Analytical Methods and Results

Thermobarometry
	Mineral chemistry data (Table 3) were obtained on 30µm polished sections, using the Microscan Electron Microprobe at Oxford at an accelerating potential of 20kV, beam current 4x10-8A, and beam size of 0.5-1.0µm (Argles et al 1999), supplemented by data obtained on the Cameca SX100 Electron Microprobe at the Open University, U.K (20kV accelerating potential, 20nA beam current, 10µm diameter fixed electron beam).  
	Line profiles of the largest garnets in each section were routinely acquired to determine zonation patterns, with X-ray maps generated on the Open University microprobe for key samples.  Where appropriate, inclusions of phases in garnet were also analysed.  Line profiles of other porphyroblast phases served mainly to verify the general absence of zoning in minerals other than garnet.  Means were taken for different petrographic populations of each phase – generally from 10 analyses or more – and the individual analysis closest to the mean was employed for thermobarometry.  Garnet analyses were selected on the basis of both stoichiometry and location (i.e. extreme rim, inner rim, plateau or core) from several line transects across the largest grains.  New estimates for this study were calculated using the individual thermometer and barometer calibrations listed in Table 1, matching the results by iteration on a spreadsheet.  Errors quoted assume a propagated 1% uncertainty on microprobe analyses and incorporate specific experimental or activity model uncertainties associated with each calibration.  Individual thermometers and barometers were used to exploit the highly domainal nature of sample C234 most effectively, in contrast to Argles et al. (1999), who also employed Thermocalc (Powell & Holland 1988) in both average PT and phase diagram mode to obtain thermobarometric estimates.

Ar-Ar analyses
	Slices of rock samples around 1 cm square were thinned to around 150 µm, polished on one side and prepared for irradiation by washing ultrasonically in methanol and de–ionised water.  Cleaned samples were packed in aluminium foil and irradiated at the McMaster Reactor, Toronto, Canada.  Upon return slices were loaded into a laser port with a fused silica window, pumped down to ultrahigh vacuum and heated to remove surface absorbed atmospheric argon.  Laser spots were fused with a focused beam from a Nd‑YAG laser running at the fundamental wavelength of 1064 nm, using techniques described in Kelley (1995). Gases released by laser melting were absorbed and reacted with hot Zr-Al alloy getters (SAES NP10) for a minimum of 5 minutes to remove all active gases.  The remaining noble gases (mainly argon) were equilibrated into an MAP215‑50 noble gas mass spectrometer with a Johnston multiplier.  All argon peaks were scanned 10 times and peak heights extrapolated back to the inlet time to allow for argon build-up and memory effects The data, which are presented in Table 5, were corrected for mass spectrometer discrimination and irradiation interference reactions.  Ages calculated were based upon analyses of GA1550 biotite standard (Renne et al. 1998).  In some cases, atmospheric contents were variable and allowed an isochron to be defined though in other cases, the spread in atmospheric contents did not allow an isochron to be defined.  In cases where excess argon is present, the variation in ages was very large though an isochron and initial ratio could be defined using the ISOPLOT/Ex programme of Ludwig (1999).  In cases where no evidence for excess argon could be discerned, we have used a weighted mean for consistency, since samples yielding little scatter defined poor isochrons and yet the individual ages were tightly clustered.  The weighting on the mean is defined using the inverse of variance but the final error is magnified by the scatter of data about the mean using the students ‘t’ value, multiplied by the square root of MSWD as defined by Ludwig (1999).
	Most of the samples from the Caratracca area yielded either an isochron which intercepted the 36Ar/40Ar axis within errors of the atmospheric ratio, or were too tighly clustered close to the 39Ar/40Ar axis to yield an isochron.  In several cases lines fitted to the data had spurious slopes despite the data yielding closely clustered individual laser spot ages (Fig. 14).  As stated above, we  adopted a pragmatic approach which allowed us to apply the same ISOPLOT weighted mean age technique to all samples, incorporating errors caused by scatter in the data without assuming an atmospheric ratio.  In the final modelling we used a weighted mean of three biotite samples (PB 378, PB379 and PB381) to achieve a representative age for these closely spaced samples.  In only one sample (PB382 amphibole) did we detect excess argon using the isochron technique indicating an extreme end member excess composition (40Ar/36Ar = 1430) and thus we used the isochron age.
	It is difficult to compare Ar-Ar ages from Montes de Malaga and Caratracca since the single sample from Montes de Malaga (an andalusite schist ) yielded a poorly defined age of 18.6±1.8 Ma (95% confidence level).  The high and variable atmospheric contents of this sample probably indicate contamination of analyses by chlorite and K-feldspar, but there is no indication of older ages that might have resulted from a strong detrital signature despite the low peak metamorphic temperature. 

