The Internal Zone of the Betic Cordilleras consists of several superimposed major thrust sheets with different P-T-t evolutions. On the basis of an integrated field, miCroscopic and laboratory study, the tectono-metamorphic history of the Mulhacen Complex and Almanzora Unit has been reconstructed in detail. The Mulhacen Complex has been af€ected by at least five phases of penetrative deformation, which have been labelled Dx-,, D. , DX+,, D,,, and DX++ D,-, and D, are related to continent-continent collision, which is indicated by high pressure-low temperature (WILT) and subsequent intermediate PIT metamorphic conditions. D,,, is related to crustal thinning and heterogeneous extension. During this event the ALmanzora Unit was juxtaposed against the Mulhacen Complex. This phase was succeeded by the establishment of low pressure-high temperature (LPIHT) conditions and at least two phases of folding and overthrusting. The Almanzora Unit shows a comparable tectono-metamorphic evolution p t D,,,. However, the P I T conditions prior to D.,, indicate a higher crustal position with respect to the Mulhacen Complex during the collisional event.

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On Kaibobo (W Seram), obduction of hot oceanic lithosphere produced high-grade metamorphism and granite in overthrust continental crust. 4°Ar/39Ar plateau ages of 5.65-6.0 Ma and 5.4 Ma of muscovite and biotite from the sole, among the youngest so far measured on single crystals, indicate complete resetting of the Ar-isotope system. Chloritized biotite crystals gave disturbed spectra and younger ages. Single fusion on biotite from the granite gave an age of 5.5 Ma. Time limits for the obduction-exhumation history of the Kaibobo complex and sole are approximated by simple 1D forward P-T-t modelling, constrained by PT data and 4°Ar/39Ar thermochronology (c. 400°C at 6 Ma; c. 320°C at 5.5 Ma). Best fit results indicate that the decelerating post-emplacement exhumation of ophiolite and sole began < 8 Ma ago. The rate during the first 1 Ma of this uplift exceeded 7.5 mm a -1. Undoing 8 Ma of migration in the SW Pacific and Australian regimes of motion back-tracks Kaibobo to the site where obductionemplacement ended: near the southeastern corner of the Banda Sea plate. Similar compositions and time-settings of the Kaibobo and N Timor ophiolites lead us to postulate that, during the Early Miocene, slow-rate spreading occurred in the oceanic lithosphere of the southern Banda Sea, south of the current volcanic arc. Rangin et al. 1990). The E-W elongated island of