reevaluation basedon Alpine samples. GSA Abstracts w/ Program, 28, 441.
Kleverlaan, K., 1989. Neogene history of the Tabernas basin (SESpain) and its Tortonian submarine fan development. Geolo-gie en Mijnbouw, 68, 421–432.
Kozur, H., Mulder-Blanken, C. W. H. & Simon, O. J., 1985. Onthe Triassic of the Betic Cordilleras (S. Spain), with specialemphasis on holothurian sclerites. Proceedings of theKoninklijke Nederlandse Akademie van Wetenschappen, SerieB, 88, 83–110.
Kretz, R., 1983. Symbols of rock forming minerals. AmericanMineralogist, 68, 277–279.
Lafuste, M. L. J. & Pavillon, M. J., 1976. Mise en evidenced’Eifelien date au sein des terrains metamorphiques des zonesinternes des Cordilleres betiques. Interet de ce nouveau reperestratigraphique. Comptes Rendus de l’Academie des Sciences deParis, 283 (Serie II), 1015–1018.
Leoni, L., Sartori, F. & Tamponi, M., 1998. Compositionalvariation in K-white micas and chlorites coexisting inAl-saturated metapelites under late diagenetic to low grademetamorphic conditions (Internal Liguride Units, NorthernApennines, Italy). European Journal of Mineralogy, 10, 1321–1339.31
Lister, G. S., Banga, G. & Feenstra, A., 1984. Metamorphic corecomplexes of cordilleran type in the Cyclades, Aegean Sea,Greece. Geology, 12, 221–225.
Lonergan, L. & White, N., 1997. Origin of the Betic-Rifmountain belt. Tectonics, 16, 504–522.
Lopez Sanchez-Vizcaıno, V., Rubatto, D., Gomez-Pugnaire, M.T., Trommsdorff, V. & Muntener, O., 2001. Middle Miocenehigh-pressure metamorphism and fast exhumation of theNevado-Filabride complex, SE Spain. Terra Nova, 13, 327–332.
Maluski, H. & Monie, P., 1988. 40Ar/39Ar laser probe multi-dating inside single biotites of a Variscan orthogneiss (MassifCentral, France). Chemical Geology, 73, 245–263.
Martınez-Martınez, J. M. & Azanon, J. M., 1997. Mode ofextensional tectonics in the southeastern Betics (SE Spain).
Implications for the tectonic evolution of the peri-Alboranorogenic system. Tectonics, 16, 205–225.
Martınez-Martınez, J. M., Soto, J. I. & Balanya, J. C., 2002.Orthogonal folding of extensional detachments: structure andorigin of the Sierra Nevada elongated dome (Betics, SESpain). Tectonics, 21, DOI 10.1029/2001TC001283.
Martınez-Martınez, J. M., Soto, J. I. & Balanya, J. C., 2004.Elongated domes in extended orogens: A mode of mountainuplift in the Betics (Southeast Spain). In: Gneiss Domesin Orogeny (eds Whitney, D., Teyssier, C. & Siddoway, C. S.),pp. 391. Special Paper, The Geological Society of America,??????????.
Massonne, H. J., 1995. Experimental and petrogenetic study ofUHPM. In: Ultra High Pressure Metamorphism (eds Coleman,R. G. & Wang, X.), pp. 33–95. Cambridge University Press,Cambridge.
Massonne, H. J. & Schreyer, W., 1987. Phengite geobarometrybased on the limiting assemblage with K-feldspar, phlogopiteand quartz. Contributions to Mineralogy and Petrology, 96,214–224.
Maurel, O., Monie, P., Respaut, J.P., Leyreloup, A.F. &Maluski, H., 2003. Pre-metamorphic 40Ar/39Ar and U-Pb agesin HP metagranitoıds from the Hercynian belt (France).Chemical Geology, 193, 195–214.
Monie, P. & Chopin, C., 1991. 40Ar/39Ar dating in coesite-bearing and associated units of the Dora Maira massif, Wes-tern Alps. European Journal of Mineralogy, 3, 239–262.
Monie, P., Torres-Roldan, R. L. & Garcıa-Casco, A., 1994.Cooling and exhumation of the Wertern Betic Cordilleras,40Ar/39Ar thermochronological constraints on a collapsedterranes. Tectonophysics, 238, 353–379.