Fission-track analyses
	Apatite and zircon samples for fission track analysis were mounted, polished and etched using KOH:NaOH eutectic at 225°C between 24 and 48 hours (zircon), and  5M HNO3 at 20±1°C for 20±1 seconds (apatite). Etched mounts were irradiated with muscovite external detectors and Corning dosimeter glasses CN-2 (zircon) and CN-5 (apatite) at the DR 3 thermal neutron facility of the Risø reactor, Denmark, (Cd/Au ratio >400).  Fission-track densities and track length measurements were made using an optical microscope at 1250x magnification (an oil objective was used for zircon analyses).  Ages (±1) were calibrated using the zeta method (Hurford and Green, 1983) determined by multiple analyses of age standards following the recommendations of Hurford (1990); analyst Carter cn2127 ± 5 (zircon) and cn5 339±5 (apatite), *Johnson cn5 361±6 (apatite). Data are reported as central ages which weights modal ages for different precisions of individual crystals (Galbraith and Laslett, 1993). Where appropriate apatite FT data were modelled to reconstruct cooling paths using the approach of Gallagher (1995) and model of Laslett and Galbraith (1996). 
	Zircon FT samples from the Caratracca sequence yielded ages (Table 6a) within error of 21 Ma. The one exception (CAR 11, central age 280±19 Ma) came from a greywacke in the surrounding non metamorphic sequence. Whilst most apatite ages are within error of 21 Ma some samples are slightly younger (youngest CAR19, 14.9±1.1Ma) reflecting minor local variation in post-exhumation erosion (the younger apatite ages tend to be found in topographically low areas). Fission track mean track length (MTL) data is of variable quality due to the limited numbers of length measurements caused by low spontaneous track densities. The more reliable data (> 40-50 measurements) are 14-15µm tracks consistent with very rapid  (< 1 Myr) cooling through the fission track partial annealing zone to temperatures ≤ ~ 60°C. Samples such as these with unannealed long MTL’s do not require modelling to constrain their cooling paths. 
	Fission track data from the Montes de Malaga area (Fig. 6b) show a similar age distribution to samples from Caratracca but a key difference is that more have Palaeozic to Mesozoic central ages, in both apatite and zircon. Data quality is generally good and higher spontaneous track densities have resulted in reasonable numbers of track length measurements for most apatite samples. The data show a correlation with their lithostratigraphic position within  the Malaguide Complex. The lowermost unit comprising graphitic phyllites and quartzites have zircon ages around 21 Ma and a single apatite age of 13.4±1.1Ma (MM3). The MTL data for the apatite sample is long (14.33±0.12µm) diagnostic of rapid cooling. Middle unit samples comprising Palaeozoic clastic and calcareous sediments show a mixture of zircon central ages ranging from 355±25 Ma (MM22) down to 170±10 Ma (MM15). Age dispersion indicators (table 6) show mixed populations of single grain ages which range between 450 Ma to ~100 Ma, i.e. older and younger than the depositional age. Such grain age distributions are indicative of partial resetting by heating to between 200-300°C. The apatite data for these samples record total resetting at or close to 21 Ma. One exception, sample MM22, has a Jurassic FT central age (150±18 Ma) showing that for some areas thermal resetting involved much lower temperatures (<100°C). The uppermost unit comprising continental clastics of probable Permo-Triassic age, were only dated using apatite. One sample (MM11) gave a central age of 20.9±1.9 Ma whilst the rest were between 185±12 Ma (MM20) and 269±11 Ma (MM10).  For the youngest age a long MTL indicates rapid cooling to temperatures < 60°C, whilst the older samples have short MTL’s, between 9.70±0.26µm (MM20) and 12.34±0.18µm (MM10). Qualitatively such short MTL’s suggest recent cooling from temperatures within the apatite FT partial annealing zone (typically between 60-110°C) and this is confirmed by modelling which shows protracted (Mesozoic to Tertiary) residence at moderately low temperatures between 60-90°C prior to rapid cooling during the middle to late Tertiary. Although timing is not well defined this rapid cooling would appear to overlap with the 21 Ma exhumation event recorded in the bulk of the FT data from the Carratracca and Malaga area.

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