Evidence for Archean crust in Iran provided by ca 2.7 Ga zircon xenocrysts within amphibolites from the Sanandaj-Sirjan zone, Zagros orogen

摘要: Abstract High-precision secondary-ion mass spectrometry (SIMS) U–Pb and Hf–O isotopic microanalyses of zircons from the central Sanandaj–Sirjan metamorphic zone (SSMZ) Zagros orogen, Iran, provide evidence presence 2.7 Ga xenocrystic zircons, suggesting that SSMZ records Neoarchean crustal components have not previously been reported in Iran. The two amphibolite samples analyzed Muteh–Golpaygan complex during this study include one sample (GQ-10) yielded with ages clustered around ca 2.7 Ga. second (GC-15) contains show distinct zircon domains (i) 2.7 2.5 Ga, (ii) 52 Ma. homogeneous, mantle-like δ18O values a mean 6.10 ± 0.69‰. They eHf(t) vary between +0.2 to +6.8 TDMC 3.1–2.7 Ga, they crystallized granitoid melts derived juvenile components. However, younger 2.5 Ga yield an average value 6.17 ± 0.24‰ evolved Hf compositions (eHf(t) −0.8 −3.4; TDMC = 3.2–3.1 Ga), indicating older crust region underwent more intense later reworking than is case for material formed at These data basement rocks region, ancient growth events. youngest 52 Ma within these most likely reflect late Paleocene–Eocene magmatic ‘flare-up’ slightly elevated (7.69 ± 0.21‰) negative −8.3 −12.1; TDMC = 1.9–1.6 Ga), intensive 50 Ma.