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High Pressure Klippe on the Active Western Margin of Pangea during Initial Stages of Amalgamation

This study investigates the Acatlán Complex at Tehuitzingo, Puebla State, southern México to understand the high-pressure metamorphism and deformation processes during the early stages of Pangea amalgamation. The research includes field relations, petrology, geochronology, geothermobarometry, and tectonic analysis. The findings provide insights into the geodynamic environment and exhumation rates of the complex.

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High Pressure Klippe on the Active Western Margin of Pangea during Initial Stages of Amalgamation

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  1. HIGH PRESSURE KLIPPE ON THE ACTIVE WESTERN MARGIN OF PANGEADURING INITIAL STAGES OF AMALGAMATION Gonzalo Galaz-Escanilla, J. Duncan Keppie, J. Brendan Murphy, James K.W. Lee, Amabel Ortega-Rivera Financing projects- PAPIIT N° IN100108-3 (Méx.), - CONACYT N° CB-2005-1:24894 (Méx.) - IGCP 597 (Unesco) Acatlán Complex at Tehuitzingo, Puebla State, southern México 1

  2. Study area Modified from Solari et al.,1998 ~250 Km tothesoutheast of México City Acatlán Complex at Tehuitzingo, Puebla State, southern México

  3. Study area Acatlán Complex geological map Authors HP metamorphismage Ordovician Ortega-Gutiérrez et al., (1999) Mississippian Keppie et al., (2008) Ordovician, Silurian and Carboniferous Vega-Granillo et al., (2009) Acatlán Complex at Tehuitzingo, Puebla State, southern México

  4. Background Different geodynamic models (0) Ortega-Gutiérrez et al., 1999 Acatlán Complex at Tehuitzingo, Puebla State, southern México

  5. Field relations 1:50,000 geological map Acatlán Complex at Tehuitzingo, Puebla State, southern México

  6. Field relations 1:50,000 geological map Acatlán Complex at Tehuitzingo, Puebla State, southern México

  7. Petrology Thin sections • HP Mica schist • Grt+Rt+Am+Zoi+Ab+Phe+Ep+Chl+Clc.Ttn • Grt + Rut • Amp + Zo • Chl + Ep + Ttn + Ab + Qz (greenschist) • HP Metabasite • Grt+Rt+Am+Zoi+Ab+Phe+Ep+Chl+Clc • Grt + Rut • Amp + Zo • Chl + Ep + Fps + Ms + Qz (greenschist) HP Serpentinite Atg+Lz+Ctl+Mag+Cal+Tlc Threemetamorphicevents (González-Mancera, 2001) • HP Granitoid • Qz+Fsp+Ms+Chl+Grt+Rt; Acc: Ep+Tit+Zrn+Op • Grt + Rut • Chl + Ep + Fps + Ms + Qz (greenschist) Low-grade Unit Qz+Fsp+Ms+Chl+Cld. Acc: Ep+Cal+Zrn+Op Acatlán Complex at Tehuitzingo, Puebla State, southern México

  8. Structure Low-grade unit deformation Threedeformationphases. Secondfoliation ~NE-SW whitdipvariations Foldinggenered axial planefoliation Secondfoldingisclass 1C and 2 Type 3 interferencepattern (Ramsay and Huber, 1987) affectedbygentlelater F3folds Acatlán Complex at Tehuitzingo, Puebla State, southern México

  9. Structure HP Unit deformation Threedeformationphases. Secondfoliations ~NS withdipvariations Othersecondfoliation NE-SW Secondfoldingisclass 1C and 2 Type 3 interferencepattern (Ramsay and Huber, 1987) affectedbygentlelater F3folds Acatlán Complex at Tehuitzingo, Puebla State, southern México