Montenat, C. & Ott d’Estevou, P., 1990. Eastern Betic Neogenebasins – a review. In: Les bassins neogenes du domaine betiqueorientale (Espagne) (ed. Montenat, C.), pp. 9–15. Documentset Travaux IGAL, ????????.32
Montenat, C. & Ott d’Estevou, P., 1999. The diversity of lateNeogene sedimentary basins generated by wrench faulting inthe Eastern Betics Cordillera, SE Spain. Journal of PetroleumGeology, 22, 61–80.
Mora, M., 1993. Tectonic and Sedimentary Analysis of theHuercal-Overa Region, SE Spain, Betic Cordillera. OxfordUniversity, Oxford.
Mortem, L., Bargossi, G. M., Martınez-Martınez, J. M., Puga,E. & Dıaz de Federico, A., 1987. Metagabbro and associatedeclogites in the Lubrın area, Nevado-Filabride Complex,Spain. Journal of Metamorphic Geology, 5, 155–174.
Mulch, A. & Cosca, M.A., 2004. Recrystallization or coolingages: in situ UV-laser 40Ar/39Ar geochronology of muscovitein mylonitic rocks. Journal of the Geological Society London,161, 573–582.
Muller, W., Kelley, S. & Villa, I. M., 2001. Dating fault-gener-ated pseudotachylytes: comparison of 40Ar/39Ar stepwise-heating, laser ablation and Rb-Sr microsampling analysis.Contributions to Mineralogy and Petrology, 144, 57–77.
Muller, W., 2003. Strengthening the link between geochrono-logy, textures and petrology. Earth and Planetary ScienceLetters, 206, 237–251.
Nijhuis, H. J., 1964. Plurifacial Alpine Metamorphism in theSouth-eastern Sierra de los Filabres, South of Lubrın, SESpain. Doctoral Thesis, University of Amsterdam, ????????.
Parra, T., Vidal, O. & Agard, P., 2001. A thermodynamicmodel for Fe-Mg dioctahedral K-white micas using datafrom phase equilibrium experiments and natural peliticassemblages. Contributions to Mineralogy and Petrology,143, 706–732.
Parra, T., Vidal, O. & Jolivet, L., 2002. Relation between theintensity of deformation and retrogression in blueschistmetapelites of Tinos Island (Greece) evidenced by chlorite-mica local equilibria. Lithos, 63, 41–66.
Pinet, P. & Souriau, M., 1988. Continental erosion and large-scale relief. Tectonics, 7, 563–582.
EXHUMAT ION, DOMING AND SLAB RETREAT 23
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Platt, J. P. & Behrmann, J. H., 1986. Structures and fabrics in acrustal-scale shear zone, Betic Cordilleras, SE Spain. Journalof Structural Geology, 5, 519–538.33
Platt, J. P. & Vissers, R. L. M., 1989. Extensional collapse ofthickened continental lithosphere: a working hypothesis forthe Alboran Sea and Gibraltar arc. Geology, 17, 540–543.
Platt, J. P., Behrmann, J. H., Martınez Martınez, J. M. &Vissers, R. L. M., 1984. A zone of mylonite and relatedductile deformation beneath the Alpujarride Nappe Complex,Betic Cordilleras, S. Spain. Geologische Rundschau, 73, 773–785.
Platt, J. P., Soto, J. I. & Comas, M. C., 1996. Decompressionand High-Temperature-Low-Pressure metamorphism in theexhumed floor of an extensional basin, Alboran-Sea, WesternMediterranean. Geology, 24, 447–450.
Platt, J. P., Soto, J. I., Whitehouse, M. J., Hurford, A. J. &Kelley, S. P., 1998. Thermal Evolution, Rate of Exhumation,and Tectonic Significance of Metamorphic Rocks from theFloor of the Alboran Extensional Basin, Western Mediterra-nean. Tectonics, 17, 671–689.
Platt, J. P., Allerton, S., Kirker, A. et al., 2003. The ultimate arc:differential displacement, oroclinal bending, and vertical axisrotation in the External Betic-Rif arc. Tectonics, 22,doi:10.1029/2001TC001321.
