Geochronological & Geochemical Constraints from IRAN on the magmatic evolution related to Neotethyan subduction and Zagros orogeny A GEOLOGICAL Silk Road Project: 01/08/2011-31/07/2016 Comparative Study of the Tibet/Himalaya vs. Caucasus/Iran Orogens CAUSE CREATE • Outstanding Q: How cont-cont collisional orogeny evolves? New Impossibilities • Major product of the Neotethyan subduction: the Urumieh Dokhtar Magmatic Arc (UDMA) 5 Stampfli & Borel (2004) ~84 Ma 6 7 Literature age data on Magmatism UDMA: Urumieh- Dokhtar Magmatic Arc SSZ: Sanandaj- Sirjan Structural Zone Age distribution of magmatic rocks in Iran Eocene magmatic flare-ups! Agard et al. (2011) • Arabia-Eurasia convergence at 2-3 cm/yr since 56 Ma • slow, steady rate of Neotethyan n-ward subduction • contrasting with strongly variable rates of the arc magma production (~50-35 Ma “flare-ups”) • subduction rate vs. cont. arc magma production? The enigmatic mid-Tertiary arc volcanic pulse Vincent, Allen et al. (2005, Bull GSA) Arabia-Eurasia collision and the forcing of mid-Cenozoic global cooling Mark B. Allen & Howard A. Armstrong (2008) Eocene Eo-Oligocene magmatic rocks Oligocene Some “Outstanding” Questions: • A “double” magmatic arc? Or, an arc vs. its “backarc”? (semi-)continueous, long-lasting Neotethyan subduction? • Magmatic “flare-up” (only) in the Eocene? • The Neo-Tethyan subduction rate: change or not? • The onset timing of the Arabia-Eurasia collision? [diachronous? e.g., SE-ward younging?] • Slab breakoff: when? a starting “point”? propagating? • When and how the Turk-Iranian plateau was uplifted? • Comparable with the Tibet-Himalaya orogen? bThe time vs. space evolution of the pre- to post- magmatism in the Caucasus-Turk-Iran orogenic belt [esp. system./precise age dating + geochemistry] Iranian Magmatic Zircons (<600 Ma) Age results in the UDMA and SSZ Literature data from the SSZ: ca. 175-150 Ma & ca. 55-36 Ma UDMA: (1) northwest (2) central (3) southeast segments Northwestern UDMA: zircon U-Pb age results 53-27 Ma and <11 Ma (post-collisional magmatism) 08-IR-ZS-87: Abundant Inh.Zc at ~233 Ma <11 Ma Post-collisional magmatism Armenia: 4-3 Ma zircon U-Pb and <2 Ma whole-rock Ar-Ar ages (Lin, thesis, 2011) Sabalan: 0.4 Ma Kirovakan (Armenia) Sahand : 7-4 Ma 4.4 Ma adakite Saray: 11 Ma high-K basalts Saray (Urumieh) Sabalan 11 Ma 0.4 Ma basalt adakite Central UDMA: zircon U-Pb age results ~166 Ma (Shir-Kuh pluton) and 57-16 Ma 08-IR-ZS-30: Abundant Inh.Zc at ~278 Ma Southeastern UDMA: zircon U-Pb age results 81-72 Ma (granitoids) and 45-5.4 Ma Mesozoic Granitoids (Late Jurassic & Late Cretaceous) Mesozoic Granitoids (Late Jurassic & Late Cretaceous) Mesozoic Granitoids (Late Jurassic & Late Cretaceous) Eocene Oligocene Miocene Λ Major Remarks: • The magmatic “flare- ups”: “longer-lasting” in the Eocene-Oligocene (ca. 55-25 Ma) • Southeastward younging of magma termination: ~16 Ma in central UDMA ~5-6 Ma in southeast UDMA• Magmatic gaps? • Major age peaks in SSZ: ~165 Ma; ~55-36 Ma Λ Chiu (2012 thesis, in ) 26.5 Ma 21-16 Ma Southeastward 13-7 Ma termination of the precollisional, “arc” magmatism 35 16 mm/yr Iran 18 mm/yr 22 mm/yr Allen (2004) Post-collisional (mid-Miocene to Quaternary) Lut Sistan ophiolite Zarrinkoub et al. (in revision) ~110 Ma ~86-70 Ma ~56-54 Ma ~45-25 Ma ~45-25 Ma Zarrinkoub et al. (in prep.) 14.3-1.6 Ma 45 ? ? McCall (1997, JAES) 4646 ? ? 4747 McCall (1997) The geotectonic history of Makran Active (<1 Ma) Volcanoes In IRAN 48 5050 5151 Coexistence of 4 types of mid-Miocene magmatism in IRAN Absarokites (~11 Ma) Adakites (~6 Ma to date) Intraplate AB Postcollisional (~14-1.6 Ma) Extensional Calc-alk. lavas (~13-5.4 Ma) Neotethyan Calc-alk. lavas Subduction (~19-0.8 Ma) (ending) start of Makran Subduction?52 Slab breakoff Dilek (2009)5353 Al-Lazki et al. (2004, GJI) 1. Pn Velocity 2. Sn Attenuation 5454 Sistan ophiolite Thank You !.