  10. Geochronology U-Pb results Acatlán Complexgranitoids: Deformedgranitoids Esperanza Suite: 480-440 Ma (severalauthors) Undeformedgranitoids La Noria: 483-451 Ma (Miller et al., 2007) Los Hornos: ~442 Ma (Miller et al., 2007) Palo Liso: 463-459 Ma (Miller et al., 2007) 900-750 Ma, unique source in the Goiás Magmatic Arc at Amazonia (Keppie et al., 2008) Acatlán Complexsedimentaryunits: Low-grade Las Minas: ~470 Ma (Ramos-Arias, 2007) 531-471 Ma (Keppie et al., 2008) Ojos de Agua: 491-441 Ma (Keppie et al., 2008) Huerta: ~464 Ma (cuttingpegmatite; Morales-Gámez et al., 2008) ~455 Ma (Keppie et al., 2006) High-grade Chicomalá: ~482 Ma (Ramos-Arias, 2011) Acatlán Complex at Tehuitzingo, Puebla State, southern México

  11. Geochronology Muscovite Ar-Ar cooling ages Coolingeventbetween 330-315 Ma MISSISSIPPIAN!! Acatlán Complex at Tehuitzingo, Puebla State, southern México

  12. Geothermobarometry P-T-t conditions HP rocks Threemetamorphic facies at HP UNIT PEAK (eclogite facies) GM geothermometer (Wu and Zhao, 2006) Zr in Rut geothermometer(Zack et al., 2004) Si in phengite barometer (AccordingtoMassonne et al., 2007) Firstretrogression (amphibolite facies) Am/Plg thermometer (Holland and Blundy, 1994) Al in amphibole barometer (Hollister et al., 1987; Schmidt, 1992) Si in phengite barometer (AccordingtoMassonne et al., 2007) Secondretrogression (greenschist facies) Al4 in chloriteCathelineau (1988) Si in phengite barometer (AccordingtoMassonne et al., 2007) ~750 °C and ~16 kbar ~472 °C and 3.4-7.1 kbar 356 ± 33 °C forlow-grade unit ~370 °C for HP unit ~2.7 kbar Acatlán Complex at Tehuitzingo, Puebla State, southern México

  13. Tectonic Acatlán Complex exhumation rates Mimilulcobasedon data from Meza-Figueroa et al. (2003) combinedwithagesfrom Elías Herrera et al. (2007) Esperanza Suite basedon data from Talavera-Mendoza et al. (2005) Cuatlaxtecomabasedon data from Ramos-Arias et al. (2011) Acatlán Complex at Tehuitzingo, Puebla State, southern México

  14. Tectonic Geodynamic environment Basedon more than 60 HP-UHP outcrops (e. g. Guillot et al., 2009; Chemenda et al., 2001) Continental collisionAccretionaryprismSerpentinitic subduction channelTehuitzingo HP rocks Exhumationrate: Up to 40 mm/year 1-5 mm/year 1-10 mm/year 0.3-1.0 mm/year Up to ~40 km (e.g. Glodny et al., 2005; Hyndman, 1995) Deph: Up to ~200 km Up to ~100 km ~54 km Clastic sedimentary rocks without mantle-derived material, suggesting that the protoliths of HP-LT rocks are sediments deposited on the sea floor The protoliths of UHP rocks are predominantly upper continental crust (granite gneisses, and metasedimentary rocks) Serpentinite matrix is associated with HP-LT gabbros lenses, considered as fragments of oceanic lithosphere, the contacts are interpreted to be primary (e.g., Coleman, 1971). Serpentinite matrix is associated with HP-LT gabbros lenses, considered as fragments of IAT (Galaz et al., 2009) Petrology features: gabbro and peridotite suggests that these rocks were present in the continent-ocean transition where the lower crust is thin or totally absent. metagabbroscontainminorultramaficcumulates metagabbroscontainminorultramaficcumulates(Messiga et al., 1999). Serpentinite subduction channel !!! Acatlán Complex at Tehuitzingo, Puebla State, southern México

  15. Paleo-reconstructions Discussion Acatlán Complex at Tehuitzingo, Puebla State, southern México

  16. a great geologist, person and coach… a spectacular panoramic view of the Mixteca Hills, México… Duncan in action Thanks Duncan!

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