Platt, J. P., Kelley, S. P., Carter, A. & Orozco, M., 2005. Timingof tectonic events in the Alpujarride Complex, Betic Cordil-lera, S. Spain. Journal of the Geological Society London, 162,1–12.
Poisson, A. M., Morel, J. L., Andrieux, J., Coulon, M., Wernli,R. & Guernet, C., 1999. The origin and development ofNeogene basins in the SE Betic Cordillera (SE Spain): A casestudy of the Tabernas-Sorbas and Huercal-Overa basins.Journal of Petroleum Geology, 22, 97–114.
Powell, R. & Holland, T. J. B., 1988. An internally consistentdataset with uncertainties and correlations: three applicationsto geobarometry, worked examples and a computer program.Journal of Metamorphic Geology, 6, 173–204.
Puga, E. &Dıaz de Federico, A., 1976.Metamorfismo polifasico ydeformaciones alpinas en el Complejo de Sierra Nevada(Cordillera Betica). Implicaciones geodinamicas. In: Reunionsobre laGeodinamica de las Cordilleras Beticas yMar deAlboran(ed. ????, ?.), pp. 79–114, Special Publication, Granada.34
Puga, E., Nieto, J. M. & Dıaz de Federico, A., 2000a35 . Con-trasting P–T paths in eclogites of the Betic ophiolitic associ-ation, Mulhacen Complex, South-eastern Spain. CanadianMineralogist, 38, 1137–1161.
Puga, E., Dıaz de Federico, A. & Nieto, J. M., 2000b36 . Tecto-nostratigraphic subdvision and petrological characterisationof the deepest cpmplexes of the Betic zone: a review. Geodi-namica Acta, 15, 23–43.
Ring, U., Brandon, M.T., Willett, S.D. & Lister, G.S., 1999.Exhumation processes. In: Exhumation Processes: NormalFaulting, Ductile Flow and Erosion (eds Ring, U., Brandon, M.T., Willett, S. D. & Lister, G.S.), pp. 1–27. Geological SocietySpecial Publication, London.
Royden, L. H., 1993. The tectonic expression of slab pull atcontinental convergent boundaries. Tectonics, 12, 303–325.
Samson, S. D. & Alexander, E. C., 1987. Calibration of theinterlaboratory 40Ar/39Ar dating standard, Mnhb-1. In: NewDevelopments and Applications in Isotope Geoscience (ed. ?????,?.), pp. 27–34. Chemical Geology (Isot. Geosci. Sect.).37
Sanchez Rodrıguez, L. & Gebauer, D., 2000. Mesozoic forma-tion of pyroxenites and gabbros in the Ronda area (SouthernSpain), followed by early Miocene subduction metamorphismand emplacement into the Middle crust – U-Pb sensitive high-resolution ion microprobe dating of zircon. Tectonophysics,316, 19–44.
Scaillet, S., 1998. K-Ar�(40Ar/39Ar) geochronology of ultrahighpressure rocks. In: When Continents Collide: Geodynamics andGeochemistry of Ultrahigh-pressure Rocks (eds Hacker, B.R. &Liou, J. G.), pp. 161–201. Kluwer, ?????.38
Scaillet, S., Feraud, G., Ballevre, M. & Amouric, M., 1992. Mg/Fe and (Mg, Fe)Si-Al2 compositional control on argonbehaviour in high-pressure white micas: a 40Ar/39Ar con-tinuous laser-probe study from the Dora-Maira nappe of theinternal western Alps, Italy. Geochimica and CosmochimicaActa, 56, 2851–2872.
Schaeffer, O. A., Muller, H. W. & Grove, T. V., 1977. Laser Ar/Ar study of Apollo 17 basalts. Geochimica and CosmochimicaActa, 8, 1489–1499.
Selverstone, J., Axen, G.J. & Bartley, J.M., 1995. Fluid inclusionconstraints on the kinematics of the footwall uplift beneath theBrenner Line normal fault, Eastern Alps. Tectonics, 14, 264–278. doi:10.1029/94TC03085.
