Breakout session 1: Global tectonic setting of arc-continent collisions

1. Penrose Conference, "Neotectonics of Arc-Continent Collision" Manizales, Colombia 21 January 2011 Breakout session 1: Global tectonic setting of arc-continent collisions Ron Harris, BYU Utah Marc-André Gutscher, Brest France

2. Arc-continent collisions around the world Active collisions: - Colombia: N. Andes margin w. Choco Block - Taiwan: China margin w. Luzon arc - Timor: Australia margin w. Banda arc - Honshu: Japan margin w. Izu-Bonin arc - Kamchatka: Siberian margin w. Aleutian arc Recent collisions: - W Medit.: Maghreb margin w. Kabylies arc - S Caribbean: N margin of S. America w. paleo-Antilles arc

3. Arc-Continent Collisional Processes • Partitioning of strain away from the initial trench • Subduction accretion and Metamorphism of lower plate material • Arc contamination or modification by slab melts or tears • Emplacement and uplift of forearcslabs • Flattening of slab dip and increased coupling • Crustal shortening and topography (island emergence or orogenic plateau) • Forearc closure or narrowing • Synorogenic basin development and reversal of sedimentation • Arc accretion (New Guinea) • Arc demise( • Indentation of arc and continent and block translation and rotation • Plate boundary reorganization ( • Subduction polarity reversal • new subduction zone on backside of indentor • Lateral propagation of trench by subduction zone rollback • Slab tear off (Mediterranean) • Syn-collisional gravitational collapse

4. Tectonic Evolution of Colombia region • 75 Ma Collision of Plateau with arc on eastern edge with continental arc on western SA • Sula Sea type subduction system • Accretion of oceanic plateau somehow and development of eastward subduction system • Northward translation and rotation of accreted fragments • 50-30 Ma NW subduction of Farallon Plate under Panama Arc and ss motion along Columbian margin • Connection of this arc with the colombianmargin is poorly defined • 30 Ma uplift of central cordillera • 24 Ma age collision of Panama Arc with margin (chemistry changes and at 10 Ma arc demise) • By 10 Ma accretion of Panama arc by sliding along oblique subduction continental arc • Collision causes Panama arc to bend CW, subduction on south side stops and new subduction starts on northside • 8 Ma to present Panama block is translated north without arc volcanism • Synorogenicsedimentation documents shortening of western Cord. • No volcanism along northern margin of SA • SA plate westward motion vs. Panama collision is simultaneous and is difficult to parse out relative contribution of each • Plate reorganization at 10 Ma may be cause of uplift • Cause of indentation is flat slab subduction of buoyant lithosphere or Panama arc indentation after it bends to maximum tightness • Carnegie ridge indentation causes northward translation • At 3 Ma panama closes • Panama is passive and bent by movement of SA plate • How much of flat slab is from west and north?

6. Global Arc-Continent Collision • Banda • Taiwan, • Panama, S. Caribbean (Throughout Cenozoic) • NW Pacific (Japan and Kamchatka) • Mediterranean • Papua New Guinea (new Britian arc) • Eastern Indonesia • Yakutat - Aleutians

7. Upper plate arc Intra-oceanic Arc-passive continental margin • Intra-oceanic Arc-bathymetric high (plateau, seamount) • Intra-oceanic arc- intra-oceanic arc • Plateau – continentalarc

8. Banda Arc – initiation of uplift and accretion Collision of continental shelf Present 1.9 Ma 3.7 Ma 5.5 Ma Banda Arc – initiation of backarc thrust Sumba-collision of Scott Plateau • Banda Arc – contamination by continental crust • Timor • Emergence to sea level • Banda Arc – Subduction volc. • Timor • Deep accretionary ridge • Metamorphism of distal continent margin

9. Mediterranean Region • Closure of Tethyan collides north African margin with Med arcs • Backarc basin development from slab rollback • Drives Lateral block migration • K-rich calc-alkaline rocks above where slab windows open up on east and west edges of slab