The temporal evolution of subduction initiation in the Samail ophiolite: High‐precision U‐Pb zircon petrochronology of the metamorphic sole

High-precision dating of the metamorphic sole ophiolites can provide insight into tectonic evolution and subduction zone processes. To understand initiation beneath a young, well-preserved, well-characterized ophiolite, we performed coupled zircon laser-ablation inductively mass spectrometry (LA-ICP-MS) trace element analyses high-precision isotope dilution-thermal ionization (ID-TIMS) U-Pb on 25 samples from Samail ophiolite (Oman-United Arab Emirates). Zircon grains amphibolite- to granulite-facies (0.8–1.3 GPa, ~700–900°C), garnet- clinopyroxene-bearing amphibolite (n = 18) show systematic trends decreasing heavy rare earth slope (HREE; Yb/Dy) with Yb concentration, reflecting progressive depletion HREE during prograde garnet growth. For half garnet-clinopyroxene samples, Ti-in-zircon temperatures increase dates young slope, consistent growth metamorphism. In remaining there is no apparent variation in temperature combined geochemical data suggest crystallization along either peak or initial retrograde portions P-T-t path. The new bracket timing highest-grade rocks between 96.698 ± 0.094 95.161 0.064 Ma, contrast previously published geochronology suggesting metamorphism at ~104 Ma. Garnet-free amphibolites leucocratic pods lower-grade (but still upper-amphibolite facies) are uniformly enriched (Yb/Dy > 5), ~0.5–1.3 Myr younger than higher-grade same localities, constraining temporal offset juxtaposition higher- units. Positive εHf (+6.5 +14.6) for all but one dated an oceanic basalt protolith sole. Our indicate that (96.7–95.2 Ma) immediately predated overlapped overlying crust (96.1–95.2 Ma). ~600 ky onset northern portion versus start magmatism order magnitude shorter proposed (~8 Ma), spontaneous abbreviated period thrusting induced initiation. Taken together, preserve record first ~1.5 subduction. A gradient high-grade northwest (96.7 southeast (96.0–95.7 may propagation nascent and/or variations rate length ophiolite.