Soto, J. I. & Munoz, M., 1993. Presencia de mineralogıas ricasen Zn como evidencias de actividad hidrotermal en zonas decizalla extensionales. Geogaceta, 14, 146–149.39
Spakman, W. & Wortel, R., 2004. A tomographic view onWestern Mediterranean geodynamics. In: The TRANSMEDAtlas – The Mediterranean Region from Crust to Mantle (edsCavazza, W., Roure, F. M., Spakman, W., Stampfli, G. M. &Ziegler, P. A.), Springer, Berlin, Heidelberg.40
Spear, F. S., Selverstone, J., Hickmott, D., Cowley, P. & Hod-ges, K. V., 1984. P–T paths from garnet zoning: A new tech-nique for deciphering tectonic processes in crystalline terranes.Geology, 12, 87–90.
Spear, F. S., Hickmott, D. D. & Selverstone, J., 1990. Meta-morphic consequences of thrust emplacement, Fall Mountain,New Hampshire. Geological Society of America-Bulletin, 102,1344–1360.
Tendero, J. A., Martın-Algarra, A., Puga, E. & Dıaz de Feder-ico, A., 1993. Lithostratigraphie des metasediments del’association ophiolitique Nevado-Filabride (SE Espagne) etmise en evidence d’objets ankeritiques evoquant des forami-niferes planctoniques du Cretace: consequences paleogeo-graphiques. Comptes Rendus de l’Academie des Sciences deParis, 316 (serie II), 1115–1122.
Trotet, F., Vidal, O. & Jolivet, L., 2001. Exhumation of Syrosand Sifnos metamorphic rocks (Cyclades, Greece). New con-straints on the P–T paths. European Journal of Mineralogy, 13,901–920.
Vanderhaeghe, O., 2004. Structural development of the Naxosmigmatite dome. In: Gneiss Domes in Orogeny (eds Whitney,D., Teyssier, C. & Siddoway, C. S.), pp. 391. Special Paper,The Geological Society of America, ?????????.
Velde, B., 1967. Si4+ content of natural phengites. Contributionsto Mineralogy and Petrology, 14, 250–258.
Vidal, O. & Parra, T., 2000a41 . Exhumation paths of high pressuremetapelites obtained from local equilibria for chlorite-phen-gite assemblages. Geological Journal, 35, 139–161.
Vidal, O. & Parra, T., 2000b42 . Exhumation paths of high pressuremetapelites obtained from local equilibria for chlorite-phen-gite assemblages. Geological Journal, 35, 139–161.
Vidal, O., Goffe, B. & Theye, T., 1992. Experimental study of anew petrogenetic grid for the system FeO-MgO-Al2O3-SiO2-H2O. Journal of Metamorphic Geology, 14, 381–386.
Vidal, O., Theye, T. & Chopin, C., 1994. Experimental study ofchloritoid stability at high pressure and various fO2 condi-tions. Contribution to Mineralogy and Petrology, 118, 256–270.
Vidal, O., Goffe, B., Bousquet, R. & Parra, T., 1999. Calibrationand testing of an empirical chloritoid-chlorite thermometerand thermodynamic data for daphnite. Journal of Meta-morphic Geology, 10, 603–614.
Vidal, O., Parra, T. & Trotet, F., 2001. A thermodynamic modelfor Fe-Mg aluminous chlorite using data from phase equili-brium experiments and natural pelitic assemblages in the 100–600 �C, 1–25 kbar P–T range. American Journal of Sciences,301, 557–592.
Villa, I. M., 1998. Isotopic closure. Terra Nova, 10, 42–47.Vissers, R. L. M., 1981. A structural study of the central Sierrade los Filabres (Betic Zone, SE Spain) with emphasis ondeformational processes and their relation to the alpinemetamorphism. GUA Papers of Geology, 15, 1–154.
24 R . AUGIER ET AL .
� 2005 Blackwell Publishing Ltd
UNCORRECTEDPROOF
Vissers, R. L. M., Platt, J. P. & Van der Wal, D., 1995. Lateorogenic extension of the Betic Cordillera and the AlboranDomain: A lithospheric view. Tectonics, 14, 786–803.
Volk, H.R., 1967. Relations between Neogene sedimentationand late orogenic movements in the Eastern Betic Cordilleras(SE Spain). Geologie en Mijnbouw, 46, 471–474.
