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
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• 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
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