Weijermars, R., Roep, T. B., Van den Eeckhout, B., Postma, G.& Kleverlaan, K., 1985. Uplift history of a Betic fold nappeinferred from Neogene-Quaternary sedimentation and tec-tonics (in the Sierra Alhamilla and Almerıa, Sorbas andTabernas Basins of the Betic Cordilleras, SE Spain). Geologieen Mijnbouw, 64, 397–411.
Wernicke, B., 1992. Cenozoic extensional tectonics of the U.S.In: Cordillera. The Cordilleran Orogen: Conterminous U.S. TheGeology of North America (eds Burchfiel, B. C., Lipman, P. W.& Zoback, M.L.), pp. 553–581. Geological Society of Amer-ica, Boulder, CO.
Yin, A., 1991, Mechanism for the formation of domal andbasinal detachment faults: A three-dimensional analysis.Journal of Geophysical Research, 96, 14577–14594.
Zeck, H. P., Albat, F., Hansen, B. T., Torres-Roldan, R. L.,Garcıa-Casco, A. & Martın-Algarra, A., 1989. A 21 ± 2 Maage for the termination of the ductile Alpine deformation inthe internal zone of the Betic Cordilleras, South Spain.Tectonophysics, 169, 215–220.
Zeck, H. P., Monie, P., Villa, I. M. & Hansen, B. T., 1992. Veryhigh rates of cooling and uplift in the Alpine belt of the BeticCordilleras, southern Spain. Geology, 20, 79–82.
Zeck, H. P., Kristensen, A. B. & Williams, I. S., 1998. Post-collisional volcanism in a sinking Slab setting – crustalanatectic origin of pyroxene-andesite magma, Caldear volca-nic group, Neogene Alboran volcanic province, South-easternSpain. Lithos, 45, 499–522.
Zeck, H. P., Argles, T. W. & Platt, J. P., 2000. Discussion onAttenuation and Excision of a Crustal section during exten-sional exhumation, Carratraca peridotites, Betic Cordilleras,Southern Spain. Journal of the Geological Society, 157, 253–255.
Received 01 February 2004; revision accepted 26 April 2005.
EXHUMAT ION, DOMING AND SLAB RETREAT 25
� 2005 Blackwell Publishing Ltd
Author Query Form
Journal: JMG
Article: 581
Dear Author,
During the copy-editing of your paper, the following queries arose. Please respond to these by marking up
your proofs with the necessary changes/additions. Please write your answers on the query sheet if there is
insufficient space on the page proofs. Please write clearly and follow the conventions shown on the attached
corrections sheet. If returning the proof by fax do not write too close to the paper’s edge. Please remember
that illegible mark-ups may delay publication.
Many thanks for your assistance.
Query
reference
Query Remarks
1 Au: Please provide e-mail ID for the corresponding author
2 Au: Lonnergan & White, 1997 has been changed to Lonergan & White,
1997 so that this citation matches the list
3 Au: Gomez-Pugnaire & Fernandez-Soler, 1987 has been changed to Gomez-
Pugnaire & Soler, 1987, in this citation and the subsequent ones, so that the
citations match the list
4 Au: Monie et al., 1991 has been changed to Monie & Chopin, 1991, in
this citation and the subsequent ones, so that the citations match the list
5 Au: Johnson et al., 1997 has not been included in the list, please supply
publication details.
6 Au: Puga et al., 2002 has not been included in the list, please supply
publication details.
7 Au: Egeler & Simon, 1969 has not been included in the list, please supply
publication details.
8 Au: Garcıa-Duenas et al., 1988 has been changed to Garcıa-Duenas et al.,
1988b so that this citation matches the list
9 Au: Martınez & Azanon, 1997 has been changed to Martınez-Martınez &
Azanon, 1997 so that this citation matches the list
10 Au: Tagami & Shimada, 1996 has not been included in the list, please
supply publication details.
11 Au: Please check: �was completed�
12 Au: Puga, 1976 has been changed to Puga & Dıaz de Federico, 1976 so that
this citation matches the list
13 Au: Please define: PAP.
14 Au: Please check this website address and confirm that it is correct.
15 Au: Krischner et al., 1996 has been changed to Kirschner et al., 1996 so
that this citation matches the list
16 Au: Sanchez-Viscaino et al. (2001) has been changed to Lopez Sanchez-
Vizcaıno et al. (2001) so that this citation matches the list
